A solar eclipse occurs when the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
passes between
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an
eclipse season
An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...
, approximately every six months, during the
new moon
In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse.
...
phase, when the Moon's orbital plane is closest to
the plane of the Earth's orbit. In a total
eclipse
An eclipse is an astronomical event that 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 ce ...
, the disk of the Sun is fully obscured by the Moon. In
partial and annular eclipses, only part of the Sun is obscured. Unlike a
lunar eclipse
A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth ...
, which may be viewed from anywhere on the
night
Night (also described as night time, unconventionally spelled as "nite") is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends o ...
side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years.
If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses once a month, at every new moon. Instead, because the Moon's orbit is
tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during
eclipse season
An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...
s, resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total.
Total eclipses are more rare because they require a more precise alignment between the centers of the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
and
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
, and because the Moon's
apparent size
The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...
in the sky is sometimes too small to fully cover the Sun.
An eclipse is a
natural phenomenon
A natural phenomenon is an observable event which is not man-made. Examples include: sunrise, weather, fog, thunder, tornadoes; biological processes, decomposition, germination; physical processes, wave propagation, erosion; tidal flow, and natur ...
. In some ancient and modern cultures, solar eclipses were attributed to
supernatural
Supernatural refers to phenomena or entities that are beyond the laws of nature. The term is derived from Medieval Latin , from Latin (above, beyond, or outside of) + (nature) Though the corollary term "nature", has had multiple meanings si ...
causes or regarded as bad
omens. Astronomers' predictions of eclipses began in China as early as the 4th century BC; eclipses hundreds of years into the future may now be predicted with high accuracy.
Looking directly at the Sun can lead to permanent eye damage, so special eye protection or indirect viewing techniques are used when viewing a solar eclipse. Only the total phase of a total solar eclipse is safe to view without protection. Enthusiasts known as
eclipse chasers or umbraphiles travel to remote locations to see solar eclipses.
The symbol for an occultation, and especially a solar eclipse, is
file:Occultation symbol.svg (U+1F775 🝵).
Types
![Solar Eclipse May 20,2012](https://upload.wikimedia.org/wikipedia/commons/2/22/Solar_Eclipse_May_20%2C2012.jpg)
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
A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma.
The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar ...
to be visible. During any one eclipse, totality occurs at best only in a narrow track on the surface of Earth. This narrow track is called the path of totality.
* An annular eclipse occurs when the Sun and Moon are exactly in line with the Earth, 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 (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to:
Human anatomy
* ''Anulus fibrosus disci intervertebralis'', spinal structure
* Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...
, surrounding the dark disk of the Moon.
[Harrington, pp. 9–11]
* A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.
* A partial eclipse occurs when the Sun and Moon are not exactly in line with the Earth 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 be seen only as a partial eclipse, because the
umbra
The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
Th ...
passes above the Earth's polar regions and never intersects the Earth's surface.
Partial eclipses are virtually unnoticeable in terms of the Sun's brightness, as it takes well over 90% coverage to notice any darkening at all. Even at 99%, it would be no darker than
civil twilight
Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this il ...
.
![Comparison angular diameter](https://upload.wikimedia.org/wikipedia/commons/2/2c/Comparison_angular_diameter.svg)
The Sun's distance from Earth is about 400 times the Moon's distance, and the Sun's
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
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
A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle in which one full rotation is 360 degrees.
It is not an SI unit—the SI unit of angular measure is t ...
in angular measure.
The Moon's orbit around the Earth is slightly
elliptical
Elliptical may mean:
* having the shape of an ellipse, or more broadly, any oval shape
** in botany, having an elliptic leaf shape
** of aircraft wings, having an elliptical planform
* characterised by ellipsis (the omission of words), or by conc ...
, 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 Earth (''i.e.,'' near its
perigee
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion.
General description
There are two apsides in any ellip ...
) can be a total eclipse because the Moon will appear to be large enough to completely cover the Sun's bright disk or
photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
; a total eclipse has a magnitude greater than or equal to 1.000. Conversely, an eclipse that occurs when the Moon is near its farthest distance from Earth (''i.e.,'' near its
apogee
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion.
General description
There are two apsides in any ellip ...
) can be only 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.
A hybrid eclipse occurs when the magnitude of an eclipse changes during the event from less to greater than one, so the eclipse appears to be total at locations nearer the midpoint, and annular at other locations nearer the beginning and end, since the sides of the Earth are slightly further away from the Moon. These eclipses are extremely narrow in their path width and relatively short in their duration at any point compared with fully total eclipses; the 2023 April 20 hybrid eclipse's totality is over a minute in duration at various points along the path of totality. Like a
focal point, the width and duration of totality and annularity are near zero at the points where the changes between the two occur.
