Solar eclipse

Solar eclipse

Overview
As seen from the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, a solar eclipse
Eclipse
An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...

occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 passes between the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

, when the Sun and the Moon are in conjunction as seen from Earth. At least two, and up to five, solar eclipses occur each year; no more than two can be total eclipses. Total solar eclipses are nevertheless rare at any particular location because totality exists only along a narrow path on the Earth's surface traced by the Moon's umbra
Umbra
The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.These names are most often used to refer to the shadows cast by celestial bodies....

.

Some people, sometimes referred to as "eclipse chasers" or "umbraphiles", will travel to remote locations to observe or witness a predicted central solar eclipse (see Types below).
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Timeline

781 BC   The first historic solar eclipse is recorded in China.

763 BC   Assyrians record a solar eclipse that is later used to fix the chronology of Mesopotamian history.

585 BC   A solar eclipse occurs, as predicted by Greek philosopher and scientist Thales, while Alyattes is battling Cyaxares in the Battle of the Eclipse, leading to a truce. This is one of the cardinal dates from which other dates can be calculated.

1831   Nat Turner sees a solar eclipse, which he believes is a sign from God. Eight days later he and 70 other slaves kill approximately 55 whites in Southampton County, Virginia.

1919   Einstein's theory of general relativity is tested (later confirmed) by Arthur Eddington's observation of a total solar eclipse in Principe and by Andrew Crommelin in Sobral, Ceará, Brazil.

1999   A total Solar eclipse (Solar eclipse of August 11, 1999)

 
Encyclopedia
As seen from the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, a solar eclipse
Eclipse
An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...

occurs when the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 passes between the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...

, when the Sun and the Moon are in conjunction as seen from Earth. At least two, and up to five, solar eclipses occur each year; no more than two can be total eclipses. Total solar eclipses are nevertheless rare at any particular location because totality exists only along a narrow path on the Earth's surface traced by the Moon's umbra
Umbra
The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.These names are most often used to refer to the shadows cast by celestial bodies....

.

Some people, sometimes referred to as "eclipse chasers" or "umbraphiles", will travel to remote locations to observe or witness a predicted central solar eclipse (see Types below). The solar eclipse of August 11, 1999, in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 helped to increase public awareness of the phenomenon, which apparently led to an unusually large number of journeys made specifically to witness the annular solar eclipse of October 3, 2005, and of March 29, 2006.

The last total solar eclipse was the solar eclipse of July 11, 2010
Solar eclipse of July 11, 2010
The total solar eclipse of July 11, 2010, occurred over the southern Pacific Ocean. -Visibility:The eclipse was one of the most remote in recorded history...

; the next will be the solar eclipse of November 13, 2012
Solar eclipse of November 13, 2012
A total solar eclipse will take place on 13-14 November, 2012, with a magnitude of 1.0500. - Details :For this eclipse totality will be visible from northern Australia and the southern Pacific Ocean. The most populous city to experience totality will be Cairns, which will experience 2 minutes of...

. The recent solar eclipse of June 1, 2011
Solar eclipse of June 1, 2011
A partial solar eclipse occurred on June 1, 2011. This eclipse is the second of four partial solar eclipses in 2011, with the others occurring on January 4, 2011, July 1, 2011, and November 25, 2011....

 and the Solar eclipse of July 1, 2011
Solar eclipse of July 1, 2011
A partial solar eclipse occurred on July 1, 2011. This is the first solar eclipse of saros series 156, only visible as a partial solar eclipse in a small area south of South Africa and north of Antarctica. At greatest eclipse, the magnitude is just 0.097. It is the first new saros series to begin...

, were partial eclipses (see Types below); the next partial eclipse will occur on November 25, 2011
Solar eclipse of November 25, 2011
A partial solar eclipse occurred on November 25, 2011. This eclipse was visible across Antarctica in its summer 24 hour day sunlight, and New Zealand near sunset with less than 20% of the sun obscured...

.

A total solar eclipse is a natural phenomenon
Natural phenomenon
A natural phenomenon is a non-artificial event in the physical sense, and therefore not produced by humans, although it may affect humans . Common examples of natural phenomena include volcanic eruptions, weather, decay, gravity and erosion...

. Nevertheless, in ancient times, and in some cultures today, solar eclipses have been attributed to supernatural
Supernatural
The supernatural or is that which is not subject to the laws of nature, or more figuratively, that which is said to exist above and beyond nature...

 causes or regarded as bad omen
Omen
An omen is a phenomenon that is believed to foretell the future, often signifying the advent of change...

s. A total solar eclipse can be frightening to people who are unaware of their astronomical
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 explanation, as the Sun seems to disappear during the day and the sky darkens in a matter of minutes.

Types



There are four types of solar eclipses:
  • A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona
    Corona
    A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph...

     to be visible. During any one eclipse, totality occurs at best only in a narrow track on the surface of the Earth.
  • An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus
    Annulus (mathematics)
    In mathematics, an annulus is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. Or, it is the area between two concentric circles...

    , surrounding the outline of the Moon.
  • A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At some points on the surface of the Earth it appears as a total eclipse, whereas at others it appears as annular. Hybrid eclipses are comparatively rare.
  • A partial eclipse occurs when the Sun and Moon are not exactly in line and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can only be seen as a partial eclipse, because the umbra
    Umbra
    The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.These names are most often used to refer to the shadows cast by celestial bodies....

     passes above the Earth's polar regions and never intersects the Earth's surface.

The Sun's distance from the Earth is about 400 times the Moon's distance, and the Sun's diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

 is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure.
The Moon's orbit around the Earth is an ellipse
Ellipse
In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is orthogonal to the cone's axis...

