One of the magical things about the Moon is
that the time it takes to spin on its axis is
exactly the same as the time it takes to orbit the Earth. In theory, therefore, on Earth we
should always see the same half, and only half,
of the Moon. Because Nature is not always that
simple, there are three reasons why, over time,
we can see more than half of the Moon’s
These effects are called librations and you can see them in this movie, which was created by taking an image of the Moon every day for a month and putting the images in a sequence. This is a great way to see not only the phases of the Moon, but also the wobbles (librations) it suffers during a month when viewed from Earth.