Why is there a Dark side of the Moon? Why do we have tides?!
This question is more or less complete now, but it still lacks clarity and some animations. Use with caution.
Before we begin, let us make it clear that there is no such thing as a real dark side of the Moon; this is only a fancy name for the other side that we never get to see. But this dark side is as sunny as the one we can see. When there is a full Moon from here on Earth it is night in the opposite side of the Moon, and when there is a new Moon from Earth it is midday at the "dark" side of the Moon.
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But we still need to explain the real mystery here: why do we only see one face of the Moon? Is it chance? Is it that it does not rotate?
The Moon rotates just fine. Instead of explaining with words, here you have a nice gif image from Wikipedia:
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It is like dancing holding hands with a friend! But why is the rotation and translation of the Moon so perfectly synchronous? It is surely NOT a coincidence, since this synchronous movement is very common in the universe (there you have old Pluto and its moon Charon, for instance). This fenomenom is called tidal locking and in fact has to do with tides.
The pull of gravity will always produce some deformation of the planet or moon.
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