Re: cosmology and quantum gravity

[Jack Uretsky <jlu@HEP.ANL.GOV>]

        Forgive me, please, for being inarticulate.  I thought that I was
clear in restricting my comments to the mathematical blowing up.
        Let me try again:  the description of gravity in the conventional
(Schwarzchild) coordinates requires the coordinates to have a singularity
at the event horizon.  I was silent as to the physical consequences of
that singularity, which requires an interpretation in the language of
clocks and measuring rods.
        David Bowman has now described at some length the consequences
of approaching and crossing over the event horizon.  Implicit in his
discussion is the fact that there is physics involved in setting up a
coordinate system, because the coordinate system implies the manner of
making time and distance measurements.
                        Regards,
                                Jack


Adam was by constitution and proclivity a scientist; I was the same, and
we loved to call ourselves by that great name...Our first memorable
scientific discovery was the law that water and like fluids run downhill,
not up.
                          Mark Twain, <Extract from Eve's Autobiography>

On Sat, 29 Apr 2000, Glenn A. Carlson wrote:

> I agree with Mr. Rauber.  If the "gravitational effect" referred to by
> Mr. Uretsky is simply the "blowing up" of the metric at the event
> horizon, I question calling this coordinate singularity a
> "gravitational effect."  As Mr. Rauber correctly points out, "there
> are no *physical* effects that blow up at the event horizon."
> [Emphasis added.]  Gravity is physical.  The coordinate singularity is
> not; it's purely mathematical.
>
> Perhaps, Mr. Uretsky can clarify what is the "gravitational effect" to
> which he refers.  Is it physical or mathematical?
>
> Glenn A. Carlson, P.E.
> gcarlson@mail.win.org
>
> > Subject: Re: cosmology and quantum gravity
> > Date: Fri, 28 Apr 2000 14:48:25 -0500
> > From: Jack Uretsky <jlu@HEP.ANL.GOV>
>
> > In the
> > usual metric, the gravitational effects get larger and larger as we
> > approach the black hole until they blow up at the horizon, where there is
> > a coordinate singularity.
>
>
> > Subject: Re: cosmology and quantum gravity
> >   Date: Fri, 28 Apr 2000 17:18:42 -0500
> >   From: Joel Rauber <Joel_Rauber@SDSTATE.EDU>
> >
> > I must reiterate, there are no physical effects that blow up at the
> > event horizon of a Schwarzchild black hole, at least in the usual physics
> > sense of the words "blow up", which I interpret as loose language for
> > diverging to infinity.