Warp <war### [at] tagpovrayorg> wrote:
>   Lack of evidence is not evidence of the contrary. Just because a
> singularity has not been observed and measured doesn't necessarily mean
> that singularities cannot exist.

You would be right if you said that lack of *proof* is not *proof* if the
contrary. But lack of evidence (i.e. an observation that does not prove
something but still seems to support it) still is *evidence* (although maybe
not as strongly) to the contrary.

Lack of evidence that the invisible pink unicorn exists is some evidence that it
doesn't.

>   There are basically two choices:

I have made the experience that when someone presents just two choices, he's
typically overlooking something ;)

> 1) Assume that GR equations are correct in all situations, including
>    the extreme ones. There's little evidence to show that this wouldn't
>    be so. One consequence of this is accepting singularities, at least
>    until better evidence shows up.
>
> 2) Object to the notion of a singularity to be possible. This implies that
>    GR equations do *not* work in all possible situations, and that they
>    start to deviate in extreme conditions. However, no concrete evidence
>    of this exists, nor widely accepted alternative theories.

Or 3) Merely *question* the notion of a singularity being possible, drawing the
following conclusions:

* Assume that GR equations *may* be wrong in extreme situations like a
singularity, or even close to it; note that this may actually help *defend* GR
- because if we find that the singularity predicted by GR doesn't exist, we can
just interpret the singularity in the equations as saying that GR never
predicted anything (sensible) at all for these conditions in the first place.

* Take it as an incentive to search for other ways of seeing things, hoping to
come up with something that does the same job as GR (in all non-extreme
situations) but gives a non-singularity answer for the extreme situations. It
may actually be that we find a theory that has singularities somewhere else,
like - say - a point where there is no gravity (just a *very* wild speculation,
please don't jump on *this* one ;)), but otherwise gives sufficiently similar
results as GR does.

* Still, at the same time, without a tested superior theory, continue to use GR.


>   It may well be that singularities can not exist in this Universe, and
> that something else is happening with collapsing stars (stars do collapse
> due to gravity, which is something basically nobody doubts). However, as
> long as viable theories or, better yet, evidence of alternatives are not
> presented, science in general has to take choice #1.

No, science *must* take choice #3.


>   As far as I understand it, science is not about the Truth. The Truth may
> be impossible to achieve. Science is about the best we know so far. About
> getting as close to the truth as we can, by observing and measuring.

That's why #1 is stupid. The singularity problem is already an indicator that GR
*may* be wrong there, so why wait until this indicator turns to hard evidence
before starting to look for alternatives, when all experience suggests that
this indicator *will* turn to hard evidence (if the question can ever be
decided, that is)?

I'm not saying "trash GR, because it gives wrong answers for the center of a
black hole" - all I'm saying is "don't be *too* dogmatic about GR, and instead
keep your eyes peeled for fresh ideas, because GR gives *questionable* answers
for the center of a black hole."

Of course, when checking candicate alternatives, they need to stand a lot of
tests, and a lot will fail at them.

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