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 size of the Sun in the same way, but not as much as does the Moon's varying distance from Earth.
When Earth approaches its
farthest distance from the Sun in early July, a total eclipse is somewhat more likely, whereas conditions favour an annular eclipse when Earth approaches its
closest distance to the Sun in early 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 the Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse.
Gamma
Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...
is a measure of how centrally the shadow strikes. The last (umbral yet) non-central solar eclipse was
on April 29, 2014. This was an annular eclipse. The next non-central total solar eclipse will be
on April 9, 2043.
The visual phases observed during a total eclipse are called:
* First contact—when the Moon's limb (edge) is exactly tangential to the Sun's limb.
* Second contact—starting with
Baily's Beads
The Baily's beads effect or diamond ring effect is a feature of total and annular solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places ...
(caused by light shining through valleys on the Moon's surface) and the
diamond ring effect
The Baily's beads effect or diamond ring effect is a feature of total and annular solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places ...
. Almost the entire disk is covered.
* Totality—the Moon obscures the entire disk of the Sun and only the solar corona is visible.
* Third contact—when the first bright light becomes visible and the Moon's shadow is moving away from the observer. Again a diamond ring may be observed.
* Fourth contact—when the trailing edge of the Moon ceases to overlap with the solar disk and the eclipse ends.
Predictions
Geometry
![Geometry of a Total Solar Eclipse](https://upload.wikimedia.org/wikipedia/commons/0/00/Geometry_of_a_Total_Solar_Eclipse.svg)
The diagrams to the right show the alignment of the Sun, Moon, and Earth during a solar eclipse. The dark gray region between the Moon and Earth is the
umbra
The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
Th ...
, where the Sun is completely obscured by the Moon. The small area where the umbra touches Earth's surface is where a total eclipse can be seen. The larger light gray area is the
penumbra
The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
Th ...
, in which a partial eclipse can be seen. An observer in the
antumbra
The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast.
Th ...
, the area of shadow beyond the umbra, will see an annular eclipse.
The
Moon's orbit
The Moon orbits Earth in the retrograde and prograde motion, prograde direction and completes one orbital period, revolution relative to the March Equinox, Vernal Equinox and the fixed stars, stars in about 27.32 days (a tropical month and sider ...
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
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...
). Because of this, at the time of a new moon, the Moon will usually pass to the north or south of the Sun. A solar eclipse can occur only when a new moon occurs close to one of the points (known as
nodes
In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), vertex).
Node may refer to:
In mathematics
*Vertex (graph theory), a vertex in a mathematical graph
*Vertex (geometry), a point where two ...
) where the Moon's orbit crosses the ecliptic.
[Harrington, pp. 4–5]
As noted above, the Moon's orbit is also
elliptical
Elliptical may mean:
* having the shape of an ellipse, or more broadly, any oval shape
** in botany, having an elliptic leaf shape
** of aircraft wings, having an elliptical planform
* characterised by ellipsis (the omission of words), or by conc ...
. 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 as seen from the Earth, 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
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion.
General description
There are two apsides in any ellip ...
) that a total eclipse occurs.
The Moon orbits the Earth in approximately 27.3 days, relative to a
fixed frame of reference. This is known as the
sidereal month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Euro ...
. However, during one sidereal month, 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
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Europ ...
and corresponds to what is commonly called the
lunar month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Eur ...
.
The Moon crosses from south to north of the ecliptic at its
ascending node
An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit, which is contained in the reference plane, has no nodes.
Planes of reference
Common planes of reference ...
, and vice versa at its descending node.
However, the nodes of the Moon's orbit are gradually moving in a
retrograde motion
Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or ...
, 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 regression 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 nodical or
draconic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Europ ...
.
Finally, the Moon's perigee is moving forwards or precessing in its orbit and makes a complete circuit in 8.85 years. The time between one perigee and the next is slightly longer than the sidereal month and known as the
anomalistic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Euro ...
.
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 (173.3 days) apart, known as
eclipse season
An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...
s, 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 to eclipse the Sun on both occasions in two partial eclipses. This means that, in any given year, there will always be at least two solar eclipses, and there can be as many as five.
Eclipses can occur only 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, and is given in ranges because the apparent sizes and speeds of the Sun and Moon vary throughout the year. 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 eclipses (or rarely a partial and a central eclipse) 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, at about 28 km/min at the Equator, but as the Moon is moving in the same direction as the
Earth's rotation
Earth's rotation or Earth's spin is the rotation of planet Earth around its own Rotation around a fixed axis, axis, as well as changes in the orientation (geometry), orientation of the rotation axis in space. Earth rotates eastward, in retrograd ...
at about 61 km/min, the umbra almost always appears to move in a roughly west–east direction across a map of the Earth at the speed of the Moon's orbital velocity minus the Earth's rotational velocity.
