The Moonís varying appearance

The Moonís varying appearance

Fig. 1.3b . During the monthly cycle, the illuminated part of the Earthís Moon waxes (grows) from crescent to gibbous, and then after full Moon, it wanes (decreases) to a crescent again. The term crescent is applied to the Moonís shape when it appears less than half-lit; it is called gibbous when it is more than half-lit but not yet fully illuminated. The reason for the Moonís changing shape is described in Figure 1.8. (Lick Observatory Photographs.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University