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B Combine a horizon line with expansion

  1. Sep 23, 2016 #1
    In this thread let's forget math, we don't have math to describe these energies anyway. Observation tells us that at extremely high energy densities there is some expansive force that vastly overwhelms everything else. Expansion has become the only viable explanation to what we observe.

    So I started thinking about a black holes collapse. Eventually, it must reach that energy density. At that point there is already a well defined event horizon, but now a small part of the space inside starts expanding faster than the speed of causality.

    What would happen next? I imagine everything outside of the event horizon is still causally disconnected from what's going on inside. Inside though, I imagine a completely new universe with a total energy of the mass of the black hole.
  2. jcsd
  3. Sep 25, 2016 #2


    Staff: Mentor

    How does observation tell us that? What observations are you referring to?

    This is not what the standard models of black holes say. Where are you getting this from?

    There are speculative models along these lines, but they're just that--speculative. Which means they're not suitable for discussion here.
  4. Oct 4, 2016 #3
    The smoothness of the microwave background. Isn't inflation the only theory left that explains that?

    Okay, forget the actual universe and go purely mathematical. What happens when rapidly collapsing spacetime suddenly starts expanding? Does all of that new space fit inside the collapsed part like a bubble?
  5. Oct 4, 2016 #4


    Staff: Mentor

    Currently it appears to be the only viable theory, but that just means that in one particular case of high energy densities, there happened to be accelerating expansion. The claim you made was much, much stronger: that at high energy densities there must be accelerating expansion, in all cases. As far as GR is concerned theoretically, this much stronger claim is certainly false: there are many consistent GR models in which there are high energy densities but not accelerating expansion.

    What specific model are you referring to? Can you give a reference?
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