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Black hole similar to pre universe

  1. Feb 6, 2014 #1
    Hey all,

    I was wondering if the singularity at the bottom of a black hole is similar to what the universe would be like before the big bang, i.e. heaps of mass/energy concentrated into a tiny point.

    To me I always think of black holes as sinkholes dotted throughout the universe which are like super highways for entropy to be destroyed and return to a low-entropy state.

    If the whole universe is like a closed thermodynamic system, then black holes are like concentrated points in which higher entropy pockets quickly become lower entropy.

    Am I interpreting this properly and is it correct?

    Are black holes the universes way of trying to converge back to its low-entropy t=0 state?

    If a black hole sucks in a bunch of matter, then explodes is that not similar to the big bang?
  2. jcsd
  3. Feb 6, 2014 #2


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    This topic is discussed at least once a month on these forums: I'd recommend you search through some of the threads. Short answer: no, the big bang is not like a black hole. The big bang did not occur from a "tiny point" -- a singularity is not a physical point: both the big bang and black hole singularities are spacelike hypersurfaces (really moments in time!)
  4. Feb 6, 2014 #3


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    Actually, it is believed a black hole has very high entropy. The entropy that enters a black hole is not destroyed [which is believed impossible due to the laws of thermodynamics], merely trapped. Physicists generally believe it is slowly returned to the universe via Hawking radiation. It is believed a black hole cannot explode until most of its mass has been carried off by Hawking radiation. This is difficult to test because it takes an unimaginable amount of time for an ordinary black hole to lose mass. Except for the theoretical primordial black holes, whose existence is unproven and in doubt, an ordinary black hole is much more massive than the sun. The background temperature of the universe is still much higher than its Hawking radiation temperature, so all black holes are actually absorbing more energy than they emit. Evaporation cannot even begin until the background temperature shrinks below the black hole temperature. This will require many billions of years. As noted, a black hole cannot explode until it has radiated away so much mass it can no longer hold itself together. The minimum mass necessary to form a black hole is the Planck mass, which is quite miniscule [much less than a gram]. It is uncertain at what mass a physical black hole would become at risk of detonation, but, it is fairly certain to happen when it fell to a Planck mass. The 'bang' produced by a decomposing Planck mass black hole would be spectacularly feeble.
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