View source for Eclipse

{{short description|Astronomical event where one body is hidden by another}}
{{Other uses}}
{{redirect|Total eclipse}}{{Distinguish|Eclipes}}
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[[File:Solar eclipse 1999 4.jpg|thumb|250px|right|Totality during the [[Solar eclipse of August 11, 1999|1999]] solar eclipse. [[Solar prominence]]s can be seen along the limb (in red) as well as extensive [[solar corona|coronal]] filaments.]]
[[File:ISS-52 Eclipse 2017 Umbra Viewed from Space (1).jpg|thumb|250px|right|The shadow of an eclipse on Earth as seen from space]]

An '''eclipse''' is an [[astronomical event]] which occurs when an [[astronomical object]] or [[spacecraft]] is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three celestial objects is known as a [[syzygy (astronomy)|''syzygy'']].<ref>{{cite press release |author=Staff |date=March 31, 1981 |work=The New York Times |title=Science Watch: A Really Big Syzygy |url=https://query.nytimes.com/gst/fullpage.html?sec=health&res=9F02E5DB1039F932A05750C0A967948260&fta=y |access-date=2008-02-29 |url-status=live |archive-url=https://web.archive.org/web/20081210100651/http://query.nytimes.com/gst/fullpage.html?sec=health&res=9F02E5DB1039F932A05750C0A967948260&fta=y |archive-date=December 10, 2008 }}</ref> An eclipse is the result of either an ''[[occultation]]'' (completely hidden) or a [[transit (astronomy)|''transit'']] (partially hidden). A "deep eclipse" (or "deep occultation") is when a small astronomical object is behind a bigger one.<ref name="QZ-2023">{{cite web |author=Staff |title=PHYS 1350 Astronomy Exam 3 (TXST-Olson) |url=https://quizlet.com/341047631/phys-1350-astronomy-exam-3-txst-olson-flash-cards/ |date=2023 |work=[[Quizlet]] |url-status=live |archiveurl=https://archive.today/20231109125204/https://quizlet.com/341047631/phys-1350-astronomy-exam-3-txst-olson-flash-cards/ |archivedate=9 November 2023 |accessdate=9 November 2023 }} "What is a deep eclipse? The smaller star is behind the bigger star"</ref><ref name="AT-20231107">{{cite news |author=Miller, A.M. |display-authors=et al.|title=ATel #16328 - ASASSN-23ht: A Deep Eclipse Event |url=https://www.astronomerstelegram.org/?read=16328 |date=7 November 2023 |work=[[The Astronomer's Telegram]] |url-status=live |archiveurl=https://archive.today/20231109132351/https://www.astronomerstelegram.org/?read=16328 |archivedate=9 November 2023 |accessdate=9 November 2023 }}</ref>

The term ''eclipse'' is most often used to describe either a [[solar eclipse]], when the [[Moon]]'s shadow crosses the [[Earth]]'s surface, or a [[lunar eclipse]], when the Moon moves into the Earth's shadow. However, it can also refer to such events beyond the Earth–Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A [[binary star]] system can also produce eclipses if the plane of the [[orbit]] of its constituent stars intersects the observer's position.

For the special cases of solar and lunar eclipses, these only happen during an "[[eclipse season]]", the two times of each year when the plane of the Earth's orbit around the Sun crosses with the plane of the Moon's orbit around the Earth and the line defined by the intersecting planes points near the Sun. The [[Solar eclipse#Types|type of solar eclipse]] that happens during each season (whether total, annular, hybrid, or partial) depends on [[apparent size]]s of the Sun and Moon. If the orbit of the Earth around the Sun and the Moon's orbit around the Earth were both in the same plane with each other, then eclipses would happen every month. There would be a lunar eclipse at every full moon, and a solar eclipse at every new moon. It is because of the non-planar differences that eclipses are not a common event.  If both orbits were perfectly circular, then each eclipse would be the same type every month.

Lunar eclipses can be viewed from the entire nightside half of the Earth. But solar eclipses, particularly total eclipses occurring at any one particular point on the Earth's surface, are very rare events that can be many decades apart.

==Etymology==
The term is derived from the [[ancient Greek]] noun {{lang|grc|ἔκλειψις}} (''{{lang|grc-Latn|ékleipsis}}''), which means 'the abandonment', 'the downfall', or 'the darkening of a heavenly body', which is derived from the verb {{lang|grc|ἐκλείπω}} (''{{lang |grc-Latn|ekleípō}}'') which means 'to abandon', 'to darken', or 'to cease to exist',<ref>{{cite web  |url=http://www.in.gr/dictionary/lookup.asp?Word=%E5%EA%EB%E5%DF%F0%F9+++&x=0&y=0  |access-date=2009-09-24  |title=in.gr  |archive-url=https://web.archive.org/web/20180511130944/http://www.in.gr/dictionary/lookup.asp/?Word=%E5%EA%EB%E5%DF%F0%F9+++&x=0&y=0  |archive-date=2018-05-11  |url-status=dead }}</ref> a combination of prefix {{lang|grc|ἐκ-}} (''{{lang|grc-Latn|ek-}}''), from preposition {{lang|grc|ἐκ}} (''{{lang|grc-Latn|ek}}''), 'out', and of verb {{lang|grc|λείπω}} (''{{lang|grc-Latn|leípō}}''), 'to be absent'.<ref>{{cite web|url=http://www.lingvozone.com/main.jsp?action=translation&do=dictionary&language_id_from=23&language_id_to=8&word=%CE%BB%CE%B5%CE%AF%CF%80%CF%89+&t.x=55&t.y=16 |title=LingvoSoft|website=lingvozone.com|url-status=live|archive-url=https://archive.today/20130128095850/http://www.lingvozone.com/main.jsp?action=translation&do=dictionary&language_id_from=23&language_id_to=8&word=%CE%BB%CE%B5%CE%AF%CF%80%CF%89+&t.x=55&t.y=16 |archive-date=2013-01-28}}</ref><ref>{{cite web|url=https://translate.google.com/translate_t?prev=hp&hl=en&js=y&text=%CE%BB%CE%B5%CE%AF%CF%80%CF%89&sl=el&tl=en&history_state0=&swap=1#|title=Google Translate|website=translate.google.com}}</ref>

