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Conservation of mass and black holes

  1. Aug 7, 2014 #1
    With this post I am hoping someone would be kind enough to lead me in the right direction.
    I am a layman who knows little about the actual math behind physics, nonetheless I have developed an interest in it and wish to expand my knowledge base.
    First question I have is if someone could shed some light for me on the bet between John Preskill and steven hawking and kip thorne. My understanding to the best of my ability is that Hawking conceded because his Hawking radiation wouldn't hold any information?
    Second question is Could I get some internet site recommendations on the best known and excepted theories on where the information goes since it has to stay in our universe and black holes can not be perfect absorbers.
  2. jcsd
  3. Aug 7, 2014 #2


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    It is still unknown, but Hawking decided to concede because the radiation could have information (Hawking and Thorne were betting it could not).

    That depends on the background knowledge you have. Note that all descriptions for laymen are wrong or at least really simplified in some way.

    There is no conservation of mass, by the way.
  4. Aug 7, 2014 #3
    I'm glad to hear he conceded to the opposite of what I thought but your answer leads me to other questions, so maybe you could straiten me out some more.

    Do you know if Hawking still believes black holes will eventually shrink and explode?
    Again to the best of my understanding, hawking theorized radiation would slow the black hole's spin. When slowed and continuing to emit radiation its mass goes down so does the entropy and area making its temperature and surface gravity go up. It makes the hole keep shrinking and becoming hotter. Would this theory still stand?

    second question With my understanding of what Hawking radiation is I don't understand why he would make a bet like that, maybe I'm missing something (probably the math). Is the radiation virtual particles and anti particle pairs in which one will escape and the other will be sucked into the event horizon before annihilating each other, the escapee being the radiation?

    You have me intrigued, is the same true for law of conservation of energy or the The first law of thermodynamics, please elaborate.
    Last edited: Aug 7, 2014
  5. Aug 8, 2014 #4


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    Hawking radiation doesn't really have anything to do with spinning or non-spinning black holes. He applied quantum field theory in curved space time to the Schwarzschild solution and found that an observer some distance away from the black hole sees the black hole emitting thermal radiation. This theory still "stands" (of course, we have not actually experimentally verified it, but as a theoretical consequence, it is not really strongly disputed within the community) as it does not have much to do with the bet itself. The bet itself was not on whether the Hawking radiation occurs or not, but on whether this radiation is "new" radiation which is purely thermal and contains no information from the matter that went into the black hole - the information inside the black hole is then slowly lost as it evaporates, or if its still a repackaging of "old" information from the matter that went into the black hole and therefore the information is not truly lost, but more like jumbled up like burning a book. Hawking and Thorne said that information is lost, while Preskill said information is not lost.

    The information paradox is still an ongoing issue. There has been no consensus on this issue in the scientific community, and new ideas are still being formulated. I believe Hawking conceded the bet after theorizing that the singularity inside the black hole leads to baby universes where the information is deposited, and therefore information is not truly lost. Or perhaps it was as mfb said, that Hawking conceded after finding some other way the information could leak out of the black hole and back into our universe somehow. Hawking conceded, but Thorne did not.

    I think the latest statement from Hawking is that a classical event horizon does not form in the first place, and that black holes are really "grey" holes (you may have seen the media reports of "Hawking says black holes don't exist!"). But I can't comment on this because Hawking's published paper was like a 1 page summary of his ideas in words that are too difficult for me lol.
  6. Aug 8, 2014 #5


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    There is, however, conservation of energy - at least locally. Since mass is merely an extremely dense form of energy, the conservation of energy rule still applies.
  7. Aug 8, 2014 #6


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    This is expected by (nearly) all physicists, including Hawking - just the explosion bit at the end is unclear.

    This is a typical description of the process.

    Why do you think "there is no conservation of mass" would imply "there is no conservation of Y" for some Y?
    There is local conservation of energy, and no violation of the first law of thermodynamics has been found.

    To see a non-conservation of mass, consider annihilation processes or pair production from photons.
  8. Aug 8, 2014 #7
    I found where mass has not been considered absolutely constant, or unchangeable since 1903. My previous idea was that conservation of mass and energy was one in the same but I see why it's not, thanks mfb and chronos.

    The paper Matterwave talked about interests me if anyone knows more about it I'd love to know. Is it ‘Information preservation and weather forecasting for black holes’ from January this year?

    So with his new theory that this radiation contains information, would not be corresponding with the current definition of an event horizon (where info is lost), so he changes the name to an apparent horizon (with chaotic gravitation collapse)?

    In one aspect of the paper mentioned above is he saying that firewalls would be more likely, with the idea of this apparent horizon? because the idea of an event horizon breaks the CPT invariance of quantum gravity(-new concept to me, a link between conservation theories and symmetry?) but an apparent horizon would be compatible with CPT.

    In this more chaotic, turbulent idea of a horizon would the previous idea of tidal gravity from a black hole be the same?

    Would the ideas of the spaghettification of an object falling in the horizon, from an outside observer be the same?
    Last edited: Aug 9, 2014
  9. Aug 9, 2014 #8


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    All those new ideas are just about the event horizon itself and/or the interior, if such a thing exists.
    Outside (even just a picometer away) everything stays the same. Tidal gravity, spaghettification and so on outside do not change.
  10. Aug 9, 2014 #9
    Last edited: Aug 9, 2014
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