These are awesome. I’ve listened to probably over a 100 vids on physics, but these go a level deeper, with the actual physicists debating and explaining their ideas in a highly technical yet still understandable frame. And there’s host interjecting at appropriate moments to summarize and clarify a point when it gets too condensed. Kudos!
Regarding the Higgs particle in Loop Quantum Gravity (at around 1:05:00) I've done two articles regarding that (and also my thesis). The short answer is that not only you can define spontaneous symmetry breaking in loop quantum gravity, but you can arrive to a theory which does not require a Higgs particle at all to describe massive vector fields. Since youtube dows not like links in the comments I will provide the titles of both my articles and my thesis. If you google them you will probably end up with very few results. The Proca-field in Loop Quantum Gravity Spontaneous symmetry breaking in Loop Quantum Gravity Massive vector fields in loop quantum gravity
1) First I want thank skydevil for publishing this video. 2) I wish that David would let Carlo speak from time to time. I want hear what he has to say. David seems to be a bad listener, a big shame. If he did not want to dialogue and only give a conference, just organize a conference for David. This is very disappointing. David speaks for Carlo. He does let not Carlo speak. That is certainly bad manners. David does not let Carlo finish. It looks like a political show, "vote for me" kind of game, and very little interest on what Carlo has to say.
I was somewhat disappointed that David Gross did not allow Carlo to fully explain his full points before diving in. I think this should have been done by Phil, allowing each person to present and counter separately and then finally debate. Carlo was impeccably polite and complimentary as ever.
Good job Phil. I feel we need more such civilized debates of polarized issues in society. These guys definitely need to talk, and LISTEN to each other, more often. My current appreciation of both sides is that they are elegant storytelling. It will be interesting to see how it all unfolds in the future…
I never knew there is this much tension between loops and strings, discussion was hard to moderate seemingly. My sympathy goes to Rovelli, who at least tries to keep discussion open, whence Gross is more on the established convention and declarative side of authorian science philosophy. That feels so last century in the current potentiality of debates we could have. But, I enjoyd and decided to listen a few more times and share to my friends interested in topics.
To be fair you should not paint Gross as so "authoritarian". The orthodoxy will alwyas defend itself, if not then it's not the orthodoxy. I am not a big M-theory fan, but Rovelli, Smolin, Loll and the others have not given us much else, you realize all the "discrete space" approaches are only theories of gravity right? They tell us nothing about the Standard Model. M-theory at least has oodles of gauge fields in it's spectrum, the problem really being too much crap on top. To my mind, the value of these discussions is in keeping young budding theoreticians and experimentalists eyes & minds open. If supersymmetry can be experimentally ruled out then it'd be one of the most amazing discoveries in the modern era, bigger than the Higgs. One of the greatest negative discoveries ever, akin to Michelson & Morley finding no aether. So the experimentalists have to get involved here, and figure out how to get beyond the LHC.
@@Achrononmaster This is not the first interview I listened about both guys. Former gave very similar impression. Orthodoxy there is certainly, and school books are always outdated what comes to latest achievements. This also makes the argumentation difficult in these issues. Gross commented on something that he was not involved for a decade and where Rovelli is doing his active research. How would you debate constructively in such situation? I do think that Rovelli and Smolin have given much for the community. Their work is important by other means than Nobel, which sometimes becomes obstacle in the progress rather than a sign of the constant development.
Thank you Phil for bringing this debate to us. I enjoyed it a lot but as a physicist i would have preferred you to let them go more into detail! Cheers
Thank you for your comment. , I appreciate that but there are also a lot fp pope interested in physics but not physicists ,so i was trying to cater to them.
