Natural Science Forum / Physics / Relativity / October 2005

You are not right if you think that time stops in black holes.

There are no physically infinite things in the universe.  Black holes
exist independently of any infinite red shift, they are caused by the
accumulation of matter large enough that the gravitational force
exerted by the matter causes the surrounding space to distort and fold
back into itself.  Other than by Hawking radiation, matter and energy
cannot escape from a black hole.  But at the centre of a black hole,
the gravitational force, although extremely high, is not infinite.

Some theorists predict that our currently expanding universe will
expand forever, others that all the matter in the universe will
eventually collapse into one single black hole, with a "singularity" at
the end of the universe.

In the collapsing universe, all the space in the universe would also
end up folded into the black hole, and the universe would consist of
nothing but a vanishingly small 'dot', but even then, the gravitational
force would not be infinite, because the universe is not infinitely
large to begin with.

If, at the end of the collapsing universe scenario, the dot decreased
by half its size each second, it could continue to do that forever,
space-time would never cease to exist, and time would never stop.  Some
theorists reckon that the rate of collapse would accelerate, so for
example, the dot might take 1/2 a second to reduce in size by half,
then 1/4 of a second to reduce in size by half again, and at intervals
of 1/8, 1/16, 1/32 seconds and so on by half each time.  At the end of
1 second of this accelearting rate of collapse tne 'dot' at the end of
the universe would actually vanish!  Only then could one describe time
as having 'stopped', as spacetime would no longer exist.

Inside an ordinary black hole, time exists as per usual, as does the
space around it.