How come the moon spins at the same speed it orbits around earth?

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It takes 27 days for the moon to spin completely and the exact same time for it to orbit around earth, thus creating a situation where we can always only see the same side of the moon.

Surely, this synchronization is not a coincidence but how exactly did we reach that point? I read some articles but found them vague.

In: Planetary Science

9 Answers

Anonymous 0 Comments

I think it’s easier to ignore the motion around the earth and just look at the moon rotating relative to earth. The earth will deform the moon slightly just like a ball rolling on the ground is deformed. With the rolling ball the deformation will be in front of the ball but the moon is deformed facing the earth.

Moving the deformation around the ball or the moon takes energy. This will cause the ball / moon to slow down to a standstill. (We ignore the friction).

Now add back the rotation around earth. The bulge doesn’t need to move so the moon doesn’t slow down (or accelerate) it’s motion.

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