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 up to wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse is seen over a much larger area of the Earth. Typically, the umbra is 100–160 km wide, while the penumbral diameter is in excess of 6400 km.
Besselian elements are used to predict whether an eclipse will be partial, annular, or total (or annular/total), and what the eclipse circumstances will be at any given location.
Calculations with Besselian elements can determine the exact shape of the umbra's shadow on the Earth's surface. But at what ''longitudes'' on the Earth's surface the shadow will fall, is a function of the Earth's rotation, and on how much that rotation has slowed down over time. A number called
ΔT is used in eclipse prediction to take this slowing into account. As the Earth slows, ΔT increases. ΔT for dates in the future can only be roughly estimated because the Earth's rotation is slowing irregularly. This means that, although it is possible to predict that there will be a total eclipse on a certain date in the far future, it is not possible to predict in the far future exactly at what longitudes that eclipse will be total. Historical records of eclipses allow estimates of past values of ΔT and so of the Earth's rotation.
Duration
The following factors determine the duration of a total solar eclipse (in order of decreasing importance):
# The Moon being almost exactly at perigee (making its angular diameter as large as possible).
# The Earth being very near
aphelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion.
General description
There are two apsides in any ell ...
(furthest away from the Sun in its elliptical orbit, making its angular diameter nearly as small as possible).
# The midpoint of the eclipse being very close to the Earth's equator, where the rotational velocity is greatest and is closest to the speed of the lunar shadow moving over Earth's surface.
# The vector of the eclipse path at the midpoint of the eclipse aligning with the vector of the Earth's rotation (i.e. not diagonal but due east).
# The midpoint of the eclipse being near the
subsolar point
The subsolar point on a planet is the point at which its sun is perceived to be directly overhead (at the zenith); that is, where the sun's rays strike the planet exactly perpendicular to its surface. It can also mean the point closest to the sun ...
(the part of the Earth closest to the Sun).
The longest eclipse that has been calculated thus far is the eclipse of
July 16, 2186 (with a maximum duration of 7 minutes 29 seconds over northern Guyana).
Occurrence and cycles
![Eclipse vs new or full moons, annotated](https://upload.wikimedia.org/wikipedia/commons/b/b9/Eclipse_vs_new_or_full_moons%2C_annotated.svg)
Total solar eclipses are rare events. Although they occur somewhere on Earth every 18 months on average, it is estimated that they recur at any given place only once every 360 to 410 years, on average. The total eclipse lasts for only a maximum of a few minutes at any location, because the Moon's umbra moves eastward at over 1700 km/h. Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s.
The last time an eclipse longer than 7 minutes occurred was
June 30, 1973 (7 min 3 sec). Observers aboard a
Concorde
The Aérospatiale/BAC Concorde () is a retired Franco-British supersonic airliner jointly developed and manufactured by Sud Aviation (later Aérospatiale) and the British Aircraft Corporation (BAC).
Studies started in 1954, and France an ...
supersonic aircraft were able to stretch totality for this eclipse to about 74 minutes by flying along the path of the Moon's umbra. The next total eclipse exceeding seven minutes in duration will not occur until
June 25, 2150. The longest total solar eclipse during the 11,000 year period from 3000 BC to at least 8000 AD will occur on
July 16, 2186, when totality will last 7 min 29 s.
For comparison, the longest total eclipse of the 20th century at 7 min 8 s occurred on
June 20, 1955, and there will be no total solar eclipses over 7 min in duration in the 21st century.
It is possible to predict other eclipses using
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
Eclips ...
s. The
saros is probably the best known and one of the most accurate. 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 westward shift of about 120° in longitude (due to the 0.3 days) and a little in latitude (north-south for odd-numbered cycles, the reverse for even-numbered ones). 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 with a partial eclipse at the opposite polar region. A saros series lasts 1226 to 1550 years and 69 to 87 eclipses, with about 40 to 60 of them being central.
Frequency per year
Between two and five solar eclipses occur every year, with at least one per
eclipse season
An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...
. Since the
Gregorian calendar
The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years dif ...
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. On average, there are about 240 solar eclipses each century.
Final totality
Total solar eclipses are seen on Earth because of a fortuitous combination of circumstances. Even on Earth, the diversity of eclipses familiar to people today is a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was closer to the Earth and therefore apparently larger, so every solar eclipse was total or partial, and there were no annular eclipses. Due to
tidal acceleration
Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit away from ...
, the orbit of the Moon around the Earth becomes approximately 3.8 cm more distant each year. Millions of years in the future, the Moon will be too far away to fully occlude the Sun, and no total eclipses will occur. In the same timeframe, the Sun may become brighter, making it appear larger in size.
Estimates of the time when the Moon will be unable to occlude the entire Sun when viewed from the Earth range between 650 million and 1.4 billion years in the future.