Wow you are getting some amazing guests lately! Love the debates! If I may attempt to constructively critique: you often asked the guests to “explain X bc people won’t know what that means”. 1) this wastes valuable time. It results in less info and less depth. We want to know what these titans think about deep things; we don’t need them to spend their time giving definitions off the top of their head when people can look up the precise definitions online. I imagine others are like me and are used to pausing to look things up and we want the nitty gritty technical conversation. 2) if someone really doesn’t know what a topic is, will a 10 second definition really be helpful for them to properly follow along? I think the majority of the time doing this is disruptive to the flow of the conversation and pointless in a time when we can pause YT and have Wikipedia access to get a general idea of any topic we are unfamiliar with. And for every person you are helping with these “explain X” stops, I wonder for how many of your viewers you are wasting their time.
Ive had a few people say this, so i will reconsider next time . But i think a scientific American article eowuld explain these terms and that is the audience Im gong for , not just physics graduates.
@@PhilHalper1 I am with Phil here. The extra explanations are short enough and not disruptive. It is important for the non physicists in the audience to know that they are welcome. This is more important than how informative the explanation actually is. So well done Phil, from my point of view.
@@PhilHalper1 Great physicists are typically great science communicators as well. They often have a unique way of explaining known phenomena so you can gain insight even if you already knew the subject they are explaining before hand. I wouldn't give this up in the future debates/interviews.
Very cool format. It was great to see them squirm in their seats trying to let each other talk! Love the tension. Its a wonderful change from the expert panels where everyone agrees.
Check out the Theory of Everything podcast with Curt Jaimungal. Same format although, instead of a debates he hosts theolocutions where guests are more encouraged to genuinely consider the other perspective and aren't anywhere near as arrogant, which is nice. :p
The problem is that Rovelli keep making factual mistakes but in a serene tone. Gross was getting too emotional, and sometimes with reason since it hurts to listen such mistakes, specially if your brain is trained to avoid as many mistakes as possible.
Great job as an interviewer and mediator. But it would be nice if you allowed them to dive deep into the technical stuff so that we the layman can research further and learn. Thanks
David just didn't understand that Carlo says that LQG is trying just to quantize gravity and doesn't turn off gauge bosons or matter and so on because it's just like Su(3) that's not unified to the electroweak part of the standard model. As a result LQG is consistent at this level. The other point is that there are arguments , very strong arguments, that LQG reproduces the classical limit of General relativity. So I agree totally with Carlo that string theory it's just useless. Wonderful mathematics but isn't supported by evidence in a concrete way: cosmological constant is positive and not negative, there's no supersymmetry that has been proven and a lot of problems with compactified dimensions. Calabi-Yau manifolds gives 3 complex dimensions, i.e. 6 more real dimensions, to add to the usual 4 dimensions of our space time that haven't been detected ever and probably will not be.
Wow great to see Gross & Rovelli go at it, thank you to all involved. It's interesting to see 2 very intelligent individuals have such different creative ideas/opinions about physics. I think such a huge & complex subject is hard to squeeze into 1 video. Perhaps a more structured format would of been better with it split over a few videos but i really enjoyed it thank you.
I came to this discussion since I follow Rovelli on social, so I’m biased towards his position. This was thoroughly run in the spirit of inquiry, IMHO., and thank you for always attempting to bring it to layman’s terms Thank you so much for organizing this stellar discussion- even of it did get Saturnian in parts, it’s been wholly illuminating 💡
This conversation was a hoot and the moderator did a fantastic job. I don't quite understand why so many of the commenters are so angry at Gross (and some at Rovelli). This is exactly what a vigorous exchange of idea between two extremely intelligent and knowledgeable people should sound like; and in the current era of polarisation, culture wars and mud slinging, it is a delight to hear it.
I loved the comically barbed compliments of each other at the end: Carlo compares David to Einstein who was famously productive when younger but lost his way a bit in later years, David compliments Carlo on his endeavours in physical theory but says he is more impressive in his philosophical travails. A wonderful podcast indeed.
Despite the at times unruly disagreements the honesty of the arguments is unquestionable and shines through brightly, which made this an amazingly helpful discussion. Very well done for promoting such an interesting and valuable debate (Thank you from Portugal).
