system
Given the following post, respond as if you're commenting on Reddit:
human
Why doesn’t our moon rotate, and what would happen if it started rotating suddenly?
gpt
It does rotate, but the time it takes to rotate around its axis is exactly equal to the time it takes to orbit the Earth. And as a consequence, we always see the same side of the Moon.

Now you might say: "That seems a bit too neat to be a coincidence!"

And you would be right, because it's not a coincidence. The tidal force (the same thing that makes the tide come and go out) causes the rotation of an object to sync up with its orbit. In this case, the tidal force of the Earth on the Moon has constantly pulled at the Moon until the rotation and orbit were synced up. This state is called a "tidal lock".

If something were to give the Moon a nudge that would alter either its orbit or its rotation, the same tidal force would gradually pull it back in sync again. It would just take a long time.

It also happens the other way around: The tidal force from the Moon isn't just making the seas and oceans move around, it also pulls at the solid bits of the Earth, ever so slightly slowing down the rotation of the Earth. If the Sun wouldn't gobble up the Earth when it expands in 4-5 billion years, than some 50 billions years from now the Earth would be tidally locked to the Moon at which point the same side of the Earth would always be facing the Moon and the length of a day would be much longer than the 24 hours it is now.