== Umbra, penumbra and antumbra ==
{{Main|Umbra, penumbra and antumbra}}
{{more citations needed|section|date=November 2017}}

[[File:Umbra01.svg|thumb|upright=1.3|Umbra, penumbra and antumbra cast by an opaque object occulting a larger light source]]
For any two objects in space, a line can be extended from the first through the second. The latter object will block some amount of light being emitted by the former, creating a region of shadow around the axis of the line. Typically these objects are moving with respect to each other and their surroundings, so the resulting shadow will sweep through a region of space, only passing through any particular location in the region for a fixed interval of time. As viewed from such a location, this shadowing event is known as an eclipse.<ref name=westfall2014>{{citation | title=Celestial Shadows: Eclipses, Transits, and Occultations | volume=410 | series=Astrophysics and Space Science Library | first1=John | last1=Westfall | first2=William | last2=Sheehan | publisher=Springer | year=2014 | isbn=978-1493915354 | pages=1–5 | url=https://books.google.com/books?id=W9mLBQAAQBAJ&pg=PA1 | postscript=. }}</ref>

Typically the cross-section of the objects involved in an astronomical eclipse is roughly disk-shaped.<ref name=westfall2014/> The region of an object's shadow during an eclipse is divided into three parts:<ref name=glossary>{{cite web | last=Espenak | first=Fred | date=September 21, 2007 | url=http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/SEglossary.html | title=Glossary of Solar Eclipse Terms | publisher=NASA | access-date=2008-02-28 | url-status=dead | archive-url=https://web.archive.org/web/20080224074526/http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/SEglossary.html | archive-date=February 24, 2008 }}</ref>
* The ''umbra'' (Latin for 'shadow'), within which the object completely covers the light source. For the [[Sun]], this light source is the photosphere.
* The ''antumbra'' (from Latin ''ante'', 'before, in front of', plus ''umbra'') extending beyond the tip of the umbra, within which the object is completely in front of the light source but too small to completely cover it.
* The ''penumbra'' (from the Latin ''paene'', 'almost, nearly', plus ''umbra''), within which the object is only partially in front of the light source.

[[File:Solar eclipse types.svg|thumb|upright=0.9|Sun-Moon configurations that produce a total (A), annular (B), and partial (C) solar eclipse|alt=|left]]
A '''total eclipse''' occurs when the observer is within the umbra, an '''annular eclipse''' when the observer is within the antumbra, and a '''partial eclipse''' when the observer is within the penumbra. During a lunar eclipse only the umbra and penumbra are applicable, because the antumbra of the Sun-Earth system lies far beyond the Moon. Analogously, Earth's apparent diameter from the viewpoint of the Moon is nearly four times that of the Sun and thus cannot produce an annular eclipse. The same terms may be used analogously in describing other eclipses, e.g., the antumbra of [[Deimos (moon)|Deimos]] crossing [[Mars]], or [[Phobos (moon)|Phobos]] entering Mars's penumbra.

The ''first contact'' occurs when the eclipsing object's disc first starts to impinge on the light source; ''second contact'' is when the disc moves completely within the light source; ''third contact'' when it starts to move out of the light; and ''fourth'' or ''last contact'' when it finally leaves the light source's disc entirely.

For spherical bodies, when the occulting object is smaller than the star, the length (''L'') of the umbra's cone-shaped shadow is given by:

:<math>L\ =\ \frac{r \cdot R_o}{R_s - R_o}</math>

where ''R<sub>s</sub>'' is the radius of the star, ''R<sub>o</sub>'' is the occulting object's radius, and ''r'' is the distance from the star to the occulting object. For [[Earth]], on average ''L'' is equal to 1.384{{e|6}}&nbsp;[[kilometer|km]], which is much larger than the Moon's [[semimajor axis]] of 3.844{{e|5}}&nbsp;km. Hence the umbral cone of the Earth can completely envelop the Moon during a [[lunar eclipse]].<ref>{{cite book 
|first=Robin M. |last=Green |date=1985 
|title=Spherical Astronomy |publisher=Oxford University Press 
|isbn=978-0-521-31779-5 }}</ref> If the occulting object has an atmosphere, however, some of the luminosity of the star can be [[refraction|refracted]] into the volume of the umbra. This occurs, for example, during an eclipse of the Moon by the Earth&mdash;producing a faint, [[red|ruddy]] illumination of the Moon even at totality.

