14 ms·

Black holes might be defects in spacetime

• tomcam 3y ago
  I’m sick of the QC for spacetime. Back when I was a kid, spacetime was highly reliable. Glitches in the matrix or continuum were almost nonexistent. Sad that you Gen Z-ers can’t keep it together.
• acyou 3y ago
  To the outside observer, modern particle physics looks like a cross between religion and Emperor Has No Clothes. Much of what constitutes a successful researcher and institution is not practical result (or even tangible or reproducible), but instead is political.
  • redeux 3y ago
    I’m not very familiar with modern particle physics. Can you explain what you mean by this?
    • x3n0ph3n3 3y ago
      There's a cult around string theory, where despite it not producing a single testable hypothesis in its multi-decade dominance, it maintains its dominance as an orthodoxy, sucking up most of the research grants. Speaking out against string theory in the particle physics circles of academia gets you branded a heretic and outcast, potentially costing you a career in particle physics.
      • acyou 3y ago
        We cannot, and should not come to terms with the prospect that the universe's complexities may be totally out of our reach. Best to keep trying in one way or another. Unfortunately, my comments are not constructive, I don't have a better avenue to suggest. All that I can tell is that phenomenon on human scale are easier to grasp. The bigger or smaller you get, the harder it is to observe.
    • acyou 3y ago
      I'm not too current. Last time I looked at this was 2016. My take is: Many experiments are conducted on "unique" equipment which is inaccessible to outsiders. This makes experiments irreproducible in the classical sense. For example, the CERN particle accelerator is the largest in the world, no other similar facilities exist. Much of the research done is on such facilities. 2. Scientists in the field agree upon a "standard model", which predicts certain phenomena but not others. For the other phenomena, they use a different model, which is incompatible or not reconciled with the first model. Both of these models resemble over-fitted models that describe but don't explain. There is no beautiful, elegant combination of geometry and mathematics to discover the underlying meaning of the universe there. 3. Experiment results are highly processed by researchers and constitute terabytes or petabytes of data which is easy to manipulate to suit a researcher's opinion or political ends. Lots of noise and very little discernible signal. 4. Recent experiments don't seem to be yielding new, novel, interesting or viable lines of thinking.
      • abdullahkhalids 3y ago
        > There is no beautiful, elegant combination of geometry and mathematics to discover the underlying meaning of the universe there. This is not a fair criticism. Its not like some of the smartest groups of people alive have not tried for over half a century. Nobody has the slightest real clue on a way out. What else to do, except to constantly try and break the model somehow?
  • bb88 3y ago
    I'm pretty sure that you walked out with no clothes in the scientific community, people would be happy to point out you have no clothes. People can make names for themselves poking holes in other's theories. Hell, Einstein tried to do that with quantum mechanics without much success. I guess, in that sense it's political. But the politics here is to try to bring about rational reasoning. And eventually, quantum mechanics won, not because it was the most reasonable theory, (it's not and who would design a universe this way?), but it has the most amount of experimental evidence to back it up.
    • acyou 3y ago
      I don't think most physicists in this area think the Standard Model is "correct" in the sense of actually describing what makes the universe tick. They mostly recognize it as a set of curves that are extremely well fitted to experimental data, up to a point (at which point it fails completely and necessitates a switch to another model).
• paulpauper 3y ago
  Did anyone else see the metric equation in the pdf? Talk about heavy-duty use of trig. Like a pre-calc nightmare. How was it derived?