Historical eclipses
![Antoine Caron Astronomers Studying an Eclipse](https://upload.wikimedia.org/wikipedia/commons/8/85/Antoine_Caron_Astronomers_Studying_an_Eclipse.jpg)
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 ancient calendars may be deduced. A
solar eclipse of June 15, 763 BC mentioned in an
Assyrian
Assyrian may refer to:
* Assyrian people, the indigenous ethnic group of Mesopotamia.
* Assyria, a major Mesopotamian kingdom and empire.
** Early Assyrian Period
** Old Assyrian Period
** Middle Assyrian Empire
** Neo-Assyrian Empire
* Assyrian ...
text is important for the
chronology of the ancient Near East. There have been other claims to date earlier eclipses. The
Book of Joshua
The Book of Joshua ( he, סֵפֶר יְהוֹשֻׁעַ ', Tiberian: ''Sēp̄er Yŏhōšūaʿ'') is the sixth book in the Hebrew Bible and the Christian Old Testament, and is the first book of the Deuteronomistic history, the story of Isra ...
10:13 describes the sun staying still for an entire day in the sky; a group of
University of Cambridge
, mottoeng = Literal: From here, light and sacred draughts.
Non literal: From this place, we gain enlightenment and precious knowledge.
, established =
, other_name = The Chancellor, Masters and Schola ...
scholars have argued that this was an annular solar eclipse that occurred on 30 October 1207 BC. The legendary Chinese king
Zhong Kang
Zhong Kang () was the fourth king of the Xia Dynasty, the first dynasty in traditional Chinese history.
Family
Zhong Kang was a son of king Qi of Xia and thus the younger brother of Tai Kang. He was the father of Xiang of Xia.
Reign
According ...
supposedly beheaded two astronomers, Hsi and Ho, who failed to predict an eclipse 4,000 years ago. Perhaps the earliest still-unproven claim is that of archaeologist Bruce Masse, who putatively links an eclipse that occurred on May 10, 2807, BC with a possible
meteor impact
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...
in the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
on the basis of several ancient
flood myth
A flood myth or a deluge myth is a myth in which a great flood, usually sent by a deity or deities, destroys civilization, often in an act of divine retribution. Parallels are often drawn between the flood waters of these Mythology, myths and the ...
s that mention a total solar eclipse. The earliest preserved depiction of a partial solar eclipse from 1143 BCE might be the one in tomb KV9 of Ramses V and Ramses VI.
![Ibn Yunus eclipses 1004 CE manuscript records Arabic](https://upload.wikimedia.org/wikipedia/commons/5/5f/Ibn_Yunus_eclipses_1004_CE_manuscript_records_Arabic.jpg)
Eclipses have been interpreted as
omens, or portents. The ancient Greek historian
Herodotus
Herodotus ( ; grc, , }; BC) was an ancient Greek historian and geographer from the Greek city of Halicarnassus, part of the Persian Empire (now Bodrum, Turkey) and a later citizen of Thurii in modern Calabria ( Italy). He is known f ...
wrote that
Thales of Miletus
Thales of Miletus ( ; grc-gre, Θαλῆς; ) was a Greek mathematician, astronomer, statesman, and pre-Socratic philosopher from Miletus in Ionia, Asia Minor. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded ...
predicted
an eclipse that occurred during a battle between the
Medes
The Medes (Old Persian: ; Akkadian: , ; Ancient Greek: ; Latin: ) were an ancient Iranian people who spoke the Median language and who inhabited an area known as Media between western and northern Iran. Around the 11th century BC, the ...
and the
Lydia
Lydia (Lydian language, Lydian: 𐤮𐤱𐤠𐤭𐤣𐤠, ''Śfarda''; Aramaic: ''Lydia''; el, Λυδία, ''Lȳdíā''; tr, Lidya) was an Iron Age Monarchy, kingdom of western Asia Minor located generally east of ancient Ionia in the mod ...
ns. Both sides put down their weapons and declared peace as a result of the eclipse. The exact eclipse involved remains 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 river in
Asia Minor
Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The re ...
. An eclipse recorded by Herodotus before
Xerxes departed for his expedition against
Greece
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders with ...
, which is traditionally dated to 480 BC, was matched by
John Russell Hind
John Russell Hind FRS FRSE LLD (12 May 1823 – 23 December 1895) was an English astronomer.
Life and work
John Russell Hind was born in 1823 in Nottingham, the son of lace manufacturer John Hind and Elizabeth Russell, and was educated at ...
to an annular eclipse of the Sun at
Sardis
Sardis () or Sardes (; Lydian: 𐤳𐤱𐤠𐤭𐤣 ''Sfard''; el, Σάρδεις ''Sardeis''; peo, Sparda; hbo, ספרד ''Sfarad'') was an ancient city at the location of modern ''Sart'' (Sartmahmut before 19 October 2005), near Salihli, ...
on February 17, 478 BC. Alternatively, a partial eclipse was visible from Persia on October 2, 480 BC.
