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A singular mind: Roger Penrose on his Nobel Prize
- andrewon 6y ago>Penrose ultimately showed that singularities are inevitable, with the implication that black holes are common in the universe. I'm not familiar with the proof. Did he show that in the THEORY of general relativity, singularity has to exist given our observation of the universe? Or there are something more to it. Would it be possible or plausible that singularity actually does not exist, but just that the theory of general relativity is not a correct description of space/time/matter in small scale? I am thinking in classical theory, when things were treated as point mass/charges, infinity exist in the solution of point sources.
- Koshkin 6y agoWell, a good theory should a) not contradict observations and b) allow to make predictions that are confirmed by subsequent observations. So far GR has been delivering on both points, including singularities, so currently there is no sensible reason to suspect that it is not correct.
- eggy 6y agoHere is an interesting paper that says a collapsing star sheds enough mass to not ever become a black hole or form a singularity. It's from 2014, and still controversial, but interesting, and her math seems to have been reviewed. I will follow this with interest to see how it fares peer review. Evidence of black holes is indirect at the moment, which is OK for now, but it will be interesting to see how it all pans out in the coming years. https://phys.org/news/2014-09-black-holes.html https://phys.org/news/2014-09-black-holes.html
- ChrisLomont 6y agoThere's plenty of papers by others past this one, showing a more accurate model yields black holes, for example [1]. Here's [2] about 25 others. [1] https://arxiv.org/pdf/1609.05775.pdf https://arxiv.org/pdf/1609.05775.pdf [2] https://scholar.google.com/scholar?cites=12026935191450315869&as_sdt=800005&sciodt=0,15&hl=en https://scholar.google.com/scholar?cites=1202693519145031586...
- meowface 6y agoI understand that the existence of black holes is pretty widely believed, now, but how controversial is the idea of true singularities being inside? I know, for example, there's Carlo Rovelli's "Planck star" hypothesis, which posits that the black hole is effectively (from an outside observer's perspective) an extremely slow violent explosion and hits an energy density limit before ever reaching the singularity stage: https://en.m.wikipedia.org/wiki/Planck_star https://en.m.wikipedia.org/wiki/Planck_star
- ChrisLomont 6y ago>but how controversial is the idea of true singularities being inside I don't know any physicist that would believe this. Singularities happen mathematically due to GR being continuous space and time and material, but we know material is not continuous, and it's possible space and time are not also. So pretty much every one I have ever read or talked to about this believes that once GR is corrected for the quantum level, the singularities will go away, since they by definition would require quantum scale behavior, and it's known GR is not a quantized theory. Note that the "Plank star" is a LQG theory, and LQG has so far failed to reproduce much of anything, so it's not clear at all how that will play out. It hasn't even been shown to reproduce GR at the appropriate scales, and it was recently a big deal when LQG was made consistent on a circle. It's no where ready to deal with 4D spacetime yet. My guess is LQG, like so many other theories of gravity, will die out as more and more pieces of it end up disagreeing with experiments.
- meowface 6y agoThanks for the clarification on LQG. As a totally uninformed layman, your description of the singularity was also my understanding. I only brought up the question because this is the second paragraph of the original comment in this sub-thread: >Would it be possible or plausible that singularity actually does not exist, but just that the theory of general relativity is not a correct description of space/time/matter in small scale? I am thinking in classical theory, when things were treated as point mass/charges, infinity exist in the solution of point sources. Basically, I wasn't sure why they were getting so much criticism for this, because it sounded pretty reasonable to me.