  • raattgift 3y ago
    > heavy-duty use of trig Trig functions are useful in differential equations, expect them everywhere in differential geometry and geometric analysis. > How was it derived If you mean eqn (15) of "the pdf" <https://arxiv.org/abs/2203.12625 https://arxiv.org/abs/2203.12625> (which is what the author at the link at the very top of the discussion was trying to summarize), then it's largely a generalization of Weyl's 1917 "Zur Gravitationstheorie" approach (English translation at sci-hub: <https://sci-hub.se/https://link.springer.com/article/10.1007/s10714-011-1310-7 https://sci-hub.se/https://link.springer.com/article/10.1007...>, in particular part B §4-§5 starting at page number 793, pdf page 15 of 32) into higher dimensions. The particular generalization is described in "the pdf"'s reference 15, "Generalized Weyl Solutions" <https://arxiv.org/abs/hep-th/0110258v2 https://arxiv.org/abs/hep-th/0110258v2>. Choice quote, "Depending on which feature of Weyl's class one focuses on, there are several directions in which one can try to extend it into higher dimensions." The authors choose an approach which produces a notion of the passage of time for a hypervolume of two fewer dimensions than the whole; contrast this with a notion of the passage of time for a three-dimensional hypersurface of a Lorentzian (3+1, or four dimensions) manifold like our own universe appears to be. The authors of "the pdf" per the top of II. THE GEOMETRIES focus on five and six dimensions, the former producing following the logic of their ref 15 a set of 3d spatial volumes that are related by a notion of time, which invites comparisons with a Lorentzian manifold like our own, and which they do in III and IV. Their result is that they cannot make their structures observably indistinguishable from Schwarzschild black holes. They do not go further into merely very slowly spinning their topological solitons, and it's not clear what the metric for those would look like, or observationally how they would compare to very slowly spinning Kerr solutions (which become indistinguishable from Schwarzschild). One of the recurring themes of M-theory/stringy gravity starts with that we see a lot of spinning objects in hydrostatic equilibrium, including relativistic objects like neutron stars (notably millisecond pulsars). We can pick out the orbits of even very small companion objects in close orbits around these (< 2% of mass of Earth, < 1/2 the apoapsis of Mercury <https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b125712-b/ https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b1257...>). Those orbits are essentially Kerr orbits (non-gravitational perturbations from e.g. the NS's radiation or magnetic field are small). M-theory/stringy gravity appears largely stuck on recovering spherical symmetry (for black holes and galaxies (e.g. Verlinde's vintage 2011 emergent gravity)) rather than obviously rotating distributions of mass with lumpy and even heavy satellites (from Draugr to the Large Magellanic Cloud and its dozens of friends, to clusters of thousands of galaxies). General Relativity's universality of free fall (UFF or "strong equivalence principle") is extremely well supported at all these scales. That UFF needs to be searched for (often requiring strong suppression of extra gravitational degrees of freedom, except exactly where they want to be different from naive quantization of General Relativity) in these supergravity theoretical ideas mean these theories are maybe-interesting but of no practical astrophysical value at this time.
• wesapien 3y ago
  Test
• JakkTrent 3y ago
  Defect isn't the right word to use for something that is part of a process that seems to play out in every instance we are aware of. If every supernova above a certain size creates a black hole that's not a defect, it's an effect. If the center of every galaxy contains a black hole - how can that be a defect?
• arisAlexis 3y ago
  Or proof of a simulation... :)
• xwdv 3y ago
  How can spacetime have a “defect”? Isn’t this just a feature?
  • deleted 3y ago
    [deleted]
  • techwiz137 3y ago
    It's not a bug. It's a feature.
    • liotier 3y ago
      Just update the specification with the observed behaviour and presto - black holes are no longer defective !
  • magicalhippo 3y ago
    In this case it's about topological defects[1], also known as topological solitons, which is explained rather well on SE here[2]. Mathematicians and physicists try to give words to concepts, they don't always map well. As Wikipedia puts it: Topological solitons arise with ease when creating the crystalline semiconductors used in modern electronics, and in that context their effects are almost always deleterious. For this reason such crystal transitions are called topological defects. However, this mostly solid-state terminology distracts from the rich and intriguing mathematical properties of such boundary regions. Thus for most non-solid-state contexts the more positive and mathematically rich phrase "topological soliton" is preferable. [1]: https://en.wikipedia.org/wiki/Topological_defect https://en.wikipedia.org/wiki/Topological_defect [2]: https://physics.stackexchange.com/questions/285731/what-is-a-topological-defect https://physics.stackexchange.com/questions/285731/what-is-a...
    • Attrecomet 3y ago
      Interesting. During my time in solid state physics and later quantum information, we just used "(topological) defects", not "topological solitons", though of course papers trying to sound cool could use that term. It takes about 2 uses to not conflate "defect" with anything deleterious, just the breaking of an otherwise functional symmetry.
• EGreg 3y ago
  I think defects imply you know there is some purpose other than the phenomenon you are referring to as a defect
  • Enginerrrd 3y ago
    Not at all. Defects are typically just points of discontinuity or where a pattern breaks. These happen when something relatively continuous is forming but then the pattern breaks locally due to either global initial conditions or something unusual happening locally. I think the term is probably borrowed from the theory of crystal lattices where defects are classified: dislocations, substitutions, and holes. As a crystal is forming, sometimes two contiguous regions can't come together in the same pattern because of initial conditions where the lattice won't line up right. These then form adjacent "grains". Alternatively, sometimes internal stresses result in a dislocation where a large section of crystal shifts along a line of symmetry. Or sometimes a stray impurity is hanging out and a crystal forms around it. Or holes happen where it's just like musical chairs as the crystal is forming and there's one too few atoms to go around. In none of those cases is there some "purpose", and yet there is a clear local discontinuity in an otherwise large scale pattern. The terminology fits pretty well to the situation here I think, only they're speaking about topological phenomena.
• metanonsense 3y ago
  If I am not completely wrong, this headline has nothing to do with the linked article. The article is about "topological solitons" that - according to the article - look "to outside observers" like black holes.
