• OT: More about the universe and black holes

    From Jan Panteltje@21:1/5 to All on Wed Dec 4 10:57:36 2024
    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

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  • From Bill Sloman@21:1/5 to Jan Panteltje on Wed Dec 4 22:54:39 2024
    On 4/12/2024 9:57 pm, 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

    Somebody hasn't heard of Hawking radiation.Stephen Hawking worked out
    that black holes had to evaporate, and small black holes had to
    evaporate quite fast.

    https://en.wikipedia.org/wiki/Hawking_radiation

    --
    Bill Sloman, Sydney

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  • From Jeroen Belleman@21:1/5 to Jan Panteltje on Wed Dec 4 12:54:59 2024
    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.

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

    Jeroen Belleman

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  • From Jan Panteltje@21:1/5 to jeroen@nospam.please on Thu Dec 5 07:13:34 2024
    On a sunny day (Wed, 4 Dec 2024 12:54:59 +0100) it happened Jeroen Belleman <jeroen@nospam.please> wrote in <vipfn9$rmtm$1@dont-email.me>:

    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.

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

    Yes, divide by zero people, but then again,
    we do not know the size of an electron.,
    so small, so it could be a black hole like thing,
    same for some other elementary particles.
    If you look at the scale of things, from planets orbiting stars
    to electrons orbiting atomic nuclei,
    to galaxies orbiting what we call black holes
    there could well be a repeating pattern going down-scale so to speak,
    also going up-scale multiple universe / big bangs.

    We need a mechanism to explain things, and that gives you one.

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  • From Martin Brown@21:1/5 to Jeroen Belleman on Thu Dec 5 09:34:15 2024
    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

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  • From Jeroen Belleman@21:1/5 to Martin Brown on Thu Dec 5 23:37:15 2024
    On 12/5/24 10:34, Martin Brown wrote:
    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.


    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

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  • From Martin Brown@21:1/5 to Jeroen Belleman on Fri Dec 6 09:14:26 2024
    On 05/12/2024 22:37, Jeroen Belleman wrote:
    On 12/5/24 10:34, Martin Brown wrote:
    On 04/12/2024 11:54, Jeroen Belleman wrote:

    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.

    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.

    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!

    --
    Martin Brown

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