Thanks for this, I’m hoping to get into quantum mechanics later in life (I’m only 17 right now) and it’s great to see there’s plenty of discussion to be had if I get there. Also I think it’s great that you try to rephrase things in a way that the public can understand. I get that as a physicist it’s probably easy go down a rabbit hole of complex jargon but it doesn’t always make for good viewing. I hope you keep it up in the future :)
It was one of the most enjoyable discussions in physics I have ever listened to. Really awesome idea and I would only hope that it will be continued in the near future
Actually, it's depressing. Gross is arguing in favour of a totally failed research programme. Nothing awesome about that. At least the LQG guy is honest.
@@PhilHalper1 yes it was a lecture Nima gave at the Niels Bohr institute, check out the beginning, he interrupted him so often, I don’t know he stayed so cool . David Gross was being so argumentative. Bad behaviour from a Nobel laureate.
I dont like people who are sooooo sensitive when people are interrupting each other … thats how a discussion goes. Also the entire time Carlos explained what his review of string theory was about … David didnt interrupt at all. So dont be so sensitive its redicules
@@MrSamialbeikgenerally that’s how discussions are but this is a public debate, there must be decorum so that the audience too can follow and fully understand each person’s position. Also there’s a difference between debate and argument- debate has rules. Gross generally didn’t follow those rules and kept interrupting (mostly)
@@nysewerrat6577 so what? Is he not allowed to look like someone having to go to the bathroom? You admited that he didnt interupt verbally, but aparently he has to look a certain Way while waiting to respond - otherwise its considered rude . 😂 the world doesnt have to adapt to your needs of what facial expression one has to have while waiting 😂.
Great debate! Not as high quality as the Guth/Penrose one: as many comments noted, David was monopolizing the time, but that was to be expected from him; he probably does not realize that this actually does a disservice to his point of view. I also support the comments that it was not necessary to get them to explain "for laypersons" some of the terms they used; this just took up unnecessary time. In any event, looking forward to more debates of this kind.
A very fundamental problem in quantum gravity is that the action in GR depends only on the energy/matter/momentum distribution, so when you have to consider all fields and physics going on to solve an isolated problem like quantum gravity in absence of a precise description of the fields and stuff in space you run into problems pretty fast, there is no way to separate what happens at high energy with gravity from what happens at high energy in qed or qcd for example, they are attracted at the hip in a tricky way.
Gauge-gravity dualities do offer ways to tackle high energy - the bulk gravity is dual to low energy QFT on the boundary. The real problem being we do not live in AdS. So they are not "attached at the hip" more like attached head-to-toe
Thank you for taking the time to put this debate together, may be a follow up with Carlo Rovelli would be interesting. English is not his first language which allowed David Gross an advantage. David should learn to turn off his email notification chime. It seemed a little intrusive.
Gross is defensive of string theory because it forms part of his ego. It's hard to be objective when your identity is so highly entangled with a given framework.
Honestly though, if we had done what Gross did we would all be defending string/M-theory even more vociferously. Human nature, you defend your tribe, even when they are dicks.
@@Achrononmaster Fair enough, but let's follow through with your analogy. Human nature, you get tired of having to defend a bunch of dicks and go find a new tribe or just embrace it and become a dick. It's sad but another human nature seems to be that it gets harder to consider new ideas or question one's own beliefs as we age. Science advances one funeral at a time sadly. Adapt or GTFO
I have an amateurish question: If there is a smallest distance and space is "pixelated", is there a force that binds those pixels together? Like the strong force with quarks?
Good point. It is not pixelated as far as physicists can tell: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-nyPdIBnWOCM.html. Furthermore, i believe, what we perceive as an empty space is a conglomerate of particles.
