["Solar System Planetary system consisting of the Sun and objects orbiting it .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} For other uses, see Solar System (disambiguation) . <a href=\\\"./Wikipedia:Featured_articles*\\\" title=\\\"This is a featured article. Click here for more information.\\\" id=\\\"mwCA\\\"><img alt=\\\"Featured article\\\" resource=\\\"./File:Cscr-featured.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/20px-Cscr-featured.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"466\\\" data-file-height=\\\"443\\\" data-file-type=\\\"drawing\\\" height=\\\"19\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/40px-Cscr-featured.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\\n\"}' id=\"mwCg\"/> <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwDg\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwDw\\\"/></a></span>\"}' id=\"mwEA\"/> (true color, size to scale, distances not to scale)|style=padding:2px 0 4px 0;}}\"},\"age\":{\"wt\":\"4.568 billion years{{refn|group=lower-alpha|name=AgeSolarSystem}}\"},\"location\":{\"wt\":\"{{Longitem|{{unbulleted list\\n |{{nowrap|[[Local Interstellar Cloud]]}}\\n |[[Local Bubble]]<ref name=\\\"JPL interstellar\\\">{{cite web |url=http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html |title=Our Local Galactic Neighborhood | website= interstellar.jpl.nasa.gov |publisher=NASA |series=Interstellar Probe Project |year= 2000 |access-date=8 August 2012 |archive-url=https://web.archive.org/web/20131121061128/http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html |archive-date=21 November 2013 |url-status=dead }}</ref>\\n |[[Orion\u2013Cygnus Arm]]\\n |[[Milky Way]]<ref>{{Cite web |last=Hurt |first=R. |date=8 November 2017 |title=The Milky Way Galaxy |url=https://science.nasa.gov/resource/the-milky-way-galaxy/ |access-date=19 April 2024 |website=science.nasa.gov |language=en-US}}</ref>}}}}\"},\"neareststar\":{\"wt\":\"{{Longitem|{{Ublist\\n |[[Proxima Centauri]]\\n | (4.2465 [[Light-year|ly]])<ref name=\\\"lurie2014\\\" group=\\\"D\\\">{{cite journal |last1=Lurie |first1=John C. |last2=Henry |first2=Todd J. |last3=Jao |first3=Wei-Chun |last4=Quinn |first4=Samuel N. |last5=Winters |first5= Jennifer G. |last6=Ianna |first6=Philip A. |last7=Koerner |first7=David W. |last8= Riedel |first8=Adric R. |last9=Subasavage |first9=John P. | display-authors = 3| year= 2014 |title=The Solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry |journal=The Astronomical Journal |volume=148 |issue= 5 |pages=91 |arxiv=1407.4820 |bibcode= 2014AJ....148...91L |doi= 10.1088/0004-6256/148/5/91 |s2cid= 118492541 |issn = 0004-6256}}</ref>\\n |[[Alpha Centauri]]\\n | (4.36 ly)<ref name=\\\"RECONS\\\" group=\\\"D\\\">{{cite web|work= astro.gsu.edu| publisher= Research Consortium On Nearby Stars, Georgia State University|date=7 September 2007|title=The One Hundred Nearest Star Systems |url=http://www.astro.gsu.edu/RECONS/TOP100.posted.htm|access-date=2 December 2014|archive-url=https://web.archive.org/web/20071112173559/http://www.chara.gsu.edu/RECONS/TOP100.posted.htm|archive-date=12 November 2007| url-status=live}}</ref>}}}}\"},\"frostline\":{\"wt\":\"{{val|5|u=AU|p=~}}<ref name=\\\"Mumma\\\">{{Cite journal |last1=Mumma |first1=M. J. |last2=Disanti |first2=M. A. |last3=Dello Russo |first3=N. |last4=Magee-Sauer |first4=K. |last5=Gibb |first5=E. |last6=Novak |first6=R. |display-authors = 3| year= 2003 |title=Remote infrared observations of parent volatiles in comets: A window on the early solar system |journal=Advances in Space Research |volume=31 |issue=12 |pages=2563\u20132575 |bibcode= 2003AdSpR..31.2563M |citeseerx= 10.1.1.575.5091 |doi=10.1016/S0273-1177(03)00578-7}}</ref>\"},\"outerplanetname\":{\"wt\":\"[[Neptune]]\"},\"semimajoraxis\":{\"wt\":\"30.07 AU<ref name=Horizons group=\\\"D\\\">{{cite web |first=Donald K. |last=Yeomans |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%278%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272000-01-01%27&STOP_TIME=%272000-01-02%27&STEP_SIZE=%27200%20years%27&CENTER=%27@0%27&OUT_UNITS=%27AU-D%27 |title=HORIZONS Web-Interface for Neptune Barycenter (Major Body=8) |publisher=[[JPL Horizons On-Line Ephemeris System]] | website= jpl.nasa.gov|access-date=18 July 2014 |archive-date=7 September 2021 |archive-url=https://web.archive.org/web/20210907055935/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%278%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272000-01-01%27&STOP_TIME=%272000-01-02%27&STEP_SIZE=%27200%20years%27&CENTER=%27%400%27&OUT_UNITS=%27AU-D%27 |url-status=live }}{{snd}}Select \\\"Ephemeris Type: Orbital Elements\\\", \\\"Time Span: 2000-01-01 12:00 to 2000-01-02\\\". (\\\"Target Body: Neptune Barycenter\\\" and \\\"Center: Solar System Barycenter (@0)\\\".)</ref>\"},\"Kuiper_cliff\":{\"wt\":\"50\u201370 AU<ref name=\\\"twotino\\\">{{cite journal | first1= E. I.| last1= Chiang |title=Resonance Occupation in the Kuiper Belt: Case Examples of the 5:2 and Trojan Resonances |journal=[[The Astronomical Journal]] |volume=126 |issue=1 |pages=430\u2013443 |date=2003 |doi=10.1086/375207 |last2=Jordan |first2=A. B. |last3=Millis |first3=R. L. |last4=Buie |first4=M. W. |last5=Wasserman |first5=L. H. |last6=Elliot |first6=J. L. |last7=Kern |first7=S. D. |last8=Trilling |first8=D. E. |last9=Meech |first9=K. J. | display-authors = 3| bibcode= 2003AJ....126..430C |arxiv=astro-ph/0301458 |s2cid=54079935}}</ref><ref name= \\\"KuiperGap\\\">{{cite journal |first1=C. | last1=de la Fuente Marcos |first2=R. | last2= de la Fuente Marcos |title=Past the outer rim, into the unknown: structures beyond the Kuiper Cliff |journal=[[Monthly Notices of the Royal Astronomical Society Letters]] |volume=527 |issue=1 |pages= L110\u2013L114 |url=https://academic.oup.com/mnrasl/article-abstract/527/1/L110/7280408 |publication-date=20 September 2023 |date=January 2024 |access-date=28 September 2023 |bibcode=2024MNRAS.527L.110D |arxiv=2309.03885 |doi=10.1093/mnrasl/slad132 | doi-access=free |s2cid= |archive-date=28 October 2023 |archive-url=https://web.archive.org/web/20231028132004/https://academic.oup.com/mnrasl/article-abstract/527/1/L110/7280408 |url-status=live}}</ref>\"},\"heliopause\":{\"wt\":\"detected at 120 AU<ref name=\\\"heliopause\\\">{{cite web|url=http://www.nasa.gov/mission_pages/voyager/voyager20130912.html#.UjJLPZKR86s|title=NASA Spacecraft Embarks on Historic Journey Into Interstellar Space|first=Tony|last=Greicius| website= nasa.gov| date=5 May 2015|access-date=19 April 2024|archive-date=11 June 2020|archive-url=https://web.archive.org/web/20200611233345/https://www.nasa.gov/mission_pages/voyager/voyager20130912.html#.UjJLPZKR86s|url-status=dead}}</ref>\"},\"hillsphere\":{\"wt\":\"{{cvt|0.865|-|1.1|pc|AU ly pc|order=out|lk=out}}<ref>{{cite journal |last1=Souami |first1=D. |last2= Cresson |first2=J. |last3=Biernacki |first3=C. |last4=Pierret |first4=F. |title=On the local and global properties of gravitational spheres of influence |journal=[[Monthly Notices of the Royal Astronomical Society]] |date=21 August 2020 |volume= 496 |issue=4 |pages= 4287\u20134297 |doi= 10.1093/mnras/staa1520|doi-access=free | arxiv= 2005.13059 }}</ref><ref name=\\\"Chebotarev\\\">{{cite journal |last1=Chebotarev |first1=G. A. |title=Gravitational Spheres of the Major Planets, Moon and Sun |journal=Astronomicheskii Zhurnal |date=1 January 1963 |volume=40 |pages=812 |bibcode=1964SvA.....7..618C |url=https://adsabs.harvard.edu/full/1964SvA.....7..618C |issn=0004-6299 |access-date=6 May 2024 |archive-date=7 May 2024 |archive-url=https://web.archive.org/web/20240507030847/https://adsabs.harvard.edu/full/1964SvA.....7..618C |url-status=live }}</ref>\"},\"noknown_stars\":{\"wt\":\"yes\"},\"noknown_planets\":{\"wt\":\"yes\"},\"stars\":{\"wt\":\"[[Sun]]\"},\"planets\":{\"wt\":\"{{Longitem|{{Plainlist|*[[Mercury (planet)|Mercury]]\\n* [[Venus]]\\n* [[Earth]]\\n* [[Mars]]\\n* [[Jupiter]]\\n* [[Saturn]]\\n* [[Uranus]]\\n* [[Neptune]]}}}}\"},\"dwarfplanets\":{\"wt\":\"{{Longitem|{{Plainlist|\\n* {{Dp|Ceres}}\\n* {{Dp|Orcus}}\\n* [[Pluto]]\\n* [[Haumea]]\\n* {{Dp|Quaoar}}\\n* [[Makemake]]\\n* {{Dp|Gonggong}}\\n* [[Eris (dwarf planet)|Eris]]\\n* {{Dp|Sedna}}\\n*  [[List of possible dwarf planets|''more candidates...'']]\\n}}}}\"},\"satellites\":{\"wt\":\"758<ref name=\\\"JPLbodies\\\" group=\\\"D\\\">{{Cite web |title=Solar System Objects |url=https://ssd.jpl.nasa.gov/ |url-status=live |archive-url=https://web.archive.org/web/20210707142304/https://ssd.jpl.nasa.gov/ |archive-date=7 July 2021 |access-date=14 August 2023 |publisher=NASA/JPL Solar System Dynamics }}</ref>\"},\"minorplanets\":{\"wt\":\"1,462,402<ref name=\\\"MPCSummary\\\" group=\\\"D\\\">{{Cite web |title=Latest Published Data |url=https://minorplanetcenter.net/mpc/summary |access-date=27 May 2024 |website=The International Astronomical Union Minor Planet Center |archive-date=5 March 2019 |archive-url=https://web.archive.org/web/20190305034947/https://minorplanetcenter.net/mpc/summary |url-status=live }}</ref>\"},\"comets\":{\"wt\":\"4,629<ref name=MPCSummary group=\\\"D\\\"/>\"},\"inclination\":{\"wt\":\"~60\u00b0, to the ecliptic{{Refn |group=lower-alpha |name=angle}}<!-- If anyone can find a cited value for the inclination of the Solar System's invariable plane to the galactic plane, please replace this value -->\"},\"galacticcenter\":{\"wt\":\"{{longitem|24,000\u201328,000 ly}}<ref name=\\\"francis14\\\">{{cite journal |first1=Charles |last1=Francis |first2=Erik |last2=Anderson |s2cid= 119235554 |title=Two estimates of the distance to the Galactic Centre |journal=[[Monthly Notices of the Royal Astronomical Society]] |date=June 2014 |volume=441 |issue=2 |pages=1105\u20131114 |doi=10.1093/mnras/stu631 |doi-access=free |bibcode= 2014MNRAS.441.1105F |arxiv=1309.2629}}</ref>\"},\"orbitalspeed\":{\"wt\":\"{{longitem|720,000 km/h (450,000 mi/h)<ref name=\\\"roughfactsofthesun\\\" />}}\"},\"orbitalperiod\":{\"wt\":\"~230 [[million year]]s<ref name=\\\"roughfactsofthesun\\\">{{Cite web |title=Sun: Facts |url=https://science.nasa.gov/sun/facts/ |access-date=19 April 2024 |website=science.nasa.gov |date=14 November 2017 |language=en-US |archive-date=19 April 2024 |archive-url=https://web.archive.org/web/20240419151126/https://science.nasa.gov/sun/facts/ |url-status=live }}</ref>\"},\"spectral\":{\"wt\":\"[[G-type main-sequence star|G2V]]\"}},\"i\":0}}]}' id=\"mwFg\">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} Solar System The Sun , planets , moons , and dwarf planets [ a ] (true color, size to scale, distances not to scale) Age 4.568 billion years [ b ] Location .mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0} Local Interstellar Cloud Local Bubble [ 1 ] Orion\u2013Cygnus Arm Milky Way [ 2 ] Nearest star Proxima Centauri (4.2465 ly ) [ D 1 ] Alpha Centauri (4.36 ly) [ D 2 ] Population Stars Sun Planets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Known dwarf planets Ceres Orcus Pluto Haumea Quaoar Makemake Gonggong Eris Sedna more candidates... Known natural satellites 758 [ D 3 ] Known minor planets 1,462,402 [ D 4 ] Known comets 4,629 [ D 4 ] Planetary system Star spectral type G2V Frost line ~5 AU [ 3 ] Semi-major axis of outermost planet 30.07 AU [ D 5 ] ( .mw-parser-output .nobold{font-weight:normal} Neptune ) Kuiper cliff 50\u201370 AU [ 4 ] [ 5 ] Heliopause detected at 120 AU [ 6 ] Hill sphere 178,000\u2013227,000 AU (2.82\u20133.59 ly ; 0.865\u20131.1 pc ) [ 7 ] [ 8 ] Orbit about Galactic Center Invariable -to- galactic plane inclination ~60\u00b0, to the ecliptic [ c ] Distance to Galactic Center 24,000\u201328,000 ly [ 9 ] Orbital speed 720,000 km/h (450,000 mi/h) [ 10 ] Orbital period ~230 million years [ 10 ] The Solar System is the gravitationally bound system of the Sun and the masses that orbit it, most prominently its eight planets , of which Earth is one. The system formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, creating the Sun and a protoplanetary disc from which the orbiting bodies assembled. The Sun accounts for 99.86% of the Solar System's total mass. Inside the Sun's core , hydrogen is fused into helium, releasing energy that is emitted through the Sun's photosphere . This creates the heliosphere and a decreasing temperature gradient across the Solar System. The next most massive objects of the system are the eight planets, which by definition dominate the orbits they occupy. Closest to the Sun in order of increasing distance are the terrestrial planets \u2013 Mercury , Venus , Earth and Mars . These are the planets of the inner Solar System . Earth and Mars are the only planets that orbit within the Sun's habitable zone , in which sunlight can keep surface water liquid under atmospheric pressure. Beyond the frost line at about five astronomical units (AU), {{Cite journal |last=Standish |first=E. M. |date=April 2005 |title=The Astronomical Unit now |journal=Proceedings of the International Astronomical Union |volume=2004 |issue=IAUC196 |pages=163\u2013179 |bibcode=2005tvnv.conf..163S |doi=10.1017/S1743921305001365 |s2cid=55944238 |doi-access=free}}</ref>\"}},\"i\":0}}]}'> [ d ] are the planets of the outer Solar System : two gas giants \u2013 Jupiter and Saturn \u2013 and two ice giants \u2013 Uranus and Neptune . Jupiter and Saturn possess nearly 90% of the non-stellar mass of the Solar System. Objects of planetary mass that do not dominate their orbit but orbit the Sun directly are called dwarf planets . The International Astronomical Union 's Minor Planet Center lists Ceres , Pluto , Eris , Makemake , and Haumea as dwarf planets. [ 12 ] Four other Solar System objects are generally identified as such: Orcus , Quaoar , Gonggong , and Sedna . [ 13 ] Less massive than the dwarf planets are the vast number of small Solar System bodies , such as asteroids , comets , centaurs , meteoroids , and interplanetary dust clouds . [ e ] The dwarf planet Ceres and many of these smaller bodies are located in the asteroid belt (between Mars's and Jupiter's orbit), while all other dwarf planets are members of populations of trans-Neptunian objects , which may be found in the Kuiper belt just outside Neptune or in the further scattered disc . Many objects in the solar system do not orbit the Sun directly and are instead natural satellites , commonly called 'moons', of larger bodies. These can be found throughout the Solar System in sizes from planetary-mass moons at their largest to much less massive moonlets at their smallest. The largest two moons ( Ganymede of Jupiter and Titan of Saturn) are larger (though less massive) than the smallest planet (Mercury), while the seven most massive, which includes Earth's Moon , are more massive and larger than any of the dwarf planets. Within the heliosphere, the Solar System is constantly flooded by the charged plasma particles of the solar wind , which, along with interplanetary dust, gas and cosmic rays , form an interplanetary medium between the bodies of the Solar System. At around 70\u201390 AU from the Sun, the solar wind is halted by the interstellar medium , resulting in the heliopause and the border of the interplanetary medium to interstellar space . Further out somewhere beyond 2,000 AU from the Sun extends the outermost region of the Solar System, the theorized Oort cloud , the source for long-period comets , stretching to the edge of the Solar System, the edge of its Hill sphere , at 178,000\u2013227,000 AU (2.81\u20133.59 ly ) , where its gravitational potential becomes equal to the galactic potential. [ 14 ] The Solar System currently moves through a cloud of interstellar medium called the Local Cloud . The closest star to the Solar System, Proxima Centauri , is 269,000 AU (4.25 ly) away. Both are within the Local Bubble , a relatively small 1,000 light-years (ly) wide region of the Milky Way . Definition The Solar System includes the Sun and all objects that are bound to it by gravity and orbit it. [ 15 ] [ 16 ] [ 17 ] The International Astronomical Union describes the Solar System as all objects that are bound by the gravity of the Sun, the Sun itself, its eight planets, and the other celestial bodies which orbit it. [ 18 ] NASA describes the Solar System as a planetary system , including the Sun and all objects that orbit it. [ 19 ] Capitalization of the name varies. When not used as a proper noun and written without capitalization, \"solar system\" may refer to either the Solar System itself or any system reminiscent of the Solar System. [ 15 ] The International Astronomical Union , the authoritative body regarding astronomical nomenclature , specifies capitalizing the names of all individual astronomical objects but uses mixed \"Solar System\" and \"solar system\" structures in their naming guidelines document. [ 20 ] Formation and evolution Main article: Formation and evolution of the Solar System Past Diagram of the early Solar System's protoplanetary disk , out of which Earth and other Solar System bodies formed The Solar System formed at least 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud . {{Cite journal |last1=Bouvier |first1=A. |last2=Wadhwa |first2=M. |author-link2=Meenakshi Wadhwa |year=2010 |title=The age of the Solar System redefined by the oldest Pb\u2013Pb age of a meteoritic inclusion |journal=Nature Geoscience |volume=3 |issue=9 |pages= 637\u2013641 |bibcode=2010NatGe...3..637B |doi=10.1038/NGEO941 |s2cid=56092512}}</ref>\"}},\"i\":0}}]}'> [ b ] This initial cloud was likely several light-years across and probably birthed several stars. [ 22 ] As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars. [ 23 ] As the pre-solar nebula [ 23 ] collapsed, conservation of angular momentum caused it to rotate faster. The center, where most of the mass collected, became increasingly hotter than the surroundings. [ 22 ] As the contracting nebula spun faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU [ 22 ] [ 24 ] and a hot, dense protostar at the center. [ 25 ] [ 26 ] The planets formed by accretion from this disc, [ 27 ] in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. Hundreds of protoplanets may have existed in the early Solar System, but they either merged or were destroyed or ejected, leaving the planets, dwarf planets, and leftover minor bodies . [ 28 ] [ 29 ] In the inner Solar System, heat from the accretion process exceeded the boiling point of hydrocarbon molecules for the first million years, leading to low carbon content for the inner planets. The boundary for this process has been dubbed the soot line . [ 30 ] As the Solar System disk cooled, this line moved inward and now lies within Earth's orbit around the Sun. [ 31 ] Material other than metals and silicates, due to their higher boiling points, could not persist in solid form. Here planets formed that are mainly rocky, which are Mercury, Venus, Earth, and Mars. Because these refractory materials only comprised a small fraction of the solar nebula, the terrestrial planets could not grow very large. [ 28 ] The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid. The ices that formed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium, the lightest and most abundant elements. [ 28 ] Leftover debris that never became planets congregated in regions such as the asteroid belt, Kuiper belt, and Oort cloud. [ 28 ] Within 50 million years, the pressure and density of hydrogen in the center of the protostar became great enough for it to begin thermonuclear fusion . [ 32 ] As helium accumulates at its core, the Sun is growing brighter; [ 33 ] early in its main-sequence life its brightness was 70% that of what it is today. [ 34 ] The temperature, reaction rate , pressure, and density increased until hydrostatic equilibrium was achieved: the thermal pressure counterbalancing the force of gravity. At this point, the Sun became a main-sequence star. [ 35 ] Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the protoplanetary disc into interstellar space. [ 33 ] Following the dissipation of the protoplanetary disk , the Nice model proposes that gravitational encounters between planetesimals and the gas giants caused each to migrate into different orbits. This led to dynamical instability of the entire system, which scattered the planetesimals and ultimately placed the gas giants in their current positions. During this period, the grand tack hypothesis suggests that a final inward migration of Jupiter dispersed much of the asteroid belt, leading to the Late Heavy Bombardment of the inner planets. [ 36 ] [ 37 ] Present and future The Solar System remains in a relatively stable, slowly evolving state by following isolated, gravitationally bound orbits around the Sun. [ 38 ] Although the Solar System has been fairly stable for billions of years, it is technically chaotic , and may eventually be disrupted . There is a small chance that another star will pass through the Solar System in the next few billion years. Although this could destabilize the system and eventually lead millions of years later to expulsion of planets, collisions of planets, or planets hitting the Sun, it would most likely leave the Solar System much as it is today. [ 39 ] The current Sun compared to its peak size in the red-giant phase The Sun's main-sequence phase, from beginning to end, will last about 10 billion years for the Sun compared to around two billion years for all other subsequent phases of the Sun's pre- remnant life combined. [ 40 ] The Solar System will remain roughly as it is known today until the hydrogen in the core of the Sun has been entirely converted to helium, which will occur roughly 5 billion years from now. This will mark the end of the Sun's main-sequence life. At that time, the core of the Sun will contract with hydrogen fusion occurring along a shell surrounding the inert helium, and the energy output will be greater than at present. The outer layers of the Sun will expand to roughly 260 times its current diameter, and the Sun will become a red giant . Because of its increased surface area, the surface of the Sun will be cooler ( 2,600 K (4,220 \u00b0F) at its coolest) than it is on the main sequence. [ 40 ] The expanding Sun is expected to vaporize Mercury as well as Venus, and render Earth and Mars uninhabitable (possibly destroying Earth as well). [ 41 ] [ 42 ] Eventually, the core will be hot enough for helium fusion; the Sun will burn helium for a fraction of the time it burned hydrogen in the core. The Sun is not massive enough to commence the fusion of heavier elements, and nuclear reactions in the core will dwindle. Its outer layers will be ejected into space, leaving behind a dense white dwarf , half the original mass of the Sun but only the size of Earth. [ 40 ] The ejected outer layers may form a planetary nebula , returning some of the material that formed the Sun \u2013 but now enriched with heavier elements like carbon \u2013 to the interstellar medium . [ 43 ] [ 44 ] General characteristics A color enhanced photograph from the Moon of a range of components of the Solar System. The three dots at the lower left are from left to right the planets Saturn , Mars , and Mercury , and in the middle of the picture rises the Sun's corona over the dark limb of the Moon, which is from the right lit by earthshine . Astronomers sometimes divide the Solar System structure into separate regions. The inner Solar System includes Mercury, Venus, Earth, Mars, and the bodies in the asteroid belt . The outer Solar System includes Jupiter, Saturn, Uranus, Neptune, and the bodies in the Kuiper belt . [ 45 ] Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune . [ 46 ] Composition Further information: List of Solar System objects and List of interstellar and circumstellar molecules The principal component of the Solar System is the Sun, a G-type main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally. [ 47 ] The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids , and comets) together comprise less than 0.002% of the Solar System's total mass. {{Cite arXiv |eprint=astro-ph/0512256 |first=Alessandro |last=Morbidelli |title=Origin and dynamical evolution of comets and their reservoirs |date=2005 }}</ref> the Kuiper belt (estimated at 0.1 Earth mass)<ref name=\\\"Delsanti-Beyond_The_Planets\\\"/> and the asteroid belt (estimated to be 0.0005 Earth mass)<ref name=\\\"Krasinsky2002\\\"/> for a total, rounded upwards, of ~37 Earth masses, or 8.1% of the mass in orbit around the Sun. With the combined masses of Uranus and Neptune (~31 Earth masses) subtracted, the remaining ~6 Earth masses of material comprise 1.3% of the total orbiting mass.\"},\"name\":{\"wt\":\"footnoteD\"},\"group\":{\"wt\":\"lower-alpha\"}},\"i\":0}}]}'> [ f ] The Sun is composed of roughly 98% hydrogen and helium, [ 51 ] as are Jupiter and Saturn. [ 52 ] [ 53 ] A composition gradient exists in the Solar System, created by heat and light pressure from the early Sun; those objects closer to the Sun, which are more affected by heat and light pressure, are composed of elements with high melting points. Objects farther from the Sun are composed largely of materials with lower melting points. [ 54 ] The boundary in the Solar System beyond which those volatile substances could coalesce is known as the frost line , and it lies at roughly five times the Earth's distance from the Sun. [ 3 ] Orbits Animations of the Solar System's inner planets orbiting. Each frame represents 2 days of motion. Animations of the Solar System's outer planets orbiting. This animation is 100 times faster than the inner planet animation. The planets and other large objects in orbit around the Sun lie near the invariable plane of the Solar System , as does Earth's orbit, known as the ecliptic , and most closely the orbit of Jupiter, with an inclination to it of 0.3219\u00b0. [ 55 ] Smaller icy objects such as comets frequently orbit at significantly greater angles to this plane. [ 56 ] [ 57 ] Most of the planets in the Solar System have secondary systems of their own, being orbited by natural satellites called moons. All of the largest natural satellites are in synchronous rotation , with one face permanently turned toward their parent. The four giant planets have planetary rings, thin discs of tiny particles that orbit them in unison. [ 58 ] As a result of the formation of the Solar System , planets and most other objects orbit the Sun in the same direction that the Sun is rotating. That is, counter-clockwise, as viewed from above Earth's north pole. [ 59 ] There are exceptions, such as Halley's Comet . [ 60 ] Most of the larger moons orbit their planets in prograde direction, matching the direction of planetary rotation; Neptune's moon Triton is the largest to orbit in the opposite, retrograde manner. [ 61 ] Most larger objects rotate around their own axes in the prograde direction relative to their orbit, though the rotation of Venus is retrograde. [ 62 ] To a good first approximation, Kepler's laws of planetary motion describe the orbits of objects around the Sun. [ 63 ] : 433\u2013437 These laws stipulate that each object travels along an ellipse with the Sun at one focus , which causes the body's distance from the Sun to vary over the course of its year. A body's closest approach to the Sun is called its perihelion , whereas its most distant point from the Sun is called its aphelion . [ 64 ] : 9-6 With the exception of Mercury, the orbits of the planets are nearly circular, but many comets, asteroids, and Kuiper belt objects follow highly elliptical orbits. Kepler's laws only account for the influence of the Sun's gravity upon an orbiting body, not the gravitational pulls of different bodies upon each other. On a human time scale, these perturbations can be accounted for using numerical models , [ 64 ] : 9-6 but the planetary system can change chaotically over billions of years. [ 65 ] The angular momentum of the Solar System is a measure of the total amount of orbital and rotational momentum possessed by all its moving components. [ 66 ] Although the Sun dominates the system by mass, it accounts for only about 2% of the angular momentum. [ 67 ] [ 68 ] The planets, dominated by Jupiter, account for most of the rest of the angular momentum due to the combination of their mass, orbit, and distance from the Sun, with a possibly significant contribution from comets. [ 67 ] Orbital periods and velocities of the planets Planet Orbital period (days) Orbital period (Earth years) Orbital velocity [ 69 ] Mercury 87.969 0.241 47.9 km/s (29.8 mi/s) Venus 224.701 0.615 35.0 km/s (21.7 mi/s) Earth 365.256 1.000 29.8 km/s (18.5 mi/s) Mars 686.980 1.881 24.1 km/s (15.0 mi/s) Jupiter 4,332.589 11.862 13.1 km/s (8.1 mi/s) Saturn 10,759.22 29.457 9.7 km/s (6.0 mi/s) Uranus 30,688.5 84.020 6.8 km/s (4.2 mi/s) Neptune 60,182 164.8 5.4 km/s (3.4 mi/s) Distances and scales Relative orbital distances in the Solar System visualized as a condensed rectangle The radius of the Sun is 0.0047 AU (700,000 km; 400,000 mi) . [ 70 ] Thus, the Sun occupies 0.00001% (1 part in 10 7 ) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 \u22126 ) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi) , whereas the most distant planet, Neptune, is 30 AU from the Sun. [ 53 ] [ 71 ] With a few exceptions, the farther a planet or belt is from the Sun, the larger the distance between its orbit and the orbit of the next nearest object to the Sun. For example, Venus is approximately 0.33 AU farther out from the Sun than Mercury, whereas Saturn is 4.3 AU out from Jupiter, and Neptune lies 10.5 AU out from Uranus. Attempts have been made to determine a relationship between these orbital distances, like the Titius\u2013Bode law [ 72 ] and Johannes Kepler's model based on the Platonic solids , [ 73 ] but ongoing discoveries have invalidated these hypotheses. [ 74 ] Some Solar System models attempt to convey the relative scales involved in the Solar System in human terms. Some are small in scale (and may be mechanical \u2013 called orreries ) \u2013 whereas others extend across cities or regional areas. [ 75 ] The largest such scale model, the Sweden Solar System , uses the 110-meter (361-foot) Avicii Arena in Stockholm as its substitute Sun, and, following the scale, Jupiter is a 7.5-meter (25-foot) sphere at Stockholm Arlanda Airport , 40 km (25 mi) away, whereas the farthest current object, Sedna , is a 10 cm (4 in) sphere in Lule\u00e5 , 912 km (567 mi) away. [ 76 ] [ 77 ] At that scale, the distance to Proxima Centauri would be roughly 8 times further than the Moon is from Earth. If the Sun\u2013Neptune distance is scaled to 100 metres (330 ft) , then the Sun would be about 3 cm (1.2 in) in diameter (roughly two-thirds the diameter of a golf ball), the giant planets would be all smaller than about 3 mm (0.12 in) , and Earth's diameter along with that of the other terrestrial planets would be smaller than a flea ( 0.3 mm or 0.012 in ) at this scale. [ 78 ] Comparison of the distances between planets, with the white bar showing orbital variations. The size of the planets is not to scale. Habitability Main article: Planetary habitability in the Solar System \"},\"image1\":{\"wt\":\"PIA21424 - The TRAPPIST-1 Habitable Zone.jpg\"},\"alt1\":{\"wt\":\"\"},\"caption1\":{\"wt\":\"Comparison of the habitable zones of the Solar System and [[TRAPPIST-1]], an ultracool red dwarf star known to have seven terrestrial planets in stable orbits around the star.\\n <!--image 2-->\"},\"image2\":{\"wt\":\"Diagram of different habitable zone regions by Chester Harman.jpg\"},\"alt2\":{\"wt\":\"\"},\"caption2\":{\"wt\":\"Comparison of the [[habitable zone]]s for different stellar temperatures, with a sample of known exoplanets plus the Earth, Mars, and Venus. From top to bottom are an [[F-type main-sequence star]], a [[G-type main-sequence star|yellow dwarf]] (G-type main-sequence star), an [[orange dwarf]] (K-type main-sequence star), a typical [[red dwarf]], and an [[ultra-cool dwarf]].\"}},\"i\":0}}]}' id=\"mwAuU\">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}} Comparison of the habitable zones of the Solar System and TRAPPIST-1 , an ultracool red dwarf star known to have seven terrestrial planets in stable orbits around the star. Comparison of the habitable zones for different stellar temperatures, with a sample of known exoplanets plus the Earth, Mars, and Venus. From top to bottom are an F-type main-sequence star , a yellow dwarf (G-type main-sequence star), an orange dwarf (K-type main-sequence star), a typical red dwarf , and an ultra-cool dwarf . The zone of habitability of the Solar System is conventionally located in the inner Solar System around Earth, where atmospheric liquid water is enabled by the Sun. [ 79 ] Besides solar energy, the primary characteristic of the Solar System enabling the presence of life is the heliosphere and planetary magnetic fields (for those planets that have them). These magnetic fields partially shield the Solar System from high-energy interstellar particles called cosmic rays . The density of cosmic rays in the interstellar medium and the strength of the Sun's magnetic field change on very long timescales, so the level of cosmic-ray penetration in the Solar System varies, though by how much is unknown. [ 80 ] Habitability in the Solar System is though not solely dependent on surface conditions, and furthermore the Solar environment, since there might be habitablity in potential subsurface oceans of various Solar System bodies, [ 81 ] or cloud layers of some planets, particularly Venus. [ 82 ] Comparison with extrasolar systems Analysis of Kepler data suggests that observed planetary systems in the Milky Way fall into three groups: \"similar\", which comprise planets of similar sizes similar distances apart and with highly circular orbits; \"ordered\", in which the masses of planets tend to increase with distance from their star, and \"mixed\", which show no pattern in masses whatsoever. The Solar System is an ordered system, as are 37% of observed systems. Similar systems however are the majority, comprising 59% of observed systems, while mixed systems comprise just 4%. [ 83 ] Compared to many extrasolar systems, the Solar System stands out in lacking planets interior to the orbit of Mercury. [ 84 ] [ 85 ] The known Solar System lacks super-Earths , planets", "Roman Empire 27 BC\u2013476/1453 AD state and civilization .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} For other uses, see Roman Empire (disambiguation) . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> {{Cite book |last=Morley |first=Neville |title=The Roman Empire: Roots of Imperialism |date=2010 |publisher=Pluto Press |isbn=978-0-7453-2870-6}}; {{Cite book |last=Diamond |first=Jared |title=Collapse: How Societies Choose to Fail or Succeed |edition=Revised |date=2011 |isbn=978-1-1015-0200-6 |page=13 |publisher=Penguin |author-link=Jared Diamond}}</ref> This is a modern convention, as the Empire continued to be seen as a single state even after the supposed \\\"split\\\" of 395, which was in fact one of many splits since 286.<ref>{{Cite journal |last=Sandberg |first=Kaj |date=2008 |title=The So-Called Division of the Roman Empire in AD 395: Notes on a Persistent Theme in Modern Historiography |url=https://journal.fi/arctos/article/view/85853 |journal=Arctos |volume=42 |pages=199\u2013213 |issn=0570-734-X}}</ref>}}<br />{{Nowrap|AD 395{{snd}}476/480 {{Nobold|([[Western Roman Empire|Western]])}}}}<br />{{Nowrap|AD 395\u20131453}} {{Nobold|([[Byzantine Empire|Eastern]])}}}}\"},\"p1\":{\"wt\":\"Roman Republic\"},\"s1\":{\"wt\":\"Western Roman Empire\"},\"s2\":{\"wt\":\"Byzantine Empire{{!}}Eastern Roman Empire\"},\"image_map\":{\"wt\":\"Roman Empire Trajan 117AD.png\"},\"image_map_caption\":{\"wt\":\"{{Legend|#b23938|Roman Empire in AD 117 at its greatest territorial extent, at the time of [[Trajan]]'s death}} {{Legend|#d28989|[[Vassal state]]s{{Sfnp|Bennett|1997}}{{Efn|Fig. 1. Regions east of the [[Euphrates]] were held only in the years 116\u2013117.}}}}\"},\"image_map2\":{\"wt\":\"Animated map of the Roman territorial evolution from the rise of the city-state of Rome to the fall of the Western Roman Empire.gif\"},\"map_caption2\":{\"wt\":\"Roman territorial evolution from the rise of the city-state of Rome to the fall of the Western Roman Empire\"},\"capital\":{\"wt\":\"{{Plainlist}}\\n* [[Rome]] {{nwr|(27 BC{{snd}}AD 476){{Efn|In 286, Emperor Diocletian divided the Roman Empire into two administrative units\u2013[[Eastern Roman Empire|East]] and [[Western Roman Empire|West]]\u2013an arrangement that periodically returned until the two halves were permanently divided in 395.<ref name=\\\":1\\\">{{Cite book |url=https://books.google.com/books?id=QrKTEAAAQBAJ |title=Ancient Rome: The Definitive Visual History |date=2023 |publisher=Dorling Kindersley |isbn=978-0-2416-3575-9 |page=276 |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622190835/https://books.google.com/books?id=QrKTEAAAQBAJ |url-status=live}}</ref> Although the halves were independent in practice, the Romans continued to consider the Roman Empire to be a single undivided state with two co-equal emperors until the fall of the western half in 476/480.<ref name=\\\":1\\\"/> Although emperors at times governed from other cities (notably [[Mediolanum]] and [[Ravenna]] in the West and [[Nicomedia]] in the East), Rome remained the ''[[de jure]]'' capital of the entire Roman Empire. In 330, Emperor [[Constantine the Great|Constantine I]] made Constantinople a second and new capital of the empire (\\\"Second Rome\\\" or \\\"New Rome\\\").<ref>{{Cite book |last=Classen |first=Albrecht |url=https://books.google.com/books?id=ez_edSWAQGAC |title=Handbook of Medieval Studies |date=2010 |publisher=Walter de Gruyter |isbn=978-3-1102-1558-8 |chapter=The changing shape of Europe |quote=Constantine the Great transferred the capital of the Roman Empire from Rome to the newly-founded city of Constantinople |access-date=26 April 2023 |archive-date=10 March 2024 |archive-url=https://web.archive.org/web/20240310115424/https://books.google.com/books?id=ez_edSWAQGAC |url-status=live}}</ref><ref>{{Cite book |last1=Price |first1=Jonathan J. |url=https://books.google.com/books?id=T4lmEAAAQBAJ |title=Rome: An Empire of Many Nations |last2=Finkelberg |first2=Margalit |last3=Shahar |first3=Yuval |date=2022 |publisher=Cambridge University Press |isbn=978-1-0092-5622-3 |page=19 |quote=the capital of the Empire was transferred from Rome to Constantinople in the fourth century |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622191212/https://books.google.com/books?id=T4lmEAAAQBAJ |url-status=live}}</ref><ref>{{Cite book |last=Erdkamp |first=Paul |url=https://books.google.com/books?id=yaM0AAAAQBAJ |title=The Cambridge Companion to Ancient Rome |date=2013 |publisher=Cambridge University Press |isbn=978-0-5218-9629-0 |page=202 |quote=Constantine sounded the death knell for Rome as a vital political centre with the dedication of his new imperial capital at Constantinople}}</ref><ref>{{Cite book |last=Bjornlie |first=M. Shane |url=https://books.google.com/books?id=VI3ebybOl0oC |title=Politics and Tradition Between Rome, Ravenna and Constantinople: A Study of Cassiodorus and the Variae, 527\u2013554 |date=2013 |publisher=Cambridge University Press |isbn=978-1-1070-2840-1 |page=41 |quote=As a new capital, Constantinople provided a stage for imperial prestige that did not depend on association with the traditions of the senatorial establishment at Rome |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622191456/https://books.google.com/books?id=VI3ebybOl0oC |url-status=live}}</ref><ref>{{Cite book |last=Coffler |first=Gail H. |url=https://books.google.com/books?id=v_GoZpiIpAEC |title=Melville's Allusions to Religion: A Comprehensive Index and Glossary: A Comprehensive Index and Glossary |date=2004 |publisher=ABC-CLIO |isbn=978-0-3130-7270-3 |page=181 |quote=It became Constantinople, capital of the entire Roman Empire |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622190856/https://books.google.com/books?id=v_GoZpiIpAEC |url-status=live}}</ref><ref>{{Cite book |last=Maxwell |first=Kathleen |url=https://books.google.com/books?id=G0uoDQAAQBAJ |title=Between Constantinople and Rome: An Illuminated Byzantine Gospel Book (Paris gr. 54) and the Union of Churches |date=2016 |publisher=Routledge |isbn=978-1-3519-5584-3 |chapter=Art and Diplomacy in Late Thirteenth-century Constantinople: Paris 54 and the Union of Churches |quote=Constantine the Great, the emperor who moved the capital of the Roman Empire from Rome to Constantinople |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622193552/https://books.google.com/books?id=G0uoDQAAQBAJ |url-status=live}}</ref> For a time, mostly over the course of the later decades of the fourth century, Rome continued to hold greater symbolic status on account of its greater antiquity as imperial capital.<ref>{{Cite book |last1=Grig |first1=Lucy |url=https://books.google.com/books?id=HHlpAgAAQBAJ |title=Two Romes: Rome and Constantinople in Late Antiquity |last2=Kelly |first2=Gavin |date=2012 |publisher=Oxford University Press |isbn=978-0-1999-2118-8 |page=237 |access-date=26 April 2023 |archive-date=10 March 2024 |archive-url=https://web.archive.org/web/20240310115405/https://books.google.com/books?id=HHlpAgAAQBAJ |url-status=live}}</ref> From at least 361 onwards, senators belonging to the [[Byzantine senate|new senate]] in Constantinople enjoyed the same status and privileges as senators of the [[Roman Senate]], to which the new senate was largely identical.<ref>{{Cite book |last=Loewenstein |first=K. |url=https://books.google.com/books?id=7uMRBwAAQBAJ |title=The Governance of ROME |date=2012 |publisher=Springer |isbn=978-9-4010-2400-6 |page=443 |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622190858/https://books.google.com/books?id=7uMRBwAAQBAJ |url-status=live}}</ref> By 450, Constantinople was much grander in size and adornment than Rome and unquestionably senior in status.<ref>{{Cite book |last=Harris |first=Jonathan |url=https://books.google.com/books?id=UTjUAwAAQBAJ |title=Constantinople: Capital of Byzantium |date=2009 |publisher=A&C Black |isbn=978-0-8264-3086-1 |page=31 |access-date=26 April 2023 |archive-date=22 June 2023 |archive-url=https://web.archive.org/web/20230622190857/https://books.google.com/books?id=UTjUAwAAQBAJ |url-status=live}}</ref>}}}}\\n* [[Constantinople]] {{nwr|(330\u20131453)}}<!--De jure capital of the entire empire (not just the east), see the note above-->{{Efn|In 1204, the crusaders of the [[Fourth Crusade]] captured Constantinople and established the [[Latin Empire]]. The city remained under foreign rule until 1261, when it was captured by the [[Empire of Nicaea]] (a Byzantine/Roman successor state). Nicaea is usually considered the \\\"legitimate\\\" continuation of the Roman Empire during the \\\"interregnum\\\" 1204\u20131261 (over its rivals in [[Empire of Trebizond|Trebizond]] and [[Empire of Thessalonica|Thessalonica]]) since it managed to retake Constantinople.{{Sfnp|Treadgold|1997|p=734}} Whether there was an interregnum at all is debatable given that the crusaders envisioned the Latin Empire to be the same empire as its predecessor (and not a new state).<ref name=\\\":0\\\">{{Cite book |last=Tricht |first=Filip Van |url=https://books.google.com/books?id=JlnPm2riK1UC&q=imperator+constantinopolitanus&pg=PA68 |title=The Latin Renovatio of Byzantium: The Empire of Constantinople (1204\u20131228) |date=2011 |publisher=Brill |isbn=978-9-0042-0323-5 |pages=61\u201382 |access-date=26 April 2023 |archive-date=6 April 2023 |archive-url=https://web.archive.org/web/20230406180853/https://books.google.com/books?id=JlnPm2riK1UC&q=imperator%20constantinopolitanus&pg=PA68 |url-status=live}}</ref>}}\\n{{Endplainlist}}\"},\"common_languages\":{\"wt\":\"{{Plainlist}}\\n* Official: initially [[Latin]], increasingly [[Greek language|Greek]] as well or instead{{sfnm|Rochette|2023|1pp=258\u2013285|Goldhill|2024|2p=850}}\\n* Other:\\n* [[Languages of the Roman Empire|Regional languages]]\\n{{Endplainlist}}\"},\"religion\":{\"wt\":\"{{Indented plainlist}}\\n* [[Roman imperial cult|Imperial cult]]-driven [[Religion in ancient Rome|polytheism]] {{nwr|(until AD 380)}}\\n* [[Nicene Christianity]] {{nwr|([[State church of the Roman Empire|officially]] from AD 380)}}\\n{{Endplainlist}}\"},\"government_type\":{\"wt\":\"[[Autocracy]]\"},\"leader_title1\":{\"wt\":\"[[Roman emperor#Titles|Emperor]]\"},\"leader_name1\":{\"wt\":\"([[List of Roman emperors|List]])\"},\"era\":{\"wt\":\"[[Classical era]] to [[Late Middle Ages]]<br />([[Timeline of Roman history|Timeline]])\"},\"stat_year1\":{\"wt\":\"{{nobold|25 BC}}\"},\"stat_area1\":{\"wt\":\"2750000\"},\"stat_pop1\":{\"wt\":\"56,800,000\"},\"stat_year2\":{\"wt\":\"{{nobold|AD 117}}\"},\"stat_area2\":{\"wt\":\"5000000\"},\"stat_year3\":{\"wt\":\"{{nobold|AD 390}}\"},\"stat_area3\":{\"wt\":\"3400000\"},\"currency\":{\"wt\":\"[[Denarius]], [[sestertius]],{{Efn|Abbreviated \\\"HS\\\". Prices and values are usually expressed in sesterces.}} [[aureus]], [[Solidus (coin)|solidus]], [[Solidus (coin)|nomisma]]\"},\"demonym\":{\"wt\":\"[[Roman people|Roman]]\"},\"ref_area1\":{\"wt\":\"<ref name=\\\"size\\\">{{Cite journal |last=Taagepera |first=Rein |author-link=Rein Taagepera |date=1979 |title=Size and Duration of Empires: Growth-Decline Curves, 600 B.C. to 600 A.D |journal=Social Science History |volume=3 |issue=3/4 |doi=10.2307/1170959 |page=125 |jstor=1170959 |issn=0145-5532}}</ref>\"},\"ref_area2\":{\"wt\":\"<ref name=\\\"size\\\"/><ref name=\\\"East-West\\\">{{Cite journal |last1=Turchin |first1=Peter |author-link=Peter Turchin |last2=Adams |first2=Jonathan M. |last3=Hall |first3=Thomas D. |date=2006 |title=East-West Orientation of Historical Empires |url=http://peterturchin.com/PDF/Turchin_Adams_Hall_2006.pdf |journal=Journal of World-Systems Research |volume=12 |issue=2 |page=222 |access-date=5 February 2016 |archive-date=17 May 2016 |archive-url=https://arquivo.pt/wayback/20160517210851/http://peterturchin.com/PDF/Turchin_Adams_Hall_2006.pdf |url-status=dead}}</ref><ref name=\\\"OxfordArea\\\">{{Cite book|last1=Bang|first1=Peter Fibiger|url=https://books.google.com/books?id=9mkLEAAAQBAJ&pg=PA92|title=The Oxford World History of Empire: Volume One: The Imperial Experience|last2=Bayly|first2=C. A.|last3=Scheidel|first3=Walter|year=2020|publisher=Oxford University Press|isbn=978-0-19-977311-4|pages=92\u201394|language=en}}</ref>\"},\"ref_area3\":{\"wt\":\"<ref name=\\\"size\\\"/>\"},\"ref_pop1\":{\"wt\":\"<ref>{{Cite journal |last=Durand |first=John D. |date=1977 |title=Historical Estimates of World Population: An Evaluation |url=http://repository.upenn.edu/cgi/viewcontent.cgi?article=1009&context=psc_penn_papers |journal=Population and Development Review |volume=3 |issue=3 |doi=10.2307/1971891 |pages=253\u2013296 |jstor=1971891 |access-date=30 October 2018 |archive-date=16 October 2019 |archive-url=https://web.archive.org/web/20191016190031/http://repository.upenn.edu/cgi/viewcontent.cgi?article=1009&context=psc_penn_papers |url-status=live}}</ref>\"}},\"i\":0}}]}' id=\"mwEA\">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} .mw-parser-output .ib-country{border-collapse:collapse;line-height:1.2em}.mw-parser-output .ib-country td,.mw-parser-output .ib-country th{border-top:1px solid #a2a9b1;padding:0.4em 0.6em 0.4em 0.6em}.mw-parser-output .ib-country .mergedtoprow .infobox-header,.mw-parser-output .ib-country .mergedtoprow .infobox-label,.mw-parser-output .ib-country .mergedtoprow .infobox-data,.mw-parser-output .ib-country .mergedtoprow .infobox-full-data,.mw-parser-output .ib-country .mergedtoprow .infobox-below{border-top:1px solid #a2a9b1;padding:0.4em 0.6em 0.2em 0.6em}.mw-parser-output .ib-country .mergedrow .infobox-label,.mw-parser-output .ib-country .mergedrow .infobox-data,.mw-parser-output .ib-country .mergedrow .infobox-full-data{border:0;padding:0 0.6em 0.2em 0.6em}.mw-parser-output .ib-country .mergedbottomrow .infobox-label,.mw-parser-output .ib-country .mergedbottomrow .infobox-data,.mw-parser-output .ib-country .mergedbottomrow .infobox-full-data{border-top:0;border-bottom:1px solid #a2a9b1;padding:0 0.6em 0.4em 0.6em}.mw-parser-output .ib-country .infobox-header{text-align:left}.mw-parser-output .ib-country .infobox-above{font-size:125%;line-height:1.2}.mw-parser-output .ib-country-names{padding-top:0.25em;font-weight:normal}.mw-parser-output .ib-country-name-style{display:inline}.mw-parser-output .ib-country .infobox-image{padding:0.5em 0}.mw-parser-output .ib-country-anthem{border-top:1px solid #a2a9b1;padding-top:0.5em;margin-top:0.5em}.mw-parser-output .ib-country-map-caption{position:relative;top:0.3em}.mw-parser-output .ib-country-largest,.mw-parser-output .ib-country-lang{font-weight:normal}.mw-parser-output .ib-country-ethnic,.mw-parser-output .ib-country-religion,.mw-parser-output .ib-country-sovereignty{font-weight:normal;display:inline}.mw-parser-output .ib-country-fake-li{text-indent:-0.9em;margin-left:1.2em;font-weight:normal}.mw-parser-output .ib-country-fake-li2{text-indent:0.5em;margin-left:1em;font-weight:normal}.mw-parser-output .ib-country-website{line-height:11pt}.mw-parser-output .ib-country-map-caption3{position:relative;top:0.3em}.mw-parser-output .ib-country-fn{text-align:left;margin:0 auto}.mw-parser-output .ib-country-fn-alpha{list-style-type:lower-alpha;margin-left:1em}.mw-parser-output .ib-country-fn-num{margin-left:1em} Roman Empire 27 BC \u2013 AD 395 .mw-parser-output .nobold{font-weight:normal} (unified) [ a ] AD 395 \u2013 476/480 ( Western ) AD 395\u20131453 ( Eastern ) .mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{} Roman Empire in AD 117 at its greatest territorial extent, at the time of Trajan 's death Vassal states [ 3 ] [ b ] Roman territorial evolution from the rise of the city-state of Rome to the fall of the Western Roman Empire Capital .mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0} Rome (27 BC \u2013 AD 476) [ c ] Constantinople (330\u20131453) [ d ] Common languages Official: initially Latin , increasingly Greek as well or instead [ 16 ] Other: Regional languages Religion Imperial cult -driven polytheism (until AD 380) Nicene Christianity ( officially from AD 380) Demonym Roman Government Autocracy \u2022 Emperor ( List ) Historical era Classical era to Late Middle Ages ( Timeline ) Area 25 BC [ 17 ] 2,750,000 km 2 (1,060,000 sq mi) AD 117 [ 17 ] [ 18 ] [ 19 ] 5,000,000 km 2 (1,900,000 sq mi) AD 390 [ 17 ] 3,400,000 km 2 (1,300,000 sq mi) Population \u2022 25 BC [ 20 ] 56,800,000 Currency Denarius , sestertius , [ e ] aureus , solidus , nomisma Preceded by Succeeded by Roman Republic Western Roman Empire Eastern Roman Empire The Roman Empire was a state that controlled the Mediterranean and much of Western Europe, Western Asia, and North Africa during the classical period . The Roman Republic had previously conquered most of these territories, which became ruled by emperors following triumvir Octavian 's rise to power and establishment of a Principate regime in 27 BC. By the 4th century AD the empire split into western and eastern halves. The Western Empire collapsed in 476 AD, while the Eastern Empire endured until the fall of Constantinople in 1453. By 100 BC, the city of Rome had expanded its rule from the Italian peninsula to most of the Mediterranean and beyond. However, it was severely destabilised by civil wars and political conflicts , which culminated in the victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the subsequent conquest of the Ptolemaic Kingdom in Egypt. In 27 BC, the Roman Senate granted Octavian overarching military power ( imperium ) and the new title of Augustus , marking his accession as the first Roman emperor . The vast Roman territories were organized into senatorial provinces, governed by proconsuls who were appointed by lot annually, and imperial provinces, which belonged to the emperor but were governed by legates . The first two centuries of the Empire saw a period of unprecedented stability and prosperity known as the Pax Romana ( literal translation</span>\"}]],\"parts\":[{\"template\":{\"target\":{\"wt\":\"Literal translation\",\"href\":\"./Template:Literal_translation\"},\"params\":{\"1\":{\"wt\":\"Roman Peace\"}},\"i\":0}}]}' id=\"mwbw\">lit. ' Roman Peace ' ). Rome reached its greatest territorial extent under Trajan ( reigned</span>\"}]]}'>r. 98\u2013117 AD ), but a period of increasing trouble and decline began under Commodus ( reigned</span>\"}]]}'>r. 180\u2013192 ). In the 3rd century, the Empire underwent a 49-year crisis that threatened its existence due to civil war, plagues and barbarian invasions . The Gallic and Palmyrene empires broke away from the state and a series of short-lived emperors led the Empire, which was later reunified under Aurelian ( reigned</span>\"}]]}'>r. 270\u2013275 ). The civil wars ended with the victory of Diocletian ( reigned</span>\"}]]}'>r. 284\u2013305 ), who set up two different imperial courts in the Greek East and Latin West . Constantine the Great ( reigned</span>\"}]]}'>r. 306\u2013337 ), the first Christian emperor , moved the imperial seat from Rome to Byzantium in 330, and renamed it Constantinople . The Migration Period , involving large invasions by Germanic peoples and by the Huns of Attila , led to the decline of the Western Roman Empire . With the fall of Ravenna to the Germanic Herulians and the deposition of Romulus Augustus in 476 by Odoacer , the Western Empire finally collapsed. The Byzantine (Eastern Roman) Empire survived for another millennium with Constantinople as its sole capital , until the city's fall in 1453. {{Cite book |last=Roy |first=Kaushik |title=Military Transition in Early Modern Asia, 1400\u20131750: Cavalry, Guns, Government and Ships |date=2014 |publisher=Bloomsbury Publishing |isbn=978-1-7809-3800-4 |series=Bloomsbury Studies in Military History |page=37 |quote=After the capture of Constantinople, the capital of the Byzantine Empire became the capital of the Ottoman Empire. The Osmanli Turks called their empire the Empire of Rum (Rome).}}</ref>\"}},\"i\":0}}]}'> [ f ] Due to the Empire's extent and endurance, its institutions and culture had a lasting influence on the development of language , religion , art , architecture , literature , philosophy , law , and forms of government across its territories. Latin evolved into the Romance languages while Medieval Greek became the language of the East. The Empire's adoption of Christianity resulted in the formation of medieval Christendom . Roman and Greek art had a profound impact on the Italian Renaissance . Rome's architectural tradition served as the basis for Romanesque , Renaissance , and Neoclassical architecture , influencing Islamic architecture . The rediscovery of classical science and technology (which formed the basis for Islamic science ) in medieval Europe contributed to the Scientific Renaissance and Scientific Revolution . Many modern legal systems, such as the Napoleonic Code , descend from Roman law. Rome's republican institutions have influenced the Italian city-state republics of the medieval period, the early United States , and modern democratic republics . History Main article: History of the Roman Empire For a chronological guide, see Timeline of Roman history . See also: Campaign history of the Roman military Animated overview of the Roman territorial history from the Republic until the fall of its last remnant (the Byzantine Empire ) in 1453 Transition from Republic to Empire Further information: Roman Republic and Roman Kingdom Augustus of Prima Porta Rome had begun expanding shortly after the founding of the Roman Republic in the 6th century BC, though not outside the Italian Peninsula until the 3rd century BC. The Republic was not a nation-state in the modern sense, but a network of self-ruled towns (with varying degrees of independence from the Senate ) and provinces administered by military commanders. It was governed by annually elected magistrates ( Roman consuls above all) in conjunction with the Senate. [ 22 ] The 1st century BC was a time of political and military upheaval, which ultimately led to rule by emperors. [ 23 ] [ 24 ] [ 25 ] The consuls' military power rested in the Roman legal concept of imperium , meaning \"command\" (typically in a military sense). [ 26 ] Occasionally, successful consuls or generals were given the honorary title imperator (commander); this is the origin of the word emperor , since this title was always bestowed to the early emperors. [ 27 ] {{Cite book |last1=Hornblower |first1=Simon |title=The Oxford Classical Dictionary |last2=Spawforth |first2=Antony |last3=Eidinow |first3=Esther |date=2012 |isbn=978-0-1995-4556-8 |pages=[https://books.google.com/books?id=bVWcAQAAQBAJ&pg=PA728 728]\u2013729 |chapter=Imperator |doi=10.1093/acrefore/9780199381135.013.3268 |chapter-url=https://doi.org/10.1093/acrefore/9780199381135.013.3268}}</ref> Both ''[[Caesar (title)|Caesar]]'' and ''[[Augustus (title)|Augustus]]'' evolved into formal titles, the former denoting the heir and the latter the monarch. In some languages, ''Caesar'' became the origin of the word \\\"[[emperor]]\\\", such as in German (''[[Kaiser]]'') and some Slavic languages (''[[Tsar]]'').