Herodotus also reports a solar eclipse at
Sparta
Sparta ( Doric Greek: Σπάρτα, ''Spártā''; Attic Greek: Σπάρτη, ''Spártē'') was a prominent city-state in Laconia, in ancient Greece. In antiquity, the city-state was known as Lacedaemon (, ), while the name Sparta referre ...
during the
Second Persian invasion of Greece
The second Persian invasion of Greece (480–479 BC) occurred during the Greco-Persian Wars, as King Xerxes I of Persia sought to conquer all of Greece. The invasion was a direct, if delayed, response to the defeat of the first Persian invasion ...
. The date of the eclipse (August 1, 477 BC) does not match exactly the conventional dates for the invasion accepted by historians.
Chinese records of eclipses begin at around 720 BC.
The 4th century BC astronomer
Shi Shen
Shi Shen (, Floruit, fl. 4th century BC) was a Chinese astronomer and astrologer. He was a contemporary of Gan De born in the State of Wei, also known as the Shi Shenfu.
Observations
Shi is credited with positioning the 121 stars found in the pres ...
described the prediction of eclipses by using the relative positions of the Moon and Sun.
Attempts have been made to establish the exact date of
Good Friday
Good Friday is a Christian holiday commemorating the crucifixion of Jesus and his death at Calvary. It is observed during Holy Week as part of the Paschal Triduum. It is also known as Holy Friday, Great Friday, Great and Holy Friday (also Hol ...
by assuming that the
darkness described at Jesus's crucifixion was a solar eclipse. This research has not yielded conclusive results, and Good Friday is recorded as being at
Passover
Passover, also called Pesach (; ), is a major Jewish holidays, Jewish holiday that celebrates the The Exodus, Biblical story of the Israelites escape from slavery in Ancient Egypt, Egypt, which occurs on the 15th day of the Hebrew calendar, He ...
, which is held at the time of a full moon. Further, the darkness lasted from the sixth hour to the ninth, or three hours, which is much, much longer than the eight-minute upper limit for any solar eclipse's totality. Contemporary chronicles wrote about an eclipse at the beginning of May
664
__NOTOC__
Year 664 ( DCLXIV) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar. The denomination 664 for this year has been used since the early medieval period, when the Anno Domini calendar era be ...
that coincided with the beginning of the
plague of 664
The plague of 664 was an epidemic that affected Great Britain, Britain and Ireland in 664 AD, during the first plague pandemic. It was the first recorded epidemic in English history, and coincided with a solar eclipse. It was considered by later ...
in the British isles. In the Western hemisphere, there are few reliable records of eclipses before AD 800, until the advent of Arab and monastic observations in the early medieval period.
The Cairo astronomer
Ibn Yunus
Abu al-Hasan 'Ali ibn 'Abd al-Rahman ibn Ahmad ibn Yunus al-Sadafi al-Misri (Arabic: ابن يونس; c. 950 – 1009) was an important Egyptians, Egyptian astronomer and Islamic mathematics, mathematician, whose works are noted for being ahead o ...
wrote that the calculation of eclipses was one of the many things that connect astronomy with the
Islamic law
Sharia (; ar, شريعة, sharīʿa ) is a body of religious law that forms a part of the Islamic tradition. It is derived from the religious precepts of Islam and is based on the sacred scriptures of Islam, particularly the Quran and the ...
, because it allowed knowing when
a special prayer can be made. The first recorded observation of the corona was made in
Constantinople
la, Constantinopolis ota, قسطنطينيه
, alternate_name = Byzantion (earlier Greek name), Nova Roma ("New Rome"), Miklagard/Miklagarth (Old Norse), Tsargrad ( Slavic), Qustantiniya (Arabic), Basileuousa ("Queen of Cities"), Megalopolis (" ...
in AD 968.
The first known telescopic observation of a total solar eclipse was made in France in 1706.
Nine years later, English astronomer
Edmund Halley
Edmond (or Edmund) Halley (; – ) was an English astronomer, mathematician and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720.
From an observatory he constructed on Saint Helena in 1676–77, Ha ...
accurately predicted and observed the
solar eclipse of May 3, 1715
__NOTOC__
A total solar eclipse occurred on 3 May 1715. It was known as Halley's Eclipse, after Edmond Halley (1656–1742) who predicted this eclipse to within 4 minutes accuracy. Halley observed the eclipse from London where the city of London ...
.
