Why does it take the moon phases 29.5 days to complete on full cycle?
The moon orbits around the earth every 29.53058868 days. It orbits in the same direction that the earth turns. Since the moon is in a much higher orbit than a geosynchronous satellite (which orbits with us every day and stays in the same position in the sky) its orbit is very slow. The moon appears to move across the sky at nearly the same speed as the sun, but just a bit slower. Personally I remember that the sun is faster because of a Greek myth about Helios, the sun, chasing after Selene, the moon.
