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B The mass of a black hole

  1. Jan 14, 2017 #1
    The question is probably naive, but please don't block this thread before I get an answer...

    As far as I know, mass doesn't exist by itself, it is rather an "attribute" of matter or, let's say it is attached to particles...no particle = no matter = no mass.

    Now, inside a black hole, everything, that is, particles, is crushed into nothingness.

    And yet it seems that once disintegrated, the mass of the concerned particles remains, since we are talking about the mass of a black hole...which depends on its appetite.

    Hence the question: to what exactly is the mass of a black hole "attached" to ? (since I suppose mass is not simply floating around in the void)
     
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  3. Jan 14, 2017 #2

    phinds

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    Good question and there's likely a Nobel Prize in your future if you can answer it. Presumably if/when we evolve a proven theory of quantum gravity we'll know what's REALLY going on in there whereas now the math in GR just breaks down to an un-physical answer which we call the "singularity".
     
  4. Jan 15, 2017 #3

    PeterDonis

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    This is not correct. "Mass" in GR, properly speaking, is a property of spacetime geometry. The attribute of matter that you are describing is called "stress-energy" in GR, not "mass".

    To the geometry of spacetime.
     
  5. Jan 15, 2017 #4
    But isn't spacetime also crushed into oblivion in a black hole?
     
  6. Jan 15, 2017 #5

    PeterDonis

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    No.
     
  7. Jan 15, 2017 #6
    Could you go a bit more into details?

    Inside a black hole, time stands still, which is a serious alteration of spacetime, if not a complete destruction.

    And what about the 3 spatial dimensions? I understood that they were "compressed" into one...singularity...

    I think it was in "The physics of Interstellar", Kip Thorne wrote that there is nothing inside a black hole, and that includes spacetime.

    How can mass be preserved in such conditions?
     
  8. Jan 15, 2017 #7

    Orodruin

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    No it doesn't, where are you getting this information? You are either misunderstanding the source or the source is wrong.
     
  9. Jan 15, 2017 #8
    OK...back to the first answer then: "mass is attached to the geometry of spacetime" and thus there is no need of a particle to have mass.

    Yet, what happens to the Higgs field and bosons in the black hole?

    Are these not requested for the existence of mass, or are they surviving inside the black hole, even though the boson is a particle that is not supposed to be safe there?
     
  10. Jan 15, 2017 #9

    Vanadium 50

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    Orodruin asked you to explain where you were getting this from,. not to switch to italics.
     
  11. Jan 15, 2017 #10
    Oh...no need to jump to my throat!
    It was a misunderstanding...and sorry for the italics, I don't even know how I switched to italics...
    And you guys at Physics Forums really need to cool down...we are just talking here, hence the word "forum", we are not in class, we can be wrong and then learn from our mistakes...we are not all experts, at least I am not...just a layman trying to educate himself...
     
  12. Jan 15, 2017 #11

    phinds

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    Might be a good idea for you to review the forum rules that you agreed to when you signed up. The PURPOSE of the "just talking here" is to discuss mainstream physics, which you do not seem to be doing. Wanting to educate yourself is great, but when someone asks you for the source of your "facts" it is good form to reply directly and immediately, not avoid the question. The reason for that is, as orodruin said, that we need to be able to figure out whether what you read is wrong or if you perhaps misunderstood what you read. This greatly increases our ability to give you a helpful answer.
     
  13. Jan 15, 2017 #12

    Vanadium 50

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    I note that you still haven't answered his question.
     
  14. Jan 15, 2017 #13
    Orodruin asked if it was a misunderstanding or a wrong source...I wrote, in answer to V50 that it was a misunderstanding...
     
  15. Jan 15, 2017 #14

    Orodruin

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    No I did not, this was the question:
    Unless you actually provide this information, there is no way for us to tell which is the case and how to correct your misunderstandings.
     
  16. Jan 15, 2017 #15

    PeterDonis

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    Please give an explicit reference and quote. Somebody is seriously misunderstanding something here, and I strongly doubt it is Kip Thorne. There is certainly spacetime inside a black hole, not to mention objects that have fallen in.

    And if you want us to help you with that, you need to give explicit references to the sources you have already consulted. Otherwise we can't tell where you are going wrong; we can only tell that you must be going wrong somewhere, since you are coming to incorrect conclusions.
     
  17. Jan 15, 2017 #16

    PeterDonis

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    Thread moved to the relativity forum as it is more appropriate there.
     
  18. Jan 20, 2017 #17

    julian

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    Asynptotic methods are needed to define mass rigorously.

    It is impossible to determine the mass of a gravitating body by simply adding up the contributions of particles, matter fields and the gravitational field. In general relativity, the concept of local gravitational energy is meanigless. This is because of the equivalence principle - in a freely falling frame gravity disapears, so what was thought as gravitational energy density in one frame is nothing in another frame.

    The only meaniful definition of mass is a global one, namely the quantity that determines the asymptotic gravitational field, as probed for example by orbiting particles.
     
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