Does the moon rotate the same speed as the earth while oribiting around the earth?

Question

Does the moon rotate the same speed as the earth while oribiting around the earth?

Answer 1

No, the moon does rotate. Read this an it will explain it to you.

How it works: If you go out on several different nights and look at the Moon, you will always see the same features, at about the same position. It looks as if the Moon doesn't rotate! Ah, but it does.

This can be seen using a model. Grab two oranges (or apples, or baseballs, or whatever roughly spherical objects you have handy). Mark one with an "X"; this represents a feature on the Moon. Now put the other one down on a table; this is the Earth. Place the Moon model on the table about 30 centimeters (one foot) away with the X facing the Earth model. Now move the Moon model as if it were orbiting the Earth, taking care to make sure that the X faces the Earth model at all times.

Surprise! You'll see that to keep the X facing the Earth model, you have to rotate the Moon model as it goes around the Earth model. Furthermore, you can see you have to spin it exactly once every orbit to keep the X facing the Earth model. If you don't rotate it, the Moon model will show all of its "sides" to the Earth model as it goes around.

Now, I have been a bit tricky here. We are talking about two different frames of reference; one on the surface of the Earth looking out at the Moon, and one outside the Earth-Moon system looking in. You performed the experiment from the latter frame, and saw the Moon rotating. From the former, however, you can see for yourself the Moon does not rotate. What is being argued here is that in one frame the Moon rotates, in another it does not.

We've actually learned three things:

# 1) the Moon rotates as it orbits the Earth (as seen by an outside observer);

# 2) it rotates one time for every orbit (to that observer); and

# 3) if it didn't rotate, we would eventually see all of the Moon as it orbited the Earth.

Answer 2

It doesn't rotate, it orbits.