Kerr is like, "I wonder how long it will take them to notice this obvious mistake." 60 years passes. "Ok, ok, they are hopeless. Here's the answer, while I'm still here"
Yeah, pretty much this. At MIT in 1980, I remember asking a physics major whether, if it takes infinite sidereal time for matter to reach the event horizon, black holes can actually ever form from a practical perspective. He said he didn't know because MIT didn't teach relativity, just quantum mechanics. Note that the mistake Kerr points out is not a mistake in the math, just in the interpretation.
This does not prove that any of us were mentaly inadequate. And why not? Both arguments are about the nature of a geometric concept. What happens inside the space we call an Event Horizon will remain a mystery until someone goes into that special space and returns from that world to tell us what that heaven or hell was like. So, to claim that Penrose and Hawking are sacardotes and the rest of us have sat ignorantly in the Space Time Cathedral only means the author still sits in Space-Time Cathedral praying for the absolute observed truth that lies on the other side of the veil with the rest of us.
Did Kerr look at the light skewing of the “white hole” (area/region before the event horizon of the black hole to pre amp universal operable light towards the black hole)???? Now how about the relativity of how we are able to observe the operable light coming from that region? And is there any hydrogen/ice/ bound gravitational lightwaves in heavy volume that are interacting along the way with that operable light volume we are able to detect and observe with the limitations of size and instrument baseline variable considerations not considered???? I think so unfortunately
Ask Brian Keating how volumes of hydrogen (in earths atmosphere as well as proximally in space) will polarize light, no matter the form of resonance for that hydrogen volume considered as well as gravitational waves as the wind in those volumes of hydrogen considered
I stumbled upon Kerr's article a bit on accident two weeks ago or so. I thought that if he's correct, then that would be an incredible realization in theoretical physics, and I wondered why I had almost seen nobody in the popular science space or media catching up to it. It's nice to see it's finally getting some attention.
Because the complication of that will be that the GR theory is actually absolutely ideal math but physically absolutely wrong. If we except that the GR is wrong, then the B.B. nonsense is wrong and there isn't a Universe's creation. No creation, then, isn't the need of a creator and the Vatican will disagree! Ha, ha, ha, ha. If the Vatican has a disagreement, then it will stop the gift and the money from the Vatican academy to the scientists! Then these scientists will have to work like Prof. Lerner in their garages!
Because like any group=think, they simply don't want it to be the truth or possible. Those who continue to insist the models are solid are doomed to be either disappointed by nearly everything or they will die before knowing how something really works.
@@catserver8577 Who is "they"? It's the lingo of a stupid conspiracy theorist. If by "they" you mean "theoretical physicists", then that's a very dumb thing to say. Who wouldn't want to disprove something and make a groundbreaking discovery?
@@catserver8577 Galileo Galilei has told: The scientist, is this person which is questioning and rejects everything! No, place for dogmas in science, because everything is under motion and under change. For that reason Heisenberg, e very dialectical scientist, describe the uncertain principle! For the same reason, Einstein isn't a scientist because he wrote 3 dogmas in his papers which are refusing even his SR's theory.
Hi Sabine, I love your channel and your videos. Unfortunately I must disagree on this one. I work on the problem of BH singularity and I need to say that it was very surprising to see this paper coming from someone like Kerr. My opinion (shared with everyone in the field I talked with) is that some of the statements are very well known, while the rest of the paper is incorrect. I’m particular, the main conclusion that Penrose theorem do not imply a curvature singularity is very well know. It is very clearly stated in the Hawking Ellis book. The technical reason is that Kerr geometry has a Cauchy horizon and Penrose paper only discusses globally hyperbolic spacetimes. The theorem only proves geodesic incompleteness. The reason why we believe the presence of singularities is not faith. It’s because there are a lot of result showing the instability of the Cauchy horizon (which seems to form a singularity) and because a stable Cauchy horizon would be much worse than a curvature singularity from the point of view of the well-posedness of the theory. Of course I realize that he is Kerr and this is just a random comment on youtube. But I hope that, if you read the comment, you’ll be curious enough to investigate the problem further!
Commenting on this so that she sees it. But also I thought that the divergence of the Kretschmann scalar also proved the existence of a singularity? And its ring-like etc? In super confused about this atm, but then again I haven’t done any GR in a couple of years.
Thank you. Geometric Spaces are emerging every 50 years since Hyperbolic Space. Let me try to list them Euclidean Space, Gallelain Space, Newtonian Space, Poinicaire Space, Mobius Space, Space-Time, Wheeler Space, and now Kerr Space. Those still are not enough descriptions of Space. Dark Matter, if it exists, could lie in a different Space. It is nice to be alive. Every day is a wonderful dream. Thank you 🙏
I'm not up to date on GR, but what do you think of this paper? arxiv.org/pdf/1710.01722.pdf It claims to prove that Cauchy horizons can in fact be stable. It's over 200 pages long though, so I haven't actually read it.
This is an interesting point. By the Cauchy horizon, I assume you mean the one at the inner horizon of a Kerr black hole? Kerr argues in this new paper that the ring singularity could be replaced by some nonsingular, finite matter distribution within the inner horizon, but he didn't comment on how (or if) that would resolve any of the issues that occur on the inner horizon.
@@frede1905 Thanks for this clarification (need to read the paper). I guess since the Kerr singularity is two dimensional, we are free to patch it with a timelike four dimensional bagel or something. Anyone could’ve argued this though, so then the result isn’t surprising. In any case the whole Cauchy horizon question remains… I guess this is stuff we already knew, no one actually understands the interior of a Kerr black hole.
7 months later and Kerr's paper, on which this video is based on, still hasn't been published because it's bunk. That's the danger of latching onto sensationalistic pre-print papers which haven't been peer-reviewed.
It's not exciting when you have just much of BS flying around accepted as "facts". Kerr just had the credentials to be accepted by physics. Mathematicians have distanced them self from this crap already a long time ago.
I apologise for my dubious tone, but... what excitement exactly? We continually find the wrong answer, as this video even shows... is this really a time for self congratulation? Shouldn't we take a step back and ask where it is we went wrong?
@@KieranLeCam I figure it exciting that, following my perception, there is a moving in research again, after decades of stagnation, that SH described so accurate in her book 'Lost In Math'. Of course, you're right, it's a way of try and error, but that's how the scientific method works, no? Last decades, everyone just followed the mainstream scientific establishment. Just my thoughts.
@@KieranLeCam Another way to look at this -- we are continuing to update our understanding of the world. Science is a process of continual refinement of models and all models are limited (if a model was 100% accurate, it would just be the thing itself that is being modeled, rather than a model). Since Knowledge is probably infinite, we will always be updating our models -- we will always be wrong about something. You gotta get used to it. Being wrong about something is the first step towards being right about it.
Having finished reading Kerr's recent paper, i think that the major problem with it is that ignores all developments that have been done in recent years about the instability phenomenon that occurs in the vicinity of the inner horizon of both Rotating and Charged Black Holes. This "blueshift" instability was originally pointed out by Penrose himself for Reissner Nordstrom black holes ( that have an inner Cauchy horizon, similar to Kerr) and later was confirmed by the famous papers from Poisson et al : "Inner Horizon instability and mass inflation in black holes" -1989 & "Internal structure of Black Holes" ( Physical Review D-1990) where the phenomenon was dubbed " Mass Inflation Instability" and occurs both in Rotating and Charged Black Holes. The consequences are : - That the region *beyond* the inner Cauchy horizon ( where in the eternal Kerr solution there are no trapped surfaces - as it is stated in Kerr's paper) *is not there* in physical Rotating Black Holes! There's no smooth transition, because instead of a Cauchy horizon, a null singularity is developed there, or even a Spacelike singularity, depending on the details! - What lies beyond the weak null singularity ( that replaces the inner horizon of the idealised vacuum Kerr solution, if there are slight perturbations from a matter field) is merely unknown. "Weak" solutions for the Einstein equation? - In more realistic cases, a strong spacelike singularity appears, so there's no extension in that case... In Kerr's paper there are neither references to the above mentioned Poisson et al papers, nor any references to subsequent papers that extensively investigated the instability ( e.g. by Ori et al, A. Hamilton, Dafermos et al, to mention only a few...).
I've never believed in point singularities because, in that case, angular rotation rate would have to be infinite. On the other hand, a ring singularity can still have finite rotation rate. Plus, the fact that black holes appear to have polar jets goes well with the ring singularity view. A ring singularity leaves open the possibility that matter that enters exactly from above the North, or below the South pole might have a small chance of passing through the ring's center and appearing on the other side.
@@robguyatt9602 Polar jets are external to the event horizon yes, you can essentially have star core like conditions just outside the event horizon with enough infalling matter and the geometry of the accretion disk means the poles have vastly less matter to absorb the radiation produced hence; polar jets.
@@volentimeh Ah got ya. I had a thought. Do the jets go both away from as well as toward the centre of the black hole? I'm thinking they are just high energy collisions of matter with only two directions to go. That being into and away from. Obviously, we can only observe one of those directions. I also imagine matter remains matter in the normal sense for quite some distance toward the centre after crossing the event horizon. It must be quite a particle soup in there before whatever the end looks like. :)
Hey Sabine love your small bite size format but will you be posting an anthology of all the bites at the end of the week as before. It was one of my weekend highlights to enjoy over a nice morning coffee
Vielen Dank Sabine! Kerr deserves the Noble Prize for this. So happy you gave him the attention he deserves. There is one additional thing Kerr has missed but thats on the physical interpretations side. Indeed what happens at the collapse of a BH is that space and time seem to be collapsing to zero, however since they are inversely related to energy and mass, what actually happens is that at the central ring the grid (defined in terms of energy and mass) actually grows!!! After all mass is inverse time (Penrose substitutes Plank E=hf into E=MC2 for this) so our galactic core actually increases in size (in terms of energy as the grid) as in spatial sense it decreases. And Heisenberg stresses the inverse relation between energy and space in dXdP>=h/2) . It also means we should see our galactic plane as an energy dominated grid, with again minor energy singularities in it (stars) in around which we have emergent and overlapping spacetime bubbles that make up our galactic spiral are. At area without stars (between the spiral arms) we don't have these emergent spacetime bubble ,so the spatial distance between outer galactic stars and the Milky Way core is actually less then we observe, and so are the absolute rotational speeds of outer galactic arms. This solves the strange rotational speed curves mystery hence no need for Dark Matter.....
I didn’t think any physicists thought black holes *actually* contained singularities. The “singularity” didn’t represent a physical object, but rather the limits of the math of general relativity.
That didn't seem to have prevented Penrose from getting a Nobel Prize for _Physics._ Still, for other reasons I didn't think they're physical, as well; fun thing, in my own theory (which, in case you wonder, has been submitted for publication) there doesn't seem to be any black-hole-like vacuum solution to the field equations, which is kinda cool - suggesting I don't even need to bother with convoluted interpretations of what happens near a point-mass.
I've seen enough lectures now that suggest that a fair number of physicists had talked themselves into it, they've certainly spent an *inordinate* amount of time trying to model physical behaviors below the EH.
@@thstroyur "there doesn't seem to be any black-hole-like vacuum solution to the field equations" So the Schwarzschild solution and the Kerr solution are not "black-hole-like"? Or don't you count those as "vacuum solutions"?
Quite the opposite - there does not seem to be any way whatsoever to remove the singularity as they're defined (the singularity theorems) where the gravitational field is well-enough understood and obeys reasonable energy conditions. Even is string theory there are singularities that appear necessary to keep the vacuum stable. The expectation is more that some quantum theory of the gravitational field will resolve the singularity, i.e. perhaps remove the divergence of the curvature invariants or give some meaning to them that's sensible.
I come here to hear about things that I don't have a full grasp of or even unaware about. It makes me not stale! Have you had your coffee already? Lots'a love, cheers, & Mabuhay, from tropical Philippines!
Nothing makes me sadder that knowing given my circumstances there was no way for me to become a physicist and live out a decent life at the same time(I dont live in a first world country). I must say when I'm older and have finished my live's goals I might consider just taking a dive into physics just to understand it.
I'm an old fart and do live in the first world. My limitation is my academic ability. I became a welder after high school. But I frequented the local library for all things science and now use the internet to quench my thirst for knowledge.
What country do you live in if you don't mind me asking. Since it appears you know English well, then you could've become an international student at the many universities that have instruction in English. Many in Europe have free tuition and there are also scholarships in the US as well.
@@robguyatt9602academic ability or opportunity? For instance simple particle in a box, with infinite potential well you ca do with maths at school, the 17 18 year level stuff. After that it is time a determination. There the path is long and gradual but not impossible. And you are never too late
1:35 "or so we thought" - but many physicists _over many years_ have pointed out that mathematical singularities are not physical things. (Which Sabine _briefly_ mentioned a bit later.)
Yes but there is a big difference between "Singularities are math artifacts, not reality, so we are looking for new physics to explain what is missing from the math that explains why the black hole singularity doesn't exist.". And Kerr saying, "The original math had an error, and thus the singularity never truly appeared in the math in the first place."
You need an answer yet you ask on a random video of the internet where nobody would hear. Remember back then when trump was government and everyone was burning cities? Don't you think this is city burning worthy?
To me, math is a tool for approximating whats happening in reality but never a description of reality itself and I have always been frustrated how people seem to get those mixed up.
5:03 As many have pointed out, including Sabine herself, I think, numerical methods are not good enough when it comes to ultra small scales and/or extra large densities.
Yep. Perhaps we'll invoke "magic". I was taught that the math[s] show a singularity, but in reality, nobody can know. But that was long ago, and perhaps some day we _will_ know, for sure. "Singularity" is such a beautiful concept, that I want to believe!
I was always confused why the larger scientific community thought black holes have a singularity in them. I had always thought a slightly more compact neutron star was at the center of black holes, possibly with the surface right underneath the event horizon. Physically, that makes more sense than a single point with all the matter condensed down to that one point.
From what I understand, the black hole singularity forms precisely when something like a neutron star reaches a point where gravitational interactions overpower the nuclear interactions, leading to a shrinking in size and increase in density as the star collapses. At that point, our current models of physics and math sort of break, but that doesn't necessarily mean it doesn't exist. It's like fluid dynamics, we don't have a formula to fully describe it, yet we can observe it in action and make some predictions, even if not 100% accurate
Kerr's paper and arguments seems to have flat-lined. At least with leading general relativists. According to them, it's just rookie mistake from a veteran! Sorry Sabine!
I spoken with Roy Kerr about this a few times and shared our conversation with other relativists and between us we've concluded that he's blatantly wrong, but we've also concluded that Roy Kerr is Roy Kerr and we're not, so maybe we're wrong. Anyway, the gist of our reasoning was (is) as follows... What he's calculated is for a pair of NPVs that asymptote on the inner horizon (infinite in geodesic length) with a finite value for some choice of the affine parameter. What we find bizarre is that this is exactly what defines a singularity, so it seems he seems to have demonstrated there's a singularity, and then uses this to say that there isn't one. For the sake of example, in Schwarzschild we can take two rocks and drop them across the horizon (over the same radial line) and show that the proper distance between the two (the geodesic length) goes to infinity, but, we can show that for each of them the elapsed proper time (the typical affine parameter along a world-line) is finite. I don't even think Roy Kerr is arguing there's no singularity in the Schwarzschild geometry. Part of me wonders if this paper will garner much interest as Kerr is working in the original Kerr-Schild coordinates as he envisioned it all in the 1960s and we've come along way since then and current research is in more realistic (e.g. perturbed Kerr geometry) physics in which there's multiple singularities (mass inflation, BKL, null) and often requiring numerical methods to solve hard numerical problems. Additionally, in few conversations over the past couple of years there is a clear and deep animosity towards Roger Penrose, Hawking, and others. This too has us wondering if decades of festering animosity left his math skills intact but left his objectivity in question.
