The Rhythmic Sky Page 7

2. Orbit of the Moon

In the days of Giordano Bruno and long before that, the common view was that all “heavenly bodies” revolved around the Earth. In one case that was correct, the Moon indeed orbits the Earth. That is a definition of a moon (and we have many moons in the Solar System): it is an object that orbits around a planet.

The moon orbits the Earth in the same direction as the Earth rotates.

This animation also explains the phases of the Moon as seen from Earth. We can only see the part of the Moon that is illuminated by the Sun,
which most of the time is a crescent form and sometimes completely dark (new moon) or completely illuminated (full moon).

It takes the moon about one month (29.5 days) to complete one revolution around the Earth.

Because of the Moon's orbit, we see the Moon in different positions in the sky with respect to the stars. About half a month we see the Moon at night, and during the other half we see it during the day.


Animation Freedman and Kaufmann http://bcs.whfreeman.com

Note that you see the Moon phases in the inset as seen from the Northern Hemisphere! On the Southern Hemisphere you see this upside down. Read more about this here.