A physicist once accidentally reformatted a SSD containing the only copy of a paper she had been working on for 6 months. She then got into a heated argument with a data recovery company over whether or not it's possible to destroy information.
Energy can't literally disappear, but whether "information" can depends on just what we define as information, as this is not necessarily the same definition as energy. Data systems when erasing data will just change the energy state, but that will occasionally be enough to make it unfindable again given the type of software systems/hardware tech solutions/rights accesses and so forth and so forth long story. Is there a material damage to the storage medium then of course it is a different story and no deal anyway. When it comes to the heated argument, the funny thing is that the IT service company should never have ended up in that heated argument. Either they can help, or they can't, or partially. One doesn't get into a quarrel with a frustrated unlucky customer under stress. .... Information as in "storage" can't appear unless you have a variety of spin states of particles in specific ways, but remember that the particles are already quantized/localities of energy potentials in space. No matter how we twist it around by words or abstracted maths, there is no such thing as a literally free lunch or any perfect perpetual motion machinery/entity. This is regardless of whether we speak of traditional harddrives (spinning harddisk/electromagnetic storage process by electrical power from the battery or the house outlet) or whether we speak of more modern tech systems such as the "DNA-nano harddrives"+"filling data into organic DNA"(some biochemistry labs) + "quantum computers". At the tiniest scales (subatomic) there is really no point in categorizing charge from mass. But all this doesn't help the poor scientist. What I don't understand is that they keep on saving stuff at only one storage solution or maybe two. Now there are reasons why sometimes this is the only possible in the SHORT run, but there are really no excuses to do it in the longer.
I absolutely love how Sabine weeds out the BS, even at top academic levels, and sticks with evidence-based, measurable physics. She's the perfect antidote to the pop-science crap out there. Keep fighting the good fight, Sabine!
Many thought experiments were proven true later like EPR from 1920s proven at Cern with evidence. So we must evaluate all without bias. Quantum mechanics and Spooky action at a distance was ridiculed initially . שלום
Not so sure. Her angle kinda reminds me some mathematicians who denounce real numbers or even infinite sets. Many theories were developed, made a prediction, clever experiments were devised and physics moved forward.
@@achiltsompanos447 I think you're right about certain theories that are mathematically consistent yet not experimentally confirmed, but could explain things in our world, like String Theory. But aside from that, look at stuff like the obsessions with "multiple worlds" and "bubble universes" in popular science media. These are fundamentally unfalsifiable-- nobody will ever know if they are true or not, and their theories don't even apply to our own universe.
As an experimentalist physicist, thank you! In my group and our collaborating groups, the theorists in these groups propose fun things. Sometimes we find them, sometimes we don't. Sometimes we find things and then the theorists have to figure it out (as an experimentalist, this is my favorite part because I don't know what's happening, but it's largely not my job to). Anyway, at any given time, theorists and experimentalists need to control themselves to be only one step ahead of the other, otherwise we get headlines like "string theorists prove 10 dimensions" or in the other extreme "experiments show neutrinos move faster than the speed of light."
Well since photons aren't ghost particles, but pretty energy-driven... You could of course have some "ghost"particles (but I don't like the expression) that move faster than photons. Here we then automatically come to the difficult question of how or what characterices "baryonism". Btw you say something skeptical/critical there about the ten dimensions of string theory. I agree to that skepticism. If there are tiny strings, well they will of course be vibratory so they will be in the fourth dimension (only). Motion+extension of volume. Greene was just mixing up the most esoteric-mathematical pseudo-physics of the 60s and 70s with particle mechanics. But that doesn't work in the long run, thus he is now discredited of course. That is not to say that string theory if more realistic can't be better than quark models. But if there are such stringpoints, they are not of course vibrating in a set number of dimensions. And they cannot create a reality above the 4th dimension of "motion in space" (that is what 4d simply means, thus it is the only empirically relevant dimension...)
@@TeaParty1776 We could maybe move deeply into plasma cosmological harmonics and all (which has some half-interesting stuff), but let's just say that all of the electric and acoustic guitar strings vibrate only in the fourth dimension. Now, that is very simply because all forms of vibrations = motions of submolecular conditions (atom/particle). If it was a motion variability of energy-wild superstrings or other similar immaterial physicalities, there would be no difference, it would still be in the 4th dimension. There is nada which is not in the 4th dimension.
This reminds me of Linguistic theory. So many assumptions about how the brain handles syntax, word structure, acquisition, etc and so much of it we cannot actually measure. I dont think anything in the field will be completely certain unless neuroscience has major breakthroughs on "reading" how our brains truly construct sentences and words.
Among the many things that made the Professor an excellent teacher was the fact that he wasn't afraid to say 'we don't know.' For the Professor, there was no shame in admitting you didn't have the answer, it was a necessary step toward the truth. It was as important to teach us about the unknown or the unknowable as it was to teach us what had already been safely proven. Yoko Ogawa, The Housekeeper and the Professor
(yawn) Well sometimes one knows, sometimes one doesn't. I don't see your point. That kind of thing is just a speech tradition to start lectures with, or thankfulness speeches during diploma handovers etc.
I’m so glad you reflected on the purpose of your work and found new purpose doing something else. Truly a moment many ancient philosophers would approve of.
Scientists need to pay more heed to philosophy instead of believing in their hubris that there is nothing to learn from the thinkers of the past. There are some things which are beyond the realm off science and which come prior to anything which lets us reach scientific understanding.
I'll be frank with you chief, her view points are very narrow minded and leave little room for actual advancement. Science requires investigations of all possible outcomes, to go down the path of only working on what we know is counterproductive and just silly. If we only stuck with what we knew, then what is the point of Theoretical Physics? What is the point of doing science anyways? If we went by her (and by extension yours) thinking we'd still be banging rocks together in caves. The "BS" you proclaim to be 'fighting the good fight' against is legitimate avenues of research. Thankfully, most scientists are not as close-minded as you lot.
Non-physicist here - but what an outstanding presentation. You put this so well that an interested biologist can understand it! I once went to a conference that brought together mathematicians and experimental physicist to address fundamental neuroscience anomalies (I was there to introduce the experimental field). What was fascinating was the fundamental difference between the neuro-mathematicians and the neuro-physicists. The latter were data-junkies and lapped up any new experimental finding but were suspicious of any conclusion from a tabula-rasa beginning. However, the former (mathematicians) seemed to despise data because it generally undermined the elegant equation constructs that they devised. I suspect that nothing really came out of that meeting that reflected the two fields - but probably a lot came out for the interactions within each one. For me I learned more about my colleagues than my area of expertise!
1:50 What I never understood about the loss of information: How is Quantum Mechanics reversible, when many results are based on probabilities? How does a reversed double slit experiment look like?
Totally legit question. That's what happens when they try to sell you on the Copenhagen (non-)interpretation of quantum mechanics... There are various answers to your question, which basically consist in explaining some alternative interpretations of QM in which the evolution is deterministic: Everett (a.k.a "Many Worlds"), Bohmian mechanics, superdeterminism (which is actually a class of models, but.. ok). Let's take my fav, which is Everett. Now QM is perfectly deterministic, the "probabilities" are just mathematical "weights" attributed to certain components of the state vector of the Universe (even though they are experienced exactly as probabilities by any agent operating as usual), and the reverse of the double slit experiment looks like the state vector of the Universe moving away from an entangled state and becoming closer and closer to the separable state which was the initial state before the "measurement". Also, "measurements" don't really exist: they're just the process of getting entangled with the environment.
It's the evolution without the measurement that is reversible. The Schrödinger equation is a one-to-one map between states at different times; it works forwards and backwards. As I said, the problem with information loss already occurs before you make a measurement. Though trying to argue that the measurement process (whatever that is) resolves the problem is one of the ways people have tried.
I've heard many times that quantum mechanics can be time reversed, but this is the first time that I heard that it can be done, unless there is a measurement. It's those small editions Sabine that make your questions and explanations unique. Thank you for taking the time to make sure to include important details that others may leave out.
That sounds pretty esoteric to me. Time in a strictly scientific sense means only that distances always change between objects (once we measure by defining our chosen reference points), and this is no exceptions to subatomic particles such as bosons or mesons or what have we. All scales are in this sense completely relativistic, there is no spookyness of hidden spacedimensions or virtual flatearther photons without extendedness. Since all particles are always in motion, have spin state variations, collide, are expulsed from bigger, etc., there is no forward or backwards time. (There is only relative time) Someone mentions "uni"verse vs bubbles like a multiverse. Well. How much sense does it make that our solar system is the only reality? How much sense does it make that our galaxy is the only. How much does it make that there is a universe... How do you define space outside of space? Of course there are bubbles. Our is only one of many, and I am pretty sure our is spinning. All other system centers are. At all scales. How do galaxies get their energy? Seems like they must be channelling some form of chargelike conditions
As much as I understand, measurement is just entangling wavefunctions of the particle and the instrument. (At least in ceratin interpretations.) So time reversal still stands.
I don't understand half of what you say and I probably misunderstand the other half but I do enjoy your videos. They are thought provoking and I appreciate you sharing them.
So what this comes down to, as far as I can make out, is that physicists tend to care less about the pursuit of knowledge than about their professional status. One might reasonably assume this a general syndrome pervading all of academia. It certainly ran rampantly amok in music theory journals and dissertations, leeching into classrooms, when I was in graduate school, along, among the faculty, with blatant quid pro quo corruption, plagiarism, and various other pseudo-intellectual (which translates to ANTI-intellectual) evils. Another thing I noticed about graduate school is that it seemed ruthlessly to weed out the brightest at least as efficiently as it weeded out the dimmest.
Arguably that is everywhere, not even just academia. Its just we expect academia to be an exception due to its core principles and its not because of human nature in a narcisstic culture and reward based economy.
@@jorgepeterbarton The difficulty with dismissing this as “human nature” is that the parasites couldn’t survive without hosts. The phonies couldn’t fool anyone without people of intellectual integrity to attempt to uphold the discipline (the discipline of music theory, in the only case for which I have experience). Now you might take the position that eventually the wheat will separate from the chaff, but my sense from my study of the history of music theory is that the rot has particularly set in since around the last several decades of the twentieth-century and that the problem continues to become progressively more acute.
"We want a solution to the Black Hole information loss problem!" "We have many solutions available! Which one would you like?" "Eh? The right one?" "Oh. I am terribly sorry. That information has been lost behind a Pay Wall..."
This is good advice for graduate students looking for a research topic. On the other hand, titles of popular articles about science all tend to overpromise, people know this and still read them for entertainment, skipping a few articles won't really make a difference.
I can't get enough of these videos. You explain everything clearly and practically. You're the perfect teacher for these topics. I appreciate your work, thanks.
Great post my Sabine. I appreciate all the ways you bend and stretch my grey matter. Much love, care and blessings to you and your family. Stay free, happy and healthy ✨️ 😇 🤗 🥰
Lady you are a great speaker . Most of the time I do not understand what you are talking about . but this one I could understand .. Nothing is for sure or absolute ,, if you ask a scientific thinker . None of this will effect my life , what is left of it . I just like to hear you talk and be amazed how smart you are .
Thank you!! This is by far the best video on the (so-called) "black hole information loss paradox" that I have yet encountered. As a mathematician, my "solution" to this seeming paradox is very simple: what's true at the quantum level is not always true at the macroscopic level. For example, if we take the rational numbers, no matter what the decimal expansion is, you can always recover a pair of whole numbers in that ratio. In other words, the information about the pair of whole number is never lost no matter how and in what base you do your expansion. But when things get more complicated (i.e. the Real numbers) you suddenly cannot find a pair of whole numbers whose ratio generates the decimal (or any other base) expansion you are dealing with if that expansion represents an irrational number. If something as simple as the number line generates this sort of scaling problem, I suspect physical reality, which is seriously more complicated than the number line, has similar problems.