A funny thing to note is the fact that Rovelli's approach is that of a physicist who builds theories starting from solid foundations, the methodology used to build the mathematics that describes the LQG stems from a canonical quantization. The solution of the loops is the solution of the wheeler dewitt equation which gives a quantum interpretation to the GR. David Gross says instead that string theory arises from a mathematical formalism that solves the problems of infinity that you have working on a small scale, turns a mathematical tool that solves a calculation problem into the model of a theory, the funny thing is that Gross speaks of a classical derivation of his theory, but this is not true. The funny thing is that he doesn't believe it either, in fact he repeats it over and over again like a mantra. Congratulations to the moderator who directed the discussion flawlessly.
Disagree. He was very specific in his points. Rovelli glossed over Gross’s criticisms whereas Gross addressed Rovelli’s critiques with specific responses.
Very valuable. A bit too heated at moments; I don't like interruptions, even interruptions of interruptions; maybe a chess clock would help. Apart from that, good job - a good topic, a good choice of speakers and good interventions like requests to outline technical terms (e.g. holography, AdS, CFT, renormalization etc).
In my opinion the main advantage of Quantum Loop Theory over String Theory is that QLT ist (gravitational) background independent and String Theory is not !
Fascinating discussion. I have to say that Mr. Halper did a yeoman's job attempting to keep the debate on point, particularly with Mr. Gross's constant interruptions. His body language, in fact, was horrible. Mr. Roveli, by contrast, was far more gracious, and eventually did become frustrated. I think decorum would have gone a long way to make the debate even more informative and applaud Mr. Halper for his efforts to do just that.
@@PhilHalper1 yes phil you did a very good job. But it was a set up. Roveli was gunning for Gross. The top dog. Haha "...the loopy guys..." Looking forward to Roveli explain why Loop Theory is superior....
@@PhilHalper1 How would you feel about muting their screens and only having one person talking at a time? Or at least having control over muting them when interruptions occur. I think that this would help the conversation be more understandable to listeners. Or would it affect the natural back and forth nature of the discussion?
From a physics standpoint, I think you are seeing Gross attempting to explain why he wasn't right about string theory. Of course without actually admitting it.
Constructing the standard model in an LQG background is just a nightmare. Part of the reason is how LQG treats spacetime on quantization. Putting a quantum field on such a spacetime then requires additional non-local corrections to restore Lorentz invariance. While perhaps one can still force their way through but I believe inconsistencies won't really stop popping up. The construction itself does not feel natural. Strings on the other hand is surprisingly tightly constrained and yet works without putting anything by hand into the theory. It just feels as natural as QFT in its respective regime. Moreover string theory actually replicates features of standard model in surprising detail even without heavy analysis. Yes there's the landscape, but it can actually be shown to contain models with a cosmological constant as small as ours using Flux compactification. For those who don't know, compared to the Planckian units the observed cosmological constant is smaller by 10^-123. That's an insane small number and honestly has every right to just not be present had the number of string vacuas been small in the landscape given that string units are closer to Planckian units. But because of the large number of vacuas it does exist. Counting the microstates of blackholes in string theory actually gives the correct (in fact exact) value of entropy to zeroth order as was shown by Hawking and Bekenstein. Granted this has quantitatively been shown only for BPS blackholes but that is by no means a small feat. The same can't be said for LQG. The original calculation of blackhole entropy had to be done by fixing the Immirzi parameter and in fact by cutting out the entire interior, which sort of beats the point for me. I haven't checked the new calculations so can't comment on that. Out of all this I feel the biggest success of string theory has to be the deep understanding of dualities (AdS/CFT and holography being just one derived example). Via compactifications of a newer more powerful formulation of type IIB strings, called F-Theory, we can now study dualities between different types of quantum field theories, one of which the Montonen Olive duality, was predicted independent of string theory in 1977. Of course there's more application of dualities, specifically as David said in the holographic formulation of QCD. Another field which is at its infancy but I believe might have something of substance is a proposal of trying to understand deep learning using AdS/CFT. All of this would have been impossible without string theory. Finally supersymmetry isn't something string theorists (or even particle phenomenologists with realistic expectations) expect to observe at TeV scales of the LHC. String scale as I said is close to Planck scale, so the supersymmetry of strings lives in the Planck regime. I can keep on writing but I guess one really needs to study it for themselves to truly understand the essence of all this.