, as is the Earth's orbit around the Sun; the apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse that occurs when the Moon is near its closest distance to the Earth (i.e., near its perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

) can be a total eclipse because the Moon will appear to be large enough to cover completely the Sun's bright disk, or photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...

; a total eclipse has a magnitude greater than 1. Conversely, an eclipse that occurs when the Moon is near its farthest distance from the Earth (i.e., near its apogee) can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Slightly more solar eclipses are annular than total because, on average, the Moon lies too far from Earth to cover the Sun completely. A hybrid eclipse occurs when the magnitude of an eclipse changes during the event from smaller than one to larger than one—or vice versa—so the eclipse appears to be total at some locations on Earth and annular at other locations.

Because the Earth's orbit around the Sun is also elliptical, the Earth's distance from the Sun similarly varies throughout the year. This affects the apparent sizes of the Sun and Moon in the same way, but not so much as the Moon's varying distance from the Earth. When the Earth approaches its farthest distance from the Sun in July, a total eclipse is somewhat more likely, whereas conditions favour an annular eclipse when the Earth approaches its closest distance to the Sun in January.

Terminology for central eclipse


Central eclipse is often used as a generic term for a total, annular, or hybrid eclipse. This is, however, not completely correct: the definition of a central eclipse is an eclipse during which the central line of the umbra touches the Earth's surface. It is possible, though extremely rare, that part of the umbra intersects with Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse. The next non-central solar eclipse will be on April 29, 2014. This will be an annular eclipse. The next non-central total solar eclipse will be on April 9, 2043.

The phases observed during a total eclipse are called:
  • First Contact—when the moon's limb first becomes visible on the solar disk. Some also name individual phases between First and Second Contact e.g. Pac-Man phase.
  • Second Contact—starting with Baily's Beads {caused by light shining through valleys on the moon's surface} and the Diamond Ring. Almost the entire disk is covered.
  • Totality—the limb of the moon obscuring the entire disk of the sun and only the corona visible
  • Third Contact—when the first bright light becomes visible and the shadow is moving away from the observer. Again a Diamond Ring may be observed

Geometry


The diagram to the right shows the alignment of the Sun, Moon and Earth during a solar eclipse. The dark gray region below the Moon is the umbra
Umbra
The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.These names are most often used to refer to the shadows cast by celestial bodies....

, where the Sun is completely obscured by the Moon. The small area where the umbra touches the Earth's surface is where a total eclipse can be seen. The larger light gray area is the penumbra, in which only a partial and annular eclipses can be seen.

The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...

). Because of this, at the time of a new moon, the Moon will usually pass above or below the Sun. A solar eclipse can occur only when the new moon occurs close to one of the points (known as node
Orbital node
An orbital node is one of the two points where an orbit crosses a plane of reference to which it is inclined. An orbit which is contained in the plane of reference has no nodes.-Planes of reference:...

s) where the Moon's orbit crosses the ecliptic.

As noted above, the Moon's orbit is also elliptical
Ellipse
In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is orthogonal to the cone's axis...

. The Moon's distance from the Earth can vary by about 6% from its average value. Therefore, the Moon's apparent size varies with its distance from the Earth, and it is this effect that leads to the difference between total and annular eclipses. The distance of the Earth from the Sun also varies during the year, but this is a smaller effect. On average, the Moon appears to be slightly smaller than the Sun, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to the Earth than average (near its perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

) that a total eclipse occurs.
| Moon | Sun
At perigee
(nearest)
At apogee
(farthest)
At perihelion
(nearest)
At aphelion
(farthest)
Mean radius, r 1737.1 kilometres (1,079.4 mi) 696000 kilometres (432,475.4 mi)
Distance, d 363104 km (225,622.9 mi) 405696 km (252,088.4 mi) 147098070 km (91,402,730.3 mi) 152097700 km (94,509,364.1 mi)
Angular diameter,
2 × arctan(r / d)
32' 54"
(0.5482°)
29' 26"
(0.4907°)
32' 32"
(0.5422°)
31' 28"
(0.5244°)
Apparent size
to scale
Rank in
descending order
1st 4th 2nd 3rd


The Moon orbits the Earth in approximately 27.3 days, relative to a fixed frame of reference. This is known as the sidereal month. However, during one sidereal month, the Earth has revolved part way around the Sun, making the average time between one new moon and the next longer than the sidereal month: it is approximately 29.5 days. This is known as the synodic month, and corresponds to what is commonly called the lunar month
Lunar month
In lunar calendars, a lunar month is the time between two identical syzygies . There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction with the Sun one or two days before that evening...

.

The Moon crosses from south to north of the ecliptic at its ascending node, and vice versa at its descending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion
Retrograde motion
Retrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...

, due to the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.6 years. This means that the time between each passage of the Moon through the ascending node is slightly shorter than the sidereal month. This period is called the draconic month.

Finally, the Moon's perigee is moving forwards in its orbit, and makes a complete circuit in about 9 years. The time between one perigee and the next is known as the anomalistic month.

The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Therefore, the new moon occurs close to the nodes at two periods of the year approximately six months apart, and there will always be at least one solar eclipse during these periods. Sometimes the new moon occurs close enough to a node during two consecutive months. This means that in any given year, there will always be at least two solar eclipses, and there can be as many as five. However, some are visible only as partial eclipses, because the umbra passes above Earth's north or south pole, and others are central only in remote regions of the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 or Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...

.

Eclipses can only occur when the sun is within about 15 to 18 degrees of a node, (10 to 12 degrees for central eclipses). This is referred to as an eclipse limit. In the time it takes for the moon to return to a node (draconic month), the apparent position of the sun has moved about 29 degrees, relative to the nodes. Since the eclipse limit creates a window of opportunity of up to 36 degrees (24 degrees for central eclipses), it is possible for partial (or rarely a partial and a central) eclipses to occur in consecutive months.