  • wrycoder 3y ago
    The phys.org article isn't worth spending time on. It's better to read the original arxiv paper that @supermatou linked in a peer thread.
  • kadoban 3y ago
    I think the headline just doesn't do enough work specifying how unlikely this is. The article otherwise seems to match. We are "outside observers", correct? So black holes we see "might" (theoretically, in an unproven and maybe unprovable system of physics) be defects in spacetime.
    • metanonsense 3y ago
      I share your understanding but when the article does not even mention that possibility, a link text seems to be an odd place to make such a claim.
      • fnordpiglet 3y ago
        Only if you don’t look at it through the lens of selling advertisements based on impressions.
      • digging 3y ago
        I don't understand how you didn't take that away from the article... it was clear to me what it was saying.
        • metanonsense 3y ago
          Can you give me some pointers where you read this? I mean, at the end they even write "It's only once you got close would you realize that you are not looking at a black hole." I take from that that they are aware that black holes are different from topological solitons. And I read at no place that they consider black holes actually being topologial solitons. So, when the authors think that those two things are different and they classify solitons as "defects in spacetime", wouldn't this directly contradict the headline "Black holes might be defects in spacetime"? I would be glad if you showed me where my reasoning is wrong.
• marricks 3y ago
  Article states that solitions are not black holes but only seem like black holes from a distance. Also they are hypothesized from string theory but haven’t ever been seen, probably because they’d appear the same as black holes except up close? Title should be updated to something like: “A theorized defect in space time that appears to be a black hole”
  • denton-scratch 3y ago
    It's a really thin article. It fails to say how "topological solitons" are different from wave-mechanical solitons, nor does it explain why they look like black holes, or why they lack an event horizon. I'm routinely disappointed with phys.org. It's pop-sci with the "-sci" component reduced to a remnant.
    • marricks 3y ago
      100% agree. It does link to an actual paper which is a step up from blogspam https://link.aps.org/doi/10.1103/PhysRevD.107.084042 https://link.aps.org/doi/10.1103/PhysRevD.107.084042
• zgramana 3y ago
  The real takeaway is that researchers may have found a potential test for string theory. Its presumed lack of falsifiability has been one of its drawbacks and has been the source of some of the controversy around it. Finding a potential test that could be conducted with telescopes instead of high energy particle accelerators would be a big moment in modern physics.
  • nathan_compton 3y ago
    I don't see how this is testable, given what is written here.
  • simiones 3y ago
    I think there are all sorts of other potential tests of string theory. The problem is that for all the actual tests that were ever proposed, it failed (supersymmetry, various proposals for sizes of the extra dimensions).
    • progrus 3y ago
      Yeah, it’s more they might have found a way to test the latest fix, than anything.
    • sigmoid10 3y ago
      To be fair, what failed is low-energy Supersymmetry and large extra dimensions, because these things were actually accessible by current gen experiments. But there's a huuuge amount of room left unexplored.
      • dcsommer 3y ago
        Not without fine-tuning. The issue is that high-energy supersymmetry no longer removes the "ugly constants" of the standard model -- it just shifts them somewhere else. Disclaimer: not a physicist, but I learned a lot reading "Lost in Math: How Beauty Leads Physics Astray".
        • 3y ago
• jiggawatts 3y ago
  I've been keeping my brain occupied on long drives by trying to come up with a theory of everything, because... why not? My current pet hypothesis is that all fundamental particles are sort-of like tiny black holes, and that the space-time distortion caused by black holes is precisely the same thing that ordinary matter causes. All matter and energy are space-time distortions, which is why mass-energy bends space time. It's not a secondary effect, the bending is what everything is, not a property that things have. (This is essentially just a variant of Kaluza Klein theory, or others like it.) Particles are kept apart by their spin, same as in well-established physics. Matter is still mostly empty space, same as normal. In this toy model, neutron stars are like a boba tea, with the black holes of particles close-packed but still not touching. When forced into forming a black hole, the event horizons of individual particles begins to merge, forming a "super-particle" that expands out. When fully-formed, the black hole is hairy, with a very dense packed crust of still-separate particles layered over a very lumpy surface, inside which there is... nothing. Not even space-time. The surface is where space-time ends. It's like... imagine if we lived on a knitted jumper or a space-time like woven cloth and could only follow threads. If someone were to poke a hole in the weave with a finger, pushing aside the threads, then it would be meaningless to ask what threads are inside that hole. There aren't any. The "weave space" doesn't extend into the hole. This simultaneously satisfies a long list of requirements gathered from modern physics: 1. Black hole formation is a gradual, continuous process at both microscopic and macroscopic scales. This model can start all the way down with the first pair of particles that got squished together and then can be extended all the way up to something the size of a star. 2. Black holes are hairy instead of smooth, satisfying thermodynamics and quantum information theory. 3. There's no paradox of what happens when you go past the event horizon. There's no singularity. The event horizon is a surface, essentially just a highly red-shifted neutron star. Hitting it is the same as hitting a neutron star. You do not go through. You get squished. 4. There's no need for complex maths to explain black hole evaporation. In a sense, black holes don't exist, they're just a very time-dilated neutron star, and their evaporation is just an ultra-slow-motion explosion of a neutron star. 5. A well-established theorem is that many properties of a black hole grow in proportion to their surface area (2D), not their volume (3D). This theory matches that. There is no volume, there's only the surface. The inside doesn't exist. When approaching from normal flat 3D space, space gradually becomes fractal (2.x dimensional), smoothly transitioning to a 2D space, which is the event horizon. 6. It is time-reversible. Seen backwards in time, "fingers" of 3D space invade into the event horizon, splitting it up into smaller and smaller chunks that bud off to form small, stable spheres that evaporate away. These are the particles that made up the black hole.