\"}},\"i\":0}}]}'> [ g ] Rome suffered a long series of internal conflicts, conspiracies, and civil wars from the late second century BC, (see Crisis of the Roman Republic ) while greatly extending its power beyond Italy. In 44 BC Julius Caesar was briefly perpetual dictator before being assassinated by a faction that opposed his concentration of power. This faction was driven from Rome and defeated at the Battle of Philippi in 42 BC by Mark Antony and Caesar's adopted son Octavian . Antony and Octavian divided the Roman world between them, but this did not last long . Octavian's forces defeated those of Mark Antony and Cleopatra at the Battle of Actium in 31 BC. In 27 BC the Senate gave him the title Augustus (\"venerated\") and made him princeps (\"foremost\") with proconsular imperium , thus beginning the Principate , the first epoch of Roman imperial history. Although the republic stood in name, Augustus had all meaningful authority. [ 29 ] During his 40-year rule , a new constitutional order emerged so that, upon his death, Tiberius would succeed him as the new de facto monarch. [ 30 ] Pax Romana Main article: Pax Romana .mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}} The so-called \" Five Good Emperors \" of 96\u2013180 AD Nerva ( reigned</span>\"}]]}'>r. 96\u201398 ) Trajan ( reigned</span>\"}]]}'>r. 98\u2013117 ) Hadrian ( reigned</span>\"}]]}'>r. 117\u2013138 ) Antoninus Pius ( reigned</span>\"}]]}'>r. 138\u2013161 ) Marcus Aurelius ( reigned</span>\"}]]}'>r. 161\u2013180 ) The 200 years that began with Augustus's rule are traditionally regarded as the Pax Romana (\"Roman Peace\"). The cohesion of the empire was furthered by a degree of social stability and economic prosperity that Rome had never before experienced. Uprisings in the provinces were infrequent and put down \"mercilessly and swiftly\". [ 31 ] The success of Augustus in establishing principles of dynastic succession was limited by his outliving a number of talented potential heirs. The Julio-Claudian dynasty lasted for four more emperors\u2014 Tiberius , Caligula , Claudius , and Nero \u2014before it yielded in 69 AD to the strife-torn Year of the Four Emperors , from which Vespasian emerged as the victor. Vespasian became the founder of the brief Flavian dynasty , followed by the Nerva\u2013Antonine dynasty which produced the \" Five Good Emperors \": Nerva , Trajan , Hadrian , Antoninus Pius , and Marcus Aurelius . [ 32 ] Among the so-called \"Five Good Emperors\", Hadrian ( reigned</span>\"}]]}'>r. 117\u2013138 ) is particularly noted for consolidating the empire's frontiers and embarking on ambitious building projects throughout the provinces. [ 33 ] In Judaea, which had long been the center of Jewish national and religious life, his reign marked a decisive turning point. After earlier Jewish resistance to Roman rule, Hadrian visited the region in 129/130 AD and refounded Jerusalem as the Roman colony Aelia Capitolina, naming it after his family (Aelius) and the Capitoline Triad. [ 34 ] The refoundation overlaid the destroyed Jewish city with a new Roman urban plan, and included the construction of a Temple to Jupiter on the site of the former Jewish Temple. [ 35 ] Later tradition and archaeological evidence also indicate a Temple of Venus near the site of the Holy Sepulchre . [ 36 ] Hadrian's measures, combined with restrictions on Jewish practices, helped spark the Bar Kokhba Revolt (132\u2013135 AD). After crushing the uprising, Roman forces expelled most Jews from Jerusalem, barring their entry except on certain days, and rebuilt the city as a statement of imperial power and domination. [ 33 ] Most scholars consider Hadrianic Aelia to have been unwalled, with free-standing gate complexes (such as the northern gate beneath today's Damascus Gate) rather than a continuous defensive circuit. [ 37 ] Transition from classical to late antiquity Main articles: Later Roman Empire and Fall of the Western Roman Empire See also: Barbarian kingdoms and Byzantine Empire The Barbarian invasions consisted of the movement of (mainly) ancient Germanic peoples into Roman territory. Historically, this event marked the transition between classical antiquity and the Middle Ages . In the view of contemporary Greek historian Cassius Dio , the accession of Commodus in 180 marked the descent \"from a kingdom of gold to one of rust and iron\", [ 38 ] a comment which has led some historians, notably Edward Gibbon , to take Commodus' reign as the beginning of the Empire's decline . [ 39 ] [ 40 ] In 212, during the reign of Caracalla , Roman citizenship was granted to all freeborn inhabitants of the empire. The Severan dynasty was tumultuous; an emperor's reign was ended routinely by his murder or execution and, following its collapse, the Empire was engulfed by the Crisis of the Third Century , a period of invasions , civil strife , economic disorder , and plague . [ 41 ] In defining historical epochs , this crisis sometimes marks the transition from classical to late antiquity . Aurelian ( reigned</span>\"}]]}'>r. 270\u2013275 ) stabilised the empire militarily and Diocletian reorganised and restored much of it in 285. [ 42 ] Diocletian's reign brought the empire's most concerted effort against the perceived threat of Christianity , the \" Great Persecution \". [ 43 ] Diocletian divided the empire into four regions, each ruled by a separate tetrarch . [ 44 ] Confident that he fixed the disorder plaguing Rome, he abdicated along with his co-emperor, but the Tetrarchy collapsed shortly after . Order was eventually restored by Constantine the Great , who became the first emperor to convert to Christianity , and who established Constantinople as the new capital of the Eastern Empire. During the decades of the Constantinian and Valentinian dynasties, the empire was divided along an east\u2013west axis, with dual power centres in Constantinople and Rome. Julian , who under the influence of his adviser Mardonius attempted to restore Classical Roman and Hellenistic religion , only briefly interrupted the succession of Christian emperors. Theodosius I , the last emperor to rule over both East and West, died in 395 after making Christianity the state religion . [ 45 ] The Roman Empire by 476, noting western and eastern divisions The administrative divisions of the Roman Empire in 395 AD Fall in the West and survival in the East The Western Roman Empire began to disintegrate in the early 5th century. The Romans fought off all invaders, most famously Attila , [ 46 ] but the empire had assimilated so many Germanic peoples of dubious loyalty to Rome that the empire started to dismember itself. [ 47 ] Most chronologies place the end of the Western Roman Empire in 476, when Romulus Augustulus was forced to abdicate to the Germanic warlord Odoacer . [ 48 ] [ 49 ] [ 50 ] Odoacer ended the Western Empire by declaring Zeno sole emperor and placing himself as Zeno's nominal subordinate. In reality, Italy was ruled by Odoacer alone. [ 48 ] [ 49 ] [ 51 ] The Eastern Roman Empire, called the Byzantine Empire by later historians, continued until the reign of Constantine XI Palaiologos , the last Roman emperor. He died in battle in 1453 against Mehmed II and his Ottoman forces during the siege of Constantinople . Mehmed II adopted the title of caesar in an attempt to claim a connection to the former Empire. [ 52 ] [ 53 ] His claim was soon recognized by the Patriarchate of Constantinople , but not by European monarchs. Geography and demography Main articles: Demography of the Roman Empire and Borders of the Roman Empire Further information: Classical demography The Roman Empire was one of the largest in history, with contiguous territories throughout Europe, North Africa, and the Middle East. [ 54 ] The Latin phrase imperium sine fine (\"empire without end\" [ 55 ] ) expressed the ideology that neither time nor space limited the Empire. In Virgil 's Aeneid , limitless empire is said to be granted to the Romans by Jupiter . [ 56 ] This claim of universal dominion was renewed when the Empire came under Christian rule in the 4th century. {{Cite book |last=Mastrangelo |first=Marc |title=The Roman Self in Late Antiquity: Prudentius and the Poetics of the Soul |date=2008 |publisher=Johns Hopkins University Press |pages=73, 203}}</ref> [[St. Augustine]], however, distinguished between the secular and eternal \\\"Rome\\\" in ''[[De Civitate Dei|The City of God]]''. See also {{Citation |last=Fears |first=J. Rufus |chapter=The Cult of Jupiter and Roman Imperial Ideology |date=1981 |title=Aufstieg und Niedergang der r\u00f6mischen Welt |volume=II |issue=17.1 |author-link=J. Rufus Fears |page=136}}, on how Classical Roman ideology influenced Christian Imperial doctrine, {{Citation |last=Bang |first=Peter Fibiger |chapter=The King of Kings: Universal Hegemony, Imperial Power, and a New Comparative History of Rome |date=2011 |title=The Roman Empire in Context: Historical and Comparative Perspectives |publisher=John Wiley & Sons}} and the Greek concept of globalism (''[[ecumene|oikoum\u00e9n\u0113]]'').\"}},\"i\":0}}]}'> [ h ] In addition to annexing large regions, the Romans directly altered their geography, for example cutting down entire forests . [ 58 ] Roman expansion was mostly accomplished under the Republic , though parts of northern Europe were conquered in the 1st century, when Roman control in Europe, Africa, and Asia was strengthened. Under Augustus , a \"global map of the known world\" was displayed for the first time in public at Rome, coinciding with the creation of the most comprehensive political geography that survives from antiquity, the Geography of Strabo . [ 59 ] When Augustus died, the account of his achievements ( Res Gestae ) prominently featured the geographical cataloguing of the Empire. [ 60 ] Geography alongside meticulous written records were central concerns of Roman Imperial administration . [ 61 ] A segment of the ruins of Hadrian's Wall in northern England, overlooking Crag Lough The Empire reached its largest expanse under Trajan ( reigned</span>\"}]]}'>r. 98\u2013117 ), [ 62 ] encompassing 5 million km 2 . [ 17 ] [ 18 ] The traditional population estimate of 55\u201360 million inhabitants [ 63 ] accounted for between one-sixth and one-fourth of the world's total population [ 64 ] and made it the most populous unified political entity in the West until the mid-19th century. [ 65 ] 21st-century demographic studies have argued for a population peak from 70 million to more than 100 million . [ 66 ] Each of the three largest cities in the Empire\u2014Rome, Alexandria , and Antioch \u2014was almost twice the size of any European city at the beginning of the 17th century. [ 67 ] As the historian Christopher Kelly described it: .mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}} Then the empire stretched from Hadrian's Wall in drizzle-soaked northern England to the sun-baked banks of the Euphrates in Syria; from the great Rhine \u2013 Danube river system, which snaked across the fertile, flat lands of Europe from the Low Countries to the Black Sea , to the rich plains of the North African coast and the luxuriant gash of the Nile Valley in Egypt. The empire completely circled the Mediterranean ... referred to by its conquerors as mare nostrum \u2014'our sea'. [ 63 ] Roman cities in the Imperial period [ 68 ] Trajan's successor Hadrian adopted a policy of maintaining rather than expanding the empire. Borders ( fines ) were marked, and the frontiers ( limites ) patrolled. [ 62 ] The most heavily fortified borders were the most unstable. [ 24 ] Hadrian's Wall , which separated the Roman world from what was perceived as an ever-present barbarian threat, is the primary surviving monument of this effort. [ 69 ] In the eastern provinces, rural administration often relied on inscribed boundary stones to demarcate land and regulate taxation. [ 70 ] [ 71 ] Languages Main article: Languages of the Roman Empire See also: Jire\u010dek Line Latin and Greek were the main languages of the Empire, {{Harvp|Rochette|2012|pp=562\u2013563}}.</ref> In the east, Greek was always the dominant language, a leftover influence from the [[Hellenistic period]] that predates the Empire.{{Sfnp|Rochette|2018|p=108}}<ref>{{Cite book |last=Millar |first=Fergus |title=A Greek Roman Empire: Power and Belief under Theodosius II (408\u2013450) |date=2006 |publisher=University of California Press |isbn=0-5209-4141-1 |page=279 |author-link=Fergus Millar}}; {{Harvp|Treadgold|1997|pp=5\u20137}}</ref>\"}},\"i\":0}}]}'> [ i ] but the Empire was deliberately multilingual. [ 76 ] Andrew Wallace-Hadrill says \"The main desire of the Roman government was to make itself understood\". [ 77 ] At the start of the Empire, knowledge of Greek was useful to pass as educated nobility and knowledge of Latin was useful for a career in the military, government, or law. [ 78 ] Bilingual inscriptions indicate the everyday interpenetration of the two languages. [ 79 ] Latin and Greek's mutual linguistic and cultural influence is a complex topic. [ 80 ] Latin words incorporated into Greek were very common by the early imperial era, especially for military, administration, and trade and commerce matters. [ 81 ] Greek grammar, literature, poetry and philosophy shaped Latin language and culture. [ 82 ] [ 83 ] A 5th-century papyrus showing a parallel Latin-Greek text of a speech by Cicero [ 84 ] There was never a legal requirement for Latin in the Empire, but it represented a certain status. [ 85 ] High standards of Latin, Latinitas , started with the advent of Latin literature. [ 86 ] Due to the flexible language policy of the Empire, a natural competition of language emerged that spurred Latinitas , to defend Latin against the stronger cultural influence of Greek. [ 87 ] Over time Latin usage was used to project power and a higher social class. [ 88 ] [ 89 ] Most of the emperors were bilingual but had a preference for Latin in the public sphere for political reasons, a \"rule\" that first started during the Punic Wars . [ 90 ] Different emperors up until Justinian would attempt to require the use of Latin in various sections of the administration but there is no evidence that a linguistic imperialism existed during the early Empire. [ 91 ] After all freeborn inhabitants were universally enfranchised in 212 , many Roman citizens lacked a knowledge of Latin. [ 92 ] The wide use of Koine Greek was what enabled the spread of Christianity and reflects its role as the lingua franca of the Mediterranean during the time of the Empire. [ 93 ] Following Diocletian's reforms in the 3rd century AD, there was a decline in the knowledge of Greek in the west. [ 94 ] Spoken Latin later fragmented into the incipient romance languages in the 7th century AD following the collapse of the Empire's west. [ 95 ] The dominance of Latin and Greek among the literate elite obscures the continuity of other spoken languages within the Empire. [ 96 ] Latin, referred to in its spoken form as Vulgar Latin , gradually replaced Celtic and Italic languages . [ 97 ] [ 98 ] References to interpreters indicate the continuing use of local languages, particularly in Egypt with Coptic , and in military settings along the Rhine and Danube. Roman jurists also show a concern for local languages such as Punic , Gaulish , and Aramaic in assuring the correct understanding of laws and oaths. [ 99 ] In Africa , Libyco-Berber and Punic were used in inscriptions into the 2nd century. [ 96", "History of mathematics A proof from Euclid 's Elements ( c. 300 BC ), considered the most influential textbook of all time. 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.sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Part of a series on Mathematics History Index Areas Number theory Geometry Algebra Calculus and Analysis Discrete mathematics Logic Probability and Statistics Decision theory Relationship with sciences Physics Chemistry Geosciences Computation Biology Linguistics Economics Philosophy Education 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.mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e The history of mathematics deals with the origin of discoveries in mathematics and the mathematical methods and notation of the past . Before the modern age and worldwide spread of knowledge, written examples of new mathematical developments have come to light only in a few locales. From 3000 BC the Mesopotamian states of Sumer , Akkad and Assyria , followed closely by Ancient Egypt and the Levantine state of Ebla began using arithmetic , algebra and geometry for taxation , commerce , trade, and in astronomy , to record time and formulate calendars . The earliest mathematical texts available are from Mesopotamia and Egypt \u2013 Plimpton 322 ( Babylonian c. 2000 \u2013 1900 BC), [ 2 ] the Rhind Mathematical Papyrus ( Egyptian c. 1800 BC) [ 3 ] and the Moscow Mathematical Papyrus (Egyptian c. 1890 BC). All these texts mention the so-called Pythagorean triples , so, by inference, the Pythagorean theorem seems to be the most ancient and widespread mathematical development, after basic arithmetic and geometry. The study of mathematics as a \"demonstrative discipline\" began in the 6th century BC with the Pythagoreans , who coined the term \"mathematics\" from the ancient Greek \u03bc\u03ac\u03b8\u03b7\u03bc\u03b1 ( mathema ), meaning \"subject of instruction\". [ 4 ] Greek mathematics greatly refined the methods (especially through the introduction of deductive reasoning and mathematical rigor in proofs ) and expanded the subject matter of mathematics. [ 5 ] The ancient Romans used applied mathematics in surveying , structural engineering , mechanical engineering , bookkeeping , creation of lunar and solar calendars , and even arts and crafts . Chinese mathematics made early contributions, including a place value system and the first use of negative numbers . [ 6 ] [ 7 ] The Hindu\u2013Arabic numeral system and the rules for the use of its operations, in use throughout the world today, evolved over the course of the first millennium AD in India and were transmitted to the Western world via Islamic mathematics through the work of Khw\u0101rizm\u012b . [ 8 ] [ 9 ] Islamic mathematics, in turn, developed and expanded the mathematics known to these civilizations. [ 10 ] Contemporaneous with but independent of these traditions were the mathematics developed by the Maya civilization of Mexico and Central America , where the concept of zero was given a standard symbol in Maya numerals . Many Greek and Arabic texts on mathematics were translated into Latin from the 12th century, leading to further development of mathematics in Medieval Europe . From ancient times through the Middle Ages , periods of mathematical discovery were often followed by centuries of stagnation. [ 11 ] Beginning in Renaissance Italy in the 15th century, new mathematical developments, interacting with new scientific discoveries, were made at an increasing pace that continues through the present day. This includes the groundbreaking work of both Isaac Newton and Gottfried Wilhelm Leibniz in the development of infinitesimal calculus during the 17th century and subsequent discoveries of German mathematicians like Carl Friedrich Gauss and David Hilbert . Prehistoric The origins of mathematical thought lie in the concepts of number , patterns in nature , magnitude , and form . [ 12 ] Modern studies of animal cognition have shown that these concepts are not unique to humans. Such concepts would have been part of everyday life in hunter-gatherer societies. The idea of the \"number\" concept evolving gradually over time is supported by the existence of languages that preserve the distinction between \"one\", \"two\", and \"many\", but not of numbers larger than two. [ 12 ] The use of yarn by Neanderthals some 40,000 years ago at a site in Abri du Maras in the south of France suggests they knew basic concepts in mathematics. [ 13 ] [ 14 ] The Ishango bone , found near the headwaters of the Nile river (northeastern Congo ), may be more than 20,000 years old and consists of a series of marks carved in three columns running the length of the bone. Common interpretations are that the Ishango bone shows either a tally of the earliest known demonstration of sequences of prime numbers [ 15 ] or a six-month lunar calendar. [ 16 ] [ 17 ] Peter Rudman argues that the development of the concept of prime numbers could only have come about after the concept of division, which he dates to after 10,000 BC, with prime numbers probably not being understood until about 500 BC. He also writes that \"no attempt has been made to explain why a tally of something should exhibit multiples of two, prime numbers between 10 and 20, and some numbers that are almost multiples of 10.\" [ 18 ] The Ishango bone, according to scholar Alexander Marshack , may have influenced the later development of mathematics in Egypt as, like some entries on the Ishango bone, Egyptian arithmetic also made use of multiplication by 2; this however, is disputed. [ 19 ] Predynastic Egyptians of the 5th millennium BC pictorially represented geometric designs. It has been claimed that megalithic monuments in England and Scotland , dating from the 3rd millennium BC, incorporate geometric ideas such as circles , ellipses , and Pythagorean triples in their design. [ 20 ] All of the above are disputed, however, and the currently oldest undisputed mathematical documents are from Babylonian and dynastic Egyptian sources. [ 21 ] Babylonian .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} Main article: Babylonian mathematics See also: Plimpton 322 Babylonian mathematics refers to any mathematics of the peoples of Mesopotamia (modern Iraq ) from the days of the early Sumerians through the Hellenistic period , almost to the dawn of Christianity . [ 22 ] The majority of Babylonian mathematical work comes from two widely separated periods: The first few hundred years of the second millennium BC (Old Babylonian period) and the last few centuries of the first millennium BC ( Seleucid period). [ 23 ] It is named Babylonian mathematics due to the central role of Babylon as a place of study. Geometry problem on a clay tablet belonging to a school for scribes; Susa , first half of the 2nd millennium BC In contrast to the sparsity of sources in Egyptian mathematics , knowledge of Babylonian mathematics is derived from more than 400 clay tablets unearthed since the 1850s. [ 24 ] Written in Cuneiform script , tablets were inscribed whilst the clay was moist, and baked hard in an oven or by the heat of the sun. Some of these appear to be graded homework. [ 25 ] The earliest evidence of written mathematics dates back to the ancient Sumerians , who built the earliest civilization in Mesopotamia. They developed a complex system of metrology from 3000 BC that was chiefly concerned with administrative/financial counting, such as grain allotments, workers, weights of silver, or even liquids, among other things. [ 26 ] From around 2500 BC onward, the Sumerians wrote multiplication tables on clay tablets and dealt with geometrical exercises and division problems. The earliest traces of the Babylonian numerals also date back to this period. [ 27 ] The Babylonian mathematical tablet Plimpton 322 , dated to 1800 BC. Babylonian mathematics was written using a sexagesimal (base-60) numeral system . [ 24 ] From this derives the modern-day usage of 60 seconds in a minute, 60 minutes in an hour, and 360 (60 \u00d7 6) degrees in a circle, as well as the use of seconds and minutes of arc to denote fractions of a degree. It is thought the sexagesimal system was initially used by Sumerian scribes because 60 can be evenly divided by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30, [ 24 ] and for scribes (doling out the aforementioned grain allotments, recording weights of silver, etc.) being able to easily calculate by hand was essential, and so a sexagesimal system is pragmatically easier to calculate by hand with; however, there is the possibility that using a sexagesimal system was an ethno-linguistic phenomenon (that might not ever be known), and not a mathematical/practical decision. [ 28 ] Also, unlike the Egyptians, Greeks, and Romans, the Babylonians had a place-value system, where digits written in the left column represented larger values, much as in the decimal system. The power of the Babylonian notational system lay in that it could be used to represent fractions as easily as whole numbers; thus, multiplying two numbers that contained fractions was no different from multiplying integers, similar to modern notation. The notational system of the Babylonians was the best of any civilization until the Renaissance , and its power allowed it to achieve remarkable computational accuracy; for example, the Babylonian tablet YBC 7289 gives an approximation of \u221a 2 accurate to five decimal places. [ 29 ] The Babylonians lacked, however, an equivalent of the decimal point, and so the place value of a symbol often had to be inferred from the context. [ 23 ] By the Seleucid period, the Babylonians had developed a zero symbol as a placeholder for empty positions; however, it was only used for intermediate positions. [ 23 ] This zero sign does not appear in terminal positions; thus, the Babylonians came close but did not develop a true place value system. [ 23 ] Other topics covered by Babylonian mathematics include fractions, algebra, quadratic and cubic equations, and the calculation of regular numbers and their reciprocal pairs . [ 30 ] The tablets also include multiplication tables and methods for solving linear , quadratic equations , and cubic equations , a remarkable achievement for the time. [ 31 ] Tablets from the Old Babylonian period also contain the earliest known statement of the Pythagorean theorem . [ 32 ] However, as with Egyptian mathematics, Babylonian mathematics shows no awareness of the difference between exact and approximate solutions, or the solvability of a problem, and most importantly, no explicit statement of the need for proofs or logical principles. [ 25 ] Egyptian Main article: Egyptian mathematics Image of Problem 14 from the Moscow Mathematical Papyrus . The problem includes a diagram indicating the dimensions of the truncated pyramid. Egyptian mathematics refers to mathematics written in the Egyptian language . From the Hellenistic period , Greek replaced Egyptian as the written language of Egyptian scholars. Archaeological evidence has suggested that the Ancient Egyptian counting system had origins in Sub-Saharan Africa . [ 33 ] Also, fractal geometry designs which are widespread among Sub-Saharan African cultures are also found in Egyptian architecture and cosmological signs. [ 34 ] Megalithic structures located in Nabta Playa , Upper Egypt featured astronomy , calendar arrangements in alignment with the heliacal rising of Sirius and supported calibration the yearly calendar for the annual Nile flood. [ 35 ] The most extensive Egyptian mathematical text is the Rhind papyrus (sometimes also called the Ahmes Papyrus after its author), dated to c. 1650 BC but likely a copy of an older document from the Middle Kingdom of about 2000\u20131800 BC. [ 36 ] It is an instruction manual for students in arithmetic and geometry. In addition to giving area formulas and methods for multiplication, division and working with unit fractions, it also contains evidence of other mathematical knowledge, [ 37 ] including composite and prime numbers ; arithmetic , geometric and harmonic means ; and simplistic understandings of both the Sieve of Eratosthenes and perfect number theory (namely, that of the number 6). [ 38 ] It also shows how to solve first order linear equations [ 39 ] as well as arithmetic and geometric series . [ 40 ] Another significant Egyptian mathematical text is the Moscow papyrus , also from the Middle Kingdom period, dated to c. 1890 BC. [ 41 ] It consists of what are today called word problems or story problems , which were apparently intended as entertainment. One problem is considered to be of particular importance because it gives a method for finding the volume of a frustum (truncated pyramid). Finally, the Berlin Papyrus 6619 (c. 1800 BC) shows that ancient Egyptians could solve a second-order algebraic equation . [ 42 ] Greek Main article: Ancient Greek mathematics The Pythagorean theorem . The Pythagoreans are generally credited with the first proof of the theorem. Greek mathematics refers to the mathematics written in the Greek language from the time of Thales of Miletus (~600 BC) to the closure of the Academy of Athens in 529 AD. [ 43 ] Greek mathematicians lived in cities spread over the entire Eastern Mediterranean, from Italy to North Africa, but were united by culture and language. Greek mathematics of the period following Alexander the Great is sometimes called Hellenistic mathematics. [ 44 ] Greek mathematics was much more sophisticated than the mathematics that had been developed by earlier cultures. All surviving records of pre-Greek mathematics show the use of inductive reasoning , that is, repeated observations used to establish rules of thumb. Greek mathematicians, by contrast, used deductive reasoning . The Greeks used logic to derive conclusions from definitions and axioms, and used mathematical rigor to prove them. [ 45 ] Greek mathematics is thought to have begun with Thales of Miletus (c. 624\u2013c.546 BC) and Pythagoras of Samos (c. 582\u2013c. 507 BC). Although the extent of the influence is disputed, they were probably inspired by Egyptian and Babylonian mathematics . According to legend, Pythagoras traveled to Egypt to learn mathematics, geometry, and astronomy from Egyptian priests. Thales used geometry to solve problems such as calculating the height of pyramids and the distance of ships from the shore. He is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales' Theorem . As a result, he has been hailed as the first true mathematician and the first known individual to whom a mathematical discovery has been attributed. [ 46 ] Pythagoras established the Pythagorean School , whose doctrine it was that mathematics ruled the universe and whose motto was \"All is number\". [ 47 ] It was the Pythagoreans who coined the term \"mathematics\", and with whom the study of mathematics for its own sake begins. The Pythagoreans are credited with the first proof of the Pythagorean theorem , [ 48 ] though the statement of the theorem has a long history, and with the proof of the existence of irrational numbers . [ 49 ] [ 50 ] Although he was preceded by the Babylonians , Indians and the Chinese , [ 51 ] the Neopythagorean mathematician Nicomachus (60\u2013120 AD) provided one of the earliest Greco-Roman multiplication tables , whereas the oldest extant Greek multiplication table is found on a wax tablet dated to the 1st century AD (now found in the British Museum ). [ 52 ] The association of the Neopythagoreans with the Western invention of the multiplication table is evident in its later Medieval name: the mensa Pythagorica . [ 53 ] Plato (428/427 BC \u2013 348/347 BC) is important in the history of mathematics for inspiring and guiding others. [ 54 ] His Platonic Academy , in Athens , became the mathematical center of the world in the 4th century BC, and it was from this school that the leading mathematicians of the day, such as Eudoxus of Cnidus (c. 390 - c. 340 BC), came. [ 55 ] Plato also discussed the foundations of mathematics, [ 56 ] clarified some of the definitions (e.g. that of a line as \"breadthless length\"). Eudoxus developed the method of exhaustion , a precursor of modern integration [ 57 ] and a theory of ratios that avoided the problem of incommensurable magnitudes . [ 58 ] The former allowed the calculations of areas and volumes of curvilinear figures, [ 59 ] while the latter enabled subsequent geometers to make significant advances in geometry. Though he made no specific technical mathematical discoveries, Aristotle (384\u2013 c. 322 BC ) contributed significantly to the development of mathematics by laying the foundations of logic . [ 60 ] One of the oldest surviving fragments of Euclid's Elements , found at Oxyrhynchus and dated to circa AD 100. The diagram accompanies Book II, Proposition 5. [ 61 ] In the 3rd century BC, the premier center of mathematical education and research was the Musaeum of Alexandria . [ 62 ] It was there that Euclid ( c. 300 BC ) taught, and wrote the Elements , widely considered the most successful and influential textbook of all time. [ 1 ] The Elements introduced mathematical rigor through the axiomatic method and is the earliest example of the format still used in mathematics today, that of definition, axiom, theorem, and proof. Although most of the contents of the Elements were already known, Euclid arranged them into a single, coherent logical framework. [ 63 ] The Elements was known to all educated people in the West up through the middle of the 20th century and its contents are still taught in geometry classes today. [ 64 ] In addition to the familiar theorems of Euclidean geometry , the Elements was meant as an introductory textbook to all mathematical subjects of the time, such as number theory , algebra and solid geometry , [ 63 ] including proofs that the square root of two is irrational and that there are infinitely many prime numbers. Euclid also wrote extensively on other subjects, such as conic sections , optics , spherical geometry , and mechanics, but only half of his writings survive. [ 65 ] Archimedes used the method of exhaustion to approximate the value of pi . Archimedes ( c. 287 \u2013212 BC) of Syracuse , widely considered the greatest mathematician of antiquity, [ 66 ] used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series , in a manner not too dissimilar from modern calculus. [ 67 ] He also showed one could use the method of exhaustion to calculate the value of \u03c0 with as much precision as desired, and obtained the most accurate value of \u03c0 then known, 3+ .mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px} \u2060 10 / 71 \u2060 < \u03c0 < 3+ \u2060 10 / 70 \u2060 . [ 68 ] He also studied the spiral bearing his name, obtained formulas for the volumes of surfaces of revolution (paraboloid, ellipsoid, hyperboloid), [ 67 ] and an ingenious method of exponentiation for expressing very large numbers. [ 69 ] While he is also known for his contributions to physics and several advanced mechanical devices, Archimedes himself placed far greater value on the products of his thought and general mathematical principles. [ 70 ] He regarded as his greatest achievement his finding of the surface area and volume of a sphere, which he obtained by proving these are 2/3 the surface area and volume of a cylinder circumscribing the sphere. [ 71 ] Apollonius of Perga made significant advances in the study of conic sections . Apollonius of Perga ( c. 262 \u2013190 BC) made significant advances to the study of conic sections , showing that one can obtain all three varieties of conic section by varying the angle of the plane that cuts a double-napped cone. [ 72 ] He also coined the terminology in use today for conic sections, namely parabola (\"place beside\" or \"comparison\"), \"ellipse\" (\"deficiency\"), and \"hyperbola\" (\"a throw beyond\"). [ 73 ] His work Conics is one of the best known and preserved mathematical works from antiquity, and in it he derives many theorems concerning conic sections that would prove invaluable to later mathematicians and astronomers studying planetary motion, such as Isaac Newton. [ 74 ] While neither Apollonius nor any other Greek mathematicians made the leap to coordinate geometry, Apollonius' treatment of curves is in some ways similar to the modern treatment, and some of his work seems to anticipate the development of analytical geometry by Descartes some 1800 years later. [ 75 ] Around the same time, Eratosthenes of Cyrene ( c. 276 \u2013194 BC) devised the Sieve of Eratosthenes for finding prime numbers . [ 76 ] The 3rd century BC is generally regarded as the \"Golden Age\" of Greek mathematics, with advances in pure mathematics henceforth in relative decline. [ 77 ] Nevertheless, in the centuries that followed significant advances were made in applied mathematics, most notably trigonometry , largely to address the needs of astronomers. [ 77 ] Hipparchus of Nicaea ( c. 190 \u2013120 BC) is considered the founder of trigonometry for compiling the first known trigonometric table, and to him is also due the systematic use of the 360 degree circle. [ 78 ] Heron of Alexandria ( c. 10 \u201370 AD) is credited with Heron's formula for finding the area of a scalene triangle and with being the first to recognize the possibility of negative numbers possessing square roots. [ 79 ] Menelaus of Alexandria ( c. 100 AD ) pioneered spherical trigonometry through Menelaus' theorem . [ 80 ] The most complete and influential trigonometric work of antiquity is the Almagest of Ptolemy ( c. AD 90 \u2013168), a landmark astronomical treatise whose trigonometric tables would be used by astronomers for the next thousand years. [ 81 ] Ptolemy is also credited with Ptolemy's theorem for deriving trigonometric quantities, and the most accurate value of \u03c0 outside of China until the medieval period, 3.1416. [ 82 ] Title page of the 1621 edition of Diophantus' Arithmetica , translated into Latin by Claude Gaspard Bachet de M\u00e9ziriac . Following a period of stagnation after Ptolemy, the period between 250 and 350 AD is sometimes referred to as the \"Silver Age\" of Greek mathematics. [ 83 ] During this period, Diophantus made significant advances in algebra, particularly indeterminate analysis , which is also known as \"Diophantine analysis\". [ 84 ] The study of Diophantine equations and Diophantine approximations is a significant area of research to this day. His main work was the Arithmetica , a collection of 150 algebraic problems dealing with exact solutions to determinate and indeterminate equations . [ 85 ] The Arithmetica had a significant influence on later mathematicians, such as Pierre de Fermat , who arrived at his famous Last Theorem after trying to generalize a problem he had read in the Arithmetica (that of dividing a square into two squares). [ 86 ] Diophantus also made significant advances in notation, the Arithmetica being the first instance of algebraic symbolism and syncopation. [ 85 ] The Hagia Sophia was designed by mathematicians Anthemius of Tralles and Isidore of Miletus . Among the last great Greek mathematicians is Pappus of Alexandria (4th century AD). He is known for his hexagon theorem and centroid theorem , as well as the Pappus configuration and Pappus graph . His Collection is a major source of knowledge on Greek mathematics as most of it has survived. [ 87 ] Pappus is considered the last major innovator in Greek mathematics, with subsequent work consisting mostly of commentaries on earlier work. The first woman mathematician recorded was Hypatia of Alexandria (AD 350\u2013415), who wrote many works on applied mathematics. Because of a political dispute, the Christian community in Alexandria had her stripped publicly and executed. [ 88 ] Her death is sometimes taken as the end of the era of the Alexandrian Greek mathematics, although work did continue in Athens for another century with figures such as Proclus , Simplicius and Eutocius . [ 89 ] Although Proclus and Simplicius were more philosophers than mathematicians, their commentaries on earlier works are valuable sources on Greek mathematics. The closure of the neo-Platonic Academy of Athens by the emperor Justinian in 529 AD is traditionally held as marking the end of the era of Greek mathematics, although the Greek tradition continued unbroken in the Byzantine empire with mathematicians such as Anthemius of Tralles and Isidore of Miletus , the architects of the Hagia Sophia . [ 90 ] Nevertheless, Byzantine mathematics consisted mostly of commentaries, with little in the way of innovation, and the centers of mathematical innovation were to be found elsewhere by this time. [ 91 ] Roman Further information: Roman abacus and Roman numerals Equipment used by an ancient Roman land surveyor ( gromatici ), found at the site of Aquincum , modern Budapest , Hungary Although ethnic Greek mathematicians continued under the rule of the late Roman Republic and subsequent Roman Empire , there were no noteworthy native Latin mathematicians in comparison. [ 92 ] [ 93 ] Ancient Romans such as Cicero (106\u201343 BC), an influential Roman statesman who studied mathematics in Greece, believed that Roman surveyors and calculators were far more interested in applied mathematics than the theoretical mathematics and geometry that were prized by the Greeks. [ 94 ] It is unclear if the Romans first derived their numerical system directly from the Greek precedent or from Etruscan numerals used by the Etruscan civilization centered in what is now Tuscany , central Italy . [ 95 ] Using calculation, Romans were adept at both instigating and detecting financial fraud , as well as managing taxes for the treasury . [ 96 ] Siculus Flaccus , one of the Roman gromatici (i.e. land surveyor), wrote the Categories of Fields , which aided Roman surveyors in measuring the surface areas of allotted lands and territories. [ 97 ] Aside from managing trade and taxes, the Romans also regularly applied mathematics to solve problems in engineering , including the erection of architecture such as bridges , road-building , and preparation for military campaigns . [ 98 ] Arts and crafts such as Roman mosaics , inspired by previous Greek designs , created illusionist geometric patterns and rich, detailed scenes that required precise measurements for each tessera tile, the opus tessellatum pieces on average measuring eight millimeters square and the finer opus vermiculatum pieces having an average surface of four millimeters square. [ 99 ] [ 100 ] The creation of the Roman calendar also necessitated basic mathematics. The first calendar allegedly dates back to 8th century BC during the Roman Kingdom and included 356 days plus a leap year every other year. [ 101 ] In contrast, the lunar calendar of the Republican era contained 355 days, roughly ten-and-one-fourth days shorter than the solar year , a discrepancy that was solved by adding an extra month into the calendar after the 23rd of February. [ 102 ] This calendar was supplanted by the Julian calendar , a solar calendar organized by Julius Caesar (100\u201344 BC) and devised by Sosigenes of Alexandria to include a leap day every four years in a 365-day cycle. [ 103 ] This calendar, which contained an error of 11 minutes and 14 seconds, was later corrected by the Gregorian calendar organized by Pope Gregory XIII ( reigned</span>\"}]]}'>r. 1572\u20131585 ), virtually the same solar calendar used in modern times as the international standard calendar. [ 104 ] At roughly the same time, the Han Chinese and the Romans both invented the wheeled odometer device for measuring distances traveled, the Roman model first described by the Roman civil engineer and architect Vitruvius ( c. 80 BC \u2013 c. 15 BC ). [ 105 ] The device was used at least until the reign of emperor Commodus ( reigned</span>\"}]]}'>r. 177 \u2013 192 AD ), but its design seems to have been lost until experiments were made during the 15th century in Western Europe. [ 106 ] Perhaps relying on similar gear-work and technology found in the Antikythera mechanism , the odometer of Vitruvius featured chariot wheels measuring 4 feet (1.2 m) in diameter turning four-hundred times in one Roman mile (roughly 4590 ft/1400 m). With each revolution, a pin-and-axle device engaged a 400-tooth cogwheel that turned a second gear responsible for dropping pebbles into a box, each pebble representing one mile traversed. [ 107 ] Chinese Main article: Chinese", "Photosynthesis Biological process to convert light into chemical energy <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected due to vandalism\\\" id=\\\"mwBg\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwBw\\\"/></a></span>\"}' id=\"mwCA\"/> Schematic of photosynthesis in plants. The carbohydrates produced are stored in or used by the plant. Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation . Dark red and blue-green indicate regions of high photosynthetic activity in the ocean and on land, respectively. Photosynthesis ( / \u02cc f o\u028a t \u0259 \u02c8 s \u026a n \u03b8 \u0259 s \u026a s / FOH -t\u0259- SINTH -\u0259-sis ) [ 1 ] is a system of biological processes by which photopigment -bearing autotrophic organisms , such as most plants , algae and cyanobacteria , convert light energy \u2014 typically from sunlight \u2014 into the chemical energy necessary to fuel their metabolism . The term photosynthesis usually refers to oxygenic photosynthesis , a process that releases oxygen as a byproduct of water splitting . Photosynthetic organisms store the converted chemical energy within the bonds of intracellular organic compounds (complex compounds containing carbon ), typically carbohydrates like sugars (mainly glucose , fructose and sucrose ), starches , phytoglycogen and cellulose . When needing to use this stored energy, an organism's cells then metabolize the organic compounds through cellular respiration . Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere , and it supplies most of the biological energy necessary for complex life on Earth . [ 2 ] Some organisms also perform anoxygenic photosynthesis , which does not produce oxygen. Some bacteria (e.g. purple bacteria ) use bacteriochlorophyll to split hydrogen sulfide as a reductant instead of water , releasing sulfur instead of oxygen, which was a dominant form of photosynthesis in the euxinic Canfield oceans during the Boring Billion . [ 3 ] [ 4 ] Archaea such as Halobacterium also perform a type of non- carbon-fixing anoxygenic photosynthesis, where the simpler photopigment retinal and its microbial rhodopsin derivatives are used to absorb green light and produce a proton ( hydron ) gradient across the cell membrane , and the subsequent ion movement powers transmembrane proton pumps to directly synthesize adenosine triphosphate (ATP), the \"energy currency\" of cells. Such archaeal photosynthesis might have been the earliest form of photosynthesis that evolved on Earth, as far back as the Paleoarchean , preceding that of cyanobacteria (see Purple Earth hypothesis ). [ 5 ] While the details may differ between species , the process always begins when light energy is absorbed by the reaction centers , proteins that contain photosynthetic pigments or chromophores . In plants, these pigments are chlorophylls (a porphyrin derivative that absorbs the red and blue spectra of light, thus reflecting green) held inside chloroplasts , abundant in leaf cells. In cyanobacteria, they are embedded in the plasma membrane . In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting of water is used in the creation of two important molecules that participate in energetic processes: reduced nicotinamide adenine dinucleotide phosphate (NADPH) and ATP. In plants, algae , and cyanobacteria , sugars are synthesized by a subsequent sequence of light-independent reactions called the Calvin cycle . In this process, atmospheric carbon dioxide is incorporated into already existing organic compounds, such as ribulose bisphosphate (RuBP). [ 6 ] Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are then reduced and removed to form further carbohydrates, such as glucose . In other bacteria, different mechanisms like the reverse Krebs cycle are used to achieve the same end. The first photosynthetic organisms probably evolved early in the evolutionary history of life using reducing agents such as hydrogen or hydrogen sulfide, rather than water, as sources of electrons. [ 7 ] Cyanobacteria appeared later; the excess oxygen they produced contributed directly to the oxygenation of the Earth , [ 8 ] which rendered the evolution of complex life possible. The average rate of energy captured by global photosynthesis is approximately 130 terawatts , [ 9 ] [ 10 ] [ 11 ] which is about eight times the total power consumption of human civilization . [ 12 ] Photosynthetic organisms also convert around 100\u2013115 billion tons (91\u2013104 Pg petagrams , or billions of metric tons), of carbon into biomass per year. [ 13 ] [ 14 ] Photosynthesis was discovered in 1779 by Jan Ingenhousz who showed that plants need light, not just soil and water. Overview .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} Main article: Biological carbon fixation Photosynthesis changes sunlight into chemical energy, splits water to liberate O 2 , and fixes CO 2 into sugar. Most photosynthetic organisms are photoautotrophs , which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis; photoheterotrophs use organic compounds, rather than carbon dioxide, as a source of carbon. [ 2 ] In plants , algae , and cyanobacteria , photosynthesis releases oxygen. This oxygenic photosynthesis is by far the most common type of photosynthesis used by living organisms. Some shade-loving plants (sciophytes) produce such low levels of oxygen during photosynthesis that they use all of it themselves instead of releasing it to the atmosphere. [ 15 ] Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of anoxygenic photosynthesis , used mostly by bacteria, which consume carbon dioxide but do not release oxygen or which produce elemental sulfur instead of molecular oxygen. [ 16 ] [ 17 ] Carbon dioxide is converted into sugars in a process called carbon fixation ; photosynthesis captures energy from sunlight to convert carbon dioxide into carbohydrates . Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration : while photosynthesis is a process of reduction of carbon dioxide to carbohydrates, cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide. Nutrients used in cellular respiration include carbohydrates, amino acids and fatty acids. These nutrients are oxidized to produce carbon dioxide and water, and to release chemical energy to drive the organism's metabolism . Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments (cellular respiration in mitochondria ). [ 18 ] [ 19 ] The general equation for photosynthesis as first proposed by Cornelis van Niel is: [ 20 ] dioxide\"},\"2\":{\"wt\":\"CO<sub>2</sub>\"}},\"i\":0}}]}' id=\"mw-A\"> CO 2 carbon dioxide + 2</sub>A\"}},\"i\":0}}]}' id=\"mw-Q\"> 2H 2 A electron donor + photons light energy \u2192 2</sub>O]\"}},\"i\":0}}]}' id=\"mw-w\"> [CH 2 O] carbohydrate + electron<br/>donor\"},\"2\":{\"wt\":\"2A\"}},\"i\":0}}]}' id=\"mw_A\"> 2A oxidized electron donor + 2</sub>O\"}},\"i\":0}}]}' id=\"mw_Q\"> H 2 O water Since water is used as the electron donor in oxygenic photosynthesis, the equation for this process is: dioxide\"},\"2\":{\"wt\":\"CO<sub>2</sub>\"}},\"i\":0}}]}' id=\"mwAQE\"> CO 2 carbon dioxide + 2</sub>O\"}},\"i\":0}}]}' id=\"mwAQI\"> 2H 2 O water + photons light energy \u2192 2</sub>O]\"}},\"i\":0}}]}' id=\"mwAQQ\"> [CH 2 O] carbohydrate + 2</sub>\"}},\"i\":0}}]}' id=\"mwAQU\"> O 2 oxygen + 2</sub>O\"}},\"i\":0}}]}' id=\"mwAQY\"> H 2 O water This equation emphasizes that water is both a reactant in the light-dependent reaction and a product of the light-independent reaction , but canceling n water molecules from each side gives the net equation: dioxide\"},\"2\":{\"wt\":\"CO<sub>2</sub>\"}},\"i\":0}}]}' id=\"mwAQ0\"> CO 2 carbon dioxide + 2</sub>O\"}},\"i\":0}}]}' id=\"mwAQ4\"> H 2 O water + photons light energy \u2192 2</sub>O]\"}},\"i\":0}}]}' id=\"mwARA\"> [CH 2 O] carbohydrate + 2</sub>\"}},\"i\":0}}]}' id=\"mwARE\"> O 2 oxygen Other processes substitute other compounds (such as arsenite ) for water in the electron-supply role; for example some microbes use sunlight to oxidize arsenite to arsenate : [ 21 ] The equation for this reaction is: dioxide\"},\"2\":{\"wt\":\"CO<sub>2</sub>\"}},\"i\":0}}]}' id=\"mwARw\"> CO 2 carbon dioxide + arsenite\"},\"2\":{\"wt\":\"(AsO{{su|b=3|p=3\u2212}})\"}},\"i\":0}}]}' id=\"mwAR0\"> (AsO 3\u2212 3 ) arsenite + photons light energy \u2192 arsenate\"},\"2\":{\"wt\":\"(AsO{{su|b=4|p=3\u2212}})\"}},\"i\":0}}]}' id=\"mwAR8\"> (AsO 3\u2212 4 ) arsenate + monoxide\"},\"2\":{\"wt\":\"CO\"}},\"i\":0}}]}' id=\"mwASA\"> CO carbon monoxide (used to build other compounds in subsequent reactions) [ 22 ] Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP . During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide. Most organisms that use oxygenic photosynthesis use visible light for the light-dependent reactions, although at least three use shortwave infrared or, more specifically, far-red radiation. [ 23 ] Some organisms employ even more radical variants of photosynthesis. Some archaea use a simpler method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump. This produces a proton gradient more directly, which is then converted to chemical energy. The process does not involve carbon dioxide fixation and does not release oxygen, and seems to have evolved separately from the more common types of photosynthesis. [ 24 ] Photosynthetic membranes and organelles Main articles: Chloroplast and Thylakoid Chloroplast ultrastructure : outer membrane intermembrane space inner membrane (1+2+3: envelope) stroma (aqueous fluid) thylakoid lumen (inside of thylakoid) thylakoid membrane granum (stack of thylakoids) thylakoid (lamella) starch ribosome plastidial DNA plastoglobule (drop of lipids) In photosynthetic bacteria, the proteins that gather light for photosynthesis are embedded in cell membranes . In its simplest form, this involves the membrane surrounding the cell itself. [ 25 ] However, the membrane may be tightly folded into cylindrical sheets called thylakoids , [ 26 ] or bunched up into round vesicles called intracytoplasmic membranes . [ 27 ] These structures can fill most of the interior of a cell, giving the membrane a very large surface area and therefore increasing the amount of light that the bacteria can absorb. [ 26 ] In plants and algae, photosynthesis takes place in organelles called chloroplasts . A typical plant cell contains about 10 to 100 chloroplasts. The chloroplast is enclosed by a membrane. This membrane is composed of a phospholipid inner membrane, a phospholipid outer membrane, and an intermembrane space. Enclosed by the membrane is an aqueous fluid called the stroma. Embedded within the stroma are stacks of thylakoids (grana), which are the site of photosynthesis. The thylakoids appear as flattened disks. The thylakoid itself is enclosed by the thylakoid membrane, and within the enclosed volume is a lumen or thylakoid space. Embedded in the thylakoid membrane are integral and peripheral membrane protein complexes of the photosynthetic system. Plants absorb light primarily using the pigment chlorophyll . The green part of the light spectrum is not absorbed but is reflected, which is the reason that most plants have a green color. Besides chlorophyll, plants also use pigments such as carotenes and xanthophylls . [ 28 ] Algae also use chlorophyll, but various other pigments are present, such as phycocyanin , carotenes , and xanthophylls in green algae , phycoerythrin in red algae (rhodophytes) and fucoxanthin in brown algae and diatoms resulting in a wide variety of colors. These pigments are embedded in plants and algae in complexes called antenna proteins. In such proteins, the pigments are arranged to work together. Such a combination of proteins is also called a light-harvesting complex . [ 29 ] Although all cells in the green parts of a plant have chloroplasts, the majority of those are found in specially adapted structures called leaves . Certain species adapted to conditions of strong sunlight and aridity , such as many Euphorbia and cactus species, have their main photosynthetic organs in their stems. The cells in the interior tissues of a leaf, called the mesophyll , can contain between 450,000 and 800,000 chloroplasts for every square millimeter of leaf. The surface of the leaf is coated with a water-resistant waxy cuticle that protects the leaf from excessive evaporation of water and decreases the absorption of ultraviolet or blue light to minimize heating . The transparent epidermis layer allows light to pass through to the palisade mesophyll cells where most of the photosynthesis takes place. Light-dependent reactions Main article: Light-dependent reactions Light-dependent reactions of photosynthesis at the thylakoid membrane In the light-dependent reactions , one molecule of the pigment chlorophyll absorbs one photon and loses one electron . This electron is taken up by a modified form of chlorophyll called pheophytin , which passes the electron to a quinone molecule, starting the flow of electrons down an electron transport chain that leads to the ultimate reduction of NADP to NADPH . In addition, this creates a proton gradient (energy gradient) across the chloroplast membrane , which is used by ATP synthase in the synthesis of ATP . The chlorophyll molecule ultimately regains the electron it lost when a water molecule is split in a process called photolysis , which releases oxygen . The overall equation for the light-dependent reactions under the conditions of non-cyclic electron flow in green plants is: [ 30 ] 2</sub>O + 2 NADP<sup>+</sup> + 3 ADP + 3 P<sub>i</sub> + light \u2192 2 NADPH + 2 H<sup>+</sup> + 3 ATP + O<sub>2</sub>\"}},\"i\":0}}]}' id=\"mwAaQ\">.mw-parser-output .block-indent{padding-left:3em;padding-right:0;overflow:hidden} 2 H 2 O + 2 NADP + + 3 ADP + 3 P i + light \u2192 2 NADPH + 2 H + + 3 ATP + O 2 Not all wavelengths of light can support photosynthesis. The photosynthetic action spectrum depends on the type of accessory pigments present. For example, in green plants , the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with absorption peaks in violet-blue and red light. In red algae , the action spectrum is blue-green light, which allows these algae to use the blue end of the spectrum to grow in the deeper waters that filter out the longer wavelengths (red light) used by above-ground green plants. The non-absorbed part of the light spectrum is what gives photosynthetic organisms their color (e.g., green plants, red algae, purple bacteria ) and is the least effective for photosynthesis in the respective organisms . Z scheme The \"Z scheme\" In plants , light-dependent reactions occur in the thylakoid membranes of the chloroplasts where they drive the synthesis of ATP and NADPH . The light-dependent reactions are of two forms: cyclic and non-cyclic . In the non-cyclic reaction, the photons are captured in the light-harvesting antenna complexes of photosystem II by chlorophyll and other accessory pigments (see diagram \"Z-scheme\"). The absorption of a photon by the antenna complex loosens an electron by a process called photoinduced charge separation . The antenna system is at the core of the chlorophyll molecule of the photosystem II reaction center. That loosened electron is taken up by the primary electron-acceptor molecule, pheophytin . As the electrons are shuttled through an electron transport chain (the so-called Z-scheme shown in the diagram), a chemiosmotic potential is generated by pumping proton cations ( H + ) across the membrane and into the thylakoid space . An ATP synthase enzyme uses that chemiosmotic potential to make ATP during photophosphorylation , whereas NADPH is a product of the terminal redox reaction in the Z-scheme . The electron enters a chlorophyll molecule in Photosystem I . There it is further excited by the light absorbed by that photosystem . The electron is then passed along a chain of electron acceptors to which it transfers some of its energy . The energy delivered to the electron acceptors is used to move hydrogen ions across the thylakoid membrane into the lumen . The electron is eventually used to reduce the coenzyme NADP with an H + to NADPH (which has functions in the light-independent reaction); at that point, the path of that electron ends. The cyclic reaction is similar to that of the non-cyclic but differs in that it generates only ATP, and no reduced NADP (NADPH) is created. The cyclic reaction takes place only at photosystem I. Once the electron is displaced from the photosystem, the electron is passed down the electron acceptor molecules and returns to photosystem I, from where it was emitted, hence the name cyclic reaction . Water photolysis Main articles: Photodissociation and Oxygen evolution Linear electron transport through a photosystem will leave the reaction center of that photosystem oxidized . Elevating another electron will first require re-reduction of the reaction center. The excited electrons lost from the reaction center ( P700 ) of photosystem I are replaced by transfer from plastocyanin , whose electrons come from electron transport through photosystem II . Photosystem II, as the first step of the Z-scheme , requires an external source of electrons to reduce its oxidized chlorophyll a reaction center. The source of electrons for photosynthesis in green plants and cyanobacteria is water. Two water molecules are oxidized by the energy of four successive charge-separation reactions of photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions. The electrons yielded are transferred to a redox-active tyrosine residue that is oxidized by the energy of P680 + . This resets the ability of P680 to absorb another photon and release another photo-dissociated electron. The oxidation of water is catalyzed in photosystem II by a redox-active structure that contains four manganese ions and a calcium ion ; this oxygen-evolving complex binds two water molecules and contains the four oxidizing equivalents that are used to drive the water-oxidizing reaction (Kok's S-state diagrams). The hydrogen ions are released in the thylakoid lumen and therefore contribute to the transmembrane chemiosmotic potential that leads to ATP synthesis . Oxygen is a waste product of light-dependent reactions, but the majority of organisms on Earth use oxygen and its energy for cellular respiration , including photosynthetic organisms . [ 31 ] [ 32 ] Light-independent reactions Calvin cycle Main articles: Calvin cycle and Carbon fixation In the light-independent (or \"dark\") reactions, the enzyme RuBisCO captures CO 2 from the atmosphere and, in a process called the Calvin cycle , uses the newly formed NADPH and releases three-carbon sugars , which are later combined to form sucrose and starch . The overall equation for the light-independent reactions in green plants is [ 30 ] : 128 2</sub> + 9 ATP + 6 NADPH + 6 H<sup>+</sup> \u2192 C<sub>3</sub>H<sub>6</sub>O<sub>3</sub>-phosphate + 9 ADP + 8 P<sub>i</sub> + 6 NADP<sup>+</sup> + 3 H<sub>2</sub>O\"}},\"i\":0}}]}' id=\"mwAic\"/> 3 CO 2 + 9 ATP + 6 NADPH + 6 H + \u2192 C 3 H 6 O 3 -phosphate + 9 ADP + 8 P i + 6 NADP + + 3 H 2 O Overview of the Calvin cycle and carbon fixation Carbon fixation produces the three-carbon sugar intermediate , which is then converted into the final carbohydrate products. The simple carbon sugars photosynthesis produces are then used to form other organic compounds , such as the building material cellulose , the precursors for lipid and amino acid biosynthesis, or as a fuel in cellular respiration . The latter occurs not only in plants but also in animals when the carbon and energy from plants is passed through a food chain . The fixation or reduction of carbon dioxide is a process in which carbon dioxide combines with a five-carbon sugar , ribulose 1,5-bisphosphate , to yield two molecules of a three-carbon compound, glycerate 3-phosphate , also known as 3-phosphoglycerate. Glycerate 3-phosphate, in the presence of ATP and NADPH produced during the light-dependent stages, is reduced to glyceraldehyde 3-phosphate . This product is also referred to as 3-phosphoglyceraldehyde (PGAL) or, more generically, as triose phosphate. Most (five out of six molecules) of the glyceraldehyde 3-phosphate produced are used to regenerate ribulose 1,5-bisphosphate so the process can continue. The triose phosphates not thus \"recycled\" often condense to form hexose phosphates, which ultimately yield sucrose , starch , and cellulose , as well as glucose and fructose . The sugars produced during carbon metabolism yield carbon skeletons that can be used for other metabolic reactions like the production of amino acids and lipids . Carbon concentrating mechanisms On land Main articles: C4 carbon fixation , CAM photosynthesis , and Alarm photosynthesis Overview of C4 carbon fixation . (This image mistakenly shows lactic acid instead of pyruvate , and all the species ending in \"-ate\" are shown as unionized acids, such as malic acid and so on). In hot and dry conditions , plants close their stomata to prevent water loss. Under these conditions, CO 2 will decrease and oxygen gas , produced by the light reactions of photosynthesis, will increase, causing an increase of photorespiration by the oxygenase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and decrease in carbon fixation. Some plants have evolved mechanisms to increase the CO 2 concentration in the leaves under these conditions. [ 33 ] Plants that use the C 4 carbon fixation process chemically fix carbon dioxide in the cells of the mesophyll by adding it to the three-carbon molecule phosphoenolpyruvate (PEP), a reaction catalyzed by an enzyme called PEP carboxylase , creating the four-carbon organic acid oxaloacetic acid . Oxaloacetic acid or malate synthesized by this process is then translocated to specialized bundle sheath cells where the enzyme RuBisCO and other Calvin cycle enzymes are located, and where CO 2 released by decarboxylation of the four-carbon acids is then fixed by RuBisCO activity to the three-carbon 3-phosphoglyceric acids . The physical separation of RuBisCO from the oxygen-generating light reactions reduces photorespiration and increases CO 2 fixation and, thus, the photosynthetic capacity of the leaf . [ 34 ] C 4 plants can produce more sugar than C 3 plants in conditions of high light and temperature . Many important crop plants are C 4 plants, including maize , sorghum , sugarcane , and millet . Plants that do not use PEP-carboxylase in carbon fixation are called C 3 plants because the primary carboxylation reaction , catalyzed by RuBisCO, produces the three-carbon 3-phosphoglyceric acids directly in the Calvin-Benson cycle . Over 90% of plants use C 3 carbon fixation, compared to 3% that use C 4 carbon fixation; [ 35 ] however, the evolution of C 4 in over sixty plant lineages makes it a striking example of convergent evolution . [ 33 ] C 2 photosynthesis , which involves carbon-concentration by selective breakdown of photorespiratory glycine, is both an evolutionary precursor to C 4 and a useful carbon-concentrating mechanism in its own right. [ 36 ] Xerophytes , such as cacti and most succulents , also use PEP carboxylase to capture carbon dioxide in a process called Crassulacean acid metabolism (CAM). In contrast to C 4 metabolism, which spatially separates the CO 2 fixation to PEP from the Calvin cycle, CAM temporally separates these two processes. CAM plants have a different leaf anatomy from C 3 plants, and fix the CO 2 at night, when their stomata are open. CAM plants store the CO 2 mostly in the form of malic acid via carboxylation of phosphoenolpyruvate to oxaloacetate , which is then reduced to malate. Decarboxylation of malate during the day releases CO 2 inside the leaves, thus allowing carbon fixation to 3-phosphoglycerate by RuBisCO. CAM is used by 16,000 species of plants. [ 37 ] Calcium-oxalate -accumulating plants, such as Amaranthus hybridus and Colobanthus quitensis , show a variation of photosynthesis where calcium oxalate crystals function as dynamic carbon pools , supplying carbon dioxide (CO 2 ) to photosynthetic cells when stomata are partially or totally closed. This process was named alarm photosynthesis . Under stress conditions (e.g., water deficit ), oxalate released from calcium oxalate crystals is converted to CO 2 by an oxalate oxidase enzyme, and the produced CO 2 can support the Calvin cycle reactions. Reactive hydrogen peroxide (H 2 O 2 ), the byproduct of oxalate oxidase reaction, can be neutralized by catalase . Alarm photosynthesis represents a photosynthetic variant to be added to the well-known C4 and CAM pathways. However, alarm photosynthesis, in contrast to these pathways, operates as a biochemical pump that collects carbon from the organ interior (or from the soil ) and not from the atmosphere. [ 38 ] [ 39 ] In water Cyanobacteria possess carboxysomes , which increase the concentration of CO 2 around RuBisCO to increase the rate of photosynthesis. An enzyme, carbonic anhydrase , located within the carboxysome, releases CO 2 from dissolved hydrocarbonate ions (HCO \u2212 3 ). Before the CO 2 can diffuse out , RuBisCO concentrated within the carboxysome quickly sponges it up. HCO \u2212 3 ions are made from CO 2 outside the cell by another carbonic anhydrase and are actively pumped into the cell by a membrane protein. They cannot cross the membrane as they are charged, and within the cytosol they turn back into CO 2 very slowly without the help of carbonic anhydrase. This causes the HCO \u2212 3 ions to accumulate within the cell from where they diffuse into the carboxysomes. [ 40 ] Pyrenoids in algae and hornworts also act to concentrate CO 2 around RuBisCO. [ 41 ] [ 42 ] Order and kinetics The overall process of photosynthesis takes place in four stages: [ 14 ] Stage Event Site Time scale 1 Energy transfer in antenna chlorophyll Thylakoid membranes in the chloroplasts Femtosecond to picosecond 2 Transfer of electrons in photochemical reactions Picosecond to nanosecond 3 Electron transport chain and ATP synthesis Microsecond to millisecond 4 Carbon fixation and export of stable products Stroma of the chloroplasts and the cell cytosol Millisecond to second Efficiency Main article: Photosynthetic efficiency Plants usually convert light into chemical energy with a photosynthetic efficiency of 3\u20136%. [ 43 ] [ 44 ] Absorbed light that is unconverted is dissipated primarily as heat , with a small fraction (1\u20132%) reemitted as chlorophyll fluorescence at longer (redder) wavelengths . This fact allows measurement of the light reaction of photosynthesis by using chlorophyll fluorometers . [ 45 ] Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity , temperature , and proportion of carbon dioxide in the atmosphere , and can vary from 0.1% to 8%. [ 46 ] By comparison, solar panels convert light into electric energy at an efficiency of approximately 6\u201320% for mass-produced panels, and above 40% in laboratory devices. Scientists are studying photosynthesis in hopes of developing plants with increased yield . [ 44 ] The efficiency of both light and dark reactions can be measured, but the relationship between the two can be complex. For example, the light reaction creates ATP and NADPH energy molecules , which C 3 plants can use for carbon fixation or photorespiration . [ 47 ] Electrons may also flow to other electron sinks. [ 48 ] [ 49 ] [ 50 ] For this reason, it is not uncommon for authors to differentiate between work done under non-photorespiratory conditions and under photorespiratory conditions . [ 51 ] [ 52 ] [ 53 ] Chlorophyll fluorescence of photosystem II can measure the light reaction, and infrared gas analyzers can measure the dark reaction . [ 54 ] An integrated chlorophyll fluorometer and gas exchange system can investigate both light and dark reactions when researchers use the two separate systems together. [ 55 ] Infrared gas analyzers and some moisture sensors are sensitive enough to measure the photosynthetic assimilation of CO 2 and of \u0394 H 2 O using reliable methods . CO 2 is commonly measured in micromoles</span>\"}]],\"parts\":[{\"template\":{\"target\":{\"wt\":\"Abbr\",\"href\":\"./Template:Abbr\"},\"params\":{\"1\":{\"wt\":\"\u03bcmols\"},\"2\":{\"wt\":\"micromoles\"}},\"i\":0}}]}' id=\"mwA7g\">\u03bcmols /( m 2 / s ), parts per million, or volume per million; and H 2 O is commonly measured in millimole</span>\"}]],\"parts\":[{\"template\":{\"target\":{\"wt\":\"Abbr\",\"href\":\"./Template:Abbr\"},\"params\":{\"1\":{\"wt\":\"mmols\"},\"2\":{\"wt\":\"millimole\"}},\"i\":0}}]}' id=\"mwA8A\">mmols /(m 2 /s) or in millibars</span>\"}]],\"parts\":[{\"template\":{\"target\":{\"wt\":\"Abbr\",\"href\":\"./Template:Abbr\"},\"params\":{\"1\":{\"wt\":\"mbars\"},\"2\":{\"wt\":\"millibars\"}},\"i\":0}}]}' id=\"mwA8M\">mbars . By measuring CO 2 assimilation , \u0394H 2 O, leaf temperature, barometric pressure , leaf area, and photosynthetically active radiation (PAR), it becomes possible to estimate, \"A\" or carbon assimilation, \"E\" or transpiration , \"gs\" or stomatal conductance , and \"Ci\" or intracellular CO 2 . [ 56 ] However, it is more common to use chlorophyll fluorescence for plant stress measurement , where appropriate, because the most commonly used parameters FV/FM and Y(II) or F/FM' can be measured in a few seconds, allowing the investigation of larger plant populations. [ 53 ] Gas exchange systems that offer control of CO 2 levels, above and below ambient , allow the common practice of measurement of A/Ci curves, at different CO 2 levels, to characterize a plant's photosynthetic response. [ 56 ] Integrated chlorophyll fluorometer \u2013 gas exchange systems allow a more precise measure of photosynthetic response and mechanisms. [ 54 ] [ 55 ] While standard gas exchange photosynthesis systems can measure Ci, or substomatal CO 2 levels, the addition of integrated chlorophyll fluorescence measurements allows a more precise measurement of C C, the estimation of CO 2 concentration at the site of carboxylation in the chloroplast, to replace Ci. [ 55 ] [ 54 ] CO 2 concentration in the chloroplast becomes possible to estimate with the measurement of mesophyll conductance or g m using an integrated system. [ 54 ] [ 55 ] [ 57 ] Photosynthesis measurement systems are not designed to directly measure the amount of light the leaf absorbs, but analysis of chlorophyll fluorescence , P700 - and P515-absorbance, and gas exchange measurements reveal detailed information about, e.g., the photosystems , quantum efficiency and the CO 2 assimilation rates. With some instruments, even wavelength dependency of the photosynthetic efficiency can be analyzed . [ 58 ] A phenomenon known as quantum walk increases the efficiency of the energy transport of light significantly. In the photosynthetic cell of an alga , bacterium , or plant, there are light-sensitive molecules called chromophores arranged in an antenna-shaped structure called a photocomplex. When a photon is absorbed by a chromophore, it is converted into a quasiparticle referred to as an exciton , which jumps from chromophore to chromophore towards the reaction center of the photocomplex, a collection of molecules that traps its energy in a chemical form accessible to the cell's metabolism. The exciton's wave properties", "Industrial Revolution 1760\u20131840 agrarian to industrial era shift .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} This article is about the 1760\u20131840 agrarian to industrial era shift. For a more general overview, see Industrialisation . 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When this tag was added, its readable prose size was 16,000 words. Consider splitting content into sub-articles, condensing it, or adding subheadings . Please discuss this issue on the article's talk page . ( February 2025 ) .mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} Industrial Revolution c. 1760 \u2013 c. 1840 Proto-industrialisation Second Industrial Revolution A Roberts Loom in a weaving shed in the United Kingdom in 1835 Location .mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0} Great Britain Western Europe North America Key events Mechanised textile production Canal construction Steam engine Factory system Iron production increase .mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:\": \"}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:\"\\a0 \u00b7 \";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li 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.sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} History of technology By technological eras Premodern / Pre-industrial Prehistoric Stone Age ( lithic ) First Agricultural Revolution Copper Age Urban revolution Bronze Age Iron Age Ancient Modern Proto-industrialization Second Agricultural Revolution First Industrial Revolution Standardization Second Industrial Revolution Machine Age Jet Age Third Agricultural Revolution Atomic Age Space Age Digital transformation Information Age Fourth Industrial Revolution Imagination Age Future Post-industrial Singularity Emerging technologies By historical regions Ancient Africa Ancient Egypt Indian subcontinent Ancient China Maya civilization Hellenistic world Roman Empire Byzantine Empire Medieval Islamic world Arab Agricultural Revolution Medieval Europe Renaissance Europe By type of technology History of agriculture History of biotechnology History of communication History of computer hardware History of electrical engineering History of manufacturing History of maritime History of materials science History of measurement History of medicine History of simple machine History of nuclear technology History of transport Technology timelines Timeline of historic inventions Technological revolution Complete list by category Article indices Outline of technology Outline of prehistoric technology .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e The Industrial Revolution , sometimes called the First Industrial Revolution in contrast to the subsequent Second Industrial Revolution , was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succeeding the Second Agricultural Revolution . Beginning in Great Britain around 1760, the Industrial Revolution had spread to continental Europe and the United States by about 1840. [ 1 ] This transition included going from hand production methods to machines ; new chemical manufacturing and iron production processes; the increasing use of water power and steam power ; the development of machine tools ; and rise of the mechanised factory system . Output greatly increased, and the result was an unprecedented rise in population and population growth . The textile industry was the first to use modern production methods, [ 2 ] : 40 and textiles became the dominant industry in terms of employment, value of output, and capital invested. [ 2 ] Many technological and architectural innovations were British. [ 3 ] [ 4 ] By the mid-18th century, Britain was the leading commercial nation, [ 5 ] controlled a global trading empire with colonies in North America and the Caribbean, and had military and political hegemony on the Indian subcontinent . [ 6 ] [ 7 ] [ 8 ] [ 9 ] The development of trade and rise of business were among the major causes of the Industrial Revolution. [ 2 ] : 15 Developments in law facilitated the revolution, such as courts ruling in favour of property rights . An entrepreneurial spirit and consumer revolution helped drive industrialisation . [ 10 ] The Industrial Revolution influenced almost every aspect of life. In particular, average income and population began to exhibit unprecedented sustained growth. Economists note the most important effect was that the standard of living for most in the Western world began to increase consistently for the first time, though others have said it did not begin to improve meaningfully until the 20th century. [ 11 ] [ 12 ] [ 13 ] GDP per capita was broadly stable before the Industrial Revolution and the emergence of the modern capitalist economy, [ 14 ] afterwards saw an era of per-capita economic growth in capitalist economies. [ 15 ] Economic historians agree that the onset of the Industrial Revolution is the most important event in human history , comparable only to the adoption of agriculture with respect to material advancement. [ 16 ] The precise start and end of the Industrial Revolution is debated among historians, as is the pace of economic and social changes . [ 17 ] [ 18 ] [ 19 ] According to Cambridge University professor Leigh Shaw-Taylor, Britain was already industrialising in the 17th century. [ 20 ] [ 21 ] Eric Hobsbawm held that the Industrial Revolution began in Britain in the 1780s and was not fully felt until the 1830s, [ 17 ] while T. S. Ashton held that it occurred between 1760 and 1830. [ 18 ] Rapid adoption of mechanized textiles spinning occurred in Britain in the 1780s, [ 22 ] and high rates of growth in steam power and iron production occurred after 1800. Mechanised textile production spread from Britain to continental Europe and the US in the early 19th century. [ 2 ] A recession occurred from the late 1830s when the adoption of the Industrial Revolution's early innovations, such as mechanised spinning and weaving, slowed as markets matured despite increased adoption of locomotives, steamships, and hot blast iron smelting . New technologies such as the electrical telegraph , widely introduced in the 1840s in the UK and US, were not sufficient to drive high rates of growth. Rapid growth reoccurred after 1870, springing from new innovations in the Second Industrial Revolution . These included steel-making processes , mass production , assembly lines , electrical grid systems, large-scale manufacture of machine tools, and use of advanced machinery in steam-powered factories. [ 2 ] [ 23 ] [ 24 ] [ 25 ] .mw-parser-output .toclimit-2 .toclevel-1 ul,.mw-parser-output .toclimit-3 .toclevel-2 ul,.mw-parser-output .toclimit-4 .toclevel-3 ul,.mw-parser-output .toclimit-5 .toclevel-4 ul,.mw-parser-output .toclimit-6 .toclevel-5 ul,.mw-parser-output .toclimit-7 .toclevel-6 ul{display:none} Etymology The earliest recorded use of \"Industrial Revolution\" was in 1799 by French envoy Louis-Guillaume Otto , announcing that France had entered the race to industrialise. [ 26 ] Raymond Williams states: \"The idea of a new social order based on major industrial change was clear in Southey and Owen , between 1811\u201318, and was implicit as early as Blake in the early 1790s and Wordsworth at the turn of the [19th] century.\" The term Industrial Revolution applied to technological change became more common by the 1830s, as in J\u00e9r\u00f4me-Adolphe Blanqui 's description in 1837 of la r\u00e9volution industrielle . [ 27 ] Friedrich Engels in The Condition of the Working Class in England in 1844 spoke of \"an industrial revolution, a revolution which...changed the whole of civil society\". His book was not translated into English until the late 19th century, and the expression did not enter everyday language till then. Credit for its popularisation is given to Arnold Toynbee , whose 1881 lectures gave a detailed account of the term. [ 28 ] Economic historians such as Mendels, Pomeranz , and Kridte argue proto-industrialisation in parts of Europe, the Islamic world , Mughal India , and China created the social and economic conditions that led to the Industrial Revolution, thus causing the Great Divergence . [ 29 ] [ 30 ] [ 31 ] Some historians, such as John Clapham and Nicholas Crafts , have argued that the economic and social changes occurred gradually and that revolution is a misnomer. [ 32 ] Requirements It has been suggested that this article be split out into a new article titled Technologies of the Industrial Revolution . ( Discuss ) ( February 2026 ) Several key factors enabled industrialisation. High agricultural productivity\u2014exemplified by the British Agricultural Revolution \u2014freed up labor and ensured food surpluses. The presence of skilled managers and entrepreneurs , an extensive network of ports, rivers, canals, and roads for efficient transport, and abundant natural resources such as coal, iron, and water power further supported industrial growth. Political stability, a legal system favorable to business, and access to financial capital also played crucial roles. Once industrialisation began in Britain in the 18th century, its spread was facilitated by the eagerness of British entrepreneurs to export industrial methods and the willingness of other nations to adopt them. By the early 19th century, industrialisation had reached Western Europe and the United States, and by the late 19th century, Japan. [ 33 ] [ 34 ] Important technological developments The commencement of the Industrial Revolution is closely linked to a small number of innovations, [ 35 ] beginning in the second half of the 18th century. By the 1830s, the following gains had been made in important technologies: Textiles \u2013 mechanised cotton spinning powered by water, and later steam, increased output per worker by a factor of around 500. The power loom increased output by a factor of 40. [ 36 ] The cotton gin increased productivity of removing seed from cotton by a factor of 50. [ 24 ] Large gains in productivity occurred in spinning and weaving of wool and linen , but were not as great as in cotton . [ 2 ] Steam power \u2013 the efficiency of steam engines increased so they used between one-fifth and one-tenth as much fuel. The adaptation of stationary steam engines to rotary motion made them suitable for industrial uses. [ 2 ] : 82 The high-pressure engine had a high power-to-weight ratio , making it suitable for transportation. [ 25 ] Steam power underwent a rapid expansion after 1800. Iron-making \u2013 the substitution of coke for charcoal greatly lowered the fuel cost of pig iron and wrought iron production. [ 2 ] : 89\u201393 Using coke also allowed larger blast furnaces , [ 37 ] [ 38 ] resulting in economies of scale . The steam engine began being used to power blast air in the 1750s, enabling a large increase in iron production by overcoming the limitation of water power. [ 39 ] The cast iron blowing cylinder was first used in 1760. It was improved by making it double acting, which allowed higher blast furnace temperatures. The puddling process produced structural grade iron at lower cost than the finery forge . [ 40 ] The rolling mill was fifteen times faster than hammering wrought iron. Developed in 1828, hot blast greatly increased fuel efficiency in iron production. Invention of machine tools \u2013 the first machine tools were the screw-cutting lathe , the cylinder boring machine, and the milling machine . Machine tools made the economical manufacture of precision metal parts possible, although it took decades to develop effective techniques for making interchangeable parts. [ 41 ] Textile manufacture Main article: Textile manufacture during the British Industrial Revolution British textile industry Weaving with handlooms from William Hogarth 's Industry and Idleness in 1747 In 1750, Britain imported 2.5 million pounds of raw cotton, most of which was spun and woven by the cottage industry in Lancashire . The work was done by hand in workers' homes or master weavers' shops. Wages were six times those in India in 1770 when productivity in Britain was three times higher. [ 42 ] In 1787, raw cotton consumption was 22 million pounds, most of which was cleaned, carded, and spun on machines. [ 2 ] : 41\u201342 The British textile industry used 52 million pounds of cotton in 1800, and 588 million pounds in 1850. [ 43 ] The share of value added by the cotton industry in Britain was 2.6% in 1760, 17% in 1801, and 22% in 1831. Value added by the woollen industry was 14% in 1801. Cotton factories numbered about 900 in 1797. In 1760, approximately one-third of cotton cloth manufactured was exported, rising to two-thirds by 1800. In 1781, cotton spun amounted to 5 million pounds, which increased to 56 million pounds by 1800. In 1800, less than 0.1% of world cotton cloth was produced on machinery invented in Britain. In 1788, there were 50,000 spindles in Britain, rising to 7 million over the next 30 years. [ 42 ] Wool The earliest European attempts at mechanised spinning were with wool; however, wool spinning proved more difficult to mechanise than cotton. Productivity improvement in wool spinning during the Industrial Revolution was significant, but less than cotton. [ 2 ] [ 9 ] Silk John Lombe 's silk mill site today in Derby , rebuilt as Derby Silk Mill Arguably the first highly mechanised factory was John Lombe 's water-powered silk mill at Derby , operational by 1721. Lombe learned silk thread manufacturing by taking a job in Italy and acting as an industrial spy; however, because the Italian silk industry guarded its secrets, the state of the industry at that time is unknown. Although Lombe's factory was technically successful, the supply of raw silk from Italy was cut off to eliminate competition. To promote manufacturing, the Crown paid for models of Lombe's machinery which were exhibited in the Tower of London . [ 44 ] [ 45 ] Cotton Parts of India, China, Central America, South America, and the Middle East have a history of hand-manufacturing cotton textiles, which became a major industry after 1000 AD. Most cotton was grown by small farmers alongside food and spun in households for domestic consumption. In the 1400s, China began to require households to pay part of their taxes in cotton cloth. By the 17th century, almost all Chinese wore cotton clothing, and it could be used as a medium of exchange . In India, cotton textiles were manufactured for distant markets, often produced by professional weavers. [ 42 ] Cotton was a difficult raw material for Europe to obtain before it was grown on colonial plantations . [ 42 ] Spanish explorers found Native Americans growing sea island ( Gossypium barbadense ) and upland cotton ( Gossypium hirsutum ). Sea island cotton was exported from Barbados from the 1650s. Upland cotton was uneconomical because of the difficulty of removing seed, a problem solved by the cotton gin . [ 24 ] : 157 A strain of cotton seed brought from Mexico to Natchez, Mississippi , in 1806 became the parent genetic material for 90% of world production today; it produced bolls three to four times faster to pick. [ 42 ] Trade and textiles European colonial empires at the start of the Industrial Revolution, superimposed upon modern political boundaries The Age of Discovery was followed by colonialism beginning around the 16th century. Following the discovery of a trade route to India around southern Africa by the Portuguese, the British founded the East India Company , and other countries founded companies, which established trading posts throughout the Indian Ocean region. [ 42 ] A large segment of this trade was in cotton textiles, which were purchased in India and sold in Southeast Asia , including the Indonesian archipelago where spices were purchased for sale to Southeast Asia and Europe. By the 1760s, cloth was over three-quarters of the East India Company's exports. Indian textiles were in demand in Europe, where previously only wool and linen were available; however, cotton goods consumed in Europe was minor until the early 19th century. [ 42 ] Pre-mechanized European textile production Weaver in Nuremberg , c. 1524 By 1600, Flemish refugees began weaving cotton in English towns where cottage spinning and weaving of wool and linen was established. They were left alone by the guilds who did not consider cotton a threat. Earlier European attempts at cotton spinning and weaving were in 12th-century Italy and 15th-century southern Germany, but these ended when the supply of cotton was cut off. British cloth could not compete with Indian cloth because India's labour cost was approximately one-fifth that of Britain's. [ 22 ] In 1700 and 1721, the British government passed Calico Acts to protect domestic woollen and linen industries from cotton fabric imported from India. [ 2 ] [ 46 ] The demand for heavier fabric was met by a domestic industry based around Lancashire that produced fustian , a cloth with flax warp and cotton weft . Flax was used for the warp because wheel-spun cotton had insufficient strength, the resulting blend was not as soft as 100% cotton and more difficult to sew. [ 46 ] On the eve of the Industrial Revolution, spinning and weaving were done in households, for domestic consumption, and as a cottage industry under the putting-out system . Under the putting-out system, home-based workers produced under contract to merchant sellers, who often supplied the raw materials. In the off-season, the women, typically farmers' wives, did the spinning and the men did the weaving. Using the spinning wheel , it took 4\u20138 spinners to supply one handloom weaver. [ 2 ] [ 46 ] [ 47 ] : 823 Invention of textile machinery A model of the spinning jenny in a museum in Wuppertal . Invented by James Hargreaves in 1764, the spinning jenny was one of the innovations that started the revolution. The only surviving example of a spinning mule built by the inventor Samuel Crompton, the mule produced high-quality thread with minimal labour, now on display at Bolton Museum in Greater Manchester The interior of Marshall's Temple Works in Leeds , West Yorkshire The flying shuttle , patented in 1733 by John Kay , doubled the output of a weaver, worsening the imbalance between spinning and weaving. It became widely used around Lancashire after 1760 when John's son, Robert , invented the dropbox, which facilitated changing thread colors. [ 47 ] : 821\u2013822 Lewis Paul patented the roller spinning frame and the flyer-and- bobbin system for drawing wool to a more even thickness. The technology was developed with John Wyatt of Birmingham . In 1743, a factory opened in Northampton with 50 spindles on each of five of Paul and Wyatt's machines. A similar mill was built by Daniel Bourn . Paul and Bourn patented carding machines in 1748. Based on two sets of rollers that travelled at different speeds, it was later used in the first cotton spinning mill . In 1764, in Oswaldtwistle , Lancashire, James Hargreaves invented the spinning jenny . It was the first practical spinning frame with multiple spindles. [ 48 ] The jenny worked similarly to the spinning wheel, by first clamping down on the fibres, then drawing them out, followed by twisting. [ 49 ] It was a simple, wooden-framed machine that only cost \u00a36 for a 40-spindle model in 1792 [ 50 ] and was used mainly by home spinners. [ 47 ] : 825\u2013827 The water frame , was developed by Richard Arkwright , who patented it in 1769. The design was partly based on a spinning machine built by Kay, hired by Arkwright. [ 47 ] : 827\u2013830 The water frame could produce a hard, medium-count thread suitable for warp, finally allowing 100% cotton cloth to be made in Britain. Arkwright used water power at a factory in Cromford , Derbyshire in 1771, giving the invention its name. Samuel Crompton invented the spinning mule in 1779, so called because it is a hybrid of Arkwright's water frame and James Hargreaves 's spinning jenny . Crompton's mule could produce finer thread than hand spinning, at lower cost. Mule-spun thread was of suitable strength to be used as a warp and allowed Britain to produce highly competitive yarn in large quantities. [ 47 ] : 832 Realising expiration of the Arkwright patent would greatly increase the supply of spun cotton and lead to a shortage of weavers, Edmund Cartwright developed a vertical power loom which he patented in 1785. [ 47 ] : 834 Samuel Horrocks patented a loom in 1813, which was improved by Richard Roberts in 1822, and these were produced in large numbers by Roberts, Hill & Co. Roberts was a maker of high-quality machine tools and pioneer in the use of jigs and gauges for precision workshop measurement. [ 51 ] The demand for cotton presented an opportunity to planters in the US, who thought upland cotton would be profitable if a better way could be found to remove the seed. Eli Whitney responded by inventing the inexpensive cotton gin . A man using a cotton gin could remove seed in one day, which previously took two months. [ 24 ] [ 52 ] These advances were capitalised on by entrepreneurs , of whom the best known is Arkwright. He is credited with a list of inventions, but these were developed by such people as Kay and Thomas Highs . Arkwright nurtured the inventors, patented the ideas, financed the initiatives, and protected the machines. He created the cotton mill which brought the production processes together in a factory, and developed the use of power, which made cotton manufacture a mechanised industry. Other inventors increased the efficiency of spinning, so the supply of yarn increased greatly. Steam power was then applied to drive textile machinery. Manchester acquired the nickname Cottonopolis during the early 19th century owing to its sprawl of textile factories. [ 53 ] Though mechanisation dramatically decreased the cost of cotton cloth, by the mid-19th century machine-woven cloth still could not equal the quality of hand-woven Indian cloth. However, the high productivity of British textile manufacturing allowed coarser grades of British cloth to undersell hand-spun and woven fabric in low-wage India, destroying the Indian industry. [ 42 ] Metallurgy The reverberatory furnace could produce cast iron using mined coal; the burning coal is separated from the iron to prevent constituents of the coal, such as sulfur and silica, from becoming impurities in the iron. Iron production increased due to the ability to use mined coal directly. The Iron Bridge in Shropshire , England, the world's first bridge constructed of iron, opened in 1781. [ 54 ] British iron production In the UK in 1720, there were 20,500 tons of charcoal iron and 400 tons with coke. In 1806, charcoal iron production had dropped to 7,800 tons and coke cast iron was 250,000 tons. [ 39 ] : 125 In 1750, the UK imported 31,000 tons of bar iron and either refined from cast iron or directly produced 18,800 tons of bar iron, using charcoal and 100 tons using coke. In 1796, the UK was making 125,000 tons of bar iron with coke and 6,400 tons with charcoal; imports were 38,000 tons and exports were 24,600 tons. In 1806 the UK did not import bar iron but exported 31,500 tons. [ 39 ] : 125 Iron process innovations Horizontal (lower) and vertical (upper) cross-sections of a single puddling furnace A major change in the iron industries, during the Industrial Revolution, was the replacement of wood and other bio-fuels with coal . For a given amount of heat, mining coal required much less labour than cutting wood and converting it to charcoal , [ 55 ] and coal was more abundant than wood, supplies of which were becoming scarce before the enormous increase in iron production that took place in the late 18th century. [ 2 ] [ 39 ] : 122 In 1709, Abraham Darby made progress using coke to fuel his blast furnaces at Coalbrookdale . [ 56 ] However, the coke pig iron made was not suitable for making wrought iron and was used mostly for the production of cast iron goods. He had the advantage over his rivals in that his pots, cast by his patented process, were thinner and cheaper. In 1750, coke had replaced charcoal in the smelting of copper and lead and was in widespread use in glass production. In the smelting and refining of iron, coal and coke produced inferior iron to that made with charcoal because of the coal's sulfur content. Low sulfur coals were known, but they still contained harmful amounts. [ 39 ] : 122\u2013125 Another factor limiting the iron industry was the scarcity of water power to power blast bellows. This limitation was overcome by the steam engine. [ 39 ] Use of coal in iron smelting started before the Industrial Revolution, based on innovations by Clement Clerke and others from 1678, using coal reverberatory furnaces known as cupolas. These were operated by the flames playing on the ore and charcoal or coke mixture, reducing the oxide to metal. This has the advantage that impurities in the coal do not migrate into the metal. This technology was applied to lead in 1678, copper in 1687, and iron foundries in the 1690s, but in this case the reverberatory furnace was known as an air furnace. [ 57 ] Coke pig iron was hardly used to produce wrought iron until 1755, when Darby's son Abraham Darby II built furnaces at Horsehay and Ketley where low sulfur coal was available, and not far from Coalbrookdale. These furnaces were equipped with water-powered bellows, the water being pumped by Newcomen atmospheric engines . Abraham Darby III installed similar steam-pumped, water-powered blowing cylinders at the Dale Company when he took control in 1768. The Dale Company used Newcomen engines to drain its mines and made parts for engines which it sold throughout the country. [ 39 ] : 123\u2013125 Steam engines made the use of higher-pressure and volume blast practical; however, the leather used in bellows was expensive to replace. In 1757, ironmaster John Wilkinson patented a hydraulic powered blowing engine for blast furnaces. [ 58 ] The blowing cylinder for blast furnaces was introduced in 1760 and the first blowing cylinder made of cast iron is believed to be the one used at Carrington in 1768, designed by John Smeaton . [ 39 ] : 124, 135 Cast iron cylinders for use with a piston were difficult to manufacture. James Watt had difficulty trying to have a cylinder made for his first steam engine. In 1774 Wilkinson invented a machine for boring cylinders. After Wilkinson bored the first successful cylinder for a Boulton and Watt steam engine in 1776, he was given an exclusive contract for providing cylinders. [ 24 ] [ 59 ] Watt developed a rotary steam engine in 1782, they were widely applied to blowing, hammering, rolling and slitting. [ 39 ] : 124 In addition to lower cost and greater availability, coke had other advantages over charcoal in that it was harder and made the column of materials flowing down the blast furnace more porous and did not crush in the much taller furnaces of the late 19th century. [ 60 ] [ 61 ] As cast iron became cheaper and widely available, it began being a structural material for bridges and buildings. A famous early example is The Iron Bridge built in 1778 with cast iron produced by Abraham Darby III. [ 54 ] However, most cast iron was converted to wrought iron. Conversion of cast iron had long been done in a finery forge . An improved refining process known as potting and stamping was developed, but this was superseded by Henry Cort 's puddling process. Cort developed significant iron manufacturing processes: rolling in 1783 and puddling in 1784. [ 2 ] : 91 Puddling produced a structural grade iron at a relatively low cost. Puddling was backbreaking and extremely hot work. Few puddlers lived to be 40. [ 2 ] : 218 Puddling became widely used after 1800. British iron manufacturers had used considerable amounts of iron imported from Sweden and Russia to supplement domestic supplies. Because of the increased British production, by the 1790s Britain eliminated imports and became a net exporter of bar iron. Hot blast , patented by the Scottish inventor James Beaumont Neilson in 1828, was the most important development of the 19th century for saving", "Theory of relativity Two interrelated physics theories by Albert Einstein .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} This article is about the scientific concept. For philosophical or ontological theories about relativity, see Relativism . For the silent film, see The Einstein Theory of Relativity . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> Simulation of the merger GW150914 , showing spacetime distortion from gravity as the black holes orbit and merge The theory of relativity comprises two physics theories by Albert Einstein : special relativity and general relativity , proposed and published in 1905 and 1915, respectively. [ 1 ] Special relativity applies to all physical phenomena in the absence of gravity . General relativity explains the law of gravitation and its relation to the forces of nature. [ 2 ] It applies to the cosmological and astrophysical realm, including astronomy. [ 3 ] The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton . [ 3 ] [ 4 ] [ 5 ] It introduced concepts including 4- dimensional spacetime as a unified entity of space and time , relativity of simultaneity , kinematic and gravitational time dilation , and length contraction . In the field of physics, relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age . With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars , black holes , and gravitational waves . 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a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} General relativity G \u03bc \u03bd + \u039b g \u03bc \u03bd = \u03ba T \u03bc \u03bd {\\displaystyle G_{\\mu \\nu }+\\Lambda g_{\\mu \\nu }={\\kappa }T_{\\mu \\nu }} Introduction History Timeline Tests Mathematical formulation Fundamental concepts Equivalence principle Special relativity World line Pseudo-Riemannian manifold Phenomena Kepler problem Gravitational lensing Gravitational redshift Gravitational time dilation Gravitational waves Frame-dragging Geodetic effect Event horizon Singularity Black hole Spacetime Spacetime diagrams Minkowski spacetime Einstein\u2013Rosen bridge Equations Formalisms Equations Linearized gravity Einstein field equations Friedmann Geodesics Mathisson\u2013Papapetrou\u2013Dixon Hamilton\u2013Jacobi\u2013Einstein Raychaudhuri Formalisms ADM NP BSSN Post-Newtonian Advanced theory Kaluza\u2013Klein theory Quantum gravity Solutions Schwarzschild ( interior ) Reissner\u2013Nordstr\u00f6m Einstein\u2013Rosen waves Wormhole G\u00f6del Kerr Kerr\u2013Newman Kerr\u2013Newman\u2013de Sitter Kasner Kantowski-Sachs Lema\u00eetre\u2013Tolman Wahlquist Taub\u2013NUT Milne Robertson\u2013Walker Oppenheimer\u2013Snyder pp-wave van Stockum dust Hartle\u2013Thorne Vaidya Peres De Sitter-Schwarzschild McVittie Weyl Scientists Einstein Lorentz Hilbert Poincar\u00e9 Schwarzschild de Sitter Reissner Nordstr\u00f6m Weyl Eddington Friedmann Milne Zwicky Lema\u00eetre Oppenheimer G\u00f6del Wheeler Robertson Bardeen Walker Kerr Chandrasekhar Ehlers Penrose Hawking Raychaudhuri Taylor Hulse van Stockum Taub Newman Yau Thorne others Physics portal Category .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e Albert Einstein published the theory of special relativity in 1905, building on many theoretical results and empirical findings obtained by Albert A. Michelson , Hendrik Lorentz , Henri Poincar\u00e9 and others. Max Planck , Hermann Minkowski and others did subsequent work. Einstein developed general relativity between 1907 and 1915, with contributions by many others after 1915. The final form of general relativity was published in 1916. [ 3 ] The term \"theory of relativity\" was based on the expression \"relative theory\" ( German : Relativtheorie ) used in 1906 by Planck, who emphasized how the theory uses the principle of relativity . In the discussion section of the same paper, Alfred Bucherer used for the first time the expression \"theory of relativity\" ( German : Relativit\u00e4tstheorie ). [ 6 ] [ 7 ] By the 1920s, the physics community understood and accepted special relativity. [ 8 ] It rapidly became a significant and necessary tool for theorists and experimentalists in the new fields of atomic physics , nuclear physics , and quantum mechanics . By comparison, general relativity did not appear to be as useful, beyond making minor corrections to predictions of Newtonian gravitation theory. [ 3 ] It seemed to offer little potential for experimental test, as most of its assertions were on an astronomical scale. Its mathematics seemed difficult and fully understandable only by a small number of people. Around 1960, general relativity became central to physics and astronomy. New mathematical techniques to apply to general relativity streamlined calculations and made its concepts more easily visualized. As astronomical phenomena were discovered, such as quasars (1963), the 3-kelvin microwave background radiation (1965), pulsars (1967), and the first black hole candidates (1981), [ 3 ] the theory explained their attributes, and measurement of them further confirmed the theory. Special relativity Main article: Special relativity Special relativity is a theory of the structure of spacetime . It was introduced in Einstein's 1905 paper \" On the Electrodynamics of Moving Bodies \" (for the contributions of many other physicists and mathematicians, see History of special relativity ). Special relativity is based on two postulates which are contradictory in classical mechanics : The laws of physics are the same for all observers in any inertial frame of reference relative to one another ( principle of relativity ). The speed of light in vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source. The resultant theory copes with experiment better than classical mechanics. For instance, postulate 2 explains the results of the Michelson\u2013Morley experiment . Moreover, the theory has many surprising and counterintuitive consequences. Some of these are: Relativity of simultaneity : Two events, simultaneous for one observer, may not be simultaneous for another observer if the observers are in relative motion. Time dilation : Moving clocks are measured to tick more slowly than an observer's \"stationary\" clock. Length contraction : Objects are measured to be shortened in the direction that they are moving with respect to the observer. Maximum speed is finite : No physical object, message or field line can travel faster than the speed of light in vacuum. The effect of gravity can only travel through space at the speed of light, not faster or instantaneously. Mass\u2013energy equivalence : 2</sup>\"}},\"i\":0}}]}' id=\"mwtg\"> E = mc 2 , energy and mass are equivalent and transmutable. Relativistic mass , idea used by some researchers. [ 9 ] The defining feature of special relativity is the replacement of the Galilean transformations of classical mechanics by the Lorentz transformations . (See Maxwell's equations of electromagnetism .) General relativity Main articles: General relativity and Introduction to general relativity General relativity is a theory of gravitation developed by Einstein in the years 1907\u20131915. The development of general relativity began with the equivalence principle , under which the states of accelerated motion and being at rest in a gravitational field (for example, when standing on the surface of the Earth) are physically identical. The upshot of this is that free fall is inertial motion : an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics . This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects cannot accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first proposed that spacetime is curved . Einstein discussed his idea with mathematician Marcel Grossmann and they concluded that general relativity could be formulated in the context of Riemannian geometry which had been developed in the 1800s. [ 10 ] In 1915, he devised the Einstein field equations which relate the curvature of spacetime with the mass, energy, and any momentum within it. Some of the consequences of general relativity are: Gravitational time dilation : Clocks run slower in deeper gravitational wells. [ 11 ] Precession : Orbits precess in a way unexpected in Newton's theory of gravity. (This has been observed in the orbit of Mercury and in binary pulsars ). Light deflection : Rays of light bend in the presence of a gravitational field. Frame-dragging : Rotating masses \"drag along\" the spacetime around them. Expansion of the universe : The universe is expanding, and certain components within the universe can accelerate the expansion . Technically, general relativity is a theory of gravitation whose defining feature is its use of the Einstein field equations . The solutions of the field equations are metric tensors which define the topology of the spacetime and how objects move inertially. Experimental evidence Einstein explained that the theory of relativity falls under a category of scientific frameworks known as \"principle-theories\"\u2014theories that start not from speculative constructs or imagined mechanisms, but from well-established empirical facts and observed regularities in nature. Unlike constructive theories, which attempt to build models of phenomena from assumed underlying processes, principle-theories, such as relativity, adopt an analytic approach: they begin with experimentally verified principles and work deductively to uncover the logical consequences and constraints that any physical process must obey. By observing natural processes, we understand their general characteristics, devise mathematical models to describe what we observed, and by analytical means we deduce the necessary conditions that have to be satisfied. Measurement of separate events must satisfy these conditions and match the theory's conclusions. [ 2 ] Tests of special relativity Main article: Tests of special relativity A diagram of the Michelson\u2013Morley experiment Relativity is a falsifiable theory: It makes predictions that can be tested by experiment. In the case of special relativity, these include the principle of relativity, the constancy of the speed of light, and time dilation. [ 12 ] The predictions of special relativity have been confirmed in numerous tests since Einstein published his paper in 1905, but three experiments conducted between 1881 and 1938 were critical to its validation. These are the Michelson\u2013Morley experiment , the Kennedy\u2013Thorndike experiment , and the Ives\u2013Stilwell experiment . Einstein derived the Lorentz transformations from first principles in 1905, but these three experiments allow the transformations to be induced from experimental evidence. Maxwell's equations \u2014the foundation of classical electromagnetism\u2014describe light as a wave that moves with a characteristic velocity. The modern view is that light needs no medium of transmission, but Maxwell and his contemporaries were convinced that light waves were propagated in a medium, analogous to sound propagating in air, and ripples propagating on the surface of a pond. This hypothetical medium was called the luminiferous aether , at rest relative to the \"fixed stars\" and through which the Earth moves. Fresnel's partial ether dragging hypothesis ruled out the measurement of first-order (v/c) effects, and although observations of second-order effects (v 2 /c 2 ) were possible in principle, Maxwell thought they were too small to be detected with then-current technology. [ 13 ] [ 14 ] The Michelson\u2013Morley experiment was designed to detect second-order effects of the \"aether wind\"\u2014the motion of the aether relative to the Earth. Michelson designed an instrument called the Michelson interferometer to accomplish this. The apparatus was sufficiently accurate to detect the expected effects, but he obtained a null result when the first experiment was conducted in 1881, [ 15 ] and again in 1887. [ 16 ] Although the failure to detect an aether wind was a disappointment, the results were accepted by the scientific community. [ 14 ] In an attempt to salvage the aether paradigm, FitzGerald and Lorentz independently created an ad hoc hypothesis in which the length of material bodies changes according to their motion through the aether. [ 17 ] This was the origin of FitzGerald\u2013Lorentz contraction , and their hypothesis had no theoretical basis. The interpretation of the null result of the Michelson\u2013Morley experiment is that the round-trip travel time for light is isotropic (independent of direction), but the result alone is not enough to discount the theory of the aether or validate the predictions of special relativity. [ 18 ] [ 19 ] The Kennedy\u2013Thorndike experiment shown with interference fringes While the Michelson\u2013Morley experiment showed that the velocity of light is isotropic, it said nothing about how the magnitude of the velocity changed (if at all) in different inertial frames . The Kennedy\u2013Thorndike experiment was designed to do that, and was first performed in 1932 by Roy Kennedy and Edward Thorndike. [ 20 ] They obtained a null result, and concluded that \"there is no effect ... unless the velocity of the solar system in space is no more than about half that of the earth in its orbit\". [ 19 ] [ 21 ] That possibility was thought to be too coincidental to provide an acceptable explanation, so from the null result of their experiment it was concluded that the round-trip time for light is the same in all inertial reference frames. [ 18 ] [ 19 ] The Ives\u2013Stilwell experiment was carried out by Herbert Ives and G.R. Stilwell first in 1938 [ 22 ] and with better accuracy in 1941. [ 23 ] It was designed to test the transverse Doppler effect \u2013 the redshift of light from a moving source in a direction perpendicular to its velocity\u2014which had been predicted by Einstein in 1905. The strategy was to compare observed Doppler shifts with what was predicted by classical theory, and look for a Lorentz factor correction. Such a correction was observed, from which was concluded that the frequency of a moving atomic clock is altered according to special relativity. [ 18 ] [ 19 ] Those classic experiments have been repeated many times with increased precision. Other experiments include, for instance, relativistic energy and momentum increase at high velocities, experimental testing of time dilation , and modern searches for Lorentz violations . [ citation needed ] Tests of general relativity Main article: Tests of general relativity General relativity has also been confirmed many times, the classic experiments being the perihelion precession of Mercury 's orbit, the deflection of light by the Sun , and the gravitational redshift of light. Other tests confirmed the equivalence principle and frame dragging . Modern applications Far from being simply of theoretical interest, relativistic effects are important practical engineering concerns. Satellite-based measurement needs to take into account relativistic effects, as each satellite is in motion relative to an Earth-bound user, and is thus in a different frame of reference under the theory of relativity. Global positioning systems such as GPS , GLONASS , and Galileo , must account for all of the relativistic effects in order to work with precision, such as the consequences of the Earth's gravitational field. [ 24 ] This is also the case in the high-precision measurement of time. [ 25 ] Instruments ranging from electron microscopes to particle accelerators would not work if relativistic considerations were omitted. [ 26 ] See also Doubly special relativity Galilean invariance List of textbooks on relativity References .mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}body.skin-vector-2022 .mw-parser-output .reflist-columns-2{column-width:27em}body.skin-vector-2022 .mw-parser-output .reflist-columns-3{column-width:22.5em}.mw-parser-output .references[data-mw-group=upper-alpha]{list-style-type:upper-alpha}.mw-parser-output .references[data-mw-group=upper-roman]{list-style-type:upper-roman}.mw-parser-output .references[data-mw-group=lower-alpha]{list-style-type:lower-alpha}.mw-parser-output .references[data-mw-group=lower-greek]{list-style-type:lower-greek}.mw-parser-output .references[data-mw-group=lower-roman]{list-style-type:lower-roman}.mw-parser-output div.reflist-liststyle-upper-alpha .references{list-style-type:upper-alpha}.mw-parser-output div.reflist-liststyle-upper-roman .references{list-style-type:upper-roman}.mw-parser-output div.reflist-liststyle-lower-alpha .references{list-style-type:lower-alpha}.mw-parser-output div.reflist-liststyle-lower-greek .references{list-style-type:lower-greek}.mw-parser-output div.reflist-liststyle-lower-roman .references{list-style-type:lower-roman} \u2191 .mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:\"\\\"\"\"\\\"\"\"'\"\"'\"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url(\"//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url(\"//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url(\"//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url(\"//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg\")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}} Einstein A. (1916), Relativity: The Special and General Theory (Translation 1920), New York: H. Holt and Company 1 2 Einstein, Albert (28 November 1919). \"Time, Space, and Gravitation\" . The Times . 1 2 3 4 5 6 Will, Clifford M (2010). \"Relativity\" . Grolier Multimedia Encyclopedia . Archived from the original on 21 May 2020 . Retrieved 1 August 2010 . 1 2 Will, Clifford M (2010). \"Space-Time Continuum\" . Grolier Multimedia Encyclopedia . Retrieved 1 August 2010 . {{ cite encyclopedia }} : CS1 maint: deprecated archival service ( link ) 1 2 Will, Clifford M (2010). \"Fitzgerald\u2013Lorentz contraction\" . Grolier Multimedia Encyclopedia . Retrieved 1 August 2010 . {{ cite encyclopedia }} : CS1 maint: deprecated archival service ( link ) \u2191 Planck, Max (1906), \"Die Kaufmannschen Messungen der Ablenkbarkeit der \u03b2-Strahlen in ihrer Bedeutung f\u00fcr die Dynamik der Elektronen (The Measurements of Kaufmann on the Deflectability of \u03b2-Rays in their Importance for the Dynamics of the Electrons)\" , Physikalische Zeitschrift , 7 : 753\u2013 761 \u2191 Miller, Arthur I. (1981), Albert Einstein's special theory of relativity. Emergence (1905) and early interpretation (1905\u20131911) , Reading: Addison\u2013Wesley, ISBN 978-0-201-04679-3 \u2191 Hey, Anthony J.G.; Walters, Patrick (2003). The New Quantum Universe (illustrated, revised ed.). Cambridge University Press. p. 227. Bibcode : 2003nqu..book.....H . ISBN 978-0-521-56457-1 . \u2191 Greene, Brian. \"The Theory of Relativity, Then and Now\" . Retrieved 26 September 2015 . \u2191 Einstein, A.; Grossmann, M. (1913). \"Entwurf einer verallgemeinerten Relativit\u00e4tstheorie und einer Theorie der Gravitation\" [ Outline of a Generalized Theory of Relativity and of a Theory of Gravitation ] . Zeitschrift f\u00fcr Mathematik und Physik . 62 : 225\u2013 261. \u2191 Feynman, Richard Phillips; Mor\u00ednigo, Fernando B.; Wagner, William; Pines, David; Hatfield, Brian (2002). Feynman Lectures on Gravitation . West view Press. p. 68. ISBN 978-0-8133-4038-8 . , Lecture 5 \u2191 Roberts, T; Schleif, S; Dlugosz, JM, eds. (2007). \"What is the experimental basis of Special Relativity?\" . Usenet Physics FAQ . University of California, Riverside . Retrieved 31 October 2010 . \u2191 Maxwell, James Clerk (1880), \"On a Possible Mode of Detecting a Motion of the Solar System through the Luminiferous Ether\" , Nature , 21 (535): 314\u2013 315, Bibcode : 1880Natur..21S.314. , doi : 10.1038/021314c0 1 2 Pais, Abraham (1982). \"Subtle is the Lord ...