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From: PD on 28 May 2010 10:45
On May 24, 8:22 pm, Edward Green <spamspamsp...(a)netzero.com> wrote:
> How would one go about operationally defining radial and
> circumferential distances in the vicinity of a black hole?  Does it
> mean something to be "1 cm above the horizon"?

I believe the only real answer to that is to measure the circumference
of an orbit and to divide that by 2pi, or to measure the surface area
of a concentric sphere and to derive it from that.

It might mean something to be 1 cm above the horizon for an observer
local to the horizon, and it might mean something to an outside
observer using one of the methods described above, but those two
things won't be the same thing.
From: Tom Roberts on 30 May 2010 12:28
xxein wrote:
> On May 26, 7:55 pm, Edward Green <spamspamsp...(a)netzero.com> wrote:
>> On May 25, 10:54 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote:
>> [...]
> xxein: It's only a theory. Don't get your panties in an uproar by
> thinking you have learned a truth.

Of course! But note that this theory is really the only description we have of
black holes. So the original question was expressed in terms of this theory
(General Relativity), not in terms of observations or "truth" (whatever that
might mean).


Tom Roberts
From: Tom Roberts on 30 May 2010 12:31
PD wrote:
> It might mean something to be 1 cm above the horizon for an observer
> local to the horizon, and it might mean something to an outside
> observer using one of the methods described above, but those two
> things won't be the same thing.

As I said earlier, it does not mean anything. Distance "above the horizon" is
not well defined, because the relevant integrals diverge. You CANNOT measure
spatial distance relative to the horizon. In part because any ruler you lower
near to the horizon will disintegrate (lower parts of it fall in).


Tom Roberts
From: Tom Roberts on 30 May 2010 12:32
PD wrote:
> I believe the only real answer to that is to measure the circumference
> of an orbit and to divide that by 2pi, or to measure the surface area
> of a concentric sphere and to derive it from that.

Either procedure yields the value of the Schw. r coordinate. But that is not
distance.


Tom Roberts
From: Androcles on 30 May 2010 12:36

"Tom Roberts" <tjroberts137(a)sbcglobal.net> wrote in message
news:G5SdnVNWoM-zD5_R4p2dnAA(a)giganews.com...
| xxein wrote:
| > On May 26, 7:55 pm, Edward Green <spamspamsp...(a)netzero.com> wrote:
| >> On May 25, 10:54 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote:
| >> [...]
| > xxein: It's only a theory. Don't get your panties in an uproar by
| > thinking you have learned a truth.
|
| Of course! But note that this theory is really the only description we
have of
| black holes. So the original question was expressed in terms of this
theory
| (General Relativity), not in terms of observations or "truth" (whatever
that
| might mean).
|
|
| Tom Roberts

Roberts thinks wild speculation wrapped in algebra is "theory",
there isn't a snowball's chance in hell of him knowing the meaning
of truth.



|

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