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Black hole evaporation

  1. Feb 19, 2010 #1
    black holes evaporate, i know that it sounds like it defies all rational elucidation but i think that black holes evaporate. see black holes emmit black body radiation they also emmit hawking radiation and hawking radiation as far as im informed shrinks black holes it causes them to lose mass and even matter.
     
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  3. Feb 19, 2010 #2

    nicksauce

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    Yes. This is highly agreed upon. (Although to the black body radiation black holes emit *is* Hawking radiation)
     
  4. Feb 25, 2010 #3
  5. Mar 1, 2010 #4
    ok thanks
     
  6. Apr 2, 2010 #5
    question, where does hawking radiation come from?
     
  7. Apr 2, 2010 #6
    and i have another question,what makes the universe expand? is it anti gravity or no one knows for sure
     
  8. Apr 2, 2010 #7
    one more question. if god exists what is he made of,and how can he survive the big crunch?
     
  9. Apr 2, 2010 #8

    nicksauce

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    This would probably be better asked in a philosophy or theology forum, rather than an Astrophysics forum.
     
  10. Apr 2, 2010 #9

    bapowell

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    From Stephen Hawking, of course :tongue:
     
  11. Jun 3, 2010 #10
    there are different views about the precise origin or Hawking radiation, but I think there is general agreement that quantum fluctuations are the ultimate source.

    Extremal black holes, at absolute zero, apparently do not radiate.....these are as far as I understand theoretical constructs...in fact I don't believe we have absolute observational evidence for any black holes yet....
     
  12. Jun 3, 2010 #11
    Wouldn't black holes BE unobservable by definition? The fact that we have things that act as theories on black holes predict, including unobservability, makes it, at least to me, seem rather convincing.
     
  13. Jun 3, 2010 #12

    bapowell

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    Black holes could be detected by observing their gravitational effect on their surroundings. Gravitational lensing, in which the black hole's gravity distorts the light from sources behind it, is one way. Also, by measuring the energy of the radiation from accretion discs, one can infer the existence (and mass) of the black hole. This second method is more indirect than the former, however, just because we can't use light to 'see' a black hole, this does not mean that they are undetectable in principle.
     
  14. Jun 3, 2010 #13
    I know, that's why I said unobservable rather than undetectable. But thanks for the elaboration.
     
  15. Jun 3, 2010 #14

    bapowell

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    I see little difference between those words. But this is no place for a semantic argument. Since this is a common question asked by forum goers, I think it's important to make the point that even though black holes are not visible, they are still observable.
     
  16. Jun 3, 2010 #15

    Chronos

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    Black holes are usually detected by radiation emitted by their accretion disc. Others are detected by their gravitational influence in a binary [or more] system. Gravitational lensing another possibility although I'm unaware of any direct detections by this method [too many plausible alternatives]. None are detected by virtue of their hawking radiation, it is much cooler than the CMB.
     
  17. Jun 4, 2010 #16
    Black Hole evaporation. Hawkins radiation. and dark matter. I think are the remains of proton distruction. It would explain why the universe is expanding as the charge would be positive and would repel all mater comming close to it. It would also account for the mismatch of strong and weak forces. Has anybody looked at this as a solution. Only areas where negative charges are abundant (electrons) would be able to accumulate and form stars and element solids.
     
  18. Jun 4, 2010 #17
    No scientist has ever admitted to actually seeing a black hole; though, there are good indicators where one might be though.

    By their very nature black holes do not directly emit any signals other than the hypothetical Hawking radiation. Since the Hawking radiation for an astrophysical black hole is predicted to be very weak, this makes it impossible to directly detect astrophysical black holes from the Earth. A possible exception to the Hawking radiation being weak is the last stage of the evaporation of light (primordial) black holes. Searches for such flashes in the past has proven unsuccessful and provides stringent limits on the possibility of existence of light primordial black holes.[64] NASA's Fermi Gamma-ray Space Telescope launched in 2008 will continue the search for these flashes.[65]

    Astrophysicists searching for black holes thus have to rely on indirect observations. A black hole's existence can sometimes be inferred by observing its gravitational interactions with its surroundings.

    http://en.wikipedia.org/wiki/Black_hole#Observational_evidence
     
  19. Jun 4, 2010 #18

    George Jones

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    Last edited: Jun 4, 2010
  20. Jun 4, 2010 #19
  21. Sep 21, 2010 #20
    the unverse as i see it is expanding because of the throw which caused th big bang .... the gravity being a very weak force , caoul not stop this expasion , hence we keep on expanding ..... but friedman proposes 3 models in which , the first one says that gravity will dominate and there will again be a big crunch , the 2nd says that the 2 forces will balnce out and th 3rd says that the unverse will expand to infinity .........
    and taxman , i don't think the unverse is expanding because of charge ....
    and hawking radiation comes from a particle and an antiparticle formed just aboive the event horizon
     
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