Sun, Moon and Earth Phases of the Moon It takes 29 and a half days for the Moon to complete one cycle of its familiar phases. Total eclipse of the Sun By a strange fluke of nature, the Sun and the Moon appear about the same size. Though the Sun is 400 times bigger, it is also 400 times further away. So when the Moon crosses directly in front of the Sun, the result is a breathtaking spectacle. Why eclipses aren't a monthly event The orientation in space of Earth and the Moon's orbit around Earth means that eclipses of the Sun and Moon can't happen every month. Orbiting the Moon in a lunar eclipse When there's an eclipse of the Moon visible from Earth, an astronaut at the Moon would see Earth eclipsing the Sun. Night and Day Day follows night because Earth is spinning around in space, turning from west to east. Seasons See how the tilt of Earth's axis works to cause our seasons to occur. See also: The Essentials The Planets Comets and asteroids Sights in the sky Spaceflight