The rotation of the moon is locked into its orbital period of
the Earth so that we always see the same face of the Moon. The Moon's rotation
is believed to be locked to its orbit of the Earth due to the variation in
the distribution of mass in the Moon. The denser side of the Moon always faces
the Earth.
It is the rotation of the Moon with respect to the Sun that causes the phases
of the moon that we see from Earth. On the surface of the Moon though you
would experience the phases of the Moon in a very different way, What do you
think they might be?
Think about the following situation.
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If an astronaut landed at site A would it be light or dark in that location. On Earth there is no direct sunlight during the night, the same could be said on the Moon. The Moon has periods of light and dark like the Earth and these could be called its days and nights. |
| The next picture shows the Moon around 100 hours later the same location is marked on the Moon at point A. Note that the terminator has moved since the last time we saw the moon and it is now closer to point A. during all of this time it has stayed light at A. |  |
| It takes around 340 hours for the terminator to cross the surface of the Moon and for the Moon to change from a full Moon to a new Moon. Can you think of how long a Moon day would last? | |