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B Black hole from a photon

  1. Feb 27, 2017 #1
    Is it possible for a photon to be so energetic that it forms a black hole?

    If so, how fast would that black hole be moving?
  2. jcsd
  3. Feb 27, 2017 #2


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    It is not, as the energy of a photon is frame-dependent. An observer moving away from the emitter would measure the photon as having a lower amount of energy than an observer moving towards the emitter. In addition, a photon has no reference frame that we can assign to it.
  4. Feb 27, 2017 #3
    We need a mass to form a blackhole
  5. Feb 27, 2017 #4


    Staff: Mentor

    Wow, I love PF because I learn every day from people like @Drakkith

    Do I understand correctly that objects (like photons) with frame-dependent energy can not form a frame-invariant object (like a BH) seen by observers in all frames? None of my teachers ever mentioned that implication of frame-dependent versus frame-independent. It is so simple and profound.
  6. Feb 27, 2017 #5


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    That is my understanding, but I'm not formally educated in relativity. It's just something I also picked up here at PF. :biggrin:

    It does make sense given that a cosmic ray proton travelling near the speed of light may see a massive star as having an staggeringly huge amount of kinetic energy. If the object's invariant mass was dependent on its kinetic energy, this star should collapse into a black hole. But it doesn't.
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