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The Moon

The moon goes through pahses cahgrs why?


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November 19, 2010 3:12AM

The phases of the moon depend on the relative positions of the earth, moon and sun. The moon orbits around the earth once every 27.3 days. Since this causes the relative positions of the three bodies to be changing over the course of a month, the phase of the moon changes. Think about the fact that the earth is rotating on its axis quite a bit faster than the moon is orbiting around earth. The portion of the moon that is lit by the sun changes over the course of a month, because what we interpret as a month is really a "moon day". We are watching the progression of sunlight as it moves across the face of the moon, one full cycle each month.