I am watching the discussion after the fact (not live). As I listen to Prof. Gross say that string theory is like QFT, I am confused because my understanding is that string theory quantizes one dimensional objects (strings; position as function of parameter along the string and time) whereas QFT quantizes fields (field value as a function of space and time). In QFT a particle is a "wave" on top of the vaccum state of the field. On the other hand, I haven't seen strings referred to as excitations on top of some field. Also, in QFT there are virtual particles. Are there virtual strings?
Well, one of the unfortunate developments over the past decade is that many string theorists have redefined string theory to basically mean "everything that self-identified string theorists do" rather than the string theory studied back in the 80s and 90s, with strings and higher-dimensional branes. So today, for example, self-identified string theorists frequently study conformal field theories, and they would argue that they are doing string theory, but CFTs are really a special class of QFTs rather than being a type of string theory. This arose because string theorists have largely failed to construct a string theory compatible with our universe and experimental evidence, and thus have moved on to other more fruitful ventures (CFT, holography, condensed matter, quantum information), but are for some reason unwilling to stop identifying as 'string theorists' and accurately label their current field of study.
A)ADS-CFT duality act as a dictionary to translate from string theory to QFT. B) same can be used to translate back full LQG as a background theory, and on the string theory side arrive at a theory of network of closed strings serving as a background. A string and a loop can be the same wordvolume but interpreted with different Wilson lines. Whereas the corresponding QFT dwell on the surface of that worldvolume. C) Sometimes a pair of virtual particles can be interpreted as a short lived open string or a closed loop in time direction.
You are misunderstanding the purpose of what is known as QFT (and it is forgivable, because there have been some culprits like Carroll and Tong who have gone around giving old-fashioned incorrect presentations on this point). So let me clarify: Even though it is described as "quantizing fields", that is a statement about a convenient mathematical description to help one understand local interactions between quantum PARTICLES. To put it differently, what people refer to as QFT is just a technical way of referring to the consistent unification of special relativity and quantum mechanics applied to particles. So Gross is right. String theory is analogous to more familiar physics. Instead of particles, it is strings, and both obey the rules of quantum mechanics. While the "field" is a convenient book keeping device to describe local interactions between large numbers of identical particles. Furthermore, there is indeed another mathematical subject known as "string field theory", where you might view a string as an excitation of a field. But remember, like particles, it is the strings that are fundamental. The fields are always pure formalism and never measurable, even in principle.
Carlo so feisty! Bit tense sometimes 😅 but sort of a little universe of science, intellectualism, passion, career, ego, culture, legacy (and oh yes physics and unified field theory) contained in one video. Great match up producing a seminal discussion that delineates the issues, conflicts and even confluences of these two, er, loops/strands of theorists.
As a layperson all I know is the jargon. String theory does not begin with Einstein's equations but yet produces a spin 2 massless particle, the graviton. However string theory's description of gravity is perturbative (around the Minkowski spacetime background) while LQG is "background independent." String theory incorporates all particles and interactions of particle physics, while LQG is about gravity/spacetime alone (though matter fields can be incorporated in the QFT way). String theory invokes supersymmetry (susy) which is under pressure due to lack of finding it at the energies of the LHC. However, susy may appear at higher energies or longer-lived decays. In some aspects strings and LQG seem to converge: the AdS-CFT correspondence and the Ryu-Takayanagi conjecture which pertain to a non-perturbative special case in string theory (??).
Foam is made of bubbles and bubbles are spheres. If you imagine spheres being inflated at the speed of light, and overlapping, then you can use such a model to describe spacetime.
