259 ms·
> "At the beginning of time and the center of every black hole lies a point of infinite density called a singularity" my understanding was that this was d̶i̶s
by achille 2y ago
> "At the beginning of time and the center of every black hole lies a point of infinite density called a singularity"
my understanding was that this was d̶i̶s̶p̶r̶o̶v̶e̶n̶ mathematically incorrect:
- https://news.ycombinator.com/item?id=38636225 https://news.ycombinator.com/item?id=38636225
- sabine's take: https://www.youtube.com/watch?v=nz55jONtFAU https://www.youtube.com/watch?v=nz55jONtFAU
edit: disproven -> mathematically incorrect
- JumpCrisscross 2y ago> my understanding was that this was disproven To the extent anything in this discussion can be absolute, it's the wrongness of your statement. Nothing about singularities has been empirically proven (or disproven).
- oneshtein 2y agoWe can empirically prove that gravitation cancels out in the gravitational center of an object, if we will dig into Moon.
- mr_mitm 2y agoWhat does this have to do with singularities? No one expects any kind of singularity anywhere around or in the moon.
- oneshtein 2y agoSingularity is not possible at 0G, isn't?
- JumpCrisscross 2y ago> Singularity is not possible at 0G, isn't? One divided by zero is a singularity. Singularity, mathematically speaking, means your math breaks. Calculus gets around this problem with limits. But there is absolutely nothing about physics that prohibits singularities, even gravitational singularities, in a zero G space because by definition a gravitational singularity per se has an undefined G.
- oneshtein 2y agoSingularity means that at least some barions will be at the same place in the same time, which against nature of fermions. Moreover, it hard to imagine that Higgs bosons will act at same place and time with same effectiveness. So, I cannot believe in a singularity unless it will be physically demonstrated.
- mr_mitm 2y agoSounds like you mean fermions. Bosons absolutely can occupy the same quantum states, look up the Bose-Einstein condensate. Also, no one serious claims that singularities exist when taking quantum mechanics into account. It's completely unknown territory.
- oneshtein 2y agoI wrote «barions», but yes, you are right, I meant «fermions». Fixed.
- JumpCrisscross 2y agoThey’re mixing up barycentres [1] and baryons [2]. [1] https://en.m.wikipedia.org/wiki/Barycenter_(astronomy) https://en.m.wikipedia.org/wiki/Barycenter_(astronomy) [2] https://en.m.wikipedia.org/wiki/Baryon https://en.m.wikipedia.org/wiki/Baryon
- oneshtein 2y agoAnyway, I propose to dig tunnel to the center of the Moon with plasma cutters and make a lab there. IMHO, the result will be worthy. As non-native speaker, it's hard for me to argue with native speakers (especially when I sick, tired, in army, and at war), and I refuse to use AI to translate, because I suspect that such messages will be automatically rejected by future archivists.
- nathan_compton 2y ago
- credit_guy 2y agoYou don’t seem to be new around here, so this quote from this forum’s guidelines is more for the benefit of others > When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3."
- JumpCrisscross 2y agoYou’re right. My apologies to OP and y’all. Can’t edit, but the snark was uncalled for.
- slwvx 2y agoI don't see any name calling. Could you eplicitly state what the problem is?
- JumpCrisscross 2y agoThe comment stands factually with just the second sentence.
- wavewrangler 2y agoBut that is not name-calling. In your words, that is snark. Are all snarky comments also name calling now, and vice-versa? One could argue that the comment stands factually with just the first sentence, too. It’s strong, yes, but very different from name calling. I think it’s a valuable tool in learning in that it [snark] reminds us to choose our words very carefully, and we all need reminders of that sometimes. Also…
- strogonoff 2y agoThere are plenty of various oblique ways of expressing similar sentiment that can hurt an educated person much more than name-calling (which, conversely, can be more amusing than anything). Digs like “the wrongness of your statement” are definitely far on relevant spectrum. Therefore, I believe the rules against name-calling are not literal. As you noticed, attempting to restrict discussion more strictly would make it bland, but on the other hand when it comes to literal name-calling in a civilized discussion it’s way past all limits. Tangentially, I was surprised to learn recently that merely the use of specific “you” in an argument is already considered unnecessary and perceived as somewhat confrontational. Haven’t confirmed it from multiple sources (not sure how to search for), but in hindsight it makes sense: the mood changes, and the argument can quickly devolve thereafter. I suspect it might be something from psychotherapy practice.
- biimugan 2y agoYour first link goes to a 2023 arXiv pre-print that never landed in any journals as far as I can tell (could be wrong though). And there seems to be some controversy about whether Kerr's math shows what he says it shows. This is the danger of trying to sensationalize science and putting any special weight on science influencers, especially ones who very often seem gung-ho about any story that challenges the status quo despite the evidence.