But what happens if the real numbers turn out not to be so real after all? Consider Cantor’s diagonal construction, which tries to write down a list of the reals. But every number that you can write down is by definition a computable number. So if you accept Cantor’s construction, then it is proving that the cardinality of the computable numbers is greater than ℵ₀, which we know to be nonsense.
@@lawrencedoliveiro9104 Cantor’s diagonal construction shows that the constructible numbers are less that all the numbers; in other words, there are more Reals than Rationals. His construction basically fails to construct all the numbers - and that's his brilliance - proof by contradiction. Details can be found at en.wikipedia.org/wiki/Cantor's_diagonal_argument
I love the comedic relief you introduced in this video. Keep it up! It's great to have something both funny and informative :D
2 ปีที่แล้ว +1
Sabine rocks!! My personal untrained assumption is that information rest right there at the event horizon, inaccessible and seemingly freeze from our perspective, but falling at light speed towards the singularity from the perspective of an observer at the event horizon
This is such an amazingly simple yet fundamental explanation. Beautiful. I am wondering though, in this context, why Sabine presented Hawking Radiation as a fact; because despite all of its elegance it, too, still bears to be verified experimentally. Using it in your reasoning puts it right there in the realm of assumptions, which Sabine so poignantly presents as a key factor to discerning which matters are worth reasoning about.
Maybe because Hawking radiation has a stronger theoretical footing compared to the solutions of the BHIP. Hawking radiation is provable without any modification to general relativity or quantum mechanics. If GR and QM are accurate and black holes exist, then Hawking radiation is extremely likely to exist too
This is why as much as I find theoretical physicists awesome for their knowledge around "how to deal with the math", I still prefer experimental physics. Just because the maths allows a certain solution it does not mean that this is what is happening in reality.
Experimental physics is all good and shiny. But if we didn't have theoretical physicists, noone would have come up with quantum mechanics and we wouldn't have our lovely transistors that gave us PCs, internet and many other great things.
Dear Sabine, I respect you absolutely, and I can just get glimpses of the things that you discuss. But, as an ordinary person, if headaches are proportional to lack of perception, then I suffer migraine. However I will continue to watch you, and like a dog under the table, pick up whatever crumbs of understanding that I can, that fall my way.
A concise presentation that addresses the problem of knowledge, its limitations, and~how easily specialists can get caught up in possibly fruitless efforts to gain knowledge~and instead settle for a set of beliefs. The problem of knowledge and its limitations also apply to other areas of "speciality", such as psychology, history, economics, etc. Sabine's presentation also applies to how easily specialists get caught/trapped in a dominant way of thinking about a subject that actually blocks furtherance of knowledge in favor of a belief that can also have social consequences when challenged. The instance of Galileo is one case in point; exposing propagandist deceptions and lies by the stature of an authority that maintains them as real knowledge and therefore true, risk serious consequences as well. What happened to the scientific attitude of skepticism?
You can be sure that skepticism and postmodernity are total opposites ! :) Just remember the deliberately excellent hoax of Sokal ! That really showed what has happened with physics (moving away from science and into gibberish)
I heard somewhere that "in the center of every black hole there's a little man with a flashlight searching for a circuit breaker." Maybe he's got all that missing information.
As a person who's only science background comes from these youtube channels... As far as I understand there's a huge paradox here: to fully (or at least much better) understand the universe we should know what's going on inside black holes. But it is impossible because of the very nature of black holes. What's inside is completely "detached" from the other parts of the universe and loses all causal connection with the rest of the universe. It's like you want to enter a locked room but the only key to the room is locked inside.
@@DrTheRichI don’t think it’s similar, because we know black holes exist in the first place. We can’t say the same for god. In the latter case, there’s nothing to interrogate. In the former, we know there *is* something to interrogate, we just don’t have the tools to do so.
@@DrTheRich But that's exactly what I'm saying. In the black hole case, we at least know that black holes exist. We just don't understand what's inside them because we can't observe that. In the god case, we don't have any evidence that god exists at all. So from a first principles standpoint, there's nothing to "discover". I hope that makes more sense.
I do love the fact that Sabine goes out of her way to remind us that the difference between being able to do something in principle vs. being able to do it practically can be a rather vast gulf. Just because you could in principle un-burn a book in mathematical and theoretical terms doesn't mean we are *ever* likely to be able to do so, even with unimaginably more advanced technology than we have today.
What would physics be like without real numbers? You know the things that are in principle claimed to be completed infinite processes - in the same principle that the whole idea of "actual infinities" is not an absurd paradox, but serious mainstream math -... but yet in practice, AFAIK nobody has been so far able to report to have empirically completed an infinite process. PS: Note that any real number in principle contains all information of all universes. All the information is already in the most important tool of contemporary mathematical physics, in the ZFC axioms, and can't ever disappear... unless you stop believing in the axioms of ZFC or some other formulation of axiomatic set theory that in principle postulates a theory of "real numbers".
@@santerisatama5409 Infinities are most likely impossible. Useful mathematically, but not realizable in any real physical context. That being said, it seems likely that reality can quite handily manage ARBITRARILY long or large processes. For example, the statements 'Time has no Limit' and 'Time is Infinite' are not remotely equal. No matter how long our universe were to go on existing and expanding, at no point would it BE infinite. It can approach Infinity all it likes - but it'll never get there, any more than anything else can. It will always be finite and - at least within any given frame of reference - measurable. Real physics (and indeed reality) seems to use Infinity as a non-inclusive boundary condition, never as an extant property. This is fine: [0,+∞) This is not: [0,+∞] Or so it seems for now.
@@Jesse_359 Yes. Gödel's incompleteness theorems are special cases of far more general Undecidability of the Halting problem. Ie. ontologically non-deterministic "sizes" of durations.
I can imagine several decades into the future, bright young physicists/cosmologists will be thinking of areas to research, and the response will be, 'Yeah nah, that idea got Hossenfeldered years ago'.
I love your argument, I think in the same way: if a theory cannot be tested that is quite useless to try to wrap our heads around the problem. It would be more productive if all those great minds would work on something else, something that can actually be tested and proven/disproven.
Okay, it has been and year since this video... the Queen of Physics still holds strong, for Sabine''s strong argument, nobody can beat this......she simply tells it like it is, and I like that because her knowledge, wisdom, and strong personality simply tells it like it is! ❤️
I think finding a solution to the conflict between GR and QM is definitely something to research, but it sounds like the BHIP just doesn't have enough clues to do that. Maybe it can one day be used to choose between several solutions that came out of other areas, but I suspect that's the only way this will be useful. And I strongly suspect _any_ solution to the conflict will depend on some actually verified new physics (i.e. discoveries that don't fit existing theories, thus hinting at what solutions have to do), not just theory (as in, not only solutions but the very BHIP itself is just theory, not observation of any kind).
For me, there is no real proof of the theory that information cannot be destroyed. It itself is an assumption. And I see no real reason why it has to be true. So what if information is lost in a black hole? Why does this create such a problem? And why have they not just adopted the theory that indeed information can be lost? There! I solved the information loss paradox! Simply by saying that information can be lost, and the theory that it cannot be lost is not true. Can anyone prove me wrong?
I agree. This BHIP is inherently a question that places QM in a GR context. Until you have a quantum theory of gravity that can join up to GR, the question seems pointless to me to be asked for all the reasons Sabine says. Fine if you want to go find a black hole and measure stuff in the meantime (I wouldn't suggest getting too close), but without a QM gravitational description, you're trying to mix oil and water and expecting it to come out without problems.
(Physics) Theory >> just music, just stories, just religion, just culture, just free market anarchy, just games, just capitalism, just nationalism, just human laws. Physics theory is about doing the hard work of solving a massive puzzle.
So working on the information paradox is a lot like systematic theology: you can create a logically consistent framework, but it's impossible to prove. It reminds me of an Asimov short story: particle physicists kept discovering smaller and smaller particles. A graduate student proved it was an infinite progression and got his PhD - in theology.
Rubbish. All Sabine said was it is impossible to prove today. Tomorrow someone might figure out a way to make a laboratory black hole and and measure the radiation. They'd better be able to, because any small enough safe lab black hole will evaporate in almost an instant, so they will not be waiting long! Not likely of course, but in her 10,000 years hence maybe. So it is not theology. It's theoretical physics ahead of experimental physics. Happens all the time.
Interesting metaphor by Asimov. I don't pretend to understand the math here, but it seems to me that the "problem" of "information loss" is nothing more than an incorrect assumption surrounding certain mathematical expressions defining black holes. Three questions occur to me. 1) If scientists cannot accurately quantify information, how can they determine how much information (if any) may be lost in a black hole? 2) If information is quantifiable, how can an exact quantity of information be calculated? 3) How can a quantity of intangible (non-physical) information be expressed? Take the book as an example. You can quantify the language information based on the total number of letters written, but this is not the only information present in a book. Most of the information in a book is COMMUNICATION OF IDEAS AND CONCEPTS that are simply REPRESENTED BY THE LANGUAGE. Ideas that are CREATED BY THE AUTHOR embody a great deal more information than just that of language symbols. Seems the concept of 'information loss" is going really deep into the rabbit hole! Exactly how many bits of "information" are present in Einstein's General Relativity Theory? Without quantification, any conclusions regarding "information loss" are not feasible.
Here's my take on it. The idea that quantum mechanics preserves information is incorrect to begin with. Why? Because there is more to quantum physics than just the Schrodinger equation. There is also the measurement which the Schrodinger equation does not describe, and the measurement drops information, because it's a projection. It is an irreversible process. And, guess what, it turns out that the gravitational field causes decoherence of quantum states thus performing the measurement. There are papers about it and even a book by Penrose (Emperor's Mind). The stronger the field, the shorter the lifetime of the quantum state. So quantum state information is lost on approach to the singularity. All quantum states decohere in its vicinity. NOTE: as Sabine pointed out in the past, decoherence is not quite the same as an actual measurement. True. But it's a prelude to it. And the decohered state is no longer described by the wave function. You have to bring the density operator at this stage. The resulting non-unitary quantum mechanics no longer preserves information.
You kind of lost me at the last part. I thought there was just one wave function to rule them all. But I agree that decoherence / measurement is the key to the quantum riddle. I like the idea that every particle interaction results in an entanglement, from the nucleus decay to the alive/dead cat to the scientist opening the box, and if you apply chaos theory you can see that the system is both unpredictable yet reversible. On the other hand, if you add 2 numbers you have no way of knowing which numbers were added, which makes me think information loss is an inherent property of the universe, and why are scientists so bothered by it?
@@user-qw6ht7jw2b No. The density operator formalism goes beyond the wave function and allows for the description of decoherence and mixed states. Wave function states are always pure.
@@zdzislawmeglicki2262 Actually I'd say that it does not go beyond the wavefunction, it rather goes "into it": Decoherence can completely be described using a wavefunction "of the whole system" (measurment apparatus and environment of the physical system in question, ultimately something like the whole korrelated universe I guess) And then the density operator just gives you information on the statistics of sybsystems wihtin this "global" wavefunction. This is done by assuming that the different degrees of freedom of the wavefunction are combined in a certain linear way, and can thus also be "seperated into subsystems" in a certain sense. None of this really goes beyond the wavefunction/Schrödinger equation fomralism: It just analyzes it in a certain more in-depth way! Decoherence then gives, without assuming any global non-unitaryness, exactly the measurment statistics that are observed in experiment (so including the vanishing of interference patterns [i.e. "collapse"]) Also notice that: At first it might seem that we are forced to give a "many worlds" type of interpretation to quantum mechanics if we acknowledge decoherence as solving the paradox as I tried to describe above, but actually this only happens if one interprets the wavefunction as exactly the physical system (I.e. gives "literal" physical meaning to every of its aspects) But certainly we don't have to do that! It still might just be statistics, but in a "setting" (manifold/physical structere or something) that in some way is not how we classically expect physical settings PS: now that I think of it, my last statement would indicate some non-unitary dynamics maybe. Also I wanted to add that I really like Penroses Idea, it just sounds to awesome and yeah, reasonable Have you read The Emperors New Mind? If a considerable amount of it is about this exact topic then I might get it, would be interested in that - his papers I found a bit of a let down.. but maybe my physics experience is still to little to appreciate what he does there :D
@@TheDummbob The idea that you can follow unitarily the entanglement of a target quantum system with an Avogadro number of components in a measuring apparatus is so impractical as to be unreal. What happens with the information spread over the measuring apparatus by such entanglement? Well it just dissipates, contributing to the rise of entropy. Regarding gravitation causing decoherence, I read papers that discussed the matter, but not Penrose's book, so I can't opine on the latter. But I bet that it's very good, like all other writings of his. Here is another idea: how does the universe come into its classical shape? I'd say it does this by entanglement and measurement of itself. Every quantum system entangles with the universe and sooner or later it classicalises, thus coming into being. There is no need to muddy the issue by talking about consciousness. Any sufficiently large system can be a measuring observer.
