Warp wrote:
>   The major objections against singularities are more or less philosophical,
> rather than based on hard science. It's "hard to believe" that mass could
> be compressed into a point of zero volume.

I think that maybe used to be the case, but I think the objections are also 
that it's in conflict with QM right now.

>   If someone objects to the notion of a singularity, he would have to show
> some evidence that GR doesn't work as predicted in this case.

I thought that's why it's called a singularity? :-)

 > There must be
> some property of the Universe which makes GR not work in this situation,
> something which actually stops the singularity from forming. What could this
> phenomenon be? Has anyone ever measured such phenomenon to exist?

QM uncertainty, and symmetry rules that indicate you can't lose information 
about individual particles. You *can't* compress something down to zero size 
and not know both where it is and how fast it's moving, for example. QM also 
says you can't have two fermions in the same quantum state in the same 
place. (More precisely, the probability that it happens is zero, once you 
add up all the possible virtual paths.) Hence, you can't collapse an entire 
star into a single point.

I don't think the objects are just "it's hard to believe". It's just that 
nobody knows how to resolve the problem, since the incompatible theories 
both satisfy all the experimental evidence gathered so far.

>   The thing is, if GR equations are right, and there is a lot of evidence
> suggesting that they are,

... at the macroscopic level ...

But a singularity is, by definition, microscopic. :-)

> There's no known way for matter/energy to stop going towards this center. 

You wouldn't think a single electron could be larger than a house, either, 
but they've done that in a laboratory.

I think the real answer is that people just don't know yet. GR says one 
thing, and every experimental investigation we can do matches GR. QM says 
another thing, and every experimental investigation we can do matches QM. 
However, we don't have the capability (yet) of doing any experiment that 
would encompass both GR and QM in the same experiment that would give 
different answers in the area where they conflict.

Now, what would be fascinating would be for someone to come up with an 
experiment that proves you can't measure things in a way that would make QM 
and GR conflict. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

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