Path


During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across the Earth. The Earth is also rotating from west to east, but the umbra always moves faster than any given point on the Earth's surface, so it almost always appears to move in a roughly west-east direction across a map of the Earth (there are some rare exceptions to this which can occur during an eclipse of the midnight sun
Midnight sun
The midnight sun is a natural phenomenon occurring in summer months at latitudes north and nearby to the south of the Arctic Circle, and south and nearby to the north of the Antarctic Circle where the sun remains visible at the local midnight. Given fair weather, the sun is visible for a continuous...

 in Arctic or Antarctic regions, for example on June 10
Solar eclipse of June 10, 2021
An annular solar eclipse will occur on June 10, 2021. This eclipse will be unusual as the path of the total eclipse will move from to the north east, then north, north west, west, south west, south, and finally south east across the Arctic, while most eclipse paths move west to east. This reversal...

 and December 4
Solar eclipse of December 4, 2021
A total solar eclipse will occur on December 4, 2021. This eclipse will be unusual as the path of the total eclipse will move from east to west across Antarctica, while most eclipse paths move from west to east. This reversal is only possible in polar regions....

, 2021).

The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. In the most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be over 250 km wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse can usually be seen over a much larger area of the Earth.

Occurrence and cycles


Total solar eclipses are rare events. Although they occur somewhere on Earth every 18 months on average, it has been estimated that they recur at any given place only once every 370 years, on average. The total eclipse only lasts for a few minutes at that location, as the Moon's umbra moves eastward at over 1700 km/h. Totality can never last more than 7 min 31 s, and is usually much shorter: during each millennium
Millennium
A millennium is a period of time equal to one thousand years —from the Latin phrase , thousand, and , year—often but not necessarily related numerically to a particular dating system....

 there are typically fewer than 10 total solar eclipses exceeding 7 minutes. The last time this happened was June 30, 1973
Solar eclipse of June 30, 1973
A total solar eclipse occurred on June 30, 1973. - Observations :This eclipse was observed by a group of scientists from the Los Alamos National Laboratory using two airplanes to extend the apparent time of totality by flying along the eclipse path in the same direction as the Moon's shadow as it...

 (7 min 3 sec). Observers aboard a Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...

 aircraft were able to stretch totality to about 74 minutes by flying along the path of the Moon's umbra. The next eclipse exceeding seven minutes in duration will not occur until June 25, 2150
Solar eclipse of June 25, 2150
A total solar eclipse will occur on June 25, 2150. - References :* * *...

. The longest total solar eclipse during the 8,000 year period from 3000 BC to 5000 AD will occur on July 16, 2186
Solar eclipse of July 16, 2186
There will be a total solar eclipse on July 16, 2186, passing over the southern Galápagos Islands , northern South America, specifically, the northern tip of Ecuador , central Colombia There will be a total solar eclipse on July 16, 2186, passing over the southern Galápagos Islands (with a maximum...

, when totality will last 7 min 29 s. For comparison, the longest eclipse of the 20th century occurred on June 20, 1955
Solar eclipse of June 20, 1955
A total solar eclipse occurred on June 20, 1955. With a maximum duration of 7 minutes 8 seconds, this is the longest solar eclipse of saros series 136, as well as the longest total solar eclipse since the 11th century...

 and lasted 7 min 8 sec.

If the date and time of any solar eclipse are known, it is possible to predict other eclipses using eclipse cycle
Eclipse cycle
Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series.- Eclipse conditions :...

s. Two such cycles are the saros
Saros cycle
The saros is a period of 223 synodic months , that can be used to predict eclipses of the Sun and Moon. One saros after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle...

 and the inex
Inex
The inex is an eclipse cycle of 10,571.95 days . The cycle was first described by Crommelin in 1901, but was named by George van den Bergh who studied it half a century later...

. The saros is probably the best known and one of the most accurate eclipse cycles. The inex cycle is itself a poor cycle, but it is very convenient in the classification of eclipse cycles. After a saros finishes, a new saros series begins one inex later, hence its name: in-ex. A saros lasts 6,585.3 days (a little over 18 years), which means that after this period a practically identical eclipse will occur. The most notable difference will be a shift of 120° in longitude (due to the 0.3 days) and a little in latitude. A saros series always starts with a partial eclipse near one of Earth's polar regions, then shifts over the globe through a series of annular or total eclipses, and ends at the opposite polar region. A saros series lasts 1226 to 1550 years and 69 to 87 eclipses, with about 40 to 60 central.

Frequency per year


Solar eclipses can occur 2 to 5 times per year, at least once per eclipse season
Eclipse season
Eclipse seasons are the only times during a year eclipses can occur, due to the 5° inclination of the moon's orbit. Each season lasts for approximately 33 days and repeats just short of six months, thus there are always two full eclipse seasons each year. 2 to 3 eclipses always occur each eclipse...

. Since the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

 was instituted in 1582, years that have had five solar eclipses were 1693, 1758, 1805, 1823, 1870, and 1935. The next occurrence will be 2206.
The 5 solar eclipses of 1935
January 5
Solar eclipse of January 5, 1935
A partial solar eclipse occurred on January 5, 1935. It was the last eclipse of solar saros 111 with the moon's penumbra touching the earth for just 10 minutes. - External links :* http://eclipse.gsfc.nasa.gov/SEplot/SEplot1901/SE1935Jan05P.GIF...

February 3
Solar eclipse of February 3, 1935
A partial solar eclipse occurred on February 3, 1935.- External links :* http://eclipse.gsfc.nasa.gov/SEplot/SEplot1901/SE1935Feb03P.GIF...