This wouldn't be the first time that an eminent scientist in their 80s makes a confident and wrong declaration that for years, their field has been on the wrong track
I'm still an undergrad so I may be (probably will be) wrong on this one Isn't Kerr's argument that, null geodesics terminating at finite affine parameter doesn't always mean that there is a singularity? His example of a geodesic between the two horizons couldn't have approached a singularity since the singularity in the Kerr metric appears strictly inside the inner horizon, right?
@@ricksonwielian3548 In the analytic continuation the ring singularity is indeed interior to the inner horizon, but in the perturbative analysis there's a singularity at the inner horizon, the mass inflation singularity. Roy Kerr seems to picked up from where he left off in 1963 and is not making arguments for/against subsequent work. Yes, he's making a claim that he's getting a null curve with finite affine parameter and stating this means there's no singularity, which is incoherent (at least to myself and everyone I've spoken to as a finite affine parameter is what we mean by a singularity). We're not sure if he means that the curvature invariants, e.g. Kretschmann don't diverge upon the limit of the affine parameter or if he's found a solution with a quasi-regular singularity or what, nobody seems to know.
Indeed, Kerr only speaks about curvature singularities, or alternatively points where the metric loses its required differentiability - he clarifies this usage of the word "singularity" at the beginning of the paper. I agree that Penrose's theorem most definitely proves that black hole spacetimes are singular in some broad sense - as per the definition that spacetimes are singular if they are null or timelike geodesically incomplete. But wouldn't it be significant if black holes do not have to contain curvature singularities or points where the metric loses its required smoothness/differentiability? Don't most relativists imagine that black holes contain that kind of singularity, not just merely that spacetime is singular in some broad sense? Although I found it interesting that he didn't discuss the problems that occur on the inner horizon of a Kerr black hole, whether a black hole without this kind of singularity would be stable etc. as you pointed out.
The Pauli Exclusion Principle applies to fermions, but not bosons. At some stage in the 'crushing down' process, the fundamental particles will be forced to decay into bosons, which can occupy the same point in space. I think most people would agree that the singularity, if one exists, is a 'container' of energy, not matter. I am not suggesting that the singularity is just a vast number of bosons all concentrated at a single point in space, I am suggesting that the conversion to bosons is a phase that the infalling matter goes through, before being converted into some very exotic form of energy, as might be described by string theory.
@@richardconway6425 That’s really interesting, and I’m surprised I’ve never read or heard any physicist talk about that decay process before. It seems like it would be really important when talking about what might be inside a black hole. Do you have any links to sources where I could read more?
@@DaHuuudge ha, no ! Sorry I don't. My explanation is based on my understanding of physics, and not on any particular theory or paper. Funnily enough, I have never heard any physicist talking about his either, and that's most likely because any discussion on the likely nature of the singularity, and the 'crushing down' phase of the infalling matter is highly speculative. Physicists tend to be quite reluctant to speculate on matters such as these, at least in public, because they are afraid of talking about things for which there is no known physics, and equally, they are afraid of reputational damage to their credibility as a respected scientist. They are afraid that other scientists may think them 'unscientific', which is the polite way of saying 'fanciful', or worse 'superstitious'. It is interesting that Stephen Hawking essentially built his reputation as a world leading theoretical phycist by investigating this very difficult subject, and writing his paper on black hole radiation. His theory was built on a very creative approach - he considered both the effects of quantum mechanics, and general relativity, and, with a bit of clever maths, came up with a way of describing what happens around the 'singularity'. He and Roger Penrose had already collaborated on a previous paper, that proved mathematically that a singularity must exist at the centre of a black hole (I believe they considered the simplest case, that of a Schwarzschild black hole), so there was no doubt in his mind that one must exist. He came up with a way of describing how the quantum fields of QFT were somehow destabilised and perturbed in the near infinite curvature of spacetime around the singularity. This somehow produced the very unexpected effect of causing black body radiation from the event horizon of the black hole, at a temperature of 2.7 K. Leonard Susskind described it as 'brilliant', and said he thought the maths was 'watertight'. The physics community seems to have accepted it, which I actually find quite surprising. The theory seems to me to be potentially flawed for the following reasons: Stephen Hawking used quantum mechanics to build his theory, unfortunately the prediction it makes fatally undermines one of the sacred cornerstones of QM itself, that is, the principle of conservation of information. This is not a good start. This problem can be mitigated, but only if you accept another, incredible theory, that of the 'Bekenstein Bound', and the 'information theory' of black holes. This seems to suggest that all the quantum mechanical 'information' that fell into a black hole, is now somehow perfectly smeared out over the event horizon at the Planck scale. This means that outgoing Hawking radiation can somehow 'take' this information with it, resolving this loss of information problem. It's safe to say that this is all quite speculative. The second problem with the theory is that it is untestable, or 'unfalsifiable', as scientists like to say. This is a very important concept in physics, and is sometimes used as the litmus test of a theory. If it's unfalsifiable, then it's not terribly useful as a theory, because none of its predictions can ever be tested. It's not that the theory is necessarily wrong, it just can't be tested one way or another, meaning we'll never know whether it's actually true or not. Some physicists will even go as far as to say that this makes it a 'bad' theory, although many would not agree with that. One of the reasons why Einstein's GR was such a good theory, was because it made many predictions which could be tested, some to great precision. The predictions it made did not require experiments proscribed by the laws of nature - the people who understood it knew that it was just a matter of time and technology before it could be tested. Space rockets, lasers, atomic clocks, massive optical and radio telescopes, those were the things that were going to make it possible, and people were already anticipating those things. However, Hawking's theory of black hole radiation may never be tested, because the surface temperature it predicts for the only type of black holes we can actually see, is significantly less than that of the cosmic microwave background. If it existed, it would simply be drowned out by the white noise of the cmb. A signal to noise impossibility. I digress. What I have been trying to illustrate, is that any discussion of what happens at the singularity is not only completely speculative, but it is clearly untestable. It is difficult enough to 'observe' the event horizon of a black hole, but getting any information 'back' from the singularity is clearly proscribed by nature. Everything beyond the event horizon is causally disconnected from the rest of the universe. Forever. We do have physics that describes very well the process of stellar collapse into neutron stars, which are the most extreme astrophysical objects we know of. Physicists are reluctant nowadays to even use the word 'object' to describe a black hole, such is their reluctance to commit themselves to anything for which they could later be dismissed, intellectually speaking. The Chandrasekhar limit describes how the electron degeneracy limit determines the point at which a white dwarf, for example, will collapse into a neutron star. It's entirely dependant on its mass, which in turn determines it's own gravitational field, which determines the forces involved trying to squeeze together it's matter. (There's a really good youtube channel called 'physics explained' which goes through the principles and math of this). Turns out to be 1.4 solar masses. A neutron star can only withstand so much pressure. Again it's mass dependent. There's the idea of a 'neutron degeneracy limit', you can only force them together so much, before they too yield, and dissolve into an ultra hot quark-gluon plasma. That's the densest form of matter that we are sure exists, and interestingly, it's thought that our early universe went through a phase when all of its spacetime was filled with this ultra energetic and dense medium. But of course, I understand, you want to know what happens when a neutron star collapses into a black hole. What happens to all of the trillions of tonnes of matter that rushes headlong to the centre, in an exponentially increasing gravitational field. It's own inward movement fuels the gravitational field - it is essentially creating it's own trap, as it becomes more and more crushed, more and more dense. It very quickly becomes a mathematical certainty that it will all end up in an impossibly tiny, deep, gravitational well. It's so difficult to understand, or even imagine what happens to the infalling matter, as it makes its journey to the singularity. Stephen Hawking described mathematically the environment in the immediate vicinity of the singularity, but not the singularity itself. It's just not possible. The best idea, or description, that I ever heard, was that it was a concentration of a vast amount of energy, in some very exotic form, smeared around in a tiny region of spacetime, that had a kind of indeterminacy in its location, according to quantum mechanics. But this is still all at the planck scale, so it's a distinction that will only be really appreciated by physicists. My original response to your comment was based on the idea that the fermions being drawn together at very high energies and pressures must, at some point, decay into bosons, or boson like 'particles ', because, as you so rightly pointed out, the PEP would not allow the superposition of even just two fermions. But our current understanding says that quarks and electrons are fundamental particles, they cannot be dismantled into anything else, except for the fact that this 'crush down' is happening in such extreme conditions, at such high energies, we don't actually know what would happen to fermions in these conditions. This seems to me to be a particle physics problem, so I would be very surprised if the Large Hadron Collider could not offer some information. I think this is probably where you should look for further information on this. Their collider spends most of its time smashing protons together. Since each proton is comprised of 3 quarks, perhaps they see some of the decay products when quarks get 'annihilated', and perhaps some of those are bosons. One interesting thing about fermions, is that sometimes they can pair up, then behave like bosons. An example of this would be superconductivity, where, at very low temperatures, electrons pair up and behave like a boson (single electrons have an integer spin value of one half, put two together, and they acquire an integer spin of 1. This then makes them a boson). This is already looking a bit more approachable, I am definitely going to look this up, so thank you for your question.
People often don't realize that there are many different kinds of singularities and tend to conflate them very often. Please check any of Jose Senovilla's review papers on this topic (or videos on RUclips - they are very detailed). For example, the curvature singularity as measured by, say, the divergence of the Kretschmann scalar is not the same as the singularity through which we cannot extend curves (Penrose-Hawking singularity). Actually, Penrose-Hawking theorems are non-constructive proofs, so we actually don't know where these singularities really are (although where else, if not where the Kretschmann diverges? - still, not a proof). Some people say, that Penrose-Hawking singularity theorems should be called manifold completeness theorems because this is how mathematicians call them when they study purely Riemannian manifolds (i.e. purely spacelike manifolds). The singularity name was attached because the sudden (dis)appearance of a physical particle would mean something serious, so "singularity" in this case stands for something strange and serious happening, not an explosion or divergence of some value. I have listened to most of the talks of Prof. Kerr on RUclips, and from what I remember, his argument rests upon the exact solutions being just idealizations with unphysical properties. Kerr black hole also has them, for example, the inner horizon is known as the Cauchy horizon and is highly unstable against perturbations. Another observation is that many singularities in reality are not singularities, because any pair of particles usually have a net non-zero angular momentum and hence create a bubble around themselves like in Kerr's case. One of his idealized proposed solutions was an almost infinite sequence of black holes within each other separated by layers of normally behaving spacetime, but this has never been developed to the full extent. Of course, most scientists do not believe that there is actual singularity because quantum effects are supposed to solve that, while now it seems that even classically this may not actually be a problem, but then we need to find an even better solution, and it would need to be evolving in time, so almost impossible to discover analytically.
I like Kerr’s argument. Once a thing pass the event horizon, it will keep speed of light to maintain its angular momentum. In order to fall inner, speed of light needs to be faster inside the black hole yet the angular momentum will still maintain and prevent it from falling further. So it should be fully empty inside.
I am total novice, but I thought is it possible that the spacetime is quite condensed yet not collapsing into a singularity. And maybe this condensed spacetime stabilizes heavier quark top quarks or maybe something beyond that decaying in ridiculously fast time frames we might not measure yet. This is analogous to neutron stars who condensed matter yet not beyond an event horizon.
Wait. You can’t just rotate a drawing of a back hole and see a dot from the “back” of it. Surely. (?) We struggle with this stuff for the same reasons you cannot just draw it. You can kinda draw a vortex like that, but in a black hole, as I understand you so far, the vortex looks the same from ALL points of view outside the event horizon. If I’ve got a bad assumption in here, please do a video to explain. (Bonus: I don’t think your drawing of “singularity” can be a good representation of that discussion either. The lines never converge. It’s an asymptote. Surely nobody ever drew the lines like in this video… (or cite one please?)
Thanks for explaining this. I've always had a problem accepting this. How can all that matter be compressed to a singularity? Nice to see Albert back 👍
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when you have the rotating cyclone of time quarcks they make bridges between the past and present, and are in some way outside of the space and can expand infinitely into a singurarity.
@ Or so one theory says. I find this highly improbable. Math is a model. But has this story points out, that model is up for interpretation. It still seems more likely that the reality of blackholes has far more variables than we are aware of and that information would explain its existence without the need for something that forces you to divide by 0 - a technical impossibility.
I was also very doubtful about singularities. But I'm just an aerospace engineer with love of physics. Who am I to judge things. That might have been part of the problem, when you have juggernauts like Hawkins and Penrose, a lot of people probably never fully committed to attempting to prove them wrong. I hope this leads to some cool new science and mathematical models for our universe :)
She said this doesn't prove black holes aren't singularities, just that the theory that claimed to prove it was wrong. It's easy to see how matter can be compressed to smallness when you realize that: A. Matter is mostly empty space; B, It might just be a mathematical construct; C, it's just like, all a simulation, man.
One thing I've always pondered is whether a singularity can technically ever form. According to (my understanding of) general relativity, time moves relatively slower when you're close to a gravitational source. That means that for an object falling into a black hole, the closer it gets to the singulairty, the faster time moves outside of the event horizon. If that's the case then can an object falling into a black hole ever techincally reach the singularity? The closer it gets, the faster time moves outside of the event horizon. Since black holes evaporate - albeit over a very long time period - the black hole will evaporate to the point where it's no longer a black hole, i.e. it will evaporate before any object hits the singularity. Thus no object can hit the singularity and thus no singularity actually exists. I first thought about this problem when I heard the following (slightly flippant) phrase many years ago: "if you fall into the center of a black hole then by the time you hit the center, the universe has ended". The reason why I thought of this in the context of the video is that there's some sort of asymptotic behaviour implied in the new paper. The above "argument" would lead to asymptotic behaviour, but only until a point. When the black hole evaporates enough then that asymptotic behaviour would stop. Anyway, if there are any GR experts here then I'd love to hear responses to the above argument. My guess is that the argument is invalid because my understanding of GR is too superficial.
Actually, it's probably the opposite, all the matter should be at the limit of the event horizon, for it would take an infinite amount of time for it to move an infinitesimal distance towards the center.
I'm lead to believe any object will fall towards the singularity at light speed maximum. And when you're at that speed, time doesn't count. Well, at least for photons, I'm not sure baryonic matter would behave the same way
Okay i got lectured twice within 6 minutes. First i didn't even know of the Hawking Penrose Theorem, i thought it was mainly accepted that singularities do not exist and are just mathematical artifacts. Now i learned about the curve argument and why it might no longer a valid argument anymore.
Well, it _is_ mainly accepted that singularities probably don't exist - as Sabine mentioned later, most physicists think that effects of quantum gravity prevent them.
yer faith in gandalf, his pink magician bastard and his assassin uncle is... indicative of trauma in your life, get help, don't smear your delusions on other people.
@@mareksgv Only for those of vain epistemology; it's been said before: the map isn't the territory. This is much closer to the heart of your ouroboros theory. Doing science is OK - turning it into an idol (scientism) isn't.
@@mareksgv The very fact that truth does truly exist means that there is a right and a wrong answer to the universe. One can be wrong and another right, or both can be wrong, but both cannot be right is a simple part of reasoning. If they counteract each other of course. The main issue with science today is not that science can't be done well or accurately. It also isn't a problem of us not knowing and making new ideas and theories, that is fine. It is that many scientists remove philosophy/theology from science as if it can't answer what is true or false. Science cannot answer many things in our universe, such as the value of man, morals, why math works, or even what is infinite for everything we see has a beginning. We see these laws of the universe but fail to ask the question where the laws come from, if they had a beginning or not. In the end the question, "Does truth exist?" is an amazing question. If you answer no then your answer can't be true or false, but it is made as a true statement and thus nullifies its own answer. This is a question that can be answered with reasoning, but not science. There is much more to this world than just physical properties and the denial of that is very dangerous. I believe in the God of the Bible. Whether you believe it doesn't make rational sense is definitely up to you. Evidence to me points to Him as the more likely answer. I also believe if you truly search and want to know the answer, He will reveal Himself to you and give the gift of faith. Have a blessed day!
I definitely prefer this format for your Science News bits. It feels like you are managing to give each topic more time and a better degree of presentation.
