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The Black Hole information loss problem is unsolvable
- mellosouls 6y agoThe recent discussions here on the article Dr Hossenfelder is sceptical about: https://news.ycombinator.com/item?id=24940086 https://news.ycombinator.com/item?id=24940086 https://news.ycombinator.com/item?id=25092231 https://news.ycombinator.com/item?id=25092231
- AnimalMuppet 6y agoNote, however, her comment: > This is why the headline that the black hole information loss problem is “coming to an end” is ridiculous. Though, let me mention that I know the author of the piece, George Musser, and he’s a decent guy and, the way this often goes, he didn’t choose the title. She's against where the popular media wants to go with the article, and against the headline, but not so much against the article itself.
- tsimionescu 6y agoI think she also believes that, since the problem is not even close to being testable at this time at least, it is not really worth studying to the current extent - any theories about it would only remain mathematical constructs, not physical theories.
- AnimalMuppet 6y agoShe said that > In my opinion, the black hole information loss problem is the most overhyped problem in all of science, and I say that as someone who has published several papers about it. So I'm not sure that she thinks it isn't worth studying. I think she thinks it isn't valid to declare that something "solves" it, though.
- beervirus 6y agoI fully expected this to be crankery like some of this author’s other stuff. But this one makes a lot of sense.
- aaron695 6y ago> crankery like some of this author’s other stuff. Link?
- AnimalMuppet 6y agoFor me, this was the money quote: > The black hole information loss problem is not a math problem. It’s not like trying to prove the Riemann hypothesis. You cannot solve the black hole information loss problem with math alone. You need data, there is no data, and there won’t be any data. Which is why the black hole information loss problem is for all practical purposes unsolvable. We lack experimental data. We lack a way to get experimental data. All we have is some beautiful mathematics. That's nice, but we don't know if it corresponds to reality. That's true of the paper under discussion, and it's true of all the other papers proposing solutions as well.
- coliveira 6y agoThis is not a convincing argument. We may not have data, but as in other problems in physics we may have indirect ways to get evidence. These indirect ways may not be apparent nowadays, but may become in the future.
- sampo 6y agoAs far as I understand, Nordström's second theory of gravitation is a mathematically self-consistent theory for gravitation, and the only way to decide between it and Einstein's theory was by comparing to observations. https://en.wikipedia.org/wiki/Nordstr%C3%B6m%27s_theory_of_gravitation https://en.wikipedia.org/wiki/Nordstr%C3%B6m%27s_theory_of_g...
- tsimionescu 6y agoSure, but until such a time, the problem will remain unsolvable.
- eternalban 6y agoIntuitionism has been knocking on theoretical physics' door for a while now.
- Kranar 6y agoIndirect data is still data. What she's saying is that math equations aren't data and hence math equations alone can't solve this problem.
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- xwdv 6y agoIf it’s unsolvable then now what? What does it mean for humanity?
- qw3rty01 6y ago> These solutions are all mathematically consistent. We just don’t know which one of them is correct. And why is that? It’s because we cannot observe black hole evaporation. > You need data, there is no data, and there won’t be any data. Which is why the black hole information loss problem is for all practical purposes unsolvable. She didn't say it was inherently unsolvable, only that it was practically unsolvable. There's still the possibility that it could be solved with some other data that doesn't require observing black hole evaporation.
- whimsicalism 6y ago> And without data, the question is not which solution to the problem is correct, but which one you like best. I think this is correct to some extent, ultimately unavoidable, and some assumptions can be "inferred" as more reasonable than others, even in the absence of falsification. By Sabine's stance, the problem of induction [0] hasn't been "solved" because we actually have no reason to assume that past events are at all related to future events. So when we say that induction is possible, we say so because we "like best" that theory of causality, rather than my alternate theory that when you finish reading this sentence, all physics will cease to function and the universe will end. It didn't happen, but we had no reason to know so ahead of time deductively. However, it is still reasonable (in my view) to believe in induction. So sure, it's perhaps 'unsolvable', but if a plausible explanation comes around that is consistent with modern physics that seems good to me. [0]: https://plato.stanford.edu/entries/induction-problem/ https://plato.stanford.edu/entries/induction-problem/
- tsimionescu 6y agoAs far as I understand, there are plenty of plausible explanations that are consistent with modern physics. The problem is finding out which one of them (if any) is right, since they are not all mutually compatible.