June 30
Solar eclipse of June 30, 1935
A partial solar eclipse occurred on June 30, 1935. - External links :* http://eclipse.gsfc.nasa.gov/SEplot/SEplot1901/SE1935Jun30P.GIF...

July 30
Solar eclipse of July 30, 1935
A partial solar eclipse occurred on July 30, 1935.- External links :* http://eclipse.gsfc.nasa.gov/SEplot/SEplot1901/SE1935Jul30P.GIF...

December 25
Solar eclipse of December 25, 1935
An annular solar eclipse occurred on December 25, 1935. This was the 5th solar eclipse in 1935, the maximum possible. The next time this will occur is 2206.-References:...

Partial
(south)
Partial
(north)
Partial
(north)
Partial
(south)
Annular
(south)

Saros 111

Saros 149

Saros 116

Saros 154

Saros 121

Final totality


Solar eclipses are seen on Earth because of a fortuitous combination of circumstances. Even on Earth, eclipses of the type familiar to people today are a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was too close to the Earth to precisely occlude the Sun as it does during eclipses today; and many millions of years in the future, it will be too far away to do so.

Due to tidal acceleration
Tidal acceleration
Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite , and the primary planet that it orbits . The "acceleration" is usually negative, as it causes a gradual slowing and recession of a satellite in a prograde orbit away from the primary, and a corresponding...

, the orbit of the Moon around the Earth becomes approximately 3.8 cm more distant each year. It is estimated that in 600 million years, the distance from the Earth to the Moon will have increased by 23,500 km, meaning that it will no longer be able to completely cover the Sun's disk. This will be true even when the Moon is at perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

, and the Earth at aphelion.

A complicating factor is that the Sun will increase in size over this timescale. This makes it even more unlikely that the Moon will be able to cause a total eclipse. Therefore, the last total solar eclipse on Earth will occur in slightly less than 600 million years.

Historical eclipses



Historical eclipses are a very valuable resource for historians, in that they allow a few historical events to be dated precisely, from which other dates and a society's calendar may be deduced. Aryabhata
Aryabhata
Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...

 (476–550) concluded the Heliocentric theory in solar eclipse. A solar eclipse of June 15, 763 BC mentioned in an Assyrian
Assyrian people
The Assyrian people are a distinct ethnic group whose origins lie in ancient Mesopotamia...

 text is important for the Chronology of the Ancient Orient. Also known as the eclipse of Bur Sagale, it is the earliest solar eclipse mentioned in historical sources that has been identified successfully. Perhaps the earliest still-unproven claim is that of archaeologist Bruce Masse asserting on the basis of several ancient flood myths
Flood (mythology)
A flood myth or deluge myth is a mythical or religious story of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution...

, which mention a total solar eclipse, he links an eclipse that occurred May 10, 2807 BC with a possible meteor impact
Impact event
An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...

 in the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

. There have been other claims to date earlier eclipses, notably that
Mursili's eclipse
The solar eclipse mentioned in a text dating to the reign of Mursili II could be of great importance for the absolute chronology of the Hittite Empire within the chronology of the Ancient Near East....

 of Mursili II
Mursili II
Mursili II was a king of the Hittite Empire ca. 1321–1295 BC .-Family:Mursili II was the younger son of Suppiluliuma I, one of the most powerful rulers of the Hittite Empire...

 (likely 1312 BC), in Babylonia
Babylonia
Babylonia was an ancient cultural region in central-southern Mesopotamia , with Babylon as its capital. Babylonia emerged as a major power when Hammurabi Babylonia was an ancient cultural region in central-southern Mesopotamia (present-day Iraq), with Babylon as its capital. Babylonia emerged as...

, and also in China, during the Fifth Year (2084 BC) of the regime of Emperor Zhong Kang of Xia dynasty, but these are highly disputed and rely on much supposition.

Herodotus
Herodotus
Herodotus was an ancient Greek historian who was born in Halicarnassus, Caria and lived in the 5th century BC . He has been called the "Father of History", and was the first historian known to collect his materials systematically, test their accuracy to a certain extent and arrange them in a...

 wrote that Thales of Miletus
Thales
Thales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...

 predicted an eclipse which occurred during a war between the Medians
Medes
The MedesThe Medes...

 and the Lydia
Lydia
Lydia was an Iron Age kingdom of western Asia Minor located generally east of ancient Ionia in the modern Turkish provinces of Manisa and inland İzmir. Its population spoke an Anatolian language known as Lydian....

ns. Soldiers on both sides put down their weapons and declared peace as a result of the eclipse. Exactly which eclipse was involved has remained uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BC, probably near the Halys
Halys River
The Kızılırmak , also known as the Halys River , is the longest river in Turkey. It is a source of hydroelectric power and is not used for navigation.- Geography :...

 river in the middle of modern Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

.

An annular eclipse of the Sun occurred at Sardis
Sardis
Sardis or Sardes was an ancient city at the location of modern Sart in Turkey's Manisa Province...

 on February 17, 478 BC, while Xerxes was departing for his expedition against Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, as Herodotus recorded. Hind and Chambers considered this absolute date more than a century ago. Herodotus also reports that another solar eclipse was observed in Sparta
Sparta
Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...

 during the next year, on August 1, 477 BC. The sky suddenly darkened in the middle of the day, well after the battles of Thermopylae
Battle of Thermopylae
The Battle of Thermopylae was fought between an alliance of Greek city-states, led by King Leonidas of Sparta, and the Persian Empire of Xerxes I over the course of three days, during the second Persian invasion of Greece. It took place simultaneously with the naval battle at Artemisium, in August...

 and Salamis
Battle of Salamis
The Battle of Salamis was fought between an Alliance of Greek city-states and the Persian Empire in September 480 BCE, in the straits between the mainland and Salamis, an island in the Saronic Gulf near Athens...