• giantg2 3y ago
  For some reason it really irks me that they are using the word defect. It's like they forgot that the rules/model we set follow what happens in reality. If there is a defect, it's not in spacetime, it's in our understanding.
  • r2_pilot 3y ago
    It's a commonly used word to describe irregularities in lattices, such as grain boundaries in metals or imperfections in crystals.
    • devmor 3y ago
      I was wondering about this too, thank you for the insight!
    • giantg2 3y ago
      That makes sense
  • _Microft 3y ago
    It's a technical term in crystallography/solid state physics as well. https://en.wikipedia.org/wiki/Crystallographic_defect https://en.wikipedia.org/wiki/Crystallographic_defect
  • EamonnMR 3y ago
    If your spacetime contains black holes you may be entitled to compensation from the manufacturer. Please retain this notice and your receipt. Known in the state of California to cause spaghettification. Offer not valid in worldlines crossing the event horizon.
  • zaebal 3y ago
    Think of it as an abnormality in spacetime.
• b800h 3y ago
  All my life, they've been hawking string theory; what feels like 40-odd years of breathless articles in New Scientist and on "Horizon". I don't really understand why it's still funded.
  • indy 3y ago
    Sunk cost fallacy. A lot of people have spent a lot of their time developing this theory
    • b800h 3y ago
      And I suppose given that it was exciting in the 1980s, these are the people in positions of power at the moment.
      • chongli 3y ago
        Tenure has its pluses and minuses. If a string theorist has tenure, they’re going to be string theorizing for a very long time. Sunk cost fallacy plays a role but so does specialization. If you’re leading string theorist and you walk away from string theory, what are you? A mathematician?
        • bumby 3y ago
          If you adjust your priors in response to data and end up walking away from a faulty theory, I think the term is “scientist”. It sounds like the problem from your perspective is they identify themselves as “string theorists” first and “scientists” second.
          • eep_social 3y ago
            And yet, “science advances one funeral at a time” probably because scientists are people.
          • runarberg 3y ago
            I can’t stop thinking about one the greatest scientific discoveries in this context. Kepler was convinced the planetary orbits around the sun were circular and could be described with the five Platonic solids. His theory was testable, and when he measured it against observation, it failed. He could have persisted, modified his theory, and continued on the wrong path, but instead, he discarded his theory and discovered elliptical orbits with his three laws of planetary motion. Kepler was a scientist.
• b800h 3y ago
  "But we do have candidates, including string theory. In string theory all the particles of the universe are actually microscopic vibrating loops of string." Actually string. Brilliant exposition this.
• supermatou 3y ago
  The actual paper (no paywall): https://arxiv.org/pdf/2212.06837.pdf https://arxiv.org/pdf/2212.06837.pdf
• briantakita 3y ago
  Has anyone considered that black holes may be defects in the model? There's an old phrase, "the map is not the territory". Some old maps show the edge of the world with giant sea monsters & ships falling off the ocean.
  • gizmo686 3y ago
    Einstein originally thought that black holes were simply an mathematical artifact, and not possible in reality. Since then, we have observed objects that look a lot like we would expect black holes to look. There are theories, such as this one, that describe those objects as something different than what GR proposes, but thus far no testable prediction has contradicted GR's version. Part of the problem is that many of the differences are about the interior of the event horizon. At least under GR's model, such differences are nit observable, even in principle.
  • vletal 3y ago
    What if black holes are NaNs in the simulation we live in. Maybe it was written by a phd student as an experiment for his thesis.
    • skirmish 3y ago
      More like a half-baked elementary school science project. Consider: * Lazy evaluation was used to reduce computational costs. Unless an event is observed, it never collapses into reality. Cannot use up all household's hyper-electricity supply, parents will be mad. * Make GR and QM work nicely together? Nah, too hard, the show-and-tell is tomorrow morning. * Intelligent beings on multiple planets? Just a single planet will do for a C, maybe a C+. And no time left to make them interestingly different anyway. Be ready, once the project grade is announced, this simulation will just blink out of existence. Hyper-CPU power will be needed for billions of years (our time) of hyper-Minecraft.
