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Would a supermassive black hole explode?

  1. May 4, 2015 #1
    I was thinking today about black holes. I was imagining how they formed a singularity, not mathematically, but physically and I got stuck at the Planck density. It's not a singularity yet and even with the entire weight of the rest of the object on top of it, you shouldn't be able to pack more energy. So I imagined it pushing back, which would then cause a shockwave through the material still falling in on it, creating a moving wave at the Planck density. Which would overwhelm even gravity and blow off a large chunk of the black hole. Anything it ejected would have already passed the event horizon so I imagine a black hole as a constantly exploding and collapsing cycle. I then tried to figure out what would happen around the black hole. The amount of gravity required to get energy density to the Planck scale is huge, so space-time would be dilated to an extreme, and as the black hole collapses, the dilation would get more and more extreme, then as it exploded, it would lessen slightly. So I would bet on some sort of gravity wave. I thought about if anything like that had been detected emanating from a black hole and hit a snag. The extreme time dilation would mean that even if the milky way's black hole explodes in a microsecond of it's own time, it could take billions of years from our perspective. Any thoughts / glaring errors?
  2. jcsd
  3. May 4, 2015 #2


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    I think this is an unsupportable personal theory. Physically, we have no idea what the "singularity" is but it is expected that if/when we get a solid theory of quantum gravity there will be a better understanding of what it might be.
  4. May 4, 2015 #3


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    What you describe initially, the negative pressure caused by reaching the Planck density, is in line with QG (at least LQG) proposals. The shock wave may sound plausible (it happens when collapsing matter hits a solid iron core in the usual supernova description), but it doesn't seem to happen in such models - my guess is because the Planck density core is not a pre-existing solid region but is forming instead gradually as the star collapses - at least in the models I've seen.

    The last part about oscillations doesn't make sense to be. If matter is blown out, it escapes, that's all, I would expect. But anyway, unless you have a model that does produce a shockwave that point is moot.

    However a (speculative) rebound scenario (without shock wave) does exist, it is described as a "Planck star" model where the star collapses to a plank density core which then explodes as a white hole.( http://arxiv.org/abs/1401.6562)
    Last edited: May 4, 2015
  5. May 4, 2015 #4
    I came to an oscillation conclusion because I figure anything that the explosion would shoot out would be blasted from far below the event horizon at less than the speed of light. The explosion wouldn't negate the effect of gravity and anything blasted out would get sucked right back in because it didn't reach the escape velocity of >c.
  6. May 4, 2015 #5


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    Hmm yes I see. In that scenario it would have no effect whatsoever on space outside the horizon and would end in the core anyway. But in any case the shock wave scenario can't be discussed here unless there's a published model of it to talk about.
  7. May 4, 2015 #6


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    Professional scientists are also stuck, so don't be discouraged about it. Unfortunately the rest of your post is speculation and I'm afraid I'm going to have to lock this thread. If you have a reputable source that you'd like to discuss the specifics of, please feel free to make a new thread.
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