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

133 viewsOtherPlanetary Science

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

It’s called [Tidal Locking](https://en.m.wikipedia.org/wiki/Tidal_locking). It occurs because when the moon is rotating on its axis at a different speed than its orbit, it causes the sphere to deform just a little bit, causing bulges in its shape as it rotates about its axis. Movement in these bulges require energy and are released as heat in the moon’s interior. This energy comes from the moon’s angular momentum (rotational energy) and slows its spin down over time as it is dissipated as heat. Eventually, after millions of years, the moon’s spin slows to a point where it no longer spins faster than its orbit with the earth. Since it now spins at the same rate as its orbit, the bulges caused by the gravity of the earth acting on it are locked in place and no longer move across the moon’s body and no longer generate heat, and therefore, no longer slow the spin of the moon.

Hopefully this makes sense. If not, the Wikipedia article I linked above should help explain further.

You are viewing 1 out of 9 answers, click here to view all answers.