Kerrs paper from 15. November 2023 is not peer reviewed and many Physicists argue that Kerr confuses time and affined time and therefore Kerr does not get the math right.
Out-freaking-standing, Sabine!!! As usual. In that I’m also including your statement “including myself”. Too many times egos get in the way of solid science - or most other human endeavors for that “matter”. (Sorry, poor pun, but I couldn’t resist)
@@KieranLeCam How? She mentioned she didn't see the mistake, but then also discusses it's implications. "There what?" is the next question of ANY new information. That's not excusing herself. It's the next logical question.
. I believe although that the ego problem in science goes two way around: what it is the big deal with being wrong? data (and math in this case) allows only a limited interpretation of nature, and even if it is self-consistent, no wonder old theories gets revisited/refuted in the future. If efforts should be made to get rid of our egos to move forward, the community should do the same in not assigning such negative value to someone being wrong (i feel Sabine does poorly here, for such beautiful content she creates). Perhaps what is really wrong, is having no data (or worse, ignoring it) and take decisions in detriment of humanity, as we are so used to see nowadays. Being wrong and reformulating our ideas accordingly, is I think, one of most beautiful aspects of science
@@pansito_1 I agree with you. And science does allow for the possibility of being wrong, but I personally think it has become a very unimaginative endeavour. Being wrong isn't the issue, it's not learning from your mistakes that is. And science refuses to acknowledge the stagnation of progress in the explanatory power of our best theories, instead relying on the defence of the method itself, and using the concept of failure to justify continuing. Sabine mentions this herself with some physicists wanting ever larger particle colliders using the justification that it isn't their idea that is wrong, but the energies of what they're looking for that are too high to detect. I'm surprised Sabine, Arvin Ash, PBS Space Time, Anton Petrov, and many other science communicators aren't reporting a mass existential crisis in physics circles at never being good enough to find the answer to the deepest mysteries of the universe. Instead to avoid feeling uncomfortable, more often than not, physicists perform a mental gymnastics where they view themselves as both competent, because they understand some things, and humble, because the universe is just too darn difficult to understand. This is just like with the supercolliders, they are avoiding feeling bad about themselves by not putting into question their ideas, and methodologies, and the type of attitude they bring to the table, and putting the blame on the universe. That way they get to keep viewing themselves as experts, and intelligent, and they never need to feel the discomfort of having to change themselves. It's quite surprising to witness. I've never seen a physicist (despite a strong desire to not give up), be upset because we just seem to be stuck. It's like we're not stuck at all. It's just how science works they will say. Well, I think it's time to put ourselves into question. Because we're just not seeing the results.
To spin requires the black hole to occupy space as we understand and interact with. If they warp spacetime sufficiently, isn't it possible that are in fact _not_ spinning despite the conservation of angular momentum?
I have always wondered how a singularity could be said to rotate. For something to rotate, it must have a physical dimension that moves around the rotational axis.
@@henrikkowalski3144 To further exemplify the lack of an classical analog, the math says that an electron must spin _720_ degrees to return to its initial state. Electrons are just weird.
@@maxweber06 That's not weird. Take "any" 4 stroke internal combustion engine. The camshaft that actuates the valves rotates at half of the crank speed. That means you have to rotate the crank twice for the engine to return to the state you started. Nothing magical about it.
Black holes are based on a mathematical misconception. Most people don't know that Einstein said that singularities are not possible. In the 1939 journal "Annals of Mathematics" he wrote - "The essential result of this investigation is a clear understanding as to why the Schwarzchild singularities (Schwarzchild was the first to raise the issue of General Relativity predicting singularities) do not exist in physical reality. Although the theory given here treats only clusters (star clusters) whose particles move along circular paths it does seem subject to reasonable doubt that more general cases will have analogous results. The Schwarzchild singularities do not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light." He was referring to the phenomenon of dilation (sometimes called gamma or y) mass that is dilated is smeared through spacetime relative to an outside observer. It's the phenomenon behind the phrase "mass becomes infinite at the speed of light". Time dilation is one aspect of dilation. Dilation will occur wherever there is an astronomical quantity of mass because high mass means high momentum. There is no place in the universe where mass is more concentrated than at the center of a galaxy. Dilation is the original and correct explanation for why we cannot see light from the galactic center. It can be shown mathematically that dilation is occurring in our own galactic center. In other words that mass is all around us. Sound familiar? This is the explanation for dark matter, the missing mass is dilated mass. Einstein wrote about dilation occurring in "large clusters of stars" which is basically a very low mass galaxy. For a galaxy to have no/low dilation it must have very, very low mass (or low mass in its center). It has recently been confirmed in 5 very, very low mass galaxies to show no signs of dark matter. For the same reason binary stars will always have predictable rotation rates. What we see in modern astronomy has been known since 1925. This is when the existence of galaxies was confirmed. It was clear that there should be an astronomical quantity of light emanating from our own galactic center. It wasn't until the 1960's when television and movies started to popularize black holes did the concept slowly became mainstream.
The question I'd ask is: is there any reason why a neutron star which acquires mass until the escape velocity at its surface exceeds c simply causing it to wink out of view should undergo any further compression/shrinkage? Is there any hard requirement that matter should necessarily be compressed beyond neutron star density?
I'm just a filthy layman, but I think it's related to the whole; "Only things that have 0 mass can travel at C" thing. It's not so much the mass that's collapsing, it's reaching a tipping point where the whole (or part of the whole) thing is converted to energy; ie photons (which still affect gravity) Photons have that whole particle-wave thing going on so they can occupy the same "point" of seething near impossibly hot energy.
Another filthy layman, and probably a stupid question, but with the mass collapsing to the point where light cannot escape, and an event horizon is created, the closer Alice, Bob or whoever approach the event horizon relativistic effects increase the speed of time for the rest of the universe for Alice, Bob, whoever. This means that although time appears normal to them, effectively time stops when the event horizon is reached. So the person in question never actually reaches the event horizon. My point being, how does matter continue to collapse when time has effectively stopped? Therefore a singularity cannot exist in the black hole, it is simply a neutron star with gravity so strong that the light cannot escape. Please excuse this 'duh' question, but it has bothered me for a long time.
@@GeorgesDupont-do8peArvin Ash recent video of entering a black hole (big enough to not rip appart) , Said the person continue entering inside after event horizon normally . Observation from outside see the last image frozen as after that , no more light of that person comes. But also is strange where that frozen image have energy to be shown, without the person there...
Thank you for your response @RF-fi2pt. To add to my point, it seems that as time stops at the event horizon, the said person will never actually pass the event horizon and all the matter would completely fill the black hole up until the event horizon. Furthermore, as according to Professor Hawking, eventually the black hole will dissipate or explode due to Hawking radiation (eventually). Thus, it seems to me, poor know nothing that I am, that from the point of view of the black hole, the matter collapses until the event horizon is reached, and then immediately (as time has stopped at the event horizon) the black hole explodes/dissipates/whatever it does. Immediately from the point of the black hole that is. For space time 'unaffected' by the black hole, billions of years will have passed. Thus, from the black hole's point of view, it merely 'bounces' from collapse to whatever the final result is. Thus, no singularity just a very long time for everywhere else. Gives me a headache, wish I'd studied astrophysics.
I've been talking about this for a while. A singularity? Infinite density? NOPE! There is *no such thing* as infinite density or in fact infinite *anything* in the real world.
I've always wondered if there are black holes not massive enough for a singularity but still enough so for an event horizon, I wonder what the effects would be if a blackhole crossed that threshold
I wonder if that depends on the definition of a singularity. Does it merely need to be singular, or must it have no size in any dimension, and can it have a size but still be singular if space-time dimensions become meaningless near it.
@@bipolarminddroppings Not necessarily true. A singularity implies infinite curvature of space-time; an event horizon only needs the curvature to be above a certain limit. At the moment we don't know what mechanism could stop matter collapsing once the strong force is overcome in a neutron star accreting material, but that doesn't mean that there isn't something.
I read a book 30 years ago about super extreme Kerr objects (SEKO). Frankly, I didn't really understand much of it, but I was convinced of the existence of black holes. Thanks, Kerr.
I'm not going to lie, I don't understand much of this but the great thing is that Sabine is a principled scientist and so are the other characters in this episode of science history in the making. When the resolution of the questions raised here becomes available it'll be posted here.
I thought the energy required to move objects with increasing mass is what set the limit for how fast an object could move thru space (as that velocity would translate into a resistance). There would be no way to maintain spin as the event horizon is theoretically moving at the speed of light (so via frame dragging, any surface of a "dark star" would be grabbed by this mass; though between the event horizon and the surface, that "space" would consist of layers of twisted time, like the windings of a spring). *movement of black holes may even fall outside of gravitational physics, with their movement thru space based on some other property that allows information to travel faster than light, and binds all black holes together in a quasi-gravitational manner.
i'm a mathematician, not a physicist, and i haven't read the paper, but this seems like such an amateur mistake by penrose and hawking that i would more readily believe an 89 year-old kerr misunderstood their argument than that this mistake was actually made and overlooked for 60 years.
Never ever underestimate the capability of physicists those days to make stuff up. If they came up with the singularity stuff 20 years later they would almost certainly have named it "dark space".
There's no mistake in the theorems by Penrose and Hawking - they prove what they claim to prove. It seems that what Kerr tries to argue is something against the interpretation of the theorem. The theorem by Penrose essentially proves that black hole spacetimes must be null geodesically incomplete, and Hawking and Penrose defines a spacetime to be singular if it is timelike or null geodesically incomplete (or, more generally, iff it is b-incomplete - see the definition of this term in the Hawking Ellis book). Hence Penrose's theorem proves that black hole spacetimes must contain a singularity. Then Kerr argues that the theorem does not guarantee that black holes must contain curvature singularity, or some point on the manifold where the metric is not sufficiently differentiable. This is HIS definition of a singularity in the entire paper. If black holes indeed do not require this kind of singularity, then to me that would seem like a significant realization (although I'm no expert on this) - but I honestly don't understand why Kerr picks fight against Penrose's theorem, as this theorem didn't claim to prove that black holes must contain Kerr's definition of singularity in the first place.
Yeah but no but the arrow travels across space to hit the target, and doesn't go past the target (yeah, the target's a singularity) but takes time to get there so never does. And neither does light. I'm picturing a Gideon's horn as some sort of analogy to the spacetimeyness.
I always assumed that time is frozen (or backwards) on the inside of a black hole. This would mean that matter would accumulate at the event horizon instead of at the center. it *would* lead to an interesting theory that you can technically keep something inside without annihilating it. (Though getting it in or out would probably be impossible) Also, assuming time goes backwards inside black holes, it could essentially be a mini universe. Black holes start large and eventually grow smaller and smaller before vaporizing into nothingness. Taking backwards logic for the inside, it goes from a very large essentially nothing with expanding border to a tiny dot of big bang vaporization. It's an insane theory without mathematical proof, but if it's true, it could tell us something about our own universe.
...Why does it need to be backwards? If spacetime is being stretched infinitely, the 'singularity' is unreachable because there's just more and more space and time inside the black hole before and outside where it would nominally happen, forever. No need to invoke any sort of inflection point besides the various limit horizons for trajectories and such.
time and space switch their roles inside a BH horizon. You can freely go in time, but all space only leads to the event horizont. No one knows what it means tough to be able to freely move in time.
This is much like going faster than light - the equations work but many things are reversed and the results are, to say the least, ridiculous. So no one takes it seriously. The same is true of the interior of BH. Yet some physicist do take those silly equations as fact and make those extreme claims. That isn't science and Kerr is correct. Its nonsense. And that is a scientific fact - lmao@@georgelionon9050
You don't understand relativity. Time moves at a normal speed in every reference frame. Including beyond the event horizon. It is just that when you have a way to try to compare how much time passed in different reference frames, they would be different. From an outside observer observing an event horizon, or an object close to it, it appears as if time is moving slower. But this is just an appearance. And a strong gravitational field will make the effect stronger.
This doesn't resolve anything at all, nor prove anyone right or wrong. It's a bit of mathematics re-framing the singularity to something that infinitely approaches zero size which is a singularity?. It technically gets rid of the singularity, replacing it with a singularity-like object, falling and stretching into infinity. Pretty sure people know the singularity is placeholder.
Thank you Dr. Sabine Hossenfelder for this excellent video and for presenting the startling assertions of Kerr's paper. Now I am waiting to hear what Dr. Becky may have to say on the matter.
@@ain92ru Since black holes are part of her specialized area in astrophysics I suspect she is well aware of Kerr's work and will comment on it when she is good and ready to do so.
Singularities are a mathematical construct, part of a theoretical model. It is likely that any model breaks down at extremes. I have always supposed that as the singularity is approached closely some other model takes over, a kind of phase change. Unless any observable consequences result from this, it is likely to remain a matter or speculation forever. If observable consequences are seen, then this could form the basis of advancing theory more deeply.
Exactly. I don't see what the big deal is. There are singularities all over physics, but nature always fixes things at the singularity. Even quantized vortices in superfluid helium have singularities at the center, but nothing bad happens. The density of helium goes to zero at the center to fix the problem with the 1/r and the multivalued phase at r=0.
@@ThePowerLover Anything with a 1/(r^n) blows up at r=0, but we don't run into problems with the many that we deal with all the time. It's only a problem inside black holes because we can't measure there and see how it's resolved.
@@ThePowerLoverwhy would you think the universe wouldn’t fix those, just like any other singularity? They only seem special because we can’t easily observe inside a black hole.
I love this video, because I never could get my head around ‘singularity’, and it makes black holes even more mysterious, and fascinating! I wonder if dark matter has something to do with what they are? Thank you, Sabine.
No matter what level of science or knowledge humans reach, even 100 million years from now, we will always be closer to knowing nothing than to knowing everything.
General Relativity predicts dilation, not singularities. Dark matter is dilated mass. In the 1939 journal "Annals of Mathematics" Einstein wrote - "The essential result of this investigation is a clear understanding as to why the Schwarzchild singularities (Schwarzchild was the first to raise the issue of General Relativity predicting singularities) do not exist in physical reality. Although the theory given here treats only clusters whose particles move along circular paths it does seem subject to reasonable doubt that more general cases will have analogous results. The Schwarzchild singularities do not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light." He was referring to the phenomenon of dilation (sometimes called gamma or y) mass that is dilated is smeared through spacetime relative to an outside observer. It's the phenomenon behind the phrase "mass becomes infinite at the speed of light". Time dilation is one aspect of dilation. General Relativity does not predict singularities when you factor in dilation. Dilation will occur wherever there is an astronomical quantity of mass because high mass means high momentum. Dilation is the original and correct explanation for why we cannot see light from the galactic center. It can be shown mathematically that the mass at the center of our own galaxy must be dilated. In other words that mass is all around us. This phenomenon does not occur in galaxies with very, very low mass because they do not have enough mass in their centers to achieve relativistic velocities. It has recently been confirmed in 5 very, very low mass galaxies to show no signs of dark matter. This is proof that dark matter is dilated mass. What we see in modern astronomy has been known since 1925. This is when the existence of galaxies was confirmed. It was clear that there should be an astronomical quantity of light emanating from our own galactic center. It wasn't until the 1960's that television and movies started to popularize black holes did they gradually become accepted. There was clarity in astronomy before idea of singularities took hold.
The normal non rotating black hole solution is also infinitely old. I kind of assumed that it was used mainly as a mathematically simple edge case for figuring out how to combine GR and QM, rather than a description of objects commonly found in nature.
I find your videos fascinating, even though much of the subject matter is well above my pay grade. As to hypothesising on backward time travel, I guess one cannot rule it out as long as causality is preserved.
Question: If mass/density directly affect the rate at which time passes. Why would a star core collapse to an infinitely dense point?. I hypothesise that at a certain treshold of mass/density, time completely stops for the object, thus preventing further collapse. Because if time doesn't pass at all, how can you expect the thing to keep collapsing indefinitely? So, beyond the event horizon, time has stopped, everything is frozen in place and in time, even light. Nothing can ever happen without the passage of time. But the mass is still there, it is still bending and warping the space and time around it.
