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First off: I am not familiar with the details of quantum mechanics or relativity. My understanding of Hawking radiation is as follows: Pairs of particles and anti-particles can and will spontaneously form in space and when that happens near the event horizon of a black hole the anti-particle might fall into the black hole and the particle not, effectively causing the black hole to lose mass.

Now, this is totally fine with me. The thing I do not understand is: Why do more anti-particles fall into the black hole than particles? If these pairs pop up randomly, shouldn't the effects of Hawking-radiation and anti-Hawking-radiation cancel out?

Qmechanic
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schtandard
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  • You may find the answer to your question here: http://physics.stackexchange.com/q/30597/ – mpv May 26 '14 at 05:10

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What do you mean, "cancel out"? Even if a particle and its antiparticle annihilate, energy is still conserved, e.g. an electron annihilating with a positron gives two photons (well, depending on their energy). The radiated energy can't just vanish without a trace.

Brian Bi
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    Well, the way I understand it, the anti-particle has a "negative mass", so that when the anti-particle falls into the black hole, then it gets lighter. This should however also happen with "normal" particles at the same rate, shouldn't it? – schtandard Apr 25 '14 at 19:41
  • Where did you read this? – Brian Bi Apr 25 '14 at 19:45
  • For example in the German Wikipedia. – schtandard Apr 25 '14 at 19:55
  • I can't read German, but I put it through Google Translate and it appears to be something like: "one partner falls into the black hole, while the second partner can escape". It doesn't say matter falls in and antimatter comes out. – Brian Bi Apr 25 '14 at 20:00
  • Well, what it says is pretty much what I wrote above. Two particles (they even talk about virtual particle-pairs) spontaneously form, one with positive and one with negative energy (which is equivalent to mass). When the particle with negative energy falls into the black hole, it becomes lighter and the escaping "real particles" make up the Hawking radiation. – schtandard Apr 25 '14 at 20:22
  • Precisely---which means all the particles that escape have positive energy. – Brian Bi Apr 25 '14 at 20:22
  • Right, which is exactly my question: If this process of pair creation is random, why would more particles with negative energy fall into the black hole than with positive energy? – schtandard Apr 25 '14 at 20:28
  • You can't have negative energy particles outside the event horizon. I can't say more because my understanding of GR is extremely limited. – Brian Bi Apr 25 '14 at 20:30
  • Well, why not? I mean, of course it would not be stable, but why should the same effect not happen with the roles of the particles switched? – schtandard Apr 25 '14 at 20:33