• flkiwi 3y ago
  From a layperson's perspective, "discovered" is doing a LOT of work in the linked article given it appears to be a hypothetical construct (topological soliton) within a hypothetical construct (string theory).
  • nathan_compton 3y ago
    It is perfectly reasonable to use the word "discovered" for purely mathematical facts for which the demonstration is non-trivial.
    • bashinator 3y ago
      I guess that depends on how much of a Platonist you are :-D
      • nathan_compton 3y ago
        I am an anti-platonist but still think its reasonable to say one discovered a mathematical fact. All this amounts to is discovering that you can reach a sentence in a formal language using the rules of the language and the axioms. One can believe that a recipe for pancakes exists without believing it does so via participating in an unseen ideal world.
    • flkiwi 3y ago
      If it were phrased as "discovered a mathematical solution in string theory that would, if confirmed, represent a topological soliton" that would strike me as more accurate. But this is the reason I stated up front that I'm a layperson: I can certainly imagine that within the community there are conventional uses of language that differ from a layperson's use. That's certainly the case in my own. But the way it is phrased appears, to a layperson, to indicate that the thing has been found to exist.
    • airstrike 3y ago
      From another layperson's perspective, it sounds like you are arguing it is "perfectly common" whereas the parent is arguing "it is unreasonable, even if it is common"
• dukoid 3y ago
  Something I was always wondering about black holes: Does there really have to be a singularity? If I understand relativity correctly, time slows down as mass increases. Couldn't this slowdown affect the contraction so that it never can actually reach an "actual" singularity point?
  • treeman79 3y ago
    https://youtu.be/351JCOvKcYw https://youtu.be/351JCOvKcYw There are a number of theories on black holes not being singularities. PBS space time goes into a few of them
  • nathan_compton 3y ago
    This is actually a pretty tricky question. The standard black hole solutions are highly idealized in order to make them tractable. In particular, they have a lot more symmetry in time than you would expect a black hole to have. Actually forming a black hole from realistically distributed matter undergoing gravitational collapse is a more complicated problem to talk about in GR. So you pose a genuinely interesting question. I think the singularity theorems address it however: https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singularity_theorems https://en.wikipedia.org/wiki/Penrose%E2%80%93Hawking_singul... The basic idea is that singularities are a very general feature of general relativity, not confined to specific solutions to the field equations but sort of inevitable for a large number of initial conditions. So while the standard black hole solutions are highly idealized, we have good theoretical reason to believe that singularities exist in non-trivial solutions to the Einstein Field Equations.
    • GoblinSlayer 3y ago
      You're confused by mathematical terminology. Since mathematics is ignorant about time, "inevitable" is a synonym to "exists" there, because mathematics can easily assume infinite time passed by usual induction, but in physics time isn't negligible. Even in terms of mathematics you need to believe in actual infinity to believe that formation of a black hole completes.
  • gizmo686 3y ago
• thrill 3y ago
  The only defect is in our understanding.
  • NHQ 3y ago
    People understand this dogma perfectly well, no reasoning or critical thinking required. Literal, to be under the standing of another mind. No logical basis exists for black holes, they are a rationalization for the faulty foundation upon which they lie, a fantasy to explain condescending pseudotheory. The defect is defending a false doctrine, accepting as truth a scientifically evident hoax.
• BulgarianIdiot 3y ago
  Defect means imperfection, shortcoming, flaw. This implies reality has a design, a plan, that it was executed according to, which execution can have defects in it, compared to the plan. Design & plan means designer & planner. So yeah, we should be careful what words we use.
  • SAI_Peregrinus 3y ago
    It also means an irregularity in an otherwise regular structure. It's jargon, which probably shouldn't be used in a popular science article, but it does not imply any sort of plan.
    • furyofantares 3y ago
      > which probably shouldn't be used in a popular science article Depends on if you're maximizing for 'engagement' I guess :/
    • BulgarianIdiot 3y ago
      Define "regular structure". So the center of the sun is as regular as my living room, but a black hole is a bit too much for someone. For whom though? And how did they decide this?
  • BulgarianIdiot 3y ago
    Funny that I get downvoted. I'm curious what is pissing everyone off that much. Physics and spacetime have no "defect" unless you define relative to what. Our theories of physics are just models we work with for our benefit, reality is entirely unconstrained by our models and concerns. And our opinions of a "defect" with respect to our models. We've long known the singularity is only "singularity" with respect to General Relativity. It's the place where the model breaks down. The model, not reality.