- zachf 6y agoIts a short and elegant proof set in pure theoretical general relativity (GR). The idea is that if there’s a sphere of space where if you try to emit light rays and the light rays don’t initially start separating, then they can’t start separating due to gravity, because in classical GR, gravity is always attractive. You can then show that this implies that inside that sphere, spacetime must end, basically because you can’t outrun light. The proof is important because it was previously believed that black holes are not interesting because they require very special perfect conditions to create, like balancing a pencil on its tip is physically possible but requires perfect aim. But these aforementioned spheres are very common and easy to find so it turns out black holes are common too. If you think (as almost every physicist does) that GR is approximately correct to describe reality, but needs fixes at very tiny lengths because of poorly understood quantum effects, the proof does not directly carry over. One immediate problem is that the proof assumes that energy densities are positive, implying that that gravity is universally attractive, which for quantum matter can never be always true for every quantum state (this is a consequence of Reeh-Schlieder, that every QFT contains states with negative energy density). None of this invalidates Penrose’s work. Physicists have always used different physics to describe different scales. Newtonian physics is great to describe most physics on a human scale, but it’s “wrong” in the sense that GR supersedes it. Similarly GR is “wrong” but still approximately right for a ton of questions of cosmology. But if you fall into a black hole, once you wait long enough, we don’t know what will happen. In string theory, there are objects that are black hole-like. It is generally believed that the singularity is “resolved” (not truly present) in string theory but the details are very tricky to work out. It still is true that geometry breaks down near the singularity and whats left is some stringy stuff, something very new and confusing. Of course it might turn out that string theory does not describe our reality either...
- andrewon 6y agoThanks for your reply. Sounds like the proof is an interesting piece to study.
- ssivark 6y agoCould you elaborate why Reeh-Schlieder implies negative energy states? Typically in QM we only care about the spectrum being lower bounded (existence of vacua), and ignoring additive energy constants.
- deeeeplearning 6y agoWhy do random non-experts always think they have poked holes in the most fleshed out scientific theories?
- meowface 6y agoSpeculation and asking questions is fun. Also, as I understand, it's not an uncommon belief among physicists that singularities may just be an artifact of GR being incomplete, kind of like a divide by zero error in the math which doesn't necessarily exist in reality. So I don't think that poster was questioning established science; I believe there's still a lot of open debate and uncertainty about if black hole centers contain infinitely dense singularities or just something that's incredibly but finitely dense. No one knows. There is indeed a common form of arrogant layman skepticism that confidently and ignorantly assumes scientists haven't thought about [some thing], but I don't think this is an example of it.
- deeeeplearning 6y agoThe problem is that the VAST majority of layman "theories" especially in Theoretical Physics fall into the Not Even Wrong category and are totally without merit or worth discussing.
- meowface 6y agoThat's true. But we're also kind of staring at a sheer wall at the moment. No one seems to be making significant theoretical progress in physics, and when the physicists are stumped, it rouses everyone else's curiosity. Personally, I think the more crackpot ideas, the better; as long as they're not presented in a crackpot way (e.g. the proposer having high confidence or even certainty in their random speculation). And even the ones that are not even wrong can at least lead to useful, intellectual discussion so that the proposer can understand the landscape a bit more and at least closer to the "mere wrong" category. Though I also agree it's much better for people to understand the existing state of affairs before proposing things as if the leading experts have somehow never considered [X] when [X] has been talked about for decades.
- coldcode 6y agoI would love to spend several hours talking with Roger Penrose. I too think doodling with your mind on things unrelated to what you are supposed to be doing can have great results but most people fear such thinking as not useful, or simply can't their mind go that far.
- techbio 6y agoIn his case, also doodling with paper and pencil.
- pault 6y agoI wish my newly ex-employer shared your views. :)
- Strilanc 6y agoI had the opportunity to do that, once, after Penrose was invited to give a talk to google's quantum team. He talked about objective orchestrated reduction and consciousness. The talk was interesting because I completely disagreed with it, but the disagreement was only in the starting assumptions. Penrose thinks humans do uncomputable things; I don't. If you ignored that difference, he was making reasonable arguments. Even more so, he was obviously thinking about things clearly and quantitatively. For example, someone on the team had worked out whether or not orchestrated reduction, if it existed, would prevent error corrected quantum computers from working. They wanted to show the result to Penrose. But before they'd shown him their answer, he knew off-hand that the rough order of magnitudes of the effect sizes meant it shouldn't be an issue. Anyways I sat next to him at dinner afterwards. There was lots of conversation around, so it wasn't like there was one topic. I remember trying to debate whether humans were doing uncomputable things or not, but nothing really came of it.