On Earth, the shadow cast during an eclipse moves very approximately at 1&nbsp;km per sec. This depends on the location of the shadow on the Earth and the angle in which it is moving.<ref>{{cite web|url=http://www.sciforums.com/threads/speed-of-eclipse-shadow.53722/|title=Speed of eclipse shadow? - Sciforums|website=sciforums.com|date=31 March 2006 |url-status=live|archive-url=https://web.archive.org/web/20150402094757/http://www.sciforums.com/threads/speed-of-eclipse-shadow.53722/|archive-date=2015-04-02}}</ref>

== Eclipse cycles ==
{{Main|Eclipse cycle}}
[[File:Eclipse vs new or full moons, annotated.svg|thumb|As the Earth revolves around the Sun, approximate [[axial parallelism]] of the Moon's [[Orbital inclination|tilted]] orbital plane (inclined at five degrees to the [[ecliptic|Earth's orbital plane]]) results in the revolution of the [[lunar nodes]] relative to the Earth. This causes an [[eclipse season]] approximately every six months, in which a [[solar eclipse]] can occur at the [[new moon]] phase and a lunar eclipse can occur at the [[full moon]] phase.]]
An [[eclipse cycle]] takes place when eclipses in a series are separated by a certain interval of time. This happens when the orbital motions of the bodies form repeating harmonic patterns. A particular instance is the [[saros (astronomy)|saros]], which results in a repetition of a solar or lunar eclipse every 6,585.3&nbsp;days, or a little over 18 years. Because this is not a whole number of days, successive eclipses will be visible from different parts of the world.<ref>{{cite web
 |last=Espenak 
 |first=Fred 
 |date=July 12, 2007 
 |url=http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html 
 |title=Eclipses and the Saros 
 |publisher=NASA 
 |access-date=2007-12-13 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20071030225501/http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html 
 |archive-date=2007-10-30 
}}</ref> In one saros period there are 239.0 anomalistic periods, 241.0 sidereal periods, 242.0 nodical periods, and 223.0 synodic periods. Although the [[orbit of the Moon]] does not give exact integers, the numbers of orbit cycles are close enough to integers to give strong similarity for eclipses spaced at 18.03 yr intervals.

==Earth–Moon system==
[[Image:Lunar eclipse diagram-en.svg|240px|thumb|A symbolic orbital diagram from the view of the Earth at the center, with the Sun and Moon projected upon the [[celestial sphere]], showing the Moon's two nodes where eclipses can occur.]]
An eclipse involving the Sun, Earth, and Moon can occur only when they are nearly in a straight line, allowing one to be hidden behind another, viewed from the third. Because the [[orbit of the Moon|orbital plane of the Moon]] is tilted with respect to the orbital plane of the Earth (the [[ecliptic]]), eclipses can occur only when the Moon is close to the intersection of these two planes (the [[node (astronomy)|node]]s). The Sun, Earth and nodes are aligned twice a year (during an [[eclipse season]]), and eclipses can occur during a period of about two months around these times. There can be from four to seven eclipses in a calendar year, which repeat according to various [[eclipse cycle]]s, such as a [[saros (astronomy)|saros]].

Between 1901 and 2100 there are the maximum of seven eclipses in:<ref>{{cite web|url=http://moonblink.info/Eclipse/lists/stats |title=Eclipse Statistics|website=moonblink.info|url-status=live|archive-url=https://web.archive.org/web/20140527212303/http://moonblink.info/Eclipse/lists/stats|archive-date=2014-05-27|first = Ian Cameron |last =Smith}}</ref>
* four (penumbral) lunar and three solar eclipses: 1908, [[Solar eclipse of December 26, 2038#Related eclipses|2038]].
* four solar and three lunar eclipses: 1918, [[December 1982 lunar eclipse#Related eclipses|1973]], 2094.
* five solar and two lunar eclipses: 1934.

Excluding penumbral lunar eclipses, there are a maximum of seven eclipses in:<ref>{{cite web|url=https://webspace.science.uu.nl/~gent0113/eclipse/eclipsecycles.htm|title=A Catalogue of Eclipse Cycles|first=R.H. van|last=Gent|website=webspace.science.uu.nl|url-status=live|archive-url=https://web.archive.org/web/20110905080517/http://www.staff.science.uu.nl/~gent0113/eclipse/eclipsecycles.htm|archive-date=2011-09-05}}</ref>
* 1591, 1656, 1787, 1805, 1918, 1935, 1982, and 2094.

===Solar eclipse===
{{main|Solar eclipse}}
[[File:Total_Solar_Eclipse_-_April_8,_2024_-_Mazatlan_Mexico_-_Ten_Minute_Time_Lapse_v2_1080p.webm|thumb|Ten Minute [[Time-lapse photography|Time Lapse]] Video of the [[Solar eclipse of April 8, 2024|Total Solar Eclipse on April 8, 2024]], in [[Mazatlán]], [[Mexico]].]]
[[Image:2008-08-01 Solar eclipse progression with timestamps.jpg|thumb|The progression of a [[solar eclipse]] on August 1, 2008, viewed from [[Novosibirsk, Russia]]. The time between shots is three minutes.|alt=|left]]
As observed from the Earth, a [[solar eclipse]] occurs when the Moon passes in front of the Sun. The type of solar eclipse event depends on the distance of the Moon from the Earth during the event. A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's shadow. When the umbra does not reach the surface of the Earth, the Sun is only partially occulted, resulting in an annular eclipse. Partial solar eclipses occur when the viewer is inside the penumbra.<ref>{{cite web
 |first       = R.
 |last        = Hipschman
 |title       = Solar Eclipse: Why Eclipses Happen
 |url         = http://www.exploratorium.edu/eclipse/why.html
 |access-date  = 2008-12-01
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20081205073238/http://www.exploratorium.edu/eclipse/why.html
 |archive-date = 2008-12-05
|date        = 2015-10-29
 }}</ref>
[[File:Solar eclipse visualisation.svg|thumb|upright|Each icon shows the view from the centre of its black spot, representing the Moon (not to scale)]]
The [[Magnitude of eclipse|eclipse magnitude]] is the fraction of the Sun's diameter that is covered by the Moon. For a total eclipse, this value is always greater than or equal to one. In both annular and total eclipses, the eclipse magnitude is the ratio of the angular sizes of the Moon to the Sun.<ref>{{cite book 
|first=Martin V. |last=Zombeck |date=2006 
|title=Handbook of Space Astronomy and Astrophysics 
|url=https://archive.org/details/handbookspaceast00zomb_313 |url-access=limited |edition=Third |page=[https://archive.org/details/handbookspaceast00zomb_313/page/n61 48]
|publisher=Cambridge University Press 
|isbn=978-0-521-78242-5 }}</ref>

