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This is a bit a bit of a weird question. Simply put, if a body such as a planet spins, there is no internal issue (that I know of) that would cause it to eventually stop (by internal I mean that an external force can't be applied as an example). I'm assuming the reason this 'perpetual motion machine' fails is one of the following:

  • The laws of thermodynamics do factor in external issues (because those laws are what prevents perpetual motion).

  • This would only work if every object could maintain their general structure (proton decay, Hawking radiation etc would pretty much decay the system) and the laws of physics say that they cannot.

To reiterate because I see this a lot: I'm not asking if this is a perpetual motion machine, I'm asking why it isn't.

Related: How does physics deal with perpetual motion in orbits?

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  • $\begingroup$ Have you studied the effects of frame dragging? $\endgroup$ – Adrian Howard Oct 14 '20 at 18:07
  • $\begingroup$ Why do you think Quillo's answer to your previous question doesn't apply (with straightforward adaptions) to this question? $\endgroup$ – The Photon Oct 14 '20 at 18:19
  • $\begingroup$ He himself said that the answer would be quite different. I'm not quite sure how GW would apply $\endgroup$ – yolo Oct 14 '20 at 18:22
  • $\begingroup$ No, I'm not familiar with the concept of frame dragging $\endgroup$ – yolo Oct 14 '20 at 18:22
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    $\begingroup$ But the main point, that perpetual motion machines of the third kind are only impossible (in classical mechanics) because of friction, and it is indeed possible to make spinning systems with very low friction. In the case of a rotating body in space the only friction would be between the outer surface of the body and the surrounding medium. So a rotating body in the interstellar medium will remain rotating for a very, very long time. $\endgroup$ – The Photon Oct 14 '20 at 19:14

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