What would it take to get the Moon rotating?

Suppose we want the Moon to appear to rotate from our perspective on Earth so we could see the dark side from here. What would that require? A pair of rockets on opposite points on the moon horizontally thrusting horizontally in opposite directions? How much thrust would be needed? Are there any nasty side effects from doing this?

Nitpick: We see the dark side of the moon every month. We can’t see the far side, however.

Thread title nitpick, although the text of your question seems to indicate you’re fundamentally aware of this fact: the Moon does rotate. Its rotation is locked to match its orbital period. It just doesn’t look like it rotates, from the perspective on Earth, because of the tidal locking.

So what you’re actually asking is what it would take to alter the Moon’s rotational period to not match its revolution period.

Huge solar sail on one side might help since you don’t need fuel. Additionally huge rotating gyroscopes could give it a nudge without ejecting mass, maybe get the moon into a oscillation so the little energy inputted into it would build on each other.

Double nitpick. It’s not the dark side now, but it was the ‘dark side’ until 1959.

That is kinds what he said in the first sentence. Still seems to be rather difficult to accomplish.

I wonder, is there some minimum acceleration needed to overcome the initial tidal lock?

Hamsters. Lots and lots of hamsters.

I’m not an astrophysicist/geologist, but I think it probably comes down to the moon’s material properties.

If you model it as a simple viscous material, then any torque placed upon it will achieve some initial acceleration that eventually tapers off as the tidal torque grows to offset the applied torque. Max rotational velocity occurs when tidal torque equals applied torque. Once the applied torque is removed, the tidal torque will eventually decelerate it until tidal lock is restored.

The fact that the moon is truly tidally locked to the earth suggests that the above model is oversimplified, and that there is some threshold torque below which the moon is able to resist the distortion that would otherwise be imposed by tidal forces. No idea how to calculate what the magnitude of such a torque would be.

Chuck Norris.

It’s never been the dark side. It gets illuminated regularly every month, in opposite synch to the side facing Earth.

What happened in 1959?

Luna 3, the first spacecraft to image the far side of the Moon.


Of course, the fact that it returned images proves it wasn’t the dark side of the moon at the time.

Luna 3sent back the first pictures of the dark side of the moon.

(and I’m going to keep on calling it that, all of you know what I’m talking about)

We knew that long before any spacecraft orbited the moon.

Dark also can mean hidden, secret, obscure. matter of fact, it’s all dark…

The Moon is massive enough that solar sails large enough to do this would be a far greater engineering challenge than any other plausible method of doing the job. And gyroscopes would only work temporarily: As soon as you stopped the gyros, the Moon would stop, too. To get any permanent change to the rotation, you have to couple to some other object, to transfer angular momentum between them.

What about just releasing the gyro’s into space?

The late Paul Birch of the British Interplanetary Society had a scheme for altering the rotational characteristics of a planet; it involves asteroids and magnets, and requires a lot of energy and time.

How to spin a planet (pdf)

You could, but then you might as well just release rocket fuel into space.

I have no idea what “dynamic compression units” are. This proposal appears to be using some sort of electromagnetic mass units that are sped up in some manner circling the sun (i.e. the solar windmill) and ejected on a path to the edge of Venus (or the Moon in our case), whereby they are “collected” in some sort of giant tube system so that they impact the surface and transfer momentum and torque to the planet.

I was going to try to calculate the energy required using angular moment of inertia, but it’s really hard to punch through on text editor.