When the Moon and the Sun are on opposite sides of the Earth , the Moon is in the sky all night with its bright side facing us. When the alignment is precise, the Earth's shadow falls on the Moon, partially or fully eclipsing it: the Earth's curved shadow slowly moves over the Moon, causing it to appear to change phases quickly.

During a total Lunar eclipse, the moon appears to progress through all its phases in a single night. The curved line of the Earth's shadow, however, is straighter than the line of the Moon's own curvature which we see during monthly phase changes. This gives an easily observable clue to the relative sizes of the Earth and the Moon. **************************************Back to Codex