Re: OT: More about the universe and black holes

Could dark matter have been forged in a 'Dark Big Bang?'

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> Are planet-killing black holes hiding inside your cat?
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Hollow out the earth? Preposterous! No cavity can persist in the core of an object big enough to be drawn into the shape of a sphere under its own gravity.

Tiny black holes that would drill microscopic tunnels through matter wouldn't go unnoticed. I think they don't exist. For that matter, I think black holes, in the sense of gravitational singularities, don't exist either, for the simple reason that their mass energy, even though huge, is not infinite.

If a theory predicts a singularity, this merely tells us the theory is incomplete.

Jeroen Belleman

Indeed. It is possible that small sized black holes do account for some of the missing matter but you can't hide them so easily. If they were too low a mass they will already have evaporated by now from Hawking radiation. If there were a range of masse sthere should be some around evaporating right now and they would have a particular signature that GR can predict.

It is just possible that the next generation supercolliders might be powerful enough to momentarily create nano BH objects once in a bluemoon. Hyper energetic cosmic rays might do this too but their decay products are impossible to observe.

The theory could be complete if it only posits singularities in places where you can never observe them and report your findings. With the possible sole exception of a maximal angular momentum Kerr metric I think that Penrose's cosmic censorship conjecture holds.

It's a philosophical issue rather than a scientific one, but I hold that a science will have ceased to be one when it accepts things by declaring them unobservable. They might as well postulate the existence of fairies.

Jeroen Belleman

It may yet be possible to prove mathematically that they are. It is only one edge case that seems to still be a problem.

In general I agree that at some stage the next level theory will come along with some new mathematics where everything that we know at present can be derived as a weaker field limiting case.

However, at the moment the contenders like string theory look very cumbersome to use even if they actually worked!