\": The Science and the Life of Albert Einstein (1st ed.). Oxford: Oxford Univ. Press. pp. 111\u2013113 . ISBN 978-0-19-280672-7 . \u2191 Michelson, Albert A. (1881). \"The Relative Motion of the Earth and the Luminiferous Ether\" . American Journal of Science . 22 (128): 120\u2013 129. Bibcode : 1881AmJS...22..120M . doi : 10.2475/ajs.s3-22.128.120 . S2CID 130423116 . \u2191 Michelson, Albert A. & Morley, Edward W. (1887). \"On the Relative Motion of the Earth and the Luminiferous Ether\" . American Journal of Science . 34 (203): 333\u2013 345. Bibcode : 1887AmJS...34..333M . doi : 10.2475/ajs.s3-34.203.333 . S2CID 124333204 . {{ cite journal }} : CS1 maint: multiple names: authors list ( link ) \u2191 Pais, Abraham (1982). \"Subtle is the Lord ...\": The Science and the Life of Albert Einstein (1st ed.). Oxford: Oxford Univ. Press. p. 122 . ISBN 978-0-19-280672-7 . 1 2 3 Robertson, H.P. (July 1949). \"Postulate versus Observation in the Special Theory of Relativity\" (PDF) . Reviews of Modern Physics . 21 (3): 378\u2013 382. 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Bibcode : 1938JOSA...28..215I . doi : 10.1364/JOSA.28.000215 . \u2191 Ives, H.E.; Stilwell, G.R. (1941). \"An experimental study of the rate of a moving atomic clock. II\". Journal of the Optical Society of America . 31 (5): 369. Bibcode : 1941JOSA...31..369I . doi : 10.1364/JOSA.31.000369 . \u2191 Ashby, N. Relativity in the Global Positioning System. Living Rev. Relativ. 6 , 1 (2003). doi : 10.12942/lrr-2003-1 \"Archived copy\" (PDF) . Archived from the original (PDF) on 5 November 2015 . Retrieved 9 December 2015 . {{ cite web }} : CS1 maint: archived copy as title ( link ) \u2191 Francis, S.; B. Ramsey; S. Stein; Leitner, J.; Moreau, J.M.; Burns, R.; Nelson, R.A.; Bartholomew, T.R.; Gifford, A. (2002). \"Timekeeping and Time Dissemination in a Distributed Space-Based Clock Ensemble\" (PDF) . Proceedings 34th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting : 201\u2013 214. Archived from the original (PDF) on 17 February 2013 . Retrieved 14 April 2013 . \u2191 Hey, Tony; Hey, Anthony J. G.; Walters, Patrick (1997). Einstein's Mirror (illustrated ed.). Cambridge University Press. p. x (preface). ISBN 978-0-521-43532-1 . Further reading .mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}} Einstein, Albert (2005). Relativity: The Special and General Theory . Translated by Robert W. Lawson (The masterpiece science ed.). New York: Pi Press. ISBN 978-0-13-186261-6 . Einstein, Albert (1920). Relativity: The Special and General Theory (PDF) . Henry Holt and Company. Einstein, Albert; trans. Schilpp; Paul Arthur (1979). Albert Einstein, Autobiographical Notes (A Centennial ed.). La Salle, Illinois: Open Court Publishing Co. ISBN 978-0-87548-352-8 . Einstein, Albert (2009). Einstein's Essays in Science . Translated by Alan Harris (Dover ed.). Mineola, New York: Dover Publications. ISBN 978-0-486-47011-5 . Einstein, Albert (1956) [1922]. The Meaning of Relativity (5 ed.). Princeton University Press. The Meaning of Relativity Albert Einstein: Four lectures delivered at Princeton University, May 1921 How I created the theory of relativity Albert Einstein, 14 December 1922; Physics Today August 1982 Relativity Sidney Perkowitz Encyclop\u00e6dia Britannica External links .mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);color:inherit;display:flow-root}.mw-parser-output .infobox .side-box{font-size:100%}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:640px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}} @media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*=\"Wiktionary-logo-en-v2.svg\"]{filter:invert(1)brightness(55%)contrast(250%)hue-rotate(180deg)}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*=\"Wiktionary-logo-en-v2.svg\"]{filter:invert(1)brightness(55%)contrast(250%)hue-rotate(180deg)}} Wikiquote has quotations related to Theory of relativity . 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relativity Background Principle of relativity ( Galilean relativity Galilean transformation ) Special relativity Doubly special relativity Fundamental concepts Frame of reference Speed of light Hyperbolic orthogonality Rapidity Maxwell's equations Proper length Proper time Proper acceleration Relativistic mass Formulation Lorentz transformation Textbooks Phenomena Time dilation Mass\u2013energy equivalence (E=mc 2 ) Length contraction Relativity of simultaneity Relativistic Doppler effect Thomas precession Ladder paradox Twin paradox Terrell rotation Spacetime Light cone World line Minkowski diagram Biquaternions Minkowski space General relativity Background Introduction Mathematical formulation Fundamental concepts Equivalence principle Riemannian geometry Penrose diagram Geodesics Mach's principle Formulation ADM formalism BSSN formalism Einstein field equations Linearized gravity Post-Newtonian formalism Raychaudhuri equation Hamilton\u2013Jacobi\u2013Einstein equation Ernst 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Poincar\u00e9 Lorentz Einstein Hilbert Schwarzschild de Sitter Weyl Eddington Friedmann Lema\u00eetre Milne Robertson Chandrasekhar Zwicky Wheeler Choquet-Bruhat Kerr Zel'dovich Novikov Ehlers Geroch Penrose Hawking Taylor Hulse Bondi Misner Yau Thorne Weiss others Category v t e Albert Einstein Physics Theory of relativity Special relativity General relativity Mass\u2013energy equivalence (E=mc 2 ) Brownian motion Photoelectric effect Einstein coefficients Einstein solid Equivalence principle Einstein field equations Einstein radius Einstein relation (kinetic theory) Einstein ring Cosmological constant Bose\u2013Einstein condensate Bose\u2013Einstein statistics Bose\u2013Einstein correlations Einstein\u2013Cartan theory Einstein\u2013Infeld\u2013Hoffmann equations Einstein\u2013de Haas effect EPR paradox Bohr\u2013Einstein debates Teleparallelism Thought experiments Unsuccessful investigations Wave\u2013particle duality Gravitational wave Tea leaf paradox Works Annus mirabilis papers (1905) \" Investigations on the Theory of Brownian Movement \" (1905) Relativity: The Special and the General Theory (1916) The Meaning of Relativity (1922) The World as I See It (1934) The Evolution of Physics (1938) \" Why Socialism? \" (1949) Russell\u2013Einstein Manifesto (1955) In popular culture Die Grundlagen der Einsteinschen Relativit\u00e4ts-Theorie (1922 documentary) The Einstein Theory of Relativity (1923 documentary) Relics: Einstein's Brain (1994 documentary) Insignificance (1985 film) Young Einstein (1988 film) Picasso at the Lapin Agile (1993 play) I.Q. 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Click here for more information.\\\" id=\\\"mwBg\\\"><img alt=\\\"Featured article\\\" resource=\\\"./File:Cscr-featured.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/20px-Cscr-featured.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"466\\\" data-file-height=\\\"443\\\" data-file-type=\\\"drawing\\\" height=\\\"19\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/40px-Cscr-featured.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwBw\\\"/></a></span>\\n\"}' id=\"mwCA\"/> .mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} Immune system A scanning electron microscope image of a single neutrophil (yellow/right), engulfing anthrax bacteria (orange/left) \u2013 scale bar is 5 \u03bcm (false color) Identifiers MeSH D007107 FMA 9825 Anatomical terminology [ edit on Wikidata ] The immune system is a network of biological systems that protects an organism from diseases . It detects and responds to a wide variety of pathogens , such as viruses , bacteria , and parasites , as well as cancer cells and foreign objects, such as wood splinters \u2014distinguishing them from the organism's own healthy tissue . [ 1 ] Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered. Both use molecules and cells to perform their functions. Nearly all organisms have some kind of immune system. Bacteria have a rudimentary immune system in the form of enzymes that protect against viral infections. Other basic immune mechanisms evolved in ancient plants and animals (eukaryotes) and remain in their modern descendants. These mechanisms include phagocytosis , antimicrobial peptides called defensins , RNA interference , and the complement system . Jawed vertebrates , including humans, have a more sophisticated defense mechanism. For example, adaptive immunity provides the ability to adapt to recognize pathogens more efficiently ( somatic hypermutation ). This process creates an immunological memory , resulting in an enhanced response against subsequent encounters with that same pathogen. This mechanism of adaptive immunity is the fundamental basis of vaccination . Dysfunction of the immune system can cause autoimmune diseases , inflammatory diseases and cancer . Immunodeficiency occurs when the immune system is less active than normal, resulting in recurring and life-threatening infections. In humans, immunodeficiency can be the result of a genetic disease such as severe combined immunodeficiency , acquired conditions such as HIV / AIDS , or the use of immunosuppressive medication . Autoimmunity results from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include Hashimoto's thyroiditis , rheumatoid arthritis , diabetes mellitus type 1 , and systemic lupus erythematosus . Immunology covers the study of all aspects of the immune system. Layered defense The immune system protects its host from infection with layered defenses of increasing specificity. Physical barriers prevent pathogens such as bacteria and viruses from entering the organism. [ 2 ] If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response. Innate immune systems are found in all animals . [ 3 ] If pathogens successfully evade the innate response, vertebrates possess a second layer of protection, the adaptive immune system, which is activated by the innate response. [ 4 ] Here, the immune system adapts its response during an infection to improve its recognition of the pathogen. This improved response is then retained after the pathogen has been eliminated, in the form of an immunological memory , and allows the adaptive immune system to mount faster and stronger attacks each time this pathogen is encountered. [ 5 ] [ 6 ] Components of the immune system Innate immune system Adaptive immune system Response is non-specific Pathogen and antigen specific response Exposure leads to immediate maximal response Lag time between exposure and maximal response Cell-mediated and humoral components Cell-mediated and humoral components No immunological memory Exposure leads to immunological memory Found in nearly all forms of life Found only in jawed vertebrates Both innate and adaptive immunity depend on the ability of the immune system to distinguish between self and non-self molecules . In immunology, self molecules are components of an organism's body that can be distinguished from foreign substances by the immune system. [ 7 ] Conversely, non-self molecules are those recognized as foreign molecules. One class of non-self molecules are called antigens (originally named for being anti body gen erators) and are defined as substances that bind to specific immune receptors and elicit an immune response. [ 8 ] Surface barriers Several barriers protect organisms from infection, including mechanical, chemical, and biological barriers. The waxy cuticle of most leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs, and skin are examples of mechanical barriers that are the first line of defense against infection. [ 9 ] Organisms cannot be completely sealed from their environments, so systems act to protect body openings such as the lungs , intestines , and the genitourinary tract . In the lungs, coughing and sneezing mechanically eject pathogens and other irritants from the respiratory tract . The flushing action of tears and urine also mechanically expels pathogens, while mucus secreted by the respiratory and gastrointestinal tract serves to trap and entangle microorganisms . [ 10 ] Chemical barriers also protect against infection. The skin and respiratory tract secrete antimicrobial peptides such as the \u03b2- defensins . [ 11 ] Enzymes such as lysozyme and phospholipase A2 in saliva , tears, and breast milk are also antibacterials . [ 12 ] [ 13 ] Vaginal secretions serve as a chemical barrier following menarche , when they become slightly acidic , while semen contains defensins and zinc to kill pathogens. [ 14 ] [ 15 ] In the stomach , gastric acid serves as a chemical defense against ingested pathogens. [ 16 ] Within the genitourinary and gastrointestinal tracts, commensal flora serve as biological barriers by competing with pathogenic bacteria for food and space and, in some cases, changing the conditions in their environment, such as pH or available iron. As a result, the probability that pathogens will reach sufficient numbers to cause illness is reduced. [ 17 ] Innate immune system .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} Further information: Innate immune system Microorganisms or toxins that successfully enter an organism encounter the cells and mechanisms of the innate immune system. The innate response is usually triggered when microbes are identified by pattern recognition receptors , which recognize components that are conserved among broad groups of microorganisms, [ 18 ] or when damaged, injured or stressed cells send out alarm signals, many of which are recognized by the same receptors as those that recognize pathogens. [ 19 ] Innate immune defenses are non-specific, meaning these systems respond to pathogens in a generic way. [ 20 ] This system does not confer long-lasting immunity against a pathogen. The innate immune system is the dominant system of host defense in most organisms, [ 3 ] and the only one in plants. [ 21 ] Immune sensing Cells in the innate immune system use pattern recognition receptors to recognize molecular structures that are produced by pathogens. [ 22 ] They are proteins expressed, mainly, by cells of the innate immune system , such as dendritic cells, macrophages, monocytes, neutrophils, and epithelial cells, [ 20 ] [ 23 ] to identify two classes of molecules: pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens , and damage-associated molecular patterns (DAMPs), which are associated with components of hosts' cells that are released during cell damage or cell death. [ 24 ] Cells in the innate immune system have pattern recognition receptors that detect internal infection or cell damage. Three major classes of these \"cytosolic\" receptors are NOD\u2013like receptors , RIG (retinoic acid-inducible gene)-like receptors , and cytosolic DNA sensors. [ 25 ] Recognition of extracellular or endosomal PAMPs is mediated by transmembrane proteins known as toll-like receptors (TLRs). [ 26 ] TLRs share a typical structural motif, the leucine rich repeats (LRRs) , which give them a curved shape. [ 27 ] Toll-like receptors were first discovered in Drosophila and trigger the synthesis and secretion of cytokines and activation of other host defense programs that are necessary for both innate or adaptive immune responses. Ten toll-like receptors have been described in humans. [ 28 ] Innate immune cells A scanning electron microscope image of normal circulating human blood . One can see red blood cells , several knobby white blood cells , including lymphocytes , a monocyte , and a neutrophil , and many small disc-shaped platelets . Some leukocytes (white blood cells) act like independent, single-celled organisms and are the second arm of the innate immune system. The innate leukocytes include the \"professional\" phagocytes ( macrophages , neutrophils , and dendritic cells ). These cells identify and eliminate pathogens, either by attacking larger pathogens through contact or by engulfing and then killing microorganisms. The other cells involved in the innate response include innate lymphoid cells , mast cells , eosinophils , basophils , and natural killer cells . [ 29 ] Phagocytosis is an important feature of cellular innate immunity performed by cells called phagocytes that engulf pathogens or particles. Phagocytes generally patrol the body searching for pathogens, but can be called to specific locations by cytokines. [ 30 ] Once a pathogen has been engulfed by a phagocyte, it becomes trapped in an intracellular vesicle called a phagosome , which subsequently fuses with another vesicle called a lysosome to form a phagolysosome . The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome. [ 31 ] [ 32 ] Phagocytosis evolved as a means of acquiring nutrients , but this role was extended in phagocytes to include engulfment of pathogens as a defense mechanism. [ 33 ] Phagocytosis probably represents the oldest form of host defense, as phagocytes have been identified in both vertebrate and invertebrate animals. [ 34 ] Neutrophils and macrophages are phagocytes that travel throughout the body in pursuit of invading pathogens. [ 35 ] Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, representing 50% to 60% of total circulating leukocytes. [ 36 ] During the acute phase of inflammation , neutrophils migrate toward the site of inflammation in a process called chemotaxis and are usually the first cells to arrive at the scene of infection. Macrophages are versatile cells that reside within tissues and produce an array of chemicals including enzymes, complement proteins , and cytokines. They can also act as scavengers that rid the body of worn-out cells and other debris and as antigen-presenting cells (APCs) that activate the adaptive immune system. [ 37 ] Dendritic cells are phagocytes in tissues that are in contact with the external environment; therefore, they are located mainly in the skin, nose, lungs, stomach, and intestines. [ 38 ] They are named for their resemblance to neuronal dendrites , as both have many spine-like projections. Dendritic cells serve as a link between the bodily tissues and the innate and adaptive immune systems, as they present antigens to T cells , one of the key cell types of the adaptive immune system. [ 38 ] Granulocytes are leukocytes that have granules in their cytoplasm. In this category are neutrophils, mast cells, basophils, and eosinophils. Mast cells reside in connective tissues and mucous membranes and regulate the inflammatory response. [ 39 ] They are most often associated with allergy and anaphylaxis . [ 36 ] Basophils and eosinophils are related to neutrophils. They secrete chemical mediators that are involved in defending against parasites and play a role in allergic reactions, such as asthma . [ 40 ] Innate lymphoid cells (ILCs) are a group of innate immune cells that are derived from common lymphoid progenitor and belong to the lymphoid lineage . These cells are defined by the absence of antigen-specific B- or T-cell receptor (TCR) because of the lack of recombination activating gene . ILCs do not express myeloid or dendritic cell markers. [ 41 ] Natural killer cells (NK cells) are lymphocytes and a component of the innate immune system that does not directly attack invading microbes. [ 42 ] Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by a condition known as \"missing self\". This term describes cells with low levels of a cell-surface marker called MHC I ( major histocompatibility complex )\u2014a situation that can arise in viral infections of host cells. [ 43 ] Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens. Those MHC antigens are recognized by killer cell immunoglobulin receptors, which essentially put the brakes on NK cells. [ 44 ] Inflammation Further information: Inflammation Inflammation is one of the first responses of the immune system to infection. [ 45 ] The symptoms of inflammation are redness, swelling, heat, and pain, which are caused by increased blood flow into tissue. Inflammation is produced by eicosanoids and cytokines , which are released by injured or infected cells. Eicosanoids include prostaglandins that produce fever and the dilation of blood vessels associated with inflammation and leukotrienes that attract certain white blood cells (leukocytes). [ 46 ] [ 47 ] Common cytokines include interleukins that are responsible for communication between white blood cells; chemokines that promote chemotaxis ; and interferons that have antiviral effects, such as shutting down protein synthesis in the host cell. [ 48 ] Growth factors and cytotoxic factors may also be released. These cytokines and other chemicals recruit immune cells to the site of infection and promote the healing of any damaged tissue following the removal of pathogens. [ 49 ] The pattern-recognition receptors called inflammasomes are multiprotein complexes (consisting of an NLR, the adaptor protein ASC, and the effector molecule pro-caspase-1) that form in response to cytosolic PAMPs and DAMPs, whose function is to generate active forms of the inflammatory cytokines IL-1\u03b2 and IL-18. [ 50 ] Humoral defenses The complement system is a biochemical cascade that attacks the surfaces of foreign cells. It contains over 20 different proteins and is named for its ability to \"complement\" the killing of pathogens by antibodies . Complement is the major humoral component of the innate immune response. [ 51 ] [ 52 ] Many species have complement systems, including non- mammals like plants, fish, and some invertebrates . [ 53 ] In humans, this response is activated by complement binding to antibodies that have attached to these microbes or the binding of complement proteins to carbohydrates on the surfaces of microbes . This recognition signal triggers a rapid killing response. [ 54 ] The speed of the response is a result of signal amplification that occurs after sequential proteolytic activation of complement molecules, which are also proteases. After complement proteins initially bind to the microbe, they activate their protease activity, which in turn activates other complement proteases, and so on. This produces a catalytic cascade that amplifies the initial signal by controlled positive feedback . [ 55 ] The cascade results in the production of peptides that attract immune cells, increase vascular permeability , and opsonize (coat) the surface of a pathogen, marking it for destruction. This deposition of complement can also kill cells directly by disrupting their plasma membrane via the formation of a membrane attack complex . [ 51 ] Adaptive immune system Further information: Adaptive immune system Overview of the processes involved in the primary immune response The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory , where each pathogen is \"remembered\" by a signature antigen. [ 56 ] The adaptive immune response is antigen-specific and requires the recognition of specific \"non-self\" antigens during a process called antigen presentation . Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by \"memory cells\". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. [ 57 ] Recognition of antigen The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow . [ 58 ] B cells are involved in the humoral immune response , whereas T cells are involved in cell-mediated immune response . Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells and regulatory T cells only recognize antigens coupled to Class II MHC molecules. These two mechanisms of antigen presentation reflect the different roles of the two types of T cell. A third, minor subtype are the \u03b3\u03b4 T cells that recognize intact antigens that are not bound to MHC receptors. [ 59 ] The double-positive T cells are exposed to a wide variety of self-antigens in the thymus , in which iodine is necessary for its thymus development and activity. [ 60 ] In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing . Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. [ 61 ] Each lineage of B cell expresses a different antibody, so the complete set of B cell antigen receptors represent all the antibodies that the body can manufacture. [ 58 ] When B or T cells encounter their related antigens they multiply and many \"clones\" of the cells are produced that target the same antigen. This is called clonal selection . [ 62 ] Antigen presentation to T lymphocytes Both B cells and T cells carry receptor molecules that recognize specific targets. T cells recognize a \"non-self\" target, such as a pathogen, only after antigens (small fragments of the pathogen) have been processed and presented in combination with a \"self\" receptor called a major histocompatibility complex (MHC) molecule. [ 63 ] Cell mediated immunity Further information: Cell-mediated immunity There are two major subtypes of T cells: the killer T cell and the helper T cell . In addition there are regulatory T cells which have a role in modulating immune response. [ 64 ] Killer T cells Killer T cells are a sub-group of T cells that kill cells that are infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional. [ 65 ] As with B cells, each type of T cell recognizes a different antigen. Killer T cells are activated when their T-cell receptor binds to this specific antigen in a complex with the MHC Class I receptor of another cell. Recognition of this MHC:antigen complex is aided by a co-receptor on the T cell, called CD8 . The T cell then travels throughout the body in search of cells where the MHC I receptors bear this antigen. When an activated T cell contacts such cells, it releases cytotoxins , such as perforin , which form pores in the target cell's plasma membrane , allowing ions , water and toxins to enter. The entry of another toxin called granulysin (a protease) induces the target cell to undergo apoptosis . [ 66 ] T cell killing of host cells is particularly important in preventing the replication of viruses. T cell activation is tightly controlled and generally requires a very strong MHC/antigen activation signal, or additional activation signals provided by \"helper\" T cells (see below). [ 66 ] Helper T cells Activation of macrophage or B cell by T helper cell Helper T cells regulate both the innate and adaptive immune responses and help determine which immune responses the body makes to a particular pathogen. [ 67 ] [ 68 ] These cells have no cytotoxic activity and do not kill infected cells or clear pathogens directly. They instead control the immune response by directing other cells to perform these tasks. [ 69 ] Helper T cells express T cell receptors that recognize antigen bound to Class II MHC molecules. The MHC:antigen complex is also recognized by the helper cell's CD4 co-receptor, which recruits molecules inside the T cell (such as Lck ) that are responsible for the T cell's activation. Helper T cells have a weaker association with the MHC:antigen complex than observed for killer T cells, meaning many receptors (around 200\u2013300) on the helper T cell must be bound by an MHC:antigen to activate the helper cell, while killer T cells can be activated by engagement of a single MHC:antigen molecule. Helper T cell activation also requires longer duration of engagement with an antigen-presenting cell. [ 70 ] The activation of a resting helper T cell causes it to release cytokines that influence the activity of many cell types. Cytokine signals produced by helper T cells enhance the microbicidal function of macrophages and the activity of killer T cells. [ 71 ] In addition, helper T cell activation causes an upregulation of molecules expressed on the T cell's surface, such as CD40 ligand (also called CD154 ), which provide extra stimulatory signals typically required to activate antibody-producing B cells. [ 72 ] Gamma delta T cells Gamma delta T cells (\u03b3\u03b4 T cells) possess an alternative T-cell receptor (TCR) as opposed to CD4+ and CD8+ (\u03b1\u03b2) T cells and share the characteristics of helper T cells, cytotoxic T cells and NK cells. The conditions that produce responses from \u03b3\u03b4 T cells are not fully understood. Like other 'unconventional' T cell subsets bearing invariant TCRs, such as CD1d -restricted natural killer T cells , \u03b3\u03b4 T cells straddle the border between innate and adaptive immunity. [ 73 ] On one hand, \u03b3\u03b4 T cells are a component of adaptive immunity as they rearrange TCR genes to produce receptor diversity and can also develop a memory phenotype. On the other hand, the various subsets are also part of the innate immune system, as restricted TCR or NK receptors may be used as pattern recognition receptors . For example, large numbers of human V\u03b39/V\u03b42 T cells respond within hours to common molecules produced by microbes, and highly restricted V\u03b41+ T cells in epithelia respond to stressed epithelial cells. [ 59 ] Humoral immune response Further information: Humoral immunity An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen. [ 74 ] A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. [ 75 ] This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides . The B cell then displays these antigenic peptides on its surface MHC class II molecules. This combination of MHC and antigen attracts a matching helper T cell, which releases lymphokines and activates the B cell. [ 76 ] As the activated B cell then begins to divide , its offspring ( plasma cells ) secrete millions of copies of the antibody that recognizes this antigen. These antibodies circulate in blood plasma and lymph , bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes . Antibodies can also neutralize challenges directly, by binding to bacterial toxins or by interfering with the receptors that viruses and bacteria use to infect cells. [ 77 ] Newborn infants have no prior exposure to microbes and are particularly vulnerable to infection. Several layers of passive protection are provided by the mother. During pregnancy, a particular type of antibody, called IgG , is transported from mother to baby directly through the placenta , so human babies have high levels of antibodies even at birth, with the same range of antigen specificities as their mother. [ 78 ] Breast milk or colostrum also contains antibodies that are transferred to the gut of the infant and protect against bacterial infections until the newborn can synthesize its own antibodies. [ 79 ] This is passive immunity because the fetus does not actually make any memory cells or antibodies\u2014it only borrows them. This passive immunity is usually short-term, lasting from a few days up to several months. In medicine, protective passive immunity can also be transferred artificially from one individual to another. [ 80 ] Immunological memory Further information: Immunity (medical) When B cells and T cells are activated and begin to replicate, some of their offspring become long-lived memory cells. Throughout the lifetime of an animal, these memory cells remember each specific pathogen encountered and can mount a strong response if the pathogen is detected again. T-cells recognize pathogens by small protein-based infection signals, called antigens, that bind directly to T-cell surface receptors. [ 81 ] B-cells use the protein, immunoglobulin, to recognize pathogens by their antigens. [ 82 ] This is \"adaptive\" because it occurs during the lifetime of an individual as an adaptation to infection with that pathogen and prepares the immune system for future challenges. Immunological memory can be in the form of either passive short-term memory or active long-term memory. [ 83 ] Physiological regulation The time-course of an immune response begins with the initial pathogen encounter, (or initial vaccination) and leads to the formation and maintenance of active immunological memory. The immune system is involved in many aspects of physiological regulation in the body. The immune system interacts intimately with other systems, such as the endocrine [ 84 ] [ 85 ] and the nervous [ 86 ] [ 87 ] [ 88 ] systems. The immune system also plays a crucial role in embryogenesis (development of the embryo), as well as in tissue repair and regeneration . [ 89 ] Hormones Hormones can act as immunomodulators , altering the sensitivity of the immune system. For example, female sex hormones are known immunostimulators of both adaptive [ 90 ] and innate immune responses. [ 91 ] Some autoimmune diseases such as lupus erythematosus strike women preferentially, and their onset often coincides with puberty . By contrast, male sex hormones such as testosterone seem to be immunosuppressive . [ 92 ] Other hormones appear to regulate the immune system as well, most notably prolactin , growth hormone and vitamin D . [ 93 ] [ 94 ] Vitamin D Although early cellular studies suggested vitamin D might influence immune responses, more recent large-scale clinical trials and meta-analyses (2022\u20132024) have found that vitamin D supplementation can reduce the risk and severity of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis, and may modestly reduce the incidence of acute respiratory tract infections and improve tuberculosis outcomes. [ 95 ] [ 96 ] [ 97 ] A 2011 United States Institute of Medicine report stated that \"outcomes related to ... immune functioning and autoimmune disorders , and infections ... could not be linked reliably with calcium or vitamin D intake and were often conflicting.\" [ 98 ] : 5 Sleep and rest The immune system is affected by sleep and rest, and sleep deprivation is detrimental to immune function. [ 99 ] Complex feedback loops involving cytokines , such as interleukin-1 and tumor necrosis factor-\u03b1 produced in response to infection, appear to also play a role in the regulation of non-rapid eye movement ( NREM ) sleep. [ 100 ] Thus the immune response to infection may result in changes to the sleep cycle, including an increase in slow-wave sleep relative to rapid eye movement ( REM ) sleep. [ 101 ] In people with sleep deprivation, active immunizations may have a diminished effect and may result in lower antibody production, and a lower immune response, than would be noted in a well-rested individual. [ 102 ] [ 103 ] Additionally, proteins such as NFIL3 , which have been shown to be closely intertwined with both T-cell differentiation and circadian rhythms , can be affected through the disturbance of natural light and dark cycles through instances of sleep deprivation. These disruptions can lead to an increase in chronic conditions such as heart disease, chronic pain, and asthma. [ 104 ] In addition to the negative consequences of sleep deprivation, sleep and the intertwined circadian system have been shown to have strong regulatory effects on immunological functions affecting both innate and adaptive immunity. First, during the early slow-wave-sleep stage, a sudden drop in blood levels of cortisol , epinephrine , and norepinephrine causes increased blood levels of the hormones leptin , pituitary growth hormone , and prolactin . These signals induce a pro-inflammatory state through the production of the pro-inflammatory cytokines interleukin-1, interleukin-12 , TNF-alpha and IFN-gamma . These cytokines then stimulate immune functions such as immune cell activation, proliferation, and differentiation . During this time of a slowly evolving adaptive immune response, there is a peak in undifferentiated or less differentiated cells, like na\u00efve and central memory T cells. In addition to these effects, the milieu of hormones produced at this time (leptin, pituitary growth hormone, and prolactin) supports the interactions between APCs and T-cells, a shift of the T h 1/T h 2 cytokine balance towards one that supports T h 1, an increase in overall T h cell proliferation, and na\u00efve T cell migration to lymph nodes. This is also thought to support the formation of long-lasting immune memory through the initiation of Th1 immune responses. [ 105 ] During wake periods, differentiated effector cells, such as cytotoxic natural killer cells and CD45RA+ cytotoxic T lymphocytes, peak in numbers. Anti-inflammatory molecules, such as cortisol and catecholamines , also peak during awake active times. Inflammation can cause oxidative stress and the presence of melatonin during sleep times could counteract free radical production during this time. [ 105 ] [ 106 ] Physical exercise Physical exercise has a positive effect on the immune system and", "Renaissance European cultural period of the 14th to 17th centuries .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} This article is about the European Renaissance of the 15th and 16th centuries. For the earlier European Renaissance, see Renaissance of the 12th century . For other uses, see Renaissance (disambiguation) . Not to be confused with Reconnaissance . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCg\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCw\\\"/></a></span>\"}' id=\"mwDA\"/> .mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline 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.sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Renaissance The Birth of Venus (c. 1484\u20131486) by Botticelli Aspects Architecture Dance Fine arts Greek scholars Humanism Literature Magic Music Philosophy Science Technology Warfare Regions England France Germany Italy Poland Portugal Spain Scotland Northern Europe Low Countries History and study Age of Discovery Continuity thesis High Renaissance .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e The Renaissance ( .mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%} UK : / r \u026a \u02c8 n e\u026a s \u0259n s / rin- AY -s\u0259nss , US : / \u02c8 r \u025b n \u0259 s \u0251\u02d0 n s / \u24d8 REN -\u0259-sahnss ) [ 1 ] [ 2 ] {{cite web|url=http://www.etymonline.com/index.php?search=renaissance&searchmode=none |title=Online Etymology Dictionary: \\\"Renaissance\\\" |website=Etymonline.com |access-date=31 July 2009}}</ref>\"}},\"i\":0}}]}'> [ a ] is a European period of history and cultural movement , very roughly defined as covering the 14th through 17th centuries, [ 4 ] [ 5 ] though sometimes more narrowly defined for instance as only covering the 15th through 16th centuries. [ 6 ] It marked the transition from the Middle Ages to modernity and was characterized by the European rediscovery and revival of the literary, philosophical, and artistic achievements of classical antiquity . [ 5 ] Associated with great social change in most fields and disciplines, including art , architecture , politics, literature , exploration and science , the Renaissance was first centered in the Republic of Florence , then spread to the rest of Italy and later throughout Europe. The term rinascita ('rebirth') first appeared in Lives of the Artists ( c. 1550 ) by Giorgio Vasari , while the corresponding French word renaissance was adopted into English as the term for this period during the 1830s. [ 7 ] [ b ] The Renaissance's intellectual basis was founded in its version of humanism , derived from the concept of Roman humanitas and the rediscovery of classical Greek philosophy , such as that of Protagoras , who said that \"man is the measure of all things\". Although the invention of metal movable type sped the dissemination of ideas from the later 15th century, the changes of the Renaissance were not uniform across Europe: the first traces appear in Italy as early as the late 13th century, in particular with the writings of Dante and the paintings of Giotto . As a cultural movement, the Renaissance encompassed innovative flowering of literary Latin and an explosion of vernacular literatures , beginning with the 14th-century resurgence of learning based on classical sources, which contemporaries credited to Petrarch ; the development of linear perspective and other techniques of rendering a more natural reality in painting; and gradual but widespread educational reform . It saw myriad artistic developments and contributions from such polymaths as Leonardo da Vinci and Michelangelo , who inspired the term \"Renaissance man\". [ 8 ] [ 9 ] In politics, the Renaissance contributed to the development of the customs and conventions of diplomacy, and in science to an increased reliance on observation and inductive reasoning . The period also saw revolutions in other intellectual and social scientific pursuits, as well as the introduction of modern banking and the field of accounting . [ 10 ] Period The Renaissance period started during the crisis of the Late Middle Ages and conventionally ends with the waning of humanism , and the advent of the Reformation (1517), the Sack of Rome (1527) or the Counter-Reformation (1545), and in art, the Baroque period. It had a different period and characteristics in different regions, such as the Italian Renaissance, the Northern Renaissance , the Spanish Renaissance , etc. Proponents of a \"long Renaissance\" may put its beginning in the 14th century and its end in the 17th century. ''The Cambridge History of Seventeenth-Century Music: Volume 1'', p. 4, 2005, Cambridge University Press, [https://books.google.com/books?id=mHJvKVq0vXoC&pg=PA4 Google Books].</ref> Or between [[Petrarch]] and [[Jonathan Swift]], an even longer period.<ref>See Rosalie L. Colie, quoted in Hageman, Elizabeth H., in ''Women and Literature in Britain, 1500\u20131700'', p. 190, 1996, ed. Helen Wilcox, Cambridge University Press, {{ISBN|978-0521467773}}, [https://books.google.com/books?id=CVgF5yTALgAC&pg=PA190 Google Books].</ref> Another source dates it from 1350 to 1620.<ref>{{Cite web|title=Renaissance Era Dates|url=https://www.encyclopedia.com/literature-and-arts/language-linguistics-and-literary-terms/literature-general/renaissance#:~:text=Historians%20also%20argue%20over%20how,it%20lasted%20until%20about%201620.|website=encyclopedia.com}}</ref> \"}},\"i\":0}}]}'> [ c ] The traditional view focuses more on the Renaissance's early modern aspects and argues that it was a break from the past, but many historians today focus more on its medieval aspects and argue that it was an extension of the Middle Ages. [ 14 ] [ 15 ] Italian Renaissance The beginnings of the period\u2014the early Renaissance of the 15th century and the Italian Proto-Renaissance from around 1250 or 1300\u2014overlap considerably with the Late Middle Ages , conventionally dated to c. 1350\u20131500 , and the Middle Ages themselves were a long period filled with gradual changes, like the modern age; as a transitional period between both, the Renaissance has close similarities to both, especially the late and early sub-periods of either. The Renaissance began in Florence , one of the many states of Italy . [ 16 ] The Italian Renaissance concluded in 1527 when Holy Roman Emperor Charles V launched an assault on Rome during the war of the League of Cognac . Nevertheless, its impact endured in the art of renowned Italian painters like Tintoretto , Sofonisba Anguissola , and Paolo Veronese , who continued their work during the mid-to-late 16th century. [ 17 ] Various theories have been proposed to account for its origins and characteristics, focusing on a variety of factors, including Florence's social and civic peculiarities at the time: its political structure, the patronage of its dominant family, the Medici , [ 18 ] and the migration of Greek scholars and their texts to Italy following the fall of Constantinople to the Ottoman Empire . [ 19 ] [ 20 ] [ 21 ] Other major centers were Venice , Genoa , Milan , Rome during the Renaissance Papacy , and Naples . From Italy, the Renaissance spread throughout Europe and also to American, African and Asian territories ruled by the European colonial powers of the time or where Christian missionaries were active. The Renaissance has a long and complex historiography , and in line with general skepticism of discrete periodizations, there has been much debate among historians reacting to the 19th-century glorification of the \"Renaissance\" and individual cultural heroes as \"Renaissance men\", questioning the usefulness of Renaissance as a term and as a historical delineation. [ 22 ] Some observers have questioned whether the Renaissance was a cultural \"advance\" from the Middle Ages, instead seeing it as a period of pessimism and nostalgia for classical antiquity , [ 23 ] while social and economic historians, especially of the longue dur\u00e9e , have instead focused on the continuity between the two eras, [ 24 ] which are linked, as Panofsky observed, \"by a thousand ties\". [ 25 ] {{cite journal |last1=Trinkaus |first1=Charles |last2=Rabil |first2=Albert |last3=Purnell |first3=Frederick |title=Renaissance Ideas and the Idea of the Renaissance |journal=Journal of the History of Ideas |date=1990 |volume=51 |issue=4 |pages=667\u2013684 |doi=10.2307/2709652 |jstor=2709652 |url=https://www.jstor.org/stable/2709652 |issn=0022-5037|url-access=subscription }}</ref> \"}},\"i\":0}}]}'> [ d ] The word has also been extended to other historical and cultural movements, such as the Carolingian Renaissance (8th and 9th centuries), Ottonian Renaissance (10th and 11th century), and the Renaissance of the 12th century . [ 27 ] Overview The Renaissance was a cultural movement that profoundly affected European intellectual life in the early modern period . Beginning in Italy, and spreading to the rest of Europe by the 16th century, its influence was felt in art , architecture , philosophy , literature , music , science , technology , politics, religion, and other aspects of intellectual inquiry. Renaissance scholars employed the humanist method in study, and searched for realism and human emotion in art. [ 28 ] Renaissance humanists such as Poggio Bracciolini sought out in Europe's monastic libraries the Latin literary, historical, and oratorical texts of antiquity , while the fall of Constantinople (1453) generated a wave of \u00e9migr\u00e9 Greek scholars bringing precious manuscripts in ancient Greek , many of which had fallen into obscurity in the West. It was in their new focus on literary and historical texts that Renaissance scholars differed so markedly from the medieval scholars of the Renaissance of the 12th century , who had focused on studying Greek and Arabic works of natural sciences, philosophy, and mathematics, rather than on such cultural texts. [ citation needed ] Portrait of a Young Woman ( c. 1480 \u201385) ( Simonetta Vespucci ) by Sandro Botticelli In the revival of neoplatonism , Renaissance humanists did not reject Christianity ; on the contrary, many of the Renaissance's greatest works were devoted to it, and the Church patronized many works of Renaissance art. [ 29 ] But a subtle shift took place in the way that intellectuals approached religion that was reflected in many other areas of cultural life. [ 30 ] [ better source needed ] In addition, many Greek Christian works, including the Greek New Testament, were brought back from Byzantium to Western Europe and engaged Western scholars for the first time since late antiquity. This new engagement with Greek Christian works, and particularly the return to the original Greek of the New Testament promoted by humanists Lorenzo Valla and Erasmus , helped pave the way for the Reformation . [ citation needed ] Well after the first artistic return to classicism had been exemplified in the sculpture of Nicola Pisano , Florentine painters led by Masaccio strove to portray the human form realistically, developing techniques to render perspective and light more naturally. Political philosophers , most famously Niccol\u00f2 Machiavelli , sought to describe political life as it really was, that is, to understand it rationally. A critical contribution to Italian Renaissance humanism, Giovanni Pico della Mirandola wrote De hominis dignitate ( Oration on the Dignity of Man , 1486), a series of theses on philosophy, natural thought, faith, and magic defended against any opponent on the grounds of reason. In addition to studying classical Latin and Greek, Renaissance authors also began increasingly to use vernacular languages; combined with the introduction of the printing press , this allowed many more people access to books, especially the Bible. [ 31 ] In all, the Renaissance can be viewed as an attempt by intellectuals to study and improve the secular and worldly, both through the revival of ideas from antiquity and through novel approaches to thought. Political philosopher Hans Kohn describes it as an age where \"Men looked for new foundations\"; some like Erasmus and Thomas More envisioned new reformed spiritual foundations, others, in the words of Machiavelli , una lunga sperienza delle cose moderne ed una continua lezione delle antiche (a long experience with modern life and a continuous learning from antiquity). [ 32 ] Sociologist Rodney Stark plays down the Renaissance in favor of the earlier innovations of the Italian city-states in the High Middle Ages , which married responsive government, Christianity and the birth of capitalism . [ 33 ] This analysis argues that, whereas the great European states (France and Spain) were absolute monarchies , and others were under direct Church control, the independent city-republics of Italy took over the principles of capitalism invented on monastic estates and set off a vast unprecedented Commercial Revolution that preceded and financed the Renaissance. [ citation needed ] Historian Leon Poliakov offers a critical view in his seminal study of European racist thought: The Aryan Myth . According to Poliakov, the use of ethnic origin myths are first used by Renaissance humanists \"in the service of a new born chauvinism\". [ 34 ] [ 35 ] Origins Main article: Italian Renaissance View of Florence , birthplace of the Renaissance Many argue that the ideas characterizing the Renaissance had their origin in Florence at the turn of the 13th and 14th centuries, in particular with the writings of Dante Alighieri (1265\u20131321) and Petrarch (1304\u20131374), as well as the paintings of Giotto di Bondone (1267\u20131337). Some writers date the Renaissance quite precisely; one proposed starting point is 1401, when the rival geniuses Lorenzo Ghiberti and Filippo Brunelleschi competed for the contract to build the bronze doors for the Baptistery of the Florence Cathedral (Ghiberti won). [ 36 ] Others see more general competition between artists and polymaths such as Brunelleschi, Ghiberti, Donatello , and Masaccio for artistic commissions as sparking the creativity of the Renaissance. Yet it remains much debated why the Renaissance began in Italy, and why it began when it did. Accordingly, several theories have been put forward to explain its origins. Peter Rietbergen posits that various influential Proto-Renaissance movements started from roughly 1300 onwards across many regions of Europe . [ 37 ] Latin and Greek phases of Renaissance humanism See also: Greek scholars in the Renaissance and Transmission of the Greek Classics Coluccio Salutati In stark contrast to the High Middle Ages , when Latin scholars focused almost entirely on studying Greek and Arabic works of natural science, philosophy and mathematics, [ e ] Renaissance scholars were most interested in recovering and studying Latin and Greek literary, historical, and oratorical texts. Broadly speaking, this began in the 14th century with a Latin phase, when Renaissance scholars such as Petrarch , Coluccio Salutati (1331\u20131406), Niccol\u00f2 de' Niccoli (1364\u20131437), and Poggio Bracciolini (1380\u20131459) scoured the libraries of Europe in search of works by such Latin authors as Cicero , Lucretius , Livy , and Seneca . [ 38 ] By the early 15th century, the bulk of the surviving such Latin literature had been recovered; the Greek phase of Renaissance humanism was under way, as Western European scholars turned to recovering ancient Greek literary, historical, oratorical and theological texts. [ 39 ] Unlike with Latin texts, which had been preserved and studied in Western Europe since late antiquity, the study of ancient Greek texts was very limited in medieval Western Europe. Ancient Greek works on science, mathematics, and philosophy had been studied since the High Middle Ages in Western Europe and in the Islamic Golden Age (normally in translation), but Greek literary, oratorical and historical works (such as Homer , the Greek dramatists, Demosthenes and Thucydides ) were not studied in either the Latin or medieval Islamic worlds ; in the Middle Ages these sorts of texts were only studied by Byzantine scholars. Some argue that the Timurid Renaissance in Samarkand and Herat , whose magnificence toned with Florence as the center of a cultural rebirth, [ 40 ] [ 41 ] were linked to the Ottoman Empire , whose conquests led to the migration of Greek scholars to Italian cities. [ 19 ] [ 42 ] One of the greatest achievements of Renaissance scholars was to bring this entire class of Greek cultural works back into Western Europe for the first time since late antiquity. Muslim logicians, most notably Avicenna and Averroes , had inherited Greek ideas after they had invaded and conquered Egypt and the Levant . Their translations and commentaries on these ideas worked their way through the Arab West into Iberia and Sicily , which became important centers for this transmission of ideas. Between the 11th and 13th centuries, many schools dedicated to the translation of philosophical and scientific works from Classical Arabic to Medieval Latin were established in Iberia, most notably the Toledo School of Translators . This work of translation from Islamic culture, though largely unplanned and disorganized, constituted one of the greatest transmissions of ideas in history. [ 43 ] The movement to reintegrate the regular study of Greek literary, historical, oratorical, and theological texts back into the Western European curriculum is usually dated to the 1396 invitation from Coluccio Salutati to the Byzantine diplomat and scholar Manuel Chrysoloras (c. 1355\u20131415) to teach Greek in Florence. [ 44 ] This legacy was continued by a number of expatriate Greek scholars, from Basilios Bessarion to Leo Allatius . Social and political structures in Italy A political map of the Italian Peninsula c. 1494 The unique political structures of Italy during the Late Middle Ages have led some to theorize that its unusual social climate allowed the emergence of a rare cultural efflorescence. Italy did not exist as a political entity in the early modern period. Instead, it was divided into smaller city-states and territories: the Neapolitans controlled the south, the Florentines and the Romans at the center, the Milanese and the Genoese to the north and west respectively, and the Venetians to the north east. 15th-century Italy was one of the most urbanized areas in Europe. [ 45 ] Many of its cities stood among the ruins of ancient Roman buildings; it seems likely that the classical nature of the Renaissance was linked to its origin in the Roman Empire's heartland. [ 46 ] Historian and political philosopher Quentin Skinner points out that Otto of Freising (c. 1114\u20131158), a German bishop visiting north Italy during the 12th century, noticed a widespread new form of political and social organization, observing that Italy appeared to have exited from feudalism so that its society was based on merchants and commerce. Linked to this was anti-monarchical thinking, represented in the famous early Renaissance fresco cycle The Allegory of Good and Bad Government by Ambrogio Lorenzetti (painted 1338\u20131340), whose strong message is about the virtues of fairness, justice, republicanism and good administration. Holding both Church and Empire at bay, these city republics were devoted to notions of liberty. Skinner reports that there were many defences of liberty such as the Matteo Palmieri (1406\u20131475) celebration of Florentine genius not only in art, sculpture and architecture, but \"the remarkable efflorescence of moral, social and political philosophy that occurred in Florence at the same time\". [ 47 ] Even cities and states beyond central Italy, such as the Republic of Florence at this time, were also notable for their merchant republics , especially the Republic of Venice. Although in practice these were oligarchical , and bore little resemblance to a modern democracy , they did have democratic features and were responsive states, with forms of participation in governance and belief in liberty. [ 47 ] [ 48 ] [ 49 ] The relative political freedom they afforded was conducive to academic and artistic advancement. [ 50 ] Likewise, the position of Italian cities such as Venice as great trading centres made them intellectual crossroads. Merchants brought with them ideas from far corners of the globe, particularly the Levant . Venice was Europe's gateway to trade with the East, and a producer of fine glass , while Florence was a capital of textiles. The wealth such business brought to Italy meant large public and private artistic projects could be commissioned and individuals had more leisure time for study. [ 50 ] Black Death Main article: Black Death Pieter Bruegel 's The Triumph of Death ( c. 1562 ) reflects the social upheaval and terror that followed the plague that devastated medieval Europe. One theory that has been advanced is that the devastation in Florence caused by the Black Death , which hit Europe between 1348 and 1350, resulted in a shift in the world view of people in 14th century Italy. Italy was particularly badly hit by the plague, and it has been speculated that the resulting familiarity with death caused thinkers to dwell more on their lives on Earth, rather than on spirituality and the afterlife . [ 51 ] It has also been argued that the Black Death prompted a new wave of piety, manifested in the sponsorship of religious works of art. [ 52 ] However, this does not fully explain why the Renaissance occurred specifically in Italy in the 14th century. The Black Death was a pandemic that affected all of Europe in the ways described, not only Italy. The Renaissance's emergence in Italy was most likely the result of the complex interaction of the above factors. [ 22 ] The plague was carried by fleas on sailing vessels returning from the ports of Asia, spreading quickly due to lack of proper sanitation: the population of England , then about 4.2 million, lost 1.4 million people to the bubonic plague . Florence's population was nearly halved in the year 1348. As a result of the decimation in the populace the value of the working class increased, and commoners came to enjoy more freedom. To answer the increased need for labor, workers traveled in search of the most favorable position economically. [ 53 ] The demographic decline due to the plague had economic consequences: the prices of food dropped and land values declined by 30\u201340% in most parts of Europe between 1350 and 1400. [ 54 ] Landholders faced a great loss, but for ordinary men and women it was a windfall. The survivors of the plague found not only that the prices of food were cheaper but also that lands were more abundant, and many of them inherited property from their dead relatives. The spread of disease was significantly more rampant in areas of poverty. Epidemics ravaged cities, particularly children. Plagues were easily spread by lice, unsanitary drinking water, armies, or by poor sanitation. Children were hit the hardest because many diseases, such as typhus and congenital syphilis , target the immune system, leaving young children without a fighting chance. Children in city dwellings were more affected by the spread of disease than the children of the wealthy. [ 55 ] The Black Death caused greater upheaval to Florence's social and political structure than later epidemics. Despite a significant number of deaths among members of the ruling classes, the government of Florence continued to function during this period. Formal meetings of elected representatives were suspended during the height of the epidemic due to the chaotic conditions in the city, but a small group of officials was appointed to conduct the affairs of the city, which ensured continuity of government. [ 56 ] Cultural conditions in Florence See also: Florentine Renaissance art Lorenzo de' Medici , ruler of Florence and patron of arts (portrait by Vasari ) It has long been a matter of debate why the Renaissance began in Florence , and not elsewhere in Italy. Scholars have noted several features unique to Florentine cultural life that may have caused such a cultural movement. Many have emphasized the role played by the Medici , a banking family and later ducal ruling house , in patronizing and stimulating the arts. Some historians have postulated that Florence was the birthplace of the Renaissance as a result of luck, i.e., because \" Great Men \" were born there by chance: [ 57 ] Leonardo, Botticelli and Michelangelo were all born in Tuscany . Arguing that such chance seems improbable, other historians have contended that these \"Great Men\" were only able to rise to prominence because of the prevailing cultural conditions at the time. [ 58 ] Lorenzo de' Medici (1449\u20131492) was the catalyst for an enormous amount of arts patronage, encouraging his countrymen to commission works from the leading artists of Florence, including Leonardo da Vinci , Sandro Botticelli , and Michelangelo Buonarroti . [ 18 ] Works by Neri di Bicci , Botticelli, Leonardo, and Filippino Lippi had been commissioned additionally by the Convent of San Donato in Scopeto in Florence. [ 59 ] The Renaissance was certainly underway before Lorenzo de' Medici came to power \u2013 indeed, before the Medici family itself achieved hegemony in Florentine society. Characteristics Humanism Main articles: Renaissance humanism , Renaissance humanism in Northern Europe , and List of Renaissance humanists In some ways, Renaissance humanism was not a philosophy but a method of learning. In contrast to the medieval scholastic mode, which focused on resolving contradictions between authors, Renaissance humanists would study ancient texts in their original languages and appraise them through a combination of reasoning and empirical evidence . Humanist education was based on the programme of Studia Humanitatis , the study of five humanities: poetry , grammar , history , moral philosophy , and rhetoric . Although historians have sometimes struggled to define humanism precisely, most have settled on \"a middle of the road definition... the movement to recover, interpret, and assimilate the language, literature, learning and values of ancient Greece and Rome\". [ 60 ] Above all, humanists asserted \"the genius of man ... the unique and extraordinary ability of the human mind\". [ 61 ] Giovanni Pico della Mirandola , writer of the famous Oration on the Dignity of Man , which has been called the \"Manifesto of the Renaissance\" [ 62 ] Humanist scholars shaped the intellectual landscape throughout the early modern period. Political philosophers such as Niccol\u00f2 Machiavelli and Thomas More revived the ideas of Greek and Roman thinkers and applied them in critiques of contemporary government, following the Islamic steps of Ibn Khaldun . [ 63 ] [ 64 ] Pico della Mirandola wrote the \"manifesto\" of the Renaissance, the Oration on the Dignity of Man , a vibrant defence of thinking. [ citation needed ] Matteo Palmieri (1406\u20131475), another humanist, is most known for his work Della vita civile (\"On Civic Life\"; printed 1528), which advocated civic humanism , and for his influence in refining the Tuscan vernacular to the same level as Latin. Palmieri drew on Roman philosophers and theorists, especially Cicero , who, like Palmieri, lived an active public life as a citizen and official, as well as a theorist and philosopher and also Quintilian . Perhaps the most succinct expression of his perspective on humanism is in a 1465 poetic work La citt\u00e0 di vita , but an earlier work, Della vita civile , is more wide-ranging. Composed as a series of dialogues set in a country house in the Mugello countryside outside Florence during the plague of 1430, Palmieri expounds on the qualities of the ideal citizen. The dialogues include ideas about how children develop mentally and physically, how citizens can conduct themselves morally, how citizens and states can ensure probity in public life, and an important debate on the difference between that which is pragmatically useful and that which is honest. [ citation needed ] The humanists believed that it is important to transcend to the afterlife with a perfect mind and body, which could be attained with education. The purpose of humanism was to create a universal man whose person combined intellectual and physical excellence and who was capable of functioning honorably in virtually any situation. [ 65 ] This ideology was referred to as the uomo universale , an ancient Greco-Roman ideal. Education during the Renaissance was mainly composed of ancient literature and history as it was thought that the classics provided moral instruction and an intensive understanding of human behavior. Humanism and libraries A unique characteristic of some Renaissance libraries is that they were open to the public. These libraries were places where ideas were exchanged and where scholarship and reading were considered both pleasurable and beneficial to the mind and soul. As freethinking was a hallmark of the age, many libraries contained a wide range of writers. Classical texts could be found alongside humanist writings. These informal associations of intellectuals profoundly influenced Renaissance culture. An essential tool of Renaissance librarianship was the catalog that listed, described, and classified a library's books. [ 66 ] Some of the richest \"bibliophiles\" built libraries as temples to books and knowledge. A number of libraries appeared as manifestations of immense wealth joined with a love of books. In some cases, cultivated library builders were also committed to offering others the opportunity to use their collections. Prominent aristocrats and princes of the Church created great libraries for the use of their courts, called \"court libraries\", and were housed in lavishly designed monumental buildings decorated with ornate woodwork, and the walls adorned with frescoes (Murray, Stuart A.P.). Art Main article: Renaissance art Renaissance art marks a cultural rebirth at the close of the Middle Ages and rise of the Modern world. One of the distinguishing features of Renaissance art was its development of highly realistic linear perspective. Giotto di Bondone (1267\u20131337) is credited with", "Plate tectonics Movement of Earth's lithosphere .