- whimsicalism 6y agoSure, but I think there's a difference between "if we conjecture this additional effect that has never been observed but is not inconsistent with observation, then we see this thing" vs. "actually this is sort of resolved by a straightforward application of solutions to models we already had of effects we have already observed"
- shaded-enmity 6y agoI'm confused, isn't the whole schtick around past events being related to future events the basis of causality?
- ethanbond 6y ago
- pjungwir 6y agoAs a non-physicist, I've always been hung up on a much simpler paradox: how does radiation escape from a black hole? I thought even light could not escape? Is there an explanation to that?
- whimsicalism 6y agoBasically.. and this is somewhat lay: in quantum mechanics, there is fundamental randomness. Part of that randomness means that in space, virtual pairs of particles can be formed right at the barrier between being able to escape and not escape. Normally, these particles annihilate each other - however if one crosses the threshold and is not able to escape, it can't annihilate the other particle and that escapes as radiation.
- colejohnson66 6y agoSo similar to “anti particles”?
- deleted 6y ago[deleted]
- adzm 6y agoThis is Hawking radiation, which I'm sure wikipedia can explain better than me: https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation > A pair of virtual waves/particles arises just beyond the event horizon due to ordinary quantum effects. Very close to the event horizon, these always manifest as a pair of photons. It may happen that one of these photons passes beyond the event horizon, while the other escapes into the wider universe ("to infinity"). A close analysis shows that the exponential redshifting effect of extreme gravity very close to the event horizon almost tears the escaping photon apart, and in addition very slightly amplifies it. The amplification gives rise to a "partner wave", which carries negative energy and passes through the event horizon, where it remains trapped, reducing the total energy of the black hole. The escaping photon adds an equal amount of positive energy to the wider universe outside the black hole. In this way, no matter or energy ever actually leaves the black hole itself. A conservation law exists for the partner wave, which in theory shows that the emissions comprise an exact black body spectrum, bearing no information about the interior conditions.
- c1ccccc1 6y agoSo this new result is derived semiclassically, right? Which means it was derived using more or less the same assumptions Hawking used to derive Hawking radiation. So couldn't the same objection be made about the claim that black holes evaporate at all? After all, we also have no empirical data about that, and likely won't have such data for a long long time.
- Kranar 6y agoOf course the criticism can also apply to Hawking radiation but it wouldn't be a particularly strong or even novel critique. Scientists already understand that an experimentally unverified prediction in theoretical physics could end up being wrong. If Hawking radiation does end up being wrong, however, it would most definitely result in some groundbreaking insights because Hawking radiation is itself built upon a set of assumptions that have a lot of experimental evidence. The multiple solutions to the black hole information loss problem all depend on a set of assumptions that do not have that same degree of experimental evidence and so the concern is that physicists will converge on the solution that they find most comforting, likely based on ideology or whatever is fashionable, rather than converge on the solution that has the most evidence. The article says that getting actual empirical data to determine which competing solution is correct is virtually impossible. So sure, Hawking radiation can be wrong and we have very little empirical data to support it, but it's not a theory that's competing with any other theories strictly on the basis of math equations derived from a set of assumptions. It's a theory that is almost uniquely derived from a pre-existing set of assumptions that do have a large body of empirical support whereas the solutions to the black hole information loss problem are not.
- c1ccccc1 6y ago> It's a theory that is almost uniquely derived from a pre-existing set of assumptions that do have a large body of empirical support. What additional assumptions (on top of the ones Hawking made) does the new calculation use that don't have a large body of empirical support?
- Kranar 6y ago
- sterlind 6y agoNot a physicist, but Hossenfelder didn't clarify well that, unlike previous proposed solutions, this one only relies on standard quantum mechanics and general relativity, not strings or LQG. Similar in spirit to Hawking's original approach, which she did mention. She seems to have a beef with extrapolating (even well-accepted) math, rather than doing experiments. But this kind of work clarifies where the theories clash and break down, how they can work together, maybe even testable predictions. I wonder if she would have been critical of the Casimir effect, back when it was thought to be untestable.