, after the departure of Mardonius
Mardonius
Mardonius was a leading Persian military commander during the Persian Wars with Greece in the early 5th century BC.-Early years:Mardonius was the son of Gobryas, a Persian nobleman who had assisted the Achaemenid prince Darius when he claimed the throne...

 to Thessaly
Thessaly
Thessaly is a traditional geographical region and an administrative region of Greece, comprising most of the ancient region of the same name. Before the Greek Dark Ages, Thessaly was known as Aeolia, and appears thus in Homer's Odyssey....

 at the beginning of the spring of (477 BC) and his second attack on Athens
Athens
Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

, after the return of Cleombrotus to Sparta
Sparta
Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...

. The modern conventional dates are different by a year or two, and that these two eclipse records have been ignored so far. The Chronicle of Ireland recorded a solar eclipse on June 29, AD 512, and a solar eclipse was reported to have taken place during the Battle of Stiklestad
Battle of Stiklestad
The Battle of Stiklestad in 1030 is one of the most famous battles in the history of Norway. In this battle, King Olaf II of Norway was killed. He was later canonized...

 in July, 1030.

In the Indian epic the Mahabharata
Mahabharata
The Mahabharata is one of the two major Sanskrit epics of ancient India and Nepal, the other being the Ramayana. The epic is part of itihasa....

 the incident is related of the thirteenth day when Arjun vows to slay Jayadrath before nightfall, to avenge the death of Abhimanyu at Jayadratha's hands. What may only be described as a solar eclipse brought Jayadrath out to celebrate his surviving the day, only to have the sun reappear and Arjun killed Jayadrath. In the epic astronomers have calculated all possible eclipse pairs matching the above time difference and being visible from Kurukshetra
Kurukshetra
Kurukshetra is a land of historical and religious importance. Historically the land belonged to Punjab now a district in Haryana state of India. It is a holy place and is also known as Dharmakshetra . According to the Puranas, Kurukshetra is named after King Kuru, the ancestor of Kauravas and...

, the battlefield of the Mahabharata
Mahabharata
The Mahabharata is one of the two major Sanskrit epics of ancient India and Nepal, the other being the Ramayana. The epic is part of itihasa....

 war. 3129 BC and 2559 BC appear to be the best candidate for the Mahabharata war.

Attempts have been made to establish the exact date of Good Friday
Good Friday
Good Friday , is a religious holiday observed primarily by Christians commemorating the crucifixion of Jesus Christ and his death at Calvary. The holiday is observed during Holy Week as part of the Paschal Triduum on the Friday preceding Easter Sunday, and may coincide with the Jewish observance of...

 by means of solar eclipses, but this research has not yielded conclusive results. Research has manifested the inability of total solar eclipses to serve as explanations for the recorded Good Friday
Good Friday
Good Friday , is a religious holiday observed primarily by Christians commemorating the crucifixion of Jesus Christ and his death at Calvary. The holiday is observed during Holy Week as part of the Paschal Triduum on the Friday preceding Easter Sunday, and may coincide with the Jewish observance of...

 features of the crucifixion eclipse
Crucifixion eclipse
According to the Christian synoptic gospels, on the day Jesus Christ was crucified, darkness covered the land for hours, an event which later came to be referred to as the "crucifixion eclipse". Although medieval writers treated the darkness as a miracle, various Christian historians have...

. (Good Friday is recorded as being at Passover
Passover
Passover is a Jewish holiday and festival. It commemorates the story of the Exodus, in which the ancient Israelites were freed from slavery in Egypt...

, which is also recorded as being at or near the time of a full moon.)

The ancient Chinese astronomer Shi Shen
Shi Shen
Shi Shen was a Chinese astronomer and contemporary of Gan De born in the State of Wei, also known as the Master Shi Shen .-Observations:...

 (fl. fourth century BC) was aware of the relation of the moon in a solar eclipse, as he provided instructions in his writing to predict them by using the relative positions of the moon and sun. The "radiating influence" theory for a solar eclipse (i.e., the moon's light was merely light reflected from the sun) was existent in Chinese thought from about the sixth century BC (in the Zhi Ran of Zhi Ni Zi), and opposed by the Chinese philosopher Wang Chong
Wang Chong
Wang Chong , courtesy name Zhongren , was a Chinese philosopher active during the Han Dynasty. He developed a rational, secular, naturalistic and mechanistic account of the world and of human beings and gave a materialistic explanation of the origin of the universe. His main work was the Lùnhéng...

 (AD 27–97), who made clear in his writing that this theory was nothing new. This can be said of Jing Fang's writing in the 1st century BC, which stated:
The ancient Greeks had known this as well, since it was Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

 of Elea
Elea
Elea may refer to:* Elea, ancient name of an Italian Greek colony, now known as Velia**Eleatics, school of pre-Socratic philosophers at Elea* Elea, Kyrenia, a settlement of Cyprus in Kyrenia District...

, around 475 BC, who supported the theory of the moon shining because of reflected light, and was accepted in the time of Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 as well. The Chinese astronomer and inventor Zhang Heng
Zhang Heng
Zhang Heng was a Chinese astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar from Nanyang, Henan. He lived during the Eastern Han Dynasty of China. He was educated in the capital cities of Luoyang and Chang'an, and began his career as a...