Solar eclipses are relatively brief events that can only be viewed in totality along a relatively narrow track. Under the most favorable circumstances, a total solar eclipse can last for 7&nbsp;minutes, 31&nbsp;seconds, and can be viewed along a track that is up to 250&nbsp;km wide. However, the region where a partial eclipse can be observed is much larger. The Moon's umbra will advance eastward at a rate of 1,700&nbsp;km/h, until it no longer intersects the Earth's surface.

[[File:Geometry of a Total Solar Eclipse.svg|thumb|300px|right|Geometry of a total solar eclipse (not to scale)]]

During a solar eclipse, the Moon can sometimes perfectly cover the Sun because its apparent size is nearly the same as the Sun's when viewed from the Earth. A total solar eclipse is in fact an [[occultation]] while an annular solar eclipse is a [[Astronomical transit|transit]].

When observed at points in space other than from the Earth's surface, the Sun can be eclipsed by bodies other than the Moon. Two examples include when the crew of [[Apollo 12]] observed the [[:File:Earth Eclipses Sun-ap12-s80-37406.jpg|Earth to eclipse the Sun]] in 1969 and when the ''[[Cassini–Huygens|Cassini]]'' [[Space probe|probe]] observed [[:File:Saturn eclipse.jpg|Saturn to eclipse the Sun]] in 2006.[[Image:Eclipse lune.jpg|thumb|250px|The progression of a [[lunar eclipse]] from right to left. Totality is shown with the first two images. These required a longer [[exposure time]] to make the details visible.|alt=|left]]

===Lunar eclipse===
{{main|Lunar eclipse}}Lunar eclipses occur when the Moon passes through the Earth's shadow. This happens only during a [[full moon]], when the Moon is on the far side of the Earth from the Sun. Unlike a solar eclipse, an eclipse of the Moon can be observed from nearly an entire hemisphere. For this reason it is much more common to observe a lunar eclipse from a given location. A lunar eclipse lasts longer, taking several hours to complete, with totality itself usually averaging anywhere from about 30 minutes to over an hour.<ref>{{cite web
 |author      = Staff
 |date        = January 6, 2006
 |url         = http://www.crh.noaa.gov/fsd/astro/suneclipse.php
 |title       = Solar and Lunar Eclipses
 |publisher   = NOAA
 |access-date  = 2007-05-02
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20070512191007/http://www.crh.noaa.gov/fsd/astro/suneclipse.php
 |archive-date = May 12, 2007
}}</ref>

There are three types of lunar eclipses: penumbral, when the Moon crosses only the Earth's penumbra; partial, when the Moon crosses partially into the Earth's [[umbra]]; and total, when the Moon crosses entirely into the Earth's umbra. Total lunar eclipses pass through all three phases. Even during a total lunar eclipse, however, the Moon is not completely dark. Sunlight refracted through the Earth's atmosphere enters the umbra and provides a faint illumination. Much as in a sunset, the atmosphere tends to more strongly scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue,<ref>
{{cite web |last=Phillips |first=Tony |date=February 13, 2008 |url=https://science.nasa.gov/headlines/y2008/13feb_lunareclipse.htm |title=Total Lunar Eclipse |publisher=NASA |access-date=2008-03-03 |url-status=dead |archive-url=https://web.archive.org/web/20080301221225/http://science.nasa.gov/headlines/y2008/13feb_lunareclipse.htm |archive-date=March 1, 2008 }}</ref> thus the phrase 'Blood Moon' is often found in descriptions of such lunar events as far back as eclipses are recorded.<ref>Ancient Timekeepers, {{cite web |url=http://blog.world-mysteries.com/science/ancient-timekeepers-part-1-movements-of-the-earth/ |title=Ancient Timekeepers, Part 1: Movements of the Earth |access-date=2011-10-25 |url-status=live |archive-url=https://web.archive.org/web/20111026041145/http://blog.world-mysteries.com/science/ancient-timekeepers-part-1-movements-of-the-earth/ |archive-date=2011-10-26 |date=2011-09-16 }}</ref>