@@zdzislawmeglicki2262 Yes you are right: Its highly impractical to regard the measurement process/dynamics of "macroskopic" systems as unitary. But I didn't claim that it is paractical, I just claimed that this is not a problem of quantum mechanics as a theory - QM totally allows you to theoretically do that, without going "beyond" the schrödinger equation or introducing some sort of "unitarity breaking" mechanism. It can totally expalin (in principle) all the non-unitary evolutions of measurement processes as happening buried wihin a "global" wavefunction which itself evolves completely unitarily (by means of entanglement and decoherence of subsystems) (Also you say information would just dissipate and thus contribute to the rise in entropy: Well that might be correct, but entropy is a quantity relating to our "knowledge" about a system, it is not a fundamental physical quantity in some other sense: Saying that measurment process increases entropy just says that we cannot track what happens with all of those phases - but it doesn't say that information is lost at a fundamental level, and thus also does not imply fundamentally non-unitary evolution) This basically is similar to what you say at the end of your answer: There is no need to introduce anything about consciousness, its only about interaction and entanglement and the resulting decoherence, and not only don't we need "observers" we actually also don't need to go beyond standart quantum mechanics (only when we try to interpret QM as being a "rough statistical estimate" of underlying processes, which might be correct, atleast I like the Idea)
Amazingly informational video as always! Always very pleasing to hear your explanation, but hearing that thunder sound effect scared me into oblivion haha.
I'm beginning to think Sabine thinks everything is gobbledygook except neutrinos. Her fashion sense is always on point though. Seriously, keep making these videos please. You are essential to the scientific community and to viewers like us who want actual information rather than clickbait drama.
Hi Sabine, you are my favorite science communicator. I have a question about black holes: should I think about a black hole as a region in space where there isn't anymore space (a hole in spacetime itself) or should I think about it like a compact object so massive that an escape velocity for anything close enough to it is impossible even for light? Because if it's the latter (my gut is leaning towards the latter), then why do scientists and/or communicators insist that anything falling onto it is gone? It's not gone, everything that ever fell onto it is still there, albeit unrecognizable. It's just inaccessible to us, but still there. Comments?
This may be a clueless question, but if thermal energy is random, and flame emits thermal energy, wouldn't some of the information in the book inevitably be lost in the burning, even if you had a Maxwell's demon tracking every oxidizing molecule of paper and ink? Would the information loss increase if you added gasoline to the fire and made it hotter? Thanks for the fascinating clip.
I think when they say "random" in this sense they mean disordered. I believe this is a different kind of random than when they say a photon decides to stop being a wave and become a particle. Still leaves more questions than answers, and I unfortunately don't have those answers (yet!)
After burning a book, you can trace every molecule and photon and reconstruct the book. The photons can be traced back to the moment of emission. You adjust the molecule's momentum and vibrations and can keep rewinding. Photons coming from a black hole carry no information about its interior. One clue that may help understand this is, that the photons emitted by a black hole are roughly the size of said black hole. They are created by the event horizon, not by the singularity where the matter is.
Contingent, chaotic not random. But if fundamentally contingent then maybe we can't. But in principle could for the logical case in question that matters to the argument.
I think you are a bit confused with the entropy… Long story short: If you are able to trace every single molecule, every single photon, every single interaction… Than you use more energy doing that(thermodynamically), than the system itself increasing its entropy! So yes, theoretically, you can do that, and extract all the information that book had! Adding gasoline to the system or doing whatever else, still keeps T
@@user-qw6ht7jw2b What you are saying is basically quite comical or a misunderstanding of basic physics. But this seems to be pretty widespread. A photon by its automatic spinstates is always a wave from and on its own. Several photons make up a light ray. The spin details cause the qualities (frequencies and intensity) of the waves. There are no mystical wave forms in space of itself. Once you have a spinning top toy with its leg painted moving along a paper, it will draw a wave. Until it runs out of energy (due to the Earth). In open space it would probably continue longer by spin because the entropy would increase much slower. Now if you close your eyes and miss some of the path of the wavedrawing toy, that doesnt mean that the toy jumped through space randomly. Given particles they move extremely fast. You can not detect their position, although of course any position is fake (since all always moves, see Einstein's 4th dimension). It is easier to adapt our motion or to observe or calculate future paths of the relatively slower (with no mass or almost no mass one moves at or near C, thus becoming more or less unrelativistic)
Wonderful little talk. I didn't understand all of it. btw Penrose says something about this problem - he said that the Schrodinger equation is a description of how the wave evolves over time but then you cannot start it off without measuring something so it doesn't work - even Schrodinger was worried about this aspect. Its in a recent Penrose video with Jordan Peterson I think, I haven't explained it well ....
Thank you for the video! I'm curious why time reversibility is assumed to be a given under such extreme circumstances, given that even a measurement breaks reversibility as far as I understand?
There is no "time reversibility," not really. Time reversal invariance (or the full CPT symmetry) is a symmetry of the _laws_ of physics, not of any particular physical system. The _laws_ of physics are not physical systems. What this means is that if you see a broken egg reassemble you cannot say any law of physics was violated. You can only say someone probably ran the universe backwards for a bit (entropy was lowered) or you got unbelievably lucky.
If you assume the Copenhagen (non-)interpretation, your objection totally makes sense. It is as if physicists insisted on applying unitary Schroedinger dynamics in the most extreme of regimes... but at the same time forgot that they are negating it in much more mundane regimes. --- I just think that Copenhagen should be abandoned, Everett should be embraced, and yes, as Sabine says the black hole information paradox is an actual logical inconsistency between quantum mechanics and General Relativity.
@@Achrononmaster isn't it also possible that a blackhole's Hawking Radiation creates a book by the same logic? On the other hand, the measurement problem says that you cannot restore the full wave function after the measurement. If you invert time for whatever law governs collapse, you end up with a different wave function originating from that point.
Can even the information loss be real from our reference system? Since, from our frame, we cannot actually observe an object pass the event horizon, even in an infinite amount of time?
This is only the case for eternal black holes (which only exist mathematically), not for real black holes which (to our best current knowledge) evaporate. We would see stuff falling into them an disappearing in finite time.
@@SabineHossenfelder thanks! I only have some knowledge of mathematics behind relativity and time dilation effects. I'm gonna go deeper into the subject then, i didn't know the difference between the eternal ones and the realistic model.
@@SabineHossenfelder : How small is that "finite time?" Are you saying objects fall past the event horizon BEFORE the rate of black hole evaporation becomes significant enough to be measurable? If not, would the object's information still outside the event horizon cause the Hawking radiation to be non-random?
I took a mathematical physics class in college several years ago and I remember covering Lagrange functions and matrix groups that described movements of particles. But never have I heard the topic of black holes described so well. Thank you Sabine!
I think you touched on a point that may lead us to a solution Sabina. "The information comes out over billions and billions of years". The information in that book before you throw it in the black hole is encoded over space. When the information from the book comes out of the black hole it is encoded over time. Kind of like a text to speech program does to a book. We just have to figure out what algorithm it uses to encode space into time.
That’s why I never got into working with the information paradox. Instead I focused on more mathematical problems and eventually left academia altogether. Best decision in my life
Would it be solvable with a Quantum Gravitational theory. Say for example someone claimed they had such a theory, should the expectation be that it could be used to calculate what happens. As opposed to theories claiming multiple universes exist, could this be a test for such a theory?
Yes any quantum gravity theory is expected to be able to solve this problem. However, I should clarify that the information paradox goes beyond the simple fact that we don’t have a theory for quantum gravity. Einstein’s equations are expected to be valid for describing black holes. And hawkings theory of Hawking radiation describes how radiation comes from black holes. It is a quantum field theory calculation in a situation where quantum field theory is expected to be valid. And together, these calculations seem to form a paradox. Probably, either quantum field theory as we know it isn’t valid near event horizons, or Einstein’s equations aren’t valid for describing black holes. In theory, one could test their quantum gravity theory by doing measurements on black holes, but the problem persists that we haven’t imagined any way of detecting radiation from black holes.
As Andrew says correctly, quantum gravity is expected to solve the problem. However, since we don't have this theory we can't do the calculation. Hence, physicists try other things.
@@SabineHossenfelder Everyday and every new video you become more attractive to me💯 I am a sapiosexual. More that we realize that objective truths cannot exist because of the fact that we are not Immortal beings and the only way to have addictive truth is to live forever from the beginning of time to the end of time and none of us 3rd dimensional beings have that ability the more that that shines through in your work it really turns me on. You are an amazing human being😍💯🌈🦄
She said "math" but the word "math" she said is acually means a physical theory. She says about theoretical physics vs experiments. I don't know why she dosen't distinguish math and mathematical models of physical systems.
The information loss paradox has me wondering if, perhaps, the only information the universe truly cares to conserve are the properties of mass, angular momentum, and charge. They seem to be the defining qualities of particles, after all 🤔
@Christopher Grant how do you figure? If quantum mechanics says information is conserved, and GR says black holes only have three "hairs," why shouldn't we consider reconciling the two in this way? I'm definitely not married to the idea, but I figure it's worth consideration.
Yeah I mean when trying to reconstruct the burned book, I have a sneaking suspicion that a given smudge of ash probably could have been produced exactly in that state from about 2 billion different combinations of letters. Like simplify it down to a simple line is what remains and then try to determine if that line had once been two separate lines combined or 10B little lines combined or some number in between... How do we really believe that we can infer past state from present state when about a bazillion past states just a tincy bit different from one another could have caused the exact same final state? Hard for me to intuit it anyways.
@@TheSkystrider But I think this is the problem - you assume two initial states CAN produce the exact same resulting state. This should not be possible according to QP. Unless...perhaps..for black holes.
The problem is that if you take two particles and mash them together into a particle with, say, '10' mass and no other properties, you have no way of knowing whether the particles that made it up had masses of 1 & 9, 2 & 8, 5 & 5, and so on. That more complex informational state has been erased irreversibly.
@Alfred Wedmore In the silicon sheet experiment, all the information that described the original complex crystaline structure was release as non-random energy during the course of its melting and reformation - heat energy is highly disordered and entropic, but that's not the same thing as random. If I had carefully recorded the entire process I could (in principle) figure out what its original shape was from the 'waste' energy given off during the process - for example you would see the complex pattern *glowing* as it dissolved, providing a time-lapse record of its form that you could record or remember, and hypothetically reverse. You as a human certainly wouldn't be able to discern its entire atomic makeup this way, you'd need unimaginably sensitive instruments capturing the entire output of the process, but you get the point.
their is something that bothers me every time I hear about this subject . I hope someone can help me understand. There is definitely something wrong with the theory and of mathematicians have no problem putting Infinity everywhere, we have no scientific evidence that Infinity exist in the real world. So question is this: Can the math just be wrong and the center of a blacj hole is not a singularity but just an extremely dense object ? I mean if the mass is big enough to curve space-time enough so the light can't escape, It should look exactly the same from the outside right ?
