The phases of Venus

The phases of Venus

Fig. 7.1 . When fully illuminated, Venus looks small and far away; its apparent size is about seven times larger when the crescents are narrowest and Venus is nearest the Earth. After observing similar phases with his small telescope in 1610, Galileo wrote "Cynthiae figuras aemulatur mater amorum", or "The mother of love (Venus) emulates the figure of Cynthia (Moon). The phases and variation in the apparent size of Venus provided important early evidence that the planets revolve around the Sun rather than the Earth. (Lowell Observatory photographs.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University