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If accelerating reference frames can be treated as normal inertial reference frames but with gravity, then for a rotating reference frame, is the centrifugal force = gravity? More specifically, I was reading about Mach's Principle as it was called by Einstein. When we spin and feel our arms fly, is it due to gravity caused by the rotational acceleration?

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    $\begingroup$ Mach's principle is one of the most infuriating topics in physics. It's a very, very easy thing to get wrong, or at least, there are so many interpretations of it that it's unclear whether you're getting it wrong, or the principle is just incorrect, despite being inspirational to Einstein. $\endgroup$ – Jerry Schirmer Feb 20 '16 at 0:36
  • $\begingroup$ en.wikipedia.org/wiki/… $\endgroup$ – Wolpertinger Feb 20 '16 at 1:29
  • $\begingroup$ i remember when we thought the earth was flat. if i was in a wheel shaped space station (like 2001) and it was large enough that i thought i was on flat ground, could i perform newton's experiments and come up with the same laws, or results? this is a rhetorical question. $\endgroup$ – chaz327 Feb 20 '16 at 15:12
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No, it is due to centrifugal force. Even if you go to deep space, where there is no heavy body around that would cause gravity, and spin, you will still see/feel your arms fly. I am not sure though how you will be able to spin yourself in deep space.

But then theories consider gravity and any other acceleration equivalent. In that sense, one can call it gravity but I think it will be a stretch.

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  • $\begingroup$ i would have used centripedal force, but you're not wrong $\endgroup$ – chaz327 Feb 20 '16 at 15:01
  • $\begingroup$ @kpv the principle of equivalence states that any accelerating reference frame mimics gravity perfectly and is absolutely equivalent. then when we spin, there is definitely a gravitational effect. However, I'm trying to figure out if this gravitational effect is what causes our arms to fly (coz I feel our spinning will produce a very feeble gravitational field, not enough to raise our arms).This problem aside... is there any explanation of psuedo forces in general relativity $\endgroup$ – Aditya Alur Feb 21 '16 at 19:36
  • $\begingroup$ There must be an explanation in GR. But this example is so simple that GR would reduce to normal circular Newtonian motion, which can be understood as result of tangential speed causing the fly out effect. The equivalence principle states that it is not possible to distinguish between acceleration and gravity in a closed box. It does not say that every acceleration is gravity. This effect is not caused by gravity in any sense. If at all there is a tiny effect due to increased gravity because of rotation, that effect should be opposite of fly out. You can neglect that effect. $\endgroup$ – kpv Feb 21 '16 at 19:45

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