"Jan Panteltje" wrote in message ...
On a sunny day (Fri, 5 Jan 2007 09:31:03 -0500) it happened "Greg Neill"
wrote in
:

"Jan Panteltje" wrote in message
...
If you move to the centre of a black hole, where gravitational forces sort
of cancel, can light and normal matter exist in some area there?

Gravitational forces don't cancel because the mass of a
black hole (except for the infalling matter from its
"feeding") is located at a singlularity at the center.

But why? image for a moment matter falling into a body.
As its mass increases, the escape speed from it will increase.
At some point the escape speed will be greater then C, so light cannot escape,
we no longer see any EM waves coming from it, we call it a black hole
(is this correct?).

There is nothing that says that the thing could not be a bit hollow, its being
black only depends on the escape speed.

(I could imagine somebody compressing an object, to comprss it all the
way to the center may be prevented by the outer layers becoming too strong).

A black hole forms when the pressure due to self-gravitation
of the constituents exceeds the support capability of these
constituents. That is, when the inward pressure exceeds the
electron degeneracy pressure of matter, there is nothing
that can prevent gravity from "winning" and collapsing the
matter to a singularity (nothing, that is, that we currently
know about). There is no known from or state of matter that
can withstand the pressures created by gravity at the extremes
of a black hole.



Gravitational acceleration and tidal forces increase
without limit as you approach the center.

Nobody has been or even measured anything there via remote methods.
So that would be a postulate, creating nasty infinities.
Nature does not accommodate infinities :-)

That, too, is a postulate! Since we haven't been there, we
cannot know. General Relativity, which should hold true until
very close to the purported singularity, indicates that the
end of all matter entering the black hole will be to end at
a singular point at its center.


Or does the black hole simply get denser when you move towards it center,
as opposed to haveing a center with a dense shell around it (black egg)?

There's no shell. The event horizon is about as substantial
as a property line; it just demarkates the boundary beyond
which there's no escape.

I agree with that (except for 'evaporation' of particles).

One could speculate that the same process that generates
the particle pairs for Hawking Radiation might increase
in effect as one approaches the singularity, so that rather
than being devoid of matter between the horizon and singularity,
the mass is spontaneously and continuously being recycled
close to the singularity as particle pairs. So the
space inside could be populated by a continuously annihilating
soup of particles which increases in density towards the
center.