"We show that when a charged particle goes in, it adds a soft photon to the black hole. So it adds hair to the black hole. And more generally if any particle goes in—because all particles carry mass and are coupled to gravity—they always add a soft graviton. So there’s a kind of recording device. These soft photons and gravitons record information about what went into the black hole—infinitely more information than we previously believed is recorded by this mechanism. Now whether all information is recorded by this mechanism… I'm pretty sure the answer to that is no, but there are generalizations of this mechanism and then it’s a lot more confusing."
They're showing in this model that perhaps, the event horizon of a black hold acts like this kind of abacus, pushing the photons suspended at the edge of the horizon a little bit in, a little bit out, recording what has fallen over that horizon during the life of the black hole.
That's really, really cool.
Here's a great lecture on this question of "well don't we need experiments? Is this all crazy physics conjecture?"
http://www.cornell.edu/video/nima-arkani-hamed-philosophy-of...
Black holes are the phenomena where quantum mechanics and gravity collide most intensely, and even theories of black hole physics compatible with both GR and QM are major achievements.
Edit: Although I agree the article is fairly opaque.
Edit: I apologize for being argumentative. Your question is somewhat intrinsic to the foundation of theoretical physics; given what we "know" now, what else can we logically deduce? There is no absolute answer, but that is part of the fun. :)
That's one way to do physics: You start with conjecture and try to find ways to prove it. (You can also do the reverse, find some unexplained thing and derive rules.)
In this case it might be millennia before we can prove it though.
The only observations we have are of supermassive objects. Do they have event horizons? We assume so, but no one really knows.
It must be because the complex math underlying these findings can not accurately be expressed in human language.
Discussion about these soft particles, zero-energy photons and gravitons, being added to a vacuum changing its state out to infinity is pretty fascinating. I would have liked him to explain a little more in-depth how one of these particles could have no energy but still have a spin, though I imagine that's left to the reader to go find the papers that define it.