- effie 6y agoCasimir effect prediction had a good theoretical grounding and testable prediction (force between parallel conducting planes). It was clear the effect (not the theory behind it) was is in principle testable in a lab.
- platz 6y agoHowever this result does rely on a very questionable interpretation of a gravitational path integral.
- pontus 6y agoI think this approach is a bit disingenuous. Her claim is that since we can't directly observe black hole evaporation, we can't know which mathematical model is "correct" in describing the phenomenon and that we're therefore just left with picking the explanation that we personally like the best. This same argument can be made about a ton of things. For example, we have yet to observe free quarks directly (due to confinement in QCD), but I don't think people are saying that the quarks model is just the one that we happen to find most pleasing. The reason we are confident in the quarks model is because it makes all sort of other predictions that we can confirm. Who is to say that the various ways of resolving the BH information paradox are indistinguishable simply because we can't observe the evaporation directly? Maybe they make other predictions as well. Generally, I think that we need to be skeptical of various speculative ideas and in many ways we have strayed off course for a while in theoretical physics, but I don't think the answer is to just explore topics and theories that are completely grounded in observations and experiments.
- justincredible 6y ago"vacuum cleaners don’t clean the vacuum" great example /s. Reminds of NdGT being smug about summer daytime getting shorter.
- andrewflnr 6y agoHawking radiation itself is not observed, but she seems willing to take that for granted on the basis of pure math. I don't see a notable difference between that and the theoretical work she's dismissing here.
- DangitBobby 6y agoI don't think so. She states clearly that the paradox simply means some of the underlying assumptions must be wrong. She does not claim to know which ones it must be.
- abdullahkhalids 6y agoYes, one resolution of the paradox is that there is no Hawking radiation, which is what the author almost said > Another option is that the black holes do not entirely evaporate and the information is kept in what’s left, usually called a black hole remnant.
- xevrem 6y agoI still don't understand what they mean by "loss". Why is this even a problem? The information isn't gone, its right -there- in the black hole, which until proven otherwise, is part of the universe. Until someone can prove the universe cares whether the info is in a black hole or not, its not really a problem is it? If anything the universe usually shows it doesn't care what we humans think, its going to do its own thing, regardless: i.e., weak nuclear force and "symmetries"
- whimsicalism 6y agoBut then the black hole evaporates...
- gizmo686 6y agoThe black hole is not eternal. Once it is fully evaporated, you still need to account for the information that was contained within (or accept information loss).
- seppel 6y ago> Once it is fully evaporated, you still need to account for the information that was contained within (or accept information loss). One way to escape this is: * You accept that the Hawkin radiation contains the original information. * But it is scrambled in a reversible way, but so hard that you cannot reverse it with the energie available in the universe. There are nice talk by Scott Aaronson about this, e.g.: https://simons.berkeley.edu/events/theoretically-speaking-series-scott-aaronson https://simons.berkeley.edu/events/theoretically-speaking-se...
- lokedhs 6y agoBut Hawking radiation is black-body radiation. Isn't it just photons where its frequency is proportional to the black hole mass? Where would the information be encoded?
- cli 6y agoI believe this was addressed in the first few paragraphs of the article: this problem is not about 'information', which is a vague phrase. Rather, it is about how black hole evaporation is fundamentally time irreversible.
- keyle 6y agoCan someone tl;dr this mad man's around a bottle of red wine ramble?
- jesuscyborg 6y agoNot true. All you have to do is launch Matthew McConaughey into a black hole and he'll solve it.
- saagarjha 6y agoUnfortunately “love” is difficult to experimentally test.
- deleted 6y ago[deleted]
- zygotic 6y agoCrap. Keep working the problem and... maybe you get a solution. Giving up is for wimps (What are WIMPs? - Universe Today+_)
- tus88 6y agoThe whole "information obeys the laws of physics" crap is just a fiction invented by modern physics to look cool in absence of any real progress for over a century, and to compete with software engineering.
- Causality1 6y agoI don't fully understand the claim that all quantum processes are time-reversible. Aren't there a lot of spontaneous quantum phenomena that aren't?
