15 ms·
Doesn’t the black hole just delay the information, not destroy it? Things that “fall in” from our perspective just fade down into a static low frequency frozen
by clord 4y ago
Doesn’t the black hole just delay the information, not destroy it? Things that “fall in” from our perspective just fade down into a static low frequency frozen image on the horizon, and the remaining trip to the horizon as seen from the outside takes infinite time.
The falling perspective likewise loses timely access to information about the entire universe as the singularity fills their view.
I don’t see a paradox. Just the strange behavior of time at the limit.
- wanda 4y agoThat's not the paradoxical part. Matter goes in, sure. But before it goes in, it is something, it has a form and a composition, it is in a state and it contains information of its prior states as well. The part that is problematic is that matter that enters the black hole is only returned to the universe as anonymous radiation. The universe is stateful, and while not all processes in the universe are reversible, matter and energy do encode the states that led to their present state and thus the prior states can be inferred (by a hypothetical, powerful enough computer, for example). The problem with black holes is that the Hawking radiation from a black hole does not encode any information about its prior state.
- lisper 4y agoI think you missed the GP's point, which is that matter is never "returned to the universe" because from any frame of reference outside the horizon, the matter takes infinite time to transit the horizon, so it never actually appears to enter the hole.
- dllthomas 4y agoHow does that remain true after the black hole has evaporated and there is no longer a horizon?
- lisper 4y agoDisclaimer: we are at the hairy edge of my knowledge here, so what I am about to tell you could very well be wrong. Hawking radiation has never actually been observed. It is just something that pops out of the math if, as Sabine rightfully emphasizes in her video, you make certain assumptions. And one of those assumptions is that you have a fully-fledged black hole, i.e. an object that actually contains mass beyond the event horizon. We are used to thinking of this assumption as having actually been confirmed by observation, but it is not actually true. No one has ever actually observed a black hole, notwithstanding that we've ostensibly taken a picture of one. That image was of the radiation emitted by an accretion disk, not the black hole itself. Black holes themselves are, obviously, impossible to image. So we don't actually know whether black holes actually exist or not. The only thing we've directly observed is their gravitational effects, and the gravitational effects of an actual black hole are indistinguishable from having all of the mass of the hole actually resident just outside the event horizon. What actually happens at the horizon is beyond the reach of our current theories because there both gravity and quantum effects are significant, and we do not yet have a consistent theory of quantum gravity. Everything we think we know about black holes is actually the result of taking GR and QM and framming them together in some ad hoc way by adding simplifying assumptions which may or may not actually be true. This is the point Sabine was trying to make: the black hole information loss paradox is not a problem with physics, it's a problem with our current theories. We simply don't know how the universe actually behaves in the presence of extreme concentrations of mass/energy. The only thing that the BHILP actually tells us is that either GR or QM -- or both -- are wrong, mere approximations to the actual truth in the same way that Newtonian mechanics turned out to be an approximation to the actual truth (one that happens to work extremely well in weak gravitational fields). But no one has a clue which one is wrong or how despite 100 years of effort. And one of the reasons for this is that we have no data, and no reasonable prospects for obtaining it. So we may just have to make our peace with not knowing.
- daxfohl 4y agoI think that's the point. From an outside perspective the black hole will evaporate before the thing falls in. Thus a thing can never fall in. From its perspective the hole will emit more and more intense radiation and finally evaporate just before it hits the horizon. If true, I think you can go even further and say no black hole can completely form; the collapsing matter just gets exponentially closer to being fully black until the effect of the Hawking radiation outweighs the gravitation, but it all evaporates before going fully black. No? (This latter part assumes there's some Hawking radiation or equivalent from pre-black holes as well. And I'm not sure whether that would be unitary or not, so it may not resolve the information paradox anyway). (Edit: I think the pre-Hawking radiation would be unitary, since the only reason Hawking radiation is not unitary is because BHs don't have information, but pre-black holes are not black holes. So doesn't that solve the info paradox? Without resorting to holographs and whatnot? Where's the error?)
- dllthomas 4y agoMaybe, but I think if it were easy to show that black holes (for whatever definition is important here) never actually form, the physicists would have noticed.
- daxfohl 4y ago100% agree, but I'm still not seeing the flaw in the argument.
- GoblinSlayer 4y agoWhen they are paid for research of black holes, it becomes easy to overlook their absence. They can also say they do hypothetical research, if black holes don't form by collapse maybe they form by other means, e.g. primordial black holes.
- Raidion 4y agoTotally uninformed here: Have we proved the Hawking radiation is without information (or enough of it), or is it just 'encrypted' at a level we can't distinguish from noise?
