Eclipse

The type of solar eclipse that happens during each season (whether total, annular, hybrid, or partial) depends on apparent sizes of the Sun and Moon.

The term is derived from the ancient Greek noun ἔκλειψις (ékleipsis), which means 'the abandonment', 'the downfall', or 'the darkening of a heavenly body', which is derived from the verb ἐκλείπω (ekleípō) which means 'to abandon', 'to darken', or 'to cease to exist',[4] a combination of prefix ἐκ- (ek-), from preposition ἐκ (ek), 'out', and of verb λείπω (leípō), 'to be absent'.

The latter object will block some amount of light being emitted by the former, creating a region of shadow around the axis of the line.

During a lunar eclipse only the umbra and penumbra are applicable, because the antumbra of the Sun-Earth system lies far beyond the Moon.

Analogously, Earth's apparent diameter from the viewpoint of the Moon is nearly four times that of the Sun and thus cannot produce an annular eclipse.

An eclipse involving the Sun, Earth, and Moon can occur only when they are nearly in a straight line, allowing one to be hidden behind another, viewed from the third.

A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's shadow.

When the umbra does not reach the surface of the Earth, the Sun is only partially occulted, resulting in an annular eclipse.

Under the most favorable circumstances, a total solar eclipse can last for 7 minutes, 31 seconds, and can be viewed along a track that is up to 250 km wide.

Much as in a sunset, the atmosphere tends to more strongly scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue,[17] thus the phrase 'Blood Moon' is often found in descriptions of such lunar events as far back as eclipses are recorded.

[20] Positing classical-era astronomers' use of Babylonian eclipse records mostly from the 13th century BC provides a feasible and mathematically consistent[21] explanation for the Greek finding all three lunar mean motions (synodic, anomalistic, draconitic) to a precision of about one part in a million or better.

Chinese historical records of solar eclipses date back over 3,000 years and have been used to measure changes in the Earth's rate of spin.

[24] In 5th century AD, solar and lunar eclipses were scientifically explained by Aryabhata, in his treatise Aryabhatiya.

[25] Aryabhata states that the Moon and planets shine by reflected sunlight and explains eclipses in terms of shadows cast by and falling on Earth.

Indian computations were very accurate that 18th-century French scientist Guillaume Le Gentil, during a visit to Pondicherry, India, found the Indian computations of the duration of the lunar eclipse of 30 August 1765 to be short by only 41 seconds, whereas Le Gentil's charts were long by 68 seconds.

By the 1600s, European astronomers were publishing books with diagrams explaining how lunar and solar eclipses occurred.

[26][27] In order to disseminate this information to a broader audience and decrease fear of the consequences of eclipses, booksellers printed broadsides explaining the event either using the science or via astrology.

[28] The American author Gene Weingarten described the tension between belief and eclipses thus: "I am a devout atheist but can't explain why the moon is exactly the right size, and gets positioned so precisely between the Earth and the sun, that total solar eclipses are perfect.

"[29] The Graeco-Roman historian Cassius Dio, writing between AD 211–229, relates the anecdote that Emperor Claudius considered it necessary to prevent disturbance among the Roman population by publishing a prediction for a solar eclipse which would fall on his birthday anniversary [1 August in the year AD 45].

[30] Typically in mythology, eclipses were understood to be one variation or another of a spiritual battle between the sun and evil forces or spirits of darkness.

[32][failed verification] Other Norse tribes believed that there are two wolves by the names of Sköll and Hati that are in pursuit of the Sun and the Moon, known by the names of Sol and Mani, and these tribes believed that an eclipse occurs when one of the wolves successfully eats either the Sun or the Moon.

In the Hindu religion, for example, people often sing religious hymns for protection from the evil spirits of the eclipse, and many people of the Hindu religion refuse to eat during an eclipse to avoid the effects of the evil spirits.

[34] Hindu people living in India will also wash off in the Ganges River, which is believed to be spiritually cleansing, directly following an eclipse to clean themselves of the evil spirits.

[34] However, more ominous eclipses such as a blood moon were believed to be a divine sign that God would soon destroy their enemies.

The most striking involve Jupiter, which has four large moons and a low axial tilt, making eclipses more frequent as these bodies pass through the shadow of the larger planet.

Ole Rømer deduced that the delay was caused by the time needed for light to travel from Jupiter to the Earth.

On Mars, only partial solar eclipses (transits) are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun's disc as seen from the surface of the planet.