Solar eclipses occur when, from our perspective, the moon moves in front of the sun, blocking some or all of its light.
Partial Eclipses
Because from the Earth, the sun and moon appear approximately the same size, most eclipses often appear “partial”, which is to say, only part of the sun is covered by the moon (see illustration below).
During a partial eclipse, the moon is dark, because the sun is directly behind it, meaning that its illuminated “day” side is not visible from the earth. Any light that still comes from the moon is outshone by the sun (see illustration below. The Earth and Moon are shaded to indicate day and night sides, but are not to scale).
For this reason, the moon will not be visible during a partial eclipse, and rather, the sun will appear to have a bite taken out of it.
Image of partial solar eclipses, Wikimedia Commons
Total Eclipses
Occasionally, however, the moon will be directly between you and the sun, and block it entirely. This is called a total eclipse. In a place where such an eclipse is visible, the eclipse will begin as partial, and gradually the part of the sun blocked by the moon will grow until the entire sun is covered. During total eclipses, the sky will become dark enough to see stars, and the temperature will drop, causing wind much like a sunset would. This is also the only time it is safe to look directly at an eclipse. During this time, the moon may also be faintly visible due to light reflected from the Earth. A ring of light, known as the corona, will become visible; this is the sun’s atmosphere which extends out enough to be visible around the moon.
Image of total solar eclipse, Wikimedia Commons
Annular Eclipses
There is also a third type of eclipse, known as an annular eclipse. These occur because, due to the Earth’s slightly varying distance from the sun and moon, the moon will sometimes appear slightly smaller than the sun, and will thus be unable to cover it completely. In this situation, when the moon would otherwise cause a total eclipse, a thin ring of sun is still visible around the moon’s shadow (see images below).
Photograph of an annular eclipse, Wikimedia Commons
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