===Historical record===
[[File:Les parisiens pendant l'éclipse du 28 Juillet.jpg|alt=|left|thumb|This print shows Parisians watching the solar eclipse of July 28, 1851|262x262px]]
Records of solar eclipses have been kept since ancient times. Eclipse dates can be used for [[chronological dating]] of historical records. A [[Syria]]n clay tablet, in the Ugaritic language, records a solar eclipse which occurred on March 5, 1223, B.C.,<ref>{{cite journal |last1=de Jong |first1=T. |last2=van Soldt |first2=W. H. |title=The earliest known solar eclipse record redated |journal=Nature |date=1989 |volume=338 |issue=6212 |pages=238–240 |doi=10.1038/338238a0 |bibcode=1989Natur.338..238D |s2cid=186243477 | quote=The new translation runs as follows: (Obverse) "On the ... day of the new moon in [the month] ''ḫiyaru'' the Sun went down, its gate-keeper was ''Ršp''". (Reverse) "Two livers were examined: danger". [...] As pointed out by Sawyer and Stephenson, ''Ršp'' is probably to be identified with the planet Mars. [...] Of the candidate eclipses [...], the one occurring on 5 March 1223 BC is the only one during which the plant Mars was above the horizon. }}</ref> while Paul Griffin argues that a stone in Ireland records an eclipse on November 30, 3340 B.C.<ref>{{cite web
 |last        = Griffin
 |first       = Paul
 |date        = 2002
 |url         = http://www.astronomy.ca/3340eclipse/
 |title       = Confirmation of World's Oldest Solar Eclipse Recorded in Stone
 |publisher   = The Digital Universe
 |access-date  = 2007-05-02
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20070409070529/http://www.astronomy.ca/3340eclipse/
 |archive-date = 2007-04-09
}}</ref> Positing classical-era astronomers' use of Babylonian eclipse records mostly from the 13th century BC provides a feasible and mathematically consistent<ref><!--

-->See [http://www.dioi.org/vols/wg0.pdf DIO 16] {{webarchive|url=https://web.archive.org/web/20110726000734/http://www.dioi.org/vols/wg0.pdf |date=2011-07-26 }} p.2 (2009). Though those Greek and perhaps Babylonian astronomers who determined the three previously unsolved lunar motions were spread over more than four centuries (263 BC to 160 AD), the math-indicated early eclipse records are all from a [http://www.dioi.org/thr.htm#ufnr much smaller span] {{webarchive|url=https://web.archive.org/web/20150402105220/http://www.dioi.org/thr.htm |date=2015-04-02 }}: the 13th century BC. The anciently attested Greek technique: use of eclipse cycles, automatically providing integral ratios, which is how all ancient astronomers' lunar motions were expressed. Long-eclipse-cycle-based reconstructions precisely produce all of the 24 digits appearing in the three attested ancient motions just cited: 6247 synod = 6695 anom (System A), 5458 synod = 5923 drac (Hipparchos), 3277 synod = 3512 anom (Planetary Hypotheses). By contrast, the System B motion, 251 synod = 269 anom (Aristarchos?), could have been determined without recourse to remote eclipse data, simply by using a few eclipse-pairs 4267 months apart.<!--

--></ref> explanation for the Greek finding all three lunar mean motions (synodic, anomalistic, draconitic) to a precision of about one part in a million or better. Chinese historical records of solar eclipses date back over 3,000 years and have been used to measure changes in the Earth's rate of spin.<ref>{{cite web
 |url         = http://www.bibalex.org/eclipse2006/HistoricalObservationsofSolarEclipses.htm
 |title       = Solar Eclipses in History and Mythology
 |publisher   = Bibliotheca Alexandrina
 |access-date  = 2007-05-02
 }}</ref>

The first person to give scientific explanation on eclipses was [[Anaxagoras]] [c500BC - 428BC].<ref>{{Citation |last=Curd |first=Patricia |title=Anaxagoras |date=2019 |url=https://plato.stanford.edu/archives/win2019/entries/anaxagoras/ |encyclopedia=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |access-date=2023-08-18 |edition=Winter 2019 |publisher=Metaphysics Research Lab, Stanford University}}</ref> Anaxagoras stated that the Moon shines by  reflected light from the Sun.<ref>{{Cite web |title=Anaxagoras - Biography |url=https://mathshistory.st-andrews.ac.uk/Biographies/Anaxagoras/ |access-date=2023-08-18 |website=Maths History |language=en}}</ref>

In 5th century AD, solar and lunar eclipses were scientifically explained by [[Aryabhata]], in his treatise ''[[Aryabhatiya]].''<ref>{{Cite web|title=Aryabhata {{!}} Achievements, Biography, & Facts {{!}} Britannica|url=https://www.britannica.com/biography/Aryabhata-I|access-date=2021-12-25|website=www.britannica.com|language=en}}</ref> Aryabhata states that the Moon and planets shine by reflected sunlight and explains eclipses in terms of shadows cast by and falling on Earth. Aryabhata provides the computation and the size of the eclipsed part during an eclipse. Indian computations were very accurate that 18th-century French scientist [[Guillaume Le Gentil]], during a visit to Pondicherry, India, found the Indian computations of the duration of the [[lunar eclipse]] of 30 August 1765 to be short by only 41 seconds, whereas Le Gentil's charts were long by 68 seconds.