    • _Microft 3y ago
      "Defect" has a different meaning here than it has in common language, so people disagree with the comment. If you are curious, then try articles like on "Topological defect", "Crystallographic defect", "Cosmic string", ... in Wikipedia to get an idea what defect is supposed to mean here. > Our theories of physics are just models we work with for our benefit, reality is entirely unconstrained by our models and concerns. True but every student of physics is taught right from the beginning that every model only has a range of parameters in which it is valid. Example: you can easily calculate speeds non-relativistically just fine if you are aware that you will only get good approximations of reality if the speeds involved are a low (~ single-digit) percentage of the speed of light. Outside of that, the results will be non-sense. We create the models after reality and use these models to predict things. After experiments, we know if the the model is still valid in a new range of parameters. Since we know that the laws of nature do not change (we can and do test that!), we can now assume that we have a model that fits well with reality in a wider range than before. What you see here in progress is exactly the attempt to find an alternative explanation for that what we expect blackholes to look like because we know that our models might not be right there.
• rcme 3y ago
  > Since we know that infinite densities cannot actually happen in the universe, we take this as a sign that Einstein's theory is incomplete. But after nearly a century of searching for extensions, we have not yet confirmed a better theory of gravity. Is it really true that infinite densities are impossible? Consider a function that measures the volume of an object with respect to time, say V(t). If the force of gravity is strong enough to overcome every other force, wouldn't V(t) approach 0 as t goes to infinity? Isn't that essentially having infinite density?
  • vletal 3y ago
    You just arrived to infinite density using a concept of infinite time. Now you need to justify existence of infinite time. The argument is that there is no infinite amount of _anything_. That is a fictional concept of 'too many parts to count'.
    • rcme 3y ago
      I guess my point is that there isn't really an infinite quantity in mathematics, either. What we think about as "infinity" usually involves some type of unbounded limit.
  • qubex 3y ago
    You’ve just defined gravitational collapse. The real question is: is the volume infinitely compressible or is there something that would eventually oppose enough counterforce to halt the collapse?
  • soulofmischief 3y ago
    It's what you would consider a mathematical limit. The limit is never actually reached. V(t) becomes vanishingly small, to the point that time effectively stands still, but mathematically it should still always remain a non-zero value, and thus density at the singularity isn't infinite. Anyway, at that point measuring things becomes exceedingly difficult and abstract.
  • grungegun 3y ago
    the infinite density is actually after a finite amount of time, since black hole collapse has already happened, which is why it matters that they are predicted to have infinitely dense points at their centers. The key is that this isn't a limit, GR seems to expect that there are infinitely dense objects just floating around breaking space-time.
• deleted 3y ago
  [deleted]
• livinglist 3y ago
  I just was interested enough to look up what’s the nearest known black hole to Earth, and it’s Gaia BH1 which is 1560 light years away from us…can I still get my hope up that during my lifetime I can witness some significant breakthrough regarding our knowledge of black hole?
  • dustingetz 3y ago
    if AGI 2030 then presumably singularity shortly after at which point physics is immediately solved subject to the computational limits of the amount of energy available in our solar system (beyond which we start paying speed of light delays to move compute to energy dense regions of the galaxy, unless warp drives are solved too).
• hk1337 3y ago
  Glitch in the Matrix.
  • JoBrad 3y ago
    Imagine the git blame results on the commit that introduced this defect.
• nico 3y ago
  What if black holes are a very thin shell and all the matter is just on the surface, orbiting so fast around a center that it cannot escape
  • sclarisse 3y ago
    First: “Orbiting the center” implies movement in circles and ellipses, and thus implies angular momentum. Angular momentum is a conserved quantity. If the collapsing star didn’t have it, the black hole’s contents won’t spontaneously develop it. Some black holes do have it, but not all. Second: under general relativity spacetime is biased so the three direction “future” is pointed to the center of the black hole. This is true of any mass, but in the black hole it is so intensely pointed that even traveling through the space part of spacetime at the maximum possible speed (the speed of light) isn’t fast enough to escape that, not in any direction. Perhaps the fastest moving objects at the very edge of the region of space we call the “event horizon” could fall in slowly enough that the black hole evaporates around them? I dunno, I don’t have math for it. But even then I wouldn’t count on it for the general case. Better to imagine everything crushed as it is dragged to the center - perhaps first into neutronium, and then quarkium, and then something hard to say except that it’s all a giant high-energy mess.
  • mr_toad 3y ago
    > orbiting so fast around a center Inside the event horizon you’d need to orbit faster than the speed of light. Outside the event horizon - if the matter wasn’t in orbit before then it can’t magically gain momentum to be in orbit.
  • onlyrealcuzzo 3y ago
    Sure, but wouldn't something need to be in the center for it to do that?
    • deleted 3y ago
      [deleted]
    • nico 3y ago
      https://www.livescience.com/62547-what-is-center-of-universe.html https://www.livescience.com/62547-what-is-center-of-universe... The universe has no center. Maybe nothing has a center?