- deleted 2y ago[deleted]
- monocasa 2y agoTo be fair, it's written by literal Roy Kerr. https://en.wikipedia.org/wiki/Roy_Kerr https://en.wikipedia.org/wiki/Roy_Kerr
- ziddoap 2y agoPBS Space Time's take on Kerr's paper: https://www.pbs.org/video/what-if-singularities-do-not-exist-i2k7s0/ https://www.pbs.org/video/what-if-singularities-do-not-exist... Echoing JumpCrisscross' sentiment, though. "Disproven" is way too strong of a word.
- wigster 2y ago"kerr black holes" should surely have been "black-kerr holes" ;-)
- empath75 2y agoSabine doesn't even say it's disproven, and the paper doesn't claim that it's disproven, it just claims that one of the earliest proofs that it was a singularity was incorrect. There's an important distinction there. If someone points out a flaw in a proof of the pythagorean theorem, that doesn't mean the theorem is disproved, it just means that the proof was wrong.
- spwa4 2y agoLayman opinion here: If a black hole forms, the point where it forms is an event horizon, but not a singularity. Then, while things get worse, it disappear from the universe. So why would a singularity ever form? And what can't be formed, can't exist.
- rbanffy 2y agoI have the (layman) impression that there is no inside - that spacetime is so stretched around the event horizon that there is no spacetime beyond it. But, then, I've never seen anywhere that the mass of the black hole (which is very much a real thing that exists in spacetime) is distributed over the event horizon, which would be at the biggest amount of mass a given region of spacetime can hold, and is not concentrated on a point with infinite density inside it.
- nh23423fefe 2y agoblack holes have an interior, you wouldn't notice if you passed the event horizon of a large enough black hole.
- spwa4 2y agoWouldn't you? 1) you'd see infinite space dilation. Distance between you and anything would increase to infinity. It doesn't even matter if it's closer to the black hole from you or further away. I wonder if it even occurs with things that fall into the black hole with you. 2) You'd see time pass infinitely fast. I'd say "behind you", but not really of course: anything already fallen in you wouldn't see, and you wouldn't see anything exactly at the same position as you do, so anything you can see would see time pass infinitely fast. You'd be "transported to the end of time". 3) You'd see the whole universe compress into a single point (like in a lens I presume) I wonder if this wouldn't present problems. The whole point of Hawking radiation is that the black hole will stretch out the wave function of light, in both ways (it "transports energy" from the virtual photon falling in to the particle escaping. The particle falling in loses energy, and keeps losing energy forever, while the particle escaping gains energy and since gravity has infinite range, it also keeps gaining energy forever, it's just that the amount decreases exponentially, never quite reaching zero. The particles never quite become real particles, however virtual particles do interact, so I'm not quite sure what makes them virtual, aside from their origin). Wouldn't it stretch out the wave function of any particle? And if you stretch out the wave function of a particle, you reduce it's energy. If you stretch it out infinitely you reduce it's energy, in the limit (but the limit is the event horizon), to zero. And the particles themselves aren't zero size: they would "see" this happen. Even the famous "point-particle" that is the electron has a wave function that occupies a portion of space (in fact, it occupies a surprisingly big volume) So the mass of black holes could be in these frozen particles being teleported to the end of time, while losing energy.
- uoaei 2y agoA more diplomatic and uncontroversial way to put it is that the event horizon is the only thing we have any evidence for.
- oneshtein 2y agoTwo event horizons, because gravitation cancels out in the center of a black hole. ps. Energy is sucked up from the center by second event horizon, but matter is pushed inside, forming a dense and cool crystal, a solid foundation for second order effects to play.
- uoaei 2y agoThat assumes there is gravity, or even universe, "inside" the black hole. We don't have any evidence of that.
- oneshtein 2y agoOccam's razor says that you must present a proof that they are not existing in a black hole.
- JumpCrisscross 2y ago> Occam's razor says that you must present a proof that they are not existing in a black hole Occam’s razor absolutely doesn’t predict that the weird thing that breaks physics occurs twice and then precipitates a crystal.
- oneshtein 2y agoPhysics is fine, it just model, which breaks. However, we can see that stars are eaten by black holes, and then can be partially released back years later, so it's proven that 1) «an event horizon» exists, 2) matter can pass the «event horizon» in both directions, 3) light cannot pass the «event horizon» in one direction. I do not introduce a new physics, like a «singularity», without any evidence. Occam's razor is in my hands now.
