# Will a small solid body spin forever in a vacuum?

Given a small solid body like a small asteroid or satellite and some initial slow spin, for example 1 rotation every hour.

If placed in a perfect vacuum with no external forces will this spin forever?

The classical solution (where we approximate the object with a rigid body) will conserve angular momentum.

Is this true even if we acknowledge that the object might over very long timescales be deformed due to internal gravity, loss of heat to the environment through radiation, or through radioactive decay?

Assume infinite time, don't let the lifetime of the universe be a constraint.

If it does slow down why? What is violating the conservation of angular momentum?

I have tried to read about this and am ending up with articles about beta decay and how spin relates to angular momentum but I am not sure this is the right track.

I also found this question

How to model energy loss in a rotating body?

But this asks about modeling and I did not see the answer to my question among those answers.

## 1 Answer

At the very least, a neutrally charged object that is rotating and is NOT a uniformly rotating axially symmetric body produces gravitational waves which clearly is a loss mechanism. Therefore, after some time, it will lose its entire energy.

Refer to Do rotating bodies emit gravitational waves? and https://www.ligo.caltech.edu/page/gw-sources for more details.

• Well, this does not happen in the hydrogen atom. But perhaps this is "too small" for the OP. Commented May 26, 2020 at 16:40
• Hmmmm. I have to admit I did not think about that. But then again, it is a little hard, for me at least, to even imagine what "rotation" means for a single hydrogen atom. The mechanics, most likely, does not resemble what we associate with the concept of rotation Commented May 26, 2020 at 16:42
• @user2820579 see physics.stackexchange.com/questions/271203/… and this physics.stackexchange.com/questions/92173/… Commented May 26, 2020 at 18:02