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} \"Tectonic plates\" redirects here; not to be confused with Tectonic Plates (film) . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> Map of Earth's 16 principal tectonic plates [ 1 ] Convergent : .mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{} Collision zone Subduction zone Divergent : Extension zone Spreading centre Transform : Dextral transform Sinistral transform .mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output 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a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Part of a series on Geology Index Outline Category Glossary History ( Timeline ) Key components Minerals Rock ( Igneous Sedimentary Metamorphic ) Sediment Plate tectonics Strata Weathering Erosion Geologic time scale Laws, principles, theories Stratigraphic principles Principle of original horizontality Law of superposition Principle of lateral continuity Principle of cross-cutting relationships Principle of faunal succession Principle of inclusions and 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tectonics Tectonics Volcanism Gravity Geodesy Geoid Physical geodesy Magnetism Earth's magnetic field Geomagnetic reversal Magnetosphere Paleomagnetism Solar wind Waves Seismology Spectroscopy Vibration Geophysicists Aki Alfven Anderson Benioff Bowie Dziewonski Forbes Eotvos Gilbert Gutenberg Heiskanen Hotine von Humboldt Jeffreys Kanamori Love Matthews McKenzie Mercalli Molodenskii Munk Press Richter Turcotte Van Allen Vanicek Vening Meinesz Wegener Wilson v t e Plate tectonics ( from Latin tectonicus , from Ancient Greek \u03c4\u03b5\u03ba\u03c4\u03bf\u03bd\u03b9\u03ba\u03cc\u03c2 ( tektonik\u00f3s ) ' pertaining to building ' ) [ 2 ] is the scientific theory that Earth 's lithosphere comprises a number of large tectonic plates , which have been slowly moving since 3\u20134 billion years ago. [ 3 ] [ 4 ] [ 5 ] The model builds on the concept of continental drift , an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by geoscientists after seafloor spreading was validated in the mid- to late 1960s. The processes that result in plates and shape Earth's crust are called tectonics . Earth's lithosphere, the rigid outer shell of the planet including the crust and upper mantle , is fractured into seven or eight major plates (depending on how they are defined) and many minor plates or \"platelets\". Where the plates meet, their relative motion determines the type of plate boundary (or fault ): convergent , divergent , or transform . The relative movement of the plates typically ranges from zero to 10 cm annually. [ 6 ] Faults tend to be geologically active, with earthquakes , volcanic activity , mountain-building , and oceanic trench formation. Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along convergent plate boundaries , the process of subduction carries the edge of one plate down under the other plate and into the mantle . This process reduces the total surface area (crust) of Earth. The lost surface is balanced by the formation of new oceanic crust along divergent margins by seafloor spreading, keeping the total surface area constant in a tectonic \"conveyor belt\". While Earth is the only planet known to currently have active plate tectonics, evidence suggests that other planets and moons have experienced or exhibit forms of tectonic activity. Jupiter's moon Europa shows signs of ice crustal plates moving and interacting, similar to Earth's plate tectonics. [ 7 ] Mars and Venus are thought to have had tectonic activity in the past, though not of the same form as Earth. [ 8 ] Tectonic plates are relatively rigid and float across the ductile asthenosphere beneath. Lateral density variations in the mantle result in convection currents, the slow creeping motion of Earth's solid mantle. At a seafloor spreading ridge , plates move away from the ridge, which is a topographic high, and the newly formed crust cools as it moves away, increasing its density and contributing to the motion. At a subduction zone, the relatively cold, dense oceanic crust sinks down into the mantle, forming the downward convecting limb of a mantle cell , [ 9 ] which is the strongest driver of plate motion. [ 10 ] [ 11 ] The relative importance and interaction of other proposed factors such as active convection, upwelling inside the mantle, and tidal drag of the Moon are subjects of debate. .mw-parser-output .toclimit-2 .toclevel-1 ul,.mw-parser-output .toclimit-3 .toclevel-2 ul,.mw-parser-output .toclimit-4 .toclevel-3 ul,.mw-parser-output .toclimit-5 .toclevel-4 ul,.mw-parser-output .toclimit-6 .toclevel-5 ul,.mw-parser-output .toclimit-7 .toclevel-6 ul{display:none} Key principles .mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}} This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. ( July 2021 ) ( Learn how and when to remove this message ) The outer layers of Earth are divided into the lithosphere and asthenosphere . The division is based on differences in mechanical properties and in the method for the transfer of heat . The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction , whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confused with the chemical subdivision of these same layers into the mantle (comprising both the asthenosphere and the mantle portion of the lithosphere) and the crust: a given piece of mantle may be part of the lithosphere or the asthenosphere at different times depending on its temperature and pressure. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates , which ride on the viscoelastic asthenosphere. Plate motions range from 10 to 40 millimetres per year (0.4 to 1.6 in/year) at the Mid-Atlantic Ridge (about as fast as fingernails grow), to about 160 millimetres per year (6.3 in/year) for the Nazca plate (about as fast as hair grows). [ 12 ] [ 13 ] Tectonic lithospheric plates consist of lithospheric mantle overlain by one or two types of crustal material: oceanic crust (in older texts called sima from silicon and magnesium ) and continental crust ( sial from silicon and aluminium ). The distinction between oceanic crust and continental crust is based on their modes of formation. Oceanic crust is formed at sea-floor spreading centers. Continental crust is formed through arc volcanism and accretion of terranes through plate tectonic processes. Oceanic crust is denser than continental crust because it has less silicon and more of the heavier elements than continental crust . [ 14 ] [ 15 ] As a result of this density difference, oceanic crust generally lies below sea level , while continental crust buoyantly projects above sea level. Average oceanic lithosphere is typically 100 km (62 mi) thick. [ 16 ] Its thickness is a function of its age. As time passes, it cools by conducting heat from below, and releasing it radiatively into space. The adjacent mantle below is cooled by this process and added to its base. Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it was formed. For a typical distance that oceanic lithosphere must travel before being subducted, the thickness varies from about 6 km (4 mi) thick at mid-ocean ridges to greater than 100 km (62 mi) at subduction zones. For shorter or longer distances, the subduction zone, and therefore also the mean, thickness becomes smaller or larger, respectively. [ 17 ] Continental lithosphere is typically about 200 km (120 mi) thick, though this varies considerably between basins, mountain ranges, and stable cratonic interiors of continents. The location where two plates meet is called a plate boundary . Plate boundaries are where geological events occur, such as earthquakes and the creation of topographic features such as mountains , volcanoes , mid-ocean ridges , and oceanic trenches . The vast majority of the world's active volcanoes occur along plate boundaries, with the Pacific plate's Ring of Fire being the most active and widely known. Some volcanoes occur in the interiors of plates, and these have been variously attributed to internal plate deformation [ 18 ] and to mantle plumes. Tectonic plates may include continental crust or oceanic crust, or both. For example, the African plate includes the continent and parts of the floor of the Atlantic and Indian Oceans. Some pieces of oceanic crust, known as ophiolites , failed to be subducted under continental crust at destructive plate boundaries; instead, these oceanic crustal fragments were pushed upward and were preserved within continental crust. Types of plate boundaries Main article: List of tectonic plate interactions Three types of plate boundaries exist, [ 19 ] characterized by the way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are: [ 20 ] [ 21 ] Divergent boundary Divergent boundaries ( constructive boundaries or extensional boundaries ). These are where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin , e.g. the Mid-Atlantic Ridge and East Pacific Rise . As the ocean plate splits, the ridge forms at the spreading center, the ocean basin expands, and finally, the plate area increases causing many small volcanoes and/or shallow earthquakes. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin, e.g., the East African Rift , the Baikal Rift , the West Antarctic Rift , the Rio Grande Rift . Convergent boundary Convergent boundaries ( destructive boundaries or active margins ) occur where two plates slide toward each other to form either a subduction zone (one plate moving underneath the other) or a continental collision . Subduction zones are of two types: ocean-to-continent subduction, where the dense oceanic lithosphere plunges beneath the less dense continent, or ocean-to-ocean subduction where older, cooler, denser oceanic crust slips beneath less dense oceanic crust. Deep marine trenches are typically associated with subduction zones, and the basins that develop along the active boundary are often called \"foreland basins\". Earthquakes trace the path of the downward-moving plate as it descends into asthenosphere, a trench forms, and as the subducted plate is heated it releases volatiles, mostly water from hydrous minerals , into the surrounding mantle. The addition of water lowers the melting point of the mantle material above the subducting slab, causing it to melt. The magma that results typically leads to volcanism. [ 22 ] At zones of ocean-to-ocean subduction a deep trench forms in an arc shape. The upper mantle of the subducted plate then heats and magma rises to form curving chains of volcanic islands e.g. the Aleutian Islands , the Mariana Islands , the Japanese island arc . At zones of ocean-to-continent subduction mountain ranges form, e.g. the Andes , the Cascade Range . At continental collision zones there are two masses of continental lithosphere converging. Since they are of similar density, neither is subducted. The plate edges are compressed, folded, and uplifted forming mountain ranges, e.g. Himalayas and Alps . Closure of ocean basins can occur at continent-to-continent boundaries. Transform boundary Transform boundaries ( conservative boundaries or strike-slip boundaries ) occur where plates are neither created nor destroyed. Instead, two plates slide, or perhaps more accurately grind past each other, along transform faults . The relative motion of the two plates is either sinistral (left side toward the observer) or dextral (right side toward the observer). Transform faults occur across a spreading center. Strong earthquakes can occur along a fault. The San Andreas Fault in California is an example of a transform boundary exhibiting dextral motion. Other plate boundary zones occur where the effects of the interactions are unclear, and the boundaries, usually occurring along a broad belt, are not well defined and may show various types of movements in different episodes. Driving forces of plate motion Plate motion based on Global Positioning System (GPS) satellite data from NASA JPL . Each red dot is a measuring point and vectors show direction and magnitude of motion. Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere . Dissipation of heat from the mantle is the original source of the energy required to drive plate tectonics through convection or large scale upwelling and doming. As a consequence, a powerful source generating plate motion is the excess density of the oceanic lithosphere sinking in subduction zones. When the new crust forms at mid-ocean ridges, this oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes denser with age as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows it to sink into the deep mantle at subduction zones, providing most of the driving force for plate movement. The weakness of the asthenosphere allows the tectonic plates to move easily towards a subduction zone. [ 23 ] Driving forces related to mantle dynamics Main article: Mantle convection For much of the first quarter of the 20th century, the leading theory of the driving force behind tectonic plate motions envisaged large scale convection currents in the upper mantle, which can be transmitted through the asthenosphere. This theory was launched by Arthur Holmes and some forerunners in the 1930s [ 24 ] and was immediately recognized as the solution for the acceptance of the theory as originally discussed in the papers of Alfred Wegener in the early years of the 20th century. However, despite its acceptance, it was long debated in the scientific community because the leading theory still envisaged a static Earth without moving continents up until the major breakthroughs of the early sixties. Two- and three-dimensional imaging of Earth's interior ( seismic tomography ) shows a varying lateral density distribution throughout the mantle. Such density variations can be material (from rock chemistry), mineral (from variations in mineral structures), or thermal (through thermal expansion and contraction from heat energy). The manifestation of this varying lateral density is mantle convection from buoyancy forces. [ 25 ] How mantle convection directly and indirectly relates to plate motion is a matter of ongoing study and discussion in geodynamics . Somehow, this energy must be transferred to the lithosphere for tectonic plates to move. There are essentially two main types of mechanisms that are thought to exist related to the dynamics of the mantle that influence plate motion which are primary (through the large scale convection cells) or secondary. The secondary mechanisms view plate motion driven by friction between the convection currents in the asthenosphere and the more rigid overlying lithosphere. This is due to the inflow of mantle material related to the downward pull on plates in subduction zones at ocean trenches. Slab pull may occur in a geodynamic setting where basal tractions continue to act on the plate as it dives into the mantle (although perhaps to a greater extent acting on both the under and upper side of the slab). Furthermore, slabs that are broken off and sink into the mantle can cause viscous mantle forces driving plates through slab suction. Plume tectonics In the theory of plume tectonics followed by numerous researchers during the 1990s, a modified concept of mantle convection currents is used. It asserts that super plumes rise from the deeper mantle and are the drivers or substitutes of the major convection cells. These ideas find their roots in the early 1930s in the works of Beloussov and van Bemmelen , which were initially opposed to plate tectonics and placed the mechanism in a fixed frame of vertical movements. Van Bemmelen later modified the concept in his \"Undation Models\" and used \"Mantle Blisters\" as the driving force for horizontal movements, invoking gravitational forces away from the regional crustal doming. [ 26 ] [ 27 ] The theories find resonance in the modern theories which envisage hot spots or mantle plumes which remain fixed and are overridden by oceanic and continental lithosphere plates over time and leave their traces in the geological record (though these phenomena are not invoked as real driving mechanisms, but rather as modulators). The mechanism is still advocated to explain the break-up of supercontinents during specific geological epochs. [ 28 ] It has followers amongst the scientists involved in the theory of Earth expansion . [ 29 ] [ 30 ] [ 31 ] Surge tectonics Another theory is that the mantle flows neither in cells nor large plumes but rather as a series of channels just below Earth's crust, which then provide basal friction to the lithosphere. This theory, called \"surge tectonics\", was popularized during the 1980s and 1990s. [ 32 ] Recent research, based on three-dimensional computer modelling, suggests that plate geometry is governed by a feedback between mantle convection patterns and the strength of the lithosphere. [ 33 ] Driving forces related to gravity Forces related to gravity are invoked as secondary phenomena within the framework of a more general driving mechanism such as the various forms of mantle dynamics described above. In modern views, gravity is invoked as the major driving force, through slab pull along subduction zones. Gravitational sliding away from a spreading ridge is one of the proposed driving forces: plate motion is driven by the higher elevation of plates at ocean ridges. [ 34 ] [ 35 ] As oceanic lithosphere is formed at spreading ridges from hot mantle material, it gradually cools and thickens with age (and thus adds distance from the ridge). Cool oceanic lithosphere is significantly denser than the hot mantle material from which it is derived and so with increasing thickness it gradually subsides into the mantle to compensate the greater load. The result is a slight lateral incline with increased distance from the ridge axis. This force is regarded as a secondary force and is often referred to as \" ridge push \". This is a misnomer as there is no force \"pushing\" horizontally, indeed tensional features are dominant along ridges. It is more accurate to refer to this mechanism as \"gravitational sliding\", since the topography across the whole plate can vary considerably and spreading ridges are only the most prominent feature. Other mechanisms generating this gravitational secondary force include flexural bulging of the lithosphere before it dives underneath an adjacent plate, producing a clear topographical feature that can offset, or at least affect, the influence of topographical ocean ridges. Mantle plumes and hot spots are also postulated to impinge on the underside of tectonic plates. Slab pull : Scientific opinion is that the asthenosphere is insufficiently competent or rigid to directly cause motion by friction along the base of the lithosphere. Slab pull is therefore most widely thought to be the greatest force acting on the plates. In this understanding, plate motion is mostly driven by the weight of cold, dense plates sinking into the mantle at trenches. [ 11 ] Recent models indicate that trench suction plays an important role as well. However, the fact that the North American plate is nowhere being subducted, although it is in motion, presents a problem. The same holds for the African, Eurasian , and Antarctic plates. Gravitational sliding away from mantle doming: According to older theories, one of the driving mechanisms of the plates is the existence of large scale asthenosphere/mantle domes which cause the gravitational sliding of lithosphere plates away from them (see the paragraph on Mantle Mechanisms). This gravitational sliding represents a secondary phenomenon of this basically vertically oriented mechanism. It finds its roots in the Undation Model of van Bemmelen . This can act on various scales, from the small scale of one island arc up to the larger scale of an entire ocean basin. [ 34 ] [ 35 ] [ 28 ] Driving forces related to Earth rotation Alfred Wegener , being a meteorologist , had proposed tidal forces and centrifugal forces as the main driving mechanisms behind continental drift ; however, these forces were considered far too small to cause continental motion as the concept was of continents plowing through oceanic crust. [ 36 ] Therefore, Wegener later changed his position and asserted that convection currents are the main driving force of plate tectonics in the last edition of his book in 1929. However, in the plate tectonics context (accepted since the seafloor spreading proposals of Heezen, Hess, Dietz, Morley, Vine, and Matthews (see below) during the early 1960s), the oceanic crust is suggested to be in motion with the continents, which caused the proposals related to Earth rotation to be reconsidered. In more recent literature, these driving forces are: Tidal drag due to the gravitational force the Moon (and the Sun ) exerts on the crust of Earth. [ 37 ] Global deformation of the geoid due to small displacements of the rotational pole with respect to Earth's crust. Other smaller deformation effects of the crust due to wobbles and spin movements of Earth's rotation on a smaller timescale. Forces that are small and generally negligible are: The Coriolis force . [ 38 ] [ 39 ] The centrifugal force , which is treated as a slight modification of gravity. [ 38 ] [ 39 ] : 249 For these mechanisms to be overall valid, systematic relationships should exist all over the globe between the orientation and kinematics of deformation and the geographical latitudinal and longitudinal grid of Earth itself. Systematic relations studies in the second half of the nineteenth century and the first half of the twentieth century underlined exactly the opposite: that the plates had not moved in time, that the deformation grid was fixed with respect to Earth's equator and axis, and that gravitational driving forces were generally acting vertically and caused only local horizontal movements (the so-called pre-plate tectonic, \"fixist theories\"). Later studies (discussed below on this page), therefore, invoked many of the relationships recognized during this pre-plate tectonics period to support their theories (see reviews of these various mechanisms related to Earth rotation in the work of van Dijk and collaborators). [ 40 ] Possible tidal effect on plate tectonics See also: Tidal triggering of earthquakes Of the many forces discussed above, tidal force is still highly debated and defended as a possible principal driving force of plate tectonics. The other forces are only used in global geodynamic models not using plate tectonics concepts (therefore beyond the discussions treated in this section) or proposed as minor modulations within the overall plate tectonics model. In 1973, George W. Moore [ 41 ] of the USGS and R. C. Bostrom [ 42 ] presented evidence for a general westward drift of Earth's lithosphere with respect to the mantle, based on the steepness of the subduction zones (shallow dipping towards the east, steeply dipping towards the west). They concluded that tidal forces (the tidal lag or \"friction\") caused by Earth's rotation and the forces acting upon it by the Moon are a driving force for plate tectonics. As Earth spins eastward beneath the Moon, the Moon's gravity ever so slightly pulls Earth's surface layer back westward, just as proposed by Alfred Wegener (see above). Since 1990 this theory has been mainly advocated by Doglioni and co-workers ( Doglioni 1990 ) , such as in a more recent 2006 study, [ 43 ] where scientists reviewed and advocated these ideas. It has been suggested in Lovett (2006) that this observation may also explain why Venus and Mars have no plate tectonics, as Venus has no moon and Mars' moons are too small to have significant tidal effects on the planet. In a paper by Torsvik et al., [ 44 ] it was suggested that, on the other hand, it can easily be observed that many plates are moving north and eastward, and that the dominantly westward motion of the Pacific Ocean basins derives simply from the eastward bias of the Pacific spreading center (which is not a predicted manifestation of such lunar forces). In the same paper the authors admit, however, that relative to the lower mantle, there is a slight westward component in the motions of all the plates. They demonstrated though that the westward drift, seen only for the past 30 Ma, is attributed to the increased dominance of the steadily growing and accelerating Pacific plate. The debate is still open, and a 2022 paper by Hofmeister et al. [ 45 ] revived the idea of the interaction between Earth's rotation and the Moon as the main driving force for plate movement. Role of water [</span>icon<span typeof=\\\"mw:Entity\\\" id=\\\"mwAf0\\\">]</span>\",\"txt\":\"[icon]\"}]]}'> This section needs expansion . You can help by making an edit request adding missing information . ( October 2025 ) The role of water has been proposed to be crucial in plate tectonics on Earth. [ 46 ] [ 47 ] [ 48 ] Relative significance of each driving force mechanism The vector of a plate's motion is a function of all the forces acting on the plate; however, therein lies the problem regarding the degree to which each process contributes to the overall motion of each tectonic plate. The diversity of geodynamic settings and the properties of each plate result from the impact of the various processes actively driving each individual plate. One method of dealing with this problem is to consider the relative rate at which each plate is moving as well as the evidence related to the significance of each process to the overall driving force on the plate. One of the most significant correlations discovered to date is that lithospheric plates attached to downgoing (subducting) plates move much faster than other types of plates. The Pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Ring of Fire) and moves much faster than the plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates. It is thus thought that forces associated with the downgoing plate (slab pull and slab suction) are the driving forces which determine the motion of plates, except for those plates which are not being subducted. [ 11 ] This view however has been contradicted by a recent study which found that the actual motions of the Pacific plate and other plates associated with the East Pacific Rise do not correlate mainly with either slab pull or slab push, but rather with a mantle convection upwelling whose horizontal spreading along the bases of the various plates drives them along via viscosity-related traction forces. [ 49 ] The driving forces of plate motion continue to be active subjects of on-going research within geophysics and tectonophysics . History of the theory Further information: Plate Tectonics Revolution Summary Detailed map showing the tectonic plates with their movement vectors The development of the theory of plate tectonics was the scientific and cultural change which occurred during a period of 50 years of scientific debate. The event of the acceptance itself was a paradigm shift and can therefore be classified as a scientific revolution, [ 50 ] now described as the Plate Tectonics Revolution . Around the start of the twentieth century, various theorists unsuccessfully attempted to explain the many geographical, geological, and biological continuities between continents. 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.sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}.mw-parser-output .sidebar-navbar{text-align:right;font-size:115%;padding:0 0.4em 0.4em}.mw-parser-output .sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Internet An Opte Project visualization of routing paths through a portion of the Internet Index Outline General Access Activism Slacktivism Censorship Data activism Democracy Digital divide Digital rights Digital public goods Freedom Freedom of information Media capture Net neutrality Phenomena Meme Privacy Right to access Sociology Usage Vigilantism Virtual community Virtual volunteering Governance IGF NRO IANA ICANN IETF ISOC Information infrastructure Domain Name System Hypertext Transfer Protocol Internet exchange point Internet protocol suite Internet Protocol Transmission Control Protocol Internet service provider IP address Internet Message Access Protocol Simple Mail Transfer Protocol Services Blogs Microblogging Email Fax File sharing File transfer Games Instant messaging Podcasts Shopping Television Voice over IP World Wide Web search History Timeline Protocol Wars Pioneers Oldest domain names Internet portal .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e The Internet originated in the efforts of scientists and engineers to build and interconnect computer networks . The Internet Protocol Suite , the set of rules used to communicate between networks and devices on the Internet, arose from research and development in the United States and involved international collaboration, particularly with researchers in the United Kingdom and France . [ 1 ] [ 2 ] [ 3 ] Computer science was an emerging discipline in the late 1950s that began to consider time-sharing between computer users, and later, the possibility of achieving this over wide area networks . J. C. R. Licklider articulated the idea of a universal network at the Information Processing Techniques Office (IPTO) of the United States Department of Defense (DoD) Advanced Research Projects Agency (ARPA). Independently, Paul Baran at the RAND Corporation proposed a distributed network based on data in message blocks in the early 1960s, and Donald Davies conceived of packet switching in 1965 at the National Physical Laboratory (NPL), proposing a national commercial data network in the United Kingdom. ARPA awarded contracts in 1969 for the development of the ARPANET project, directed by Robert Taylor and managed by Lawrence Roberts . ARPANET adopted the packet switching technology proposed by Davies and sought input from Baran. The network of Interface Message Processors (IMPs) was built by a team at Bolt, Beranek, and Newman , with the design and specification led by Bob Kahn . The host-to-host protocol was specified mainly by graduate students, led by Steve Crocker at UCLA , along with Jon Postel and others. The ARPANET expanded rapidly across the United States with connections to the United Kingdom and Norway. Several early packet-switched networks emerged in the 1970s which researched and provided data networking . Louis Pouzin and Hubert Zimmermann pioneered a simplified end-to-end approach to internetworking at the IRIA . Peter Kirstein put internetworking into practice at University College London in 1973. Bob Metcalfe developed the theory and practice behind Ethernet and the PARC Universal Packet . ARPA initiatives and the International Network Working Group developed and refined ideas for internetworking, in which multiple separate networks could be joined into a network of networks . Vint Cerf , now at Stanford University , and Bob Kahn, now at DARPA, published their research on internetworking in 1974. Through the Internet Experiment Note series and later RFCs this evolved into the Transmission Control Protocol (TCP) and Internet Protocol (IP), two protocols of the Internet protocol suite . The design reflected concepts pioneered in the French CYCLADES project directed by Louis Pouzin. The development of packet switching networks was complemented by mathematical work in the 1970s by Leonard Kleinrock at UCLA. In the late 1970s, national and international public data networks emerged based on the X.25 protocol, designed by R\u00e9mi Despr\u00e9s and others. In the United States, the National Science Foundation (NSF) funded national supercomputing centers at several universities in the United States, and provided interconnectivity in 1986 with the NSFNET project, thus creating network access to these supercomputer sites for research and academic organizations in the United States. International connections to NSFNET, the emergence of architecture such as the Domain Name System , and the adoption of TCP/IP on existing networks in the United States and around the world marked the beginnings of the Internet . [ 4 ] [ 5 ] [ 6 ] Commercial Internet service providers (ISPs) emerged in 1989 in the United States and Australia. [ 7 ] Limited private connections to parts of the Internet by officially commercial entities emerged in several American cities by late 1989 and 1990. [ 8 ] The optical backbone of the NSFNET was decommissioned in 1995, removing the last restrictions on the use of the Internet to carry commercial traffic, as traffic transitioned to optical networks managed by Sprint, MCI and AT&T in the United States. Research at CERN in Switzerland by the British computer scientist Tim Berners-Lee in 1989\u201390 resulted in the World Wide Web , linking hypertext documents into an information system, accessible from any node on the network. [ 9 ] The dramatic expansion of the capacity of the Internet, enabled by the advent of wave division multiplexing (WDM) and the rollout of fiber optic cables in the mid-1990s, had a revolutionary impact on culture, commerce, and technology. This made possible the rise of near-instant communication by electronic mail , instant messaging , voice over Internet Protocol (VoIP) telephone calls, video chat , and the World Wide Web with its discussion forums , blogs , social networking services , and online shopping sites. Increasing amounts of data are transmitted at higher and higher speeds over fiber-optic networks operating at 1 Gbit/s , 10 Gbit/s, and 800 Gbit/s by 2019. [ 10 ] The Internet's takeover of the global communication landscape was rapid in historical terms: it only communicated 1% of the information flowing through two-way telecommunications networks in the year 1993, 51% by 2000, and more than 97% of the telecommunicated information by 2007. [ 11 ] The Internet continues to grow, driven by ever greater amounts of online information, commerce, entertainment, and social networking services . However, the future of the global network may be shaped by regional differences. [ 12 ] Foundations Precursors Telegraphy The practice of transmitting messages between two different places through an electromagnetic medium dates back to the electrical telegraph in the late 19th century, which was the first fully digital communication system. Radiotelegraphy began to be used commercially in the early 20th century. Telex became an operational teleprinter service in the 1930s. Such systems were limited to point-to-point communication between two end devices . Information theory Fundamental theoretical work in telecommunications technology was developed by Harry Nyquist and Ralph Hartley in the 1920s. Information theory , as enunciated by Claude Shannon in 1948, provided a firm theoretical underpinning to understand the trade-offs between signal-to-noise ratio , bandwidth , and error-free transmission in the presence of noise . Computers and modems Early fixed-program computers in the 1940s were operated manually by entering small programs via switches in order to load and run a series of programs. As transistor technology evolved in the 1950s, central processing units and user terminals came into use by 1955. The mainframe computer model was devised, and modems , such as the Bell 101 , allowed digital data to be transmitted over regular unconditioned telephone lines at low speeds by the late 1950s. These technologies made it possible to exchange data between remote computers . However, a fixed-line link was still necessary; the point-to-point communication model did not allow for direct communication between any two arbitrary systems. In addition, the applications were specific and not general purpose. Examples included SAGE (1958) and SABRE (1960). Time-sharing Christopher Strachey , who became Oxford University's first Professor of Computation , filed a patent application in the United Kingdom for time-sharing in February 1959. [ 13 ] [ 14 ] In June that year, he gave a paper \"Time Sharing in Large Fast Computers\" at the UNESCO Information Processing Conference in Paris where he passed the concept on to J. C. R. Licklider . [ 15 ] [ 16 ] Licklider, a vice president at Bolt Beranek and Newman, Inc. (BBN), promoted the idea of time-sharing as an alternative to batch processing . [ 14 ] John McCarthy , at MIT , wrote a memo in 1959 that broadened the concept of time sharing to encompass multiple interactive user sessions, which resulted in the Compatible Time-Sharing System (CTSS) implemented at MIT. Other multi-user mainframe systems developed, such as PLATO at the University of Illinois Chicago . [ 17 ] In the early 1960, the Advanced Research Projects Agency (ARPA) of the United States Department of Defense funded further research into time-sharing at MIT through Project MAC . Inspiration J. C. R. Licklider, while working at BBN, proposed a computer network in his March 1960 paper Man\u2013Computer Symbiosis : [ 18 ] .mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}} A network of such centers, connected to one another by wide-band communication lines [...] the functions of present-day libraries together with anticipated advances in information storage and retrieval and symbiotic functions suggested earlier in this paper In August 1962, Licklider and Welden Clark published the paper \"On-Line Man-Computer Communication\" [ 19 ] which was one of the first descriptions of a networked future. In October 1962, Licklider was hired by Jack Ruina as director of the newly established Information Processing Techniques Office (IPTO) within ARPA, with a mandate to interconnect the United States Department of Defense's main computers at Cheyenne Mountain , the Pentagon, and SAC HQ. There he formed an informal group within DARPA to further computer research. He began by writing memos in 1963 describing a distributed network to the IPTO staff, whom he called \"Members and Affiliates of the Intergalactic Computer Network \". [ 20 ] Although he left the IPTO in 1964, five years before the ARPANET went live, it was his vision of universal networking that provided the impetus for one of his successors, Robert Taylor , to initiate the ARPANET development. Licklider later returned to lead the IPTO in 1973 for two years. [ 21 ] Packet switching The \"message block\", designed by Paul Baran in 1962 and refined in 1964, is the first proposal of a data packet . [ 22 ] [ 23 ] .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} Main article: Packet switching The infrastructure for telephone systems at the time was based on circuit switching , which requires pre-allocation of a dedicated communication line for the duration of the call. Telegram services had developed store and forward telecommunication techniques. Western Union 's Automatic Telegraph Switching System Plan 55-A was based on message switching . The U.S. military's AUTODIN network became operational in 1962. These systems, like SAGE and SBRE, still required rigid routing structures that were prone to single point of failure . [ 24 ] The technology was considered vulnerable for strategic and military use because there were no alternative paths for the communication in case of a broken link. In the early 1960s, Paul Baran of the RAND Corporation produced a study of survivable networks for the U.S. military in the event of nuclear war. [ 25 ] [ 26 ] Information would be transmitted across a \"distributed\" network, divided into what he called \"message blocks\". [ 27 ] [ 28 ] [ 29 ] [ 30 ] Baran's design was intended for high-speed digital communication of voice messages using low-cost hardware; it was not implemented. [ 31 ] [ 32 ] [ 33 ] [ 34 ] In addition to being prone to a single point of failure, existing telegraphic techniques were inefficient and inflexible. Beginning in 1965 Donald Davies , at the National Physical Laboratory in the United Kingdom, independently developed a similar proposal of the concept, designed for high-speed data communication in computer networks , which he called packet switching , the term that would ultimately be adopted. [ 35 ] [ 36 ] [ 37 ] [ 38 ] Packet switching is a technique for transmitting computer data by splitting it into very short, standardized chunks, attaching routing information to each of these chunks, and transmitting them independently through a computer network. It provides better bandwidth utilization than traditional circuit-switching used for telephony, and enables the connection of computers with different transmission and receive rates. It is a distinct concept to message switching. [ 39 ] Networks that led to the Internet See also: List of packet-switched networks NPL network Main article: NPL network Following discussions with J. C. R. Licklider in 1965, Donald Davies became interested in data communications for computer networks. [ 40 ] [ 41 ] Later that year, at the National Physical Laboratory (NPL) in the United Kingdom, Davies designed and proposed a national commercial data network based on packet switching. [ 42 ] The following year, he described the use of \"switching nodes\" to act as routers in a digital communication network. [ 43 ] [ 44 ] The proposal was not taken up nationally but he produced a design for a local network to serve the needs of the NPL and prove the feasibility of packet switching using high-speed data transmission. [ 45 ] [ 46 ] To deal with packet permutations (due to dynamically updated route preferences) and to datagram losses (unavoidable when fast sources send to a slow destinations), he assumed that \"all users of the network will provide themselves with some kind of error control\", [ 47 ] thus inventing what came to be known as the end-to-end principle . In 1967, he and his team were the first to use the term 'protocol' in a modern data-commutation context. [ 48 ] In 1968, [ 49 ] Davies began building the Mark I packet-switched network to meet the needs of his multidisciplinary laboratory and prove the technology under operational conditions. [ 50 ] [ 51 ] The network's development was described at a 1968 conference. [ 52 ] [ 53 ] Elements of the network became operational in early 1969, [ 50 ] [ 54 ] the first implementation of packet switching, [ 55 ] [ 56 ] and the NPL network was the first to use high-speed links. [ 57 ] Many other packet switching networks built in the 1970s were similar \"in nearly all respects\" to Davies' original 1965 design. [ 40 ] The Mark II version which operated from 1973 used a layered protocol architecture. [ 57 ] In 1977, there were roughly 30 computers, 30 peripherals and 100 VDU terminals all able to interact through the NPL Network. [ 58 ] The NPL team carried out simulation work on wide-area packet networks, including datagrams and congestion ; and research into internetworking and secure communications . [ 50 ] [ 59 ] [ 60 ] The network was replaced in 1986. [ 57 ] ARPANET Main article: ARPANET Robert Taylor was promoted to the head of the Information Processing Techniques Office (IPTO) at Advanced Research Projects Agency (ARPA) in 1966. He intended to realize Licklider 's ideas of an interconnected networking system. [ 61 ] As part of the IPTO's role, three network terminals had been installed: one for System Development Corporation in Santa Monica , one for Project Genie at University of California, Berkeley , and one for the Compatible Time-Sharing System project at Massachusetts Institute of Technology (MIT). [ 62 ] Taylor's identified need for networking became obvious from the waste of resources apparent to him. {{cite news |last=Markoff |first=John |title=An Internet Pioneer Ponders the Next Revolution |work=[[The New York Times]] |url=https://archive.nytimes.com/www.nytimes.com/library/tech/99/12/biztech/articles/122099outlook-bobb.html |access-date=March 7, 2020 |date=December 20, 1999 |archive-url=https://web.archive.org/web/20050304045456/http://partners.nytimes.com/library/tech/99/12/biztech/articles/122099outlook-bobb.html |archive-date=March 4, 2005 |url-status=live}}</ref>\"}},\"i\":0}}]}' id=\"mwAf8\"/> For each of these three terminals, I had three different sets of user commands. So if I was talking online with someone at S.D.C. and I wanted to talk to someone I knew at Berkeley or M.I.T. about this, I had to get up from the S.D.C. terminal, go over and log into the other terminal and get in touch with them.... I said, oh man, it's obvious what to do: If you have these three terminals, there ought to be one terminal that goes anywhere you want to go where you have interactive computing. That idea is the ARPAnet. [ 62 ] Bringing in Larry Roberts from MIT in January 1967, he initiated a project to build such a network. Roberts and Thomas Merrill had been researching computer time-sharing over wide area networks (WANs). [ 63 ] Wide area networks emerged during the late 1950s and became established during the 1960s. At the first ACM Symposium on Operating Systems Principles in October 1967, Roberts presented a proposal for the \"ARPA net\", based on Wesley Clark's idea to use Interface Message Processors (IMP) to create a message switching network. [ 64 ] [ 65 ] [ 66 ] At the conference, Roger Scantlebury presented Donald Davies' work on a hierarchical digital communications network using packet switching and referenced the work of Paul Baran at RAND . Roberts incorporated the packet switching concepts proposed by Davies into the ARPANET design. He upgraded the proposed communications speed from 2.4 kbit/s to 50 kbit/s and sought input from Baran. [ 67 ] [ 68 ] ARPA awarded the contract to build the network to Bolt Beranek & Newman . The \"IMP guys\", led by Frank Heart and Bob Kahn , developed the routing, flow control, software design and network control. [ 40 ] [ 69 ] The first ARPANET link was established between the Network Measurement Center at the University of California, Los Angeles (UCLA) Henry Samueli School of Engineering and Applied Science led by Leonard Kleinrock , and the NLS system at Stanford Research Institute (SRI) led by Douglas Engelbart in Menlo Park , California at 22:30 hours on October 29, 1969. With reference to the actions of the graduate and undergraduate students working with the IMPs, Kleinrock said: [ 70 ] [ 71 ] {{Cite journal |last=Beranek |first=Leo |date=2000 |title=Roots of the Internet: A Personal History |url=https://www.jstor.org/stable/25081152 |journal=Massachusetts Historical Review |volume=2 |pages=55\u201375 |jstor=25081152 |issn=1526-3894}}</ref><ref name=\\\"NetValley\\\">{{cite web|url=http://www.netvalley.com/intval.html|title=Roads and Crossroads of Internet History|first=Gregory|last=Gromov|year=1995}}</ref> \"},\"author\":{\"wt\":\"\"},\"title\":{\"wt\":\"\"},\"source\":{\"wt\":\"\"}},\"i\":0}}]}' id=\"mwAkY\"/> \"We set up a telephone connection between us and the guys at SRI ...\", Kleinrock ... said in an interview: \"We typed the L and we asked on the phone, \"Do you see the L?\" \"Yes, we see the L,\" came the response. We typed the O, and we asked, \"Do you see the O.\" \"Yes, we see the O.\" Then we typed the G, and the system crashed ... Yet a revolution had begun\" .... [ 72 ] [ 73 ] Postage stamp of Azerbaijan (2004): 35 Years of the Internet, 1969\u20132004 By December 1969, a four-node network was connected by adding the Culler-Fried Interactive Mathematics Center at the University of California, Santa Barbara followed by the University of Utah Graphics Department. [ 74 ] In the same year, Taylor helped fund ALOHAnet , a system designed by professor Norman Abramson and others at the University of Hawai\u02bbi at M\u0101noa that transmitted data by radio between seven computers on four islands on Hawaii . [ 75 ] Steve Crocker , a graduate student at UCLA, formed the \"Network Working Group\" in 1969. Working with Jon Postel and others, [ 76 ] he initiated and managed the Request for Comments (RFC) process, which is still used today for proposing and distributing contributions. RFC 1, entitled \"Host Software\", was written by Crocker and published on April 7, 1969. The protocol for establishing links between network sites in the ARPANET, the Network Control Program (NCP), was completed in 1970. These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing . Roberts presented the idea of packet switching to the communication professionals, and faced anger and hostility. Before ARPANET was operating, they argued that the router buffers would quickly run out. After the ARPANET was operating, they argued packet switching would never be economic without the government subsidy. Baran had faced the same rejection and thus failed to convince the military into constructing a packet switching network. [ 77 ] [ 78 ] Early international collaborations via the ARPANET were sparse. Connections were made in 1973 to Norway ( NORSAR ), [ 79 ] via a satellite link at the Tanum Earth Station in Sweden, and to Peter Kirstein 's research group at University College London , which provided a gateway to British academic networks , the first international heterogenous resource sharing network. [ 80 ] Throughout the 1970s, Leonard Kleinrock developed the mathematical theory to model and measure the performance of packet-switching technology, building on his earlier work on the application of queueing theory to message switching systems. [ 81 ] [ 82 ] [ 83 ] By 1981, the number of hosts had grown to 213. [ 84 ] The ARPANET became the technical core of what would become the Internet, and a primary tool in developing the technologies used. CYCLADES Main article: CYCLADES CYCLADES was a French research network designed and directed by Louis Pouzin . [ 85 ] In 1972, he began implementing his ideas to build on the work of Donald Davies and explore alternatives to the early ARPANET design. [ 86 ] [ 87 ] His goal was to enable internetworking , which he called a \"catenet\". [ 88 ] This was the first network to implement the end-to-end principle by making the hosts responsible for reliable delivery of data, rather than the network itself, using unreliable datagrams . [ 89 ] [ 90 ] Concepts implemented in this network influenced the initial proposal of the Transmission Control Program, [ 91 ] [ 92 ] and were reflected in the later TCP/IP architecture. [ 93 ] [ 94 ] X.25 and public data networks Main articles: X.25 and public data network 1974 interview with Arthur C. Clarke by the Australian Broadcasting Corporation , in which he describes a future of ubiquitous networked personal computers Based on international research initiatives, particularly the contributions of R\u00e9mi Despr\u00e9s , packet switching network standards were developed by the CCITT, which is now the International Telegraph and Telephone Consultative Committee (ITU-T), in the form of X.25 and related standards. [ 95 ] [ 96 ] X.25 is built on the concept of virtual circuits emulating traditional telephone connections. The initial ITU Standard on X.25 was approved in March 1976. [ 97 ] Existing networks, such as Telenet in the United States adopted X.25 as well as new public data networks , such as DATAPAC in Canada and TRANSPAC in France. [ 95 ] [ 96 ] The protocol formed the basis for the SERCnet network between British academic and research sites, which became JANET in the 1980s, the United Kingdom's high-speed national research and education network (NREN). The British Post Office , Western Union International , and Tymnet collaborated to create the first international packet-switched network, referred to as the International Packet Switched Service (IPSS), in 1978. This network grew from Europe and the US to cover Canada, Hong Kong, and Australia by 1981. By the 1990s it provided a worldwide networking infrastructure. [ 98 ] X.25 was supplemented by the X.75 protocol which enabled internetworking between national PTT networks in Europe and commercial networks in North America. [ 99 ] [ 100 ] [ 101 ] Unlike the ARPANET and its protocols, X.25 was available for business use. In 1979, CompuServe became the first service to offer commercial electronic mail capabilities and technical support to personal computer users. The company broke new ground again in 1980 as the first to offer real-time chat with its CB Simulator . Telenet offered its Telemail electronic mail service, which was also targeted to enterprise use unlike the network mail system of the ARPANET. Other major dial-in networks were America Online (AOL) and Prodigy that also provided communications, content, and entertainment features. [ 102 ] Bulletin board system (BBS) networks also provided on-line access, such as FidoNet which was popular amongst hobbyist computer users, many of them hackers and amateur radio operators . [ citation needed ] Many of these public data networks went on to adopt TCP/IP and formed the infrastructure of the early Internet. UUCP and Usenet Main articles: UUCP and Usenet In 1979, two students at Duke University , Tom Truscott and Jim Ellis , originated the idea of using Bourne shell scripts to transfer news and messages on a serial line UUCP connection with nearby University of North Carolina at Chapel Hill . Following public release of the software in 1980, the mesh of UUCP hosts forwarding on the Usenet news rapidly expanded. UUCPnet, as it would later be named, also created gateways and links between FidoNet and dial-up BBS hosts. UUCP networks spread quickly due to the lower costs involved, ability to use existing leased lines, X.25 links or even ARPANET connections, and the lack of strict use policies compared to later networks like CSNET and BITNET . All connects were local. By 1981 the number of UUCP hosts had grown to 550, nearly doubling to 940 in 1984. [ 103 ] Sublink Network , operating since 1987 and officially founded in Italy in 1989, based its interconnectivity upon UUCP to redistribute mail and news groups messages throughout its Italian nodes (about 100 at the time) owned both by private individuals and small companies. Sublink Network evolved into one of the first examples of Internet technology coming into use through popular diffusion. 