By the 1600s, European astronomers were publishing books with diagrams explaining how lunar and solar eclipses occurred.<ref>{{cite book|last=Girault|first=Simon|title=Globe dv monde contenant un bref traite du ciel & de la terra|date=1592|location=Langres, France|page=Fol. 8V}}</ref><ref>{{cite book|last=Hevelius|first=Johannes|title=Observatio Eclipseos Solaris Gedani|date=1652|location=Danzig, Poland}}</ref> In order to disseminate this information to a broader audience and decrease fear of the consequences of eclipses, booksellers printed broadsides explaining the event either using the science or via astrology.<ref>{{cite book|last1=Stephanson|first1=Bruce |last2=Bolt|first2=Marvin |last3=Friedman|first3=Anna Felicity |title=The Universe Unveiled: Instruments and Images through History|date=2000|publisher=Cambridge University Press|location=Cambridge, UK|isbn=978-0521791434|pages=32–33}}</ref>

=== Eclipses in mythology and religion ===
{{main article|Eclipses in mythology and culture}}
The American author [[Gene Weingarten]] described the tension between belief and eclipses thus: "I am a devout atheist but can't explain why the moon is exactly the right size, and gets positioned so precisely between the Earth and the sun, that total solar eclipses are perfect. It bothers me."<ref>Gene Weingarten, '[https://www.washingtonpost.com/wp-dyn/content/article/2009/02/27/AR2009022701536.html Me, in a Nutshell]', ''Washington Post'' (USA), 8 March 2009, Page W32 (accessed 9 March 2009).</ref>

The Graeco-Roman historian [[Cassius Dio]], writing between AD 211–229, relates the anecdote that Emperor [[Claudius]] considered it necessary to prevent disturbance among the Roman population by publishing a prediction for a solar eclipse which would fall on his birthday anniversary [1 August in the year AD 45]. In this context, Cassius Dio provides a detailed explanation of solar and lunar eclipses.<ref>{{cite web | url=https://lexundria.com/dio/60.26/cy | title=Cassius Dio, Roman History 60.26 }}</ref>

Typically in mythology, eclipses were understood to be one variation or another of a spiritual battle between the sun and evil forces or spirits of darkness.<ref>{{Cite book|last1=Littmann|first1=Mark|url=https://books.google.com/books?id=UOnH01tv078C&dq=totality+eclipses+of+the+sun&pg=PR7|title=Totality: Eclipses of the Sun|last2=Espenak|first2=Fred|last3=Willcox|first3=Ken|date=2008-07-17|publisher=OUP Oxford|isbn=978-0-19-157994-3|language=en}}</ref> More specifically, in [[Norse mythology]], it is believed that there is a wolf by the name of [[Fenrir]] that is in constant pursuit of the Sun, and eclipses are thought to occur when the wolf successfully devours the divine Sun.<ref>{{Cite book|last=Lindow|first=John|url=https://books.google.com/books?id=jME8hD2UO4QC&dq=norse+mythology+a+guide+to+gods&pg=PR5|title=Norse Mythology: A Guide to Gods, Heroes, Rituals, and Beliefs|date=2002-10-17|publisher=Oxford University Press|isbn=978-0-19-983969-8|language=en}}</ref>{{Failed verification|date=April 2024}} Other Norse tribes believed that there are two wolves by the names of [[Sköll]] and Hati that are in pursuit of the Sun and the Moon, known by the names of Sol and Mani, and these tribes believed that an eclipse occurs when one of the wolves successfully eats either the Sun or the Moon.<ref>{{Cite book|last=Morrison|first=Jessica|url=https://books.google.com/books?id=cbq2DwAAQBAJ&dq=wolf&pg=PA4|title=Eclipses|date=2017-08-01|publisher=Weigl Publishers|isbn=978-1-4896-5814-2|language=en}}</ref>

In most types of mythologies and certain religions, eclipses were seen as a sign that the gods were angry and that danger was soon to come, so people often altered their actions in an effort to dissuade the gods from unleashing their wrath. In the [[Hinduism|Hindu]] religion, for example, people often sing religious hymns for protection from the evil spirits of the eclipse, and many people of the Hindu religion refuse to eat during an eclipse to avoid the effects of the evil spirits.<ref name=":0">{{Cite journal|last1=Musharraf|first1=Muhammad Nabeel|last2=Dars|first2=Dr Basheer Ahmed|title=Eclipses, Mythology, and Islam|date=2021-09-15|url=https://www.alduhaa.com/index.php/al-duhaa/article/view/77|journal=Al-Duhaa|language=en-US|volume=2|issue=02|pages=01–16|doi=10.51665/al-duhaa.002.02.0077|issn=2710-0812|doi-access=free}}</ref> Hindu people living in India will also wash off in the [[Ganges|Ganges River]], which is believed to be spiritually cleansing, directly following an eclipse to clean themselves of the evil spirits.<ref name=":0" /> In early [[Judaism]] and [[Christianity]], eclipses were viewed as signs from God, and some eclipses were seen as a display of God's greatness or even signs of cycles of life and death.<ref name=":0" /> However, more ominous eclipses such as a blood moon were believed to be a divine sign that God would soon destroy their enemies.<ref name=":0" />

==Other planets and dwarf planets==

===Gas giants===
{{see also|Solar eclipses on Jupiter|Solar eclipses on Saturn|Solar eclipses on Uranus|Solar eclipses on Neptune}}
[[Image:JupiterandIo.jpg|thumb|right|A picture of [[Jupiter]] and its moon [[Io (moon)|Io]] taken by [[Hubble Space Telescope|Hubble]]. The black spot is Io's shadow.]]
[[Image:Saturn eclipse.jpg|250px|right|thumb|[[Saturn]] occults the Sun as seen from the ''[[Cassini–Huygens]]'' space probe]]
The [[gas giant]] planets have many moons and thus frequently display eclipses. The most striking involve [[Jupiter]], which has four large moons and a low [[axial tilt]], making eclipses more frequent as these bodies pass through the shadow of the larger planet. Transits occur with equal frequency. It is common to see the larger moons casting circular shadows upon Jupiter's cloudtops.

