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Entire universe ending with a supermassive black hole?

  1. Mar 20, 2015 #1
    Black holes grow by absorbing matter, which includes galaxies and black holes. Would the growth of black holes overtake the expansion of space time and collapse the entire universe?
     
  2. jcsd
  3. Mar 20, 2015 #2
    It is one conceivable scenario that the entire mass of the observable universe could in the distant future = trillions of trillions of years - all end up inside one black hole.
    That would eventually evaporate as radiation according to Stephan Hawking.
    There isn't any reason I know of though, to suppose that the universe in such a state would do anything to halt or reverse the expansion of space.
    Space would still exist but other than the black hole it would be devoid of any kind of matter.
    A black hole cannot collapse - it already is in a collapsed condition.
     
    Last edited: Mar 20, 2015
  4. Mar 20, 2015 #3

    Drakkith

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    No. Black holes are very small objects and the distances in space are extraordinarily large. Compressing all of the mass of the Milky Way into a single black hole would result in a black hole that is a tiny, tiny fraction of the Milky Way in size. In addition, to stop the expansion of the universe we would need more matter/energy to create more gravity that would slow and eventually reverse the expansion. But even including dark matter we don't have enough. The creation of a black hole does not create more gravity, it simply concentrates it. For example, if the Sun were compressed into a black hole, the planets would continue in their orbits as if nothing had happened.
     
  5. Mar 20, 2015 #4

    Chronos

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    It is deemed possible that all matter could, in the distant future, reside in black holes. Galaxies may someday be consumed by black holes, but, that is the extent of it save for the occasional merger with a neighbor. As Drakkith noted, this would be a strictly local phenomenon with no affect on the universe at large.
     
  6. Mar 21, 2015 #5
    Thanks guys now I have a deeper idea of black holes :)
     
  7. Mar 21, 2015 #6

    FRK

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    it is possible but on opposite condition that the expansion of space-time overtake the growth of black hole means by the entropy of time ,space more and more expand like a sheet losing its thickness which may lead to more growth of black hole and by emerging in one another the whole mass of universe return to big bang singularity
    hence the universe collapse,
    and new universe begins.............
     
  8. Mar 21, 2015 #7

    phinds

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    This does not make sense. Can you restate what it is that you are saying?
     
  9. Mar 21, 2015 #8

    DaveC426913

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    How would the expansion of space time lead to the growth of a black hole? Cosmological expansion does not make things larger.

    If anything, expansion would actually result in the black hole being starved for fuel.
     
  10. Mar 22, 2015 #9
    A black hole with a mass of ≈ 8.7×1052 kg would have Schwarzschild radius rS ≈ 13.7 billion lightyears... According to NASA/WMAP, that is a somewhat reasonable "Mass of the Universe" estimate... Is there a message hidden here, somehow?

    The formula is simple: rS (in meter) = 2GM/c2, where G is Newton's gravitation constant, M is the mass in kg, and c the speed of light in m s-1.

    According to Hawking, it would be rather cold... 2.3×10-29 K...
     
    Last edited: Mar 22, 2015
  11. Mar 22, 2015 #10

    phinds

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    No, it is not. It is an estimate of the OBSERVABLE universe. The whole universe is unknown in scope but likely at least orders of magnitude larger than the observable universe and possibly infinite.
     
  12. Mar 24, 2015 #11

    Chronos

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    The mass of the observable universe is not something easily measured directly. We can, however, measure its curvature and use that to determine mass equivalence. CMB measurements tell us the universe is dead flat to the limit of our measurement ability. If you plug the numerical value for 'dead flat' into the formulas used to derive the mass equivalence of the universe, you get about 10E53 kg. Plug that number into the Schwarzschild formula you get... the hubble radius of the observable universe! Sounds like an amazing coincidence - until you realize the Hubble radius is part of the calculation for mass equivalence of the observable universe in flat space. In truth, the observable universe more closely resembles a white hole, than a black hole. It should be noted that any mass that might lay beyond the hubble radius of the observable universe is of no observational consequence because it is not in causal contact.
     
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