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Even in empty space virtual particles can constantly pop in and out of existence in pairs, when 1 of the pair fall into the black hole while the other escape this is hawking radiation but black hole feeds on virtual particles so I am confuse when people says black hole lose mass via hawking radiation. Are they mistaken or did I wake up on the wrong side of bed?

user6760
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    You can forget everything about the gory details of Hawking radiation and simply fall back on the third law of thermodynamics. No physical body can have a temperature of 0K, hence even a black hole has to have a radiation temperature that is finite. When space is colder than the black hole, it will lose mass-energy, when space is hotter, it will gain mass-energy. – CuriousOne May 19 '15 at 03:11
  • @CuriousOne when space is colder than BH do you mean radiation can escape from a BH and I supposed that's hawking radiation beside I never heard any prison breaks in event horizon have you? – user6760 May 19 '15 at 04:43
  • Have a look at the duplicate I've suggested. If if you insist on the virtual particle metaphor then the black hole swallows particles with a negative energy, so its total energy decreases. The escaping positive energy particles make up the radiation. – John Rennie May 19 '15 at 05:12
  • @JohnRennie oh I see what you mean I have a hard time reading the duplicate. – user6760 May 19 '15 at 05:22
  • The black hole and the radiation field in space are basically at different temperatures. The second law of thermodynamics tells you how that plays out: heat moves from hot to cold, so the direction of the heat flow is given by whichever part of the system is colder. That's where the heat will go, and since heat is energy, that's where the mass-energy will go. That nothing can escape from a black hole is the prediction of a macroscopic theory with an effective temperature of 0K. It's correct for the short term evolution of a black hole, but it's not the whole story. – CuriousOne May 19 '15 at 05:29
  • @CuriousOne is that's why Stephen Hawking claims ideal black hole doesn't exist? a black hole(>3K) can evaporate becoming smaller and hotter (3rd law), then according to 2nd law black hole(<3K) can grow bigger and colder is this what you mean? i assume temp of space is 3K approx. – user6760 May 19 '15 at 05:41
  • @CuriousOne: what you say is of course perfectly true, but that doesn't mean it isn't interesting to look into the precise mechanism. – John Rennie May 19 '15 at 06:22
  • Yes, that is what I mean. I can't speak for Hawking, but to me this breaks down along these lines: there is no observational evidence that thermodynamics is violated, so I have no reason to doubt that it's valid. If it's valid, then it can make some trivial statements about black holes like the one above. The problem is that there probably are no black holes with a temperature near or even above that of the CMB, which makes observations and experiments impossible. We may find microscopic black holes that have a much higher temperature and very short lifetime in accelerators, though. – CuriousOne May 19 '15 at 06:23
  • @JohnRennie: All I am trying to do is to motivate to the OP that the idea that black holes can evaporate is not totally crazy, not even if we don't know anything in detail about general relativity and quantum gravity. Of course there is a world of theory beyond this trivial insight, but I can't speak to that, nor would I want to without some observational data, which I still hope will come during our lifetimes (hope springs eternal...). – CuriousOne May 19 '15 at 06:28

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