 (AD 78–139) wrote of both solar and lunar eclipse
Lunar eclipse
A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...

s in the publication of Ling Xian in AD 120, supporting the radiating influence theory that Wang Chong had opposed (Wade-Giles
Wade-Giles
Wade–Giles , sometimes abbreviated Wade, is a romanization system for the Mandarin Chinese language. It developed from a system produced by Thomas Wade during the mid-19th century , and was given completed form with Herbert Giles' Chinese–English dictionary of 1892.Wade–Giles was the most...

):
The later Chinese scientist and statesman Shen Kuo
Shen Kuo
Shen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...

 (AD 1031–1095) also wrote of eclipses, and his reasoning for why the celestial bodies were round and spherical instead of flat (Wade-Giles
Wade-Giles
Wade–Giles , sometimes abbreviated Wade, is a romanization system for the Mandarin Chinese language. It developed from a system produced by Thomas Wade during the mid-19th century , and was given completed form with Herbert Giles' Chinese–English dictionary of 1892.Wade–Giles was the most...

 spelling):
Eclipses have been interpreted as omens, or portents, especially when associated with battles. On 22 January 1879
Solar eclipse of January 22, 1879
An annular solar eclipse occurred on January 22, 1879. The path of totality crossed southern Africa.- Observations :On 22 January 1879 a British battalion was massacred by Zulu warriors during the Zulu War in South Africa. At 2:29 PM there was a solar eclipse...

 Zulu warriors successfully defeated a British battalion in the fight against imperialism during the Zulu War in South Africa. At 2:29 PM there was a solar eclipse. The conflict was named the Battle of Isandlwana
Battle of Isandlwana
The Battle of Isandlwana on 22 January 1879 was the first major encounter in the Anglo-Zulu War between the British Empire and the Zulu Kingdom...

, the Zulu name for the battle translates as "the day of the dead moon".

Viewing


Looking directly at the photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...

 of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in permanent impairment of vision, up to and including blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.

Under normal conditions, the Sun is so bright that it is difficult to stare at it directly, so there is no tendency to look at it in a way that might damage the eye. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Unfortunately, looking at the Sun during an eclipse is just as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during a total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage in a fraction of a second.

Glancing at the Sun with all or most of its disk visible is unlikely to result in permanent harm, as the pupil will close down and reduce the brightness of the whole scene. If the eclipse is near total, the low average amount of light causes the pupil to open. Unfortunately the remaining parts of the Sun are still just as bright, so they are now brighter on the retina than when looking at a full Sun. As the eye has a small fovea, for detailed viewing, the tendency will be to track the image on to this best part of the retina, causing damage.

Partial and annular eclipses


Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods, if eye damage is to be avoided. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Sunglasses do not make viewing the sun safe. Only properly designed and certified solar filters should be used for direct viewing of the Sun's disk. Especially, self-made filters using common objects such as a floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...

 removed from its case, a Compact Disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

, a black colour slide film, etc. must be avoided despite what may have been said in the media.

The safest way to view the Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera
Pinhole camera
A pinhole camera is a simple camera without a lens and with a single small aperture – effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box...

. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspot
Sunspot
Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....

s, as well as eclipses. Care must be taken, however, to ensure that no one looks through the projector (telescope, pinhole, etc.) directly. Viewing the Sun's disk on a video display screen (provided by a video camera
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...

 or digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...

) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe. Securely mounting #14 welder's glass in front of the lens and viewfinder protects the equipment and makes viewing possible. Professional workmanship is essential because of the dire consequences any gaps or detaching mountings will have. In the partial eclipse path one will not be able to see the corona or nearly complete darkening of the sky, yet, depending on how much of the sun's disk is obscured, some darkening may be noticeable. If two-thirds or more of the sun is obscured, then an effect can be observed by which the daylight appears to be dim, as if the sky were overcast, yet objects still cast sharp shadows.

Totality


It is safe to observe the total phase of a solar eclipse directly with the unaided eye, binoculars or a telescope, only when the Sun's photosphere is completely covered by the Moon. During this period the sun is too dim to be seen through filters. The Sun's faint corona
Corona
A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph...

 will be visible, and the chromosphere
Chromosphere
The chromosphere is a thin layer of the Sun's atmosphere just above the photosphere, roughly 2,000 kilometers deep....

, solar prominence
Solar prominence
A prominence is a large, bright feature extending outward from the Sun's surface, often in a loop shape. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the Sun's corona...

s, and possibly even a solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...

 may be seen. However, viewing the Sun after totality is dangerous.
When the shrinking visible part of the photosphere becomes very small, Baily's beads
Baily's beads
As the moon "grazes" by the Sun during a solar eclipse, the rugged lunar limb topography allows beads of sunlight to shine through in some places, and not in others. This effect is called Baily's beads in honor of Francis Baily who first provided an exact explanation of the phenomenon in 1836...

 will occur. These are caused by the sunlight still being able to reach Earth through lunar valleys, but no longer where mountains are present. Totality then begins with the diamond ring effect
Diamond ring effect (solar eclipse)
The diamond ring effect is a feature of total solar eclipses. Just before the sun disappears or just after it emerges from behind the moon, the rugged lunar limb topography allows beads of sunlight to shine through...

, the last bright flash of sunlight.

At the end of totality, the same effects will occur in reverse order, and on the opposite side of the moon.

Photography


Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the sun/moon to be easily visible, a fairly high magnification long focus lens is needed (70–200 mm for a 35 mm camera), and for the disk to fill most of the frame, a longer lens is needed (over 500 mm). As with viewing the sun directly, looking at it through the viewfinder of a camera
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

 can produce damage to the retina, so care is advised.

Other observations



For astronomers, a total solar eclipse forms a rare opportunity to observe the corona
Corona
A corona is a type of plasma "atmosphere" of the Sun or other celestial body, extending millions of kilometers into space, most easily seen during a total solar eclipse, but also observable in a coronagraph...