I can help. General Relativity doesn't actually predict the formation of black holes from an outside observer's perspective, despite permitting the solution. As a shell of matter undergoes gravitational collapse, the gravitational time dilation increases in the space the matter occupies, slowing its collapse. As the collapsing surface of mass/energy approaches the would-be event horizon, the collapse gets slowed more and more. This slowing is severe enough that the collapsing surface of mass/energy never even meets the would-be event horizon, only gets infinitesimally close. This structure is known as a shell collapsar. If you throw more matter into the shell collapsar, it'll plunge the matter below it into a gravitational well, sucking the mass/energy out of it and into itself. The result is the shell collapsar grows, but still doesn't become a black hole. For a shell collapsar, all the mass/energy is concentrated infinitesimally above where the would-be event horizon would form. Shell collapsars look identical to black holes from the outside and have no event horizons nor singularities. So the solution to the black hole information paradox is black holes aren't real so there can't be a paradox.
Thank you so much for taking the time to answer. But again, if the math are wrong. If the plank limit is way smaller than predicted. Couldn't we arrive at a critical mass that would generate an event horizon without the need of a singularity ? Wouldn't this be the simplest answer to the lost information paradox ?
@@MrSpantra The existence of an infinity is generally suspected of being an imperfection of the math, meaning the core singularity of a black hole should still have volume.
and if it does have volume, the black hole paradox doesn't exist because you would gind all the information in the core of the black hole. Hence my question
I love this! There are so many channels talking objectively about the output of science, but not many that talk about the processes and the value, or lack there of, of those ideas. So good to get this insiders view. Especially on physics, cause it one of these areas where non experts like me can’t even begin to accurately judge the relative importance of anything.
Isn't the "simplest" solution to state that falling into a black hole constitutes a measurement process? And if GR breaks at the Cauchy horizon, aren't physicists putting the cart before the horse trying to solve this problem?
I believe there should always be a disclaimer (maybe in a form of a video watermark?) that BHIP results from the incompatibility and incompleteness of two models rather than exists as a physical phenomenon.
No, that's nonsense. GR does not "break" at a Cauchy horizon. Cauchy surfaces were invented by GR! GR does not even "break" at a singularity, all physics surrounding a singularity is well-defined. It is only up extremely close when the singularity might get "fuzzed out" by "quantum noise" (a fantasy term, but physicists have to worry about what it means) that classical GR does not apply. But _non-classical Classical_ GR might apply, that is, GR with non-trivial spacetime topology --- which is possibly the ultimate explanation for quantum mechanics. (Or to coin a new Wheelerism: "quantum mechanics without quantum mechanics.") More people should look into this.
I struggle to believe that if I wrote something on a piece of paper, then rubbed it out, you could observe the rubber flakes or whatnot to discover the information that had been lost. I could throw the paper in a fire. It's all over my head.
I don't understand the paradox. You only end with lost information in the thermal radiation because you have no clue about the process that created it. If you only have light you can't recreate the lightbulb from it, let alone the generator that powered it. The preservation of information demands that you know every aspect involved.
As far as I have understood it Hawking radiation forms when a virtual particle/antiparticle pair is separated at the event horizon. Therefore, it is only dependent on the black hole's mass, angular momentum and electric charge and not on what specifically formed the black hole.
@@theouxepl1222 I don't really get it. You put said book into the black hole. It's mass increases by a book. Now that damn book has to come out of it somehow if the black hole is to evaporate over time. What happens to the book?
@@Unotch I don't know what happens to the book inside the black hole and I'm not sure if physics has an answer to that question as a black hole's inside is immeasurable. But what may help you is the idea, that the book's matter is nowhere to be found in the Hawking radiation. You can not determine whether a given emitted particle originated from the book, not practically but also not in principle. Rather, Hawking radiation happens "on its own" (due to quantum fluctuation creating particle/antiparticle pairs right at the event horizon) and as a consequence in order to conserve energy the black hole must experience negative energy thus lose mass.
@@theouxepl1222 That's ... unsettling. How do you know that it fails at the conservation of information and not the conservation of energy? Because if the radiation has nothing to do with the things inside the BH ... well, SOMEHOW the book that fell in would have to end up as heat radiation or the black hole would not lose mass because the book would still be there. Well, compressed to atom core on atom core but still there. It would have to disappeare by something else doing something somewhere else and then it just goes away particle by particle - and then there STILL must be a certain mechanic behind it all. A black hole losing information is saying that something happens without ANY process behind it which i find frankly absurd ... well, THERE's the paradox.
Another solution could be that black holes do not evaporate at all, due to the fundamental misunderstanding of gravity. Black holes could keep absorbing energy, even if not a single particle falls into it if gravity is spatial in nature. Gravity as an inward spatial flow, absorbing space itself and the energy it contains, countered by an outward spatial flow of energy that falls into a higher state of entropy. We need to give energy integral spatial properties to keep things in balance, so an increase in entropy causes spatial expansion to solve the dark energy mystery as well while we're at it :) Eventualy the entropy in the universe becomes so high that the the inward spatial flow of gravity takes the upper hand, and the universe will start shrinking in size. The amount of (radiation) energy in space will still be magnitudes higher then the hawking radiation and due to the spatial absorbtion even giant black holes can eventually coalesce to form even bigger black holes. The spatial absorbtion will continue till the point where all space-time is absorbed, and there is no more inward spatial flow, and thus no more gravity. And with no more gravity the black hole will become the primordial seed of the next iteration of the universe... Thinking about physics and cosmology without the hindrance of established scientific knowledge is fun :)
Would the paradox be considered solved if someone came up a theory of quantum gravity and proved it though other observations? Even if we aren't able to measure Hawking radiation, if that theory can consistently explain what happens to information that become trapped in black hole then it's as good as solved.
We don’t know if quantum gravity exists and we don’t know if the solution to quantum gravity would have any consequence on the solution of the paradox. So, the solution wouldn’t be considered solved until a change in our current understanding of physics removes the paradox. And to be honest, quantum mechanics allows for superposition. Which means that maybe 2 different solutions that seem like a paradox based on our understanding may not be a paradox at all. Maybe your asking something different. Maybe your asking: If it can’t be directly measured but evidence strongly suggests information isn’t destroyed then is that good enough? Well if it is good enough for a burning a book, I would suspect it is good enough for an evaporating black whole.
As from the external point of view the Schawartzshild horizon takes forever to form and anything falling in (e.g. a 'book') takes forever to get in. Thus no black hole paradox ever occurs. The information is always still there just outside the forming horizon. If it's a big black hole it might even still be 'readable'. If the 'book' is destroyed by the large forces it encounters this is no different than burning it in a fire. I mathimatical black hole might have no hair, but a forming black hole never loses its hair. Even if you start with a preformed black hole that has a horizon it still takes the 'book' forever to fall in.
Hi Sabine. I come from a biochemistry background, a field where many important advances were developed by physicists. I recognize that physicists are really smart people but researching topics like this (black holes) feel like a waste of their time.
It isn't a waste of time: 1. Black Holes DO exist 2. The apparent incongruence of the "inside" and "outside" of a black hole points to the black spots in our understanding of gravity and quantum theory
1. If we have a problem with information loss in black holes, why is there no issue with information loss across the cosmic horizon as the universe expands? 2. Would a record of what fell into a black hole not continue to exist in the position and motion of particles in the surrounding universe as a consequence of its existence outside it?
This type of problem is an example of arguing over how many angels can dance on the head of a pin. Without the possibility of experimental/observational confirmation of a hypothesis, it’s little more than speculation.
I suspect that because we currently can't "see" into a black hole the best we can do is work off a foundation of assumptions and you know what they say about assumptions. The clearest thing to me is that we need new physics to fully understand black holes, it is like guessing what is in a black box we can't open. We can make a lot of guesses based on what we can see and measure from the outside, we can eliminate a great number of things but we still can't know what is inside until we can look. For this reason I understand the drive to keep trying, who knows some really cool new physics might emerge from the research, but I can also understand why some physicists such as yourself walk away from the problem until something new is discovered that gives us that peek inside.
Sabine, please tell your opinion about the following. Firstly, humans body consists mostly of empty space (considering the ranges between electrons and protons/neutrons, etc.). Second, we have good examples when several signals don't interfere each other (e.g. radio). The question is: IF we change internal (particle) frequencies of an object A, then could it be that object B passes through A without any difficulties? For instance, if I want to pass through a wall to get home, and a wall changes its internal frequency - is it possible in principle to pass through it? That would be very convenient... Thank you.
To get a handle on the black hole information loss paradox (if it really is a paradox), I suspect that we would either need to find a black hole that is small enough to have measurable Hawking Radiation OR prove that a black hole that small cannot exist (as in anything below a certain mass, potentially up in the lower stellar range, quits being a black hole).
Excellent commentary! This video prompted me to purchase your book "Lost In Math". I have been suspicious for many years that the the beauty of math can lead smart people to erroneous conclusions. Your views are a balm, yet we still need mathematicians and physicists to place themselves on "The Foreskin Of Science" to discover Nature's secrets.
the great thing about explaining zero is you can't be challenged about your explanations if you use the right words and the right syntax and remove the boogie man correctly
A physicist once accidentally reformatted a SSD containing the only copy of a paper she had been working on for 6 months. She then got into a heated argument with a data recovery company over whether or not it's possible to destroy information.
She should have talked to a data reconstruction company, then. And kept all emissions from the formatting on hand to aid with the process.
It's just 1s and 0s
LOL
How much information it was, measured in kilogram ?
Energy can't literally disappear, but whether "information" can depends on just what we define as information, as this is not necessarily the same definition as energy. Data systems when erasing data will just change the energy state, but that will occasionally be enough to make it unfindable again given the type of software systems/hardware tech solutions/rights accesses and so forth and so forth long story. Is there a material damage to the storage medium then of course it is a different story and no deal anyway.
When it comes to the heated argument, the funny thing is that the IT service company should never have ended up in that heated argument. Either they can help, or they can't, or partially. One doesn't get into a quarrel with a frustrated unlucky customer under stress. ....
Information as in "storage" can't appear unless you have a variety of spin states of particles in specific ways, but remember that the particles are already quantized/localities of energy potentials in space.
No matter how we twist it around by words or abstracted maths, there is no such thing as a literally free lunch or any perfect perpetual motion machinery/entity. This is regardless of whether we speak of traditional harddrives (spinning harddisk/electromagnetic storage process by electrical power from the battery or the house outlet) or whether we speak of more modern tech systems such as the "DNA-nano harddrives"+"filling data into organic DNA"(some biochemistry labs) + "quantum computers".
At the tiniest scales (subatomic) there is really no point in categorizing charge from mass. But all this doesn't help the poor scientist. What I don't understand is that they keep on saving stuff at only one storage solution or maybe two. Now there are reasons why sometimes this is the only possible in the SHORT run, but there are really no excuses to do it in the longer.
I absolutely love how Sabine weeds out the BS, even at top academic levels, and sticks with evidence-based, measurable physics. She's the perfect antidote to the pop-science crap out there. Keep fighting the good fight, Sabine!
Many thought experiments were proven true later like EPR from 1920s proven at Cern with evidence.
So we must evaluate all without bias. Quantum mechanics and
Spooky action at a distance was ridiculed initially .
שלום
Hello Geoffrey!! Why am I an idiot? I dont understand a single thing?
Not so sure. Her angle kinda reminds me some mathematicians who denounce real numbers or even infinite sets. Many theories were developed, made a prediction, clever experiments were devised and physics moved forward.
@@achiltsompanos447 I think you're right about certain theories that are mathematically consistent yet not experimentally confirmed, but could explain things in our world, like String Theory. But aside from that, look at stuff like the obsessions with "multiple worlds" and "bubble universes" in popular science media. These are fundamentally unfalsifiable-- nobody will ever know if they are true or not, and their theories don't even apply to our own universe.
@@achiltsompanos447 All ideas need be examined ... Quantum was initially mocked as quackery..