If gravity is acceleration and leads to time dilation effects, doesn't it hold that a point with infinite density would therefor have infinite time dilation, and in effect, stop time? If so, then one would think that any massive object that is currently in the process of collapsing into a singularity would never actually complete the process, because, as its density increased exponentially, time would also slow exponentially... and as a result, blackholes would be objects that are forever collapsing into a singularity, but will never actually get there. Likewise, infalling objects would fall forever, but never actually reach the center. The universe, time, whatever... will end before the process ever completes.
If the infinity is only at 1 point, and all the other points around have finite values, this means the whole path there has finite length. And GR textbooks show how to compute this finite path and finite proper time to singularity.
@@thedeemon right, but that's from the perspective of the in-falling object, who's time isn't really effected from it's perspective. But from any outside observers perspective, the in-falling objects timeline gets stretched out at an exponential rate in relation to how close it gets to the singularity. From the outside observers perspective, it never actually forms a singularity in the first place. The in-falling objects perspective is entirely irrelevant because it's either behind the event horizon, or at the end of time, or whatever...
@@charliemopps4926 yep, that's how it looks for a static outside observer. I'm not sure why this apparent look is more relevant than the infalling one. After all, it's only a kind of "optical illusion" - once you start moving freely towards the BH, in your frame of reference objects can cross the horizon in finite time too. Perspective changes depending on how and where you move.
@@thedeemon but I'm questioning whether it really is an optical illusion. Saying it's an optical illusion suggests to me that there's a true "world clock" that exists coordinating all observers and that time dilation isn't actually really, but I don't think that's accurate.
@@dimitrispapadimitriou5622 oh ok. If that is true, i won’t be able to say. I am no physicist. However, it is evident that such singularity has to be a mis interpretation due to lack of information.
To me singularity never made sense. In my mind nothing says the matter would have to end up into the center. Even if black hole were mostly hollow beneath the event horizon, we wouldn't be able to tell it from outside, right?
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you could probe it with a quantum magnetic light gluons, but that's pretty hard
@@spacejunk2186 I don't think so. I'm betting that there's no space below it. I'd guess the entire interior is no more than a single plank width across, that gets stretched to the radii of the event horizon, and everything ends up sitting just above that horizon with no-where to fall, because it's already at plank density.
Yes, if all the matter is in a plank shell AT the horizon, I don't think we'd be able to easily distinguish that from a classical black hole at any significant distance. In principle you SHOULD be able to somehow probe that surface and determine that it is different, but you'd have to do so at an incredibly minute level I think? Alternatively, we might be able to detect the difference via gravitational waves from the collisions, if we knew what to look for. That's our only realistic way to actually observe BH behavior at the moment.
I mean if time stops past the event horizon from our perspective, does a singularity even fail or suceed to form? If a singularity is impossible in physics whilst potentially inevitable during black hole formation, then does it balance out if time stops relatively at the exact moment a singularity would be formed?
It's only a matter of perspective: for a static outside observer this whole region under the horizon is not part of their spacetime, it's in infinite future, no event there ever happened yet. But if you start to move freely towards the black hole, perspective changes, and now things do cross the horizon in finite time. So even if some things never happen for one observer, it doesn't quite mean they never happen at all.
There is no such thing as "time stopping". Time is what is measured by a clock and all identical clocks tick away at the same rate, everywhere, and under all circumstances of motion and orientation (by Local Position Invariance and Local Lorentz Invariance, respectively).
@@kylelochlann5053 time is relative though, like mentioned in the video; photons don't experience time. Muons that slam into our atmosphere to create northern lights are only able to reach the atmosphere before their half-life decays them away because of time dilation. Time dilates for those near supermassive black holes relative to those further away
@@terryflopycow2231 There's no slowing of time in time dilation and it's fundamental to relativity that all clocks tick at the same rate. In kinematic time dilation the world-line of the traveling clock is shorter than the world-time defined by the observer (obvious in any spacetime diagram). In the case of gravity a pair of synchronized clocks will show differences in elapsed proper time as the length along a world-line is a function of the metric, but there's no "time slowing".
“When someone tells you who they are, believe them”. I still think we aren’t taking the tell of black holes seriously enough. If the event horizon really is the “end of happening” on one side of the boundary, then you have to assume that light, really IS frozen for forever. Eternity becomes an instant, and it only ever falls in almost infinitely far into the future when the black hole evaporates. To Kerrs credit, I offer a quote on light by David Grandy: “to a photon, all of time is an instant, all of space, a point.” Follow that logic through when applied to a black hole and it really makes it feel like that instant stretches out for forever, and the universe only ever lets light press play on traversing it’s last leg the moment it becomes thermodynamically feasible for the black hole to evaporate. Two when’s at once.
Sabine, what is your analysis of Stephen Crothers repeated and varied 'take-downs' of GR and black hole mathematics? I've not been able to find any mathematical rebuttals, only personality attacks. It's been almost 20 years now...
nothing is escaping, time dilation is stretching everything out, a self contained infinity. Could already be another universe beginning in there as matter is somehow converted to space time. Easy to speculate when you can't see inside and the math says 🤷♂
Which, btw, is an interesting problem in and of itself. I've never been clear on why the universe at the start of the big bang wouldn't simply be instantly bounded by its own event horizon and never be seen again. I guess if you assume the entire universe is inside a geometric event horizon and everything we see is simply going on inside it then that's fine? I guess that 'inescapable direction' towards the 'singularity' described in black hole could simply be us moving forward on the axis of time towards an 'inescapable' future - we've just swapped an axis in space for an axis in time. It would certainly explain why we can't go backwards in time, only mess with its rate of forwards progress. :D
The difference is that black holes in our Universe form 1-dimentional universes inside, whith only one direction (to the singularity) while our Universe is 3-dimentional. It could be the black hole from another, multi-dimentional, Hyperuniverse.
@@Jesse_359 Imagine all of the matter in the universe was in a singularity with all that curved spacetime, then someone flipped the gravity switch off. That's what we see, but space is doing some weird expansion of it's own. Maybe at the point of the big bang space itself suddenly expanded faster than light and stretched the singularity apart until it was no longer a singularity. We know that space is the only thing which is permitted to expand faster than the speed of light. It would suck if the expansion of space is just a random value which periodically changes, and right now it's just moving to a higher value, but in the past it randomly went above C and caused the universe to begin by ripping energy right out of it's own vacuum state.
@@Boritis yeah the problem with those kind of nested universe ideas is that you're just pushing the creation of the universe into another realm without actually explaining anything about how it all began in that universe. It becomes a recursive loop like the chicken and the egg.
I always said we can't know if there is an actual singularity in a black hole. It's just that it's not like it makes a lot of difference. The point to note is that the matter going into a black hole is not disappearing out the other side since black holes of any significance are always increasing in size regardless of the amount of matter entering into them which is the reason for the vacuum of space. Whether or not they actually reach an actual singularity it doesn't really matter. There are lots of things that we can know such as how much gravity drops off outside of a galaxy and what effect does that have on the passing of time and the size of the measure of distance compared to where we are or compared to the area around a black hole.
@@dporangecountyWhat if their density and gravity forms an event horizon/ black hole? You cant´t differ a black hole with a singularity from one, that has a compact ,but not zero diameter object in the center. Anyhow, though I heard of these hypothetical quark stars, I heard nothing about which force could stabilze them from collapsing to zero.
"Every new beginning comes from some other beginning's end." _Closing Time_ - Semisonic So, curve-fitting works both ways, and instead of a curve ending at a singularity, it can just begin there?
I sat by Roy Kerr in Stockholm at his Crafoord Prize lecture. We got chatting, as fellow New Zealanders, like neighbours across the fence, nice man, and I remember him saying to me, something like, 'Those guys over there...they're making all this rubbish, we don't know anything'. I just nodded in respect.
@@SabineHossenfelder The other funny thing from that day was when I came into the theatre (early) and sat up front, two seats back (that is why Roy was in front of me) the only other person in there as Kip Thorne, sitting in the middle, same row, and I thought, okay, wow, me and Kip Thorne, cool. And he turned to me and asked: (and I will never forget this) "Do you have the time?". A physics joke, but it made me chuckle.
He sounds like the kind of Scientist who would fight like the devil if his theory was ever falsified. Doesn't sound like a particularly humble man to me. I admire humility above intelligence. But that's cos I ain't particularly intelligent. :)
This all seems very unsurprising to me, as what's described here has been my intuitive expectation of what would happen, ever since i gave it any real though. I always just assumed i didn't understand it properly, and I suspect I was right and I still don't. But nice if the intuitive turns out to be right.
Makes sense. Rotation can't occur if the radius is zero, and we know rotation of black holes is reality. Also, when mass is added to a black hole, the event horizon expands. This means that the object at the center became physically larger, or more dense, or both; and a singularity cannot do either of those things.
I feel this so much, but also question why i never quetioned this simple plot hole myself, why does it get larger, if it is infinetly dense? Makes me feel very dumb on a much deeper level. I think you do not need a singularity to fold space all into itself to create a still damn scary black hole. Bonus you do not break the laws of physics, or create a place were they are "different" i am all for this!
No, it's not. It's a well defined mathematical description of what happens if you apply known theories. If there's an event horizon, we don't know what happens inside it; mathematical theories are always going to be just a guess.
You can never remove a sigularity from a black hole, in terms of reference frames its only posible to have a singularity. Fist a Object enters the Event Horizon it interacts in 3 different refenence frames (inside,outside,object) in the outside frame you can interact with and observe the object, the moment the object is in the inner and outer frame at the same time everything breaks when a object is moved in any frame other then the Object Referrence Frame the object will break. Since a force can not be applied in referrence frames with different time constraints. The inner referrence frame can be, at any time, in the past, present or future at that point in space.
Singularities stopped making sense as soon as the observations of Black Holes started occurring. How can they they all have the same infinite center while being massively different sizes and some have fast spin, while some spin slower? The likely answer is that the central mass probably has as many variations as stars do, but it all occurs at the Planck length and at energy levels and magnetic fields we cant come close to replicating yet. Some of these "maths" look infinite when you plot a good chunk of their curve, but actually find a solution at an astronomical scale (no pun intended)
I also had the same thought by chance while taking a shower just now. The point with the strongest gravity on Earth is actually not at the center of the Earth, but rather in the region close to the crust. I suddenly thought, why do people all believe that black holes have singularities? And we know that the singularity of a black hole is an infinite future. Can matter reach an infinite future? Wouldn't it take an infinite amount of time for light to pass through (almost) infinitely compressed space? If that's the case, could a singularity be created?
Yes, in fact, some physicists have proposed that. I've been meaning to make a video about this, but in the end there wasn't much to say other than "some physicists think..."
@@SabineHossenfelderjust because absolute zero is considered not reachable does not mean that it doesn't exist... same applies to singularity state... come on with this crap...
@@SabineHossenfelderI mean let's just think about this for half a second of course everything is subjective because in order to have objective reality you need to have an observer that exists from the beginning of time all the way to the end of time and the end of time has not came yet so therefore everything is only subjective... with that in mind certainty cannot be achieved therefore Singularity cannot be achieved this does not mean that we scrap this most logical idea... clickbait bs...
As far as I know, CTCs are in the r < 0 region in the Kerr solution (below the Cauchy horizon), not between the horizons. (I might be wrong tho, the Kerr metric is complicated.)
Even using math when we can't physically experience and experiment we don't have definitive proof, I like this talk. And time and time the narrative has changed about the things we really can't experiment on.
It is embarrassing that this video has not had a follow up in the light of the rebuttals. Sabine has sunk a great deal in my estimation. Rebut the rebuttals or make some correction.
I never believed in the existence of singularities anyway, because they require matter within, quarks in particular, to change size and became zero in volume. I simply do not think that's a possibility.
I always thought 'proofs' were confined to mathematics or formal logic. If you follow the rules of the game the conclusions must follow from the premises. Once proven they cannot be disproven Science does not do 'proofs' because science is empirical, using inductive not deductive reasoning. Scientific theories are never 'settled' but always subject to modification or replacement in the event of further knowledge.
Kerr is like, "I wonder how long it will take them to notice this obvious mistake." 60 years passes. "Ok, ok, they are hopeless. Here's the answer, while I'm still here"
Yeah, pretty much this. At MIT in 1980, I remember asking a physics major whether, if it takes infinite sidereal time for matter to reach the event horizon, black holes can actually ever form from a practical perspective. He said he didn't know because MIT didn't teach relativity, just quantum mechanics.
Note that the mistake Kerr points out is not a mistake in the math, just in the interpretation.
If Kerr was confident his this theory over the last 60 years he'd have published a paper.
This does not prove that any of us were mentaly inadequate.
And why not? Both arguments are about the nature of a geometric concept.
What happens inside the space we call an Event Horizon will remain a mystery until someone goes into that special space and returns from that world to tell us what that heaven or hell was like.
So, to claim that Penrose and Hawking are sacardotes and the rest of us have sat ignorantly in the Space Time Cathedral only means the author still sits in Space-Time Cathedral praying for the absolute observed truth that lies on the other side of the veil with the rest of us.
Did Kerr look at the light skewing of the “white hole” (area/region before the event horizon of the black hole to pre amp universal operable light towards the black hole)???? Now how about the relativity of how we are able to observe the operable light coming from that region? And is there any hydrogen/ice/ bound gravitational lightwaves in heavy volume that are interacting along the way with that operable light volume we are able to detect and observe with the limitations of size and instrument baseline variable considerations not considered???? I think so unfortunately
Ask Brian Keating how volumes of hydrogen (in earths atmosphere as well as proximally in space) will polarize light, no matter the form of resonance for that hydrogen volume considered as well as gravitational waves as the wind in those volumes of hydrogen considered
I stumbled upon Kerr's article a bit on accident two weeks ago or so. I thought that if he's correct, then that would be an incredible realization in theoretical physics, and I wondered why I had almost seen nobody in the popular science space or media catching up to it. It's nice to see it's finally getting some attention.
Because the complication of that will be that the GR theory is actually absolutely ideal math but physically absolutely wrong. If we except that the GR is wrong, then the B.B. nonsense is wrong and there isn't a Universe's creation. No creation, then, isn't the need of a creator and the Vatican will disagree! Ha, ha, ha, ha. If the Vatican has a disagreement, then it will stop the gift and the money from the Vatican academy to the scientists! Then these scientists will have to work like Prof. Lerner in their garages!
Because like any group=think, they simply don't want it to be the truth or possible. Those who continue to insist the models are solid are doomed to be either disappointed by nearly everything or they will die before knowing how something really works.
@@catserver8577 Who is "they"? It's the lingo of a stupid conspiracy theorist.
If by "they" you mean "theoretical physicists", then that's a very dumb thing to say. Who wouldn't want to disprove something and make a groundbreaking discovery?
@@catserver8577 Galileo Galilei has told: The scientist, is this person which is questioning and rejects everything! No, place for dogmas in science, because everything is under motion and under change. For that reason Heisenberg, e very dialectical scientist, describe the uncertain principle! For the same reason, Einstein isn't a scientist because he wrote 3 dogmas in his papers which are refusing even his SR's theory.
@@lajoswinkler nah your comment is dumb one. You have no clue how bad status quo is/was especially in past in academia
Hi Sabine,
I love your channel and your videos. Unfortunately I must disagree on this one. I work on the problem of BH singularity and I need to say that it was very surprising to see this paper coming from someone like Kerr. My opinion (shared with everyone in the field I talked with) is that some of the statements are very well known, while the rest of the paper is incorrect. I’m particular, the main conclusion that Penrose theorem do not imply a curvature singularity is very well know. It is very clearly stated in the Hawking Ellis book. The technical reason is that Kerr geometry has a Cauchy horizon and Penrose paper only discusses globally hyperbolic spacetimes. The theorem only proves geodesic incompleteness. The reason why we believe the presence of singularities is not faith. It’s because there are a lot of result showing the instability of the Cauchy horizon (which seems to form a singularity) and because a stable Cauchy horizon would be much worse than a curvature singularity from the point of view of the well-posedness of the theory. Of course I realize that he is Kerr and this is just a random comment on youtube. But I hope that, if you read the comment, you’ll be curious enough to investigate the problem further!