- mannykannot 4y agoThis seems to address it (from the article): "[Hawking] radiation is thermal which means it’s random except for its temperature, and the temperature is inversely proportional to the mass of the black hole. This means two things. First, there’s no new information which comes out in the Hawking radiation..." Its mass is one of the few things we know from the outside.
- phendrenad2 4y agoHow do we know it's thermal? How do we know there aren't small fluctuations that are too small for us to detect millions of miles away?
- mannykannot 4y agoAFAIK Hawking radiation has never been detected. It is hypothesized on the basis of current theories of quantum mechanics and gravity, and those assumptions imply a thermal distribution of energy. So, we have a reason to think that Hawking radiation occurs and has this property, while no-one so far has proposed a mechanism that would encode data on it.
- tsimionescu 4y agoIt's important to understand that Hawking radiation is not something we've observed and have noticed seems random. Instead, Hawking radiation is a prediction of a mathematical model. In that model, Hakwing radiation is purely random. If I remember correctly, Hawking radiation is postulated to arise because of fluctuations in the vacuum giving rise to virtual particle pairs. Normally, these would annihiliate back almost instantly. But, when such an event happens near the event horizon, one of them may fall into the black hole, leaving the other one to "escape", and appear as if the event horizon is emitting radiation. Since this radiation is caused by random fluctuations in the void outside the event horizon, it can't be correlated with anything past the even horizon, so it can't carry information about that.
- SnowHill9902 4y agoWhat is problematic about that? In what way does it violate the second law of thermodynamics? If anything, it seems like a great example of the natural tendency towards disorder. Also, it’s not possible to infer macroscopic prior states even with an infinitely powerful computer. When you mix water at different temperatures, entropy is irreversibly increased. It’s not possible to tell the initial temperatures just from the final state.
- jfengel 4y agoIt's a subtle point. Several key theorems of thermodynamics rely on the ability to count unique states. If you could evolve the exact same state in two different ways, the proofs would fail. That's how thermodynamics derives indistinguishable macro states from distinguishable micro states. Throw that off and thermodynamics stops working. Since it has worked well so far they're reluctant to throw it out. Something has to go, and since they already know there's something funny going on where black holes meet quantum mechanics, that's the lowest hanging fruit.
- SnowHill9902 4y agoSo you are saying that if I solve the Schrödinger's equation for all the particles that make up her I could know where my wife wants to go out for dinner?
- wanda 4y ago> In what way does it violate the second law of thermodynamics? If you read my comment, you will find no mention of the second law of thermodynamics or any violation of said law. In fact, black holes need to evaporate in this way in order to comply with said law of thermodynamics. > When you mix water at different temperatures, entropy is irreversibly increased. It's not possible to tell the initial temperatures just from the final state. It is still water, however. You may not be able to say what temperatures W(a) and W(b) were from W(c), but you could at least say that W(c) may actually be W(ab) i.e. may be the mixture of two bodies of water W(a) and W(b). Bring the same water to a black hole and you have: W(a) went into a black hole and x came out, where x is some random heat. If you detect the heat x, what could you say about anything that may have been before? If W(a), W(b), Chair(a), Xylophone(g), Stone(f), Person(z) or anything went into the black hole, only heat x comes out in the end.
- andi999 4y agoWhat is the difference of this paradox to a particle entering a gas container, thermalizing, and the ejecting the particle (evaporate the gas). Thermal states is described by macroobservables only.
- lamontcg 4y agoBut that just suggests that at some high enough energy that QM becomes nonlinear and singular and nonreversible and information is destroyed.
- mannykannot 4y agoI have wondered that, though without knowing enough to even figure out if it is a reasonable question. One follow-on thought I had was this: what about the matter that becomes the black hole when it forms? When a star collapses into a black hole, where does the event horizon first appear?
- lupire 4y agoWhat do you mean "where"? It appears at the region one Schwarzchild radius away from the center.
- mannykannot 4y agoSure, but the Schwarzchild radius is a function of the mass within it. I'm thinking by analogy to a galaxy or globular cluster, which has enough mass to be a black hole, if it were dense enough, but it will not become one unless and until some dissipative process has caused it to collapse towards its center. When this happens, I am supposing that the black hole will first form in the center (where the gravity well is deepest), with a large part of the cluster mass initially outside of it, and grow as the friction continues to feed mass into it. If this is, in fact, a reasonable model, would something similar happen in a collapsing star? (Only much faster.)
- amelius 4y agoHmm I thought the laws of physics were time-reversible, but then I found this: https://www.wolframscience.com/nks/notes-9-3--time-reversal-invariance/ https://www.wolframscience.com/nks/notes-9-3--time-reversal-...
- rssoconnor 4y agoSame. https://www.youtube.com/watch?v=L2idut9tkeQ https://www.youtube.com/watch?v=L2idut9tkeQ is the relevant episode from Space Time.