> David Feuer writes:
> > In general relativity, it is impossible to tell whether you are rotating,
> >
> > or whether the universe is rotating about you.
> >
> > If the universe rotates about you, the gravitational waves produced by all the other matter in
> >
> > the universe will conspire together to produce the same effects as if you were rotating.
>
> The point is that pseudo-gravity induced by acceleration (whether
> you consider the universe as accelerating with respect to you or
> you accelerating with respect to the universe) produces a field
> qualitatively different from the spacetime curvature induced by
> mass; they are easily distinguished by observation. Only in the
> infinitesimal limit may you consider them as having identical
> effects.
>
> However, I am far more familiar with special relativity than
> general relativity:
>
> http://hexadecimal.uoregon.edu/relativity/
Me too. I've read huge bunches on special relativity (Maxwells's equations, four-vectors, etc.) but
practically nothing on general relativity. If I remember correctly (doubtful), I said this in
response to the following:
> "Centrifugal force" doesn't exist. It's the apparent "force" directed away
> from the center of rotation which appears to be pulling the rotating object
> directly outward from the center; in fact, it's actually the object's
> momentum trying to carry it in a straight line (at a tangent to the circle,
> not normal to it). Since for short distances the tangent is fairly close to
> the circular path resulting from the application of centripetal force to the
> object, it "feels" like a force directly away from the center.
>
My point (IIRC) was that in GR, the apparent centrifugal and centripetal forces could in fact be
true gravitional forces due to the rotation of the entire rest of the universe. One can take the
frame of reference of the "fixed stars", in which the space-ship is spinning and the centrifugal
force is a virtual force, or one may take a frame of reference fixed to the ship and consider
everything else to be spinning. That spinning of huge masses at tremendous distances leads to just
the right gravitational waves to produce the same effect, or so I have been told (by one who should
know).
--______________________________ / David Feuer \ | dfeuer@binx.mbhs.edu | | feuer@his.com | \ david@feuer.his.com / -----------------------------
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