1973\u20131989: Merging the networks and creating the Internet Map of the TCP/IP test network in February 1982 TCP/IP Main article: Internet protocol suite Further information: Transmission Control Protocol and Internet Protocol First Internet demonstration, linking the ARPANET , PRNET , and SATNET on November 22, 1977 With so many different networking methods seeking interconnection, a method was needed to unify them. Louis Pouzin initiated the CYCLADES project in 1972, [ 104 ] building on the work of Donald Davies and the ARPANET. [ 105 ] An International Network Working Group formed in 1972; active members included Vint Cerf from Stanford University , Alex McKenzie from BBN , Donald Davies and Roger Scantlebury from NPL , and Louis Pouzin and Hubert Zimmermann from IRIA . [ 106 ] [ 107 ] [ 108 ] Pouzin coined the term catenet for concatenated network. Bob Metcalfe at Xerox PARC outlined the idea of Ethernet and PARC Universal Packet (PUP) for internetworking . Bob Kahn , now at DARPA , recruited Vint Cerf to work with him on the problem. By 1973, these groups had worked out a fundamental reformulation, in which the differences between network protocols were hidden by using a common internetworking protocol. Instead of the network being responsible for reliability, as in the ARPANET, the hosts became responsible. [ 2 ] [ 109 ] Cerf and Kahn published their ideas in May 1974, [ 91 ] which incorporated concepts implemented by Louis Pouzin and Hubert Zimmermann in the CYCLADES network. [ 89 ] [ 110 ] The specification of the resulting protocol, the Transmission Control Program , was published as .mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:\"\\\"\"\"\\\"\"\"'\"\"'\"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url(\"//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url(\"//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url(\"//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg\")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url(\"//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg\")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}} RFC 675 by the Network Working Group in December 1974. [ 111 ] It contains the first attested use of the term internet , as a shorthand for internetwork. This software was monolithic in design using two simplex communication channels for each user session. With the role of the network reduced to a core of functionality, it became possible to exchange traffic with other networks independently from their detailed characteristics, thereby solving the fundamental problems of internetworking. DARPA agreed to fund the development of prototype software, work on which was documented in the Internet Experiment Notes . Testing began in 1975 through concurrent implementations at Stanford, BBN and University College London (UCL). [ 3 ] After several years of work, the first demonstration of a gateway between the Packet Radio network (PRNET) in the SF Bay area and the ARPANET was conducted by", "Ancient Egypt Cradle of civilization in North Africa .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} \"Ancient Egyptian\" redirects here. For the language, see Egyptian language . For the magazine, see Ancient Egypt (magazine) . For the TV series, see Ancient Egyptians (TV series) . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCw\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwDA\\\"/></a></span>\"}' id=\"mwDQ\"/> \"},\"year_start\":{\"wt\":\"{{circa|3150 BC}}\"},\"common_languages\":{\"wt\":\"[[Egyptian language]]\"},\"year_end\":{\"wt\":\"30 BC{{efn|Depending on the definition, the end of ancient Egypt may be considered to have occurred either with the end of the [[Late 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BC\"},\"event_end\":{\"wt\":\"[[War of Actium|Annexation by the Roman Empire]]\"},\"p1\":{\"wt\":\"Predynastic Egypt\"},\"s1\":{\"wt\":\"Roman Egypt\"}},\"i\":0}}]}' id=\"mwEQ\">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} .mw-parser-output .ib-country{border-collapse:collapse;line-height:1.2em}.mw-parser-output .ib-country td,.mw-parser-output .ib-country th{border-top:1px solid #a2a9b1;padding:0.4em 0.6em 0.4em 0.6em}.mw-parser-output .ib-country .mergedtoprow .infobox-header,.mw-parser-output .ib-country .mergedtoprow .infobox-label,.mw-parser-output .ib-country .mergedtoprow .infobox-data,.mw-parser-output .ib-country .mergedtoprow .infobox-full-data,.mw-parser-output .ib-country .mergedtoprow .infobox-below{border-top:1px solid #a2a9b1;padding:0.4em 0.6em 0.2em 0.6em}.mw-parser-output .ib-country .mergedrow .infobox-label,.mw-parser-output .ib-country .mergedrow .infobox-data,.mw-parser-output .ib-country .mergedrow .infobox-full-data{border:0;padding:0 0.6em 0.2em 0.6em}.mw-parser-output .ib-country .mergedbottomrow .infobox-label,.mw-parser-output .ib-country .mergedbottomrow .infobox-data,.mw-parser-output .ib-country .mergedbottomrow .infobox-full-data{border-top:0;border-bottom:1px solid #a2a9b1;padding:0 0.6em 0.4em 0.6em}.mw-parser-output .ib-country .infobox-header{text-align:left}.mw-parser-output .ib-country .infobox-above{font-size:125%;line-height:1.2}.mw-parser-output .ib-country-names{padding-top:0.25em;font-weight:normal}.mw-parser-output .ib-country-name-style{display:inline}.mw-parser-output .ib-country .infobox-image{padding:0.5em 0}.mw-parser-output .ib-country-anthem{border-top:1px solid #a2a9b1;padding-top:0.5em;margin-top:0.5em}.mw-parser-output .ib-country-map-caption{position:relative;top:0.3em}.mw-parser-output .ib-country-largest,.mw-parser-output .ib-country-lang{font-weight:normal}.mw-parser-output .ib-country-ethnic,.mw-parser-output .ib-country-religion,.mw-parser-output .ib-country-sovereignty{font-weight:normal;display:inline}.mw-parser-output .ib-country-fake-li{text-indent:-0.9em;margin-left:1.2em;font-weight:normal}.mw-parser-output .ib-country-fake-li2{text-indent:0.5em;margin-left:1em;font-weight:normal}.mw-parser-output .ib-country-website{line-height:11pt}.mw-parser-output .ib-country-map-caption3{position:relative;top:0.3em}.mw-parser-output .ib-country-fn{text-align:left;margin:0 auto}.mw-parser-output .ib-country-fn-alpha{list-style-type:lower-alpha;margin-left:1em}.mw-parser-output .ib-country-fn-num{margin-left:1em} Ancient Egypt c. 3150 BC \u2013 30 BC Nile</a> up to the <a rel=\\\"mw:WikiLink\\\" href=\\\"./Cataracts_of_the_Nile\\\" title=\\\"Cataracts of the Nile\\\" id=\\\"mwFA\\\">Fifth Cataract</a>. Modern <a rel=\\\"mw:WikiLink\\\" href=\\\"./Cairo\\\" title=\\\"Cairo\\\" id=\\\"mwFQ\\\">Cairo</a> and <a rel=\\\"mw:WikiLink\\\" href=\\\"./Jerusalem\\\" title=\\\"Jerusalem\\\" id=\\\"mwFg\\\">Jerusalem</a> are marked for reference.\"}'> Ancient Egyptian cities and other sites following the Nile up to the Fifth Cataract . Modern Cairo and Jerusalem are marked for reference. Capital See List of historical capitals of Egypt Common languages Egyptian language Religion Egyptian religion Historical era Ancient history \u2022 Unification of Upper and Lower Egypt c. 3150 BC \u2022 Early Dynastic Period c. 3150 BC \u2013 2686 BC \u2022 Old Kingdom 2686 BC \u2013 2181 BC \u2022 Middle Kingdom 2134 BC \u2013 1690 BC \u2022 New Kingdom 1549 BC \u2013 1078/77 BC [ a ] \u2022 Late Period 664 BC \u2013 332 BC \u2022 Ptolemaic Kingdom 332 BC \u2013 30 BC \u2022 Annexation by the Roman Empire 30 BC [ b ] Preceded by Succeeded by Predynastic Egypt Roman Egypt Ancient Egypt was a cradle of civilization concentrated along the lower reaches of the Nile River in the eastern corner of North Africa . It emerged from prehistoric Egypt around 3150 BC (according to conventional Egyptian chronology ), [ 1 ] when Upper and Lower Egypt were united by Menes , who is believed by the majority of Egyptologists to have been the same person as Narmer . [ 2 ] The history of ancient Egypt unfolded as a series of stable kingdoms interspersed by the \" Intermediate Periods \" of relative instability. These stable kingdoms existed in one of three periods: the Old Kingdom of the Early Bronze Age ; the Middle Kingdom of the Middle Bronze Age ; or the New Kingdom of the Late Bronze Age . The pinnacle of ancient Egyptian power was achieved during the New Kingdom, which extended its rule to much of Nubia and a considerable portion of the Levant . After this period, Egypt entered an era of slow decline. Over the course of its history, it was invaded or conquered by a number of foreign civilizations, including the Hyksos , the Kushites , the Assyrians , the Persians , and the Greeks and then the Romans . The end of ancient Egypt is variously defined as occurring with the end of the Late Period during the Wars of Alexander the Great in 332 BC or with the end of the Greek-ruled Ptolemaic Kingdom during the Roman conquest of Egypt in 30 BC. [ 3 ] In AD 642, the Arab conquest of Egypt brought an end to the region's millennium-long Greco-Roman period . The success of ancient Egyptian civilization came partly from its ability to adapt to the Nile's conditions for agriculture . The predictable flooding of the Nile and controlled irrigation of its fertile valley produced surplus crops, which supported a more dense population, and thereby substantial social and cultural development. With resources to spare, the administration sponsored the mineral exploitation of the valley and its surrounding desert regions, the early development of an independent writing system , the organization of collective construction and agricultural projects, trade with other civilizations, and a military to assert Egyptian dominance throughout the Near East . Motivating and organizing these activities was a bureaucracy of elite scribes, religious leaders, and administrators under the control of the reigning pharaoh , who ensured the cooperation and unity of the Egyptian people in the context of an elaborate system of religious beliefs . [ 4 ] Among the many achievements of ancient Egypt are: the quarrying , surveying, and construction techniques that supported the building of monumental pyramids , temples , and obelisks ; a system of mathematics ; a practical and effective system of medicine ; irrigation systems and agricultural production techniques; the first known planked boats; [ 5 ] Egyptian faience and glass technology ; new forms of literature ; and the earliest known peace treaty , which was ratified with the Anatolia -based Hittite Empire . [ 6 ] Its art and architecture were widely copied and its antiquities were carried off to be studied, admired, or coveted in the far corners of the world. Likewise, its monumental ruins inspired the imaginations of travelers and writers for millennia. A newfound European and Egyptian respect for antiquities and excavations that began in earnest in the early modern period has led to much scientific investigation of ancient Egypt and its society, as well as a greater appreciation of its cultural legacy. [ 7 ] History Main articles: History of ancient Egypt , Population history of Egypt , Sahara , Northeast Africa , and North Africa The Nile has been the lifeline of its region for much of human history. The fertile floodplain of the Nile gave humans the opportunity to develop a settled agricultural economy and a more sophisticated, centralized society that became a cornerstone in the history of human civilization. [ 8 ] Predynastic period Main article: Predynastic Egypt Artifacts of Egypt from the prehistoric period, from 4400 to 3100 BC. First row from top left: a Badarian ivory figurine, a Naqada II jar, a Bat figurine. Second row: a diorite vase, the Gebel el-Arak Knife , a cosmetic palette . Ancient Petroglyphs of giraffe, ostrich, and longhorned cow being driven by a human, featured in the desert region, Gilf Kebir , Egypt. In Predynastic and Early Dynastic times, the Egyptian climate was much less arid than it is today . Large regions of Egypt were savanna and traversed by herds of grazing ungulates . Foliage and fauna were far more prolific in all environs, and the Nile region supported large populations of waterfowl . Hunting would have been common for Egyptians, and this is also the period when many animals were first domesticated . [ 9 ] By about 5500 BC , small tribes living in the Nile valley had developed into a series of cultures demonstrating firm control of agriculture and animal husbandry , and identifiable by their pottery and personal items, such as combs, bracelets, and beads. The largest of these early cultures in upper (Southern) Egypt was the Badarian culture , which probably originated in the Western Desert ; it was known for its high-quality ceramics, stone tools , and its use of copper. [ 10 ] The Badari was followed by the Naqada culture : the Naqada I ( Amratian ), the Naqada II ( Gerzeh ), and Naqada III ( Semainean ). [ 11 ] These brought a number of technological improvements. As early as the Naqada I Period, predynastic Egyptians imported obsidian from Ethiopia , used to shape blades and other objects from flakes . [ 12 ] [ 13 ] Mutual trade with the Levant was established during Naqada II ( c. 3600\u20133350 BC ); this period was also the beginning of trade with Mesopotamia , which continued into the early dynastic period and beyond. [ 14 ] Over a period of about 1,000 years, the Naqada culture developed from a few small farming communities into a powerful civilization whose leaders were in complete control of the people and resources of the Nile valley. [ 15 ] Establishing a power center at Nekhen , and later at Abydos , Naqada III leaders expanded their control of Egypt northwards along the Nile . [ 16 ] They also traded with Nubia to the south, the oases of the western desert to the west, and the cultures of the eastern Mediterranean and Near East to the east. [ 17 ] The Naqada culture manufactured a diverse selection of material goods, reflective of the increasing power and wealth of the elite, as well as societal personal-use items, which included combs, small statuary, painted pottery, high quality decorative stone vases , cosmetic palettes , and jewelry made of gold, lapis , and ivory . They also developed a ceramic glaze known as faience , which was used well into the Roman Period to decorate cups, amulets, and figurines. [ 18 ] [ 19 ] During the last predynastic phase, the Naqada culture began using written symbols that eventually were developed into a full system of hieroglyphs for writing the ancient Egyptian language. [ 20 ] Early Dynastic Period ( c. 3150\u20132686 BC) Main article: Early Dynastic Period of Egypt The Narmer Palette depicts the unification of the Two Lands. [ 21 ] The Early Dynastic Period was approximately contemporary to the early Sumerian - Akkadian civilization of Mesopotamia and of ancient Elam . The third-century BC Egyptian priest Manetho grouped the long line of kings from Menes to his own time into 30 dynasties, a system still used today. He began his official history with the king named \"Meni\" (or Menes in Greek), who was believed to have united the two kingdoms of Upper and Lower Egypt . [ 22 ] The transition to a unified state happened more gradually than ancient Egyptian writers represented, and there is no contemporary record of Menes. Some scholars now believe, however, that the mythical Menes may have been the king Narmer , who is depicted wearing royal regalia on the ceremonial Narmer Palette , in a symbolic act of unification. [ 23 ] In the Early Dynastic Period, which began about 3000 BC, the first of the Dynastic kings solidified control over Lower Egypt by establishing a capital at Memphis , from which he could control the labor force and agriculture of the fertile delta region , as well as the lucrative and critical trade routes to the Levant . The increasing power and wealth of the kings during the early dynastic period was reflected in their elaborate mastaba tombs and mortuary cult structures at Abydos, which were used to celebrate the deified king after his death. [ 24 ] The strong institution of kingship developed by the kings served to legitimize state control over the land, labor, and resources that were essential to the survival and growth of ancient Egyptian civilization. [ 25 ] Old Kingdom (2686\u20132181 BC) Main article: Old Kingdom of Egypt The pyramids of Giza are among the most recognizable symbols of ancient Egyptian civilization. Khafre enthroned ( c. 2558\u20132532 BC) Major advances in architecture, art, and technology were made during the Old Kingdom , fueled by the increased agricultural productivity and resulting population growth, made possible by a well-developed central administration. [ 26 ] Some of ancient Egypt's crowning achievements, the Giza pyramids and Great Sphinx , were constructed during the Old Kingdom. Under the direction of the vizier , state officials collected taxes, coordinated irrigation projects to improve crop yield , and drafted peasants to work on construction projects. [ 27 ] With the rise of central administration in Egypt, a new class of educated scribes and officials emerged and were granted estates by the king as payment for their services. Kings also made land grants to their mortuary cults and local temples , to ensure that these institutions had the resources to worship the king after his death. Scholars believe that five centuries of these practices slowly eroded the economic vitality of Egypt, and that the economy could no longer afford to support a large centralized administration. [ 28 ] As the power of the kings diminished, regional governors called nomarchs began to challenge the supremacy of the office of king. This, coupled with severe droughts between 2200 and 2150 BC, [ 29 ] is believed to have caused the country to enter the 140-year period of famine and strife known as the First Intermediate Period. [ 30 ] First Intermediate Period (2181\u20132055 BC) Main article: First Intermediate Period of Egypt After Egypt's central government collapsed at the end of the Old Kingdom, the administration could no longer support or stabilize the country's economy. The ensuing food shortages and political disputes escalated into famines and small-scale civil wars. Yet despite difficult problems, local leaders, owing no tribute to the king, used their new-found independence to establish a thriving culture in the provinces. Once in control of their own resources, the provinces became economically richer\u2014which was demonstrated by larger and better burials among all social classes. [ 31 ] Free from their loyalties to the king, local rulers began competing with each other for territorial control and political power . By 2160 BC, rulers in Herakleopolis controlled Lower Egypt in the north, while a rival clan based in Thebes , the Intef family , took control of Upper Egypt in the south. As the Intefs grew in power and expanded their control northward, a clash between the two rival dynasties became inevitable. Around 2055 BC the northern Theban forces under Nebhepetre Mentuhotep II finally defeated the Herakleopolitan rulers, reuniting the Two Lands. They inaugurated a period of economic and cultural renaissance known as the Middle Kingdom . [ 32 ] Middle Kingdom (2134\u20131690 BC) Main article: Middle Kingdom of Egypt A figure wearing the red crown of Lower Egypt, most probably Amenemhat II or Senwosret II The kings of the Middle Kingdom restored the country's stability, which saw a resurgence of art and monumental building projects, and a new flourishing of literature . [ 33 ] Mentuhotep II and his Eleventh Dynasty successors ruled from Thebes, but the vizier Amenemhat I , upon assuming the kingship at the beginning of the Twelfth Dynasty around 1985 BC, shifted the kingdom's capital to the city of Itjtawy , located in Faiyum . [ 34 ] From Itjtawy, the kings of the Twelfth Dynasty undertook a far-sighted land reclamation and irrigation scheme to increase agricultural output in the region. Moreover, the military reconquered territory in Nubia that was rich in quarries and gold mines, while laborers built a defensive structure in the Eastern Delta, called the \" Walls of the Ruler \", to defend against foreign attack. [ 35 ] With the kings having secured the country militarily and politically and with vast agricultural and mineral wealth at their disposal, the nation's population, arts, and religion flourished. The Middle Kingdom displayed an increase in expressions of personal piety toward the gods. Middle Kingdom literature featured sophisticated themes and characters written in a confident, eloquent style. [ 36 ] The relief and portrait sculpture of the period captured subtle, individual details that reached new heights of technical sophistication. [ 37 ] Second Intermediate Period (1674\u20131549 BC) and the Hyksos Main article: Second Intermediate Period of Egypt {{harvnb|Montet|1968|p=80|ps=. \\\"Others were later added to them, things which came from the pharaoh Ahmose, like the axe decorated with a griffin and a likeness of the king slaying a Hyksos, with other axes and daggers.\\\"}}</ref>\"}},\"i\":0}}]}' id=\"mwAZ4\">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}} Pharaoh Ahmose I (ruled c. 1549\u20131524 BC) slaying a probable Hyksos . Detail of a ceremonial axe in the name of Ahmose I, treasure of Queen Ahhotep II . [ 38 ] Around 1785 BC, as the power of the Middle Kingdom kings weakened, a Western Asian people called the Hyksos , who had already settled in the Delta, seized control of Egypt and established their capital at Avaris , forcing the former central government to retreat to Thebes . The king was treated as a vassal and expected to pay tribute. [ 39 ] The Hyksos ('foreign rulers') retained Egyptian models of government and identified as kings, thereby integrating Egyptian elements into their culture. [ 40 ] After retreating south, the native Theban kings found themselves trapped between the Canaanite Hyksos ruling the north and the Hyksos' Nubian allies, the Kushites , to the south. After years of vassalage, Thebes gathered enough strength to challenge the Hyksos in a conflict that lasted more than 30 years, until 1555 BC. [ 39 ] Ahmose I waged a series of campaigns that permanently eradicated the Hyksos' presence in Egypt. He is considered the founder of the Eighteenth Dynasty , and the military became a central priority for his successors, who sought to expand Egypt's borders and attempted to gain mastery of the Near East . [ 41 ] New Kingdom (1549\u20131069 BC) Main article: New Kingdom of Egypt Pharaohs' tombs were provided with vast quantities of wealth, such as the golden mask from the mummy of Tutankhamun . The New Kingdom pharaohs established a period of unprecedented prosperity by securing their borders and strengthening diplomatic ties with their neighbours, including the Mitanni Empire, Assyria , and Canaan . Military campaigns waged under Tuthmosis I and his grandson Tuthmosis III extended the influence of the pharaohs to the largest empire Egypt had ever seen. Between their reigns, Hatshepsut , a queen who established herself as pharaoh, launched many building projects, including the restoration of temples damaged by the Hyksos, and sent trading expeditions to Punt and the Sinai. [ 42 ] When Tuthmosis III died in 1425 BC, Egypt had an empire extending from Niya in north west Syria to the Fourth Cataract of the Nile in Nubia , cementing loyalties and opening access to critical imports such as bronze and wood . [ 43 ] The New Kingdom pharaohs began a large-scale building campaign to promote the god Amun , whose growing cult was based in Karnak . They also constructed monuments to glorify their own achievements, both real and imagined. The Karnak temple is the largest Egyptian temple ever built. [ 44 ] Around 1350 BC, the stability of the New Kingdom was threatened when Amenhotep IV ascended the throne and instituted a series of radical and chaotic reforms. Changing his name to Akhenaten , he touted the previously obscure sun deity Aten as the supreme deity , suppressed the worship of most other deities, and moved the capital to the new city of Akhetaten (modern-day Amarna ). [ 45 ] He was devoted to his new religion and artistic style . After his death, the cult of the Aten was quickly abandoned and the traditional religious order restored. The subsequent pharaohs, Tutankhamun , Ay , and Horemheb , worked to erase all mention of Akhenaten's heresy, now known as the Amarna Period . [ 46 ] Around 1279 BC, Ramesses II , also known as Ramesses the Great, ascended the throne, and went on to build more temples, erect more statues and obelisks, and sire more children than any other pharaoh in history. [ c ] A bold military leader, Ramesses II led his army against the Hittites in the Battle of Kadesh (in modern Syria ) and, after fighting to a stalemate, finally agreed to the first recorded peace treaty , around 1258 BC. [ 47 ] Egypt's wealth, however, made it a tempting target for invasion, particularly by the Libyan Berbers to the west, and the Sea Peoples , a conjectured confederation of seafarers from the Aegean Sea . [ d ] Initially, the military was able to repel these invasions, but Egypt eventually lost control of its remaining territories in southern Canaan , much of it falling to the Assyrians. The effects of external threats were exacerbated by internal problems such as corruption, tomb robbery, and civil unrest . After regaining their power, the high priests at the temple of Amun in Thebes accumulated vast tracts of land and wealth, and their expanded power splintered the country during the Third Intermediate Period. [ 48 ] Third Intermediate Period (1069\u2013653 BC) Main article: Third Intermediate Period of Egypt Statues of two pharaohs of Egypt's Twenty-Fifth Dynasty and several other Kushite kings, Kerma Museum [ 49 ] Following the death of Ramesses XI in 1078 BC, Smendes assumed authority over the northern part of Egypt, ruling from the city of Tanis . The south was effectively controlled by the High Priests of Amun at Thebes , who recognized Smendes in name only. [ 50 ] During this time, Libyans had been settling in the western delta, and chieftains of these settlers began increasing their autonomy. Libyan princes took control of the delta under Shoshenq I in 945 BC, founding the so-called Libyan or Bubastite dynasty that would rule for some 200 years. Shoshenq also gained control of southern Egypt by placing his family members in important priestly positions. Libyan control began to erode as a rival dynasty in the delta arose in Leontopolis , and Kushites threatened from the south. Around 727 BC the Kushite king Piye invaded northward, seizing control of Thebes and eventually the Delta, which established the 25th Dynasty . [ 51 ] During the 25th Dynasty, Pharaoh Taharqa created an empire nearly as large as the New Kingdom 's. Twenty-fifth Dynasty pharaohs built, or restored, temples and monuments throughout the Nile valley, including at Memphis, Karnak, Kawa, and Jebel Barkal. [ 52 ] During this period, the Nile valley saw the first widespread construction of pyramids (many in modern Sudan) since the Middle Kingdom. [ 53 ] [ 54 ] [ 55 ] Egypt's far-reaching prestige declined considerably toward the end of the Third Intermediate Period. Its foreign allies had fallen into the Assyrian sphere of influence, and by 700 BC war between the two states became inevitable. Between 671 and 667 BC the Assyrians began the Assyrian conquest of Egypt . The reigns of both Taharqa and his successor, Tanutamun , were filled with frequent conflict with the Assyrians. Ultimately, the Assyrians pushed the Kushites back into Nubia, occupied Memphis, and sacked the temples of Thebes . [ 56 ] Late Period (653\u2013332 BC) Main articles: Late Period of Egypt and History of Persian Egypt The Assyrians left control of Egypt to a series of vassals who became known as the Saite kings of the Twenty-Sixth Dynasty . By 653 BC, the Saite king Psamtik I was able to oust the Assyrians with the help of Greek mercenaries, who were recruited to form Egypt's first navy . Greek influence expanded greatly as the city-state of Naucratis became the home of Greeks in the Nile Delta. The Saite kings based in the new capital of Sais witnessed a brief but spirited resurgence in the economy and culture, but in 525 BC, the Persian Empire, led by Cambyses II , began its conquest of Egypt, eventually defeating the pharaoh Psamtik III at the Battle of Pelusium . Cambyses II then assumed the formal title of pharaoh, but ruled Egypt from Iran, leaving Egypt under the control of a satrap . A few revolts against the Persians marked the 5th century BC, but Egypt was never able to overthrow the Persians until the end of the century. [ 57 ] Following its annexation by Persia, Egypt was joined with Cyprus and Phoenicia in the sixth satrapy of the Achaemenid Persian Empire . This first period of Persian rule over Egypt, also known as the Twenty-Seventh Dynasty , ended in 402 BC, when Egypt regained independence under a series of native dynasties. The last of these dynasties, the Thirtieth , proved to be the last native royal house of ancient Egypt, ending with the kingship of Nectanebo II . A brief restoration of Persian rule, sometimes known as the Thirty-First Dynasty , began in 343 BC, but shortly after, in 332 BC, the Persian ruler Mazaces handed Egypt over to Alexander the Great without a fight. [ 58 ] Ptolemaic period (332\u201330 BC) Main article: Ptolemaic Kingdom Portrait of Ptolemy VI Philometor wearing the double crown of Egypt In 332 BC, Alexander the Great conquered Egypt with little resistance from the Persians and was welcomed by the Egyptians as a deliverer. The administration established by Alexander's successors, the Macedonian Ptolemaic Kingdom , was based on an Egyptian model and based in the new capital city of Alexandria . The city showcased the power and prestige of Hellenistic rule, and became a centre of learning and culture that included the famous Library of Alexandria and the Mouseion . [ 59 ] The Lighthouse of Alexandria lit the way for the many ships that kept trade flowing through the city\u2014as the Ptolemies made commerce and revenue-generating enterprises, such as papyrus manufacturing, their top priority. [ 60 ] Hellenistic culture did not supplant native Egyptian culture, as the Ptolemies supported time-honored traditions in an effort to secure the loyalty of the populace. They built new temples in Egyptian style, supported traditional cults, and portrayed themselves as pharaohs. Some traditions merged, as Greek and Egyptian gods were syncretized into composite deities, such as Serapis , and classical Greek forms of sculpture influenced traditional Egyptian motifs. Despite their efforts to appease the Egyptians, the Ptolemies were challenged by native rebellion, bitter family rivalries, and frequent mob violence in Alexandria. [ 61 ] In addition, as Rome relied more heavily on imports of grain from Egypt, the Romans took great interest in the political situation in the country. Continued Egyptian revolts, ambitious politicians, and powerful opponents from the Near East made this situation unstable, leading Rome to send forces to secure the country as a province of its empire. [ 62 ] Roman period (30 BC \u2013 AD 642) Main article: Roman Egypt The Fayum mummy portraits epitomize the meeting of Egyptian and Roman cultures. Egypt became a province of the Roman Empire in 30 BC, following the defeat of Mark Antony and Ptolemaic Queen Cleopatra VII by Octavian (later Emperor Augustus) in the Battle of Actium . The Romans relied heavily on grain shipments from Egypt, and the Roman army , under the control of a prefect appointed by the emperor, quelled rebellions, strictly enforced the collection of heavy taxes, and prevented attacks by bandits, which had become a notorious problem during the period. [ 63 ] Alexandria became an increasingly important center on the trade route with the orient, as exotic luxuries were in high demand in Rome. [ 64 ] Although the Romans had a more hostile attitude than the Greeks towards the Egyptians, some traditions such as mummification and worship of the traditional gods continued. [ 65 ] The art of mummy portraiture flourished, and some Roman emperors had themselves depicted as pharaohs, though not to the extent that the Ptolemies had. The former lived outside Egypt and did not perform the ceremonial functions of Egyptian kingship. Local administration became Roman in style and closed to native Egyptians. [ 65 ] From the mid-first century AD, Christianity took root in Egypt and it was originally seen as another cult that could be accepted. However, it was an uncompromising religion that sought to win converts from the pagan Egyptian and Greco-Roman religions and threatened popular religious traditions. This led to the persecution of converts to Christianity, culminating in the great purges of Diocletian starting in 303, but eventually Christianity won out. [ 66 ] In 391, the Christian emperor Theodosius introduced legislation that banned pagan rites and closed temples. [ 67 ] Alexandria became the scene of great anti-pagan riots with public and private religious imagery destroyed. [ 68 ] As a consequence, Egypt's native religious culture was continually in decline. While the native population continued to speak their language , the ability to read hieroglyphic writing slowly disappeared as the role of the Egyptian temple priests and priestesses diminished. The temples themselves were sometimes converted to churches or abandoned to the desert. [ 69 ] Government and economy Administration and commerce The pharaoh was the absolute monarch of the country and, at least in theory, wielded complete control of the land and its resources. The king was the supreme military commander and head of the government, who relied on a bureaucracy of officials to manage his affairs. In charge of the administration was his second in command, the vizier , who acted as the king's representative and coordinated land surveys, the treasury, building projects, the legal system, and the archives . [ 70 ] At a regional level, the country was divided into as many as 42 administrative regions called nomes each governed by a nomarch , who was accountable to the vizier for his jurisdiction. The temples formed the backbone of the economy. Not only were they places of worship , but were also responsible for collecting and storing the kingdom's wealth in a system of granaries and treasuries", "Quantum mechanics Description of physical properties at the atomic and subatomic scale .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} \"Quantum systems\" redirects here. For the company, see Quantum-Systems . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> <a href=\\\"./Wikipedia:Good_articles*\\\" title=\\\"This is a good article. Click here for more information.\\\" id=\\\"mwDw\\\"><img alt=\\\"This is a good article. Click here for more information.\\\" resource=\\\"./File:Symbol_support_vote.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/20px-Symbol_support_vote.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"180\\\" data-file-height=\\\"185\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"19\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/40px-Symbol_support_vote.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwEA\\\"/></a></span>\\n\"}' id=\"mwEQ\"/> For a more accessible and less technical introduction to this topic, see Introduction to quantum mechanics . Wave functions of the electron in a hydrogen atom at different energy levels. Quantum mechanics cannot predict the exact location of a particle in space, only the probability of finding it at different locations. [ 1 ] The brighter areas represent a higher probability of finding the electron. .mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:\": \"}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:\"\\a0 \u00b7 \";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output 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screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Part of a series of articles about Quantum mechanics i \u210f d d t | \u03a8 \u27e9 = H ^ | \u03a8 \u27e9 {\\displaystyle i\\hbar {\\frac {d}{dt}}|\\Psi \\rangle ={\\hat {H}}|\\Psi \\rangle } Schr\u00f6dinger equation Introduction Glossary History Background Classical mechanics Old quantum theory Interference Fundamentals Bra\u2013ket notation Complementarity Entanglement Energy level Hamiltonian Measurement Nonlocality Quantum number State Superposition Symmetry Tunnelling Uncertainty Wave function Collapse Experiments Bell's inequality Davisson \u2013 Germer Double-slit Elitzur \u2013 Vaidman Franck \u2013 Hertz Mach \u2013 Zehnder Delayed-choice quantum eraser Stern \u2013 Gerlach Rutherford Formulations Overview Heisenberg Interaction Matrix Phase-space Schr\u00f6dinger Sum-over-histories (path integral) Equations Dirac Klein\u2013Gordon Pauli Rydberg Schr\u00f6dinger Interpretations Bayesian Consciousness causes collapse Consistent histories Copenhagen de Broglie\u2013Bohm Ensemble Hidden-variable Many-worlds Objective-collapse Quantum logic Superdeterminism Relational Transactional Advanced topics Relativistic quantum mechanics Quantum field theory Quantum information science Quantum computing Quantum chaos Decoherence EPR paradox Density matrix Scattering theory Quantum statistical mechanics Quantum machine learning .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e Quantum mechanics is the fundamental physical theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms . [ 2 ] : 1.1 It is the foundation of all quantum physics , which includes quantum chemistry , quantum biology , quantum field theory , quantum technology , and quantum information science . Quantum mechanics can describe many systems that classical physics cannot. Classical physics can describe many aspects of nature at an ordinary ( macroscopic and (optical) microscopic ) scale, however is insufficient for describing them at very small submicroscopic (atomic and subatomic ) scales. Classical mechanics can be derived from quantum mechanics as an approximation that is valid at ordinary scales. [ 3 ] Quantum systems have bound states that are quantized to discrete values of energy , momentum , angular momentum , and other quantities, in contrast to classical systems where these quantities can be measured continuously. Measurements of quantum systems show characteristics of both particles and waves ( wave\u2013particle duality ), and there are limits to how accurately the value of a physical quantity can be predicted prior to its measurement, given a complete set of initial conditions (the uncertainty principle ). Quantum mechanics arose gradually from theories to explain observations that could not be reconciled with classical physics , such as Max Planck 's solution in 1900 to the black-body radiation problem, and the correspondence between energy and frequency in Albert Einstein 's 1905 paper , which explained the photoelectric effect . These early attempts to understand microscopic phenomena, now known as the \" old quantum theory \", led to the full development of quantum mechanics in the mid-1920s by Niels Bohr , Erwin Schr\u00f6dinger , Werner Heisenberg , Max Born , Paul Dirac and others. The modern theory is formulated in various specially developed mathematical formalisms . In one of them, a mathematical entity called the wave function provides information, in the form of probability amplitudes , about what measurements of a particle's energy, momentum, and other physical properties may yield. Overview and fundamental concepts Quantum mechanics allows the calculation of properties and behaviour of physical systems . It is typically applied to microscopic systems: molecules , atoms and subatomic particles . It has been demonstrated to hold for complex molecules with thousands of atoms, [ 4 ] but its application to human beings raises philosophical problems, such as Wigner's friend , and its application to the universe as a whole remains speculative. [ 5 ] Predictions of quantum mechanics have been verified experimentally to an extremely high degree of accuracy . For example, the refinement of quantum mechanics for the interaction of light and matter, known as quantum electrodynamics (QED), has been shown to agree with experiment to within 1 part in 10 12 when predicting the magnetic properties of an electron. [ 6 ] A fundamental feature of the theory is that it usually cannot predict with certainty what will happen, but only gives probabilities. Mathematically, a probability is found by taking the square of the absolute value of a complex number , known as a probability amplitude. This is known as the Born rule , named after physicist Max Born . For example, a quantum particle like an electron can be described by a wave function, which associates to each point in space a probability amplitude. Applying the Born rule to these amplitudes gives a probability density function for the position that the electron will be found to have when an experiment is performed to measure it. This is the best the theory can do; it cannot say for certain where the electron will be found. The Schr\u00f6dinger equation relates the collection of probability amplitudes that pertain to one moment of time to the collection of probability amplitudes that pertain to another. [ 7 ] : 67\u201387 One consequence of the mathematical rules of quantum mechanics is a tradeoff in predictability between measurable quantities. The most famous form of this uncertainty principle says that no matter how a quantum particle is prepared or how carefully experiments upon it are arranged, it is impossible to have a precise prediction for a measurement of its position and also at the same time for a measurement of its momentum . [ 7 ] : 427\u2013435 An illustration of the double-slit experiment Another consequence of the mathematical rules of quantum mechanics is the phenomenon of quantum interference , which is often illustrated with the double-slit experiment . In the basic version of this experiment, a coherent light source , such as a laser beam, illuminates a plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. [ 8 ] : 102\u2013111 [ 2 ] : 1.1\u20131.8 The wave nature of light causes the light waves passing through the two slits to interfere , producing bright and dark bands on the screen \u2013 a result that would not be expected if light consisted of classical particles. [ 8 ] However, the light is always found to be absorbed at the screen at discrete points, as individual particles rather than waves; the interference pattern appears via the varying density of these particle hits on the screen. Furthermore, versions of the experiment that include detectors at the slits find that each detected photon passes through one slit (as would a classical particle), and not through both slits (as would a wave). [ 8 ] : 109 [ 9 ] [ 10 ] However, such experiments demonstrate that particles do not form the interference pattern if one detects which slit they pass through. This behavior is known as wave\u2013particle duality . In addition to light, electrons , atoms , and molecules are all found to exhibit the same dual behavior when fired towards a double slit. [ 2 ] A simplified diagram of quantum tunneling , a phenomenon by which a particle may move through a barrier which would be impossible under classical mechanics Another non-classical phenomenon predicted by quantum mechanics is quantum tunnelling : a particle that goes up against a potential barrier can cross it, even if its kinetic energy is smaller than the maximum of the potential. [ 11 ] In classical mechanics this particle would be trapped. Quantum tunnelling has several important consequences, enabling radioactive decay , nuclear fusion in stars, and applications such as scanning tunnelling microscopy , tunnel diode and tunnel field-effect transistor . [ 12 ] [ 13 ] When quantum systems interact, the result can be the creation of quantum entanglement : their properties become so intertwined that a description of the whole solely in terms of the individual parts is no longer possible. Erwin Schr\u00f6dinger called entanglement \"... the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought\". [ 14 ] Quantum entanglement enables quantum computing and is part of quantum communication protocols, such as quantum key distribution and superdense coding . [ 15 ] Contrary to popular misconception, entanglement does not allow sending signals faster than light , as demonstrated by the no-communication theorem . [ 15 ] Another possibility opened by entanglement is testing for \" hidden variables \", hypothetical properties more fundamental than the quantities addressed in quantum theory itself, knowledge of which would allow more exact predictions than quantum theory provides. A collection of results, most significantly Bell's theorem , have demonstrated that broad classes of such hidden-variable theories are in fact incompatible with quantum physics. According to Bell's theorem, if nature actually operates in accord with any theory of local hidden variables, then the results of a Bell test will be constrained in a particular, quantifiable way. Many Bell tests have been performed and they have shown results incompatible with the constraints imposed by local hidden variables. [ 16 ] [ 17 ] It is not possible to present these concepts in more than a superficial way without introducing the mathematics involved; understanding quantum mechanics requires not only manipulating complex numbers, but also linear algebra , differential equations , group theory , and other more advanced subjects. [ 18 ] [ 19 ] Accordingly, this article will present a mathematical formulation of quantum mechanics and survey its application to some useful and oft-studied examples. Mathematical formulation Main article: Mathematical formulation of quantum mechanics In the mathematically rigorous formulation of quantum mechanics, the state of a quantum mechanical system is a vector \u03c8 {\\displaystyle \\psi } belonging to a ( separable ) complex Hilbert space H {\\displaystyle {\\mathcal {H}}} . This vector is postulated to be normalized under the Hilbert space inner product, that is, it obeys \u27e8 \u03c8 , \u03c8 \u27e9 = 1 {\\displaystyle \\langle \\psi ,\\psi \\rangle =1} , and it is well-defined up to a complex number of modulus 1 (the global phase), that is, \u03c8 {\\displaystyle \\psi } and e i \u03b1 \u03c8 {\\displaystyle e^{i\\alpha }\\psi } represent the same physical system. In other words, the possible states are points in the projective space of a Hilbert space, usually called the complex projective space . The exact nature of this Hilbert space is dependent on the system \u2013 for example, for describing position and momentum the Hilbert space is the space of complex square-integrable functions L 2 ( C ) {\\displaystyle L^{2}(\\mathbb {C} )} , [ 20 ] : 13 while the Hilbert space for the spin of a single proton is simply the space of two-dimensional complex vectors C 2 {\\displaystyle \\mathbb {C} ^{2}} with the usual inner product. [ 20 ] : 20 Physical quantities of interest \u2013 position, momentum, energy, spin \u2013 are represented by observables, which are Hermitian (more precisely, self-adjoint ) linear operators acting on the Hilbert space. [ 20 ] : 17 A quantum state can be an eigenvector of an observable, in which case it is called an eigenstate , and the associated eigenvalue corresponds to the value of the observable in that eigenstate. More generally, a quantum state will be a linear combination of the eigenstates, known as a quantum superposition . When an observable is measured, the result will be one of its eigenvalues with probability given by the Born rule : in the simplest case the eigenvalue \u03bb {\\displaystyle \\lambda } is non-degenerate and the probability is given by | \u27e8 \u03bb \u2192 , \u03c8 \u27e9 | 2 {\\displaystyle |\\langle {\\vec {\\lambda }},\\psi \\rangle |^{2}} , where \u03bb \u2192 {\\displaystyle {\\vec {\\lambda }}} is its associated unit-length eigenvector. More generally, the eigenvalue is degenerate and the probability is given by \u27e8 \u03c8 , P \u03bb \u03c8 \u27e9 {\\displaystyle \\langle \\psi ,P_{\\lambda }\\psi \\rangle } , where P \u03bb {\\displaystyle P_{\\lambda }} is the projector onto its associated eigenspace. [ 21 ] In the continuous case, these formulas give instead the probability density . After the measurement , if result \u03bb {\\displaystyle \\lambda } was obtained, the quantum state is postulated to collapse to \u03bb \u2192 {\\displaystyle {\\vec {\\lambda }}} , in the non-degenerate case, or to P \u03bb \u03c8 / \u27e8 \u03c8 , P \u03bb \u03c8 \u27e9 {\\textstyle P_{\\lambda }\\psi {\\big /}\\!{\\sqrt {\\langle \\psi ,P_{\\lambda }\\psi \\rangle }}} , in the general case. The probabilistic nature of quantum mechanics thus stems from the act of measurement. This is one of the most debated aspects of quantum theory, with different interpretations of quantum mechanics giving radically different answers to questions regarding quantum-state collapse, as discussed below . Time evolution of a quantum state The time evolution of a quantum state is described by the Schr\u00f6dinger equation: i \u210f \u2202 \u2202 t \u03c8 ( t ) = H \u03c8 ( t ) . {\\displaystyle i\\hbar {\\frac {\\partial }{\\partial t}}\\psi (t)=H\\psi (t).} Here H {\\displaystyle H} denotes the Hamiltonian , the observable corresponding to the total energy of the system, and \u210f {\\displaystyle \\hbar } is the reduced Planck constant . The constant i \u210f {\\displaystyle i\\hbar } is introduced so that the Hamiltonian is reduced to the classical Hamiltonian in cases where the quantum system can be approximated by a classical system; the ability to make such an approximation in certain limits is called the correspondence principle . The solution of this differential equation is given by \u03c8 ( t ) = e \u2212 i H t / \u210f \u03c8 ( 0 ) . {\\displaystyle \\psi (t)=e^{-iHt/\\hbar }\\psi (0).} The operator U ( t ) = e \u2212 i H t / \u210f {\\displaystyle U(t)=e^{-iHt/\\hbar }} is known as the time-evolution operator, and has the crucial property that it is unitary . This time evolution is deterministic in the sense that \u2013 given an initial quantum state \u03c8 ( 0 ) {\\displaystyle \\psi (0)} \u2013 it makes a definite prediction of what the quantum state \u03c8 ( t ) {\\displaystyle \\psi (t)} will be at any later time. [ 22 ] Fig. 1: Probability densities corresponding to the wave functions of an electron in a hydrogen atom possessing definite energy levels (increasing from the top of the image to the bottom: n = 1, 2, 3, ...) and angular momenta (increasing across from left to right: s , p , d , ...). Denser areas correspond to higher probability density in a position measurement. Such wave functions are directly comparable to Chladni's figures of acoustic modes of vibration in classical physics and are modes of oscillation as well, possessing a sharp energy and thus, a definite frequency. The angular momentum and energy are quantized and take only discrete values like those shown \u2013 as is the case for resonant frequencies in acoustics. Some wave functions produce probability distributions that are independent of time, such as eigenstates of the Hamiltonian. [ 7 ] : 133\u2013137 Many systems that are treated dynamically in classical mechanics are described by such \"static\" wave functions. For example, a single electron in an unexcited atom is pictured classically as a particle moving in a circular trajectory around the atomic nucleus , whereas in quantum mechanics, it is described by a static wave function surrounding the nucleus. For example, the electron wave function for an unexcited hydrogen atom is a spherically symmetric function known as an s orbital ( Fig. 1 ). Analytic solutions of the Schr\u00f6dinger equation are known for very few relatively simple model Hamiltonians including the quantum harmonic oscillator , the particle in a box , the dihydrogen cation , and the hydrogen atom . Even the helium atom \u2013 which contains just two electrons \u2013 has defied all attempts at a fully analytic treatment, admitting no solution in closed form . [ 23 ] [ 24 ] [ 25 ] However, there are techniques for finding approximate solutions. One method, called perturbation theory , uses the analytic result for a simple quantum mechanical model to create a result for a related but more complicated model by (for example) the addition of a weak potential energy . [ 7 ] : 793 Another approximation method applies to systems for which quantum mechanics produces only small deviations from classical behavior. These deviations can then be computed based on the classical motion. [ 7 ] : 849 Uncertainty principle One consequence of the basic quantum formalism is the uncertainty principle. In its most familiar form, this states that no preparation of a quantum particle can imply simultaneously precise predictions both for a measurement of its position and for a measurement of its momentum. [ 26 ] [ 27 ] Both position and momentum are observables, meaning that they are represented by Hermitian operators . The position operator X ^ {\\displaystyle {\\hat {X}}} and momentum operator P ^ {\\displaystyle {\\hat {P}}} do not commute, but rather satisfy the canonical commutation relation : [ X ^ , P ^ ] = i \u210f . {\\displaystyle [{\\hat {X}},{\\hat {P}}]=i\\hbar .} Given a quantum state, the Born rule lets us compute expectation values for both X {\\displaystyle X} and P {\\displaystyle P} , and moreover for powers of them. Defining the uncertainty for an observable by a standard deviation , we have \u03c3 X = \u27e8 X 2 \u27e9 \u2212 \u27e8 X \u27e9 2 , {\\displaystyle \\sigma _{X}={\\textstyle {\\sqrt {\\left\\langle X^{2}\\right\\rangle -\\left\\langle X\\right\\rangle ^{2}}}},} and likewise for the momentum: \u03c3 P = \u27e8 P 2 \u27e9 \u2212 \u27e8 P \u27e9 2 . {\\displaystyle \\sigma _{P}={\\sqrt {\\left\\langle P^{2}\\right\\rangle -\\left\\langle P\\right\\rangle ^{2}}}.} The uncertainty principle states that \u03c3 X \u03c3 P \u2265 \u210f 2 . {\\displaystyle \\sigma _{X}\\sigma _{P}\\geq {\\frac {\\hbar }{2}}.} Either standard deviation can in principle be made arbitrarily small, but not both simultaneously. [ 28 ] This inequality generalizes to arbitrary pairs of self-adjoint operators A {\\displaystyle A} and B {\\displaystyle B} . The commutator of these two operators is [ A , B ] = A B \u2212 B A , {\\displaystyle [A,B]=AB-BA,} and this provides the lower bound on the product of standard deviations: \u03c3 A \u03c3 B \u2265 1 2 | \u27e8 [ A , B ] \u27e9 | . {\\displaystyle \\sigma _{A}\\sigma _{B}\\geq {\\tfrac {1}{2}}\\left|{\\bigl \\langle }[A,B]{\\bigr \\rangle }\\right|.} Another consequence of the canonical commutation relation is that the position and momentum operators are Fourier transforms of each other, so that a description of an object according to its momentum is the Fourier transform of its description according to its position. The fact that dependence in momentum is the Fourier transform of the dependence in position means that the momentum operator is equivalent (up to an i / \u210f {\\displaystyle i/\\hbar } factor) to taking the derivative according to the position, since in Fourier analysis differentiation corresponds to multiplication in the dual space . This is why in quantum equations in position space, the momentum p i {\\displaystyle p_{i}} is replaced by \u2212 i \u210f \u2202 \u2202 x {\\displaystyle -i\\hbar {\\frac {\\partial }{\\partial x}}} , and in particular in the non-relativistic Schr\u00f6dinger equation in position space the momentum-squared term is replaced with a Laplacian times \u2212 \u210f 2 {\\displaystyle -\\hbar ^{2}} . [ 26 ] Composite systems and entanglement When two different quantum systems are considered together, the Hilbert space of the combined system is the tensor product of the Hilbert spaces of the two components. For example, let A and B be two quantum systems, with Hilbert spaces H A {\\displaystyle {\\mathcal {H}}_{A}} and H B {\\displaystyle {\\mathcal {H}}_{B}} , respectively. The Hilbert space of the composite system is then H A B = H A \u2297 H B . {\\displaystyle {\\mathcal {H}}_{AB}={\\mathcal {H}}_{A}\\otimes {\\mathcal {H}}_{B}.} If the state for the first system is the vector \u03c8 A {\\displaystyle \\psi _{A}} and the state for the second system is \u03c8 B {\\displaystyle \\psi _{B}} , then the state of the composite system is \u03c8 A \u2297 \u03c8 B . {\\displaystyle \\psi _{A}\\otimes \\psi _{B}.} Not all states in the joint Hilbert space H A B {\\displaystyle {\\mathcal {H}}_{AB}} can be written in this form, however, because the superposition principle implies that linear combinations of these \"separable\" or \"product states\" are also valid. For example, if \u03c8 A {\\displaystyle \\psi _{A}} and \u03d5 A {\\displaystyle \\phi _{A}} are both possible states for system A {\\displaystyle A} , and likewise \u03c8 B {\\displaystyle \\psi _{B}} and \u03d5 B {\\displaystyle \\phi _{B}} are both possible states for system B {\\displaystyle B} , then 1 2 ( \u03c8 A \u2297 \u03c8 B + \u03d5 A \u2297 \u03d5 B ) {\\displaystyle {\\tfrac {1}{\\sqrt {2}}}\\left(\\psi _{A}\\otimes \\psi _{B}+\\phi _{A}\\otimes \\phi _{B}\\right)} is a valid joint state that is not separable. States that are not separable are called entangled . [ 29 ] [ 30 ] If the state for a composite system is entangled, it is impossible to describe either component system A or system B by a state vector. One can instead define reduced density matrices that describe the statistics that can be obtained by making measurements on either component system alone. This necessarily causes a loss of information, though: knowing the reduced density matrices of the individual systems is not enough to reconstruct the state of the composite system. [ 29 ] [ 30 ] Just as density matrices specify the state of a subsystem of a larger system, analogously, positive operator-valued measures (POVMs) describe the effect on a subsystem of a measurement performed on a larger system. POVMs are extensively used in quantum information theory. [ 29 ] [ 31 ] As described above, entanglement is a key feature of models of measurement processes in which an apparatus becomes entangled with the system being measured. Systems interacting with the environment in which they reside generally become entangled with that environment, a phenomenon known as quantum decoherence . This can explain why, in practice, quantum effects are difficult to observe in systems larger than microscopic. [ 32 ] Equivalence between formulations There are many mathematically equivalent formulations of quantum mechanics. One of the oldest and most common is the \" transformation theory \" proposed by Paul Dirac , which unifies and generalizes the two earliest formulations of quantum mechanics \u2013 matrix mechanics (invented by Werner Heisenberg ) and wave mechanics (invented by Erwin Schr\u00f6dinger ). [ 33 ] An alternative formulation of quantum mechanics is Feynman 's path integral formulation , in which a quantum-mechanical amplitude is considered as a sum over all possible classical and non-classical paths between the initial and final states. This is the quantum-mechanical counterpart of the action principle in classical mechanics. [ 34 ] Symmetries and conservation laws Main article: Noether's theorem The Hamiltonian H {\\displaystyle H} is known as the generator of time evolution, since it defines a unitary time-evolution operator U ( t ) = e \u2212 i H t / \u210f {\\displaystyle U(t)=e^{-iHt/\\hbar }} for each value of t {\\displaystyle t} . From this relation between U ( t ) {\\displaystyle U(t)} and H {\\displaystyle H} , it follows that any observable A {\\displaystyle A} that commutes with H {\\displaystyle H} will be conserved : its expectation value will not change over time. [ 7 ] : 471 This statement generalizes, as mathematically, any Hermitian operator A {\\displaystyle A} can generate a family of unitary operators parameterized by a variable t {\\displaystyle t} . Under the evolution generated by A {\\displaystyle A} , any observable B {\\displaystyle B} that commutes with A {\\displaystyle A} will be conserved. Moreover, if B {\\displaystyle B} is conserved by evolution under A {\\displaystyle A} , then A {\\displaystyle A} is conserved under the evolution generated by B {\\displaystyle B} . This implies a quantum version of the result proven by Emmy Noether in classical ( Lagrangian ) mechanics: for every differentiable symmetry of a Hamiltonian, there exists a corresponding conservation law . Examples Free particle Main article: Free particle Position space probability density of a Gaussian wave packet moving in one dimension in free space The simplest example of a quantum system with a position degree of freedom is a free particle in a single spatial dimension. A free particle is one which is not subject to external influences, so that its Hamiltonian consists only of its kinetic energy: H = 1 2 m P 2 = \u2212 \u210f 2 2 m d 2 d x 2 . {\\displaystyle H={\\frac {1}{2m}}P^{2}=-{\\frac {\\hbar ^{2}}{2m}}{\\frac {d^{2}}{dx^{2}}}.