Asked by denisa123 to Alice, Andi, Bas, Daniel, Rhian on 11 Mar 2015.
I think this is because as the moon moves around the Earth, it does not turn around on it’s own axis. so the side of the moon you see is the same everywhere as that side is always facing the Earth.
Apparently what we can see is about 59% of the surface of the Moon.
The reason for this, is the fact that the Moon and the Earth are “tidally-locked”. A very long time ago the moon used to spin around its axis much faster than it does now. But about 4 billions (!!) years ago the Earth and the Moon became tidally-locked, due to their own gravitational fields. So the Earth sort of “captured” the Moon in its own orbit and gradually slowed down its rotation (and in the same way, the smaller gravitational influence of the Moon creates tides on the Earth).
As a result of this interaction, now it takes the same time for the Moon to rotate around its own axis as the time that it needs to orbit around the Earth (about 29.5 days). This is the reason why it’s always the same part of the Moon’s sphere that is facing the Earth.
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