By the mid-19th century, scientific understanding of the Sun was improving through observations of the Sun's corona during solar eclipses. The corona was identified as part of the Sun's atmosphere in
1842
Events
January–March
* January
** Michael Alexander takes office, as the first appointee to the Anglican-German Bishopric in Jerusalem.
** American medical student William E. Clarke of Berkshire Medical College becomes the first pe ...
, and the first photograph (or
daguerreotype
Daguerreotype (; french: daguerréotype) was the first publicly available photographic process; it was widely used during the 1840s and 1850s. "Daguerreotype" also refers to an image created through this process.
Invented by Louis Daguerre an ...
) of a total eclipse was taken of the
solar eclipse of July 28, 1851
The earliest scientifically useful photograph of a total solar eclipse was made by Julius Berkowski at the Royal Observatory in Königsberg, Prussia, on July 28, 1851. This was the first occasion that an accurate photographic image of a solar e ...
.
Spectroscope
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...
observations were made of the
solar eclipse of August 18, 1868
A total solar eclipse occurred on August 18, 1868, also known as "The King of Siam's eclipse". A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. ...
, which helped to determine the chemical composition of the Sun.
John Fiske summed up myths about the solar eclipse like this in his 1872 book ''Myth and Myth-Makers'',
Viewing
Looking directly at the
photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent
damage
Damage is any change in a thing, often a physical object, that degrades it away from its initial state. It can broadly be defined as "changes introduced into a system that adversely affect its current or future performance".Farrar, C.R., Sohn, H., ...
to the
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including
blindness
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment ...
. 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. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Looking at the Sun during an eclipse is 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 within a fraction of a second.
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
A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...
removed from its case, a
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...
, a black colour slide film, smoked glass, etc. must be avoided.
The safest way to view the Sun's disk is by indirect projection.
[Harrington, p. 25] 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
A pinhole camera is a simple camera without a lens but with a tiny aperture (the so-called ''pinhole'')—effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image o ...
. The projected image of the Sun can then be safely viewed; this technique can be used to observe
sunspots, 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
A video camera is an optical instrument that captures videos (as opposed to a movie camera, which records images on film). Video cameras were initially developed for the television industry but have since become widely used for a variety of oth ...
or
digital camera
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
) 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. However, depending on how much of the Sun's disk is obscured, some darkening may be noticeable. If three-quarters 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
When the shrinking visible part of the photosphere becomes very small,
Baily's beads
The Baily's beads effect or diamond ring effect is a feature of total and annular solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places ...
will occur. These are caused by the sunlight still being able to reach the Earth through lunar valleys. Totality then begins with the
diamond ring effect
The Baily's beads effect or diamond ring effect is a feature of total and annular solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places ...
, the last bright flash of sunlight.
It is safe to observe the total phase of a solar eclipse directly only when the Sun's photosphere is completely covered by the Moon, and not before or after totality.
During this period, the Sun is too dim to be seen through filters. The Sun's faint
corona
Corona (from the Latin for 'crown') most commonly refers to:
* Stellar corona, the outer atmosphere of the Sun or another star
* Corona (beer), a Mexican beer
* Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
will be visible, and the
chromosphere,
solar prominence
A prominence, sometimes referred to as a filament, is a large plasma and magnetic field structure 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 outw ...
s, and possibly even a
solar flare
A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phe ...
may be seen. At the end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon.
Eclipse chasing
A dedicated group of eclipse chasers have pursued the observation of solar eclipses when they occur around the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
. A person who chases eclipses is known as an umbraphile, meaning shadow lover.
Umbraphiles travel for eclipses and use various tools to help view the sun including
solar viewing glasses, also known as eclipse glasses, as well as telescopes.
Photography
![2008-08-01 Solar eclipse progression with timestamps](https://upload.wikimedia.org/wikipedia/commons/5/58/2008-08-01_Solar_eclipse_progression_with_timestamps.jpg)
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
In photography, a long-focus lens is a camera lens which has a focal length that is longer than the diagonal measure of the film or sensor that receives its image.
It is used to make distant objects appear magnified with magnification increas ...
is needed (at least 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 optical viewfinder of a camera can produce damage to the retina, so care is recommended. Solar filters are required for digital photography even if an optical viewfinder is not used. Using a camera's live view feature or an electronic viewfinder is safe for the human eye, but the Sun's rays could potentially irreparably damage digital image sensors unless the lens is covered by a properly designed solar filter.
Other observations
A total solar eclipse provides a rare opportunity to observe the
corona
Corona (from the Latin for 'crown') most commonly refers to:
* Stellar corona, the outer atmosphere of the Sun or another star
* Corona (beer), a Mexican beer
* Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
(the outer layer of the Sun's atmosphere). Normally this is not visible because the
photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
is much brighter than the corona. According to the point reached in the
solar cycle
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surfa ...