 (the outer layer of the Sun's atmosphere). Normally this is not visible because the photosphere
Photosphere
The photosphere of an astronomical object is the region from which externally received light originates. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to the fact that it is a spheric surface perceived...

 is much brighter than the corona. According to the point reached in the solar cycle
Solar cycle
The solar cycle, or the solar magnetic activity cycle, is a periodic change in the amount of irradiation from the Sun that is experienced on Earth. It has a period of about 11 years, and is one component of solar variation, the other being aperiodic fluctuations. Solar variation causes changes in...

, the corona may appear small and symmetric, or large and fuzzy. It is very hard to predict this prior to totality.

During a solar eclipse, special (indirect) observations can also be achieved with the unaided eye only. Normally the spots of light which fall through the small openings between the leaves of a tree have a circular shape. These are images of the Sun. During a partial eclipse, the light spots will show the partial shape of the Sun, as seen on the picture.

Another famous phenomenon is shadow bands
Shadow bands
Shadow bands are thin wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse. They are caused by the thin slot-like solar crescent illuminating the Earth's atmosphere moments before...

 (also known as flying shadows), which are similar to shadows on the bottom of a swimming pool. They only occur just prior to and after totality, and are very difficult to observe. Many professional eclipse chasers have never been able to witness them.

During a partial eclipse, a related effect that can be seen is anisotropy in the shadows of objects. Particularly if the partial eclipse is nearly total, the unobscured part of the sun acts as an approximate line source of light. This means that objects cast shadows which have a very narrow penumbra in one direction, but a broad penumbra in the perpendicular direction.

1919 observations


The observation of a total solar eclipse of May 29, 1919
Solar eclipse of May 29, 1919
A total solar eclipse occurred on May 29, 1919. With a maximum duration of totality of 6 minutes 51 seconds, it was one of the longest solar eclipses of the 20th century. It was visible throughout most of South America and Africa as a partial eclipse...

 helped to confirm Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

's theory of general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

. By comparing the apparent distance between two stars, with and without the Sun between them, Arthur Eddington stated that the theoretical predictions
Predictive power
The predictive power of a scientific theory refers to its ability to generate testable predictions. Theories with strong predictive power are highly valued, because the predictions can often encourage the falsification of the theory...

 about gravitational lens
Gravitational lens
A gravitational lens refers to a distribution of matter between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer...

es were confirmed, though it now appears the data was ambiguous at the time. The observation with the Sun between the stars was only possible during totality, since the stars are then visible.

Gravity anomalies


There is a long history of observations of gravity-related phenomena during solar eclipses, especially around totality. In 1954 and again in 1959, Maurice Allais
Maurice Allais
Maurice Félix Charles Allais was a French economist, and was the 1988 winner of the Nobel Memorial Prize in Economics "for his pioneering contributions to the theory of markets and efficient utilization of resources."...

 reported observations of strange and unexplained movement during solar eclipses. This phenomenon is now called the Allais Effect
Allais effect
The Allais effect is a claimed anomalous precession of the plane of oscillation of a pendulum during a solar eclipse. It has been speculated to be unexplained by standard physical models of gravitation, but recent mainstream physics publications tend rather to posit conventional explanations for...

. Similarly, Saxl and Allen in 1970 observed sudden change in motion of a torsion pendulum, and this phenomenon is called
the Saxl effect.

A recent published observation during the 1997 solar eclipse by Wang et al. suggested a possible gravitational shielding effect, though there is some serious debate. Later in 2002, Yang and Wang published detailed data analysis which suggested that the phenomenon still remains unexplained. More studies are being planned by NASA and ESA over the next decade.

Before sunrise, after sunset


The phenomenon of atmospheric refraction
Atmospheric refraction
Atmospheric refraction is the deviation of light or other things like humanelectromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of altitude...

 makes it possible to observe the Sun (and hence a solar eclipse) even when it is slightly below the horizon. It is, however, possible for a solar eclipse to attain totality (or in the event of a partial eclipse, near-totality) before (visual and actual) sunrise or after sunset from a particular location. When this occurs shortly before the former or after the latter, the sky will appear much darker than it would otherwise be immediately before sunrise or after sunset. On these occasions, an object (especially a planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

, often Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

) may be visible near the sunrise or sunset point of the horizon when it could not have been seen without the eclipse.

Eclipses and transits


In principle, the simultaneous occurrence of a Solar eclipse and a transit of a planet is possible. But these events are extremely rare because of their short durations. The next anticipated simultaneous occurrence of a Solar eclipse and a transit of Mercury
Transit of Mercury
A transit of Mercury across the Sun takes place when the planet Mercury comes between the Sun and the Earth, and Mercury is seen as a small black dot moving across the face of the Sun....

 will be on July 5, 6757, and a Solar eclipse and a transit of Venus
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun...

 is expected on April 5, 15232.

Only five hours after the transit of Venus on June 4, 1769, there was a total solar eclipse, which was visible in Northern America, Europe, and Northern Asia as partial solar eclipse. This was the lowest time difference between a transit of a planet and a solar eclipse in the historical past.

More common, but still infrequent, is a conjunction of any planet (not only Mercury or Venus) at the time of a total solar eclipse, in which event the planet will be visible very near the eclipsed Sun, when without the eclipse it would have been lost in the Sun's glare. At one time, some scientists hypothesized that there may be a planet (often given the name Vulcan) even closer to the Sun than Mercury; the only way to confirm its existence would have been to observe it during a total solar eclipse. It now is known that no such planet exists. While there does remain some possibility for small Vulcanoid asteroids to exist, none has ever been found.

