We explain what an eclipse is and how this phenomenon occurs. Also, the differences between a solar eclipse and a lunar eclipse.
What is an eclipse?
An eclipse is an astronomical phenomenon in which the light of an incandescent star, like the Sun, is totally or partially covered by another opaque star that intervenes (known as eclipsing body) and whose shadow is projected on the planet Earth. Its name comes from the Greek ekleipsis: "Disappearance".
In principle, eclipses can occur between any set of stars, as long as the dynamics of light and interposition described above are produced. However, as there are no off-planet observers, we generally speak of two types of eclipse: lunar or solar eclipses. Moon, and solar or solar eclipses, depending on which celestial body is obscured.
From the antiquity, eclipses fascinated and disturbed the human being, whose ancient civilizations they saw in them a sign of change, catastrophe or rebirth, if not a bad omen, since most religions worshiped the Sun in one way or another.
However, these phenomena were understood and predicted by ancient civilizations endowed with knowledge astronomical, since they studied the recurrence of the astral cycles in their various calendars. Some of them came to use them to distinguish between political, religious or social epochs or eras.
Why do eclipses occur?
In the lunar eclipse, the Earth casts a shadow that obscures the Moon.The logic of eclipses is simple: a celestial body stands between us and some light source, producing a shadow that can sometimes block much of the brightness. It is something similar to what happens when we pass an object in front of the light of an overhead projector: its shadow is also projected on the backdrop.
For eclipses to occur, however, there must be a more or less exact confluence of spatial factors between the Moon, the Earth, and the Sun, which occurs once every certain number of orbital repetitions. That is why they occur with a certain frequency.
In addition, they can be predicted with the help of a computer, for example, since we know the time it takes to Earth in revolving around the Sun Y around its axis, as well as the time it takes for the Moon to orbit our planet.
solar eclipse
In solar eclipses, the Moon comes between the Sun and the Earth.The solar eclipse occurs when the Moon comes between the Earth and the Sun, casting its shadow on a portion of the land surface, whose day is overshadowed for a moment. This can only happen during a new moon, and it can happen in three different ways:
- Partial solar eclipse. The Moon partially overshadows the sunlight or a visible segment of its circumference, leaving the rest visible.
- Total solar eclipse. The position of the Moon is correct so that, in a certain place on Earth, the Sun is totally obscured and an artificial night of a few minutes takes place.
- Annular solar eclipse. The Moon coincides with the Sun in its positioning, but not in such a way that it completely covers it, thus exposing only the solar corona.
Solar eclipses are very frequent, but they can only be seen from a specific point on the Earth, since the Moon is much smaller than the Earth. This means that a solar eclipse of some kind may be seen at the same point every 360 years.
lunar eclipse
In lunar eclipses, the Earth comes between the Sun and the Moon.The lunar eclipse, unlike the solar one, occurs when the Earth interposes between the Moon and the Sun, casting its shadow on it and obscuring it to some extent, always from a certain point on Earth.
The duration of these eclipses is variable and depends on the position of the Moon within the cone of shadow cast by the Earth, which is divided into Umbra (the darkest section) and Penumbra (the least dark section).
Every year between 2 and 5 lunar eclipses occur, which can also be of three types:
- Partial lunar eclipse. Just a part of the Moon is submerged in the cone of shadow that the Earth casts, showing itself slightly obscured or only obscured in some segment of its circumference.
- Penumbral eclipse of the Moon. It occurs when the Moon passes through the Earth's shadow cone, but only through the twilight region, that is, the least dark. This diffuse shade may slightly darken the view of the Moon or it can alter its color, going from white to red or orange. There are also cases in which the Moon enters only partially in the penumbra, reason why it is possible to also speak of partial penumbral lunar Eclipses.
- Total lunar eclipse. It happens when the terrestrial shadow completely obscures the Moon, which happens gradually, passing first from a penumbral eclipse to a partial one, then the total one, and again the partial one, the penumbral and the end of the eclipse.