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Revision as of 16:27, 13 December 2002 by Montrealais (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)From Earth, a lunar eclipse occurs when Sun, Earth and Moon are in a single line with Earth in the middle. If this occurs, the Moon (or part of it) does not receive light from the Sun because it is in the shadow of the Earth, and thus the Moon becomes invisible even though there would normally have been a full moon. Most of the light that passes through the Earth's atmosphere is red, and thus an eclipsed Moon will glow in reddish hues.
A penumbral eclipse occurs when the Moon passes through the Earth's penumbra only. In such a case the Moon still looks full but appears dimmer. A total lunar eclipse occurs when the Moon travels completely into the Earth's umbra. If only part of the Moon enters then umbra, then there is a partial lunar eclipse.
Lunar eclipses are only possible during a full moon, when the Moon is directly opposite the Sun. The Moon is usually above or below the ecliptic, however when it does align, with the ecliptic, an eclipse may occur!
Unlike a solar eclipse, which can only be viewed in a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere where the moon is visible.
If you were on the Moon during a lunar eclipse you would witness a solar eclipse.
The Moon's speed through the Earth's shadow is about 1km per second (3600km per hour) and the longest the Moon will remain completely within the Umbra is 102 minutes.
History of Lunar Eclipses
Ancient Greeks noticed that during lunar eclipses the edge of the shadow was always circular. They thus concluded that the Earth was spherical.
See also: eclipse, solar eclipse