There IS no interior of a black hole

Discussion in 'Physics & Math' started by Mike_Fontenot, Nov 25, 2022.

  1. Mike_Fontenot Registered Senior Member

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    That seems like a very unenthusiastic statement in support of an interior of a black hole, to me. I don't think his views on this issue changed much between 1962 and 1975.

    But I don't know if and/or how his view changed after that.
     
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  3. foghorn Valued Senior Member

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    Mike
    Here's Dirac calling the region r< 2m also a black hole. ( That's the region inside the event horizon): page 36
    My green underlined.

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    And here's you saying the surface is the entire black hole because there is nothing inside and so the event horizon can't be crossed.
    Have you a Dirac quote saying material can't cross the horizon?
    Have you a Dirac quote saying the entire black hole is just the event horizion?
     
    Last edited: Dec 31, 2022
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  5. Mike_Fontenot Registered Senior Member

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    Schwarzschild gave equations for two regions: r > 1 , and r < 1. I don't believe the term "black hole" existed then, but according to Dirac, the black hole doesn't include the region r < 1.

    Dirac said:

    "so I feel that the space inside the Schwarzchild radius must belong to a different universe and should not be taken into account in any physical theory." (The "Schwarzchild radius" is the event horizon, where r = 1.)

    Therefore Dirac said that there is NOTHING in our universe inside the event horizon of a black hole. And in his statement that you quoted, he was really just saying that the only thing we can observe is the region r > 1. We can't see the event horizon (at r = 1), and we obviously can't see anything beyond the event horizon (r < 1), since anything in that range of r is NOT in our universe.
     
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  7. arfa brane call me arf Valued Senior Member

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    Understanding what a black hole "really" is, I don't think is going to be facilitated by clinging religiously to what one scientist said.

    Note that Penrose diagrams earned the man a Nobel prize. Dirac didn't get a Nobel for his work on black hole theory.
     
  8. Mike_Fontenot Registered Senior Member

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    I don't disagree with anything you said. But there are still disagreements about what Dirac said.
     
  9. foghorn Valued Senior Member

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    Dirac uses the term black hole to describe the region r < 2m, see page 36 below.
    Mass in units of length gives the event horizon as r = 2m for all Schwarzchild black holes, that's why Dirac uses the term 2m for the event horizon. See page 36 below.

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    I'm getting off your merry-go- round.
     
    Last edited: Jan 1, 2023
  10. James R Just this guy, you know? Staff Member

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    As several of us have pointed out, Dirac did not claim in 1962 (or any other year, as far as I'm aware) that there is no interior of a black hole.

    The quote you have been referring to merely expresses Dirac's view (at that time) that nothing inside the event horizon can affect the universe outside the event horizon; therefore, any events that occur inside the event horizon are irrelevant to the physics of the external universe. That's all Dirac is saying, there. He clearly did not share your view then, or later. You have been provided with references that explicitly refute your interpretation. Can you not see that?
    It's a derived result from general relativity. It doesn't matter what you think of it, unless you can find some error in the derivation or in the theory of relativity itself.
    He chose the coordinate r because it matches the common-sense notion of a radial coordinate in the "external" region (r>1) of the black hole. The value r=1 for the event horizon is simply achoice of scaling of the r spatial coordinate, which is a measure of distance. Literally, in this case, we measure the distance from the centre of the hole to the event horizon to be equal to 1 "event horizon distance", and measure all other r values in units of the "event horizon distance".

    In the quote from Dirac that was provided by foghorn, above, you will see that the event horizon is not at r=1, but at r=2m. In that case, the 'm' designates the mass of the black hole. Clearly, though, a radial distance cannot be equated with a mass, so what's going on here? The answer is again that the units are scaled; in this case some factors of \(c\), the speed of light, are implied, along with the universal gravitational constant, G. It is quite common in the relativity literature to choose distance and/or time units such that the speed of light has numerical value c=1; that is what has been done here, in effect. For instance, if we choose to measure distances in light years and time in years, then the speed of light is 1 light year per year, or c=1. Similarly, we can choose mass units such that G=1. Then, from General Relativity, we find that the event horizon distance for a black hole is r=2m. A different choice of mass units gives r=1, as previously discussed.
    The interior solution from GR is what it is. Again, if you want to refute that, you'll need to find a flaw in the derivation, or a flaw in GR itself.

    The interpretation of the solution follows from the maths, essentially.
    Dirac says the opposite in the quote provided by foghorn, above. He calls the r<1 region the black hole. Everything at r>1 is not the black hole.
    He meant that nothing inside the event horizon can affect our universe. The converse does not apply, however. There's no reason why our outside universe cannot affect the inside of a black hole. Moreover, observationally, it does just that.
    From the outside, yes.
    He didn't say that. His point is only that nothing at r<=1 can send any kind of information out to r>1. But, again, the converse is not true. Clearly, information can be sent into a black hole from outside.
     
  11. arfa brane call me arf Valued Senior Member

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    Black holes are supposed to be the simplest (gravitational) objects in the universe. Well, at least classically they are.
    But nobody should get the idea that black holes are well-understood, or that there are some details left to be ironed out. That is not the case.

    There are still a lot of unanswered questions: Einstein didn't believe Schwarzschild's solution could describe anything real; there are still, today, solutions to the field equations that nobody understands or can explain (c.f. Hawking-Bekenstein entropy). It is what it is.

    It's kind of strange too, that physicists can formulate things whose nature is unknown, in a consistent way. Right?
     
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  12. JJM Registered Senior Member

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    • Please do not post pseudoscience or nonsense in our Science sections.
    bh are impact momentum spheroids, as is most events in Nature. Therefore a bh has resonating pulsating waves and fields of dm. That is the composition of a bh. Remember compressed compression pressure density is gravity density, ergo most all objects are evolved dm.
     
  13. origin Heading towards oblivion Valued Senior Member

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    This is a thread discussing science, please don't interject your mind numbing ramblings.
     
  14. Beaconator Valued Senior Member

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    I would like to have more information on this because my idea might just make a black hole. Either incredibly reflective or a black hole. Wouldn’t want to make one of those very large… it could be like a nuclear bomb’s radius with a black hole at the center. So I suggest something at the atomic scale.
     
  15. James R Just this guy, you know? Staff Member

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    What idea?

    (Might be best not to post your idea in one of our Science sections, unless it is scientific.)
     
  16. Beaconator Valued Senior Member

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    How is the power of all elements not science?

    should I add acids to acids and bases to bases? Or just throw them both on the wall like Jackson Pollick?

    the result is the same
     
  17. Beaconator Valued Senior Member

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    They exist and only consciousness can place them together.
     
  18. James R Just this guy, you know? Staff Member

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    Please keep your nonsense out of the Science sections, Beaconator.
     

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