Commenting on this so that she sees it. But also I thought that the divergence of the Kretschmann scalar also proved the existence of a singularity? And its ring-like etc? In super confused about this atm, but then again I haven’t done any GR in a couple of years.
Thank you. Geometric Spaces are emerging every 50 years since Hyperbolic Space.
Let me try to list them Euclidean Space, Gallelain Space, Newtonian Space, Poinicaire Space, Mobius Space, Space-Time, Wheeler Space, and now Kerr Space.
Those still are not enough descriptions of Space. Dark Matter, if it exists, could lie in a different Space.
It is nice to be alive. Every day is a wonderful dream.
Thank you 🙏
I'm not up to date on GR, but what do you think of this paper? arxiv.org/pdf/1710.01722.pdf
It claims to prove that Cauchy horizons can in fact be stable. It's over 200 pages long though, so I haven't actually read it.
This is an interesting point. By the Cauchy horizon, I assume you mean the one at the inner horizon of a Kerr black hole? Kerr argues in this new paper that the ring singularity could be replaced by some nonsingular, finite matter distribution within the inner horizon, but he didn't comment on how (or if) that would resolve any of the issues that occur on the inner horizon.
@@frede1905 Thanks for this clarification (need to read the paper). I guess since the Kerr singularity is two dimensional, we are free to patch it with a timelike four dimensional bagel or something. Anyone could’ve argued this though, so then the result isn’t surprising. In any case the whole Cauchy horizon question remains… I guess this is stuff we already knew, no one actually understands the interior of a Kerr black hole.
7 months later and Kerr's paper, on which this video is based on, still hasn't been published because it's bunk. That's the danger of latching onto sensationalistic pre-print papers which haven't been peer-reviewed.
This is exactly the kind of content and length I enjoy from you Sabine!
how bout girth?
What exciting days in physics, and what a pleasure to have Sabine to bring them close. Couldn't be better 🎉💚
It's not exciting when you have just much of BS flying around accepted as "facts". Kerr just had the credentials to be accepted by physics. Mathematicians have distanced them self from this crap already a long time ago.
I apologise for my dubious tone, but... what excitement exactly? We continually find the wrong answer, as this video even shows... is this really a time for self congratulation? Shouldn't we take a step back and ask where it is we went wrong?
@@KieranLeCam
Where it is we went wrong? Easy.. it’s called war.
@@KieranLeCam I figure it exciting that, following my perception, there is a moving in research again, after decades of stagnation, that SH described so accurate in her book 'Lost In Math'. Of course, you're right, it's a way of try and error, but that's how the scientific method works, no? Last decades, everyone just followed the mainstream scientific establishment. Just my thoughts.
@@KieranLeCam Another way to look at this -- we are continuing to update our understanding of the world. Science is a process of continual refinement of models and all models are limited (if a model was 100% accurate, it would just be the thing itself that is being modeled, rather than a model). Since Knowledge is probably infinite, we will always be updating our models -- we will always be wrong about something. You gotta get used to it. Being wrong about something is the first step towards being right about it.
Sabine, you need to reassess this topic in light of the rebuttal of Kerr’s claims, which are appearing currently.
any other source apart from that video on youtube? thanks
Having finished reading Kerr's recent paper, i think that the major problem with it is that ignores all developments that have been done in recent years about the instability phenomenon that occurs in the vicinity of the inner horizon of both Rotating and Charged Black Holes.
This "blueshift" instability was originally pointed out by Penrose himself for Reissner Nordstrom black holes ( that have an inner Cauchy horizon, similar to Kerr) and later was confirmed by the famous papers from Poisson et al : "Inner Horizon instability and mass inflation in black holes" -1989 & "Internal structure of Black Holes" ( Physical Review D-1990) where the phenomenon was dubbed " Mass Inflation Instability" and occurs both in Rotating and Charged Black Holes.
The consequences are :
- That the region *beyond* the inner Cauchy horizon ( where in the eternal Kerr solution there are no trapped surfaces - as it is stated in Kerr's paper)
*is not there* in physical Rotating Black Holes!
There's no smooth transition, because instead of a Cauchy horizon, a null singularity is developed there, or even a Spacelike singularity, depending on the details!
- What lies beyond the weak null singularity ( that replaces the inner horizon of the idealised vacuum Kerr solution, if there are slight perturbations from a matter field) is merely unknown. "Weak" solutions for the Einstein equation?
- In more realistic cases, a strong spacelike singularity appears, so there's no extension in that case...
In Kerr's paper there are neither references to the above mentioned Poisson et al papers, nor any references to subsequent papers that extensively investigated the instability ( e.g. by Ori et al, A. Hamilton, Dafermos et al, to mention only a few...).
@@CiaDora-us1tf please, re-read my comment.
A "stable core" cannot exist inside a black hole, rotating or not...
I've never believed in point singularities because, in that case, angular rotation rate would have to be infinite. On the other hand, a ring singularity can still have finite rotation rate. Plus, the fact that black holes appear to have polar jets goes well with the ring singularity view. A ring singularity leaves open the possibility that matter that enters exactly from above the North, or below the South pole might have a small chance of passing through the ring's center and appearing on the other side.
Aren't the Polar Jets just the effects of matter collisions close to the event horizon? Just hypothesizing. I'm a boilermaker/welder.
@@robguyatt9602 Polar jets are external to the event horizon yes, you can essentially have star core like conditions just outside the event horizon with enough infalling matter and the geometry of the accretion disk means the poles have vastly less matter to absorb the radiation produced hence; polar jets.
@@volentimeh Ah got ya. I had a thought. Do the jets go both away from as well as toward the centre of the black hole? I'm thinking they are just high energy collisions of matter with only two directions to go. That being into and away from. Obviously, we can only observe one of those directions. I also imagine matter remains matter in the normal sense for quite some distance toward the centre after crossing the event horizon. It must be quite a particle soup in there before whatever the end looks like. :)
Hey Sabine love your small bite size format but will you be posting an anthology of all the bites at the end of the week as before. It was one of my weekend highlights to enjoy over a nice morning coffee
I barely understand you, but I am glad there are such smart people like you. You give great presentations.
Vielen Dank Sabine! Kerr deserves the Noble Prize for this. So happy you gave him the attention he deserves. There is one additional thing Kerr has missed but thats on the physical interpretations side. Indeed what happens at the collapse of a BH is that space and time seem to be collapsing to zero, however since they are inversely related to energy and mass, what actually happens is that at the central ring the grid (defined in terms of energy and mass) actually grows!!! After all mass is inverse time (Penrose substitutes Plank E=hf into E=MC2 for this) so our galactic core actually increases in size (in terms of energy as the grid) as in spatial sense it decreases. And Heisenberg stresses the inverse relation between energy and space in dXdP>=h/2) . It also means we should see our galactic plane as an energy dominated grid, with again minor energy singularities in it (stars) in around which we have emergent and overlapping spacetime bubbles that make up our galactic spiral are. At area without stars (between the spiral arms) we don't have these emergent spacetime bubble ,so the spatial distance between outer galactic stars and the Milky Way core is actually less then we observe, and so are the absolute rotational speeds of outer galactic arms. This solves the strange rotational speed curves mystery hence no need for Dark Matter.....
I didn’t think any physicists thought black holes *actually* contained singularities. The “singularity” didn’t represent a physical object, but rather the limits of the math of general relativity.
That didn't seem to have prevented Penrose from getting a Nobel Prize for _Physics._ Still, for other reasons I didn't think they're physical, as well; fun thing, in my own theory (which, in case you wonder, has been submitted for publication) there doesn't seem to be any black-hole-like vacuum solution to the field equations, which is kinda cool - suggesting I don't even need to bother with convoluted interpretations of what happens near a point-mass.
I've seen enough lectures now that suggest that a fair number of physicists had talked themselves into it, they've certainly spent an *inordinate* amount of time trying to model physical behaviors below the EH.
@@thstroyur I know you'll be hesitant to divulge details of your theory until it's published, as am I with my own, but could you give a vague hint?
@@thstroyur "there doesn't seem to be any black-hole-like vacuum solution to the field equations"
So the Schwarzschild solution and the Kerr solution are not "black-hole-like"? Or don't you count those as "vacuum solutions"?
Quite the opposite - there does not seem to be any way whatsoever to remove the singularity as they're defined (the singularity theorems) where the gravitational field is well-enough understood and obeys reasonable energy conditions. Even is string theory there are singularities that appear necessary to keep the vacuum stable. The expectation is more that some quantum theory of the gravitational field will resolve the singularity, i.e. perhaps remove the divergence of the curvature invariants or give some meaning to them that's sensible.
I come here to hear about things that I don't have a full grasp of or even unaware about. It makes me not stale!
Have you had your coffee already? Lots'a love, cheers, & Mabuhay, from tropical Philippines!
Nothing makes me sadder that knowing given my circumstances there was no way for me to become a physicist and live out a decent life at the same time(I dont live in a first world country). I must say when I'm older and have finished my live's goals I might consider just taking a dive into physics just to understand it.
I'm an old fart and do live in the first world. My limitation is my academic ability. I became a welder after high school. But I frequented the local library for all things science and now use the internet to quench my thirst for knowledge.
@@robguyatt9602 ❤
You and me brother. I hope we can make it eventually, I wish you the best
What country do you live in if you don't mind me asking.
Since it appears you know English well, then you could've become an international student at the many universities that have instruction in English. Many in Europe have free tuition and there are also scholarships in the US as well.
@@robguyatt9602academic ability or opportunity? For instance simple particle in a box, with infinite potential well you ca do with maths at school, the 17 18 year level stuff. After that it is time a determination. There the path is long and gradual but not impossible. And you are never too late
1:35 "or so we thought" - but many physicists _over many years_ have pointed out that mathematical singularities are not physical things. (Which Sabine _briefly_ mentioned a bit later.)
Yes but there is a big difference between "Singularities are math artifacts, not reality, so we are looking for new physics to explain what is missing from the math that explains why the black hole singularity doesn't exist.". And Kerr saying, "The original math had an error, and thus the singularity never truly appeared in the math in the first place."
The real question is why Hawking was on Epstein Island.
I want an answer to that.
I think he was checking out some 'brown' holes ....
You need an answer yet you ask on a random video of the internet where nobody would hear. Remember back then when trump was government and everyone was burning cities? Don't you think this is city burning worthy?
You make a great, compelling argument, either way. Good job.
To me, math is a tool for approximating whats happening in reality but never a description of reality itself and I have always been frustrated how people seem to get those mixed up.
Fascinating! Thanks, Sabine!!! 😊
Stay safe there with your family! 🖖😊
And happy holidays!
5:03
As many have pointed out, including Sabine herself, I think, numerical methods are not good enough when it comes to ultra small scales and/or extra large densities.
Yep. Perhaps we'll invoke "magic".
I was taught that the math[s] show a singularity, but in reality, nobody can know. But that was long ago, and perhaps some day we _will_ know, for sure. "Singularity" is such a beautiful concept, that I want to believe!
Now all the latest videos are awesome,short and to the point 😊
Well this question is suddenly relevant
Yes. Wonder what he was on Epstein Island for...
Checking out brown holes ...
I was always confused why the larger scientific community thought black holes have a singularity in them. I had always thought a slightly more compact neutron star was at the center of black holes, possibly with the surface right underneath the event horizon. Physically, that makes more sense than a single point with all the matter condensed down to that one point.
Same. I feel the scientific community sensationalized BHs and went off the deep end in their portrayal of them.
What would stop those neutron stars within the event horizon from collapsing ever further?
@@damianich4824 Watch Science Asylums videos on black holes, he explains it
The problem with that view is that, above a certain mass, the neutron star isn't stable and continues to contract, apparently without limit.
From what I understand, the black hole singularity forms precisely when something like a neutron star reaches a point where gravitational interactions overpower the nuclear interactions, leading to a shrinking in size and increase in density as the star collapses. At that point, our current models of physics and math sort of break, but that doesn't necessarily mean it doesn't exist. It's like fluid dynamics, we don't have a formula to fully describe it, yet we can observe it in action and make some predictions, even if not 100% accurate
Kerr's paper and arguments seems to have flat-lined. At least with leading general relativists. According to them, it's just rookie mistake from a veteran! Sorry Sabine!
I spoken with Roy Kerr about this a few times and shared our conversation with other relativists and between us we've concluded that he's blatantly wrong, but we've also concluded that Roy Kerr is Roy Kerr and we're not, so maybe we're wrong. Anyway, the gist of our reasoning was (is) as follows...
What he's calculated is for a pair of NPVs that asymptote on the inner horizon (infinite in geodesic length) with a finite value for some choice of the affine parameter. What we find bizarre is that this is exactly what defines a singularity, so it seems he seems to have demonstrated there's a singularity, and then uses this to say that there isn't one. For the sake of example, in Schwarzschild we can take two rocks and drop them across the horizon (over the same radial line) and show that the proper distance between the two (the geodesic length) goes to infinity, but, we can show that for each of them the elapsed proper time (the typical affine parameter along a world-line) is finite. I don't even think Roy Kerr is arguing there's no singularity in the Schwarzschild geometry.
Part of me wonders if this paper will garner much interest as Kerr is working in the original Kerr-Schild coordinates as he envisioned it all in the 1960s and we've come along way since then and current research is in more realistic (e.g. perturbed Kerr geometry) physics in which there's multiple singularities (mass inflation, BKL, null) and often requiring numerical methods to solve hard numerical problems. Additionally, in few conversations over the past couple of years there is a clear and deep animosity towards Roger Penrose, Hawking, and others. This too has us wondering if decades of festering animosity left his math skills intact but left his objectivity in question.
This wouldn't be the first time that an eminent scientist in their 80s makes a confident and wrong declaration that for years, their field has been on the wrong track
I'm still an undergrad so I may be (probably will be) wrong on this one
Isn't Kerr's argument that, null geodesics terminating at finite affine parameter doesn't always mean that there is a singularity?
His example of a geodesic between the two horizons couldn't have approached a singularity since the singularity in the Kerr metric appears strictly inside the inner horizon, right?
@@ricksonwielian3548 In the analytic continuation the ring singularity is indeed interior to the inner horizon, but in the perturbative analysis there's a singularity at the inner horizon, the mass inflation singularity. Roy Kerr seems to picked up from where he left off in 1963 and is not making arguments for/against subsequent work.
Yes, he's making a claim that he's getting a null curve with finite affine parameter and stating this means there's no singularity, which is incoherent (at least to myself and everyone I've spoken to as a finite affine parameter is what we mean by a singularity). We're not sure if he means that the curvature invariants, e.g. Kretschmann don't diverge upon the limit of the affine parameter or if he's found a solution with a quasi-regular singularity or what, nobody seems to know.
Indeed, Kerr only speaks about curvature singularities, or alternatively points where the metric loses its required differentiability - he clarifies this usage of the word "singularity" at the beginning of the paper. I agree that Penrose's theorem most definitely proves that black hole spacetimes are singular in some broad sense - as per the definition that spacetimes are singular if they are null or timelike geodesically incomplete. But wouldn't it be significant if black holes do not have to contain curvature singularities or points where the metric loses its required smoothness/differentiability? Don't most relativists imagine that black holes contain that kind of singularity, not just merely that spacetime is singular in some broad sense? Although I found it interesting that he didn't discuss the problems that occur on the inner horizon of a Kerr black hole, whether a black hole without this kind of singularity would be stable etc. as you pointed out.
“We don’t know of any force that could prevent it from completely collapsing.” What about the Pauli Exclusion Principle?
