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Black Hole 100% proven already?

  1. Dec 14, 2011 #1
    Are Black Hole 100% proven already or are they just theoretical construct? If the latter, how come the news item in the following speaks as if Black Holes are 100% certainty?

    http://www.bbc.co.uk/news/science-environment-16178112
     
  2. jcsd
  3. Dec 14, 2011 #2
    Nothing is 100%, but I'd put existence of black holes as 99%.
     
  4. Dec 14, 2011 #3

    e.bar.goum

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    Well, we can observe really really massive things (in the center of the Milky way, for instance) that seem to behave as we would expect black holes to behave, as far as we can see. Whether or not one is willing to call them a black hole is a matter of taste. Most people do though.
     
  5. Dec 14, 2011 #4
    It's one of those. It looks like a duck. It quacks like a duck. No one has come up with a better explanation for it than being a duck. How sure do you have to be that it is a duck before you call it a duck?
     
  6. Dec 14, 2011 #5

    e.bar.goum

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    Indeed! Black holes are an extreme example of this (rather common) phenomenon - we cannot ever actually observe a singularity directly, so, that which we call a black hole is one that looks and quacks like we expect one to.
     
  7. Dec 14, 2011 #6

    phinds

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    Yes, but we MAY some day (not any time soon, though) be able to observe a black hole as it appears from the outside; that is NOT an impossibility. Observations will still be somewhat indirect but they will be direct enough to conclude that it IS what we call a black hole.
     
  8. Dec 15, 2011 #7

    e.bar.goum

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    Well yes, as it appears from the outside being the key phrase - you still can't see behind the event horizon, and say "yep, that's a singularity", as I interpreted the OP. Space-time outside the black hole could still be examined though, and that would be good enough.
     
  9. Dec 15, 2011 #8

    Chronos

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    The only thing reasonably certain about a black hole is it has an event horizon. That does not necessarily require a singularity.
     
  10. Dec 15, 2011 #9

    phinds

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    Just the point I was about to make in response. Thanks.

    There have even been hypotheses that there IS no singularity in a BH but rather some sort of unbelieveably dense plasma. I don't "get" that, but it's what I've read.
     
  11. Dec 15, 2011 #10
    In the Big Bang what is the minimum possible length of the original core (1 Mile)? How is it calculated? Whatever it is, the Black Hole core (singularity or whatever) can't be smaller than the BB original core.

    Also does it mean the BH core of masses equal to billions of suns is the same size as a BH with few times the solar mass?
     
    Last edited: Dec 15, 2011
  12. Dec 15, 2011 #11

    e.bar.goum

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    For sure, and kind of my point. I think we're actually in violent agreement here.
     
  13. Dec 15, 2011 #12
    I do and those papers are non-sense papers written by people that don't understand general relativity. This issue was settled in the 1970's, but you have the occasion paper from people without clue.
     
  14. Dec 15, 2011 #13

    phinds

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    Thanks for that. I was not aware.
     
  15. Dec 15, 2011 #14

    phinds

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    There is no such thing. There was no center to the BB.
     
  16. Dec 15, 2011 #15

    Pengwuino

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    In what sense would it not have a singularity according to these people? I mean, I'm under the impression the true nature of the singularity when you reach the quantum scale still need a theory of QG to really be talked about. Or are they saying that there's no singularity even at the macroscopic scale of GR?
     
  17. Dec 15, 2011 #16
    I mean, not the center.. but the original core.. do you actually believe the entire universe with billions and billions of galaxies was once the size of an atom.. if not.. what's the size in miles before Inflation.
     
  18. Dec 15, 2011 #17

    Chronos

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    I think the planck density is a plausible limit on density. But, there is nothing to assure us quantum mechanics was not an emergent property of the universe. So, it is certainly conceivable the big bang originated from a true singularity.
     
    Last edited: Dec 15, 2011
  19. Dec 15, 2011 #18

    Pengwuino

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    There would be nothing preventing a sufficiently massive object from continuing to collapse into a singularity. So, Sun, Galaxy, or entire Universe, there's no reason (yet) to believe there's a point where a gravitational collapse would stop at some very small radius. In terms of the Big Bang, there is no reason to believe (yet) that there was a finite radius that the universe had to start out of. I mean to say that there is no minimum radius that must exist no matter how massive something is, not that the Big Bang was the result of a collapse.

    (Edited for much clarity)
     
    Last edited: Dec 15, 2011
  20. Dec 15, 2011 #19

    Chronos

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    There is a flaw in that logic. What collapsed to form the BB singularity?
     
  21. Dec 15, 2011 #20

    Pengwuino

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    Ewww what horrible wording I chose.
     
  22. Dec 15, 2011 #21

    So a 100 billion sun mass black hole has the same singularity or core size as a black hole a few times the sun mass and what differs is the mass.. just like the same wire can emit different magnetic field (or mass in analogy) resulting in different event horizon sizes for both (a few kilometers to a few light years)?
     
  23. Dec 15, 2011 #22

    Chronos

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    The planck density is quite high, so the radius of universe mass black hole would be virtually indistinguishable from the radius of a solar mass black hole.
     
  24. Dec 15, 2011 #23
    Black hole event horizon is said to be the point of no return.. that the cliche goes.. "not even light can escape..." but for quantum entangled pair.. inside and outside the black hole. They are still correlated right?
     
  25. Dec 15, 2011 #24
    I know the Big Bang created or expanded space and time but when it is just 1 mile in length. There is an edge.. the edge of the 1 mile spacetime ball. But it is said the universe has no edge.. how do you explain that?

    Another thing. When we heard the phase how many angels can dance in a pin head. We laugh how ridiculous it sounds. But in actual life, many men on the street are not aware that the question "how many galaxies can fit in a pin head" has an answer and it is "All of the known galaxies". Anyway. How do you calculate again for this planck density? It's so fantastic that all the universe as pure energy can be contracted to a planck size region and can fit there. Is the calculation definite or just theoretical?
     
  26. Dec 15, 2011 #25

    D H

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    The universe is not and never was a black hole.

    The only thing that "Big Bang singularity" and "black hole singularity" have in common is that word "singularity." The natures of these singularities are quite different, and most physicists think that these singularities aren't quite real.

    Ask astrophysicists what is at the center of a black hole and they will answer that general relativity says that the center of a black hole is a gravitational singularity. They will also be quick to point out that most physicists also think that this indicates that there is some unknown flaw in general relativity. Do black holes have an event horizon? Yes. Is all mass/energy truly concentrated at a single point? Almost certainly not.

    Ask cosmologists about what happened at t=0 and they will answer that the standard cosmological model says that at the instant of the big bang universe was a singularity. They will be even quicker to point out that this supposed singularity was nothing like a black hole. Moreover, nobody believes that the universe truly was a singularity. Singularities in a physical theory are an indication that the theory isn't quite right. A better answer is that standard cosmological models currently can't answer questions about what happened in the first 10-30 seconds of the universe.
     
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