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Is rotational motion relative to space?

Assume a universe with the same physics as ours, but containing only one rotating (charge-free) body - let's say the size of the Earth. Would the rotation cause a bulge at the equator of the rotating body?

Qmechanic
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frank baumann
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  • +1. ..I was about to comment with side question how will gyroscopes react to the turns then got a brain freeze –  Jun 03 '12 at 21:52
  • Why not? In our universe, what's the answer and why? – Chris Gerig Jun 03 '12 at 22:32
  • I really feel that knowing this part will make me a better human and citizen. May be it is more relevant to some 18th century study, but it will be so nice to see the understandable answer. –  Jun 03 '12 at 22:40
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    Einstein may give Mach some credit for molding his thinking, but Einsteins theory's put Mach's ideas firmly in the trash bin. Einstein tells us that physics is local, so Mach can take a flying leap as his arguments revolved around a purely non-local argument. – dmckee --- ex-moderator kitten Jun 03 '12 at 22:43
  • What do you mean by rotating? ...rotating with respect to what? – hpekristiansen Jun 03 '12 at 22:55
  • Since it's rotating around itself, and since it's a massive object (so there's gravity), then I guess yes. There will be an equatorial bulge. – stupidity Jun 03 '12 at 23:40
  • I'm tempted to say the answer to the question is 'no', in the sense that you can't really talk about rotation unless there is other matter present in the universe. Mach's principle, as interpreted by Einstein in GR, relies on the presence of distant matter to make sense of rotating reference frames. – kleingordon Jun 04 '12 at 00:22
  • @kleingordon umm, if we were part of that rotating body, can't we use a Foucault pendulum to talk about its rotation around itself? (I'm talking classical physics. I don't know how to think about this problem in terms of relativity.) – stupidity Jun 04 '12 at 00:36
  • This has been asked many times before. http://physics.stackexchange.com/questions/1372/is-rotational-motion-relative-to-space http://physics.stackexchange.com/questions/3986/newtons-bucket http://physics.stackexchange.com/questions/13008/inertia-in-an-empty-universe http://physics.stackexchange.com/questions/13767/how-are-accelerated-reference-frames-non-symmetrical/13768#13768 http://physics.stackexchange.com/questions/173/is-acceleration-an-absolute-quantity http://physics.stackexchange.com/questions/1048/what-if-the-universe-is-rotating-as-a-whole – Mark Eichenlaub Jun 04 '12 at 01:42

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