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Why should rotating black holes emit particles?

  1. Jun 20, 2012 #1
    In a brief history of time it says theft 'according to the uncertainty principle rotating black holes should emit particles'. However I do not understand why rotating black holes need to emit particles according to the uncertainty principle.

    I do understand why black holes emit particles it is just the rotating black holes and The uncertainty principle thing that I do not understand.

    Thanks in advance.
  2. jcsd
  3. Jul 27, 2012 #2
    My understanding is that Hawking radiation is a theory used to explain how black holes conserve energy. For example, we think blackholes grow in size as they consume matter. Any particle that enters the Schwarzchild radius (SR) of a blackhole is absorbed. QM purposes that virtual particles in the quantum field 'pop' in and out of existence all the time, but that they come in particle/anti-particle pairs that quickly annihilate one another, thus conserving energy and momentum in the universe. Hawking used this notion to theorize that virtual pairs that happen to 'pop' into existence on the event horizon (SR), are split up and do not annihilate eachother as they usually do. One particle 'falls' into the black hole, while the other escapes and appears as Hawking Radiation. Since the black hole grows fractionally by swallowing one particle, and since the other particle in the pair is emitted as radiation, energy and momentum are conserved.
  4. Jul 28, 2012 #3


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    A black hole in General Relativity alone does not emit Hawking radiation and conserves energy.

    Hawking radiation causes black holes to shrink.

    @Confuses: There is nothing special about rotating black holes. All black holes are assumed to radiate particles (mainly photons). Rotating black holes are just the most common type of them in space.
  5. Jul 29, 2012 #4
    There is something called Penrose Pair Production (PPP) which occurs with static black holes but increases significantly for rotating black holes with high spin-

    'Magnetohydrodynamics on the Kerr Geometry' by A Mueller
    pages 47 & 48
    Last edited: Jul 29, 2012
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