Re: OT: More about the universe and black holes

On 04/12/2024 11:54, Jeroen Belleman wrote:

On 12/4/24 11:57, Jan Panteltje wrote:

Could dark matter have been forged in a 'Dark Big Bang?'
  https://www.space.com/second-big-bang-second-dark-matter
>
Are planet-killing black holes hiding inside your cat?
  https://www.space.com/primordial-black-holes-cat-big-bang

 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.

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.

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

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.
https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis
I don't know how strongly supported it is these days.
--
Martin Brown