The Pauli Exclusion Principle applies to fermions, but not bosons. At some stage in the 'crushing down' process, the fundamental particles will be forced to decay into bosons, which can occupy the same point in space. I think most people would agree that the singularity, if one exists, is a 'container' of energy, not matter. I am not suggesting that the singularity is just a vast number of bosons all concentrated at a single point in space, I am suggesting that the conversion to bosons is a phase that the infalling matter goes through, before being converted into some very exotic form of energy, as might be described by string theory.
@@richardconway6425 That’s really interesting, and I’m surprised I’ve never read or heard any physicist talk about that decay process before. It seems like it would be really important when talking about what might be inside a black hole. Do you have any links to sources where I could read more?
@@DaHuuudge ha, no ! Sorry I don't. My explanation is based on my understanding of physics, and not on any particular theory or paper. Funnily enough, I have never heard any physicist talking about his either, and that's most likely because any discussion on the likely nature of the singularity, and the 'crushing down' phase of the infalling matter is highly speculative. Physicists tend to be quite reluctant to speculate on matters such as these, at least in public, because they are afraid of talking about things for which there is no known physics, and equally, they are afraid of reputational damage to their credibility as a respected scientist. They are afraid that other scientists may think them 'unscientific', which is the polite way of saying 'fanciful', or worse 'superstitious'.
It is interesting that Stephen Hawking essentially built his reputation as a world leading theoretical phycist by investigating this very difficult subject, and writing his paper on black hole radiation. His theory was built on a very creative approach - he considered both the effects of quantum mechanics, and general relativity, and, with a bit of clever maths, came up with a way of describing what happens around the 'singularity'. He and Roger Penrose had already collaborated on a previous paper, that proved mathematically that a singularity must exist at the centre of a black hole (I believe they considered the simplest case, that of a Schwarzschild black hole), so there was no doubt in his mind that one must exist. He came up with a way of describing how the quantum fields of QFT were somehow destabilised and perturbed in the near infinite curvature of spacetime around the singularity. This somehow produced the very unexpected effect of causing black body radiation from the event horizon of the black hole, at a temperature of 2.7 K.
Leonard Susskind described it as 'brilliant', and said he thought the maths was 'watertight'. The physics community seems to have accepted it, which I actually find quite surprising. The theory seems to me to be potentially flawed for the following reasons:
Stephen Hawking used quantum mechanics to build his theory, unfortunately the prediction it makes fatally undermines one of the sacred cornerstones of QM itself, that is, the principle of conservation of information. This is not a good start. This problem can be mitigated, but only if you accept another, incredible theory, that of the 'Bekenstein Bound', and the 'information theory' of black holes. This seems to suggest that all the quantum mechanical 'information' that fell into a black hole, is now somehow perfectly smeared out over the event horizon at the Planck scale. This means that outgoing Hawking radiation can somehow 'take' this information with it, resolving this loss of information problem.
It's safe to say that this is all quite speculative.
The second problem with the theory is that it is untestable, or 'unfalsifiable', as scientists like to say. This is a very important concept in physics, and is sometimes used as the litmus test of a theory. If it's unfalsifiable, then it's not terribly useful as a theory, because none of its predictions can ever be tested. It's not that the theory is necessarily wrong, it just can't be tested one way or another, meaning we'll never know whether it's actually true or not. Some physicists will even go as far as to say that this makes it a 'bad' theory, although many would not agree with that.
One of the reasons why Einstein's GR was such a good theory, was because it made many predictions which could be tested, some to great precision. The predictions it made did not require experiments proscribed by the laws of nature - the people who understood it knew that it was just a matter of time and technology before it could be tested. Space rockets, lasers, atomic clocks, massive optical and radio telescopes, those were the things that were going to make it possible, and people were already anticipating those things.
However, Hawking's theory of black hole radiation may never be tested, because the surface temperature it predicts for the only type of black holes we can actually see, is significantly less than that of the cosmic microwave background. If it existed, it would simply be drowned out by the white noise of the cmb. A signal to noise impossibility.
I digress. What I have been trying to illustrate, is that any discussion of what happens at the singularity is not only completely speculative, but it is clearly untestable. It is difficult enough to 'observe' the event horizon of a black hole, but getting any information 'back' from the singularity is clearly proscribed by nature. Everything beyond the event horizon is causally disconnected from the rest of the universe. Forever.
We do have physics that describes very well the process of stellar collapse into neutron stars, which are the most extreme astrophysical objects we know of. Physicists are reluctant nowadays to even use the word 'object' to describe a black hole, such is their reluctance to commit themselves to anything for which they could later be dismissed, intellectually speaking.
The Chandrasekhar limit describes how the electron degeneracy limit determines the point at which a white dwarf, for example, will collapse into a neutron star. It's entirely dependant on its mass, which in turn determines it's own gravitational field, which determines the forces involved trying to squeeze together it's matter. (There's a really good youtube channel called 'physics explained' which goes through the principles and math of this). Turns out to be 1.4 solar masses.
A neutron star can only withstand so much pressure. Again it's mass dependent. There's the idea of a 'neutron degeneracy limit', you can only force them together so much, before they too yield, and dissolve into an ultra hot quark-gluon plasma. That's the densest form of matter that we are sure exists, and interestingly, it's thought that our early universe went through a phase when all of its spacetime was filled with this ultra energetic and dense medium.
But of course, I understand, you want to know what happens when a neutron star collapses into a black hole. What happens to all of the trillions of tonnes of matter that rushes headlong to the centre, in an exponentially increasing gravitational field. It's own inward movement fuels the gravitational field - it is essentially creating it's own trap, as it becomes more and more crushed, more and more dense. It very quickly becomes a mathematical certainty that it will all end up in an impossibly tiny, deep, gravitational well.
It's so difficult to understand, or even imagine what happens to the infalling matter, as it makes its journey to the singularity. Stephen Hawking described mathematically the environment in the immediate vicinity of the singularity, but not the singularity itself. It's just not possible.
The best idea, or description, that I ever heard, was that it was a concentration of a vast amount of energy, in some very exotic form, smeared around in a tiny region of spacetime, that had a kind of indeterminacy in its location, according to quantum mechanics. But this is still all at the planck scale, so it's a distinction that will only be really appreciated by physicists.
My original response to your comment was based on the idea that the fermions being drawn together at very high energies and pressures must, at some point, decay into bosons, or boson like 'particles ', because, as you so rightly pointed out, the PEP would not allow the superposition of even just two fermions. But our current understanding says that quarks and electrons are fundamental particles, they cannot be dismantled into anything else, except for the fact that this 'crush down' is happening in such extreme conditions, at such high energies, we don't actually know what would happen to fermions in these conditions. This seems to me to be a particle physics problem, so I would be very surprised if the Large Hadron Collider could not offer some information. I think this is probably where you should look for further information on this. Their collider spends most of its time smashing protons together. Since each proton is comprised of 3 quarks, perhaps they see some of the decay products when quarks get 'annihilated', and perhaps some of those are bosons. One interesting thing about fermions, is that sometimes they can pair up, then behave like bosons. An example of this would be superconductivity, where, at very low temperatures, electrons pair up and behave like a boson (single electrons have an integer spin value of one half, put two together, and they acquire an integer spin of 1. This then makes them a boson). This is already looking a bit more approachable, I am definitely going to look this up, so thank you for your question.
People often don't realize that there are many different kinds of singularities and tend to conflate them very often. Please check any of Jose Senovilla's review papers on this topic (or videos on RUclips - they are very detailed).
For example, the curvature singularity as measured by, say, the divergence of the Kretschmann scalar is not the same as the singularity through which we cannot extend curves (Penrose-Hawking singularity). Actually, Penrose-Hawking theorems are non-constructive proofs, so we actually don't know where these singularities really are (although where else, if not where the Kretschmann diverges? - still, not a proof). Some people say, that Penrose-Hawking singularity theorems should be called manifold completeness theorems because this is how mathematicians call them when they study purely Riemannian manifolds (i.e. purely spacelike manifolds). The singularity name was attached because the sudden (dis)appearance of a physical particle would mean something serious, so "singularity" in this case stands for something strange and serious happening, not an explosion or divergence of some value.
I have listened to most of the talks of Prof. Kerr on RUclips, and from what I remember, his argument rests upon the exact solutions being just idealizations with unphysical properties. Kerr black hole also has them, for example, the inner horizon is known as the Cauchy horizon and is highly unstable against perturbations. Another observation is that many singularities in reality are not singularities, because any pair of particles usually have a net non-zero angular momentum and hence create a bubble around themselves like in Kerr's case. One of his idealized proposed solutions was an almost infinite sequence of black holes within each other separated by layers of normally behaving spacetime, but this has never been developed to the full extent.
Of course, most scientists do not believe that there is actual singularity because quantum effects are supposed to solve that, while now it seems that even classically this may not actually be a problem, but then we need to find an even better solution, and it would need to be evolving in time, so almost impossible to discover analytically.
The fact that there is scientific conversation about this is what matters.
Thank you! Absolutely fascinating.
I love these short videos on a single paper.
I like Kerr’s argument. Once a thing pass the event horizon, it will keep speed of light to maintain its angular momentum. In order to fall inner, speed of light needs to be faster inside the black hole yet the angular momentum will still maintain and prevent it from falling further. So it should be fully empty inside.
I am total novice, but I thought is it possible that the spacetime is quite condensed yet not collapsing into a singularity. And maybe this condensed spacetime stabilizes heavier quark top quarks or maybe something beyond that decaying in ridiculously fast time frames we might not measure yet.
This is analogous to neutron stars who condensed matter yet not beyond an event horizon.
Wait. You can’t just rotate a drawing of a back hole and see a dot from the “back” of it. Surely. (?) We struggle with this stuff for the same reasons you cannot just draw it. You can kinda draw a vortex like that, but in a black hole, as I understand you so far, the vortex looks the same from ALL points of view outside the event horizon. If I’ve got a bad assumption in here, please do a video to explain. (Bonus: I don’t think your drawing of “singularity” can be a good representation of that discussion either. The lines never converge. It’s an asymptote. Surely nobody ever drew the lines like in this video… (or cite one please?)
Thanks for explaining this. I've always had a problem accepting this. How can all that matter be compressed to a singularity?
Nice to see Albert back 👍
when you have the rotating cyclone of time quarcks they make bridges between the past and present, and are in some way outside of the space and can expand infinitely into a singurarity.
@ Or so one theory says. I find this highly improbable. Math is a model. But has this story points out, that model is up for interpretation. It still seems more likely that the reality of blackholes has far more variables than we are aware of and that information would explain its existence without the need for something that forces you to divide by 0 - a technical impossibility.
I was also very doubtful about singularities. But I'm just an aerospace engineer with love of physics. Who am I to judge things. That might have been part of the problem, when you have juggernauts like Hawkins and Penrose, a lot of people probably never fully committed to attempting to prove them wrong. I hope this leads to some cool new science and mathematical models for our universe :)
Well, what it does say is that there must be something weird, it just may be a different weird thing than a singularity
She said this doesn't prove black holes aren't singularities, just that the theory that claimed to prove it was wrong. It's easy to see how matter can be compressed to smallness when you realize that: A. Matter is mostly empty space; B, It might just be a mathematical construct; C, it's just like, all a simulation, man.
One thing I've always pondered is whether a singularity can technically ever form. According to (my understanding of) general relativity, time moves relatively slower when you're close to a gravitational source. That means that for an object falling into a black hole, the closer it gets to the singulairty, the faster time moves outside of the event horizon.
If that's the case then can an object falling into a black hole ever techincally reach the singularity? The closer it gets, the faster time moves outside of the event horizon. Since black holes evaporate - albeit over a very long time period - the black hole will evaporate to the point where it's no longer a black hole, i.e. it will evaporate before any object hits the singularity. Thus no object can hit the singularity and thus no singularity actually exists.
I first thought about this problem when I heard the following (slightly flippant) phrase many years ago: "if you fall into the center of a black hole then by the time you hit the center, the universe has ended".
The reason why I thought of this in the context of the video is that there's some sort of asymptotic behaviour implied in the new paper. The above "argument" would lead to asymptotic behaviour, but only until a point. When the black hole evaporates enough then that asymptotic behaviour would stop.
Anyway, if there are any GR experts here then I'd love to hear responses to the above argument. My guess is that the argument is invalid because my understanding of GR is too superficial.
Actually, it's probably the opposite, all the matter should be at the limit of the event horizon, for it would take an infinite amount of time for it to move an infinitesimal distance towards the center.
@@joseislanio8910 that would also make sense. But either way, doesn't that imply there's no singularity?
I'm lead to believe any object will fall towards the singularity at light speed maximum. And when you're at that speed, time doesn't count. Well, at least for photons, I'm not sure baryonic matter would behave the same way
Okay i got lectured twice within 6 minutes. First i didn't even know of the Hawking Penrose Theorem, i thought it was mainly accepted that singularities do not exist and are just mathematical artifacts. Now i learned about the curve argument and why it might no longer a valid argument anymore.
Well, it _is_ mainly accepted that singularities probably don't exist - as Sabine mentioned later, most physicists think that effects of quantum gravity prevent them.
There's no room for 'faith' in science - leave that for the people with the invisible friend.
Being invisible isn't the same as not existing, friend.
yer faith in gandalf, his pink magician bastard and his assassin uncle is... indicative of trauma in your life, get help, don't smear your delusions on other people.
@@mareksgv "But there is no truth" Hmm - is that true?
@@mareksgv Only for those of vain epistemology; it's been said before: the map isn't the territory. This is much closer to the heart of your ouroboros theory. Doing science is OK - turning it into an idol (scientism) isn't.
@@mareksgv The very fact that truth does truly exist means that there is a right and a wrong answer to the universe. One can be wrong and another right, or both can be wrong, but both cannot be right is a simple part of reasoning. If they counteract each other of course.
The main issue with science today is not that science can't be done well or accurately. It also isn't a problem of us not knowing and making new ideas and theories, that is fine. It is that many scientists remove philosophy/theology from science as if it can't answer what is true or false. Science cannot answer many things in our universe, such as the value of man, morals, why math works, or even what is infinite for everything we see has a beginning. We see these laws of the universe but fail to ask the question where the laws come from, if they had a beginning or not.
In the end the question, "Does truth exist?" is an amazing question. If you answer no then your answer can't be true or false, but it is made as a true statement and thus nullifies its own answer. This is a question that can be answered with reasoning, but not science. There is much more to this world than just physical properties and the denial of that is very dangerous.
I believe in the God of the Bible. Whether you believe it doesn't make rational sense is definitely up to you. Evidence to me points to Him as the more likely answer. I also believe if you truly search and want to know the answer, He will reveal Himself to you and give the gift of faith.
Have a blessed day!
He checked all the underage girls, and he was wrong.
I definitely prefer this format for your Science News bits. It feels like you are managing to give each topic more time and a better degree of presentation.
Kerrs paper is not mathematical correct, Sabine
Got proof?
Kerrs paper from 15. November 2023 is not peer reviewed and many Physicists argue that Kerr confuses time and affined time and therefore Kerr does not get the math right.
ruclips.net/video/foq4nVAwEao/видео.htmlsi=uIZRv3krMJCjn7Oe
What's the difference? One says the point is infinitely far the other says it's not infinitely away but it takes infinite time to reach it
Out-freaking-standing, Sabine!!! As usual. In that I’m also including your statement “including myself”. Too many times egos get in the way of solid science - or most other human endeavors for that “matter”. (Sorry, poor pun, but I couldn’t resist)
Yes... but the "so what" at the end kind of undermines that humility...
@@KieranLeCam How? She mentioned she didn't see the mistake, but then also discusses it's implications. "There what?" is the next question of ANY new information.
That's not excusing herself. It's the next logical question.
. I believe although that the ego problem in science goes two way around: what it is the big deal with being wrong? data (and math in this case) allows only a limited interpretation of nature, and even if it is self-consistent, no wonder old theories gets revisited/refuted in the future. If efforts should be made to get rid of our egos to move forward, the community should do the same in not assigning such negative value to someone being wrong (i feel Sabine does poorly here, for such beautiful content she creates). Perhaps what is really wrong, is having no data (or worse, ignoring it) and take decisions in detriment of humanity, as we are so used to see nowadays.