- mikhailfranco 6y agoCorrect. This is the part of QM known as Interpretations, for which people cannot agree on a single viewpoint, and hence do not agree on which axiom to add to the theory. The measurement / collapse / decoherence / forking-of-worlds / entanglement-with-the-environment is either time-irreversible by definition, or time-irreversible FAPP. For example, Penrose proposes that the gravitational field induces one of these time-irreversible processes: https://en.wikipedia.org/wiki/Penrose_interpretation https://en.wikipedia.org/wiki/Penrose_interpretation
- abdullahkhalids 6y agoQuantum processes are described by Schrodinger's equation, that is a linear differential equation in time. Consequently, it's solutions for every possible boundary conditions are always reversible.
- mikhailfranco 6y agoThe Schrodinger Equation is obviously wrong in gravitational scenarios, because it is expressed in a background classical t that does not exist in GR, let alone a future theory of QG.
- Causality1 6y agoSo if you could measure an atom precisely enough you could calculate exactly when it decayed from a heavier atom?
- miltondts 6y agoMeasuring things is kind of problematic. https://en.m.wikipedia.org/wiki/Measurement_problem https://en.m.wikipedia.org/wiki/Measurement_problem
- wwarner 6y agoHer frustration with the priorities of theoretical physics probably is justified, but in this case I disagree with @skdh. Her claim is that any solution for the BHIP cannot be falsified, and that strikes me as too pessimistic for two reasons. First, look at the results of pushing the theory harder with respect to spinning black holes. Many predictions of Kerr's theory have been observed, even if the ring singularity at the center hasn't. Second, we're observing new black hole phenomena every day, and if black holes really do explode at the end of evaporation, then maybe that is also observable. Sure, Hawking radiation is normally too small to be directly observed, but the theory can be driven into a place where it can make a testable prediction.
- ddxxdd 6y agoI completely agree with this. Ancient philosophers debated the existence of atoms for centuries; then Boltzmann took the theory up to second gear by discovering the implications on temperature and entropy, and then Einstein proved their existence beyond a shadow of a doubt through his work on Brownian motion. It might take centuries of mathematical work to discover an artifact of quantum gravity that's observable within our macroscopic world, but the work must be done.
- avz 6y ago> and if black holes really do explode at the end of evaporation, then maybe that is also observable I suppose her reason to assume we can't observe this is that evaporation takes extremely long time. For example, a solar mass black hole will take about 10^64 years to evaporate [1] (this is approximately 7 * 10^54 times the age of the universe). Note that astronomical black holes are heavier than the Sun, so take even longer to evaporate. I suppose the micro black holes [2] might offer a glimmer of hope, but these objects are entirely hypothetical. [1] https://en.wikipedia.org/wiki/Hawking_radiation#Black_hole_evaporation https://en.wikipedia.org/wiki/Hawking_radiation#Black_hole_e... [2] https://en.wikipedia.org/wiki/Micro_black_hole https://en.wikipedia.org/wiki/Micro_black_hole
- adrianN 6y agoCreating a microscopic black hole is not completely out of our reach. https://arxiv.org/abs/0908.1803 https://arxiv.org/abs/0908.1803 discusses this topic a bit. If the assumptions there are not wrong, and climate change doesn't get us first, creating small black holes might be become possible an a couple of generations.
- shagie 6y agoThe most recent podcast for Star Talk Radio ( https://www.startalkradio.net https://www.startalkradio.net ) which, admittingly is much more of a layman's level than deep science, was about black holes. One of the topics covered in https://www.startalkradio.net/show/cosmic-queries-black-hole-survival-guide/ https://www.startalkradio.net/show/cosmic-queries-black-hole... was about the debate on the black hole information loss problem.