• marricks 3y ago
  The actual article linked has a better title and the abstract is probably sufficient for anyone interested in the subject: https://link.aps.org/doi/10.1103/PhysRevD.107.084042 https://link.aps.org/doi/10.1103/PhysRevD.107.084042 The given title is just flat out misleading.
• gcgbcfy 3y ago
  String theory like most of theoretical physics is just made up. Today our knowledge of atomic physics and the cosmos is no more improved little since 1945. There’s a lot of theories, but ultimately they just add up to different kinds of particles interacting in non-verifiable ways. If you look at the actual advancements it’s pretty laughable we’re sitting here saying “Hey look this theoretical thing called a black hole, that easily could just be some type of unknown radio telescope interference? It maybe might exist for a different reason than we thought!” Your layman’s understanding that a black hole is some kinda big suck-y thing in space is actually better then engineering an elaborate and probably incorrect theory.
• friend_and_foe 3y ago
  This is pretty badly written. Something looks like a black hole but doesn't have an event horizon? Isn't a black hole nothing but an event horizon to an outward observer? How does it look like a black hole if it doesn't bend light with gravity? You could hold it in your hand "if you survive the encounter"? So you can't hold it in your hand? *What would happen to you if you touched it?"
  • GoblinSlayer 3y ago
    Collapsar asymptotically approaches state of black hole as inverse exponent of time. Feel free to detect such small difference.
  • 100721 3y ago
    I find a lot of posts from phys.org to be highly editorialized, with ambiguous and sensational headlines. It is a low quality source, imo
  • eigenform 3y ago
    I think implication is that there's a spectrum of related phenomena (and that "black holes" with an event horizon are an extreme case)
  • elashri 3y ago
    The Topological solitons would appear exactly like predicted black holes from a distance, with shadows, light rings, and gravitational wave signatures. It is not about the event horizon. It just telling you we would see them as black holes if we look to them from some distance. Remember that cannot observe the event horizon directly, the famous gravitational waves discovery in 2015 is an example of indirect black holes observation The other important difference is that they could form without mass which is not the case with black holes. So I am not sure that I would agree with you.
    • zelphirkalt 3y ago
      So if they form without mass, why would they bend light like black holes? If they don't bend light, then it seems to me that they would not really appear as black holes.
• eigenform 3y ago
  (I'm not a physicist, but) from the paper: > All together, the Schwarzschild topological solitons have scattering properties very similar to Schwarzschild black holes. The main difference will be a residual faded glow that emerges from inside the would-be shadow. So basically, things fall in, bounce around, and come back out (albeit scrambled)? Seems intuitively more reasonable than singularities?
• davidgrenier 3y ago
  "Since we know that infinite densities cannot actually happen in the universe" How do we "know" that?
  • vitehozonage 3y ago
    Yeah, I stopped reading when i got to that sentence
    • echelon 3y ago
      Infinity and singularity are mathematical constructs. They look great on paper, but we don't know if they have actual physical analogs. It could be that relativity and the physics around black holes, the big bang, etc. are wrong.
      • vitehozonage 3y ago
        Could be true that there is nothing with infinite density. But it is certainly not known with certainty, so the statement is horribly wrong. >It could be that relativity and the physics around black holes, the big bang, etc. are wrong. Of course, that's almost certain
      • bell-cot 3y ago
        > Infinity and singularity are mathematical... THIS. That I've seen, the [astro]physicists are confident that there are no actual physical infinities nor singularities. With the public, they'll use those terms for situations "approaching" infinities and singularities. But in private, they're busy using all sorts of clever mathematics and calculations and arguments to avoid having any infinity or singularity occur, even on paper. A very basic example: https://en.wikipedia.org/wiki/Dirac_delta_function#Motivation_and_overview https://en.wikipedia.org/wiki/Dirac_delta_function#Motivatio...
        • dandare 3y ago
          Are you saying that we have evidence that universe is not infinite?
