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  Black hole event horizons as "firewalls"Jul 21, 2012 5:31 AM PDT | url
 
Added 2 new A* pages:Man this is a long conversation! Gonna go through next week, too. What more will we learn about trees?!? Anyway after that the ultra-violence starts and lasts for pretty much the rest of the episode, so maybe I should have more patience for these little chunks of civility. :P
 
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There is a new theory on the event horizon around a black hole--the radius from their central singularity past which not even light can escape their gravitational pull--that stuff falling through the event horizon doesn't just sort of go through without much happening (in that split-second, anyway; because momentarily, as the object gets close to the singularity, it's supposed to be pulled apart in long strands ("spaghettification" :P) by the stress of differences in the gravitational force across it), but instead more or less gets destroyed at or maybe just past the event horizon. Two research papers on this have slightly different ideas of exactly where/when that destruction would take place; they can be found here and here (I got those links from this Sixty Symbols video on the topic, but I can't really recommend that one as it meanders awfully and is not very clear.)
 
This idea that the event horizon is destructive came from thinking about the quantum properties of the Hawking radiation emitted by black holes--that's where a particle/antiparticle pair spontaneously appears right next to the horizon (these are also appearing everywhere in the universe at all times as far as we know, even RIGHT BEHIND YOU AAAUGH), but instead of annihilating each other instantly, as usually happens in the rest of space, one gets sucked into the the event horizon, while the other is flung away--so one is eaten by the black hole while the other escapes, and these escaping particles are what form this theoretical Hawking radiation.
 
But these two particles, because they were created by the same event, or something, are also entangled, which means that if one is acted upon and undergoes a change of some kind, its entangled pair particle, no matter where it is in space, also undergoes that change. Pretty wild and not really understood well, but this "quantum teleportation" has been verified experimentally.
 
The particle that got sucked into the black hole should in theory be accelerating at an incredible rate and having all sorts of ridiculously energetic things happening to it as it approaches the singularity, and so its entangled partner should also be getting supercharged or something, even though it's just drifting through space away from the hole. So the theory (to the small extent that I can fathom it, at least) goes that around the event horizon of an "old" black hole--one that's had time to expel an appreciable amount of these entangled particles as Hawking radiation--you'll have all these supercharged Hawking particles forming a veritable "firewall" around the event horizon, powerful enough to atomize anything falling in more or less immediately.
 
Or possibly I've read all that wrong! In any case, if you were planning on doing some black hole diving any time soon, you may want to wade carefully.
 
 
 
 
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