- hycaria 6y agoThe writing was not that great IMO. Would still like to read more about Penrose.
- kmote00 6y agoPersonally, I enjoyed it very much. I thought the essay itself was put together like a set of Penrose tiles: it brought together the disparate aspects of Penrose's iagination and thought-life as if they were polygonal shapes -- all distinct, yet when arranged together they form a beautiful and very satisfying pattern.
- FartyMcFarter 6y ago> ` (...) They keep pushing it to later!’ His big concern about AI isn’t Judgment Day, but rather ‘that people will believe machines actually understand things’. He gives examples of symmetrical chess configurations in which humans consistently outperform computers by abstracting to a higher level This sounds a lot like the usual moving of goalposts whereby "anything computers can do isn't AI, so AI doesn't work". When AI couldn't do anything, chess was supposed to be a demonstration of human intelligence. Now that AI can play chess and other board games, suddenly it needs to solve symmetrical configurations and think "abstractly" (which is left fairly loosely defined).
- bonoboTP 6y agoThe goalposts (as AI was originally envisioned) are still at the same place, at human equivalent performance in general. Depending on what is still not solved, people point out different things at different times to illustrate that we aren't there yet.
- FartyMcFarter 6y agoYou're right, the overall goal is clear to everyone. But progress in AI is often dismissed because it doesn't achieve that final goal, regardless of how impressive the progress is; cf the first part of the quote: > They keep pushing it to later!
- stanfordkid 6y agoThere's something deeper at the core of his observation IMO -- that our consciousness has some connection / dependence to the universes overall notion of symmetry through it's biological make up. His theory of consciousness looks at these quantum microtubules that are found in proteins ... so what he's saying is that maybe there is some sort of computational power within "wet brains", in how those brains relate to the broader environment that is difficult to precisely characterize. Silicon AI is fundamentally incapable of tapping in to these forces due to the lack of such a connection. The point is that the computational power of the brain may be non-local and non-constrained to the physical dimensions or neural capacity of the brain.
- sudhirkhanger 6y agoI am someone who spends enormous amount of time mindlessly skimming through internet glued to my phone. It makes me worry that due to this habit it will be difficult for me to do any novel work due to lack of deep thinking.
- 7373737373 6y agoThere's always the exploration-exploitation tradeoff...
- Method-X 6y agoPlease elaborate... I’m curious.
- 7373737373 6y agoYou often have a choice of either exploring the unknown, with possible but uncertain rewards, or just work with what you already have, and try to exploit it as best as possible. This is a common theme in machine learning and agent simulations, but can be found everywhere. > Exploration involves activities such as search, variation, risk taking, experimentation, discovery, and innovation. Exploitation involves activities such as refinement, efficiency, selection, implementation, and execution (from here: https://journals.sagepub.com/doi/full/10.1177/0256090915599709 https://journals.sagepub.com/doi/full/10.1177/02560909155997...)
- emj 6y agoWell you need to do these stuff: > experimentation, discovery, and innovation. Is the important part, e.g. because of mindlessly surfing around and trying out new cool algorithms/demos made with obsucre tools, I became an expert at testing and integrating things which were not ment to be integrated with each other. That is a usefull skill.. But I can just as often fall into the trap of reiterating cool stories from the internet to other people. That is usually not helpfull. I.e. you need to do your own discoveries as well by trying them, not just share.
- kmote00 6y ago> "When your work, and what you do to avoid it, become the same thing, that’s when the breakthroughs come." Perhaps I need to get a job here at HN to attain my own personal singularity.
- rnkamyar 6y agoThis resonates. I wonder if he writes poetry? Would imagine anyone who naturally writes poetry about their domain expertise would have competitive advantages.