} The general solution of the Schr\u00f6dinger equation is given by \u03c8 ( x , t ) = 1 2 \u03c0 \u222b \u2212 \u221e \u221e \u03c8 ^ ( k , 0 ) e i ( k x \u2212 \u210f k 2 2 m t ) d k , {\\displaystyle \\psi (x,t)={\\frac {1}{\\sqrt {2\\pi }}}\\int _{-\\infty }^{\\infty }{\\hat {\\psi }}(k,0)e^{i(kx-{\\frac {\\hbar k^{2}}{2m}}t)}\\mathrm {d} k,} which is a superposition of all possible plane waves e i ( k x \u2212 \u210f k 2 2 m t ) {\\displaystyle e^{i(kx-{\\frac {\\hbar k^{2}}{2m}}t)}} , which are eigenstates of the momentum operator with momentum p = \u210f k {\\displaystyle p=\\hbar k} . The coefficients of the superposition are \u03c8 ^ ( k , 0 ) {\\displaystyle {\\hat {\\psi }}(k,0)} , which is the Fourier transform of the initial quantum state \u03c8 ( x , 0 ) {\\displaystyle \\psi (x,0)} . It is not possible for the solution to be a single momentum eigenstate, or a single position eigenstate, as these are not normalizable quantum states. {{rp|100\u2013105}}\"}},\"i\":0}}]}'> [ note 1 ] Instead, we can consider a Gaussian wave packet : \u03c8 ( x , 0 ) = 1 \u03c0 a 4 e \u2212 x 2 2 a {\\displaystyle \\psi (x,0)={\\frac {1}{\\sqrt[{4}]{\\pi a}}}e^{-{\\frac {x^{2}}{2a}}}} which has Fourier transform, and therefore momentum distribution \u03c8 ^ ( k , 0 ) = a \u03c0 4 e \u2212 a k 2 2 . {\\displaystyle {\\hat {\\psi }}(k,0)={\\sqrt[{4}]{\\frac {a}{\\pi }}}e^{-{\\frac {ak^{2}}{2}}}.} We see that as we make a {\\displaystyle a} smaller the spread in position gets smaller, but the spread in momentum gets larger. Conversely, by making a {\\displaystyle a} larger we make the spread in momentum smaller, but the spread in position gets larger. This illustrates the uncertainty principle. As we let the Gaussian wave packet evolve in time, we see that its center moves through space at a constant velocity (like a classical particle with no forces acting on it). However, the wave packet will also spread out as time progresses, which means that the position becomes more and more uncertain. The uncertainty in momentum, however, stays constant. [ 35 ] Particle in a box 1-dimensional potential energy box (or infinite potential well) Main article: Particle in a box The particle in a one-dimensional potential energy box is the most mathematically simple example where restraints lead to the quantization of energy levels. The box is defined as having zero potential energy everywhere inside a certain region, and therefore infinite potential energy everywhere outside that region. [ 26 ] : 77\u201378 For the one-dimensional case in the x {\\displaystyle x} direction, the time-independent Schr\u00f6dinger equation may be written \u2212 \u210f 2 2 m d 2 \u03c8 d x 2 = E \u03c8 . {\\displaystyle -{\\frac {\\hbar ^{2}}{2m}}{\\frac {d^{2}\\psi }{dx^{2}}}=E\\psi .} With the differential operator defined by p ^ x = \u2212 i \u210f d d x {\\displaystyle {\\hat {p}}_{x}=-i\\hbar {\\frac {d}{dx}}} the previous equation is evocative of the classic kinetic energy analogue , 1 2 m p ^ x 2 = E , {\\displaystyle {\\frac {1}{2m}}{\\hat {p}}_{x}^{2}=E,} with state \u03c8 {\\displaystyle \\psi } in this case having energy E {\\displaystyle E} coincident with the kinetic energy of the particle. The general solutions of the Schr\u00f6dinger equation for the particle in a box are \u03c8 ( x", "French Revolution 1789\u20131799 sociopolitical change in France .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} For other uses, see French Revolution (disambiguation) . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> (10 years, 6 months, and 4 days)\"},\"Result\":{\"wt\":\"* [[Proclamation of the abolition of the monarchy|Abolition]] of the ''[[Ancien r\u00e9gime]]'' and creation of [[Constitutional Cabinet of Louis XVI|constitutional monarchy]]\\n* Proclamation of the [[French First Republic]] in September 1792\\n* [[Reign of Terror]] and [[execution of Louis XVI]]\\n* [[French Revolutionary Wars]]\\n* Establishment of the [[French Consulate]] in November 1799\"}},\"i\":0}}]}' id=\"mwEQ\">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent;color:inherit}.mw-parser-output .infobox-3cols-child{margin:-3px}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}} French Revolution Part of the Atlantic Revolutions The Storming of the Bastille , 14 July 1789 Date 5 May 1789 \u2013 9 November 1799 (10 years, 6 months, and 4 days) Location France Outcome Abolition of the Ancien r\u00e9gime and creation of constitutional monarchy Proclamation of the French First Republic in September 1792 Reign of Terror and execution of Louis XVI French Revolutionary Wars Establishment of the French Consulate in November 1799 The French Revolution [ a ] was a period of political and societal change in France that began with the Estates General of 1789 and ended with the Coup of 18 Brumaire on 9 November 1799. Many of the revolution's ideas are considered fundamental principles of liberal democracy , [ 1 ] and its values remain central to modern French political discourse. [ 2 ] It was caused by a combination of social, political, and economic factors which the existing regime proved unable to manage. Financial crisis and widespread social distress led to the convocation of the Estates General in May 1789, its first meeting since 1614. The representatives of the Third Estate broke away and re-constituted themselves as a National Assembly in June. The Storming of the Bastille in Paris on 14 July led to a series of radical measures by the Assembly, including the abolition of feudalism , state control over the Catholic Church in France , and issuing the Declaration of the Rights of Man and of the Citizen . The next three years were dominated by a struggle for political control. King Louis XVI 's attempted flight to Varennes in June 1791 further discredited the monarchy, and military defeats after the outbreak of the French Revolutionary Wars in April 1792 led to the insurrection of 10 August 1792 . As a result, the monarchy was replaced by the French First Republic in September, followed by the execution of Louis XVI himself in January 1793. After another revolt in June 1793 , the constitution was suspended, and political power passed from the National Convention to the Committee of Public Safety , dominated by radical Jacobins led by Maximilien Robespierre . About 16,000 people were sentenced by the Revolutionary Tribunal and executed in the Reign of Terror , which ended in July 1794 with the Thermidorian Reaction . Weakened by external threats and internal opposition, the Committee of Public Safety was replaced in November 1795 by the Directory . Its instability ended in 1799 with the coup of 18 Brumaire and the establishment of the Consulate , with Napoleon Bonaparte as First Consul. 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screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} Part of a series on the History of France Timeline Ancient Prehistory Greek colonies 600 BC \u2013 49 BC Celtic Gaul until 50 BC Roman Gaul 50 BC \u2013 486 AD Middle Ages Francia and the Frankish settlement Merovingians 481\u2013751 Carolingians 751\u2013987 West Francia 843\u2013987 Kingdom of France 987\u20131792 Direct Capetians 987\u20131328 Valois 1328\u20131498 Early modern Ancien R\u00e9gime Valois-Orl\u00e9ans kings 1498\u20131515 Valois-Angoul\u00eame kings 1515\u20131589 Bourbon kings 1589\u20131792 Long 19th century French Revolution 1789\u20131799 Kingdom of France 1791\u20131792 First Republic 1792\u20131804 First Empire 1804\u20131814 Restoration 1814\u20131830 July Monarchy 1830\u20131848 Second Republic 1848\u20131852 Second Empire 1852\u20131870 Third Republic 1870\u20131940 Belle \u00c9poque 1871\u20131914 20th century Third Republic 1870\u20131940 Interwar period 1919\u20131939 Ann\u00e9es folles 1920\u20131929 Free France Vichy France 1940\u20131944 Provisional Republic 1944\u20131946 Fourth Republic 1946\u20131958 Fifth Republic 1958\u2013 present Topics Diplomacy Economy Health care Law LGBTQ Medicine Military Monarchs Consorts Politics Religion Taxation Territory France portal \u00b7 History portal .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e Main article: Causes of the French Revolution The Revolution resulted from multiple long-term and short-term factors, culminating in a social, economic, financial and political crisis in the late 1780s. [ 3 ] [ 4 ] [ 5 ] Combined with resistance to reform by the ruling elite and indecisive policy by Louis XVI and his ministers, the result was a crisis the state was unable to manage. [ 6 ] [ 7 ] Between 1715 and 1789, the French population grew from 21 to 28 million, 20% of whom lived in towns or cities, Paris alone having over 600,000 inhabitants. [ 8 ] This was accompanied by a tripling in the size of the middle class, which comprised almost 10% of the population by 1789. [ 9 ] Despite increases in overall prosperity, its benefits were largely restricted to the rentier and mercantile classes, while the living standards fell for wage labourers and peasant farmers who rented their land. [ 10 ] [ 11 ] Economic recession from 1785, combined with bad harvests in 1787 and 1788, led to high unemployment and food prices, causing a financial and political crisis. [ 3 ] [ 12 ] [ 13 ] [ 14 ] While the state also experienced a debt crisis, the level of debt itself was not high compared with Britain's. [ 15 ] A significant problem was that tax rates varied widely from one region to another, were often different from the official amounts, and were collected inconsistently. The complexity and lack of accountability caused resentment among all taxpayers. [ 16 ] [ b ] Attempts to simplify the system were blocked by the regional Parlements which approved financial policy. The resulting impasse led to the calling of the Estates General of 1789 , which became radicalised by the struggle for control of public finances. [ 18 ] Louis XVI was willing to consider reforms, but he often backed down when faced with opposition from conservative elements within the nobility. Enlightenment critiques of social institutions were widely discussed among the educated French elite. At the same time, the American Revolution and the European revolts of the 1780s inspired public debate on issues such as patriotism, liberty, equality, and democracy. These shaped the response of the educated public to the crisis, [ 19 ] while scandals such as the Affair of the Diamond Necklace fuelled widespread anger at the court, nobility, and church officials. [ 20 ] Crisis of the Ancien R\u00e9gime The regional Parlements in 1789; note area covered by the Parlement of Paris Financial and political crisis France faced a series of budgetary crises during the 18th century as revenues failed to keep pace with expenditure. [ 21 ] [ 22 ] Despite solid economic growth, the use of tax farmers meant this was not reflected in a proportional growth in state tax income. [ 21 ] As the nobility and Church benefited from a variety of exemptions, the tax burden fell mainly on the lower classes. [ 23 ] Reform was difficult because new tax laws had to be registered with regional judicial bodies or parlements that were able to block them. The king could impose laws by decree, but this risked open conflict with the parlements , the nobility, and those subject to new taxes. [ 24 ] France primarily used loans to fund the 1778 to 1783 Anglo-French War . Even after it ended , the monarchy continued to borrow heavily, and by 1788, half of state revenue went on servicing its debt. [ 25 ] [ 26 ] In 1786, the French finance minister, Calonne , proposed reforms including a universal land tax, the abolition of grain controls and internal tariffs, and new provincial assemblies appointed by the king. The new taxes were rejected, first by a hand-picked Assembly of Notables dominated by the nobility, then by the parlements when submitted by Calonne's successor Brienne . The notables and parlements argued that the proposed taxes could only be approved by an Estates-General, a representative body that last met in 1614. [ 27 ] The conflict between the Crown and the parlements became a national political crisis. Both sides issued a series of public statements, the government arguing that it was combating privilege, and the parlement defending the ancient rights of the nation. Public opinion was firmly on the side of the parlements , and riots broke out in several towns. Brienne's attempts to raise new loans failed, and on 8 August 1788, he announced that the king would summon an Estates-General to convene the following May. Brienne resigned and was replaced by Jacques Necker . [ 28 ] In September 1788, the Parlement of Paris ruled that the Estates-General should convene in the same form as in 1614, meaning that the three estates would meet and vote separately, with votes counted by estate rather than by head. As a result, the clergy and nobility could combine to outvote the Third Estate, despite representing less than 5% of the population. [ 29 ] [ 30 ] With the relaxation of censorship and laws against political clubs, a group of liberal nobles and middle class activists known as the Society of Thirty launched a campaign for the doubling of Third Estate representation and individual voting. The public debate sparked an average of 25 new political pamphlets published each week from 25 September 1788. [ 31 ] One of the most influential was written by Abb\u00e9 Siey\u00e8s . Titled What Is the Third Estate? , it denounced the privilege of the clergy and nobility, and argued the Third Estate represented the nation and should sit alone as a National Assembly. Activists such as Jean Joseph Mounier , Antoine Barnave and Maximilien Robespierre organised regional meetings, petitions and literature in support of these demands. [ 32 ] In December, the king agreed to double the representation of the Third Estate, but left the question of counting votes for the Estates-General to decide. [ 33 ] Estates-General of 1789 Main article: Estates General of 1789 in France Caricature of the Third Estate carrying the First Estate (clergy) and the Second Estate (nobility) on its back The Catholic Church in France was wealthy, owning nearly 10% of all land, as well as receiving annual tithes . [ 34 ] However, three-quarters of the 303 clergy elected were parish priests, many of whom earned less than unskilled labourers and had more in common with their poor parishioners than with the bishops of the first estate. [ 35 ] The Second Estate elected 322 deputies, representing about 400,000 men and women, who owned about 25% of the land and collected seigneurial dues and rents from their tenants. Most delegates were town-dwelling members of the noblesse d'\u00e9p\u00e9e , or traditional aristocracy. Courtiers and representatives of the noblesse de robe (those who derived rank from judicial or administrative posts) were underrepresented. [ 36 ] Of the 610 deputies of the Third Estate, about two-thirds held legal qualifications and almost half were venal office holders. Less than 100 were in trade or industry, and none were peasants or artisans. [ 37 ] To assist delegates, each region completed a list of grievances, known as Cahiers de dol\u00e9ances . [ 38 ] Tax inequality and seigneurial dues (feudal payments owed to landowners) headed the grievances in the cahiers de doleances for the estate. [ 39 ] On 5 May 1789, the Estates-General convened at Versailles , with Necker reiterating that each estate should decide separately how and when it would meet and vote in common with the other estates. On the following day, each estate was to separately verify the credentials of their representatives. The Third Estate, however, voted to invite the other estates to join them in verifying all the representatives of the Estates-General in common, and to agree that votes should be counted by head. Negotiations continued until 12 June when the Third Estate unilaterally began verifying its own members. On 17th, the Third Estate declared itself to be the National Assembly of France and that all existing taxes were illegal. [ 40 ] Le Serment du Jeu de paume by Jacques-Louis David ( c. 1791 ), depicting the Tennis Court Oath By 19 June, they had been joined by more than 100 members of the clergy. [ 41 ] Shaken by this challenge to his authority, the king agreed to a reform package he would present personally to the Estates-General. The Salle des \u00c9tats was closed to prepare for the joint session, but the members of the Estates-General were not informed in advance. Finding their meeting place closed next day, they took the so-called Tennis Court Oath , undertaking not to disperse until a constitution had been agreed. [ 42 ] At the royal session, Louis XVI announced a series of reforms and stated no new taxes or loans would be implemented without the consent of the Estates-General. However, he then undermined this by re-stating his original demand for all three to sit and vote separately. The Third Estate refused to leave the hall and reiterated their oath not to disperse until a constitution had been agreed. Over the next days more members of the clergy joined the National Assembly. On 27 June, faced with popular demonstrations and mutinies in his French Guards , Louis XVI commanded the members of the first and second estates to join the third in the National Assembly. [ 43 ] Constitutional monarchy (July 1789 \u2013 September 1792) Abolition of the Ancien R\u00e9gime Even the limited reforms the king had announced went too far for Marie Antoinette and Louis' younger brother the Comte d'Artois . On their advice, Louis dismissed Necker again as chief minister on 11 July. [ 44 ] On 12 July, the Assembly went into a non-stop session following rumours that the king was planning to use the Swiss Guards to force it to close. The news brought crowds of protestors into the streets, and soldiers of the elite Gardes Fran\u00e7aises refused to disperse them. [ 45 ] On 14 July many of these soldiers joined a crowd attacking the Bastille , a royal fortress with large stores of arms and ammunition. Its governor, Bernard-Ren\u00e9 de Launay , surrendered after several hours of fighting that cost the lives of 83 attackers. Launay was taken to the H\u00f4tel de Ville , where he was killed and his head placed on a pike and paraded around the city. Although rumoured to hold many prisoners, the Bastille held only seven: four forgers, a lunatic, a failed assassin, and a deviant nobleman. Nevertheless, it was a potent symbol of the Ancien R\u00e9gime and it was demolished in the following weeks. [ 46 ] Bastille Day has become the French national holiday. [ 47 ] The Storming of the Bastille on 14 July 1789; the iconic event of the Revolution, still commemorated each year as Bastille Day Alarmed by the prospect of losing control of the capital, Louis appointed the Marquis de Lafayette commander of the National Guard , with Jean-Sylvain Bailly as head of a new administrative structure known as the Commune . On 17 July, Louis visited Paris accompanied by 100 deputies, where he was greeted by Bailly and accepted a tricolore cockade to loud cheers. However, it was clear power had shifted from his court; he was welcomed as 'Louis XVI, father of the French and king of a free people.' [ 48 ] The short-lived unity enforced on the Assembly by a common threat quickly dissipated. Deputies argued over constitutional forms, while civil authority rapidly deteriorated. On 22 July, former Finance Minister Joseph Foullon and his son were lynched by a Parisian mob, and neither Bailly nor Lafayette could prevent it. In rural areas, wild rumours and paranoia resulted in the formation of militia and an agrarian insurrection known as the Great Fear . [ 49 ] The breakdown of law and order and frequent attacks on aristocratic property led much of the nobility to flee abroad. These \u00e9migr\u00e9s funded reactionary forces within France and urged foreign monarchs to back a counter-revolution . [ 50 ] In response, the Assembly published the August Decrees which abolished feudalism . Over 25% of French farmland was subject to feudal dues , providing the nobility with most of their income; these were now cancelled, along with church tithes. While their former tenants were supposed to pay them compensation, collecting it proved impossible, and the obligation was annulled in 1793. [ 51 ] Other decrees included equality before the law, opening public office to all, freedom of worship, and cancellation of special privileges held by provinces and towns. [ 52 ] With the suspension of the 13 regional parlements in November, the key institutional pillars of the old regime had all been abolished in less than four months. From its early stages, the Revolution therefore displayed signs of its radical nature; what remained unclear was the constitutional mechanism for turning intentions into practical applications. [ 53 ] Creating a constitution Part of a series on Revolution Liberty Leading the People</i>, depicting the 1830 July Revolution in France\"}'> Characteristics Bourgeois Colour Communist Counter-revolutionary Democratic Nonviolent Passive Permanent Proletarian From above Wave Social Methods Boycott Civil disorder Civil war Class struggle Contentious politics Coup d'\u00e9tat Demonstration Human chain Direct action Guerrilla warfare Insurgency Mass mobilization Mutiny Protest Rebellion Resistance Nonviolent Civil Disobedience Riot Samizdat Strike action Tax resistance Terror Examples English American Brabant Li\u00e8ge French Haitian Spanish American Serbian Greek 1820s 1830 July Belgian Texas 1848 Italian states February German Hungarian Eureka Bulgarian unification Philippine Iranian First Second Young Turk Mexican Chinese Xinhai Communist Cultural 1917\u20131923 Russian German Siamese Spanish August Guatemalan Indonesian Hungarian (1956) Cuban Rwandan Nicaraguan Argentine Carnation Saur People Power 1989 Yogurt Velvet Romanian Singing Bolivarian Bulldozer Rose Orange Tulip Kyrgyz Arab Spring Tunisian Egyptian Yemeni Euromaidan Second Arab Spring Sudanese Gen Z Bangladeshi July Nepal Politics portal v t e On 9 July, the National Assembly declared itself the National Constituent Assembly [ 54 ] and appointed a committee to draft a constitution and statement of rights. [ 55 ] Twenty drafts were submitted, which were used by a sub-committee to create a Declaration of the Rights of Man and of the Citizen , with Mirabeau being the most prominent member. [ 56 ] The declaration was approved by the Assembly and published on 26 August as a statement of principle. [ 57 ] The Assembly now concentrated on the constitution. Mounier and his monarchist supporters advocated a bicameral system, with an upper house appointed by the king, who would also have the right to appoint ministers and veto legislation. On 10 September, the majority of the Assembly, led by Siey\u00e8s and Talleyrand , voted in favour of a single body, and the following day approved a \" suspensive veto \" for the king, meaning Louis could delay implementation of a law but not block it indefinitely. In October, the Assembly voted to restrict political rights, including voting rights, to \" active citizens \", defined as French males over the age of 25 who paid direct taxes equal to three days' labour. The remainder were designated \"passive citizens\", restricted to \"civil rights\", a distinction opposed by a significant minority, including the Jacobin clubs . [ 58 ] [ 59 ] By mid-1790, the main elements of a constitutional monarchy were in place, although the constitution was not accepted by Louis until 1791. [ 60 ] Food shortages and the worsening economy caused frustration at the lack of progress and led to popular unrest in Paris. This came to a head in late September 1789, when the Flanders Regiment arrived in Versailles to reinforce the royal bodyguard and were welcomed with a formal banquet as was common practice. The radical press described this as a 'gluttonous orgy' and claimed the tricolour cockade had been abused, while the Assembly viewed their arrival as an attempt to intimidate them. [ 61 ] On 5 October, crowds of women assembled outside the H\u00f4tel de Ville , agitating against high food prices and shortages. [ 62 ] These protests quickly turned political, and after seizing weapons stored at the H\u00f4tel de Ville, some 7,000 of them marched on Versailles , where they entered the Assembly to present their demands. They were followed to Versailles by 15,000 members of the National Guard under Lafayette, who was virtually \"a prisoner of his own troops\". [ 63 ] When the National Guard arrived later that evening, Lafayette persuaded Louis that the safety of his family required their relocation to Paris. Next morning, some of the protestors broke into the royal apartments, searching for Marie Antoinette, who had escaped. They ransacked the palace, killing several guards. Order was eventually restored, and the royal family and Assembly left for Paris, escorted by the National Guard. [ 64 ] Louis had announced his acceptance of the August Decrees and the declaration, and his official title changed from 'King of France' to 'King of the French'. [ 65 ] Catholic Church Historian John McManners argues \"in eighteenth-century France, throne and altar were commonly spoken of as in close alliance; their simultaneous collapse ... would one day provide the final proof of their interdependence.\" One suggestion is that after a century of persecution, some French Protestants actively supported an anti-Catholic regime, a resentment fuelled by Enlightenment thinkers such as Voltaire . [ 66 ] Jean-Jacques Rousseau , considered a philosophical founder of the revolution, [ 67 ] [ 68 ] [ 69 ] wrote it was \"manifestly contrary to the law of nature ... that a handful of people should gorge themselves with superfluities, while the hungry multitude goes in want of necessities.\" [ 70 ] In this caricature, monks and nuns enjoy their new freedom after the decree of 16 February 1790. The Revolution caused a massive shift of power from the Catholic Church to the state; although the extent of religious belief has been questioned, elimination of tolerance for religious minorities meant by 1789 being French also meant being Catholic. [ 71 ] The church was the largest individual landowner in France, controlling nearly 10% of all estates and levied tithes , effectively a 10% tax on income, collected from peasant farmers in the form of crops. In return, it provided a minimal level of social support. [ 72 ] The August Decrees abolished tithes, and on 2 November the Assembly confiscated all church property, the value of which was used to back a new paper currency known as assignats . In return, the state assumed responsibilities such as paying the clergy and caring for the poor, the sick and the orphaned. [ 73 ] On 13 February 1790, religious orders and monasteries were dissolved, while monks and nuns were encouraged to return to private life. [ 74 ] The Civil Constitution of the Clergy of 12 July 1790 made them employees of the state, established rates of pay, and developed a system for electing priests and bishops. Pope Pius VI and many French Catholics objected to this since it denied the authority of the Pope over the French church. In October, 30 bishops wrote a declaration denouncing the law, further fuelling opposition. [ 75 ] When clergy were required to swear loyalty to the Civil Constitution in November, it split the church between the 24% who complied and the majority who refused. [ 76 ] This stiffened popular resistance against state interference, especially in traditionally Catholic areas such as Normandy , Brittany and the Vend\u00e9e , where only a few priests took the oath and the civilian population turned against the revolution. [ 75 ] The result was state-led persecution of \" refractory clergy \", many of whom were forced into exile, deported, or executed. [ 77 ] Political divisions The period from October 1789 to spring 1791 is usually seen as one of relative tranquility, when some of the most important legislative reforms were enacted. However, conflict over the source of legitimate authority was more apparent in the provinces, where officers of the Ancien R\u00e9gime had been swept away but not yet replaced by new structures. This was less obvious in Paris, since the National Guard made it the best policed city in Europe, but disorder in the provinces inevitably affected members of the Assembly. [ 78 ] The F\u00eate de la F\u00e9d\u00e9ration on 14 July 1790 celebrated the establishment of the constitutional monarchy. Centrists led by Siey\u00e8s, Lafayette, Mirabeau and Bailly created a majority by forging consensus with monarchiens like Mounier, and independents including Adrien Duport , Barnave and Alexandre Lameth . At one end of the political spectrum, reactionaries like Cazal\u00e8s and Maury denounced the Revolution in all its forms, with radicals like Maximilien Robespierre at the other. He and Jean-Paul Marat opposed the criteria for \"active citizens\", gaining them substantial support among the Parisian proletariat, many of whom had been disenfranchised by the measure. [ 79 ] On 14 July 1790, celebrations were held throughout France commemorating the fall of the Bastille, with participants swearing an oath of fidelity to \"the nation, the law and the king.\" The F\u00eate de la F\u00e9d\u00e9ration in Paris was attended by the royal family, with Talleyrand performing a mass . Despite this show of unity, the Assembly was increasingly divided, while external players like the Paris Commune and National Guard competed for power. One of the most significant was the Jacobin club; originally a forum for general debate, by August 1790 it had over 150 members, split into different factions. [ 80 ] The Assembly continued to develop new institutions; in September 1790, the regional Parlements were abolished and their legal functions replaced by a new independent judiciary, with jury trials for criminal cases. However, moderate deputies were uneasy at popular demands for universal suffrage, labour unions and cheap bread, and over the winter of 1790 and 1791, they passed a series of measures intended to disarm popular radicalism. These included exclusion of poorer citizens from the National Guard, limits on use of petitions and posters, and the June 1791 Le Chapelier Law suppressing trade guilds and any form of worker organisation. [ 81 ] The traditional force for preserving law and order was the army, which was increasingly divided between officers, who largely came from the nobility, and ordinary soldiers. In August 1790, the loyalist General Bouill\u00e9 suppressed a serious mutiny at Nancy ; although congratulated by the Assembly, he was criticised by Jacobin radicals for the severity of his actions. Growing disorder meant many professional officers either left or became \u00e9migr\u00e9s, further destabilising the institution. [ 82 ] Varennes and after Main article: Flight to Varennes Held in the Tuileries Palace under virtual house arrest, Louis XVI was urged by his brother and wife to re-assert his independence by taking refuge with Bouill\u00e9, who was based at Montm\u00e9dy with 10,000 soldiers considered loyal to the Crown. [ 83 ] The royal family left the palace in disguise on the night of 20 June 1791; late the next day, Louis was recognised as he passed through Varennes , arrested and taken back to Paris. The attempted escape had a profound impact on public opinion; since it was clear Louis had been seeking refuge in Austria, the Assembly now demanded oaths of loyalty to the regime and began preparing for war, while fear of 'spies and traitors' became pervasive. [ 84 ] After the Flight to Varennes ; the royal family are escorted back to Paris Despite calls to replace the monarchy with a republic, Louis retained his position but was generally regarded with acute suspicion and forced to swear allegiance to the constitution. A new decree stated retracting this oath, making war upon the nation, or permitting anyone to do so in his name would be considered abdication. However, radicals led by Jacques Pierre Brissot prepared a petition demanding his deposition, and on 17 July, an immense crowd gathered in the Champ de Mars to sign. Led by Lafayette, the National Guard was ordered to \"preserve public order\" and responded to", "DNA Molecule that carries genetic information .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} For a non-technical introduction to the topic, see Introduction to genetics . For other uses, see DNA (disambiguation) . <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected due to vandalism\\\" id=\\\"mwCA\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCQ\\\"/></a></span>\"}' id=\"mwCg\"/> Chromosome ( 10 7 - 10 10 bp ) DNA Gene ( 10 3 - 10 6 bp ) Function A chromosome and its packaged long strand of DNA unraveled. The DNA's base pairs encode genes, which provide functions. A human DNA can have up to 500 million base pairs with thousands of genes. The structure of the DNA double helix (type B-DNA ). The atoms in the structure are colour-coded by element and the detailed structures of two base pairs are shown in the bottom right. 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.sidebar-left{float:left;clear:left;margin:0.5em 1em 1em 0}.mw-parser-output .sidebar-none{float:none;clear:both;margin:0.5em 1em 1em 0}.mw-parser-output .sidebar-outer-title{padding:0 0.4em 0.2em;font-size:125%;line-height:1.2em;font-weight:bold}.mw-parser-output .sidebar-top-image{padding:0.4em}.mw-parser-output .sidebar-top-caption,.mw-parser-output .sidebar-pretitle-with-top-image,.mw-parser-output .sidebar-caption{padding:0.2em 0.4em 0;line-height:1.2em}.mw-parser-output .sidebar-pretitle{padding:0.4em 0.4em 0;line-height:1.2em}.mw-parser-output .sidebar-title,.mw-parser-output .sidebar-title-with-pretitle{padding:0.2em 0.8em;font-size:145%;line-height:1.2em}.mw-parser-output .sidebar-title-with-pretitle{padding:0.1em 0.4em}.mw-parser-output .sidebar-image{padding:0.2em 0.4em 0.4em}.mw-parser-output .sidebar-heading{padding:0.1em 0.4em}.mw-parser-output .sidebar-content{padding:0 0.5em 0.4em}.mw-parser-output .sidebar-content-with-subgroup{padding:0.1em 0.4em 0.2em}.mw-parser-output .sidebar-above,.mw-parser-output .sidebar-below{padding:0.3em 0.8em;font-weight:bold}.mw-parser-output .sidebar-collapse .sidebar-above,.mw-parser-output .sidebar-collapse .sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}.mw-parser-output .sidebar-navbar{text-align:right;font-size:115%;padding:0 0.4em 0.4em}.mw-parser-output .sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} .mw-parser-output .excerpt-hat .mw-editsection-like{font-style:normal} Part of a series on Genetics Key components Chromosome DNA RNA Genome Heredity Nucleotide Mutation Genetic variation Allele Amino acid Outline Index History and topics Introduction History Evolution ( molecular ) Population genetics Mendelian inheritance Quantitative genetics Molecular genetics Research Geneticist DNA sequencing Genetic engineering Genomics ( template ) Medical genetics Branches of genetics Fields Classical Conservation Cytogenetics Ecological Immunogenetics Microbial Molecular Population Quantitative Personalized medicine Personalized medicine Category .mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:\"[ \"}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:\" ]\"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}} v t e Deoxyribonucleic acid ( pronunciation \u24d8 ; [ 1 ] DNA ) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix . The polymer carries genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses . DNA and ribonucleic acid (RNA) are nucleic acids . Alongside proteins , lipids and complex carbohydrates ( polysaccharides ), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life . The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides . [ 2 ] [ 3 ] Each nucleotide is composed of one of four nitrogen-containing nucleobases ( cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose , and a phosphate group . The nucleotides are joined to one another in a chain by covalent bonds (known as the phosphodiester linkage ) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone . The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups, the single-ringed pyrimidines and the double-ringed purines . In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. Both strands of double-stranded DNA store the same biological information . This information is replicated when the two strands separate. The two strands of DNA run in opposite directions to each other and are thus antiparallel . Attached to each sugar is one of four types of nucleobases (or bases ). It is the sequence of these four nucleobases along the backbone that encodes genetic information. RNA strands are created using DNA strands as a template in a process called transcription , where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes uracil (U). [ 4 ] Under the genetic code , these RNA strands specify the sequence of amino acids within proteins in a process called translation . Within eukaryotic cells, DNA is organized into long structures called chromosomes . Before typical cell division , these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. Eukaryotic organisms ( animals , plants , fungi and protists ) store most of their DNA inside the cell nucleus as nuclear DNA , and some in the mitochondria as mitochondrial DNA or in chloroplasts as chloroplast DNA . [ 5 ] In contrast, prokaryotes ( bacteria and archaea ) store their DNA only in the cytoplasm , in circular chromosomes . Within eukaryotic chromosomes, chromatin proteins, such as histones , compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed. .mw-parser-output .toclimit-2 .toclevel-1 ul,.mw-parser-output .toclimit-3 .toclevel-2 ul,.mw-parser-output .toclimit-4 .toclevel-3 ul,.mw-parser-output .toclimit-5 .toclevel-4 ul,.mw-parser-output .toclimit-6 .toclevel-5 ul,.mw-parser-output .toclimit-7 .toclevel-6 ul{display:none} Properties Chemical structure of DNA; hydrogen bonds shown as dotted lines. Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3\u2032 hydroxyl group (\u2014OH) on the other. DNA is a long polymer made from repeating units called nucleotides . [ 6 ] [ 7 ] The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. [ 8 ] In all species it is composed of two helical chains, bound to each other by hydrogen bonds . Both chains are coiled around the same axis, and have the same pitch of 34 \u00e5ngstr\u00f6ms (3.4 nm ) . The pair of chains have a radius of 10 \u00c5 (1.0 nm) . [ 9 ] According to another study, when measured in a different solution, the DNA chain measured 22\u201326 \u00c5 (2.2\u20132.6 nm) wide, and one nucleotide unit measured 3.3 \u00c5 (0.33 nm) long. [ 10 ] The buoyant density of most DNA is 1.7g/cm 3 . [ 11 ] DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. [ 9 ] [ 12 ] These two long strands coil around each other, in the shape of a double helix . The nucleotide contains both a segment of the backbone of the molecule (which holds the chain together) and a nucleobase (which interacts with the other DNA strand in the helix). A nucleobase linked to a sugar is called a nucleoside , and a base linked to a sugar and to one or more phosphate groups is called a nucleotide . A biopolymer comprising multiple linked nucleotides (as in DNA) is called a polynucleotide . [ 13 ] The backbone of the DNA strand is made from alternating phosphate and sugar groups. [ 14 ] The sugar in DNA is 2-deoxyribose , which is a pentose (five- carbon ) sugar. The sugars are joined by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These are known as the 3\u2032-end (three prime end), and 5\u2032-end (five prime end) carbons, the prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a glycosidic bond . [ 12 ] Therefore, any DNA strand normally has one end at which there is a phosphate group attached to the 5\u2032 carbon of a ribose (the 5\u2032 phosphoryl) and another end at which there is a free hydroxyl group attached to the 3\u2032 carbon of a ribose (the 3\u2032 hydroxyl). The orientation of the 3\u2032 and 5\u2032 carbons along the sugar-phosphate backbone confers directionality (sometimes called polarity) to each DNA strand. In a nucleic acid double helix , the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel . The asymmetric ends of DNA strands are said to have a directionality of five prime end (5\u2032 ), and three prime end (3\u2032), with the 5\u2032 end having a terminal phosphate group and the 3\u2032 end a terminal hydroxyl group. One major difference between DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the related pentose sugar ribose in RNA. [ 12 ] A section of DNA. The bases lie horizontally between the two spiraling strands [ 15 ] ( animated version ). The DNA double helix is stabilized primarily by two forces: hydrogen bonds between nucleotides and base-stacking interactions among aromatic nucleobases. [ 16 ] The four bases found in DNA are adenine ( .mw-parser-output .monospaced{font-family:monospace,monospace} A ), cytosine ( C ), guanine ( G ) and thymine ( T ). These four bases are attached to the sugar-phosphate to form the complete nucleotide, as shown for adenosine monophosphate . Adenine pairs with thymine and guanine pairs with cytosine, forming A-T and G-C base pairs . [ 17 ] [ 18 ] Nucleobase classification The nucleobases are classified into two types: the purines , A and G , which are fused five- and six-membered heterocyclic compounds , and the pyrimidines , the six-membered rings C and T . [ 12 ] A fifth pyrimidine nucleobase, uracil ( U ), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. In addition to RNA and DNA, many artificial nucleic acid analogues have been created to study the properties of nucleic acids, or for use in biotechnology. [ 19 ] Non-canonical bases Modified bases occur in DNA. The first of these recognized was 5-methylcytosine , which was found in the genome of Mycobacterium tuberculosis in 1925. [ 20 ] The reason for the presence of these noncanonical bases in bacterial viruses ( bacteriophages ) is to avoid the restriction enzymes present in bacteria. This enzyme system acts at least in part as a molecular immune system protecting bacteria from infection by viruses. [ 21 ] Modifications of the bases cytosine and adenine, the more common and modified DNA bases, play vital roles in the epigenetic control of gene expression in plants and animals. [ 22 ] A number of noncanonical bases are known to occur in DNA. [ 23 ] Most of these are modifications of the canonical bases plus uracil. Modified Adenine N6-carbamoyl-methyladenine N6-methyadenine Modified Guanine 7-Deazaguanine 7-Methylguanine Modified Cytosine N4-Methylcytosine 5-Carboxylcytosine 5-Formylcytosine 5-Glycosylhydroxymethylcytosine 5-Hydroxycytosine 5-Methylcytosine Modified Thymidine \u03b1-Glutamythymidine \u03b1-Putrescinylthymine Uracil and modifications Base J Uracil 5-Dihydroxypentauracil 5-Hydroxymethyldeoxyuracil Others Deoxyarchaeosine 2,6-Diaminopurine (2-Aminoadenine) Grooves DNA major and minor grooves. The latter is a binding site for the Hoechst stain dye 33258. Twin helical strands form the DNA backbone. Another double helix may be found tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a binding site . As the strands are not symmetrically located with respect to each other, the grooves are unequally sized. The major groove is 22 \u00e5ngstr\u00f6ms (2.2 nm) wide, while the minor groove is 12 \u00c5 (1.2 nm) in width. [ 24 ] Due to the larger width of the major groove, the edges of the bases are more accessible in the major groove than in the minor groove. As a result, proteins such as transcription factors that can bind to specific sequences in double-stranded DNA usually make contact with the sides of the bases exposed in the major groove. [ 25 ] This situation varies in unusual conformations of DNA within the cell (see below) , but the major and minor grooves are always named to reflect the differences in width that would be seen if the DNA was twisted back into the ordinary B form . Base pairing Further information: Base pair Top, a GC base pair with three hydrogen bonds . Bottom, an AT base pair with two hydrogen bonds. Non-covalent hydrogen bonds between the pairs are shown as dashed lines. In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called complementary base pairing . Purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across the double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with high GC-content is more stable than DNA with low GC -content. A Hoogsteen base pair (hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. [ 26 ] As hydrogen bonds are not covalent , they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature . [ 27 ] As a result of this base pair complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in organisms. [ 7 ] ssDNA vs. dsDNA Most DNA molecules are actually two polymer strands, bound together in a helical fashion by noncovalent bonds; this double-stranded (dsDNA) structure is maintained largely by the intrastrand base stacking interactions, which are strongest for G,C stacks. The two strands can come apart\u2014a process known as melting\u2014to form two single-stranded DNA (ssDNA) molecules. Melting occurs at high temperatures, low salt and high pH (low pH also melts DNA, but since DNA is unstable due to acid depurination, low pH is rarely used). The stability of the dsDNA form depends not only on the GC -content (% G,C basepairs) but also on sequence (since stacking is sequence specific) and also length (longer molecules are more stable). The stability can be measured in various ways; a common way is the melting temperature (also called T m value), which is the temperature at which 50% of the double-strand molecules are converted to single-strand molecules; melting temperature is dependent on ionic strength and the concentration of DNA. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determines the strength of the association between the two strands of DNA. Long DNA helices with a high GC -content have more strongly interacting strands, while short helices with high AT content have more weakly interacting strands. [ 28 ] In biology, parts of the DNA double helix that need to separate easily, such as the TATAAT Pribnow box in some promoters , tend to have a high AT content, making the strands easier to pull apart. [ 29 ] In the laboratory, the strength of this interaction can be measured by finding the melting temperature T m necessary to break half of the hydrogen bonds. When all the base pairs in a DNA double helix melt, the strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others. [ 30 ] Amount Schematic karyogram of a human. It shows 22 homologous chromosomes , both the female (XX) and male (XY) versions of the sex chromosome (bottom right), as well as the mitochondrial genome (to scale at bottom left). The blue scale to the left of each chromosome pair (and the mitochondrial genome) shows its length in terms of millions of DNA base pairs . Further information: Karyotype In humans, the total female diploid nuclear genome per cell extends for 6.37 Gigabase pairs (Gbp), is 208.23 cm long and weighs 6.51 picograms (pg). [ 31 ] Male values are 6.27 Gbp, 205.00 cm, 6.41 pg. [ 31 ] Each DNA polymer can contain hundreds of millions of nucleotides, such as in chromosome 1 . Chromosome 1 is the largest human chromosome with approximately 220 million base pairs , and would be 85 mm long if straightened. [ 32 ] In eukaryotes , in addition to nuclear DNA , there is also mitochondrial DNA (mtDNA) which encodes certain proteins used by the mitochondria. The mtDNA is usually relatively small in comparison to the nuclear DNA. For example, the human mitochondrial DNA forms closed circular molecules, each of which contains 16,569 [ 33 ] [ 34 ] DNA base pairs, [ 35 ] with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules. [ 35 ] Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500. [ 35 ] However, the amount of mitochondria per cell also varies by cell type, and an egg cell can contain 100,000 mitochondria, corresponding to up to 1,500,000 copies of the mitochondrial genome (constituting up to 90% of the DNA of the cell). [ 36 ] Sense and antisense Further information: Sense (molecular biology) \"Sense and antisense\" redirects here. For the TV episode, see Sense and Antisense (Millennium) . A DNA sequence is called a \"sense\" sequence if it is the same as that of a messenger RNA copy that is translated into protein. [ 37 ] The sequence on the opposite strand is called the \"antisense\" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands can contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear. [ 38 ] One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing. [ 39 ] A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses , blur the distinction between sense and antisense strands by having overlapping genes . [ 40 ] In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. In bacteria , this overlap may be involved in the regulation of gene transcription, [ 41 ] while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome. [ 42 ] Supercoiling Further information: DNA supercoil DNA can be twisted like a rope in a process called DNA supercoiling . With DNA in its \"relaxed\" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound. [ 43 ] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that is introduced by enzymes called topoisomerases . [ 44 ] These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as transcription and DNA replication . [ 45 ] Alternative DNA structures Further information: Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid , Molecular models of DNA , and DNA structure From left to right, the structures of A , B and Z-DNA DNA exists in many possible conformations that include A-DNA , B-DNA , and Z-DNA forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. [ 14 ] The conformation that DNA adopts depends on the hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal ions , and the presence of polyamines in solution. [ 46 ] The first published reports of A-DNA X-ray diffraction patterns\u2014and also B-DNA\u2014used analyses based on Patterson functions that provided only a limited amount of structural information for oriented fibers of DNA. [ 47 ] [ 48 ] An alternative analysis was proposed by Wilkins et al. in 1953 for the in vivo B-DNA X-ray diffraction-scattering patterns of highly hydrated DNA fibers in terms of squares of Bessel functions . [ 49 ] In the same journal, James Watson and Francis Crick presented their molecular modeling analysis of the DNA X-ray diffraction patterns to suggest that the structure was a double helix. [ 9 ] Although the B-DNA form is most common under the conditions found in cells, [ 50 ] it is not a well-defined conformation but a family of related DNA conformations [ 51 ] that occur at the high hydration levels present in cells. Their corresponding X-ray diffraction and scattering patterns are characteristic of molecular paracrystals with a significant degree of disorder. [ 52 ] [ 53 ] Compared to B-DNA, the A-DNA form is a wider right-handed spiral, with a shallow, wide minor groove and a narrower, deeper major groove. The A form occurs under non-physiological conditions in partly dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, and in enzyme-DNA complexes. [ 54 ] [ 55 ] Segments of DNA where the bases have been chemically modified by methylation may undergo a larger change in conformation and adopt the Z form . Here, the strands turn about the helical axis in a left-handed spiral, the opposite of the more common B form. [ 56 ] These unusual structures can be recognized by specific Z-DNA binding proteins and may be involved in the regulation of transcription. [ 57 ] Alternative DNA chemistry Further information: hypothetical types of biochemistry For many years, exobiologists have proposed the existence of a shadow biosphere , a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. One of the proposals was the existence of lifeforms that use arsenic instead of phosphorus in DNA . A report in 2010 of the possibility in the bacterium GFAJ-1 was announced, [ 58 ] [ 59 ] though the research was disputed, [ 59 ] [ 60 ] and evidence suggests the bacterium actively prevents the incorporation of arsenic into the DNA backbone and other biomolecules. [ 61 ] Quadruplex structures Further information: G-quadruplex DNA quadruplex formed by telomere repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix. The green spheres in the center represent potassium ions. [ 62 ] At the ends of the linear chromosomes are specialized regions of DNA called telomeres . The main function of these regions is to allow the cell to replicate chromosome ends using the enzyme telomerase , as the enzymes that normally replicate DNA cannot copy the extreme 3\u2032 ends of chromosomes. [ 63 ] These specialized chromosome caps also help protect the DNA ends, and stop the DNA repair systems in the cell from treating them as damage to be corrected. [ 64 ] In human cells , telomeres are usually lengths of single-stranded DNA containing several thousand repeats of a simple TTAGGG sequence. [ 65 ] These guanine-rich sequences may stabilize chromosome ends by forming structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases, known as a guanine tetrad , form a flat plate. These flat four-base units then stack on top of each other to form a stable G-quadruplex structure. [ 66 ] These structures are stabilized by hydrogen bonding between the edges of the bases and chelation of a metal ion in the centre of each four-base unit. [ 67 ] Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here, the single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins. [ 68 ] At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This triple-stranded structure is called a displacement loop or D-loop . [ 66 ] Branched DNA Further information: Branched DNA and DNA nanotechnology Single branch Multiple branches Branched DNA can form networks containing multiple branches. In DNA, fraying occurs when non-complementary regions exist at the end of an otherwise complementary double-strand of DNA. However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible. [ 69 ] Branched DNA can be used in nanotechnology to construct geometric shapes, see the section on uses in technology below. Artificial bases Main article: Nucleic acid analogue Several artificial nucleobases have been synthesized, and successfully incorporated in the eight-base DNA analogue named Hachimoji DNA . Dubbed S, B, P, and Z, these artificial bases are capable of bonding with each other in a predictable way (S\u2013B and P\u2013Z), maintain the double helix structure of DNA, and be transcribed to RNA. Their existence could be seen as an indication that there is nothing special about the four natural nucleobases that evolved on Earth. [ 70 ] [ 71 ] On the other hand, DNA is tightly related to RNA which does not only act as a transcript of DNA but also performs as molecular machines many tasks in cells. For this purpose it has to fold into a structure. It has been shown that to allow to create all possible structures at least four bases are required for the corresponding RNA , [ 72 ] while a higher number is also possible but this would be against the natural principle of least effort . Acidity The phosphate groups of DNA give it similar acidic properties to phosphoric acid and it can be considered as a strong acid . It will be fully ionized at a normal cellular pH, releasing protons which leave behind negative charges on the phosphate groups. These negative charges protect DNA from breakdown by hydrolysis by repelling nucleophiles which could hydrolyze it. [ 73 ] Macroscopic appearance Impure DNA extracted from an orange Pure DNA extracted from cells forms white, stringy clumps. [ 74 ] Chemical modifications and altered DNA packaging Base modifications and DNA packaging Further information: DNA methylation and Chromatin remodeling cytosine 5-methylcytosine thymine Structure of cytosine with and without the 5-methyl group. Deamination converts 5-methylcytosine into thymine. The expression of genes is influenced by how the DNA is packaged in chromosomes, in a structure called chromatin . Base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of methylation of cytosine bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the histone protein core around which DNA is wrapped in the chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see Chromatin remodeling ). There is, further, crosstalk between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression. [ 75 ] For one example, cytosine methylation produces 5-methylcytosine , which is important for X-inactivation of chromosomes. [ 76 ] The average level of methylation varies between organisms\u2014the worm Caenorhabditis elegans lacks cytosine methylation, while vertebrates have higher levels, with up to 1% of their DNA containing 5-methylcytosine. [ 77 ] Despite the importance of 5-methylcytosine, it can deaminate to leave a thymine base, so methylated cytosines are particularly prone to mutations . [ 78 ] Other base modifications include adenine methylation in bacteria, the presence of 5-hydroxymethylcytosine in the brain , [ 79 ] and the glycosylation of uracil to produce the \"J-base\" in kinetoplastids . [ 80 ] [ 81 ] Damage Further information: DNA damage (naturally occurring) , Mutation , and DNA damage theory of aging A covalent adduct between a metabolically activated form of benzo[ a ]pyrene , the major mutagen in tobacco smoke , and DNA [ 82 ] DNA can be damaged by many sorts of mutagens , which change the DNA sequence . Mutagens include oxidizing agents , alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and X-rays . The type of DNA damage produced depends on the type of mutagen. For example, UV light can damage DNA by producing thymine dimers", "Climate change Human-caused changes to climate on Earth .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} This article is about the human-induced rise in global temperatures. For natural historical climate trends, see Climate variability and change . \"Global warming\" redirects here. For other uses, see Climate change (disambiguation) and Global warming (disambiguation) . <a href=\\\"./Wikipedia:Featured_articles*\\\" title=\\\"This is a featured article. Click here for more information.\\\" id=\\\"mwCg\\\"><img alt=\\\"Featured article\\\" resource=\\\"./File:Cscr-featured.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/20px-Cscr-featured.