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I Quantum bits information lost in black holes

  1. Jun 21, 2017 #1
    I have just started googling/youtubeing black holes. One point made repeatedly discussed is the loss of information in black holes. In particular quantum bits. What I have not yet found is very much explanation of what these potentially lost bits might be. So what I would like to know is the following:

    A photon gets sucked into a black hole.

    How many bits of information is in that photon?

    What are those bits - one bit for position, one for momentum, one for phase ...????

    What I would like is for someone to enumerate the specific bits of information that a photon inside a black hole would consist of - number and kind.

    I follow the argument that what happens in a black hole can't be conveyed in the usual way outside of the black hole though I understand there are theories where events in the black hole can be somehow seen outside of the black hole - radiation, holographic - communication. However putting those aside, what I am not quite following is what does lost mean? Is it equivalent to not being able to see what is going on inside a black hole or conversely the processes in the black hole can't get out so they can't be be seen outside of the black hole? It seems to me that with virtual photons being created and annihilated out of the vacuum outside of a black hole if you aren't there just in time you might not see the process so information would be lost in that situation too? Or not? If not why is this information not lost as well?

    The final point made in my various sources is that quantum mechanics has some kind of problem with lost information - it seems to exclude the possibility at its very core. I am not sure what that means. Does it mean that anything quantum has to be 'seen' by its very nature to in fact be quantum? If it's not seen then it can't be truly quantum? What quantum rule/core concept is violated/contradicted if quantum information is lost? Is it tied up with some kind of measurement issue - if you start out with some combo x - potential energy and kinetic energy - you can do a lot of things but you can't change the total energy? So in the world outside of the black hole you have some immense global number of quantum particles/quantum states of such particles - a lot of quantum bits - and no matter what happens in this 'outside the black hole universe' you should always end up with the same global number of bits though they may be distributed in endless variations. Thus if something goes into a black hole this number of bits is decreased and 'quantum mechanics' is broken. So one photon going into the black hole kills quantum mechanics because we can't 'see' it anymore, it can't communicate what it's doing - the states it's in, the bits of those states - it's the same as if it didn't exist?

    Any assistance in clearing this up is appreciated.
  2. jcsd
  3. Jun 21, 2017 #2
    I suppose that depends on what you mean by 'information'. There's definitely vector information that is related to it's direction of travel. There's a wavelength bit of information, a polarization state, etc. There are also some quantum entanglement possibilities to consider:


    Since Hawking Radiation allows for all energy inside the black hole to be eventually extracted/evaporated out of a black hole again, the "total energy" isn't ever lost, but the aforementioned information related to the energy state coming back out of the black hole via Hawking Radiation, might not be directly related to the energy state as it went into the event horizon.

    I think I will deffer your QM questions to someone else for the time being.
    Last edited: Jun 22, 2017
  4. Jun 22, 2017 #3
    Thanks. When I use the word 'information' I am just using the word I read so it's not what I mean by it, it's what's meant when people use the word in the context I described. I am asking for the meaning of information as in the common phrase in this area - 'information' is lost in the black hole'.
  5. Jun 24, 2017 #4


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    Susskind has it all laid out in his "Black Hole Wars" book and it's an interesting read, at least the half I've read so far.
  6. Jun 25, 2017 #5


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    You're better off asking for the meaning of the complete phrase. The Wikipedia article on "black hole information paradox" is actually pretty good (but as with all Wikipedia articles, don't trust it until you've read the "talk" section, and be aware that not all Wikipedia articles are reliable).
  7. Jun 26, 2017 #6


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    I just read that talk section. It was very disappointing with speaker after speaker talking past each other mainly because of different definitions in their heads about the meaning of "information" in this context.

    I hate semantics debates. The worst kind are what I call "pun" debates; those based on multiple meanings of the same word(s).

    Scientists, and especially PF mentors will be forever tortured by a few notorious unfortunate choices of words. They are unfortunate because the words carry "baggage" in the form of common language meanings and associations. IMO, the three worst ones are:
    1. "big bang" in cosmology, which invites visions of an explosion starting from a point in space.
    2. "observable" in QM, which invites interpretations that intelligent conscious observers are required.
    3. "information" in the concept "Conservation of Information", which most lay people (supported by dictionaries) equate with knowledge. Adding entropy to the discussion just further muddles the water.
    I have a draft Insights article on exactly this topic, but I hesitate to publish it because I'm only an amateur at physics.
  8. Jun 26, 2017 #7


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    You left out "dark" as a part of the name of dark energy and dark matter.
  9. Jun 26, 2017 #8
    it's all moot until someone goes into one and reports back?
  10. Jun 26, 2017 #9


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    What are you talking about? Black holes? There IS no "reporting back"
  11. Jun 26, 2017 #10
    are you sure?
  12. Jun 26, 2017 #11


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  13. Jul 2, 2017 #12
    I think everybody is trying to provide to help but unfortunately I am not getting much out of this thread - lost me at unicorn for sure. There's far to much of that kind of diversion in social media chats. It seems to be built into the DNA of social media. I have no cure for it - I think like many I just move away when I encounter it. I think I will go back and ask in different ways with more questions more tightly targeted.
  14. Jul 25, 2017 #13


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    FRB and unicorns are not subject to this thread. That's why I deleted several posts. The subject can well be discussed by scientific arguments, especially on "I" level. Unfortunately, this goal seemed to be lost. Therefore I'll close this thread.

    @arlesterc You're absolutely right in your judgement of the answers given. I apologize for that. Maybe you could start a similar thread about the information loss on a new "A" level thread and eventually with a more precise definition of what is meant by "information". Also please report those hijack attempts as they occur, so we could react in time.
    Last edited: Jul 25, 2017
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