- platz 6y agoOriginal result discussed on Sean Carroll's podcast, Mindscape: https://www.preposterousuniverse.com/podcast/2020/09/21/115-netta-engelhardt-on-black-hole-information-wormholes-and-quantum-gravity/ https://www.preposterousuniverse.com/podcast/2020/09/21/115-... He seems a little non-committal if not skeptical. One telling exchange near the end regarding the gravitational path integral they used: * * * "1:18:41 SC: And there is this trick that you can introduce, ’cause what you’re supposed to do is say, well, integrate up all of the spacetimes that match on to this particular wave function you’re looking at. But the trick is, instead of integrating all the four-dimensional spacetimes that match on to this condition you’re looking at, you can just say, well, I’m going to integrate over all four dimensional spaces, so I’m going to forget about spacetime. I’m just going to do what we call the Euclidean path integral because Euclid just talked about space, not time. And… 1:19:13 NE: Oh, you went there. [laughter] 1:19:15 SC: I did, I did. This is where I’m going. And so it was sort of like you could justify… It’s a trick. It’s a mathematical trick. And it’s very rigorously justifiable in certain simple cases in quantum mechanics, and it certainly has the smell of being correct in certain more subtle cases in quantum field theory. In quantum gravity, what they were doing with it, it just seemed to be a trick so they could get a finite answer at the end of the day, and it was very unclear why it had anything to do with the real world, but they suggested it did. Maybe they were right. And since then, I think we’ve become a little more comfortable with the idea that we can use this trick of calculating quantum gravity wave functions by integrating over the Euclidean path integral, the set of all the spaces that end up looking like what we want, instead of all the spacetimes that look like what we want. 1:20:05 NE: Yes. 1:20:05 SC: And that’s what you’re doing, isn’t it? That’s the kind of wormholes that you’re invoking. 1:20:09 NE: Yes, right. That’s what I was trying to sweep under the rug. 1:20:11 SC: I know. [laughter] And you were right to do so, but I just like to live dangerously here. [chuckle] 1:20:18 SC: So Lenny and Juan have wormholes that are literally good old in spacetime wormholes, and you have wormholes that are in these fake Euclidean spaces that you used to calculate the entropy. 1:20:29 NE: That’s exactly right. Yeah, that’s exactly right. And these fake Euclidean spacetimes have more boundaries. There are more edges than our original spacetime, which means that these wormholes are connecting these… More edges than we have in our original spacetime, and therefore, it’s difficult to make sense of them in terms of the original spacetime that we’ve started with." *
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- BMSmnqXAE4yfe1 6y agoIn what sense thermal radiation is "random"? Normal thermal radiation is only random in the sense that it's very hard to compute all the photons given the initial states of all the electrons etc, but it's possible in principle. Does black hole have an internal state, that depends on the states of all the particles that fell into it? If so, the emanating radiation can be computed from that internal state, so information is preserved.
- mcguire 6y ago"Does black hole have an internal state, that depends on the states of all the particles that fell into it? If so, the emanating radiation can be computed from that internal state, so information is preserved." If I understand, the short answer from Stephen Hawking is "no." The only properties they have is mass, angular momentum, and charge.
- peter_d_sherman 6y agoYou know, it makes me wonder if Black Holes can't be thought of as just giant Fourier Transforms in Space... You know, regular waves (and particles, as waves) go in to the black hole, Fourier-transformed waves (as Hawking Radiation, or whatever else goes out) come out of the black hole... Now you see it... now you don't! Hmm, not to go all crackpot or anything (but to go all crackpot! <g>), now that I think about it, it makes me wonder if disappearing sub-particles do that by Fourier-transforming themselves into smaller sub-particles(!) (as waves!), which then radiate outward in space (undetectably, because they're now multiple smaller/higher-energy particle/waves!) from the point at which they "disappeared" from! If this crackpot theory is true (and let's not kid ourselves, it is a completely crackpot theory! <g>) then NO INFORMATION would ever be lost to the Universe, ever, basically, the Universe would just be doing a whole lot of Fourier Transforms (and Reverse Fourier Transforms!) in the background, all the time, at all particle sizes, but at different time scales relative to that particle size! In fact, if a particle goes out of scope ("disappears") relative to a Fourier Transform, then perhaps Fourier Transforms are what also, equal-and-oppositely CREATE particles! And all of this "creation" and "destruction" of particles -- would be at different beat FREQUENCIES relative to scale! It also leads to a very weird question, which is: What is the relationship of Gravity to the Fourier Transform? And, Is Gravity itself just a Fourier Transform -- just at a specific scale? Also, if Black Holes are Fourier Transforms -- maybe Suns and Stars are too -- just reverse or "Inverse" Fourier Transforms... ?