, the corona may appear small and symmetric, or large and fuzzy. It is very hard to predict this in advance.
![eclipse_shadows](https://upload.wikimedia.org/wikipedia/commons/3/38/Eclipse_shadows.svg)
As the light filters through leaves of trees during a partial eclipse, the overlapping leaves create natural pinholes, displaying mini eclipses on the ground.
Phenomena associated with eclipses include
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 refraction by Earth's atmosphe ...
(also known as ''flying shadows''), which are similar to shadows on the bottom of a swimming pool. They occur only just prior to and after totality, when a narrow solar crescent acts as an
anisotropic
Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
light source.
1919 observations
![1919 eclipse positive](https://upload.wikimedia.org/wikipedia/commons/3/37/1919_eclipse_positive.jpg)
The observation of a total
solar eclipse of May 29, 1919
A total solar eclipse occurred on Thursday, May 29, 1919. With the duration of totality at maximum eclipse of 6 minutes 50.75 seconds, it was the longest solar eclipse since May 27, 1416. A longer total solar eclipse would later occur on June 8 ...
, helped to confirm
Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...
's theory of
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
. By comparing the apparent distance between stars in the constellation
Taurus
Taurus is Latin for 'bull' and may refer to:
* Taurus (astrology), the astrological sign
* Taurus (constellation), one of the constellations of the zodiac
* Taurus (mythology), one of two Greek mythological characters named Taurus
* '' Bos tauru ...
, with and without the Sun between them,
Arthur Eddington stated that the
theoretical predictions about
gravitational lens
A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer that is capable of bending the light from the source as the light travels toward the observer. This effect is known ...
es were confirmed.
The observation with the Sun between the stars was possible only during totality since the stars are then visible. Though Eddington's observations were near the experimental limits of accuracy at the time, work in the later half of the 20th century confirmed his results.
Gravity anomalies
There is a long history of observations of gravity-related phenomena during solar eclipses, especially during the period of totality. In 1954, and again in 1959,
Maurice Allais
Maurice Félix Charles Allais (31 May 19119 October 2010) was a French physicist and economist, the 1988 winner of the Nobel Memorial Prize in Economic Sciences "for his pioneering contributions to the theory of markets and efficient utilization o ...
reported observations of strange and unexplained movement during solar eclipses. The reality of this phenomenon, named the
Allais effect, has remained controversial. Similarly, in 1970,
Saxl and
Allen Allen, Allen's or Allens may refer to:
Buildings
* Allen Arena, an indoor arena at Lipscomb University in Nashville, Tennessee
* Allen Center, a skyscraper complex in downtown Houston, Texas
* Allen Fieldhouse, an indoor sports arena on the Unive ...
observed the sudden change in motion of a torsion pendulum; this phenomenon is called the Saxl effect.
Observation during the 1997 solar eclipse by Wang ''et al.'' suggested a possible
gravitational shielding
The term gravitational shielding refers to a hypothetical process of shielding an object from the influence of a gravitational field. Such processes, if they existed, would have the effect of reducing the weight of an object. The shape of the shie ...
effect, which generated debate. In 2002, Wang and a collaborator published detailed data analysis, which suggested that the phenomenon still remains unexplained.
Eclipses and transits
In principle, the simultaneous occurrence of a solar eclipse and a
transit
Transit may refer to:
Arts and entertainment Film
* ''Transit'' (1979 film), a 1979 Israeli film
* ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world
* ''Transit'' (2006 film), a 2006 ...
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
frameless, upright=0.5
A transit of Mercury across the Sun takes place when the planet Mercury passes directly between the Sun and a superior planet. During a transit, Mercury appears as a tiny black dot moving across the Sun as the planet obs ...
will be on July 5, 6757, and a solar eclipse and a
transit of Venus
frameless, upright=0.5
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a trans ...
is expected on April 5, 15232.
More common, but still infrequent, is a
conjunction
Conjunction may refer to:
* Conjunction (grammar), a part of speech
* Logical conjunction, a mathematical operator
** Conjunction introduction, a rule of inference of propositional logic
* Conjunction (astronomy), in which two astronomical bodies ...
of a planet (especially, but 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
Vulcan may refer to:
Mythology
* Vulcan (mythology), the god of fire, volcanoes, metalworking, and the forge in Roman mythology
Arts, entertainment and media Film and television
* Vulcan (''Star Trek''), name of a fictional race and their home p ...
) even closer to the Sun than Mercury; the only way to confirm its existence would have been to observe it in transit or during a total solar eclipse. No such planet was ever found, and
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
has since explained the observations that led astronomers to suggest that Vulcan might exist.
