Eclipse

Solar eclipse.

The eclipse (from the Greek ἔκλειψις, ékleipsis, which means 'disappearance', 'abandonment') is a phenomenon in which light from a celestial body it is blocked by another eclipsing body. There are eclipses of the Sun and the Moon, which occur only when the Sun and the Moon align with the Earth in a certain way. This happens during some new moons and full moons.

However, eclipses can also occur outside the Earth-Moon system. For example, when the shadow of a satellite is cast on the surface of a planet, when a satellite passes through the shadow of a planet, or when a satellite casts its shadow on another satellite.

An eclipse, like transits and occultations, is a type of syzygy.

In the Sun-Earth-Moon System

Eclipses of the Earth-Moon system can only occur when the Sun, Earth, and Moon are aligned. These eclipses are divided into:

• Moon eclipse. The Earth stands between the Sun and the Moon; it darkens the latter. The Moon enters the Earth's shadow zone. This can only happen on a full moon. The lunar eclipses, in turn, are divided into totals, partial and penumbral, depending on whether the Moon passes in whole or part by the shade cone projected by the Earth, or if it only does it through the area of the penumbra.

• Solar eclipse. The Moon prevents the passage of sunlight to the earth, interposes between it and the sun. That can only happen on a new moon. Solar eclipses are divided in turn into total, partial and annular.

For this alignment to occur, it is essential that the Moon is in full or new phase. Even so, as the plane of translation of the Moon around the Earth is inclined about 5° with respect to the ecliptic, an eclipse is not always produced when there is a full moon or a new moon. Sometimes the Moon passes above or below the Earth's shadow, so there is no lunar eclipse, while, being at the opposite point of its orbit, the shadow it casts passes above or below the Earth. However, when the full or new moon occurs close enough to the node—that is, close to the intersection of the plane of translation of the moon with the ecliptic—a solar or lunar eclipse occurs.

Eclipse prediction

Eclipses can be predicted in two different ways. The first, made possible with the development of computing, is to calculate the orbits of the Earth and the Moon with great precision, thus predicting the exact positions of their shadows and recording the times when the shadows fall on the Earth. the other star The second way, which is the one that has been used from the time of the Assyrians and Babylonians until today, consists of writing down their cyclical repetitions. The most notable cycle with which they are repeated is the saros cycle, based on a geocentric model. A saro contains 6,585.3 days (18 years, 10 or 11 days and about 8 hours), and after this period almost identical orbital circumstances are repeated, so a very similar eclipse occurs, although displaced about 140° to the west (for the 8 hours difference, which makes the Earth have rotated 1/3 of a revolution).

Eclipses in the Solar System

Eclipses are impossible on Mercury and Venus, due to their lack of satellites. But you can see how these planets stand between the Earth and the Sun, which is called astronomical transit.

On Mars, only partial eclipses are possible, because none of its moons is large enough to cover the solar disk. Partial eclipses have been photographed from the planet's surface and from orbiting vehicles. The view of Mars from Earth can be obscured by the Moon at night, known as an occultation.

The gas giants, which have many moons, show frequent eclipses. The most prominent affect Jupiter, whose four large moons and low axis tilt make them routine.

Eclipses in mythology and religion

Before eclipses were as well understood as they are today, there was a much more fearful connotation surrounding these seemingly inexplicable events. There was very considerable confusion regarding eclipses before the 17th century because eclipses were not very accurately or scientifically described until Johannes Kepler provided a scientific explanation for eclipses in the early 17th century. Typically in mythology, eclipses were understood as one variation or another of a spiritual battle between the sun and evil forces or spirits of darkness. The phenomenon of the sun appearing to disappear was a very fearsome sight to all who they did not understand the science of eclipses, as well as for those who supported and believed in the idea of mythological gods. The sun was considered divine by many ancient religions, and some even viewed eclipses as if the sun god were overwhelmed by evil spirits. More specifically, in Norse mythology, there is believed to be a wolf named Fenrir who constantly chases the sun., and eclipses are believed to occur when the wolf successfully devours the divine sun. Other Norse tribes believe that there are two wolves by the names of Sköll and Hati that chase the sun and the moon, known by the names of Sol and Mani, and these tribes believe that an eclipse occurs when one of the wolves eats itself with hit the sun or the moon. Once again, this mythical explanation was a very common source of fear for most people at the time who believed that the sun was some kind of divine power or god, because the known explanations for eclipses were quite often seen as false. the fall of their highly regarded god. Similarly, other mythological explanations of eclipses describe the phenomenon of darkness covering the sky during the day as a war between the gods of the sun and the moon.

In most mythologies and some religions, eclipses were considered a sign that the gods were angry and danger was coming soon, so people often altered their actions in an effort to deter the gods. gods to unleash their wrath. In the Hindu religion, for example, people often sing religious hymns to ward off 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. Hindus living in India also wash in the Ganges River, which is believed to be spiritually cleansing, directly after an eclipse to cleanse themselves of evil spirits. In early Judaism and Christianity, eclipses were seen as signs of God, and some eclipses were considered a sign of God's greatness or even signs of cycles of life and death. However, it was believed that more ominous eclipses, like a blood moon, were a divine sign that God would soon destroy his enemies.