Well handled, Phil! With regards to criticism, I felt that David was more equipped with established mathematical results of string theory and Carlo responded to criticism with just ideas that are maybe in research but not in the literature.
Should I be under the impression that a lot of Gross' criticism is outdated? Like the low-energy limit, fermions etc, which Rovelli said now have solutions in LQG, but sadly that idea wasn't expanded as well as stringy ideas such as the holographic principle for example. This didn't offer too satisfactory of an explanation of why they're against LQG since Rovelli's response to some of the most important objectives was "no, we now have a solution" or something like that. Okay, any further criticism on that solution? I wish they went into spinfoam theory at least a bit too, since apparently that's crucial to understand why LQG makes sense or potentially why it doesn't.
Note that the Cosmological Constant "problem" is only a problem from a QFT perspective. In General Relativity its value is simply not surprising and it is not particularly. small. (The reason for that is that it is a _constant_ in GR and so in an expanding universe, where other densities shrink with time, its role will grow until it starts to dominate.)
There was lots of good stuff in here, but it would have been better if david would have let carlo get a word in edgeways. i'm not entirely convinced that this was particularly approachable for people who don't know about a lot of the advanced topics in modern physics. there was a *lot* of terminology. even a couple of things i'm going to have to go and look up before i rewatch it.
I agree David did speak to much. if i could redo it I would have tried to do more about that. And yes I told Carlo and David to try and make it accessible to a Scientific American readership. but I think they were very excited to talk to each other and naturally they fell back to the language of professional physics.
Request to you❤: Suppose: we managed to “improve” the Michelson-Morley experiment so that with its help the result of the experiment was determined; speed on an airplane is 300, 350, 400 meters per second. Question for you: what kind of surprise will this be for BIG SCIENCE?
I think both of them did a good job in this conversation. I just happen to lean towards thinking David Gross has bet on the better horse here. For good reasons. But let’s all keep on working on the problems, following our noses and we’ll see where we end up.
@@lepidoptera9337 Ok, maybe that was a bit vague (though it is just a RU-vid comment). Let me clarify. I think both String theory and LQG and other things are worth exploring and there are lots of theoretical questions with each alternative that needs to be solved. That doesn’t mean there is perfect symmetry between the two options. But solving such issues is what I mean by working on the problems. That would also include trying to differentiate between the options on empirical grounds eventually. The “following our noses” is the part where reasonable people disagree. There obviously are differing intuitions about what will turn out to be most useful in the end and there might not be enough empirical guide right now to unambiguously decide. There is some space there to pursue different directions and people do so. My current best judgement is that ST is more fruitful than LQG. I’m not motivating that, just stating my opinion. Neither have I given you any particular reason to care about my opinion so if you don’t that’s fine.
@@HyperFocusMarshmallow Theoretical questions matter very little in science. The actual problem is entirely on the observational and experimental side. There is no good observational motivation for either string theory or LQG. They are just two random line of thoughts that have established themselves. String theory was originally supposed to explain the hadron spectrum and it failed at that and then it got repurposed and it failed at that, too. LQG didn't even have that false motivation. Neither do double copy gravity, massive gravitons and all the other nonsensical approaches that people are trying out of desperation. Until there will be precision data that shows deviations from Einstein's equations proportional to Planck's constant, there will be no theory of quantum gravity. Period.
@@lepidoptera9337 I’d say there can be a tonne of theories and we don’t know for certain which if any is right. They are just the list of hypotheses. But we are allowed to theoretically explore and adjust our best guess according to what we learn. The different lines of thought are not random. Nor are they nonsensical. Well some might be, I don’t know, but a theory could be very sensical and yet turn out to be wrong. The problem with our currently accepted theories are that beyond a certain scale they are already theoretically nonsensical yet they appear to be right for what we can observe so far. So we kind of want to find some framework that does make sense. There are lots of things one can try theoretically that simply doesn’t work, so theoretical considerations does rule out some alternatives. In fact it’s fairly discriminating. But there will very likely be freedom left that only new experiments or observation will discriminate between and maybe even that won’t be enough. The history and original motivations for studying a structure matters little for what the theory becomes. How do you think theoretical physics should proceed right now if not by trying out these kinds of ideas and seeing where that leads? 😊 Thanks for the conversation btw, it’s always fun sharing intuitions about these things.