Artificial satellites


Artificial satellites can also pass in front of, or transit, the Sun as seen from Earth, but none is large enough to cause an eclipse. At the altitude of the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

, for example, an object would need to be about 3.35 km (2.08 mi) across to blot the Sun out entirely. These transits are difficult to watch, because the zone of visibility is very small. The satellite passes over the face of the Sun in about a second, typically. As with a transit of a planet, it will not get dark.

Artificial satellites do play an important role in documenting solar eclipses. Images of the umbra on the Earth's surface taken from Mir
Mir
Mir was a space station operated in low Earth orbit from 1986 to 2001, at first by the Soviet Union and then by Russia. Assembled in orbit from 1986 to 1996, Mir was the first modular space station and had a greater mass than that of any previous spacecraft, holding the record for the...

 and the International Space Station are among the most spectacular of all eclipse images. Observations of eclipses from satellites orbiting above the Earth's atmosphere are not subject to weather conditions.

The direct observation of a total solar eclipse from space is rare. The only documented case is Gemini 12
Gemini 12
-Backup crew:-Mission parameters:*Mass: *Perigee: *Apogee: *Inclination: 28.87°*Period: 88.87 min-Docking:*Docked: November 12, 1966 - 01:06:00 UTC*Undocked: November 13, 1966 - 20:18:00 UTC-Space walk:...

 in 1966. The partial phase of the 2006 total eclipse was visible from the International Space Station. At first, it looked as though an orbit correction in the middle of March would bring the ISS in the path of totality, but this correction was postponed.

Meteorological measurements


A marked drop of the intensity of the solar radiation occurs during solar eclipse. It influences the actions in the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

. The variations of the atmospheric actions display in changes of standard meteorological and physical quantities
Quantity
Quantity is a property that can exist as a magnitude or multitude. Quantities can be compared in terms of "more" or "less" or "equal", or by assigning a numerical value in terms of a unit of measurement. Quantity is among the basic classes of things along with quality, substance, change, and relation...

. These may be noticed by a measurement of the air temperature and other meteorological quantities (e.g.: air humidity, soil temperature, colour of the solar radiation).

The progressions of the quantities are usually detected by special weather station
Weather station
A weather station is a facility, either on land or sea, with instruments and equipment for observing atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include temperature, barometric pressure, humidity, wind speed, wind...

s because of a short duration of a total (annular) solar eclipse. The properties of the devices usually are: high speed of measurement, high resolution, and sensitivity. Acquired results show variations in progressions of meteorological and physical quantities (e.g.: colour of the light).

Recent and forthcoming solar eclipses


Short term eclipse cycles repeat every six lunation
Lunation
Lunation is the mean time for one lunar phase cycle .  It is on average 29.530589 days, or 29 days 12 hours 44 minutes and 3 seconds...

s (every 177 days), each set lasting three–four years. They occur at either the ascending or descending node of the moon's orbit. Each set has the moon's shadow crossing the earth near the north or south pole, and subsequent events progress toward the other pole until it misses the earth and the series ends. The Saros cycle
Saros cycle
The saros is a period of 223 synodic months , that can be used to predict eclipses of the Sun and Moon. One saros after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle...

 increments by 5 within each set, and 5 different sets repeat every 18 years, the Saros period.
1997–2000
2000–2003
2004–2007
2008–2011
2011–2014
2015–2018
2018–2021
2022–2025


Eclipses elsewhere

  • Solar eclipses on Jupiter
    Solar eclipses on Jupiter
    Solar eclipses on Jupiter occur when any of the natural satellites of Jupiter pass in front of the Sun as seen from the planet Jupiter. For bodies which appear smaller in angular diameter than the Sun, the proper term would be a transit...

  • Solar eclipses on Saturn
    Solar eclipses on Saturn
    Solar eclipses on Saturn occur when the natural satellites of Saturn pass in front of the Sun as seen from Saturn. For bodies which appear smaller in angular diameter than the Sun, the proper term would be a transit. For bodies which are larger than the apparent size of the Sun, the proper term...

  • Solar eclipses on Uranus and Neptune
    Solar eclipses on Uranus and Neptune
    Solar eclipses on Uranus and Neptune occur when any of the natural satellites of both Uranus and Neptune pass in front of the Sun as seen from both planets. For bodies which appear smaller in angular diameter than the Sun, the proper term would be a transit...

  • Solar eclipses on Pluto
    Solar eclipses on Pluto
    Solar eclipses on Pluto are caused when one of its four natural satellites – Charon, Nix, Hydra, and P4 – passes in front of the Sun, blocking its light....

  • Transit of Deimos from Mars
    Transit of Deimos from Mars
    A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Sun's disc for an observer on Mars...

  • Transit of Phobos from Mars
    Transit of Phobos from Mars
    A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Sun's disc for an observer on Mars. During a transit, Phobos can be seen from Mars as a large black disc rapidly moving...


Eclipse lists


Articles on individual solar eclipses

Miscellaneous

  • Besselian Elements
    Besselian Elements
    The Besselian Elements are schedular values to calculate and predict the local circumstances of occultations for an observer on Earth. This method is particularly used for solar eclipses but also applied for occultations of stars or planets by the Moon and transits of Venus or Mercury...

  • Black Sun (mythology)
    Black Sun (mythology)
    The Black Sun in Mesoamerican mythology has many mystical meanings, among them it is connected to the god Quetzalcoatl and his penetration in the Underworld through the west door after his diurnal passage on the sky. Amidst the Mexicas there were two suns, the young day sun and the ancient sun,...

  • Solar eclipses in fiction
    Solar eclipses in fiction
    This is a list of fictional stories in which solar eclipses feature as an important plot element. Mere passing mentions are not listed.- Novels :* Dating of the Mahabharata with the help of a solar eclipse....


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