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Black and white

  1. Sep 18, 2011 #1
    Hello friends! Forgive me, I have another question for you physicists. We see those active galactic nucley which show enormous emission phenomena, so:

    How can we know that responsible are gigantic black holes and not white holes?

    I suppose we guess it, becouse we have some thoery on the formation of blackholes from a collapsing star while for white holes we have nothing similar, which makes the existence of white holes rather improbable to most people... but we cannot be really sure. Am I wrong?
     
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  3. Sep 19, 2011 #2

    Chalnoth

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    White holes are black holes with the time coordinate reversed. They don't exist for the exact same reason that we don't see eggs spontaneously jumping out of a frying pan and back into their shells.
     
  4. Sep 19, 2011 #3
    Is that all??
     
  5. Sep 19, 2011 #4

    DaveC426913

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    No. White holes don't exist because they comply with no known physics.

    Black holes have a mundane physical explanation - gravity. Gravity has no repulsive counterpart, thus no white holes.
     
  6. Sep 19, 2011 #5
    Perhaps, if I am not abusing of your patience, I must try to be more precise in my question. I already knew that most of the physicists don't believe in white holes, probably I don't too, but some scientists have a different opinion. There are relatively few papers on that subject in the literature, but there are some 20 rather recent papers on arxiv.org, which means there could be a sort of revival going on. So I would not like to discard the thing unless I can understand:

    1) do we have any observative proof that emission from active galactic nuclei (x-rays, jets, etc...)are really caused by matter falling into a supermassive black hole? Or is it mainly a matter of "what else could be?"

    2) in the unespected case white holes should exist, could they in theory be responsible (as well as black holes) for such phenomena? Or can we clearly exonerate them for some reason (but that the fact that their existence is unlikely)?

    Thank you
     
  7. Sep 19, 2011 #6

    DaveC426913

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    Well,

    1] "what else could it be" is a pretty good scientific argument.

    Our understanding of gravity and mass and the centre of galaxies leads to a model with black holes. There is no competing theory. There is no repulsive gravity, there is no model for a white hole.

    2] It's not simply "we see stuff spewing out, let's assume it's a BH". The stuff that's coming out is consistent with matter being highly compressed as it spirals inward to a strong gravitational source. We do know that's what matter does in that circumstance.
     
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