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Hawking Radiation's Virtual Particles?

  1. Nov 10, 2011 #1
    Not sure if this is the right forum but hey ho..

    I have been reading about Hawking radiation in Black Holes, whereby virtual particles are created at the event horizon and of the particle and anti particle pair 1 can escape before it is annihilated.

    Why are the particles which make up the hawking radiation a virtual particle inside the Event Horizon but are real particles outside of the horizon?

  2. jcsd
  3. Nov 10, 2011 #2


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    Quoting from Birrell and Davies, p264: " ...the continuous, spontaneous creation of virtual particle-antiparticle pairs around the black hole can be used to explain the Hawking radiation. Virtual particle pairs created with wavelength λ separate temporarily to a distance ≈ λ. For λ ≈ M, the size of the hole, strong tidal forces operate to prevent reannihilation. One particle escapes to infinity with positive energy to contribute to the Hawking flux, while its corresponding antiparticle enters the black hole trapped by the deep gravitational potential well on a timelike path of negative energy relative to infinity. Thus the hole radiates quanta with wavelength ≈ M."
  4. Nov 10, 2011 #3


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    rollcast, make sure you note what Bill K said only implicitly "while its corresponding antiparticle enters the black hole" which mean the formation is OUTSIDE the event horizon.

    I was previously strongly of the belief that I had read that the formation was INSIDE the EH, but in a previous thread on this forum it was explained to me that I was wrong and why.
  5. Nov 11, 2011 #4
    Thanks, makes a bit more sense when its outside the EH.
    Are the particle pairs just vacuum fluctuations, and to obey conservation laws the negative one goes into the black hole and reduces the BH total energy and mass. The other positive particle is then emitted from the BH and adds energy and mass to the surrounding space so therefore conservation is maintained?
  6. Nov 11, 2011 #5


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    That's my understanding.
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