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How much do you know about the moon?

By: Anna Norris on Sept. 16, 2013, 12:29 p.m.
Composite photograph of a lunar eclipse

Photo: Russ Wright/Flickr

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Lunar eclipse

A lunar eclipse occurs when the Earth perfectly blocks the sun's light from illuminating the moon in a straight-line, "syzygy" configuration. (This occurs during a full moon but is much less common, by the way.) When the moon passes through the Earth's umbra, it's a total lunar eclipse. Sometimes, the moon passes through the penumbra (the part of the Earth's shadow that isn't totally dark) for a penumbral eclipse, but total penumbral eclipses are rare.