As an experimentalist physicist, thank you! In my group and our collaborating groups, the theorists in these groups propose fun things. Sometimes we find them, sometimes we don't. Sometimes we find things and then the theorists have to figure it out (as an experimentalist, this is my favorite part because I don't know what's happening, but it's largely not my job to). Anyway, at any given time, theorists and experimentalists need to control themselves to be only one step ahead of the other, otherwise we get headlines like "string theorists prove 10 dimensions" or in the other extreme "experiments show neutrinos move faster than the speed of light."
They do move faster than light you're behind the times :-)
Well since photons aren't ghost particles, but pretty energy-driven... You could of course have some "ghost"particles (but I don't like the expression) that move faster than photons. Here we then automatically come to the difficult question of how or what characterices "baryonism". Btw you say something skeptical/critical there about the ten dimensions of string theory. I agree to that skepticism. If there are tiny strings, well they will of course be vibratory so they will be in the fourth dimension (only). Motion+extension of volume. Greene was just mixing up the most esoteric-mathematical pseudo-physics of the 60s and 70s with particle mechanics. But that doesn't work in the long run, thus he is now discredited of course. That is not to say that string theory if more realistic can't be better than quark models. But if there are such stringpoints, they are not of course vibrating in a set number of dimensions. And they cannot create a reality above the 4th dimension of "motion in space" (that is what 4d simply means, thus it is the only empirically relevant dimension...)
neutrinos do move faster than c, but only close to deadlines :D
@@KibyNykraft If the universe was a Telecaster, how many strings would it have?
@@TeaParty1776 We could maybe move deeply into plasma cosmological harmonics and all (which has some half-interesting stuff), but let's just say that all of the electric and acoustic guitar strings vibrate only in the fourth dimension. Now, that is very simply because all forms of vibrations = motions of submolecular conditions (atom/particle). If it was a motion variability of energy-wild superstrings or other similar immaterial physicalities, there would be no difference, it would still be in the 4th dimension. There is nada which is not in the 4th dimension.
This reminds me of Linguistic theory. So many assumptions about how the brain handles syntax, word structure, acquisition, etc and so much of it we cannot actually measure. I dont think anything in the field will be completely certain unless neuroscience has major breakthroughs on "reading" how our brains truly construct sentences and words.
Among the many things that made the Professor an excellent teacher was the fact that he wasn't afraid to say 'we don't know.' For the Professor, there was no shame in admitting you didn't have the answer, it was a necessary step toward the truth. It was as important to teach us about the unknown or the unknowable as it was to teach us what had already been safely proven.
Yoko Ogawa, The Housekeeper and the Professor
(yawn) Well sometimes one knows, sometimes one doesn't. I don't see your point. That kind of thing is just a speech tradition to start lectures with, or thankfulness speeches during diploma handovers etc.
I always find your videos very refreshing and not at all hyped up as some other channels on YT. Thank you for the sanity check !
I’m so glad you reflected on the purpose of your work and found new purpose doing something else. Truly a moment many ancient philosophers would approve of.
seemed to me Sabine just doesn't like wasting time.
Scientists need to pay more heed to philosophy instead of believing in their hubris that there is nothing to learn from the thinkers of the past. There are some things which are beyond the realm off science and which come prior to anything which lets us reach scientific understanding.
I'll be frank with you chief, her view points are very narrow minded and leave little room for actual advancement. Science requires investigations of all possible outcomes, to go down the path of only working on what we know is counterproductive and just silly. If we only stuck with what we knew, then what is the point of Theoretical Physics? What is the point of doing science anyways? If we went by her (and by extension yours) thinking we'd still be banging rocks together in caves. The "BS" you proclaim to be 'fighting the good fight' against is legitimate avenues of research.
Thankfully, most scientists are not as close-minded as you lot.
Non-physicist here - but what an outstanding presentation. You put this so well that an interested biologist can understand it! I once went to a conference that brought together mathematicians and experimental physicist to address fundamental neuroscience anomalies (I was there to introduce the experimental field). What was fascinating was the fundamental difference between the neuro-mathematicians and the neuro-physicists. The latter were data-junkies and lapped up any new experimental finding but were suspicious of any conclusion from a tabula-rasa beginning. However, the former (mathematicians) seemed to despise data because it generally undermined the elegant equation constructs that they devised. I suspect that nothing really came out of that meeting that reflected the two fields - but probably a lot came out for the interactions within each one. For me I learned more about my colleagues than my area of expertise!
1:50 What I never understood about the loss of information: How is Quantum Mechanics reversible, when many results are based on probabilities?
How does a reversed double slit experiment look like?
Totally legit question. That's what happens when they try to sell you on the Copenhagen (non-)interpretation of quantum mechanics...
There are various answers to your question, which basically consist in explaining some alternative interpretations of QM in which the evolution is deterministic: Everett (a.k.a "Many Worlds"), Bohmian mechanics, superdeterminism (which is actually a class of models, but.. ok).
Let's take my fav, which is Everett. Now QM is perfectly deterministic, the "probabilities" are just mathematical "weights" attributed to certain components of the state vector of the Universe (even though they are experienced exactly as probabilities by any agent operating as usual), and the reverse of the double slit experiment looks like the state vector of the Universe moving away from an entangled state and becoming closer and closer to the separable state which was the initial state before the "measurement". Also, "measurements" don't really exist: they're just the process of getting entangled with the environment.
It's the evolution without the measurement that is reversible. The Schrödinger equation is a one-to-one map between states at different times; it works forwards and backwards. As I said, the problem with information loss already occurs before you make a measurement. Though trying to argue that the measurement process (whatever that is) resolves the problem is one of the ways people have tried.
I second this. How does a theory whose foundation is objective randomness get off saying information cannot be lost?
@@SabineHossenfelder How did we define measurement again? Any interaction between two chains of cause and effect would seem like a measurement.
@@JCAtkeson3 Well, that's the problem. Measurement isn't properly defined.
I've heard many times that quantum mechanics can be time reversed, but this is the first time that I heard that it can be done, unless there is a measurement. It's those small editions Sabine that make your questions and explanations unique. Thank you for taking the time to make sure to include important details that others may leave out.
That sounds pretty esoteric to me. Time in a strictly scientific sense means only that distances always change between objects (once we measure by defining our chosen reference points), and this is no exceptions to subatomic particles such as bosons or mesons or what have we. All scales are in this sense completely relativistic, there is no spookyness of hidden spacedimensions or virtual flatearther photons without extendedness. Since all particles are always in motion, have spin state variations, collide, are expulsed from bigger, etc., there is no forward or backwards time. (There is only relative time) Someone mentions "uni"verse vs bubbles like a multiverse. Well. How much sense does it make that our solar system is the only reality? How much sense does it make that our galaxy is the only. How much does it make that there is a universe... How do you define space outside of space? Of course there are bubbles. Our is only one of many, and I am pretty sure our is spinning. All other system centers are. At all scales. How do galaxies get their energy? Seems like they must be channelling some form of chargelike conditions
As much as I understand, measurement is just entangling wavefunctions of the particle and the instrument. (At least in ceratin interpretations.) So time reversal still stands.
These are some of the best videos on this site
It's good you still regard youtube as a site
@@goyonman9655wdym by that?
Certainly, I've gotten a lot of information out of black holes by listening to this video. Thank you, Sabine.
I don't understand half of what you say and I probably misunderstand the other half but I do enjoy your videos. They are thought provoking and I appreciate you sharing them.
So what this comes down to, as far as I can make out, is that physicists tend to care less about the pursuit of knowledge than about their professional status. One might reasonably assume this a general syndrome pervading all of academia. It certainly ran rampantly amok in music theory journals and dissertations, leeching into classrooms, when I was in graduate school, along, among the faculty, with blatant quid pro quo corruption, plagiarism, and various other pseudo-intellectual (which translates to ANTI-intellectual) evils. Another thing I noticed about graduate school is that it seemed ruthlessly to weed out the brightest at least as efficiently as it weeded out the dimmest.
Arguably that is everywhere, not even just academia. Its just we expect academia to be an exception due to its core principles and its not because of human nature in a narcisstic culture and reward based economy.
@@jorgepeterbarton The difficulty with dismissing this as “human nature” is that the parasites couldn’t survive without hosts. The phonies couldn’t fool anyone without people of intellectual integrity to attempt to uphold the discipline (the discipline of music theory, in the only case for which I have experience). Now you might take the position that eventually the wheat will separate from the chaff, but my sense from my study of the history of music theory is that the rot has particularly set in since around the last several decades of the twentieth-century and that the problem continues to become progressively more acute.
"We want a solution to the Black Hole information loss problem!"
"We have many solutions available! Which one would you like?"
"Eh? The right one?"
"Oh. I am terribly sorry. That information has been lost behind a Pay Wall..."
🤣🤣
Pay walls. The event horizons of the Internet.
The science industry in a nutshell
@@ccsleepy8342 No then we are into politics. Science just means "a method to determine reality". In fact. :)
This is good advice for graduate students looking for a research topic. On the other hand, titles of popular articles about science all tend to overpromise, people know this and still read them for entertainment, skipping a few articles won't really make a difference.
I've never seen someone as cheerful, thoughtful, analytical, and scathingly direct as Sabine. Brilliant video!
let's not forget the girl is a hottie, too!
@@warehousejo007 I couldn't possibly comment on her appearance. I'll leave that to those who can see.
I can't get enough of these videos. You explain everything clearly and practically. You're the perfect teacher for these topics. I appreciate your work, thanks.
Great post my Sabine. I appreciate all the ways you bend and stretch my grey matter. Much love, care and blessings to you and your family. Stay free, happy and healthy ✨️ 😇 🤗 🥰
Lady you are a great speaker . Most of the time I do not understand what you are talking about . but this one I could understand .. Nothing is for sure or absolute ,, if you ask a scientific thinker . None of this will effect my life , what is left of it . I just like to hear you talk and be amazed how smart you are .
Thank you!! This is by far the best video on the (so-called) "black hole information loss paradox" that I have yet encountered. As a mathematician, my "solution" to this seeming paradox is very simple: what's true at the quantum level is not always true at the macroscopic level. For example, if we take the rational numbers, no matter what the decimal expansion is, you can always recover a pair of whole numbers in that ratio. In other words, the information about the pair of whole number is never lost no matter how and in what base you do your expansion. But when things get more complicated (i.e. the Real numbers) you suddenly cannot find a pair of whole numbers whose ratio generates the decimal (or any other base) expansion you are dealing with if that expansion represents an irrational number. If something as simple as the number line generates this sort of scaling problem, I suspect physical reality, which is seriously more complicated than the number line, has similar problems.
Nice!
But what happens if the real numbers turn out not to be so real after all?
Consider Cantor’s diagonal construction, which tries to write down a list of the reals. But every number that you can write down is by definition a computable number. So if you accept Cantor’s construction, then it is proving that the cardinality of the computable numbers is greater than ℵ₀, which we know to be nonsense.
@@lawrencedoliveiro9104 Cantor’s diagonal construction shows that the constructible numbers are less that all the numbers; in other words, there are more Reals than Rationals. His construction basically fails to construct all the numbers - and that's his brilliance - proof by contradiction. Details can be found at en.wikipedia.org/wiki/Cantor's_diagonal_argument
@@leighnbrasington Yes, but Cantor’s construction itself is only producing computable numbers.
I can't tell the difference for Sabine to be super excited or to be super calm.
I love the comedic relief you introduced in this video. Keep it up! It's great to have something both funny and informative :D
Sabine rocks!!
My personal untrained assumption is that information rest right there at the event horizon, inaccessible and seemingly freeze from our perspective, but falling at light speed towards the singularity from the perspective of an observer at the event horizon
This is such an amazingly simple yet fundamental explanation. Beautiful. I am wondering though, in this context, why Sabine presented Hawking Radiation as a fact; because despite all of its elegance it, too, still bears to be verified experimentally. Using it in your reasoning puts it right there in the realm of assumptions, which Sabine so poignantly presents as a key factor to discerning which matters are worth reasoning about.