- mr_mitm 2y agoThey are singularities in the framework of general relativity, i.e. while ignoring quantum mechanics. I think most people expect the right version of quantum gravity to make the singularities go away, but studying classical GR is worth it on its own, so it's often ignored like in this statement you quoted.
- goatlover 2y agoWhat if gravity is non-linear and thus collapses the wave function? I think Penrose has suggested gravity as an objective collapse interpretation. The measurement problem still hasn't been resolved, but we observe a classical world around us, despite the fact that decoherence simply spreads the superposition of interacting quantum systems to the world. Gravity could be what prevents the linearity of quantum systems from putting the entire universe into superposition.
- mr_mitm 2y agoGravity is non-linear (as in: the Einstein field equations are non-linear differential equations). That has nothing to do with the measurement problem. Also, the measurement problem is only a problem of the Copenhagen interpretation. It doesn't exist in the many worlds interpretation.
- goatlover 2y agoGravity as in the actual force or field, not the current equations. You mentioned quantizing gravity, a few physicists like Penrose doubt it can be done. MWI is not a consensus, and there are more than two interpretations. Objective collapse theories have also been proposed, at least one involves gravity as the mechanism.
- raattgift 2y agoThe nonlinearity of gravity is obvious even in the solar system - it was discovered because Mercury's orbit, when described with the linear theory of Newton's universal gravitation, behaved as if there were an additional hidden mass between its orbit's periastron point and the sun. Or, if you prefer, summing all the sources of gravitation in the solar system is insufficient for describing all the observed orbits in the solar system. (Indeed, even if you summed all the sources of gravity in the galaxy, you wouldn't get the evolution of the relatively eccentric elliptical orbit of Mercury right.) Precision measurements by satellites around Earth and spacecraft scattered around the solar system reveal the nonlinearity of gravitation, as do precision measurements of systems like Hulse-Taylor and PSR J2222-0137. A linear superposition law for gravitation is consequently unavailable - again, this can be seen in the solar system, where a linear superposition model helped find a real mass (Neptune, where ultimately the telescope targetting was driven by Urbain Le Varrier's detailed study of the orbit of Uranus in the 1840s, assuming the validity of Newtonian gravitation), but misled astronomers into decades of futile searches for "Vulcan", a hypothetical body inside Mercury's orbit. There are a bunch of ways one can capture the nonlinearity of observed gravitation. A nice slogan: gravitation self-gravitates. A nice theoretical framework: Newton-Cartan gravity is great for exploring the failure of linear gravity. An easier theoretical approach: the relativistic two-body effective radial potential energy <https://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity#Effective_radial_potential_energy https://en.wikipedia.org/wiki/Two-body_problem_in_general_re...> or less encyclopedically <https://spaceengine.org/articles/the-anomalous-advance-of-the-perihelion-of-mercury/ https://spaceengine.org/articles/the-anomalous-advance-of-th...> where you can see the same effective potential term written slightly differently, with more about Mercury's orbit. Quoting the latter: Again I don't want to get lost in math, but it's worthwhile just to look briefly at what the math is saying here. Notice this still has the exact same two terms from the Newtonian effective potential: an attraction that goes as -1/r, and a repulsion that goes as +1/r^2. But a new term is added: another attractive term that goes as -1/r^3. This means that at very small radii, the -1/r^3 term dominates, and gravitation becomes attractive again, dominating even over the centrifugal effect of your orbital velocity. The increased attraction mimics an additional mass in a linear theory. No linear theory of gravitation is viable for known planetary and astrophysics. At best one can come up with a quasi-linear theory. This is calculationally unfortunate: solving the full nonlinear Einstein Field Equations exactly is fiendishly hard. Where one can use a linear approximation, essentially every physicist would choose to do so. Indeed, Einstein invented linearized gravity (and various other approximation techniques). Unfortunately, linear theories of gravity can only ever be approximate, as they fail to deal with multibody systems, systems where orbital velocities are even only thousands of kilometres per second, where one wants to trace out radiation (including gravitational radiation), and so forth. Convincing proof of incompatibility between any possible linear theories of gravity and numerous observed physical orbits have been known since the 1960s. Roman Sexl did some really interesting work (alone and with collaborators like Otto Nachtmann) in that area in that decade. These days one can turn to box 7.1 (sec. H) of Misner Thorne & Wheeler as a textbook starting point. None of this really has anything to do with quantum mechanics, except with respect to a correspondence principle (e.g. Fraunhofer-like spectral lines have their origin in quantum mechanics, and we can see how gravity rather than just motion affects them).
- pdonis 2y agoIn the GR model of black holes, the singularity is at the end of time inside the hole, not the beginning.