Re: GR -> Black Holes Can't Form... Take 2
From: Ken S. Tucker (dynamics_at_vianet.on.ca)
Date: 02/14/05
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Date: 14 Feb 2005 15:09:37 -0800
carlip-nospam@physics.ucdavis.edu wrote:
> In sci.physics Ken S. Tucker <dynamics@vianet.on.ca> wrote:
>
> > carlip-nospam@physics.ucdavis.edu wrote:
>
> [...]
> >> In particular, the "radar distance" to r=2m is infinite.
> >> This should be obvious -- it's the result of the infinite
> >> time dilation. But even if you stay well away from the
> >> horizon, he "radar distance" is most certainly not the
> >> Schwarzschild coordinate r.
>
> > It's complicated, but I think we'll
> > need to adopt do standard, I suggested
> > one.
>
> The whole point of general covariance is that you can use
> any coordinate system you want,
No sir, I think that's not true in physics.
For example, in general tensor analysis you
can have an absolute spatial displacement
given by, {i=1,2,3|
dx_i dx^i =/=0, (absolute spatial displacement).
But relativity imposes a condition on this
equation and says *absolute motion* vanishs.
Then a constraint is imposed upon GC,
dx_i dx^i =0 (1)
which means absolute displacement vanishes
and only relative displacement remains.
So now we're left with choosing CS's consistent
with (1).
I'll stop here, awaiting Dr. Carlips reply.
>as long as you are careful in
> the end to compute results of real physical observations. But
> if you want to use "radar distance" and choose coordinates
> that have a direct physical meaning in terms of trajectories
> of light, that's fine. The coordinates you end up with are
> called Eddington-Finkelstein coordinates if you restrict to
> only ingoing or only outgoing light rays, or Kruskal-Szekeres
> if you use both.
>
> So by all means, go learn the Schwazschild metric in Kruskal
> coordinates. You will find that it clears up a lot of your
> confusion.
Dr. Carlip, I respect your record of publications
on BH's in arXiv, and do I do respect the excersize,
but question does remain, are BH's physically real?
> Steve Carlip
Happy Valentines, hope you get @^@%#$$
Ken
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