Maybe because Hawking radiation has a stronger theoretical footing compared to the solutions of the BHIP. Hawking radiation is provable without any modification to general relativity or quantum mechanics. If GR and QM are accurate and black holes exist, then Hawking radiation is extremely likely to exist too
Excellent, Sabine
This is why as much as I find theoretical physicists awesome for their knowledge around "how to deal with the math", I still prefer experimental physics. Just because the maths allows a certain solution it does not mean that this is what is happening in reality.
Nailed it Friedrich Herschel.
The way I say it about QM now is "Probability of reality is not reality".
But those theoretical folks do come up with a lot of things for the experimentalists to start poking at.
@@lordgarion514 one hand washes the other.
Experimental physics is all good and shiny. But if we didn't have theoretical physicists, noone would have come up with quantum mechanics and we wouldn't have our lovely transistors that gave us PCs, internet and many other great things.
Dear Sabine, I respect you absolutely, and I can just get glimpses of the things that you discuss. But, as an ordinary person, if headaches are proportional to lack of perception, then I suffer migraine. However I will continue to watch you, and like a dog under the table, pick up whatever crumbs of understanding that I can, that fall my way.
Throwing a book into a blackhole is what we call lossy compression
One may always set their backup target to /dev/null. As a benefit, write speed is limited only by reading speed.
@@AlexanderGieg So you're saying that /dev/null is a black hole? In that case we can study it. Every unix/linux system has one.
Simple solution to that problem: nothing ever crossed the even horizon, so nothing ever was lost. The information is still on its way in.
A concise presentation that addresses the problem of knowledge, its limitations, and~how easily specialists can get caught up in possibly fruitless efforts to gain knowledge~and instead settle for a set of beliefs.
The problem of knowledge and its limitations also apply to other areas of "speciality", such as psychology, history, economics, etc. Sabine's presentation also applies to how easily specialists get caught/trapped in a dominant way of thinking about a subject that actually blocks furtherance of knowledge in favor of a belief that can also have social consequences when challenged. The instance of Galileo is one case in point; exposing propagandist deceptions and lies by the stature of an authority that maintains them as real knowledge and therefore true, risk serious consequences as well.
What happened to the scientific attitude of skepticism?
You can be sure that skepticism and postmodernity are total opposites ! :) Just remember the deliberately excellent hoax of Sokal ! That really showed what has happened with physics (moving away from science and into gibberish)
I heard somewhere that "in the center of every black hole there's a little man with a flashlight searching for a circuit breaker."
Maybe he's got all that missing information.
As a person who's only science background comes from these youtube channels... As far as I understand there's a huge paradox here: to fully (or at least much better) understand the universe we should know what's going on inside black holes. But it is impossible because of the very nature of black holes. What's inside is completely "detached" from the other parts of the universe and loses all causal connection with the rest of the universe. It's like you want to enter a locked room but the only key to the room is locked inside.
It's really quite similar to trying to proof if an extra demensional God exists that created the entire universe...
@@DrTheRich yep, also like making sense of non-existence in terms of existence
@@DrTheRichI don’t think it’s similar, because we know black holes exist in the first place. We can’t say the same for god. In the latter case, there’s nothing to interrogate. In the former, we know there *is* something to interrogate, we just don’t have the tools to do so.
@@kuribojim3916 tell me how you know that there is something behind the event horizon? you can only speculate.
@@DrTheRich But that's exactly what I'm saying.
In the black hole case, we at least know that black holes exist. We just don't understand what's inside them because we can't observe that.
In the god case, we don't have any evidence that god exists at all. So from a first principles standpoint, there's nothing to "discover".
I hope that makes more sense.
how i learned to not worry about the blackhole information paradox
and focus on growing vegetables in my garden
I do love the fact that Sabine goes out of her way to remind us that the difference between being able to do something in principle vs. being able to do it practically can be a rather vast gulf. Just because you could in principle un-burn a book in mathematical and theoretical terms doesn't mean we are *ever* likely to be able to do so, even with unimaginably more advanced technology than we have today.
What would physics be like without real numbers? You know the things that are in principle claimed to be completed infinite processes - in the same principle that the whole idea of "actual infinities" is not an absurd paradox, but serious mainstream math -... but yet in practice, AFAIK nobody has been so far able to report to have empirically completed an infinite process.
PS: Note that any real number in principle contains all information of all universes. All the information is already in the most important tool of contemporary mathematical physics, in the ZFC axioms, and can't ever disappear... unless you stop believing in the axioms of ZFC or some other formulation of axiomatic set theory that in principle postulates a theory of "real numbers".
@@santerisatama5409 Infinities are most likely impossible. Useful mathematically, but not realizable in any real physical context. That being said, it seems likely that reality can quite handily manage ARBITRARILY long or large processes. For example, the statements 'Time has no Limit' and 'Time is Infinite' are not remotely equal.
No matter how long our universe were to go on existing and expanding, at no point would it BE infinite. It can approach Infinity all it likes - but it'll never get there, any more than anything else can. It will always be finite and - at least within any given frame of reference - measurable.
Real physics (and indeed reality) seems to use Infinity as a non-inclusive boundary condition, never as an extant property.
This is fine: [0,+∞)
This is not: [0,+∞]
Or so it seems for now.
@@Jesse_359 Yes. Gödel's incompleteness theorems are special cases of far more general Undecidability of the Halting problem. Ie. ontologically non-deterministic "sizes" of durations.
This is a very no-nonsense TH-cam channel and I'm subscribing.
I can imagine several decades into the future, bright young physicists/cosmologists will be thinking of areas to research, and the response will be, 'Yeah nah, that idea got Hossenfeldered years ago'.
Going to UCB for physics/math major next year. Not saying I’m bright but she’s sure had an impact on me.
You might say it jumped the quantum.
😂😂
Yep, at the moment all we've got is that sh**ty "debunked" going on..Hossenfeldered sounds much more natural.👍👍
😀 yeah nah? You must be Australian
@@XEinstein I am. :)
I love your argument, I think in the same way: if a theory cannot be tested that is quite useless to try to wrap our heads around the problem. It would be more productive if all those great minds would work on something else, something that can actually be tested and proven/disproven.
I really liked this one!
I think much of the physics topics covered by pop sci journalism suffer from this same problem.
Okay, it has been and year since this video... the Queen of Physics still holds strong, for Sabine''s strong argument, nobody can beat this......she simply tells it like it is, and I like that because her knowledge, wisdom, and strong personality simply tells it like it is! ❤️
I think finding a solution to the conflict between GR and QM is definitely something to research, but it sounds like the BHIP just doesn't have enough clues to do that. Maybe it can one day be used to choose between several solutions that came out of other areas, but I suspect that's the only way this will be useful. And I strongly suspect _any_ solution to the conflict will depend on some actually verified new physics (i.e. discoveries that don't fit existing theories, thus hinting at what solutions have to do), not just theory (as in, not only solutions but the very BHIP itself is just theory, not observation of any kind).
For me, there is no real proof of the theory that information cannot be destroyed. It itself is an assumption. And I see no real reason why it has to be true. So what if information is lost in a black hole? Why does this create such a problem? And why have they not just adopted the theory that indeed information can be lost? There! I solved the information loss paradox! Simply by saying that information can be lost, and the theory that it cannot be lost is not true. Can anyone prove me wrong?
First define "information" sounds like the question was asked by a creatard!
I agree. This BHIP is inherently a question that places QM in a GR context. Until you have a quantum theory of gravity that can join up to GR, the question seems pointless to me to be asked for all the reasons Sabine says. Fine if you want to go find a black hole and measure stuff in the meantime (I wouldn't suggest getting too close), but without a QM gravitational description, you're trying to mix oil and water and expecting it to come out without problems.
@@FB-no4lr Yum, creamy italian dressing
(Physics) Theory >> just music, just stories, just religion, just culture, just free market anarchy, just games, just capitalism, just nationalism, just human laws. Physics theory is about doing the hard work of solving a massive puzzle.
Such a great video, Sabine. You have the best channel on all over youtube
"Physicists shall not live on math alone, but on every data point that proceeds from the results of experimentation."
Listening to Sabine is addicting. Love this "no BS" lady.
So you just didn't notice that she is totally bullshitting you. ;-)
So working on the information paradox is a lot like systematic theology: you can create a logically consistent framework, but it's impossible to prove.
It reminds me of an Asimov short story: particle physicists kept discovering smaller and smaller particles. A graduate student proved it was an infinite progression and got his PhD - in theology.
Rubbish. All Sabine said was it is impossible to prove today. Tomorrow someone might figure out a way to make a laboratory black hole and and measure the radiation. They'd better be able to, because any small enough safe lab black hole will evaporate in almost an instant, so they will not be waiting long! Not likely of course, but in her 10,000 years hence maybe. So it is not theology. It's theoretical physics ahead of experimental physics. Happens all the time.
Maybe it's impossible to think outside the box when all your tools are inside.
A linux crusader?
No god excuse is internally consistent!
Interesting metaphor by Asimov. I don't pretend to understand the math here, but it seems to me that the "problem" of "information loss" is nothing more than an incorrect assumption surrounding certain mathematical expressions defining black holes.
Three questions occur to me. 1) If scientists cannot accurately quantify information, how can they determine how much information (if any) may be lost in a black hole? 2) If information is quantifiable, how can an exact quantity of information be calculated? 3) How can a quantity of intangible (non-physical) information be expressed?
Take the book as an example. You can quantify the language information based on the total number of letters written, but this is not the only information present in a book. Most of the information in a book is COMMUNICATION OF IDEAS AND CONCEPTS that are simply REPRESENTED BY THE LANGUAGE. Ideas that are CREATED BY THE AUTHOR embody a great deal more information than just that of language symbols.
Seems the concept of 'information loss" is going really deep into the rabbit hole! Exactly how many bits of "information" are present in Einstein's General Relativity Theory? Without quantification, any conclusions regarding "information loss" are not feasible.
"because they'd have to stop writing papers on it" lol. Thankyou for being down to earth.
"For me, the real paradox is why they keep doing it."
It's so much fun listening to Sabine mercilessly hammering at academia
Why do you like to listen to a sore loser? ;-)
Here's my take on it. The idea that quantum mechanics preserves information is incorrect to begin with. Why? Because there is more to quantum physics than just the Schrodinger equation. There is also the measurement which the Schrodinger equation does not describe, and the measurement drops information, because it's a projection. It is an irreversible process. And, guess what, it turns out that the gravitational field causes decoherence of quantum states thus performing the measurement. There are papers about it and even a book by Penrose (Emperor's Mind). The stronger the field, the shorter the lifetime of the quantum state. So quantum state information is lost on approach to the singularity. All quantum states decohere in its vicinity.
NOTE: as Sabine pointed out in the past, decoherence is not quite the same as an actual measurement. True. But it's a prelude to it. And the decohered state is no longer described by the wave function. You have to bring the density operator at this stage. The resulting non-unitary quantum mechanics no longer preserves information.
You kind of lost me at the last part. I thought there was just one wave function to rule them all. But I agree that decoherence / measurement is the key to the quantum riddle. I like the idea that every particle interaction results in an entanglement, from the nucleus decay to the alive/dead cat to the scientist opening the box, and if you apply chaos theory you can see that the system is both unpredictable yet reversible. On the other hand, if you add 2 numbers you have no way of knowing which numbers were added, which makes me think information loss is an inherent property of the universe, and why are scientists so bothered by it?
@@user-qw6ht7jw2b No. The density operator formalism goes beyond the wave function and allows for the description of decoherence and mixed states. Wave function states are always pure.
@@zdzislawmeglicki2262 Actually I'd say that it does not go beyond the wavefunction, it rather goes "into it":
Decoherence can completely be described using a wavefunction "of the whole system" (measurment apparatus and environment of the physical system in question, ultimately something like the whole korrelated universe I guess)
And then the density operator just gives you information on the statistics of sybsystems wihtin this "global" wavefunction.
This is done by assuming that the different degrees of freedom of the wavefunction are combined in a certain linear way, and can thus also be "seperated into subsystems" in a certain sense.
