The American Heritage® Science Dictionary
Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Search Images
Half of the Moon is always in sunlight, as shown on the left. The relative positions of the Earth, Moon, and Sun determine the Moon's phase as seen from the Earth, as shown on the right.
David Mackay Ballard
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