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 It is an astronomical phenomenon in which the light of an incandescent star, such as the Sun, is totally or partially covered by another opaque star that gets in the way (known as eclipsing body) and whose shadow is projected on planet Earth. Its name comes from Greek ekleipsis: “disappearance.”
In principle, eclipses can occur between any set of stars, as long as the light and interposition dynamics described above occur. However, since there are no observers outside the planet, we generally talk about two types of eclipse: lunar or lunar eclipses, and solar or solar eclipses, depending on which celestial body is obscured.
Since ancient times, eclipses have fascinated and disturbed humans, whose ancient civilizations saw in them a sign of change, catastrophe or rebirth, if not a bad omen, given that most religions worshiped the Sun in one way or another.
However, these phenomena were understood and predicted by ancient civilizations equipped with astronomical knowledge, since they studied the recurrence of astral cycles in their various calendars. Some of them came to use them to distinguish between political, religious or social periods or eras.
See also: Phases of the Moon
Why do eclipses occur?
The logic of eclipses is simple: a celestial body comes between us and some light source, producing a shadow which can sometimes block a lot of the brightness. It is something similar to what happens when we cross 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.
Furthermore, they can be predicted with the help of a computer, for example, since we know the time it takes for the Earth to rotate around the Sun and around its axis, as well as the time it takes for the Moon to orbit our planet.
solar eclipse
The solar eclipse It occurs when the Moon comes between the Earth and the Sun, casting its shadow on a portion of the Earth's surface whose day is darkened for a few moments. This can only occur during a new moon, and can occur in three different ways:
- Partial solar eclipse The Moon partially shadows the Sun's light 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 completely obscured and an artificial night of a few minutes occurs.
- Annular solar eclipse The Moon coincides with the Sun in its position, but not in such a way that it completely covers it, thus leaving only the solar corona exposed.
Solar eclipses are very frequent, but they can only be seen from a specific point on Earth, since the Moon is much smaller than the Earth. This means that a solar eclipse of some type can be seen at the same point every 360 years.
See more in: Solar eclipse
lunar eclipse
The lunar eclipse, unlike the solar one, It occurs when the Earth comes between the Moon and the Sun, casting its shadow on it and obscuring it to some extent, always from some specific terrestrial point.
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 immersed in the shadow cone cast by the Earth, appearing slightly obscured or only obscured in some segment of its circumference.
- Penumbral lunar eclipse It occurs when the Moon passes through the Earth's shadow cone, but only through the penumbra region, that is, the least dark. This diffuse shadow can slightly obscure the view of the Moon or can alter its color, going from white to red or orange. There are also cases in which the Moon only partially enters the penumbra, so it is also possible to speak of partial penumbral lunar eclipses.
- Total lunar eclipse It happens when the Earth's 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 one and the end of the eclipse.
Continue on: Lunar eclipse
References
- “Eclipse” on Wikipedia.
- “The eclipses” (video) in La Eduteca.
- “Solar and lunar eclipses” at NASA Space place.
- “The eclipses” in AstroMía.
- “Solar eclipse” in GeoEncyclopedia.
- “Lunar eclipse” in GeoEncyclopedia.
- “Eclipse” in The Encyclopaedia Britannica.
