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Whatever happens in there is not falsifiable nor provable to the outside. If for (amusing) example the interior consisted of 10^100 Beatles clones playing "Number Nine" backwards, do we know how to unscramble the Hawking radiation to divine this? The same question applies to this new firewall furor. So of what use is a description of the interior to our physics on the outside?

The only possibility of usefulness I can see is if our own universe can be described as an interior up to the cosmic horizon in de Sitter space. But that's only an "if".

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I am almost tempted to downvote this since the question is formulated in a very confrontational tone, which could ignite unconstructive flame wars about legitimate black hole physics ... –  Dilaton Apr 10 '13 at 19:32
@Dilaton: meh, looks like a legit question asked out of good faith to me. The Beatles thing was a joking example. :) –  Manishearth Apr 10 '13 at 19:44
Usefulness is a much stricter criterion than falsifiability. –  Ben Crowell Apr 10 '13 at 20:37
How about the study can lead to new methods, techniques, ideas... that may be useful in solving other problems. –  MBN Apr 10 '13 at 20:51
@Dilaton: No it's not. Lubos' comment contained a personal attack. The question itself contains none. It just questions a part of physics; which is legitimate. This is not a war. Nobody is attacking, you don't need to defend yourself. I don't see any part of the question which is confrontational. –  Manishearth Apr 11 '13 at 10:09
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Simply because our final goal is a set of laws of physics that describes any part of the universe equally well. Let's say a physicist jumped into a black hole and saw that the interior of the black hole was composed entirely of John Lennon clones. His last thoughts before getting spaghettified would be "why?". From his perspective, physics is incomplete.

Sure, we probably can't use it to predict anything -- but modern physics is much less about predictions and much more about having a beautiful, mathematically rigorous model of the universe. Mathematical models with discontinuities usually aren't "beautiful", and John Lennon in black holes counts as a discontinuity if we take general relativity as our mathematical model of the universe. Which would mean that we will eventually have to replace our model (which is why knowing as much as we can about the inside is important). Besides, if our current theories partially fail inside a black hole, we need to patch that up.

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Does the situation not have some analog in describing the physics of other verses in a multiverse, perhaps? In this case also the alternate regimes appear inaccessible. Perhaps one can talk about "gravity leaking between branes" in the verse case, or of "entanglement bridging the event horizon" in the BH case. But if we can agree that nothing that occurs in the "possibly different physics" of verses or BH interiors has any substantive effect on our physics right here, then isn't it justified to ignore the other stuff? I guess it depends where one draws the line between "curious" and "relevant" –  Andrew Palfreyman Apr 11 '13 at 5:06
@AndrewPalfreyman: No, it doesn't. We can't jump to other universes. We can jump into a black hole. –  Manishearth Apr 11 '13 at 8:52
Your point is well-taken. I would however have inserted the word "yet" in there re. hopping verses. And perhaps, in the interest of frankness, this as-yet-hypothetical process might putatively partially involve jumping into a black hole :) –  Andrew Palfreyman Apr 11 '13 at 11:14
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Whatever happens in there is not falsifiable nor provable to the outside.

General relativity predicts this, but a) no one has ever checked experimentally, and b) it seems to be incompatible with the rules of quantum physics. Every attempt at mixing quantum theory and GR has produced results like Hawking radiation that tell us that the black hole interior and exterior are not completely decoupled.

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But isn't that the point? - that, although you can indeed dive in and do some experiments, there's no way you can tell the physics community back here anything about it. –  Andrew Palfreyman Apr 11 '13 at 5:07
Who says that the physics community will remain "back here"? I can throw the Earth including all of the communities into a black hole – whether or not such an experiment is legal. Nature surely has prepared an answer to what the people will feel and a good theory of physics must be able to answer that, too. –  Luboš Motl Apr 11 '13 at 6:41
As I mentioned in my original question, perhaps we already inhabit such an interior. –  Andrew Palfreyman Apr 11 '13 at 11:06
@LubošMotl AFAIK we already proved that there exist undecidable statements in most branches of mathematics, why shouldn't there be undecidable physical questions? –  Bakuriu Apr 11 '13 at 11:58
@AndrewPalfreyman: The existence of event horizons is an untested prediction of GR. Probably true, but we won't know until we've actually tried dropping a flashlight past where we think an event horizon is. –  user1504 Apr 11 '13 at 12:22
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Can we be sure today that we'll never have some sort of faster-than-light travel, some unthinkable technology that transcends spacetime, or some other way that the black hole interior ceases to be unreachable and unknowable?

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This should be a comment, not an answer. –  sjasonw Apr 16 '13 at 23:43
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From my limited understanding of LHC physics, it has not been ruled out that particle accelerators can create subatomic-size objects which would behave very much like black holes, except for the sucking up of matter. Maybe this or other ways of creating black holes on demand could provide limited insight into their inner workings.

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