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I Event horizon and sudden acceleration

  1. Jul 22, 2016 #1
    Scenario 1: Alice drops into the event horizon at free fall and notices nothing as she crosses it. Bob looks on from the outside and sees her flattened against the event horizon.

    Scenario 2: Alice drops into the event horizon from the outside and notices nothing. But as she nears it, she suddenly whips out an immensely powerful propulsion device, points it towards the singularity and activates it.

    What does Alice see in scenario 2?
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  3. Jul 22, 2016 #2


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    Looking away from the horizon? An increasing blue shift of the free falling light, as she accelerates.
  4. Jul 22, 2016 #3
    As I understand it, to Bob, the event horizon appears extremely hot. To Alice in free fall, nothing seemed out of the ordinary as she neared it. When she experiences acceleration, does the area close to the event horizon suddenly become extremely hot? (Possibly as a consequence of the blue-shifted light?)

    Or did I misunderstand the theory?

    (In addition: Can Alice see the singularity when she is in free fall? As a point of blackness, maybe? When she accelerates, does everything inside the event horizon visually disappear and other things falling into it appear as visibly flattened against its surface?)
    Last edited: Jul 22, 2016
  5. Jul 22, 2016 #4


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    When you say that the area around the horizon appears extremely hot, are you thinking about the accretion disk, the hot infalling matter that surrounds some black holes? That's there for both Bob and Alice (of course - how could it be otherwise?) so if we do this experiment with with a black hole that has an accretion disk, Alice gets cooked whether she's in free fall or accelerating.

    Or are you thinking of some the interesting but unproven hypothesis that every black hole is surrounded by a "firewall" of high energy radiation at the event horizon? That's a hypothesis, but if it is correct Alice cooks, again whether she accelerates or not. Google for "black hole firewall" for more.
  6. Jul 22, 2016 #5
    I took everything Leonard Susskind said in this lecture in the literal sense:

    Could you recommend a book or some other source that goes into it in more detail?
  7. Jul 22, 2016 #6
    Dear glOWyrm,

    It seems to me Dr. Craig Hogan's experiments in Fermilab ruled out the cherished theory of Leonard Susskind exposed in his recent book "The Universe From Nothing". Time and space are not granular.

  8. Jul 22, 2016 #7
    Has that book been published yet?
  9. Jul 22, 2016 #8
  10. Jul 22, 2016 #9
    I was hoping for a popularization with technical details, but I suppose I could try and go through the paper on that website. How has the scientific community responded to this research?
  11. Jul 22, 2016 #10

    Hovering near a black hole is a quite ordinary situation:

    Bob sees black hole emitting some amount of thermal radiation. Bob sees Alice, who is hovering near the black hole hole, emitting extremely small amount of thermal radiation. Therefore Bob considers the black hole to be hotter than Alice.

    Black holes are warmer than things hovering near black holes, that's why things hovering near black holes are heated by black holes.

    Now this "firewall" thing ... A black hole has a temperature, which is the same temperature as the temperature of the Hawking radiation that the black hole emits. A hovering thermometer can not find any any other "firewall" than the Hawking radiation, because the black hole's temperature is defined by the Hawking radiation. I mean, if hovering things are heated by something else besides Hawking radiation, then black holes are hotter than we have thought.
    Last edited: Jul 22, 2016
  12. Jul 22, 2016 #11


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    Um... Your comment "Time and space are not granular." is too strong a claim. Let's look at what was actually written in the news release (emphasis by me)
  13. Jul 22, 2016 #12


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    Last edited by a moderator: May 8, 2017
  14. Jul 23, 2016 #13


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    Well, there are many different books with the same title. For instance "Quantum Field Theory".
  15. Jul 23, 2016 #14


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    Hm. I didn't realize that and Google only gives my one book with that title, as does Amazon. Lots with somewhat similar titles but none exact.

    EDIT poor search. Found several more where that is essentially the main title (not counting subtitles like "for the gifted amateur")
  16. Jul 24, 2016 #15


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    Here are some books which have the exact title "Quantum Field Theory" and do not have any subtitle:
    L. S. Brown
    C. Itzykson, J-B. Zuber
    F. Mandl, G. Shaw
    L. H. Ryder
    U. Umezawa
    M. Srednicki

    Also, there are several books with exact title "Introduction to Quantum Field theory" or "An Introduction to Quantum Field Theory". The situation with "Quantum Mechanics" is similar.
    Last edited: Jul 25, 2016
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