Would energy be seen to "flow" to the outside of the black hole? Through what mechanism?


The observer inside the event horizon does not observe Hawking radiation--- this is a pure external effect.

  • $\begingroup$ Not Hawking Radiation per se, but surely some mechanism by which energy is disappearing must be observed from the inside of the black hole. $\endgroup$ – user1247 Apr 15 '12 at 19:18
  • $\begingroup$ Why should it be? There is no local mechanism--- the inside is a construct of the quantum states. You don't see stuff flying out in the future region. There is what I consider the likely possibility that for charged and rotating black holes you end up going through the middle, missing the singularity and coming out the same black hole. It is in the outgoing leg of your journey, on your way to exiting the event horizon that you might see the Hawking radiation. I didn't work it out, and I don't think this past region was the intention of your question. $\endgroup$ – Ron Maimon Apr 15 '12 at 20:08
  • $\begingroup$ Maybe I'm not understanding your response. Are you saying that for an inside observer, the black hole would not appear to be losing mass? $\endgroup$ – user1247 Apr 15 '12 at 20:36
  • $\begingroup$ @user1247: Yes, I am saying that. The inside observer can't measure the mass of the black hole. $\endgroup$ – Ron Maimon Apr 15 '12 at 22:53
  • 1
    $\begingroup$ Why couldn't an inside observer measure his distance from the singularity and the rate that he was falling toward the it and use that to compute its mass? $\endgroup$ – Dan Is Fiddling By Firelight May 15 '12 at 13:31

This is an incomplete answer, but I would bring two important points here:

1) When observer moves freely in GR, he/she observes locally flat spacetime up to quadratic corrections in 3-distance from his/her worldline. Hence, if you are falling into a black hole, you shall see the same as what you would see, if you were in Minkowski spacetime throughout all your infall, unless you start measuring the tidal forces. Hence, you shall see no Hawking radiation generated around you at all, until you come so close to the singularity, that the tidal forces shall become very strong and you shall eventually observe local generation of particle-antiparticle pairs around.

However, this doesn't exclude the possibility of observing some flux falling with you from the infinity into the black hole.

2) The notion of particles in GR depends on your reference frame. If you imagine an observer located above the event horizon, accelerated in such a way that he/she has stationary spatial coordinates, he/she will not be moving freely due to acceleration and shall see particles/antiparticles generated around, some of them falling under the horizon, and some of them flying away from the black hole. If you consider some static asymptotically flat coordinate system, you shall see that some particles in this system shall escape to infinity and shall be visible to the remote observers, moving freely with respect to that system.

To conclude, you shall not observe Hawking radiation generated around you, though you might possibly see already existing particle-antiparticle background (possibly, exactly Hawking radiation).


An observer inside a black hole is impossible because a black hole has no internal structure (otherwise it would be possible to transfer information from inside by moving massive bodies.

Also no information can be under the horizon because this would mean information loss which is impossible thermodynamically.

So any black hole is an uniform body without internal structure.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.