Artificial satellites
![Eclipse fromISS 2006-03-29](https://upload.wikimedia.org/wikipedia/commons/4/42/Eclipse_fromISS_2006-03-29.jpg)
Artificial satellites can also pass in front of the Sun as seen from the Earth, but none is large enough to cause an eclipse. At the altitude of the
International Space Station
The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
, for example, an object would need to be about 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.
Observations of eclipses from spacecraft or artificial satellites orbiting above the Earth's atmosphere are not subject to weather conditions. The crew of
Gemini 12
Gemini 12 (officially Gemini XII) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was a 1966 crewed spaceflight in NASA's Project Gemini. It was the 10th and final crewed Gemini flight ( Gemini 1 and Gemini 2 wer ...
observed a total solar eclipse from space in 1966. The partial phase of the
1999 total eclipse was visible from
Mir
''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...
.
Impact
The
solar eclipse of March 20, 2015
A total solar eclipse occurred on March 20, 2015. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's ...
, was the first occurrence of an eclipse estimated to potentially have a significant impact on the power system, with the electricity sector taking measures to mitigate any impact. The
continental Europe
Continental Europe or mainland Europe is the contiguous continent of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by ...
and
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
synchronous areas were estimated to have about 90
gigawatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
s of
solar power
Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic e ...
and it was estimated that production would temporarily decrease by up to 34 GW compared to a clear sky day.
[Solar Eclipse 2015 – Impact Analysis]
" pp. 3, 6–7, 13. '''', 19 February 2015. Accessed: 4 March 2015.
Eclipses may cause the temperature to decrease by 3 °C, with
wind power
Wind power or wind energy is mostly the use of wind turbines to electricity generation, generate electricity. Wind power is a popular, sustainable energy, sustainable, renewable energy source that has a much smaller Environmental impact of wi ...
potentially decreasing as winds are reduced by 0.7 m/s.
In addition to the drop in light level and air temperature, animals change their behavior during totality. For example, birds and squirrels return to their nests and crickets chirp.
Recent and forthcoming solar eclipses
![Solar eclipses 2021-2040](https://upload.wikimedia.org/wikipedia/commons/6/6e/Solar_eclipses_2021-2040.png)
Eclipses occur only in the
eclipse season
An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...
, when the Sun is close to either the ascending or descending
node of the Moon. Each eclipse is separated by one, five or six
lunation
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Euro ...
s (
synodic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Europ ...
s), and the midpoint of each season is separated by 173.3 days, which is the mean time for the Sun to travel from one node to the next. The period is a little less than half a calendar year because the lunar nodes slowly regress. Because 223 synodic months is roughly equal to 239
anomalistic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Euro ...
s and 242
draconic month
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
Variations
In Shona, Middle Eastern, and Europ ...
s, eclipses with similar geometry recur 223 synodic months (about 6,585.3 days) apart. This period (18 years 11.3 days) is a
saros. Because 223 synodic months is not identical to 239 anomalistic months or 242 draconic months, saros cycles do not endlessly repeat. Each cycle begins with the Moon's shadow crossing the Earth near the north or south pole, and subsequent events progress toward the other pole until the Moon's shadow misses the Earth and the series ends.
Saros cycles are numbered; currently, cycles 117 to 156 are active.
See also
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Lists of solar eclipses
There are several lists of solar eclipses.
On Earth, by the Moon By location
* List of solar eclipses visible from Australia
* List of solar eclipses visible from China
* List of solar eclipses visible from the Philippines
* List of solar eclip ...
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Apollo–Soyuz
Apollo–Soyuz was the first crewed international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo spacecraft docked ...
: An artificial solar eclipse
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Eclipse chasing
Eclipse chasing is the pursuit of observing solar eclipses when they occur around the Earth. Solar eclipses must occur at least twice and as often as five times a year across the Earth. Total eclipses may occur multiple times every few years.
A pe ...
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Lunar eclipse
A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth ...
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Occultation
An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...
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Solar eclipses in fiction
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Solar eclipses on the Moon
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Transit of Deimos from Mars
A transit of Deimos across the Sun as seen from Mars occurs when Deimos (moon), 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. During a astronomical t ...
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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 ...
Notes
References
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External links
NASA Eclipse Web Site Fred Espenak's new eclipse site
with maps and circumstances for 5000 years of solar eclipses
Detailed eclipse explanations and predictions Hermit Eclipse
Eclipse Photography Prof. Miroslav Druckmüller
Larry Koehn
Xavier M. Jubier
, University of South Wales
Eclipse Image Gallery, The World at Night
Ring of Fire Eclipse: 2012 Photos
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Solar eclipse photographs taken from the Lick Observatory from the Lick Observatory Records Digital Archive, UC Santa Cruz Library’s Digital Collections
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Total Solar Eclipse Shadow on Earth March 09 2016 CIMSSSatelite
List of all solar eclipsesNational Geographic Solar Eclipse 101 video
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Eclipses