The eclipses of the [[Galilean moon]]s by Jupiter became accurately predictable once their orbital elements were known. During the 1670s, it was discovered that these events were occurring about 17 minutes later than expected when Jupiter was on the far side of the Sun. [[Ole Rømer]] deduced that the delay was caused by the time needed for light to travel from Jupiter to the Earth. This was used to produce the first estimate of the [[speed of light]].<ref>{{cite web
 |url         = http://www.mathpages.com/home/kmath203/kmath203.htm
 |title       = Roemer's Hypothesis
 |publisher   = MathPages
 |access-date  = 2007-01-12
 |url-status     = live
 |archive-url  = http://archive.wikiwix.com/cache/20110224015233/http://www.mathpages.com/home/kmath203/kmath203.htm
 |archive-date = 2011-02-24
}}</ref>

The timing of the Jovian satellite eclipses was also used to calculate an observer's [[longitude]] upon the Earth. By knowing the expected time when an eclipse would be observed at a standard longitude (such as [[Greenwich]]), the time difference could be computed by accurately observing the local time of the eclipse. The time difference gives the longitude of the observer because every hour of difference corresponded to 15° around the Earth's equator. This technique was used, for example, by [[Giovanni Domenico Cassini|Giovanni D. Cassini]] in 1679 to re-map [[France]].<ref>{{cite journal
 |last        = Cassini
 |first       = Giovanni D.
 |author-link  = Giovanni Domenico Cassini
 |title       = Monsieur Cassini His New and Exact Tables for the Eclipses of the First Satellite of Jupiter, Reduced to the Julian Stile, and Meridian of London
 |journal     = [[Philosophical Transactions of the Royal Society]]
 |date        = 1694
 |volume      = 18
 |issue       = 207–214
 |pages       = 237–256
 |doi         = 10.1098/rstl.1694.0048
 |jstor       = 102468
 |doi-access= free
 |bibcode = 1694RSPT...18..237C
 }}</ref>

On the other three [[gas giant]]s ([[Saturn]], [[Uranus]] and [[Neptune]]) eclipses only occur at certain periods during the planet's orbit, due to their higher [[inclination]] between the orbits of the moon and the [[orbital plane (astronomy)|orbital plane]] of the planet. The moon [[Titan (moon)|Titan]], for example, has an orbital plane tilted about 1.6° to Saturn's equatorial plane. But Saturn has an axial tilt of nearly 27°. The orbital plane of Titan only crosses the line of sight to the Sun at two points along Saturn's orbit. As the orbital period of Saturn is 29.7&nbsp;years, an eclipse is only possible about every 15 years.

===Mars===
{{main|Transit of Phobos from Mars}}
[[Image:PIA05553.gif|right|thumbnail|[[Transit of Phobos from Mars]], as seen by the Mars ''[[Opportunity (rover)|Opportunity rover]]'' (10 March 2004).]]
On [[Mars]], only partial solar eclipses ([[Transit of Phobos from Mars|transits]]) are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun's disc as seen from the surface of the planet. Eclipses of the moons by Mars are not only possible, but commonplace, with hundreds occurring each Earth year. There are also rare occasions when Deimos is eclipsed by Phobos.<ref>{{cite book 
|first=Norman |last=Davidson |date=1985 
|title=Astronomy and the Imagination: A New Approach to Man's Experience of the Stars 
|publisher=Routledge 
|isbn=978-0-7102-0371-7 }}</ref> Martian eclipses have been photographed from both the surface of Mars and from orbit.

===Pluto===
{{main|Solar eclipses on Pluto}}
[[Pluto]], with its proportionately largest moon [[Charon (moon)|Charon]], is also the site of many eclipses. A series of such mutual eclipses occurred between 1985 and 1990.<ref>{{cite journal 
|last=Buie |first=M. W. |author2=Polk, K. S. 
|title=Polarization of the Pluto-Charon System During a Satellite Eclipse 
|journal=Bulletin of the American Astronomical Society 
|date=1988 |volume=20 |page=806 
|bibcode=1988BAAS...20..806B }}</ref> These daily events led to the first accurate measurements of the physical parameters of both objects.<ref>{{cite journal |last=Tholen |first=D. J. |author2=Buie, M. W. |author3=Binzel, R. P. |author4=Frueh, M. L. |title=Improved Orbital and Physical Parameters for the Pluto-Charon System |journal=Science |date=1987 |volume=237 |issue=4814 |pages=512&ndash;514 |doi=10.1126/science.237.4814.512 |pmid=17730324 |bibcode=1987Sci...237..512T |s2cid=33536340 }}</ref>

===Mercury and Venus===
Eclipses are impossible on [[Mercury (planet)|Mercury]] and [[Venus]], which have no moons. However, as seen from the Earth, both have been observed to [[Astronomical transit|transit]] across the face of the Sun. [[Transit of Venus|Transits of Venus]] occur in pairs separated by an interval of eight years, but each pair of events happen less than once a century.<ref>{{cite web |last=Espenak |first=Fred |date=May 29, 2007 |url=http://sunearth.gsfc.nasa.gov/eclipse/transit/transit.html |title=Planetary Transits Across the Sun |publisher=NASA |access-date=2008-03-11 |url-status=dead |archive-url=https://web.archive.org/web/20080311033452/http://sunearth.gsfc.nasa.gov/eclipse/transit/transit.html |archive-date=March 11, 2008 }}</ref> According to NASA, the next pair of Venus transits will occur on December 10, 2117, and December 8, 2125. [[Transit of Mercury|Transits of Mercury]] are much more common, occurring 13 times each century, on average.<ref>{{Cite web|url=https://eclipse2017.nasa.gov/when-will-next-transits-mercury-and-venus-occur-during-total-solar-eclipse|title=When will the next transits of Mercury and Venus occur during a total solar eclipse? {{!}} Total Solar Eclipse 2017|website=eclipse2017.nasa.gov|language=en|access-date=2017-09-25|url-status=dead|archive-url=https://web.archive.org/web/20170918151937/https://eclipse2017.nasa.gov/when-will-next-transits-mercury-and-venus-occur-during-total-solar-eclipse|archive-date=2017-09-18}}</ref>