None of this really goes beyond the wavefunction/Schrödinger equation fomralism: It just analyzes it in a certain more in-depth way!
Decoherence then gives, without assuming any global non-unitaryness, exactly the measurment statistics that are observed in experiment (so including the vanishing of interference patterns [i.e. "collapse"])
Also notice that:
At first it might seem that we are forced to give a "many worlds" type of interpretation to quantum mechanics if we acknowledge decoherence as solving the paradox as I tried to describe above, but actually this only happens if one interprets the wavefunction as exactly the physical system (I.e. gives "literal" physical meaning to every of its aspects)
But certainly we don't have to do that!
It still might just be statistics, but in a "setting" (manifold/physical structere or something) that in some way is not how we classically expect physical settings
PS: now that I think of it, my last statement would indicate some non-unitary dynamics maybe.
Also I wanted to add that I really like Penroses Idea, it just sounds to awesome and yeah, reasonable
Have you read The Emperors New Mind?
If a considerable amount of it is about this exact topic then I might get it, would be interested in that - his papers I found a bit of a let down.. but maybe my physics experience is still to little to appreciate what he does there :D
@@TheDummbob The idea that you can follow unitarily the entanglement of a target quantum system with an Avogadro number of components in a measuring apparatus is so impractical as to be unreal. What happens with the information spread over the measuring apparatus by such entanglement? Well it just dissipates, contributing to the rise of entropy.
Regarding gravitation causing decoherence, I read papers that discussed the matter, but not Penrose's book, so I can't opine on the latter. But I bet that it's very good, like all other writings of his.
Here is another idea: how does the universe come into its classical shape? I'd say it does this by entanglement and measurement of itself. Every quantum system entangles with the universe and sooner or later it classicalises, thus coming into being. There is no need to muddy the issue by talking about consciousness. Any sufficiently large system can be a measuring observer.
@@zdzislawmeglicki2262 Yes you are right: Its highly impractical to regard the measurement process/dynamics of "macroskopic" systems as unitary.
But I didn't claim that it is paractical, I just claimed that this is not a problem of quantum mechanics as a theory - QM totally allows you to theoretically do that, without going "beyond" the schrödinger equation or introducing some sort of "unitarity breaking" mechanism.
It can totally expalin (in principle) all the non-unitary evolutions of measurement processes as happening buried wihin a "global" wavefunction which itself evolves completely unitarily
(by means of entanglement and decoherence of subsystems)
(Also you say information would just dissipate and thus contribute to the rise in entropy: Well that might be correct, but entropy is a quantity relating to our "knowledge" about a system, it is not a fundamental physical quantity in some other sense: Saying that measurment process increases entropy just says that we cannot track what happens with all of those phases - but it doesn't say that information is lost at a fundamental level, and thus also does not imply fundamentally non-unitary evolution)
This basically is similar to what you say at the end of your answer: There is no need to introduce anything about consciousness, its only about interaction and entanglement and the resulting decoherence, and not only don't we need "observers" we actually also don't need to go beyond standart quantum mechanics
(only when we try to interpret QM as being a "rough statistical estimate" of underlying processes, which might be correct, atleast I like the Idea)
Amazingly informational video as always! Always very pleasing to hear your explanation, but hearing that thunder sound effect scared me into oblivion haha.
Sabine, thank you for the honesty and your ability to communicate very well.
I'm beginning to think Sabine thinks everything is gobbledygook except neutrinos. Her fashion sense is always on point though. Seriously, keep making these videos please. You are essential to the scientific community and to viewers like us who want actual information rather than clickbait drama.
Sabine: That's right, this guy again
*shakes fist at the ceiling
EEEEEEEIIIINNSTEEEEEEEIN!
I will never get enough of you saying "Yes, that guy again".
Thank you. As always, your incisive logic clarifies the issue.
I love the way she thinks. She presents the science in the best way.
Hi Sabine, you are my favorite science communicator. I have a question about black holes: should I think about a black hole as a region in space where there isn't anymore space (a hole in spacetime itself) or should I think about it like a compact object so massive that an escape velocity for anything close enough to it is impossible even for light?
Because if it's the latter (my gut is leaning towards the latter), then why do scientists and/or communicators insist that anything falling onto it is gone? It's not gone, everything that ever fell onto it is still there, albeit unrecognizable. It's just inaccessible to us, but still there. Comments?
She addresses this starting around 4:16
We should call this the “Black Hole Information Loss Paradox Paradox.” Well spoken and well done !
Very clear explanation. I was always been a fan of emergent/induced gravity, although I don't know if it can help to solve the paradox.
Yes, that guy again!
Great stuff. I love your work. Thanks for educating us.
This may be a clueless question, but if thermal energy is random, and flame emits thermal energy, wouldn't some of the information in the book inevitably be lost in the burning, even if you had a Maxwell's demon tracking every oxidizing molecule of paper and ink? Would the information loss increase if you added gasoline to the fire and made it hotter? Thanks for the fascinating clip.
I think when they say "random" in this sense they mean disordered. I believe this is a different kind of random than when they say a photon decides to stop being a wave and become a particle. Still leaves more questions than answers, and I unfortunately don't have those answers (yet!)
After burning a book, you can trace every molecule and photon and reconstruct the book. The photons can be traced back to the moment of emission. You adjust the molecule's momentum and vibrations and can keep rewinding.
Photons coming from a black hole carry no information about its interior. One clue that may help understand this is, that the photons emitted by a black hole are roughly the size of said black hole. They are created by the event horizon, not by the singularity where the matter is.
Contingent, chaotic not random. But if fundamentally contingent then maybe we can't. But in principle could for the logical case in question that matters to the argument.
I think you are a bit confused with the entropy…
Long story short: If you are able to trace every single molecule, every single photon, every single interaction… Than you use more energy doing that(thermodynamically), than the system itself increasing its entropy!
So yes, theoretically, you can do that, and extract all the information that book had!
Adding gasoline to the system or doing whatever else, still keeps T
@@user-qw6ht7jw2b What you are saying is basically quite comical or a misunderstanding of basic physics. But this seems to be pretty widespread. A photon by its automatic spinstates is always a wave from and on its own. Several photons make up a light ray. The spin details cause the qualities (frequencies and intensity) of the waves. There are no mystical wave forms in space of itself. Once you have a spinning top toy with its leg painted moving along a paper, it will draw a wave. Until it runs out of energy (due to the Earth). In open space it would probably continue longer by spin because the entropy would increase much slower. Now if you close your eyes and miss some of the path of the wavedrawing toy, that doesnt mean that the toy jumped through space randomly. Given particles they move extremely fast. You can not detect their position, although of course any position is fake (since all always moves, see Einstein's 4th dimension). It is easier to adapt our motion or to observe or calculate future paths of the relatively slower (with no mass or almost no mass one moves at or near C, thus becoming more or less unrelativistic)
Sabine, please never stop making TH-cam videos.
As an Engineer rather than a Physicist I have to admire real world experiments. Thanks for the new Green Screen life change.
Wonderful little talk. I didn't understand all of it.
btw Penrose says something about this problem - he said that the Schrodinger equation is a description of how the wave evolves over time but then you cannot start it off without measuring something so it doesn't work - even Schrodinger was worried about this aspect. Its in a recent Penrose video with Jordan Peterson I think, I haven't explained it well ....
Thank you for the video! I'm curious why time reversibility is assumed to be a given under such extreme circumstances, given that even a measurement breaks reversibility as far as I understand?
There is no "time reversibility," not really. Time reversal invariance (or the full CPT symmetry) is a symmetry of the _laws_ of physics, not of any particular physical system. The _laws_ of physics are not physical systems. What this means is that if you see a broken egg reassemble you cannot say any law of physics was violated. You can only say someone probably ran the universe backwards for a bit (entropy was lowered) or you got unbelievably lucky.
If you assume the Copenhagen (non-)interpretation, your objection totally makes sense. It is as if physicists insisted on applying unitary Schroedinger dynamics in the most extreme of regimes... but at the same time forgot that they are negating it in much more mundane regimes. --- I just think that Copenhagen should be abandoned, Everett should be embraced, and yes, as Sabine says the black hole information paradox is an actual logical inconsistency between quantum mechanics and General Relativity.
@@Achrononmaster isn't it also possible that a blackhole's Hawking Radiation creates a book by the same logic? On the other hand, the measurement problem says that you cannot restore the full wave function after the measurement. If you invert time for whatever law governs collapse, you end up with a different wave function originating from that point.
The thumbnail is a chef-d'oeuvre!
Can even the information loss be real from our reference system? Since, from our frame, we cannot actually observe an object pass the event horizon, even in an infinite amount of time?
This is only the case for eternal black holes (which only exist mathematically), not for real black holes which (to our best current knowledge) evaporate. We would see stuff falling into them an disappearing in finite time.
@@SabineHossenfelder thanks! I only have some knowledge of mathematics behind relativity and time dilation effects. I'm gonna go deeper into the subject then, i didn't know the difference between the eternal ones and the realistic model.
@@arkhamnygma4278 she explains this in the video as well
@@SabineHossenfelder : How small is that "finite time?" Are you saying objects fall past the event horizon BEFORE the rate of black hole evaporation becomes significant enough to be measurable? If not, would the object's information still outside the event horizon cause the Hawking radiation to be non-random?
@@brothermine2292 Planck time?
That was awesome! Nailed it. Thank you.
Like the black hole paradox outfit.
I took a mathematical physics class in college several years ago and I remember covering Lagrange functions and matrix groups that described movements of particles. But never have I heard the topic of black holes described so well. Thank you Sabine!
I think you touched on a point that may lead us to a solution Sabina. "The information comes out over billions and billions of years". The information in that book before you throw it in the black hole is encoded over space. When the information from the book comes out of the black hole it is encoded over time. Kind of like a text to speech program does to a book. We just have to figure out what algorithm it uses to encode space into time.
That’s why I never got into working with the information paradox. Instead I focused on more mathematical problems and eventually left academia altogether. Best decision in my life
Would it be solvable with a Quantum Gravitational theory.
Say for example someone claimed they had such a theory, should the expectation be that it could be used to calculate what happens. As opposed to theories claiming multiple universes exist, could this be a test for such a theory?
Yes any quantum gravity theory is expected to be able to solve this problem.
However, I should clarify that the information paradox goes beyond the simple fact that we don’t have a theory for quantum gravity. Einstein’s equations are expected to be valid for describing black holes. And hawkings theory of Hawking radiation describes how radiation comes from black holes. It is a quantum field theory calculation in a situation where quantum field theory is expected to be valid. And together, these calculations seem to form a paradox. Probably, either quantum field theory as we know it isn’t valid near event horizons, or Einstein’s equations aren’t valid for describing black holes.
In theory, one could test their quantum gravity theory by doing measurements on black holes, but the problem persists that we haven’t imagined any way of detecting radiation from black holes.
As Andrew says correctly, quantum gravity is expected to solve the problem. However, since we don't have this theory we can't do the calculation. Hence, physicists try other things.
@@SabineHossenfelder Please, make an episode on rotating Eishtein-Rosen bridges? Many thanks.
@@SabineHossenfelder Everyday and every new video you become more attractive to me💯 I am a sapiosexual. More that we realize that objective truths cannot exist because of the fact that we are not Immortal beings and the only way to have addictive truth is to live forever from the beginning of time to the end of time and none of us 3rd dimensional beings have that ability the more that that shines through in your work it really turns me on. You are an amazing human being😍💯🌈🦄
@@AquarianSoulTimeTraveler yikes
I am so happy you haven’t changed your attitude toward math vs physics. It makes me feel better about not knowing answers in general.
She said "math" but the word "math" she said is acually means a physical theory. She says about theoretical physics vs experiments. I don't know why she dosen't distinguish math and mathematical models of physical systems.
The information loss paradox has me wondering if, perhaps, the only information the universe truly cares to conserve are the properties of mass, angular momentum, and charge. They seem to be the defining qualities of particles, after all 🤔
@Christopher Grant how do you figure? If quantum mechanics says information is conserved, and GR says black holes only have three "hairs," why shouldn't we consider reconciling the two in this way? I'm definitely not married to the idea, but I figure it's worth consideration.