Being wrong and reformulating our ideas accordingly, is I think, one of most beautiful aspects of science
@@robertbeste Well, I suppose we'll see if Sabine comes up with any new science, and that will tell us if she was being logical, or overly confident.
@@pansito_1 I agree with you. And science does allow for the possibility of being wrong, but I personally think it has become a very unimaginative endeavour. Being wrong isn't the issue, it's not learning from your mistakes that is. And science refuses to acknowledge the stagnation of progress in the explanatory power of our best theories, instead relying on the defence of the method itself, and using the concept of failure to justify continuing.
Sabine mentions this herself with some physicists wanting ever larger particle colliders using the justification that it isn't their idea that is wrong, but the energies of what they're looking for that are too high to detect. I'm surprised Sabine, Arvin Ash, PBS Space Time, Anton Petrov, and many other science communicators aren't reporting a mass existential crisis in physics circles at never being good enough to find the answer to the deepest mysteries of the universe.
Instead to avoid feeling uncomfortable, more often than not, physicists perform a mental gymnastics where they view themselves as both competent, because they understand some things, and humble, because the universe is just too darn difficult to understand. This is just like with the supercolliders, they are avoiding feeling bad about themselves by not putting into question their ideas, and methodologies, and the type of attitude they bring to the table, and putting the blame on the universe. That way they get to keep viewing themselves as experts, and intelligent, and they never need to feel the discomfort of having to change themselves. It's quite surprising to witness.
I've never seen a physicist (despite a strong desire to not give up), be upset because we just seem to be stuck. It's like we're not stuck at all. It's just how science works they will say. Well, I think it's time to put ourselves into question. Because we're just not seeing the results.
Excellent show as usual 👏 👌
To spin requires the black hole to occupy space as we understand and interact with. If they warp spacetime sufficiently, isn't it possible that are in fact _not_ spinning despite the conservation of angular momentum?
I have always wondered how a singularity could be said to rotate. For something to rotate, it must have a physical dimension that moves around the rotational axis.
@@henrikkowalski3144 To further exemplify the lack of an classical analog, the math says that an electron must spin _720_ degrees to return to its initial state. Electrons are just weird.
@@maxweber06 That's not weird. Take "any" 4 stroke internal combustion engine. The camshaft that actuates the valves rotates at half of the crank speed. That means you have to rotate the crank twice for the engine to return to the state you started. Nothing magical about it.
Black holes are based on a mathematical misconception. Most people don't know that Einstein said that singularities are not possible. In the 1939 journal "Annals of Mathematics" he wrote -
"The essential result of this investigation is a clear understanding as to why the Schwarzchild singularities (Schwarzchild was the first to raise the issue of General Relativity predicting singularities) do not exist in physical reality. Although the theory given here treats only clusters (star clusters) whose particles move along circular paths it does seem subject to reasonable doubt that more general cases will have analogous results. The Schwarzchild singularities do not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light."
He was referring to the phenomenon of dilation (sometimes called gamma or y) mass that is dilated is smeared through spacetime relative to an outside observer. It's the phenomenon behind the phrase "mass becomes infinite at the speed of light". Time dilation is one aspect of dilation.
Dilation will occur wherever there is an astronomical quantity of mass because high mass means high momentum. There is no place in the universe where mass is more concentrated than at the center of a galaxy. Dilation is the original and correct explanation for why we cannot see light from the galactic center.
It can be shown mathematically that dilation is occurring in our own galactic center. In other words that mass is all around us. Sound familiar? This is the explanation for dark matter, the missing mass is dilated mass.
Einstein wrote about dilation occurring in "large clusters of stars" which is basically a very low mass galaxy. For a galaxy to have no/low dilation it must have very, very low mass (or low mass in its center). It has recently been confirmed in 5 very, very low mass galaxies to show no signs of dark matter. For the same reason binary stars will always have predictable rotation rates.
What we see in modern astronomy has been known since 1925. This is when the existence of galaxies was confirmed. It was clear that there should be an astronomical quantity of light emanating from our own galactic center. It wasn't until the 1960's when television and movies started to popularize black holes did the concept slowly became mainstream.
The question I'd ask is: is there any reason why a neutron star which acquires mass until the escape velocity at its surface exceeds c simply causing it to wink out of view should undergo any further compression/shrinkage? Is there any hard requirement that matter should necessarily be compressed beyond neutron star density?
I'm just a filthy layman, but I think it's related to the whole; "Only things that have 0 mass can travel at C" thing. It's not so much the mass that's collapsing, it's reaching a tipping point where the whole (or part of the whole) thing is converted to energy; ie photons (which still affect gravity) Photons have that whole particle-wave thing going on so they can occupy the same "point" of seething near impossibly hot energy.
Another filthy layman, and probably a stupid question, but with the mass collapsing to the point where light cannot escape, and an event horizon is created, the closer Alice, Bob or whoever approach the event horizon relativistic effects increase the speed of time for the rest of the universe for Alice, Bob, whoever. This means that although time appears normal to them, effectively time stops when the event horizon is reached. So the person in question never actually reaches the event horizon. My point being, how does matter continue to collapse when time has effectively stopped? Therefore a singularity cannot exist in the black hole, it is simply a neutron star with gravity so strong that the light cannot escape. Please excuse this 'duh' question, but it has bothered me for a long time.
@@GeorgesDupont-do8peArvin Ash recent video of entering a black hole (big enough to not rip appart) , Said the person continue entering inside after event horizon normally . Observation from outside see the last image frozen as after that , no more light of that person comes. But also is strange where that frozen image have energy to be shown, without the person there...
Thank you for your response @RF-fi2pt. To add to my point, it seems that as time stops at the event horizon, the said person will never actually pass the event horizon and all the matter would completely fill the black hole up until the event horizon. Furthermore, as according to Professor Hawking, eventually the black hole will dissipate or explode due to Hawking radiation (eventually). Thus, it seems to me, poor know nothing that I am, that from the point of view of the black hole, the matter collapses until the event horizon is reached, and then immediately (as time has stopped at the event horizon) the black hole explodes/dissipates/whatever it does. Immediately from the point of the black hole that is. For space time 'unaffected' by the black hole, billions of years will have passed. Thus, from the black hole's point of view, it merely 'bounces' from collapse to whatever the final result is. Thus, no singularity just a very long time for everywhere else. Gives me a headache, wish I'd studied astrophysics.
I've been talking about this for a while. A singularity? Infinite density? NOPE! There is *no such thing* as infinite density or in fact infinite *anything* in the real world.
🧂
I mean, is there a practical difference between infinity and a number with so many 0's after it that it breaks equations just as badly?
Stephen Hawking was just a complete idiot. - Discoverer of extraterrestrials on 01.17.1995 Johann Zdebor
Ein Kurs über Topologie und Relativitätstheorie wäre toll.
I've always wondered if there are black holes not massive enough for a singularity but still enough so for an event horizon, I wonder what the effects would be if a blackhole crossed that threshold
According to GR, size doesn't matter, even smallest black holes have the same structure.
You cant have one without the other. An event horizon isn't a physical thing, it's just the point at which you can no longer escape the black hole.
I wonder if that depends on the definition of a singularity. Does it merely need to be singular, or must it have no size in any dimension, and can it have a size but still be singular if space-time dimensions become meaningless near it.
@@bipolarminddroppings Not necessarily true. A singularity implies infinite curvature of space-time; an event horizon only needs the curvature to be above a certain limit. At the moment we don't know what mechanism could stop matter collapsing once the strong force is overcome in a neutron star accreting material, but that doesn't mean that there isn't something.
@@jakeaurod In Kerr's solution black hole's singularity is not a point but a ring of finite size. (zero thickness though)
I read a book 30 years ago about super extreme Kerr objects (SEKO).
Frankly, I didn't really understand much of it, but I was convinced of the existence of black holes.
Thanks, Kerr.
I'm not going to lie, I don't understand much of this but the great thing is that Sabine is a principled scientist and so are the other characters in this episode of science history in the making. When the resolution of the questions raised here becomes available it'll be posted here.
Stephen Hawking was just a complete idiot. - Discoverer of extraterrestrials on 01.17.1995 Johann Zdebor
I thought the energy required to move objects with increasing mass is what set the limit for how fast an object could move thru space (as that velocity would translate into a resistance). There would be no way to maintain spin as the event horizon is theoretically moving at the speed of light (so via frame dragging, any surface of a "dark star" would be grabbed by this mass; though between the event horizon and the surface, that "space" would consist of layers of twisted time, like the windings of a spring). *movement of black holes may even fall outside of gravitational physics, with their movement thru space based on some other property that allows information to travel faster than light, and binds all black holes together in a quasi-gravitational manner.
i'm a mathematician, not a physicist, and i haven't read the paper, but this seems like such an amateur mistake by penrose and hawking that i would more readily believe an 89 year-old kerr misunderstood their argument than that this mistake was actually made and overlooked for 60 years.
Never ever underestimate the capability of physicists those days to make stuff up. If they came up with the singularity stuff 20 years later they would almost certainly have named it "dark space".
There's no mistake in the theorems by Penrose and Hawking - they prove what they claim to prove. It seems that what Kerr tries to argue is something against the interpretation of the theorem. The theorem by Penrose essentially proves that black hole spacetimes must be null geodesically incomplete, and Hawking and Penrose defines a spacetime to be singular if it is timelike or null geodesically incomplete (or, more generally, iff it is b-incomplete - see the definition of this term in the Hawking Ellis book). Hence Penrose's theorem proves that black hole spacetimes must contain a singularity. Then Kerr argues that the theorem does not guarantee that black holes must contain curvature singularity, or some point on the manifold where the metric is not sufficiently differentiable. This is HIS definition of a singularity in the entire paper. If black holes indeed do not require this kind of singularity, then to me that would seem like a significant realization (although I'm no expert on this) - but I honestly don't understand why Kerr picks fight against Penrose's theorem, as this theorem didn't claim to prove that black holes must contain Kerr's definition of singularity in the first place.
So is the archer's paradox. The arrow seems to go asymptotically towards the target, but is still hits it.
Yeah but no but the arrow travels across space to hit the target, and doesn't go past the target (yeah, the target's a singularity) but takes time to get there so never does. And neither does light. I'm picturing a Gideon's horn as some sort of analogy to the spacetimeyness.
I always assumed that time is frozen (or backwards) on the inside of a black hole.
This would mean that matter would accumulate at the event horizon instead of at the center.
it *would* lead to an interesting theory that you can technically keep something inside without annihilating it.
(Though getting it in or out would probably be impossible)
Also, assuming time goes backwards inside black holes, it could essentially be a mini universe.
Black holes start large and eventually grow smaller and smaller before vaporizing into nothingness.
Taking backwards logic for the inside, it goes from a very large essentially nothing with expanding border to a tiny dot of big bang vaporization.
It's an insane theory without mathematical proof, but if it's true, it could tell us something about our own universe.
...Why does it need to be backwards? If spacetime is being stretched infinitely, the 'singularity' is unreachable because there's just more and more space and time inside the black hole before and outside where it would nominally happen, forever. No need to invoke any sort of inflection point besides the various limit horizons for trajectories and such.
time and space switch their roles inside a BH horizon. You can freely go in time, but all space only leads to the event horizont. No one knows what it means tough to be able to freely move in time.
There is nothing AT the event horizon.
This is much like going faster than light - the equations work but many things are reversed and the results are, to say the least, ridiculous. So no one takes it seriously. The same is true of the interior of BH. Yet some physicist do take those silly equations as fact and make those extreme claims. That isn't science and Kerr is correct. Its nonsense. And that is a scientific fact - lmao@@georgelionon9050
You don't understand relativity. Time moves at a normal speed in every reference frame. Including beyond the event horizon. It is just that when you have a way to try to compare how much time passed in different reference frames, they would be different. From an outside observer observing an event horizon, or an object close to it, it appears as if time is moving slower. But this is just an appearance. And a strong gravitational field will make the effect stronger.
This doesn't resolve anything at all, nor prove anyone right or wrong. It's a bit of mathematics re-framing the singularity to something that infinitely approaches zero size which is a singularity?. It technically gets rid of the singularity, replacing it with a singularity-like object, falling and stretching into infinity. Pretty sure people know the singularity is placeholder.
Thank you Dr. Sabine Hossenfelder for this excellent video and for presenting the startling assertions of Kerr's paper. Now I am waiting to hear what Dr. Becky may have to say on the matter.
Do you think she released a video about on this topic since?
@@ain92ru Since black holes are part of her specialized area in astrophysics I suspect she is well aware of Kerr's work and will comment on it when she is good and ready to do so.
How refreshing that in Astrophysics you can still question "The Science" without the danger of being censored or cancelled!
THUMBNAIL: Was Hawking Wrong?
ANSWER: Yes, he should not have been on that island.
Singularities are a mathematical construct, part of a theoretical model. It is likely that any model breaks down at extremes. I have always supposed that as the singularity is approached closely some other model takes over, a kind of phase change. Unless any observable consequences result from this, it is likely to remain a matter or speculation forever. If observable consequences are seen, then this could form the basis of advancing theory more deeply.
Exactly. I don't see what the big deal is. There are singularities all over physics, but nature always fixes things at the singularity. Even quantized vortices in superfluid helium have singularities at the center, but nothing bad happens. The density of helium goes to zero at the center to fix the problem with the 1/r and the multivalued phase at r=0.
Any proof of that?
@@ThePowerLover Anything with a 1/(r^n) blows up at r=0, but we don't run into problems with the many that we deal with all the time. It's only a problem inside black holes because we can't measure there and see how it's resolved.
@@chrisl6546 I was asking for black hole singularities.
@@ThePowerLoverwhy would you think the universe wouldn’t fix those, just like any other singularity? They only seem special because we can’t easily observe inside a black hole.
Of course they don't have singularities. That idea is absurd.
I love this video, because I never could get my head around ‘singularity’, and it makes black holes even more mysterious, and fascinating! I wonder if dark matter has something to do with what they are? Thank you, Sabine.
Probably it's the other way round: (primordial) black holes make up at least some of the dark matter.
No matter what level of science or knowledge humans reach, even 100 million years from now, we will always be closer to knowing nothing than to knowing everything.
Amen, brother.
General Relativity predicts dilation, not singularities. Dark matter is dilated mass. In the 1939 journal "Annals of Mathematics" Einstein wrote -
"The essential result of this investigation is a clear understanding as to why the Schwarzchild singularities (Schwarzchild was the first to raise the issue of General Relativity predicting singularities) do not exist in physical reality. Although the theory given here treats only clusters whose particles move along circular paths it does seem subject to reasonable doubt that more general cases will have analogous results. The Schwarzchild singularities do not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light."
He was referring to the phenomenon of dilation (sometimes called gamma or y) mass that is dilated is smeared through spacetime relative to an outside observer. It's the phenomenon behind the phrase "mass becomes infinite at the speed of light". Time dilation is one aspect of dilation. General Relativity does not predict singularities when you factor in dilation. Dilation will occur wherever there is an astronomical quantity of mass because high mass means high momentum. Dilation is the original and correct explanation for why we cannot see light from the galactic center.
It can be shown mathematically that the mass at the center of our own galaxy must be dilated. In other words that mass is all around us. This phenomenon does not occur in galaxies with very, very low mass because they do not have enough mass in their centers to achieve relativistic velocities. It has recently been confirmed in 5 very, very low mass galaxies to show no signs of dark matter. This is proof that dark matter is dilated mass.
What we see in modern astronomy has been known since 1925. This is when the existence of galaxies was confirmed. It was clear that there should be an astronomical quantity of light emanating from our own galactic center. It wasn't until the 1960's that television and movies started to popularize black holes did they gradually become accepted. There was clarity in astronomy before idea of singularities took hold.
@@shawns0762 Good reply, thank you for your effort!
One thing is certain, hawking is on epstein's client list......................
