What Is a Lunar Eclipse?

A lunar eclipse can only happen at night because a lunar eclipse is when the Moon gets eclipsed, which means the Earth is in between the Moon and the Sun. The Earth casts its shadow on the Moon because Earth blocks the rays of light coming from the Sun. You can remember this by thinking of "moonar" eclipse because it sounds like "lunar" eclipse.  That doesn’t exactly mean you can’t see the Moon, though. It means the Moon turns red. The light rays can sometimes bend (refract) or bounce around the Earth’s atmosphere. Particles make up our atmosphere, which causes the light to bounce around or bend through the atmosphere. Then the Moon gets just enough light to be seen, but the Moon appears to be red because our atmosphere had blue components in it. So when we look through the atmosphere, we’re also looking through the blue component, which causes the redness of the Moon. If the Moon ended up not getting any light, then it would be pitch black because the Moon doesn’t produce its own light.

There’s an average of only two lunar eclipses a year, but one year there were five eclipses! Lunar eclipses last for about one to two hours. Lunar eclipses can only happen when there’s a full moon because this is the only time when the Sun, Earth, and the Moon are lined up in that order. There isn’t a lunar eclipse every time there’s a full moon, though. The Moon generally orbits either higher or lower around the Sun than the Earth orbits around the Sun. This means the Moon doesn’t have the same orbit around the Sun as Earth does, so they're not all three exactly lined up.

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All pictures courtesy of NASA unless otherwise noted