==Eclipsing binaries==
A [[binary star]] system consists of two stars that orbit around their common [[centre of mass]]. The movements of both stars lie on a common [[orbital plane]] in space. When this plane is very closely aligned with the location of an observer, the stars can be seen to pass in front of each other. The result is a type of extrinsic [[variable star]] system called an [[eclipsing binary]].

The maximum [[luminosity]] of an eclipsing binary system is equal to the sum of the luminosity contributions from the individual stars. When one star passes in front of the other, the luminosity of the system is seen to decrease. The luminosity returns to normal once the two stars are no longer in alignment.<ref>{{cite web
 |last=Bruton 
 |first=Dan 
 |url=http://www.physics.sfasu.edu/astro/ebstar/ebstar.html 
 |title=Eclipsing binary stars 
 |publisher=Midnightkite Solutions 
 |access-date=2007-05-01 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20070414144827/http://www.physics.sfasu.edu/astro/ebstar/ebstar.html 
 |archive-date=2007-04-14 
}}</ref>

The first eclipsing binary star system to be discovered was [[Algol]], a star system in the constellation [[Perseus (constellation)|Perseus]]. Normally this star system has a [[visual magnitude]] of 2.1. However, every 2.867 days the magnitude decreases to 3.4 for more than nine hours. This is caused by the passage of the dimmer member of the pair in front of the brighter star.<ref>{{cite web 
|last=Price 
|first=Aaron 
|date=January 1999 
|url=http://www.aavso.org/vstar/vsots/0199.shtml 
|title=Variable Star Of The Month: Beta Persei (Algol) 
|publisher=AAVSO 
|access-date=2007-05-01 
|archive-url=https://web.archive.org/web/20070405003853/http://www.aavso.org/vstar/vsots/0199.shtml <!-- Bot retrieved archive --> |archive-date=2007-04-05 }}</ref> The concept that an eclipsing body caused these luminosity variations was introduced by [[John Goodricke]] in 1783.<ref>{{cite journal 
|last1=Goodricke 
|first1=John 
|author-link=John Goodricke 
|last2=Englefield 
|first2=H. C. 
|title=Observations of a New Variable Star 
|journal=Philosophical Transactions of the Royal Society of London 
|date=1785 
|volume=75 
|pages=153–164 
|bibcode=1785RSPT...75..153G 
|doi=10.1098/rstl.1785.0009 |s2cid=186208561 
|doi-access= 
}}</ref>

== Types ==
'''Sun – Moon – Earth:''' '''[[Solar eclipse]]''' | [[annular eclipse]] | [[hybrid eclipse]] | [[Solar eclipse|partial eclipse]]

'''Sun – Earth – Moon:''' '''[[Lunar eclipse]]''' | [[penumbral eclipse]] | [[partial lunar eclipse]] | [[central lunar eclipse]]

'''Sun – Phobos – Mars: [[Transit of Phobos from Mars]]''' | [[Solar eclipses on Mars]]

'''Sun – Deimos – Mars: [[Transit of Deimos from Mars]]''' | [[Solar eclipses on Mars]]

'''Other types:''' [[Solar eclipses on Jupiter]] | [[Solar eclipses on Saturn]] | [[Solar eclipses on Uranus]] | [[Solar eclipses on Neptune]] | [[Solar eclipses on Pluto]]

==See also==
* [[List of solar eclipses in the 21st century]]
* [[Mursili's eclipse]]
* [[Transit of Venus]]

==References==
{{Reflist}}

== External links ==
{{commons}}
{{Wikiquote}}
{{Wiktionary|eclipse}}
* {{YouTube|id=VwklVTy03Wc|title=Phobos Eclipsing Mars Observed by Curiosity Rover}}
* [https://webspace.science.uu.nl/~gent0113/eclipse/eclipsecycles.htm A Catalogue of Eclipse Cycles]
* [http://moonblink.info/Eclipse/lists/search Search 5,000 years of eclipses]
* [https://science.nasa.gov/eclipses/ NASA eclipse home page]
* [http://www.eclipses.info International Astronomical Union's Working Group on Solar Eclipses]
* [http://xjubier.free.fr/en/site_pages/SolarEclipsesGoogleMaps.html Interactive eclipse maps site]
* [https://demos.smu.ca/demos/astronomy/200-eclipses Classroom demonstration of how an eclipse occurs]

;Image galleries
*[https://twanight.org/special/eclipses/ The World at Night Eclipse Gallery]
* [http://www.perseus.gr/Astro-Eclipses.htm Solar and Lunar Eclipse Image Gallery]
* [http://www.williams.edu/astronomy/eclipse Williams College eclipse collection of images]

{{lunar eclipses}}
{{Solar eclipses}}
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[[Category:Eclipses| ]]
[[Category:Astrological aspects]]
[[Category:Astronomical events]]
[[Category:Earth phenomena]]
[[Category:Concepts in astronomy]]