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Virtual particle and event horizon

  1. Jul 26, 2004 #1
    Was wondering: In Hawkins's " Univers in a nutshell" book, he talks about the behavior ov virtual particle pairs around the event horizon of a black hole. My understanding is that one of the antiparticle of the pair can be absorbed by the black hole. This makes for the release of the particle ( wich is then sort-of materialized out of "nothing" ) into space and for the blackhole loosing some mass from the absorbtion of anti-matter particle. If my understanding is correct, what I am really curious about in this case is: Would it always be the anti-particle that gets sucked in the black-hole and if so then WHY ?
    Also, what type of particle are we talkin about ? I figure you can have virtual anything but wich one is it in space ??
    Very much apreciate any input on this , Thank you !

    Hippy :confused:
  2. jcsd
  3. Jul 27, 2004 #2


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    The rates of absorption of particles and antiparticles would be equal, it's just a random happenstance which one has the component of momentum toward the horizon. But if the surviving particle is an antiparticle, it wil quickly annihilate with all the regular matter that accumulates near a black hole, producing photons. I believe there are proposals to try to detect these photons, which would have a characteristc spectrum, e.g. 1022 eV for electron pair annihilation.
  4. Jul 29, 2004 #3
    Not my field of expertise this (what is!), but isn't the photon its own anti-particle? So when 'virtual pairs' of photons appear either side of the event horizon, the one that suddenly appears outside, is just a photon - ie not an anti-matter particle. The energy this photon has comes from the mass of the black hole.

    SelfAdjoints description of anti-particle annhilations above is of course the solution to your original question about why you don't see antiparticles being emmitted.
  5. Aug 15, 2011 #4
    I am also confused. Rereading Gribbin on this he quotes Hawking saying that the Universe as a whole gains energy from the black hole itself when any antiparticle annihilates. How is this possible if the black hole is, technically, not a part of the universe, at least that part beyond the event horizon. I cannot understand why both the universe at large and the black hole both do not gain mass/energy. Is Hawking saying that this is a (statistical) event brought about by the decreasing density of the Universe due to its expansion. Is this where he gets the idea that omega must be 1 plus a (tiny) bit, because, if so, he seemms to be trying to have it both ways. Going back to read Penrose and Davies.
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