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B Can a photon be made energetic enough to escape a black hole

  1. Feb 1, 2017 #1
    why cant a photon escape a black hole? i think it is because the photon is red shifted away to nothing, if this is true, it would be possible to create a photon that would be energetic enough that a black hole would not have enough time to red shift it away to nothing, unless there is some theoretical limit on the energy a photon can have?
    Since a photon cannot be slowed, an force doing this will just red shift it, it should be theoretically possible.
    this brings me to another question, how can a photon be red shifted to nothing? as it is red shifted there will be less energy in the photon, so gravity would act on it less, it would be an exponential curve and would never reach 0. all this must b based on the assumption that we are launching this photon perfectly straight away from the black hole from within the event horizon so it cannot be bent, merely red shifted or decelerated.
    Last edited by a moderator: Feb 1, 2017
  2. jcsd
  3. Feb 1, 2017 #2


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    It is not true. Light cannot escape the black hole because the future lightcones for all events inside the event horizon never exit the event horizon. In turn, this is due to the spacetime curvature.
  4. Feb 1, 2017 #3
    At the event horizon of a black hole, spacetime is warped in such a way that there is no out. Think about an object inside of a black hole, now point in any direction. What's in that direction if you went in a straight line? The singularity. Okay, now pick another direction. It still points to the singularity. Now point in the complete opposite direction, that must be pointing out right? Nope, still straight line shot into the singularity. There is no direction that you can travel that leads out.

    Black holes can explode (theoretically) but it's not because of any extreme energy, it's simply from the uncertain nature of quantum mechanics than a photon may momentarily appear beyond the event horizon and escape.
  5. Feb 1, 2017 #4
    Thank you, you have sufficiently destroyed my wrong theory
  6. Feb 1, 2017 #5
    whatever direction you face will be towards the singularity, so if you threw something backwards and forwards at the same time would you actually be throwing them the same way?
    And what would happen if (theoretically of course, there is no way to actually do this) you reached the center of the singularity?
  7. Feb 1, 2017 #6


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    No. The singularity is not a point in space. It is an event in the future, the point is that the future of any object in the black hole ends in the singularity.
  8. Feb 1, 2017 #7
    so what you are seeing is actually the past? And if it only exists in the future and is not in the time of now what is the gravity that pulls you towards the schwarzschild (i hope i spelled this right) radius from?
    Is the gravity so strong i can pull through time?
    due to quantum theory, not all futures end in the black hole, right?
    Also you say that all objects that pass the event horizon are bound to end up in the singularity, because it is in their future, inescapable; but there are pictures of emissions coming out of the black hole at the poles, so whats happening there?
    Last edited: Feb 1, 2017
  9. Feb 1, 2017 #8


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    "Now" is not well defined in GR (or SR for that matter - even in the simplest incarnation it is observer dependent). What occurs in a Schwarzschild black hole is an effect of space-time curvature. To go into detail you need to go beyond B-level.
    These are not things coming out of the black hole. They are jets created by the accretion of external matter.
  10. Feb 3, 2017 #9


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    The gravity is from the matter and energy in the black hole. The details of this are beyond a 'B' level thread unfortunately.

    The phrase, "pull through time", makes no sense, so I can only answer with, "no".

    Quantum theory and General Relativity are not currently compatible, so there's no way to answer your question.
  11. Feb 12, 2017 #10
    Nothing except nothing escapes a BH.
    I like the river model as detailed by Professor Hamilton and his paper here....
    The EH of a BH is "falling in" at "c": Inside the EH that speed increases. [This does not contravene SR as it is only spacetime falling in...a massless quantity]
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