The normal non rotating black hole solution is also infinitely old. I kind of assumed that it was used mainly as a mathematically simple edge case for figuring out how to combine GR and QM, rather than a description of objects commonly found in nature.
I find your videos fascinating, even though much of the subject matter is well above my pay grade. As to hypothesising on backward time travel, I guess one cannot rule it out as long as causality is preserved.
Don't be too hard on yourself. You used the correct word (hypothesising.)
@@douglaswilkinson5700 thanks our soul 👍
Question: If mass/density directly affect the rate at which time passes. Why would a star core collapse to an infinitely dense point?. I hypothesise that at a certain treshold of mass/density, time completely stops for the object, thus preventing further collapse. Because if time doesn't pass at all, how can you expect the thing to keep collapsing indefinitely? So, beyond the event horizon, time has stopped, everything is frozen in place and in time, even light. Nothing can ever happen without the passage of time. But the mass is still there, it is still bending and warping the space and time around it.
If gravity is acceleration and leads to time dilation effects, doesn't it hold that a point with infinite density would therefor have infinite time dilation, and in effect, stop time? If so, then one would think that any massive object that is currently in the process of collapsing into a singularity would never actually complete the process, because, as its density increased exponentially, time would also slow exponentially... and as a result, blackholes would be objects that are forever collapsing into a singularity, but will never actually get there. Likewise, infalling objects would fall forever, but never actually reach the center. The universe, time, whatever... will end before the process ever completes.
I think so too, and if Hawking radiation exist, it will evaporate it before the singularity forms.
If the infinity is only at 1 point, and all the other points around have finite values, this means the whole path there has finite length. And GR textbooks show how to compute this finite path and finite proper time to singularity.
@@thedeemon right, but that's from the perspective of the in-falling object, who's time isn't really effected from it's perspective. But from any outside observers perspective, the in-falling objects timeline gets stretched out at an exponential rate in relation to how close it gets to the singularity. From the outside observers perspective, it never actually forms a singularity in the first place. The in-falling objects perspective is entirely irrelevant because it's either behind the event horizon, or at the end of time, or whatever...
@@charliemopps4926 yep, that's how it looks for a static outside observer. I'm not sure why this apparent look is more relevant than the infalling one. After all, it's only a kind of "optical illusion" - once you start moving freely towards the BH, in your frame of reference objects can cross the horizon in finite time too. Perspective changes depending on how and where you move.
@@thedeemon but I'm questioning whether it really is an optical illusion. Saying it's an optical illusion suggests to me that there's a true "world clock" that exists coordinating all observers and that time dilation isn't actually really, but I don't think that's accurate.
Truly interesting Physics are finally happening again.
Can't wait for your Full video on this after you've had time to fully digested these papers.
Love it. I knew behind the singularity stuff there was something like a silly misinterpretation. Thanks Sabine for communicating it
Yes, of course you did. 🙄
Hahahaha sorry to disappoint you, but I was not the only one😁 @@-Devy-
@@ISK_VAGRWell, Kerr's paper is not correct anyway, so "much ado about nothing"..
@@dimitrispapadimitriou5622 oh ok. If that is true, i won’t be able to say. I am no physicist. However, it is evident that such singularity has to be a mis interpretation due to lack of information.
Thanks Sabine.
To me singularity never made sense. In my mind nothing says the matter would have to end up into the center. Even if black hole were mostly hollow beneath the event horizon, we wouldn't be able to tell it from outside, right?
you could probe it with a quantum magnetic light gluons, but that's pretty hard
Does "inside the event horizon" even make any sense?
@@spacejunk2186 I don't think so. I'm betting that there's no space below it. I'd guess the entire interior is no more than a single plank width across, that gets stretched to the radii of the event horizon, and everything ends up sitting just above that horizon with no-where to fall, because it's already at plank density.
Yes, if all the matter is in a plank shell AT the horizon, I don't think we'd be able to easily distinguish that from a classical black hole at any significant distance. In principle you SHOULD be able to somehow probe that surface and determine that it is different, but you'd have to do so at an incredibly minute level I think?
Alternatively, we might be able to detect the difference via gravitational waves from the collisions, if we knew what to look for. That's our only realistic way to actually observe BH behavior at the moment.
I mean if time stops past the event horizon from our perspective, does a singularity even fail or suceed to form? If a singularity is impossible in physics whilst potentially inevitable during black hole formation, then does it balance out if time stops relatively at the exact moment a singularity would be formed?
It's only a matter of perspective: for a static outside observer this whole region under the horizon is not part of their spacetime, it's in infinite future, no event there ever happened yet. But if you start to move freely towards the black hole, perspective changes, and now things do cross the horizon in finite time. So even if some things never happen for one observer, it doesn't quite mean they never happen at all.
There is no such thing as "time stopping". Time is what is measured by a clock and all identical clocks tick away at the same rate, everywhere, and under all circumstances of motion and orientation (by Local Position Invariance and Local Lorentz Invariance, respectively).
@@kylelochlann5053 time is relative though, like mentioned in the video; photons don't experience time. Muons that slam into our atmosphere to create northern lights are only able to reach the atmosphere before their half-life decays them away because of time dilation. Time dilates for those near supermassive black holes relative to those further away
@@thedeemon I guess that's where the theory about how when black holes evaporate away eventually and releasing a huge burst of energy could come in
@@terryflopycow2231 There's no slowing of time in time dilation and it's fundamental to relativity that all clocks tick at the same rate. In kinematic time dilation the world-line of the traveling clock is shorter than the world-time defined by the observer (obvious in any spacetime diagram). In the case of gravity a pair of synchronized clocks will show differences in elapsed proper time as the length along a world-line is a function of the metric, but there's no "time slowing".
Kerr is the programmer colleague who always points out your bugs before you run your code.
You admire and hate them at the same time.
I hope you don't wait 60 years to run your code
“When someone tells you who they are, believe them”. I still think we aren’t taking the tell of black holes seriously enough. If the event horizon really is the “end of happening” on one side of the boundary, then you have to assume that light, really IS frozen for forever. Eternity becomes an instant, and it only ever falls in almost infinitely far into the future when the black hole evaporates. To Kerrs credit, I offer a quote on light by David Grandy: “to a photon, all of time is an instant, all of space, a point.” Follow that logic through when applied to a black hole and it really makes it feel like that instant stretches out for forever, and the universe only ever lets light press play on traversing it’s last leg the moment it becomes thermodynamically feasible for the black hole to evaporate. Two when’s at once.
I am going to go out on a limb. You can not go back in time.
Something else he was wrong about...
Unless there is more than one time dimension.
@@scotthammond3230 There is not.
Sabine, what is your analysis of Stephen Crothers repeated and varied 'take-downs' of GR and black hole mathematics? I've not been able to find any mathematical rebuttals, only personality attacks. It's been almost 20 years now...
Whatever is at the singularity is going to be similar to the conditions of the instant the universe began.
nothing is escaping, time dilation is stretching everything out, a self contained infinity. Could already be another universe beginning in there as matter is somehow converted to space time. Easy to speculate when you can't see inside and the math says 🤷♂
Which, btw, is an interesting problem in and of itself. I've never been clear on why the universe at the start of the big bang wouldn't simply be instantly bounded by its own event horizon and never be seen again. I guess if you assume the entire universe is inside a geometric event horizon and everything we see is simply going on inside it then that's fine? I guess that 'inescapable direction' towards the 'singularity' described in black hole could simply be us moving forward on the axis of time towards an 'inescapable' future - we've just swapped an axis in space for an axis in time.
It would certainly explain why we can't go backwards in time, only mess with its rate of forwards progress. :D
The difference is that black holes in our Universe form 1-dimentional universes inside, whith only one direction (to the singularity) while our Universe is 3-dimentional. It could be the black hole from another, multi-dimentional, Hyperuniverse.
@@Jesse_359 Imagine all of the matter in the universe was in a singularity with all that curved spacetime, then someone flipped the gravity switch off. That's what we see, but space is doing some weird expansion of it's own. Maybe at the point of the big bang space itself suddenly expanded faster than light and stretched the singularity apart until it was no longer a singularity. We know that space is the only thing which is permitted to expand faster than the speed of light.
It would suck if the expansion of space is just a random value which periodically changes, and right now it's just moving to a higher value, but in the past it randomly went above C and caused the universe to begin by ripping energy right out of it's own vacuum state.
@@Boritis yeah the problem with those kind of nested universe ideas is that you're just pushing the creation of the universe into another realm without actually explaining anything about how it all began in that universe. It becomes a recursive loop like the chicken and the egg.
I always said we can't know if there is an actual singularity in a black hole. It's just that it's not like it makes a lot of difference. The point to note is that the matter going into a black hole is not disappearing out the other side since black holes of any significance are always increasing in size regardless of the amount of matter entering into them which is the reason for the vacuum of space. Whether or not they actually reach an actual singularity it doesn't really matter. There are lots of things that we can know such as how much gravity drops off outside of a galaxy and what effect does that have on the passing of time and the size of the measure of distance compared to where we are or compared to the area around a black hole.
@SabineHossenfelder Is it possible that Blackholes do not collapse into a singularity because instead they collapse into a "Quark Star"?
How could you ever verify that, behind the event horizon?
@@Thomas-gk42 Quark Stars do not have an event horizon. They are nearly dark stars but not quite.
This could be the case for solar mass black holes, but hard to see how this would generally the case, no matter what is collapsing.
@@dporangecountyWhat if their density and gravity forms an event horizon/ black hole? You cant´t differ a black hole with a singularity from one, that has a compact ,but not zero diameter object in the center.
Anyhow, though I heard of these hypothetical quark stars, I heard nothing about which force could stabilze them from collapsing to zero.
@@Thomas-gk42 Black hole horizons can form at any density, it could arbitrarily low.
"Every new beginning comes from some other beginning's end." _Closing Time_ - Semisonic
So, curve-fitting works both ways, and instead of a curve ending at a singularity, it can just begin there?
I sat by Roy Kerr in Stockholm at his Crafoord Prize lecture. We got chatting, as fellow New Zealanders, like neighbours across the fence, nice man, and I remember him saying to me, something like, 'Those guys over there...they're making all this rubbish, we don't know anything'. I just nodded in respect.
😅
@@SabineHossenfelder The other funny thing from that day was when I came into the theatre (early) and sat up front, two seats back (that is why Roy was in front of me) the only other person in there as Kip Thorne, sitting in the middle, same row, and I thought, okay, wow, me and Kip Thorne, cool. And he turned to me and asked: (and I will never forget this) "Do you have the time?". A physics joke, but it made me chuckle.
He sounds like the kind of Scientist who would fight like the devil if his theory was ever falsified. Doesn't sound like a particularly humble man to me. I admire humility above intelligence. But that's cos I ain't particularly intelligent. :)
Stephen Hawking was just a complete idiot. - Discoverer of extraterrestrials on 01.17.1995 Johann Zdebor
Which Hawking, the one from the 70s or a more recent one? He was played by at least 3 different actors.
This all seems very unsurprising to me, as what's described here has been my intuitive expectation of what would happen, ever since i gave it any real though. I always just assumed i didn't understand it properly, and I suspect I was right and I still don't. But nice if the intuitive turns out to be right.
Makes sense. Rotation can't occur if the radius is zero, and we know rotation of black holes is reality.
Also, when mass is added to a black hole, the event horizon expands. This means that the object at the center became physically larger, or more dense, or both; and a singularity cannot do either of those things.
I feel this so much, but also question why i never quetioned this simple plot hole myself, why does it get larger, if it is infinetly dense? Makes me feel very dumb on a much deeper level. I think you do not need a singularity to fold space all into itself to create a still damn scary black hole. Bonus you do not break the laws of physics, or create a place were they are "different" i am all for this!
Is "singularity" just a one word way of saying "we don't know"?
Yes. Much like 'Dark Matter'. It's a fudge.
No, it's not. It's a well defined mathematical description of what happens if you apply known theories.
If there's an event horizon, we don't know what happens inside it; mathematical theories are always going to be just a guess.
You can never remove a sigularity from a black hole, in terms of reference frames its only posible to have a singularity. Fist a Object enters the Event Horizon it interacts in 3 different refenence frames (inside,outside,object) in the outside frame you can interact with and observe the object, the moment the object is in the inner and outer frame at the same time everything breaks when a object is moved in any frame other then the Object Referrence Frame the object will break. Since a force can not be applied in referrence frames with different time constraints. The inner referrence frame can be, at any time, in the past, present or future at that point in space.
Singularities never passed my BS detector.
Where's your PhD thesis?, maybe I look it over for mistakes?, can it withstand peer review in the peanut gallery?, hmmm?
@@seanhewitt603 The black hole ate it.
Singularities stopped making sense as soon as the observations of Black Holes started occurring. How can they they all have the same infinite center while being massively different sizes and some have fast spin, while some spin slower? The likely answer is that the central mass probably has as many variations as stars do, but it all occurs at the Planck length and at energy levels and magnetic fields we cant come close to replicating yet. Some of these "maths" look infinite when you plot a good chunk of their curve, but actually find a solution at an astronomical scale (no pun intended)
I also had the same thought by chance while taking a shower just now. The point with the strongest gravity on Earth is actually not at the center of the Earth, but rather in the region close to the crust. I suddenly thought, why do people all believe that black holes have singularities? And we know that the singularity of a black hole is an infinite future. Can matter reach an infinite future? Wouldn't it take an infinite amount of time for light to pass through (almost) infinitely compressed space? If that's the case, could a singularity be created?
I did not realise Kerr was still alive - and active! I would definitely listen to him! :O
I heard that there may be a white hole on the other side!
Yes, in fact, some physicists have proposed that. I've been meaning to make a video about this, but in the end there wasn't much to say other than "some physicists think..."
Yes, so we follow the network's return, or narrow the focus to conjecture of our own, which may also have creative powers. @@SabineHossenfelder
@@SabineHossenfelder Have you considered a video on Lee Smolin's Cosmological Natural Selection hypothesis?
@@SabineHossenfelderIt sounds intriguing, at least.
@@SabineHossenfelder then the big bang was a white hole
Sounds like he was all about the holes, more so on little kids.
So if that's true we just might be able to travel through a black whole.
Well, there's still the question what all those quantum fluctuations do. Though maybe they're not there at all?
@@SabineHossenfelderjust because absolute zero is considered not reachable does not mean that it doesn't exist... same applies to singularity state... come on with this crap...
@@SabineHossenfelderI mean let's just think about this for half a second of course everything is subjective because in order to have objective reality you need to have an observer that exists from the beginning of time all the way to the end of time and the end of time has not came yet so therefore everything is only subjective... with that in mind certainty cannot be achieved therefore Singularity cannot be achieved this does not mean that we scrap this most logical idea... clickbait bs...
As far as I know, CTCs are in the r < 0 region in the Kerr solution (below the Cauchy horizon), not between the horizons. (I might be wrong tho, the Kerr metric is complicated.)
I thought the same. Wonder what she was referring to
Even using math when we can't physically experience and experiment we don't have definitive proof, I like this talk. And time and time the narrative has changed about the things we really can't experiment on.
It is embarrassing that this video has not had a follow up in the light of the rebuttals. Sabine has sunk a great deal in my estimation. Rebut the rebuttals or make some correction.
I never believed in the existence of singularities anyway, because they require matter within, quarks in particular, to change size and became zero in volume. I simply do not think that's a possibility.
penrose is still alive to refute kerr...and hopefully hand back the nobel.
Quarks are point like so they have no volume to begin with, inside or outside a black hole.
@@psychohist really. and what are virtual particles.
why is there a difference between a static and a rotating black hole at all, since it is a sphere and should look the same from all directions ??
I always thought 'proofs' were confined to mathematics or formal logic. If you follow the rules of the game the conclusions must follow from the premises. Once proven they cannot be disproven
Science does not do 'proofs' because science is empirical, using inductive not deductive reasoning.
Scientific theories are never 'settled' but always subject to modification or replacement in the event of further knowledge.