- KingFelix 6y agoHe does a lot of drawing, if you have seen him speak before he uses hand drawn overheads. Its hard sometimes to find venues that even have them! (or they need to borrow one) I have flipped through some of his doodle books from the 50s/60s amazing stuff.
- mikhailfranco 6y agoA sketch of twistor space: https://theportal.wiki/images/1/11/Penrose-Rindler-Clifford-parallels.jpg https://theportal.wiki/images/1/11/Penrose-Rindler-Clifford-... A Penrose slide pack: http://cgpg.gravity.psu.edu/online/Html/Seminars/Fall1998/Penrose/ http://cgpg.gravity.psu.edu/online/Html/Seminars/Fall1998/Pe... For example, slide 19: http://cgpg.gravity.psu.edu/online/Html/Seminars/Fall1998/Penrose/Slides/s19.html http://cgpg.gravity.psu.edu/online/Html/Seminars/Fall1998/Pe... An original manuscript with fully formed illustrations: https://math.ucr.edu/home/baez/penrose/Penrose-TheoryOfQuantizedDirections.pdf https://math.ucr.edu/home/baez/penrose/Penrose-TheoryOfQuant...
- rfreytag 6y agoArchive.org version: https://web.archive.org/web/20201217142228/https://www.spectator.co.uk/article/a-singular-mind-roger-penrose-on-his-nobel-prize https://web.archive.org/web/20201217142228/https://www.spect...
- deleted 6y ago[deleted]
- markc 6y agoTIL: Escher got the visual paradox in "Ascending and Descending" from Penrose.
- Cd00d 6y ago>'When I would talk to someone about an idea, I found myself not understanding a word they were saying.’ Ha! It goes both ways! Penrose gave a colloquium at my institution when I was a graduate student (physics department), and I've often reflected on how it was the most impossible to understand talk I've ever attended. He had multiple overhead projectors going to different screens (and this was in the early 2000s when wet-erase transparencies were already less common), and he kept mixing up the slide order or which projector he wanted them on. Then the geometry was so far beyond my capabilities that getting to the science was impossible.
- justjonathan 6y agoI went to see him give a guest lecture at a university, a few years ago. It was a great disappointment. It was a terrible lecture. I’m not sure anybody who attended got anything out of it other than being close to the “great man“.
- dnprock 6y agoPenrose is probably correct about the limit of AI. We're living in many simulations now. And sometimes we cannot distinguish between reality and simulations. But one thing that stands out is the suffering. It's an important concept in Buddhism, Duḥkha. Suffering may be a key to consciousness. Machines can have minds. But they don't have bodies. They'd never understand reality on their own. The danger is more with humans. They may increasingly connect their own sufferings into machines. They become tools and slaves for machines.
- baja_blast 6y ago>> We're living in many simulations now I mean it's completely possible we are living in a simulation, but the idea that there can be infinite nested simulations or that we could simulate our own universe seems unlikely. I mean think about a program that runs a copy of that program recursively, you'd run out of memory. Now I am aware that some argue that we could be ancestor simulations which would only render what we same like in gaming, BUT! that would mean they would have to simulate billions of minds and a world with physics and fidelity as convincing as our own which would take an insane amount of energy that I can't imagine anyone wanting to do. If we are a simulation then reality is much more complex than our own.
- anu7df 6y agoI never really understood such arguments. Not being combative, just not sure. If we are in a simulation, then why do things like energy matter? Who says those are meaningful in the "real" world. We can only perceive the simulation, so our idea of physics is whatever the simulation creator thought would be nice, no? May be there are things we can infer from this "simulation" about the world one abstraction above, but in nested simulations that would be arbitrary as well.
- vlovich123 6y agoWasn’t there a mathematical proof that if we are in a simulation then the universe stimulating ours must be drastically different? [0] https://www.seeker.com/tech/physicists-prove-that-reality-is-not-a-computer-simulation https://www.seeker.com/tech/physicists-prove-that-reality-is...