Yeah I mean when trying to reconstruct the burned book, I have a sneaking suspicion that a given smudge of ash probably could have been produced exactly in that state from about 2 billion different combinations of letters. Like simplify it down to a simple line is what remains and then try to determine if that line had once been two separate lines combined or 10B little lines combined or some number in between... How do we really believe that we can infer past state from present state when about a bazillion past states just a tincy bit different from one another could have caused the exact same final state? Hard for me to intuit it anyways.
@@TheSkystrider But I think this is the problem - you assume two initial states CAN produce the exact same resulting state. This should not be possible according to QP. Unless...perhaps..for black holes.
The problem is that if you take two particles and mash them together into a particle with, say, '10' mass and no other properties, you have no way of knowing whether the particles that made it up had masses of 1 & 9, 2 & 8, 5 & 5, and so on. That more complex informational state has been erased irreversibly.
@Alfred Wedmore In the silicon sheet experiment, all the information that described the original complex crystaline structure was release as non-random energy during the course of its melting and reformation - heat energy is highly disordered and entropic, but that's not the same thing as random. If I had carefully recorded the entire process I could (in principle) figure out what its original shape was from the 'waste' energy given off during the process - for example you would see the complex pattern *glowing* as it dissolved, providing a time-lapse record of its form that you could record or remember, and hypothetically reverse. You as a human certainly wouldn't be able to discern its entire atomic makeup this way, you'd need unimaginably sensitive instruments capturing the entire output of the process, but you get the point.
Congrats Sabine. Flawless video.
their is something that bothers me every time I hear about this subject . I hope someone can help me understand.
There is definitely something wrong with the theory and of mathematicians have no problem putting Infinity everywhere, we have no scientific evidence that Infinity exist in the real world.
So question is this: Can the math just be wrong and the center of a blacj hole is not a singularity but just an extremely dense object ?
I mean if the mass is big enough to curve space-time enough so the light can't escape, It should look exactly the same from the outside right ?
I can help. General Relativity doesn't actually predict the formation of black holes from an outside observer's perspective, despite permitting the solution. As a shell of matter undergoes gravitational collapse, the gravitational time dilation increases in the space the matter occupies, slowing its collapse. As the collapsing surface of mass/energy approaches the would-be event horizon, the collapse gets slowed more and more. This slowing is severe enough that the collapsing surface of mass/energy never even meets the would-be event horizon, only gets infinitesimally close. This structure is known as a shell collapsar. If you throw more matter into the shell collapsar, it'll plunge the matter below it into a gravitational well, sucking the mass/energy out of it and into itself. The result is the shell collapsar grows, but still doesn't become a black hole. For a shell collapsar, all the mass/energy is concentrated infinitesimally above where the would-be event horizon would form. Shell collapsars look identical to black holes from the outside and have no event horizons nor singularities. So the solution to the black hole information paradox is black holes aren't real so there can't be a paradox.
Thank you so much for taking the time to answer.
But again, if the math are wrong. If the plank limit is way smaller than predicted. Couldn't we arrive at a critical mass that would generate an event horizon without the need of a singularity ?
Wouldn't this be the simplest answer to the lost information paradox ?
@@MrSpantra The existence of an infinity is generally suspected of being an imperfection of the math, meaning the core singularity of a black hole should still have volume.
and if it does have volume, the black hole paradox doesn't exist because you would gind all the information in the core of the black hole. Hence my question
I love this! There are so many channels talking objectively about the output of science, but not many that talk about the processes and the value, or lack there of, of those ideas. So good to get this insiders view. Especially on physics, cause it one of these areas where non experts like me can’t even begin to accurately judge the relative importance of anything.
Isn't the "simplest" solution to state that falling into a black hole constitutes a measurement process? And if GR breaks at the Cauchy horizon, aren't physicists putting the cart before the horse trying to solve this problem?
I believe there should always be a disclaimer (maybe in a form of a video watermark?) that BHIP results from the incompatibility and incompleteness of two models rather than exists as a physical phenomenon.
No, that's nonsense. GR does not "break" at a Cauchy horizon. Cauchy surfaces were invented by GR! GR does not even "break" at a singularity, all physics surrounding a singularity is well-defined. It is only up extremely close when the singularity might get "fuzzed out" by "quantum noise" (a fantasy term, but physicists have to worry about what it means) that classical GR does not apply. But _non-classical Classical_ GR might apply, that is, GR with non-trivial spacetime topology --- which is possibly the ultimate explanation for quantum mechanics. (Or to coin a new Wheelerism: "quantum mechanics without quantum mechanics.") More people should look into this.
Physicists are putting the cart before the horse in trying to solve the BHIP instead of the Measurement Problem.
There's nothing at a black hole horizon. It's just empty space. What is supposed to be doing the measurement?
@@SabineHossenfelder If I understand correctly the Penrose's viewpoint, gravity alone could induce OR ('objective reduction') of a quantum state?
I struggle to believe that if I wrote something on a piece of paper, then rubbed it out, you could observe the rubber flakes or whatnot to discover the information that had been lost. I could throw the paper in a fire. It's all over my head.
I don't understand the paradox. You only end with lost information in the thermal radiation because you have no clue about the process that created it. If you only have light you can't recreate the lightbulb from it, let alone the generator that powered it. The preservation of information demands that you know every aspect involved.
As far as I have understood it Hawking radiation forms when a virtual particle/antiparticle pair is separated at the event horizon. Therefore, it is only dependent on the black hole's mass, angular momentum and electric charge and not on what specifically formed the black hole.
@@theouxepl1222 I don't really get it. You put said book into the black hole. It's mass increases by a book. Now that damn book has to come out of it somehow if the black hole is to evaporate over time. What happens to the book?
@@Unotch I don't know what happens to the book inside the black hole and I'm not sure if physics has an answer to that question as a black hole's inside is immeasurable.
But what may help you is the idea, that the book's matter is nowhere to be found in the Hawking radiation. You can not determine whether a given emitted particle originated from the book, not practically but also not in principle. Rather, Hawking radiation happens "on its own" (due to quantum fluctuation creating particle/antiparticle pairs right at the event horizon) and as a consequence in order to conserve energy the black hole must experience negative energy thus lose mass.
@@theouxepl1222 That's ... unsettling. How do you know that it fails at the conservation of information and not the conservation of energy? Because if the radiation has nothing to do with the things inside the BH ... well, SOMEHOW the book that fell in would have to end up as heat radiation or the black hole would not lose mass because the book would still be there. Well, compressed to atom core on atom core but still there. It would have to disappeare by something else doing something somewhere else and then it just goes away particle by particle - and then there STILL must be a certain mechanic behind it all. A black hole losing information is saying that something happens without ANY process behind it which i find frankly absurd ... well, THERE's the paradox.
Another solution could be that black holes do not evaporate at all, due to the fundamental misunderstanding of gravity.
Black holes could keep absorbing energy, even if not a single particle falls into it if gravity is spatial in nature. Gravity as an inward spatial flow, absorbing space itself and the energy it contains, countered by an outward spatial flow of energy that falls into a higher state of entropy. We need to give energy integral spatial properties to keep things in balance, so an increase in entropy causes spatial expansion to solve the dark energy mystery as well while we're at it :)
Eventualy the entropy in the universe becomes so high that the the inward spatial flow of gravity takes the upper hand, and the universe will start shrinking in size. The amount of (radiation) energy in space will still be magnitudes higher then the hawking radiation and due to the spatial absorbtion even giant black holes can eventually coalesce to form even bigger black holes.
The spatial absorbtion will continue till the point where all space-time is absorbed, and there is no more inward spatial flow, and thus no more gravity.
And with no more gravity the black hole will become the primordial seed of the next iteration of the universe...
Thinking about physics and cosmology without the hindrance of established scientific knowledge is fun :)
Would the paradox be considered solved if someone came up a theory of quantum gravity and proved it though other observations? Even if we aren't able to measure Hawking radiation, if that theory can consistently explain what happens to information that become trapped in black hole then it's as good as solved.
We don’t know if quantum gravity exists and we don’t know if the solution to quantum gravity would have any consequence on the solution of the paradox.
So, the solution wouldn’t be considered solved until a change in our current understanding of physics removes the paradox.
And to be honest, quantum mechanics allows for superposition. Which means that maybe 2 different solutions that seem like a paradox based on our understanding may not be a paradox at all.
Maybe your asking something different. Maybe your asking: If it can’t be directly measured but evidence strongly suggests information isn’t destroyed then is that good enough?
Well if it is good enough for a burning a book, I would suspect it is good enough for an evaporating black whole.
As from the external point of view the Schawartzshild horizon takes forever to form and anything falling in (e.g. a 'book') takes forever to get in. Thus no black hole paradox ever occurs. The information is always still there just outside the forming horizon. If it's a big black hole it might even still be 'readable'. If the 'book' is destroyed by the large forces it encounters this is no different than burning it in a fire.
I mathimatical black hole might have no hair, but a forming black hole never loses its hair.
Even if you start with a preformed black hole that has a horizon it still takes the 'book' forever to fall in.
Hi Sabine. I come from a biochemistry background, a field where many important advances were developed by physicists. I recognize that physicists are really smart people but researching topics like this (black holes) feel like a waste of their time.
It isn't a waste of time:
1. Black Holes DO exist
2. The apparent incongruence of the "inside" and "outside" of a black hole points to the black spots in our understanding of gravity and quantum theory
Super clear explanation 👍
Great argument and conclusion!
I absolutely love your logic sass!
Deine Lesungen sind (fast) immer gut, geraden weil du so kritisch bist, und das schätze ich👍👍
1. If we have a problem with information loss in black holes, why is there no issue with information loss across the cosmic horizon as the universe expands?
2. Would a record of what fell into a black hole not continue to exist in the position and motion of particles in the surrounding universe as a consequence of its existence outside it?
This type of problem is an example of arguing over how many angels can dance on the head of a pin. Without the possibility of experimental/observational confirmation of a hypothesis, it’s little more than speculation.
Excellent video again! Thank you! Cheers, Eddy.
I suspect that because we currently can't "see" into a black hole the best we can do is work off a foundation of assumptions and you know what they say about assumptions. The clearest thing to me is that we need new physics to fully understand black holes, it is like guessing what is in a black box we can't open. We can make a lot of guesses based on what we can see and measure from the outside, we can eliminate a great number of things but we still can't know what is inside until we can look. For this reason I understand the drive to keep trying, who knows some really cool new physics might emerge from the research, but I can also understand why some physicists such as yourself walk away from the problem until something new is discovered that gives us that peek inside.
Sabine, please tell your opinion about the following. Firstly, humans body consists mostly of empty space (considering the ranges between electrons and protons/neutrons, etc.). Second, we have good examples when several signals don't interfere each other (e.g. radio). The question is: IF we change internal (particle) frequencies of an object A, then could it be that object B passes through A without any difficulties? For instance, if I want to pass through a wall to get home, and a wall changes its internal frequency - is it possible in principle to pass through it? That would be very convenient... Thank you.
To get a handle on the black hole information loss paradox (if it really is a paradox), I suspect that we would either need to find a black hole that is small enough to have measurable Hawking Radiation OR prove that a black hole that small cannot exist (as in anything below a certain mass, potentially up in the lower stellar range, quits being a black hole).
Love your videos! Learnt something today, *again*!
0:54 I am listening to this with nice headphones on. This was dope. 10/10 would enter black hole again.
Excellent commentary! This video prompted me to purchase your book "Lost In Math". I have been suspicious for many years that the the beauty of math can lead smart people to erroneous conclusions. Your views are a balm, yet we still need mathematicians and physicists to place themselves on "The Foreskin Of Science" to discover Nature's secrets.
THANK YOU!
the great thing about explaining zero is you can't be challenged about your explanations if you use the right words and the right syntax and remove the boogie man correctly