• zelphirkalt 3y ago
  The article has some pop-science feel to it: > But we do have candidates, including string theory. Oh no, you mean the theory that physicists say we see no evidence of at all? Great, if that is the basis, ... lets see what follows. > In string theory all the particles of the universe are actually microscopic vibrating loops of string. In order to support the wide variety of particles and forces that we observe in the universe, these strings can't just vibrate in our three spatial dimensions. Instead, there have to be extra spatial dimensions that are curled up on themselves into manifolds so small that they escape everyday notice and experimentation. Right, it would most definitely escape the experiments I have in my garage ... Who talks about "everyday experimentation" when talking about string theory? I mean, in "everyday experimentation" we don't even see atoms and most of us in their "everyday experimentation" do not even see molecules. Really makes you wonder what "everyday experimentation" they are going on about. > That exotic structure in spacetime gave a team of researchers the tools they needed to identify a new class of object, something that they call a topological soliton. In their analysis they found that these topological solitons are stable defects in space-time itself. They require no matter or other forces to exist—they are as natural to the fabric of space-time as cracks in ice. The research is published in the journal Physical Review D. But cracks in ice do consist of something: Usually air that fills the gaps. And even if we put ice in perfect vacuum somehow, there is still space between the parts of the ice. It is not like there is nothing. Seems like a bad analogy. At least they would have to go into what "fills" the gaps like with ice. Some space-time-vacuum? On top of that, the article tries to explain things by using even more in my vocabulary undefined terms like "soliton". > Because they are objects of extreme space-time [...] Ah, they are "of extreme space-time"! Now I know ... nothing. I don't feel like I understood anything valuable, but more like reading a sci-fi novel. Although, sometimes sci-fi novels do make more sense in their own invented universe than this article. Was this article perhaps generated by some language model?
  • deleted 3y ago
    [deleted]
• dathinab 3y ago
  Wasn't string theory very thoroughly "dis-proven" (as in you have to go through absurd hoops to make it still work which indicates it most likely is not the truth at all, even though you can not completely rule it out because some concepts are very resistant to be proven to not exist).
  • phyzome 3y ago
    Hmm? I've not heard of any such thing. The main problem I've heard is that it's hard to come up with a test that will confirm or reject the hypothesis, let alone distinguish between the different variations.
• luxuryballs 3y ago
  they might be cosmic whale blow holes too
• codethief 3y ago
  From https://journals.aps.org/prd/abstract/10.1103/PhysRevD.107.084042 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.107.0... : > We show that topological solitons are remarkably similar to black holes in apparent size and scattering properties, while being smooth and horizonless. Incoming photons experience very high redshift, inducing phenomenological horizonlike behaviors from the point of view of photon scattering. Thus, they provide a compelling case for real-world gravitational solitons and topological alternatives to black holes from string theory. This is certainly interesting but so far they have only looked into Schwarzschild black holes (the simplest kind of black holes). Their case would be much more compelling if they also found soliton solutions that looked like non-static (Kerr) or even non-stationary/dynamic black hole solutions (<-> black hole formation). I know far too little about solitons, unfortunately, to estimate how easy/difficult it would be to find/construct those.
  • raattgift 3y ago
    > only looked into Schwarzschild black holes What plane is the authors' "equatorial plane"? Shortly after their eqn (31), "One should a priori do a similar computation out of the equatorial plane to obtain the total size of the solitons. Due to the complexity of the geodesic equations, this is only possible numerically. However, we will see in the next section that the outer photon shell is actually almost spherically symmetric and slightly flattened at its poles". (ETA: "... the Schwarzschild topological solution is not spherically symmetric ...", just before section A. Methodology). Central SMBHs' spin appears to be largely far from parallel to their host galaxies' angular momentum[1]. Spin gives us an equatorial plane for the SMBH. Is there physical motivation for picking an equatorial plane if we found an SMBH with negligible J (and no jets)? I don't doubt that people would land on some convention (e.g. equatorial plane parallel to host galaxy's north if available, our galaxy's north if not), but do doubt that the convention would reflect physics (i.e., that there is such a plane where J = 0 or even that such a plane is relevant where J <<< 1, even if the plane is thereby picked out) rather than useful coordinates. I scanned the paper only briefly (I'm not really interested in black holes out of a cosmological or at least astrophysical context and am in no hurry to jump ahead of further EHT results) but found myself curious about the authors' "these solutions can be embedded in string theory" as their ref [17] at first glance seems to be about AdS, an acronym which is found only once in this paper. What provokes my wondering is in particular, "and so an asymptotic observer will barely notice the difference between the parallax angles" (among other references to an asymptotic observer), drawing a comparison with a distant Schwarzschild observer, again around eqn (31). "Barely notice" is, at least qualitatively, interesting wording. Can an observer at infinity more than barely notice the difference between a cold noncompact spherically symmetric uncharged nonspinning central mass and a Schwarzschild BH? [1] This is especially true for Sgr A*, see EHT paper https://iopscience.iop.org/article/10.3847/2041-8213/ac6674 https://iopscience.iop.org/article/10.3847/2041-8213/ac6674 which is wildly "tilt"ed (to use authors' expression).
• dandare 3y ago
  > Since we know that infinite densities cannot actually happen in the universe... Lol, and how exactly do we know that?
  • astrange 3y ago
    https://physics.stackexchange.com/questions/26515/what-is-exactly-the-density-of-a-black-hole-and-how-can-it-be-calculated https://physics.stackexchange.com/questions/26515/what-is-ex... But if it wasn't for that, you wouldn't be able to collect infinite mass in less than infinite time.
• exabrial 3y ago
  Is it true that general relativity also predicts white holes?