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"466\\\" data-file-height=\\\"443\\\" data-file-type=\\\"drawing\\\" height=\\\"19\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/e/e7/Cscr-featured.svg/40px-Cscr-featured.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwCw\\\"/></a></span>\\n\"}' id=\"mwDA\"/> <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwEQ\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwEg\\\"/></a></span>\"}' id=\"mwEw\"/> {{Cite web |title=GISS Surface Temperature Analysis (v4) |url=https://data.giss.nasa.gov/gistemp/maps/ |access-date=12 January 2024 |website=NASA}}</ref> The [[Arctic]] has warmed the most, and temperatures on land have generally increased more than [[sea surface temperature]]s.\"},\"image2\":{\"wt\":\"Global Temperature And Forces With Fahrenheit.svg\"},\"alt2\":{\"wt\":\"Timeseries of global warming from 1880 to 2020 compared to simulated temperatures given only natural forcing. The first shows a positive trend since around 1950 and the second stays relatively flat.\"},\"caption2\":{\"wt\":\"Earth's average surface air temperature has increased almost 1.5{{nbsp}}\u00b0C (about{{nbsp}}2.5 \u00b0F) since the [[Industrial Revolution]]. Natural forces cause some variability, but the 20-year average shows the progressive influence of human activity.<ref>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|loc=SPM-7}}</ref>\"}},\"i\":0}}]}' id=\"mwGg\">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}} Changes in surface air temperature over the past 50 years. [ 1 ] The Arctic has warmed the most, and temperatures on land have generally increased more than sea surface temperatures . Earth's average surface air temperature has increased almost 1.5 \u00b0C (about 2.5 \u00b0F) since the Industrial Revolution . Natural forces cause some variability, but the 20-year average shows the progressive influence of human activity. [ 2 ] Present-day climate change includes both global warming \u2014the ongoing increase in global average temperature \u2014and its wider effects on Earth's climate system . Climate change in a broader sense also includes previous long-term changes to Earth's climate . The modern-day rise in global temperatures is driven by human activities , especially fossil fuel ( coal , oil and natural gas ) burning since the Industrial Revolution . [ 3 ] [ 4 ] Fossil fuel use, deforestation , and some agricultural and industrial practices release greenhouse gases . [ 5 ] These gases absorb some of the heat that the Earth radiates after it warms from sunlight, warming the lower atmosphere. Earth's atmosphere now has roughly 50% more carbon dioxide , the main gas driving global warming, than it did at the end of the pre-industrial era , reaching levels not seen for millions of years. [ 6 ] Climate change has an increasingly large impact on the environment . Deserts are expanding , while heat waves and wildfires are becoming more common. [ 7 ] Amplified warming in the Arctic has contributed to thawing permafrost , retreat of glaciers and sea ice decline . [ 8 ] Higher temperatures are also causing more intense storms , droughts , and other weather extremes . [ 9 ] Rapid environmental change in mountains , coral reefs , and the Arctic is forcing many species to relocate or become extinct . [ 10 ] Even if efforts to minimize future warming are successful, some effects will continue for centuries. These include ocean heating , ocean acidification and sea level rise . [ 11 ] Climate change threatens people with increased flooding, extreme heat, increased food and water scarcity, more disease, and economic loss . [ 12 ] Human migration and conflict can also be a result. [ 13 ] The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. [ 14 ] Societies and ecosystems will experience more severe risks without action to limit warming . [ 15 ] Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached. [ 16 ] Poorer communities are responsible for a small share of global emissions , yet have the least ability to adapt and are most vulnerable to climate change . [ 17 ] [ 18 ] {{cite web |url=https://www.cbsnews.com/news/water-cutbacks-california-6-million-people-drought/ |title=California is rationing water amid its worst drought in 1,200 years |first=Irina |last=Ivanova |publisher=[[CBS News]] |date=June 2, 2022}}</ref>\"},\"footer\":{\"wt\":\"Examples of some [[effects of climate change]]: [[Wildfire]] intensified by heat and drought, [[Coral bleaching|bleaching of corals]] occurring more often due to [[marine heatwave]]s, and worsening droughts compromising water supplies.\"}},\"i\":0}}]}' id=\"mwmg\"/> <a href=\\\"./Climate_change#cite_note-19\\\" id=\\\"mwnQ\\\"><span class=\\\"mw-reflink-text\\\" id=\\\"mwng\\\"><span class=\\\"cite-bracket\\\" id=\\\"mwnw\\\">[</span>19<span class=\\\"cite-bracket\\\" id=\\\"mwoA\\\">]</span></span></a></sup>\",\"txt\":\"A dry lakebed in California, which is experiencing its worst megadrought in 1,200 years..mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:\\\"\\\\\\\"\\\"\\\"\\\\\\\"\\\"\\\"'\\\"\\\"'\\\"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url(\\\"//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg\\\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url(\\\"//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg\\\")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url(\\\"//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg\\\")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url(\\\"//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg\\\")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#bf3c2c)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}Ivanova, Irina (2 June 2022). \\\"California is rationing water amid its worst drought in 1,200 years\\\". CBS News.\"}]]}'> Examples of some effects of climate change : Wildfire intensified by heat and drought, bleaching of corals occurring more often due to marine heatwaves , and worsening droughts compromising water supplies. Many climate change impacts have been observed in the first decades of the 21st century, with 2024 the warmest on record at + 1.60 \u00b0C (2.88 \u00b0F) since regular tracking began in 1850. [ 20 ] [ 21 ] Additional warming will increase these impacts and can trigger tipping points , such as melting all of the Greenland ice sheet . [ 22 ] Under the 2015 Paris Agreement , nations collectively agreed to keep warming \"well under 2 \u00b0C\". However, with pledges made under the Agreement, global warming would still reach about 2.8 \u00b0C (5.0 \u00b0F) by the end of the century. [ 23 ] There is widespread support for climate action worldwide, [ 24 ] [ 25 ] and most countries aim to stop emitting carbon dioxide . [ 26 ] Fossil fuels can be phased out by stopping subsidising them , conserving energy and switching to energy sources that do not produce significant carbon pollution . These energy sources include wind , solar , hydro , and nuclear power . [ 27 ] Cleanly generated electricity can replace fossil fuels for powering transportation , heating buildings , and running industrial processes. [ 28 ] Carbon can also be removed from the atmosphere , for instance by increasing forest cover and farming with methods that store carbon in soil . [ 29 ] [ 30 ] [ 31 ] .mw-parser-output .toclimit-2 .toclevel-1 ul,.mw-parser-output .toclimit-3 .toclevel-2 ul,.mw-parser-output .toclimit-4 .toclevel-3 ul,.mw-parser-output .toclimit-5 .toclevel-4 ul,.mw-parser-output .toclimit-6 .toclevel-5 ul,.mw-parser-output .toclimit-7 .toclevel-6 ul{display:none} Terminology Before the 1980s, it was unclear whether the warming effect of increased greenhouse gases was stronger than the cooling effect of airborne particulates in air pollution. Scientists used the term inadvertent climate modification to refer to human impacts on the climate at this time. [ 32 ] In the 1980s, the terms global warming and climate change became more common, often being used interchangeably. [ 33 ] [ 34 ] [ 35 ] Scientifically, global warming refers only to increased global average surface temperature, while climate change describes both global warming and its effects on Earth's climate system , such as precipitation changes. [ 32 ] Climate change can also be used more broadly to include changes to the climate that have happened throughout Earth's history as result of natural processes. [ 36 ] The term anthropogenic climate change is sometimes used to describe climate change resulting from human activities. [ 37 ] Global warming \u2014used as early as 1975 [ 38 ] \u2014became the more popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate . [ 39 ] Since the 2000s, usage of climate change has increased. [ 40 ] Various scientists, politicians and media may use the terms climate crisis or climate emergency to talk about climate change, and may use the term global heating instead of global warming . [ 41 ] [ 42 ] Global temperature rise Further information: Global surface temperature Temperatures prior to present-day global warming Main articles: Climate variability and change ; Temperature record of the last 2,000 years ; and Paleoclimatology Global surface temperature reconstruction over the past 2000 years using proxy data from tree rings, corals, and ice cores in blue. [ 43 ] Directly observed data is in red. [ 44 ] Over the last few million years the climate cycled through ice ages . One of the hotter periods was the Last Interglacial , around 125,000 years ago, where temperatures were between 0.5 \u00b0C and 1.5 \u00b0C warmer than before the start of global warming. [ 45 ] This period saw sea levels 5 to 10 metres higher than today. The most recent glacial maximum 20,000 years ago was some 5\u20137 \u00b0C colder. This period has sea levels that were over 125 metres (410 ft) lower than today. [ 46 ] Temperatures stabilized in the current interglacial period beginning 11,700 years ago . [ 47 ] This period also saw the start of agriculture. [ 48 ] Historical patterns of warming and cooling, like the Medieval Warm Period and the Little Ice Age , did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions. [ 49 ] [ 50 ] Climate information for that period comes from climate proxies , such as trees and ice cores . [ 51 ] [ 52 ] Warming since the Industrial Revolution In recent decades, new high temperature records have substantially outpaced new low temperature records on a growing portion of Earth's surface. [ 53 ] There has been an increase in ocean heat content during recent decades as the oceans absorb over 90% of the heat from global warming . [ 54 ] Around 1850 thermometer records began to provide global coverage. [ 55 ] Between the 18th century and 1970 there was little net warming, as the warming impact of greenhouse gas emissions was offset by cooling from sulfur dioxide emissions. Sulfur dioxide causes acid rain , but it also produces sulfate aerosols in the atmosphere, which reflect sunlight and cause global dimming . After 1970, the increasing accumulation of greenhouse gases and controls on sulfur pollution led to a marked increase in temperature. [ 56 ] [ 57 ] [ 58 ] NASA animation portraying global surface temperature changes since 1880. The colour blue denotes cooler temperatures and red denotes warmer temperatures. As reference value the mean temperature from 1951 to 1980 is used. Ongoing changes in climate have had no precedent for several thousand years. [ 59 ] Multiple datasets all show worldwide increases in surface temperature, [ 60 ] at a rate of around 0.2 \u00b0C per decade. [ 61 ] The 2014\u20132023 decade warmed to an average 1.19 \u00b0C [1.06\u20131.30 \u00b0C] compared to the pre-industrial baseline (1850\u20131900). [ 62 ] Not every single year was warmer than the last: internal climate variability processes can make any year 0.2 \u00b0C warmer or colder than the average. [ 63 ] From 1998 to 2013, negative phases of two such processes, Pacific Decadal Oscillation (PDO) [ 64 ] and Atlantic Multidecadal Oscillation (AMO) [ 65 ] caused a short slower period of warming called the \" global warming hiatus \". [ 66 ] After the \"hiatus\", the opposite occurred, with 2024 well above the recent average at more than +1.5 \u00b0C. [ 67 ] This is why the temperature change is defined in terms of a 20-year average, which reduces the noise of hot and cold years and decadal climate patterns, and detects the long-term signal. [ 68 ] : 5 [ 69 ] A wide range of other observations reinforce the evidence of warming. [ 70 ] [ 71 ] The upper atmosphere is cooling, because greenhouse gases are trapping heat near the Earth's surface, and so less heat is radiating into space. [ 72 ] Warming reduces average snow cover and forces the retreat of glaciers . At the same time, warming also causes greater evaporation from the oceans , leading to more atmospheric humidity , more and heavier precipitation . [ 73 ] [ 74 ] Plants are flowering earlier in spring, and thousands of animal species have been permanently moving to cooler areas. [ 75 ] Differences by region Different regions of the world warm at different rates . The pattern is independent of where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet. Since the pre-industrial period, the average surface temperature over land regions has increased almost twice as fast as the global average surface temperature. [ 76 ] This is because oceans lose more heat by evaporation and oceans can store a lot of heat . [ 77 ] The thermal energy in the global climate system has grown with only brief pauses since at least 1970, and over 90% of this extra energy has been stored in the ocean . [ 78 ] [ 79 ] The rest has heated the atmosphere , melted ice, and warmed the continents. [ 80 ] The Northern Hemisphere and the North Pole have warmed much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, but also more seasonal snow cover and sea ice . As these surfaces flip from reflecting a lot of light to being dark after the ice has melted, they start absorbing more heat . [ 81 ] Local black carbon deposits on snow and ice also contribute to Arctic warming. [ 82 ] Arctic surface temperatures are increasing between three and four times faster than in the rest of the world. [ 83 ] [ 84 ] Melting of ice sheets near the poles weakens both the Atlantic and the Antarctic limb of thermohaline circulation , which further changes the distribution of heat and precipitation around the globe. [ 85 ] [ 86 ] [ 87 ] [ 88 ] Future global temperatures CMIP6 multi-model projections of global surface temperature changes for the year 2090 relative to the 1850\u20131900 average. The current trajectory for warming by the end of the century is roughly halfway between these two extremes. [ 23 ] [ 89 ] [ 90 ] The World Meteorological Organization estimates there is almost a 50% chance of the five-year average global temperature exceeding +1.5 \u00b0C between 2024 and 2028. [ 91 ] The IPCC expects the 20-year average to exceed +1.5 \u00b0C in the early 2030s. [ 92 ] The IPCC Sixth Assessment Report (2021) included projections that by 2100 global warming is very likely to reach 1.0\u20131.8 \u00b0C under a scenario with very low emissions of greenhouse gases , 2.1\u20133.5 \u00b0C under an intermediate emissions scenario , or 3.3\u20135.7 \u00b0C under a very high emissions scenario . [ 93 ] The warming will continue past 2100 in the intermediate and high emission scenarios, [ 94 ] [ 95 ] with future projections of global surface temperatures by year 2300 being similar to millions of years ago. [ 96 ] The remaining carbon budget for staying beneath certain temperature increases is determined by modelling the carbon cycle and climate sensitivity to greenhouse gases. [ 97 ] According to UNEP , global warming can be kept below 2.0 \u00b0C with a 50% chance if emissions after 2023 do not exceed 900 gigatonnes of CO 2 . This carbon budget corresponds to around 16 years of current emissions. [ 98 ] Causes of recent global temperature rise Main article: Causes of climate change Physical drivers of global warming that has happened so far. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. Whiskers on each bar show the possible error range . The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, El Ni\u00f1o events cause short-term spikes in surface temperature while La Ni\u00f1a events cause short term cooling. [ 99 ] Their relative frequency can affect global temperature trends on a decadal timescale. [ 100 ] Other changes are caused by an imbalance of energy from external forcings . [ 101 ] Examples of these include changes in the concentrations of greenhouse gases , solar luminosity , volcanic eruptions, and variations in the Earth's orbit around the Sun. [ 102 ] To determine the human contribution to climate change, unique \"fingerprints\" for all potential causes are developed and compared with both observed patterns and known internal climate variability . [ 103 ] For example, solar forcing\u2014whose fingerprint involves warming the entire atmosphere\u2014is ruled out because only the lower atmosphere has warmed. [ 104 ] Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in albedo , are less impactful. [ 105 ] Greenhouse gases Main articles: Greenhouse gas , Greenhouse gas emissions , Greenhouse effect , and Carbon dioxide in Earth's atmosphere CO 2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black) Greenhouse gases are transparent to sunlight , and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat , and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time. [ 106 ] While water vapour (\u224850%) and clouds (\u224825%) are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature and are therefore mostly considered to be feedbacks that change climate sensitivity . On the other hand, concentrations of gases such as CO 2 (\u224820%), tropospheric ozone , [ 107 ] CFCs and nitrous oxide are added or removed independently from temperature, and are therefore considered to be external forcings that change global temperatures. [ 108 ] Before the Industrial Revolution, naturally occurring amounts of greenhouse gases caused the air near the surface to be about 33 \u00b0C warmer than it would have been in their absence. [ 109 ] [ 110 ] Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels (coal, oil , and natural gas), [ 111 ] has increased the amount of greenhouse gases in the atmosphere. In 2022, the concentrations of CO 2 and methane had increased by about 50% and 164%, respectively, since 1750. [ 112 ] These CO 2 levels are higher than they have been at any time during the last 14 million years. [ 113 ] Concentrations of methane are far higher than they were over the last 800,000 years. [ 114 ] The Global Carbon Project shows how additions to CO 2 since 1880 have been caused by different sources ramping up one after another. Global human-caused greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of CO 2 . Of these emissions, 75% was CO 2 , 18% was methane , 4% was nitrous oxide, and 2% was fluorinated gases . [ 115 ] CO 2 emissions primarily come from burning fossil fuels to provide energy for transport, manufacturing, heating , and electricity. [ 5 ] Additional CO 2 emissions come from deforestation and industrial processes , which include the CO 2 released by the chemical reactions for making cement , steel , aluminium , and fertilizer . [ 116 ] [ 117 ] [ 118 ] [ 119 ] Methane emissions come from livestock , manure, rice cultivation , landfills, wastewater, and coal mining , as well as oil and gas extraction . [ 120 ] [ 121 ] Nitrous oxide emissions largely come from the microbial decomposition of fertilizer . [ 122 ] [ 123 ] While methane only lasts in the atmosphere for an average of 12 years, [ 124 ] CO 2 lasts much longer. The Earth's surface absorbs CO 2 as part of the carbon cycle . While plants on land and in the ocean absorb most excess emissions of CO 2 every year, that CO 2 is returned to the atmosphere when biological matter is digested, burns, or decays. [ 125 ] Land-surface carbon sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global CO 2 emissions. [ 126 ] The ocean has absorbed 20 to 30% of emitted CO 2 over the last two decades. [ 127 ] CO 2 is only removed from the atmosphere for the long term when it is stored in the Earth's crust, which is a process that can take millions of years to complete. [ 125 ] Land surface changes The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy. [ 128 ] Around 30% of Earth's land area is largely unusable for humans ( glaciers , deserts , etc.), 26% is forests, 10% is shrubland and 34% is agricultural land . [ 129 ] Deforestation is the main land use change contributor to global warming, [ 130 ] as the destroyed trees release CO 2 , and are not replaced by new trees, removing that carbon sink . [ 131 ] Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable agricultural expansion for crops and livestock. Another 24% has been lost to temporary clearing under the shifting cultivation agricultural systems. 26% was due to logging for wood and derived products, and wildfires have accounted for the remaining 23%. [ 132 ] Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink. [ 133 ] Local vegetation cover impacts how much of the sunlight gets reflected back into space ( albedo ), and how much heat is lost by evaporation . For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify the release of chemical compounds that influence clouds, and by changing wind patterns. [ 134 ] In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler. [ 133 ] At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains. [ 134 ] Globally, these increases in surface albedo have been the dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect. [ 135 ] Other factors Aerosols and clouds Air pollution, in the form of aerosols, affects the climate on a large scale. [ 136 ] Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed. This phenomenon is popularly known as global dimming , [ 137 ] and is primarily attributed to sulfate aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like coal and bunker fuel . [ 58 ] Smaller contributions come from black carbon (from combustion of fossil fuels and biomass ), and from dust. [ 138 ] [ 139 ] [ 140 ] Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much. [ 141 ] [ 58 ] Aerosols also have indirect effects on the Earth's energy budget . Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets. [ 142 ] They also reduce the growth of raindrops , which makes clouds more reflective to incoming sunlight. [ 143 ] Indirect effects of aerosols are the largest uncertainty in radiative forcing . [ 144 ] While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise. [ 145 ] Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 \u00b0C by 2050. [ 146 ] The effect of decreasing sulfur content of fuel oil for ships since 2020 [ 147 ] is estimated to cause an additional 0.05 \u00b0C increase in global mean temperature by 2050. [ 148 ] Solar and volcanic activity Further information: Solar activity and climate The Fourth National Climate Assessment (\"NCA4\", USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming. [ 149 ] [ 150 ] As the Sun is the Earth's primary energy source, changes in incoming sunlight directly affect the climate system . [ 144 ] Solar irradiance has been measured directly by satellites , [ 151 ] and indirect measurements are available from the early 1600s onwards. [ 144 ] Since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth, in contrast to the warming of the lower atmosphere (the troposphere ). [ 152 ] The upper atmosphere (the stratosphere ) would also be warming if the Sun was sending more energy to Earth, but instead, it has been cooling. [ 104 ] This is consistent with greenhouse gases preventing heat from leaving the Earth's atmosphere. [ 153 ] Explosive volcanic eruptions can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapour into the atmosphere, which adds to greenhouse gases and increases temperatures. [ 154 ] These impacts on temperature only last for several years, because both water vapour and volcanic material have low persistence in the atmosphere. [ 155 ] volcanic CO 2 emissions are more persistent, but they are equivalent to less than 1% of current human-caused CO 2 emissions. [ 156 ] Volcanic activity still represents the single largest natural impact (forcing) on temperature in the industrial era. Yet, like the other natural forcings, it has had negligible impacts on global temperature trends since the Industrial Revolution. [ 155 ] Climate change feedbacks Main articles: Climate change feedbacks and Climate sensitivity Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process . [ 157 ] The climate system's response to an initial forcing is shaped by feedbacks, which either amplify or dampen the change. Self-reinforcing or positive feedbacks increase the response, while balancing or negative feedbacks reduce it. [ 158 ] The main reinforcing feedbacks are the water-vapour feedback , the ice\u2013albedo feedback , and the net cloud feedback . [ 159 ] [ 160 ] The primary balancing mechanism is radiative cooling , as Earth's surface gives off more heat to space in response to rising temperature. [ 161 ] In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of CO 2 on plant growth. [ 162 ] Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity. [ 163 ] These feedback processes alter the pace of global warming. For instance, warmer air can hold more moisture in the form of water vapour , which is itself a potent greenhouse gas. [ 159 ] Warmer air can also make clouds higher and thinner, and therefore more insulating, increasing climate warming. [ 164 ] The reduction of snow cover and sea ice in the Arctic is another major feedback, this reduces the reflectivity of the Earth's surface in the region and accelerates Arctic warming . [ 165 ] [ 166 ] This additional warming also contributes to permafrost thawing, which releases methane and CO 2 into the atmosphere. [ 167 ] Around half of human-caused CO 2 emissions have been absorbed by land plants and by the oceans. [ 168 ] This fraction is not static and if future CO 2 emissions decrease, the Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%. [ 169 ] This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer . [ 170 ] [ 171 ] The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution. [ 172 ] [ 173 ] [ 86 ] Uncertainty over feedbacks, particularly cloud cover, [ 174 ] is the major reason why different climate models project different magnitudes of warming for a given amount of emissions. [ 175 ] Modelling Further information: Climate model and Climate change scenario Energy flows between space, the atmosphere, and Earth's surface. Most sunlight passes through the atmosphere to heat the Earth's surface, then greenhouse gases absorb most of the heat the Earth radiates in response. Adding to greenhouse gases increases this insulating effect, causing an energy imbalance that heats the planet up. A climate model is a representation of the physical, chemical and biological processes that affect the climate system. [ 176 ] Models include", "American Civil War 1861\u20131865 conflict in the United States <a href=\\\"./Wikipedia:Protection_policy#semi\\\" title=\\\"This article is semi-protected.\\\" id=\\\"mwBg\\\"><img alt=\\\"Page semi-protected\\\" resource=\\\"./File:Semi-protection-shackle.svg\\\" src=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/20px-Semi-protection-shackle.svg.png\\\" decoding=\\\"async\\\" data-file-width=\\\"512\\\" data-file-height=\\\"512\\\" data-file-type=\\\"drawing\\\" height=\\\"20\\\" width=\\\"20\\\" srcset=\\\"//upload.wikimedia.org/wikipedia/en/thumb/1/1b/Semi-protection-shackle.svg/40px-Semi-protection-shackle.svg.png 2x\\\" class=\\\"mw-file-element\\\" id=\\\"mwBw\\\"/></a></span>\"}' id=\"mwCA\"/> [A]nd on May 26 he [E. Kirby Smith] surrendered and the war was over.\\\" | {{harvnb|Gallagher |Engle |Krick |Glatthaar|2003|p=308}}. \\\"By 26 May, General Edward Kirby Smith had surrendered the Rebel forces in the trans-Mississippi west. The war was over.\\\" | {{harvnb|Blair|2015|p=9}}. \\\"The sheer weight of scholarship has leaned toward portraying the surrenders of the Confederate armies as the end of the war.\\\"}}}}{{efn|name=End2|Among the many other contemporary sources and later historians citing May 26, 1865, as the end date for the American Civil War hostilities are [[George Templeton Strong]], who was a prominent New York lawyer; a founder, treasurer, and member of the Executive Committee of United States Sanitary Commission throughout the war; and a diarist. A diary excerpt is published in Gienapp, William E. (ed.). ''The Civil War and Reconstruction: A Documentary Collection.'' New York: W.W. Norton & Co., 2001, pp. 313\u2013314 {{ISBN|978-0-393-97555-0}}. A footnote in Gienapp shows the excerpt was taken from an edited version of the diaries by Allan Nevins and Milton Halsey Thomas, eds., ''The Diary of George Templeton Strong'', vol. 2 (New York: The Macmillan Company), pp. 600\u2013601, which differs from the volume and page numbers of the original diaries; the page in Strong's original handwriting is shown at {{Cite web |title=Volume 4, pages 124\u2013125: diary entries for May 23 (continued)\u2013June 7, 1865. |url=https://digitalcollections.nyhistory.org/islandora/object/nyhs%3A55249 |url-status=live |archive-url=https://web.archive.org/web/20221116151714/https://digitalcollections.nyhistory.org/islandora/object/nyhs%3A55249 |archive-date=November 16, 2022 |via=New-York Historical Society Museum & Library}}}} {{nwr|({{Age in years, months, weeks and days|month1=04|day1=12|year1=1861|month2=05|day2=26|year2=1865}})}}\"},\"place\":{\"wt\":\"[[United States]], [[Atlantic Ocean]]\"},\"result\":{\"wt\":\"[[Union (American Civil War)|Union]] victory\"},\"territory\":{\"wt\":\"Dissolution of the [[Confederate States of America]]\"},\"combatant1\":{\"wt\":\"{{flagicon|United States|1861}} [[Union (American Civil War)|United States]]\"},\"combatant2\":{\"wt\":\"{{flagcountry|Confederate States of America|1861}}\"},\"commander1\":{\"wt\":\"{{plainlist|\\n* {{flagicon|United States|1861}} [[Abraham Lincoln]]{{Assassinated|Assassination of Abraham Lincoln}}\\n* {{flagicon|United States|1861}} [[Ulysses S. Grant]]\\n* ''[[Military leadership in the American Civil War#The United States (The Union)|and others...]]''\\n}}\"},\"commander2\":{\"wt\":\"{{plainlist|\\n* {{flagicon|Confederate States of America|1861}} [[Jefferson Davis]]{{Surrender}}{{POW}}\\n* {{flagicon|Confederate States of America|1861}} [[Robert E. Lee]]{{Surrender}}\\n* ''[[Military leadership in the American Civil War#The Confederate States (The Confederacy)|and others...]]''\\n}}\"},\"strength1\":{\"wt\":\"{{indented plainlist|\\n* 698,000 at peak<ref>{{Cite web |title=Size of the Union Army in the American Civil War |url=http://www.oocities.org/littlegreenmen.geo/UASize.htm |url-status=live |archive-url=https://web.archive.org/web/20160130034407/http://www.oocities.org/littlegreenmen.geo/UASize.htm |archive-date=January 30, 2016 |quote=Of which 131,000 were in the Navy and Marines, 140,000 were garrison troops and home defense militia, and 427,000 were in the field army}}</ref>\\n* 2,200,000 total<ref name=\\\"NationalParkService\\\">{{Cite web |title=Facts |url=https://www.nps.gov/civilwar/facts.htm |publisher=National Park Service |access-date=June 3, 2025 |archive-date=April 4, 2019 |archive-url=https://web.archive.org/web/20190404044248/https://www.nps.gov/civilwar/facts.htm |url-status=live }}</ref>\\n}}\"},\"strength2\":{\"wt\":\"{{indented plainlist|\\n* 360,000 at peak<ref name=\\\"NationalParkService\\\" /><ref>{{Cite web |year=1900 |title=The war of the rebellion: a compilation of the official records of the Union and Confederate armies; Series 4 \u2013 Volume 2 |url=https://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=abstract;rgn=full%20text;idno=waro0128;didno=waro0128;view=image;seq=0542 |archive-url=https://web.archive.org/web/20170725221244/http://ebooks.library.cornell.edu/cgi/t/text/pageviewer-idx?c=moawar;cc=moawar;q1=abstract;rgn=full%20text;idno=waro0128;didno=waro0128;view=image;seq=0542 |archive-date=July 25, 2017 |publisher=United States War Dept.}}</ref>\\n* 750,000\u20131,000,000 total{{sfn|Long|1971|p=705}}\\n}}\"},\"casualties1\":{\"wt\":\"{{indented plainlist|\\n* 110,000+ [[Killed in action|{{abbr|KIA|killed in action}} or {{abbr|DOW|died of wounds}}]]\\n* 230,000+ died from accidents or disease<ref name=\\\"Fox1889\\\">{{Cite book |last=Fox |first=William F. |url=http://www.civilwarhome.com/foxspref.html |title=Regimental losses in the American Civil War |year=1889 |archive-url=https://web.archive.org/web/20170525214736/http://www.civilwarhome.com/foxspref.html |archive-date=May 25, 2017 |url-status=usurped}}</ref><ref name=\\\"DCAS\\\">{{Cite web |title=US Military Casualties: Principal Wars 1775\u20131991 |url=https://dcas.dmdc.osd.mil/dcas/app/summaryData/casualties/principalWars |website=Defence Casuality Analysis System (DCAS) |access-date=August 2, 2022 |archive-date=October 20, 2022 |archive-url=https://web.archive.org/web/20221020072530/https://dcas.dmdc.osd.mil/dcas/app/summaryData/casualties/principalWars |url-status=live }}</ref>\\n* 25,000\u201330,000 died in Confederate prisons<ref name=\\\"NationalParkService\\\" /><ref name=\\\"Fox1889\\\" />\\n* '''365,000+ total dead'''{{sfn|Chambers|Anderson|1999|p=849}}\\n}}\\n----\\n{{indented plainlist|\\n* 282,000+ wounded<ref name=\\\"DCAS\\\" />\\n* 181,193 captured<ref name=\\\"Rhodes1893\\\">{{Cite book |last=Rhodes |first=James Ford |url=http://archive.org/details/historyunitedst20unkngoog |title=History of the United States from the Compromise of 1850 |year=1893 |publisher=Harper & Bros. |location=New York |pages=507\u2013508}}</ref>{{Efn|211,411 Union soldiers were captured, and 30,218 died in prison. The ones who died have been excluded to prevent double-counting of casualties.}}\\n* '''828,000+ total casualties'''\\n}}\"},\"casualties2\":{\"wt\":\"{{indented plainlist|\\n* 94,000+ [[Killed in action|{{abbr|KIA|killed in action}} or {{abbr|DOW|died of wounds}}]]<ref name=\\\"Fox1889\\\" />\\n* 164,000+ died from accidents or disease<ref name=\\\"NationalParkService\\\" />\\n* 26,000\u201331,000 died in Union prisons<ref name=\\\"DCAS\\\" />\\n* '''290,000+ total dead'''\\n}}\\n----\\n{{indented plainlist|\\n* 137,000+ wounded\\n* 436,658 captured<ref name=\\\"Rhodes1893\\\" />{{Efn|462,634 Confederate soldiers were captured and 25,976 died in prison. The ones who died have been excluded to prevent double-counting of casualties.}}\\n* '''864,000+ total casualties'''\\n}}\"},\"casualties3\":{\"wt\":\"{{plainlist|\\n* 50,000 free civilians died<ref name=\\\"Nofi2001\\\" />\\n* 60,000 documented slaves, \\\"tens of thousands\\\" of undocumented slaves died from disease<ref>{{harvnb|Downs|2012}}. \\\"The rough 19th century estimate was that 60,000 former slaves died from the epidemic, but doctors treating black patients often claimed that they were unable to keep accurate records due to demands on their time and the lack of manpower and resources. The surviving records only include the number of black patients whom doctors encountered; tens of thousands of other slaves had no contact with army doctors, leaving no records of their deaths.\\\"</ref>\\n* '''616,222<ref>Toward a Social History of the American Civil War Exploratory Essays, Cambridge University Press, 1990, p. 4.</ref>\u20131,000,000+ total dead'''<ref name=\\\"Hacker2011\\\" /><ref>{{harvnb|Downs|2012}}. \\\"An 2 April 2012 New York Times article, 'New Estimate Raises Civil War Death Toll', reports that a new study ratchets up the death toll from an estimated 650,000 to a staggering 850,000 people. As horrific as this new number is, it fails to reflect the mortality of former slaves during the war. If former slaves were included in this figure, the Civil War death toll would likely be over a million casualties ...\\\".</ref>}}\"},\"conflict\":{\"wt\":\"American Civil War\"}},\"i\":0}}]}' id=\"mwDw\">@media all and (min-width:720px){.mw-parser-output .desktop-float-right{box-sizing:border-box;float:right;clear:right}}.mw-parser-output .infobox.vevent .status>p:first-child{margin:0} American Civil War .mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}} Battle of Gettysburg Battle of Franklin US Horse Artillery Brigade officers Battle of Antietam A Harvest of Death Ironclad USS Atlanta Date April 12, 1861 \u2013 May 26, 1865 [ a ] [ b ] (4 years, 1 month and 2 weeks) Location United States , Atlantic Ocean Result Union victory Territorial changes Dissolution of the Confederate States of America Belligerents United States Confederate States Commanders and leaders .mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0} Abraham Lincoln X Ulysses S. Grant and others... Jefferson Davis ( Prisoner of war</span>\"}]]}'>POW ) Robert E. Lee and others... Strength 698,000 at peak [ 1 ] 2,200,000 total [ 2 ] 360,000 at peak [ 2 ] [ 3 ] 750,000\u20131,000,000 total [ 4 ] Casualties and losses 110,000+ killed in action</span>\"}]]}'>KIA or died of wounds</span>\"}]]}'>DOW 230,000+ died from accidents or disease [ 5 ] [ 6 ] 25,000\u201330,000 died in Confederate prisons [ 2 ] [ 5 ] 365,000+ total dead [ 7 ] 282,000+ wounded [ 6 ] 181,193 captured [ 8 ] [ c ] 828,000+ total casualties 94,000+ killed in action</span>\"}]]}'>KIA or died of wounds</span>\"}]]}'>DOW [ 5 ] 164,000+ died from accidents or disease [ 2 ] 26,000\u201331,000 died in Union prisons [ 6 ] 290,000+ total dead 137,000+ wounded 436,658 captured [ 8 ] [ d ] 864,000+ total casualties 50,000 free civilians died [ 9 ] 60,000 documented slaves, \"tens of thousands\" of undocumented slaves died from disease [ 10 ] 616,222 [ 11 ] \u20131,000,000+ total dead [ 12 ] [ 13 ] .mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist 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a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}} .mw-parser-output .US-history-sidebar{width:22.0em;border:4px double #d69d36}.mw-parser-output .US-history-sidebar .sidebar-title-with-pretitle{background:#002868;color:#FFFFFF;background-clip:padding-box}.mw-parser-output .US-history-sidebar .sidebar-title-with-pretitle a,.mw-parser-output .US-history-sidebar .sidebar-list-title a,.mw-parser-output .US-history-sidebar .mw-collapsible-text{color:#FFFFFF}.mw-parser-output .US-history-sidebar .sidebar-caption{padding-bottom:0.3em}.mw-parser-output .US-history-sidebar .sidebar-list-content{text-align:center}.mw-parser-output .US-history-sidebar .sidebar-list-title{text-align:center;background:#bf0a30;color:#FFFFFF} This article is part of a series on the History of the United States Timeline and periods Prehistoric and Pre-Columbian Era until 1607 Colonial Era 1607\u20131765 1776\u20131789 American Revolution 1765\u20131783 Confederation period 1783\u20131788 1789\u20131815 Federalist Era 1788\u20131801 Jeffersonian Era 1801\u20131817 1815\u20131849 Era of Good Feelings 1817\u20131825 Jacksonian Era 1825\u20131849 1849\u20131865 Civil War Era 1849\u20131865 Greater Reconstruction 1846\u20131898 1865\u20131917 Reconstruction Era 1865\u20131877 Gilded Age 1877\u20131896 Progressive Era 1896\u20131917 1917\u20131945 World War I 1917\u20131918 Roaring Twenties 1918\u20131929 Great Depression 1929\u20131941 World War II 1941\u20131945 1945\u20131964 Post-World War II Era 1945\u20131964 Civil Rights Era 1954\u20131968 1964\u20131980 Civil Rights Era 1954\u20131968 Vietnam War 1964\u20131975 1980\u20131991 Reagan Era 1981\u20131991 1991\u20132016 Post-Cold War Era 1991\u2013present 2016\u2013present 2016\u2013present Topics American Century Antisemitism Civil unrest Racial violence Cultural Cinema Music Newspapers Sports Demography Immigration Economy Banking Education Higher education Flag Government Abortion Capital punishment Civil rights Corruption The Constitution Debt ceiling Direct democracy Foreign policy Law enforcement Postal service Taxation Voting rights Journalism Maritime Military Army Marine Corps Navy Air Force Space Force Coast Guard Party Systems First Second Third Fourth Fifth Sixth Religion Social class Slavery Sexual slavery Technology and industry Agriculture Labor Lumber Medicine Railway Groups African Americans Asian Americans Chinese Americans Filipino Americans Indian Americans Japanese Americans Korean Americans Thai Americans Vietnamese Americans European Americans Albanian Americans English Americans Estonian Americans Finnish Americans German Americans Irish Americans Italian Americans Lithuanian Americans Polish Americans Serbian Americans Hispanic and Latino Americans Mexican Americans Jewish Americans Middle Eastern Americans Egyptian Americans Iranian Americans Iraqi Americans Lebanese Americans Palestinian Americans Saudi Americans Native Americans Cherokee Comanche Pacific Islander Americans Chamorros Hawaiians Women LGBTQ Gay men Lesbians Transgender people Places Territorial evolution Admission to the Union Historic regions American frontier Manifest destiny Indian removal Regions New England The South The West Coast States AL AK AZ AR CA CO CT DE FL GA HI ID IL IN IA KS KY LA ME MD MA MI MN MS MO MT NE NV NH NJ NM NY NC ND OH OK OR PA RI SC SD TN TX UT VT VA WA WV WI WY Territories DC AS GU MP PR VI Cities Urban history Cities Outline List of years Historiography Category Portal v t e The American Civil War (April 12, 1861 \u2013 May 26, 1865; also known by other names ) was a civil war in the United States between the Union [ e ] (\"the North\") and the Confederacy (\"the South\"), which was formed in 1861 by states that had seceded from the Union to preserve slavery in the United States , which they saw as threatened because of the election of Abraham Lincoln and the growing abolitionist movement in the North. [ 14 ] The war lasted a little over four years, ending with Union victory, the dissolution of the Confederacy and the abolition of slavery, freeing four million African Americans . Decades of controversy over slavery came to a head when Abraham Lincoln , a Republican who opposed slavery's expansion, won the 1860 presidential election . Seven Southern slave states responded to Lincoln's victory by seceding from the United States and forming the Confederacy. The Confederacy seized US forts and other federal assets in the South. The war began on April 12, 1861, when the Confederacy bombarded Fort Sumter in South Carolina . A wave of enthusiasm for war swept over the North and South, as military recruitment soared. Four more Southern states seceded after the war began and, led by its president, Jefferson Davis , the Confederacy comprised eleven states, containing a third of the US population. Four years of intense combat, mostly in the South, ensued. During 1861\u20131862 in the western theater , the Union made permanent gains\u2014though in the eastern theater the conflict was inconclusive. The abolition of slavery became a Union war goal on January 1, 1863, when Lincoln issued the Emancipation Proclamation , which declared all slaves in rebel states to be free, applying to more than 3.5 million of the 4 million enslaved people in the country. To the west, the Union first destroyed the Confederacy's river navy by the summer of 1862, then much of its western armies, and seized New Orleans . The successful 1863 Union siege of Vicksburg split the Confederacy in two at the Mississippi River , while Confederate general Robert E. Lee 's incursion north failed at the Battle of Gettysburg . General Ulysses S. Grant 's western successes led Lincoln to promote him to command of all Union armies in 1864. Inflicting an ever-tightening naval blockade of Confederate ports, the Union marshaled resources and manpower to attack the Confederacy from all directions. This led to the fall of Atlanta in 1864 to Union general William Tecumseh Sherman , followed by his March to the Sea , which culminated in his taking Savannah . The last significant battles raged around the ten-month Siege of Petersburg , gateway to the Confederate capital of Richmond . The Confederates abandoned Richmond, and on April 9, 1865, Lee surrendered to Grant following the Battle of Appomattox Court House , setting in motion the end of the war . [ f ] Lincoln lived to see this victory but was shot by an assassin on April 14, dying the next day. By the end of the war, much of the South's infrastructure had been destroyed. The Confederacy collapsed, slavery was abolished, and four million enslaved black people were freed. The war-torn nation then entered the Reconstruction era in an attempt to rebuild the country, bring the former Confederate states back into the United States, and grant civil rights to freed slaves. The war is one of the most extensively studied and written about episodes in the history of the United States . It remains the subject of cultural and historiographical debate . Of continuing interest is the myth of the Lost Cause of the Confederacy . The war was among the first to use industrial warfare . Railroads, the electrical telegraph , steamships, the ironclad warship , and mass-produced weapons were widely used. The war left an estimated 700,000 soldiers dead, along with an undetermined number of civilian deaths, making it the deadliest in American history. [ g ] The technology and brutality of the Civil War foreshadowed the coming world wars . Origins .mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}} Main article: Origins of the American Civil War Further information: Timeline of events leading to the American Civil War , Slave states and free states , Slavery in the United States , and Abolitionism in the United States The origins of the war were rooted in the desire of the Southern states to preserve the institution of slavery . [ 15 ] Historians in the 21st century overwhelmingly agree on the centrality of slavery in the conflict\u2014at least for the Southern states. They disagree on the North 's reasons for refusing to allow the Southern states to secede. [ 16 ] The pseudo-historical Lost Cause ideology denies that slavery was the principal cause of the secession, a view disproven by historical evidence, notably some of the seceding states' own secession documents . [ 17 ] After leaving the Union, Mississippi issued a declaration stating, \"Our position is thoroughly identified with the institution of slavery\u2014the greatest material interest of the world.\" [ 18 ] [ 19 ] The principal political battle leading to Southern secession was over whether slavery would expand into the Western territories destined to become states. Initially Congress had admitted new states into the Union in pairs, one slave and one free . This had kept a sectional balance in the Senate but not in the House of Representatives , as free states outstripped slave states in numbers of eligible voters. [ 20 ] Thus, at mid-19th century, the free-versus-slave status of the new territories was a critical issue, both for the North, where anti-slavery sentiment had grown, and for the South, where the fear of slavery's abolition had grown. Another factor leading to secession and the formation of the Confederacy was the development of white Southern nationalism in the preceding decades. [ 21 ] The primary reason for the North to reject secession was to preserve the Union, a cause based on American nationalism . [ 22 ] Background factors in the run up to the Civil War were partisan politics , abolitionism, nullification versus secession , Southern and Northern nationalism, expansionism , economics , and modernization in the antebellum period . As a panel of historians said in 2011, \"while slavery and its various and multifaceted discontents were the primary cause of disunion, it was disunion itself that sparked the war.\" [ 23 ] Lincoln's election Main article: 1860 United States presidential election Portrait of Abraham Lincoln , an 1860 photograph portrait of Abraham Lincoln by Mathew Brady Abraham Lincoln won the 1860 presidential election. [ 24 ] Southern leaders feared Lincoln would stop slavery's expansion and put it on a course toward extinction. [ 25 ] His victory triggered declarations of secession by seven slave states of the Deep South , all of whose riverfront or coastal economies were based on cotton that was cultivated by slave labor. Lincoln was not inaugurated until March 4, 1861, four months after his 1860 election, which afforded the South time to prepare for war. [ 26 ] Nationalists in the North and \"Unionists\" in the South refused to accept the declarations of secession, and no foreign government ever recognized the Confederacy. The US government , under President James Buchanan , refused to relinquish the nation's forts, which the Confederacy claimed were located in their territory. According to Lincoln, the American people had demonstrated, beginning with their victory in the American Revolution and Revolutionary War and subsequent establishment of a sovereign nation, that they could successfully establish and administer a republic. Yet, Lincoln believed, a question remained unanswered: Could the nation be maintained as a republic, with its government selected by vote of the people, in the face of internal attempts to destroy it or separate from it? [ 27 ] Outbreak of the war Secession crisis Main article: Ordinance of Secession Status of the states, 1861 .mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{} Slave states that seceded before April 15, 1861 Slave states that seceded after April 15, 1861 Border Southern states that permitted slavery but did not secede (both KY and MO had dual competing Confederate and Unionist governments) Union states that banned slavery Territories Lincoln's election provoked South Carolina 's legislature to call a state convention to consider secession. South Carolina had done more than any other state to advance the notion that a state had the right to nullify federal laws and even secede. On December 20, 1860, the convention unanimously voted to secede and adopted a secession declaration . It argued for states' rights for slave owners but complained about states' rights in the North in the form of resistance to the federal Fugitive Slave Act, claiming that Northern states were not fulfilling their obligations to assist in the return of fugitive slaves. The \"cotton states\" of Mississippi , Florida , Alabama , Georgia , Louisiana , and Texas followed suit, seceding in January and February 1861. [ 26 ] Division of the states during the American Civil War: Union Confederacy Border states Territories Among the ordinances of secession, those of Texas, Alabama, and Virginia mentioned the plight of the \"slaveholding states\" at the hands of Northern abolitionists. The rest made no mention of slavery but were brief announcements by the legislatures of the dissolution of ties to the Union. [ 28 ] However, at least four\u2014South Carolina, [ 29 ] Mississippi, [ 30 ] Georgia, [ 31 ] and Texas [ 32 ] \u2014provided detailed reasons for their secession, all blaming the movement to abolish slavery and its influence over the North. Southern states believed that the Fugitive Slave Clause made slaveholding a constitutional right. These states agreed to form a new federal government, the Confederate States of America , on February 4, 1861. [ 33 ] They took control of federal forts and other properties within their boundaries, with little resistance from outgoing president James Buchanan , whose term ended on March 4. Buchanan said the Dred Scott decision was proof the Southern states had no reason to secede and that the Union \"was intended to be perpetual\". He added, however, that \"The power by force of arms to compel a State to remain in the Union\" was not among the \"enumerated powers granted to Congress\". [ 34 ] A quarter of the US army\u2014the Texas garrison\u2014was surrendered in February to state forces by its general, David E. Twiggs , who joined the Confederacy. [ 35 ] Referring to the seven Southern states that initially seceded, James McPherson wrote, \"Slaves constituted 47 percent of the population of the Confederate states but only 24 percent in the upper South.\" [ 36 ] He added, \"In the four border states the proportion of slaves and slaveowners was less than half what it was in the eleven states that seceded.\" [ 37 ] Eastern Tennessee and western Virginia also had less slavery and showed more support for the Union than the rest of the Confederacy. West Virginia left the rest of Virginia and joined the Union as West Virginia because of the slavery issue. Even within Virginia and Tennessee, which had seceded, McPherson wrote, \"The voters in 35 Virginia counties with a slave population of only 2.5 percent opposed secession by a margin of three to one, while voters in the remainder of the state, where slaves constituted 36 percent of the population, supported secession by more than ten to one. The thirty counties of east Tennessee that rejected secession by more than two to one contained a slave population of only 8 percent, while the rest of the state, with a slave population of 30 percent, voted for secession by a margin of seven to one.\" [ 38 ] As Southerners resigned their Senate and House seats, Republicans could pass projects that had been blocked. These included the Morrill Tariff , land grant colleges , a Homestead Act , a transcontinental railroad, [ 39 ] the National Bank Act , authorization of United States Notes by the Legal Tender Act of 1862 , the end of slavery in the District of Columbia , and a ban on slavery in the territories. [ 40 ] The Revenue Act of 1861 introduced an income tax to help finance the war. [ 41 ] Jefferson Davis , President of the Confederate States of America (1861\u20131865) In December 1860, the Crittenden Compromise was proposed to re-establish the Missouri Compromise line, by constitutionally banning slavery in territories to the north of it, while permitting it to the south. The Compromise would likely have prevented secession, but Lincoln and the Republicans rejected it. [ 42 ] Lincoln stated that any compromise that would extend slavery would bring down the Union. [ 43 ] A February peace conference met in Washington, proposing a solution similar to the Compromise; it was rejected by Congress. The Republicans proposed the Corwin Amendment , an alternative, not to interfere with slavery where it existed, but the South regarded it as insufficient. The remaining eight slave states rejected pleas to join the Confederacy, following a no-vote in Virginia's First Secessionist Convention on April 4. [ 44 ] On March 4, Lincoln was sworn in as president. In his first inaugural address , he argued that the Constitution was a more perfect union than the earlier Articles of Confederation and Perpetual Union , was a binding contract, and that secession was \"legally void\". [ 45 ] He did not intend to invade Southern states, nor to end slavery where it existed, but he said he would use force to maintain possession of federal property, [ 45 ] including forts, arsenals, mints, and customhouses that had been seized. [ 46 ] \"The mails, unless repelled, will continue to be furnished in all parts of the Union.\" Where conditions did not allow peaceful enforcement of federal law, US marshals and judges would be withdrawn. No mention was made of bullion lost from mints. He stated that it would be US policy \"to collect the duties and imposts\"; \"there will be no invasion, no using of force against or among the people anywhere\" that would justify an armed revolution. His speech closed with a plea for restoration of the bonds of union, famously calling on \"the mystic chords of memory\" binding the two regions. [ 45 ] The Confederacy sent delegates to Washington to negotiate a peace treaty. Lincoln rejected negotiations, because he claimed that the Confederacy was not a legitimate government and to make a treaty with it would recognize it as such. [ 47 ] Lincoln instead attempted to negotiate directly with the governors of seceded states, whose administrations he continued to recognize. [ 48 ] Complicating Lincoln's attempts to defuse the crisis was Secretary of State William H. Seward , who had been Lincoln's rival for the Republican nomination . Embittered by his defeat, Seward agreed to support Lincoln's candidacy only after he was guaranteed the executive office then considered the second most powerful. In the early stages of Lincoln's presidency Seward held little regard for him, due to his perceived inexperience. Seward viewed himself as the de facto head of government, the \" prime minister \" behind the throne. Seward attempted to engage in unauthorized and indirect negotiations that failed. [ 47 ] Lincoln was determined to hold all remaining Union-occupied forts in the seceded states: Fort Pickens , Fort Jefferson , and Fort Taylor in Florida, and Fort Sumter in South Carolina. [ 49 ] Battle of Fort Sumter Main article: Battle of Fort Sumter See also: Proclamation 80 The Battle of Fort Sumter, as depicted by Currier and Ives The American Civil War began on April 12, 1861, when Confederate forces opened fire on the Union-held Fort Sumter. Fort Sumter is located in the harbor of Charleston , South Carolina. [ 50 ] Its status had been contentious for months. Outgoing president Buchanan had dithered in reinforcing its garrison, commanded by Major Robert Anderson . Anderson took matters into his own hands and on December 26, 1860, under the cover of darkness, sailed the garrison from the poorly placed Fort Moultrie to the stalwart island Fort Sumter. [ 51 ] Anderson's actions catapulted him to hero status in the North. An attempt to resupply the fort on January 9, 1861, failed and nearly started the war then, but an informal truce held. [ 52 ] On March 5, Lincoln was informed the fort was low on supplies. [ 53 ] Fort Sumter proved a key challenge to Lincoln's administration. [ 53 ] Back-channel dealing by Seward with the Confederates undermined Lincoln's decision-making; Seward wanted to pull out. [ 54 ] But a firm hand by Lincoln tamed Seward, who was a staunch Lincoln ally thereafter. Lincoln decided holding the fort, which would require reinforcing it, was the only workable option. On April 6, Lincoln informed the Governor of South Carolina that a ship with food but no ammunition would attempt to supply the fort. Richard N. Current wrote: Current, Richard N. (1963). [https://archive.org/details/lincolnfirstshot00curr ''Lincoln and the First Shot''] J. B. Lippincott Company, pp. 193-194, quoting [[James G. Randall|Randall, James G.]] (1945). ''Lincoln the President'', vol. 1. New York: Dodd, Mead, p. 350.</ref>\"}},\"i\":0}}]}' id=\"mwAgk\">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}} In short, it appears that Lincoln, when he decided to send the Sumter expedition, considered hostilities to be probable . It also appears, however, that he believed an unopposed and peaceable provisioning to be at least barely possible .... He thought hostilities would be the likely result, and he was determined that, if they should be, they must clearly be initiated by the Confederates. \"To say that Lincoln meant that the first shot would be fired by the other side if a first shot was fired , ... is not to say that he maneuvered to have the first shot fired.\" [ 55 ] James McPherson describes this win-win approach as \"the first sign of the mastery that would mark Lincoln's presidency\"; the Union would win if it could resupply and hold the fort, and the South would be the aggressor if it opened fire on an unarmed ship supplying starving men. [ 56 ] An April 9 Confederate cabinet meeting resulted in Davis ordering General P. G. T. Beauregard to take the fort before supplies reached it. [ 57 ] At 4:30 a.m. on April 12, Confederate forces fired the first of 4,000 shells at the fort; it fell the next day. The loss of Fort Sumter lit a patriotic fire under the North. [ 58 ] On April 15, Lincoln called on the states to field 75,000 militiamen for 90 days; impassioned Union states met the quotas quickly. [ 59 ] On"]