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Question about black holes

  1. Feb 28, 2009 #1
    the URL above says that black holes can decay, but I don't understand, if the black hole sucks in an antiparticle and the particle gets ejected in the opposite direction, doesn't the event horizon of the black hole stay the same? How does it get smaller??

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  3. Mar 1, 2009 #2
    The problem is that those particle/antiparticle pairs are energy from nothing. Normally they would destroy each other and there would be no net loss or gain. However, when one is pulled into a black hole, and its pair escapes then the one that got away is new matter from nothing. Since this matter must come from somewhere it comes from the black hole.
  4. Mar 1, 2009 #3


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    well it depends on what you mean by "nothing", which semantic use of "nothing" you anticipate here.. it is not nihilo, it is the energy-density, vacuum of particles which creates particle-antiparticle pair.s
  5. Mar 1, 2009 #4
    One must be careful here with the definition of energy. The process of particle-antiparticle creation near the event horizon is defined locally. But then, one must look at the global effect, where spacetime is no longer flat as was approximately used in the previous setting, locally near the event horizon. It turns out that the blackhole sucks in negative energy and spits out at infinity positive energy. So its mass deos decrease, and therefore it does shrink.
  6. Mar 5, 2009 #5
    Actually, nothing gets ejected form black holes, what happens, is that all matter that gets sucked up by the black hole goes into the black hole's center or core where it gets destroyed. Also, about the event horizon: most of the time it stays the same, but depnding on what is going on around it, it can change. For more information look at my post, why white holes don't exist. It will explain why black holes are one way.
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