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Black hole thought.

  1. Apr 7, 2005 #1
    Could black holes get so enormously dense and big that they cannot swallow anything else and eventually explode? Like a big bang. What if black holes are the eventual evolution of space/time/existence as we know it. All matter is swallowed back by all the black holes in the universe, then black holes swallow other black holes then eventually it cannot sustain itself and starts the expansion again... giving off another big bang so to speak. :eek:
    Last edited: Apr 7, 2005
  2. jcsd
  3. Apr 8, 2005 #2


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    There is nothing in the theory which indicates that black holes have a size maximum. As they swallow more stuff, they just get bigger. Although we don't know what is going on inside, nevertheless, the average density decreases as they get bigger. The radius is proportional to the mass.
  4. Apr 8, 2005 #3
    Imagine a black hole whose size is the same as the cosmological event horizon. One horizon is pulling things in, the other is pulling them out. What would happen? If the universe were to exponentially accelerate, then perhaps it is really possible for the cosmological event horizon to shrink to the size of a galaxy consisting of nothing but a large black hole.
  5. Apr 9, 2005 #4


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    Could you expand on this? It looks like you have a black hole consisting of the entire universe. What do you mean by "cosmological event horizon"?
  6. Apr 10, 2005 #5
    You know that if space is expanding, then the further away things are the faster it is receeding away from us. At some point things are receeding so fast that light from that region will not reach us. This is the cosmological event horizon. Also, as the universe accelerates in expansion the distance to the cosmological event horizon gets closer. Some say that this acceleration will cause all the other galaxies to eventually receed away from us so that the cosmological event horizon will be little bigger than our present galaxy.

    In the mean time, gravity still operates, causing matter to contract. This may cause galaxies to collide and black holes to form. This may eventually cause there to be created black holes about the size of a galaxy.

    So it seems that there is coming a possibility of an observable universe consisting only of a black hole. I am questioning along with you what exactly that would imply and if it would even be physically possible.

    A cosmological event horizon so close to the surface of a black hole. The close cosmological event horizon means space is receeding away from us very fast indeed. But a black hole event horizon means space is contracting as much as it can. Are these two situation contradictory? Or is it completely consistent? Afterall, a black hole event horizon is where reference frames are accelerating as you get closer. I don't know, you tell me.
  7. Apr 10, 2005 #6
    The two situations are contradictory. Once something collapses gravitationally it is no longer part of the hubble flow. Hence in a Universe dense enough such that gravitational effects cause the whole universe to collapse gravitationally, there will be no expansion hence no cosmological event horizon. There would be no expansion of space in this 'black hole universe'.

    I fact this is analagous to a closed universe where the density parameter is greater than 1. the gravitational forces eventually cause the 'big crunch'.
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