Repost: Understanding Moon Phases

The upcoming third six weeks science curriculum in Dallas ISD turns its focus to the moon and other celestial objects (in most grades).  I’ m going to re-run Earth & Sky’s excellent series of articles on the moon’s phases through the end of 2011.

In conjuction with tomorrow’s New Moon, we begin with a nice, concise, relatively clear explanation of the changing phases of our moon:

Why does the moon seem to change its shape every night?

The answer is the moon is a world in space, just as Earth is. Like Earth, it’s always half illuminated by the sun. In other words, the round globe of the moon has a day side and a night side. From our earthly vantage point, as the moon orbits around Earth, we see varying fractions of its day and night sides. These are the changing phases of the moon.


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