@@HyperFocusMarshmallow A theory is a well confirmed description of scientific observations. What we call "theories" of quantum gravity do not even reach the stage of scientific hypothesis, yet. Until one does, it's really just guesswork. This has happened before in physics, in the 19th century. It took over a century of work between discovery of optical spectra and their qualitative and quantitative explanation.
@@PhilHalper1 Btw Phil you might wanna facilitate a debate between Lee SMolin and Jim Gates on string theory vs Loop Quantum Gravity. Somebody just posted a video of the most recent STRINGS conference where Veneziano, Gross, Witten and Gates basically just dismiss LQG.
Even if one gave them an own youtube channel I do not think they would have soon come to an end; great moderating skill! Nevertheless, one or two follow-ups seem to be required.
Great discussion! It shows how much the communication between these communities is needed. I would like to see an episode devoted to noncommutative geometry, yet another very promising idea which extends the notion of the space to encorporate forces from Standard Model
Quantum Entangled Twisted Tubules: When we draw a sine wave on a blackboard, we are representing spatial curvature. Does a photon transfer spatial curvature from one location to another? Wrap a piece of wire around a pencil and it can produce a 3D coil of wire, much like a spring. When viewed from the side it can look like a two-dimensional sine wave. You could coil the wire with either a right-hand twist, or with a left-hand twist. Could Planck's Constant be proportional to the twist cycles. A photon with a higher frequency has more energy. (More spatial curvature). What if gluons are actually made up of these twisted tubes which become entangled with other tubes to produce quarks. (In the same way twisted electrical extension cords can become entangled.) Therefore, the gluons are actually a part of the quarks. Mesons are made up of two entangled tubes (Quarks/Gluons), while protons and neutrons would be made up of three entangled tubes. (Quarks/Gluons) The "Color Force" would be related to the XYZ coordinates (orientation) of entanglement. "Asymptotic Freedom", and "flux tubes" make sense based on this concept. Neutrinos would be made up of a twisted torus (like a twisted donut) within this model. Gravity is a result of a very small curvature imbalance within atoms. (This is why the force of gravity is so small.) Instead of attempting to explain matter as "particles", this concept attempts to explain matter more in the manner of our current understanding of the space-time curvature of gravity. If an electron has qualities of both a particle and a wave, it cannot be either one. It must be something else. Therefore, a "particle" is actually a structure which stores spatial curvature. Can an electron-positron pair (which are made up of opposite directions of twist) annihilate each other by unwinding into each other producing Gamma Ray photons. Alpha decay occurs when the two protons and two neutrons (which are bound together by entangled tubes), become un-entangled from the rest of the nucleons. Beta decay occurs when the tube of a down quark/gluon in a neutron becomes overtwisted and breaks producing a twisted torus (neutrino) and an up quark, and the ejected electron. Gamma photons are produced when a tube unwinds producing electromagnetic waves.
Hi, Phil! :) Can I ask you a little favor? I'm planing to make a high-quality video (2n part) defending Vilenkin's model of tunneling from nothing against critiques by apologists and others, and there is a paper criticizing his model which unfortunately wasn't mentioned in your video (Before BB 9), and this paper makes some strong points which need to be addressed if the defense is going to be complete. A long time ago I asked Vilenkin, but he did not reply (probably because he doesn't know me). But you know him, so would you mind briefly asking him what are some of his thoughts on the paper? I would appreciate immensely! The paper is _Comments on A Universe from Nothing_ by Ikjyot Singh Kohli.
I appreciate what you are doing but i dont want to bother are interview subjects on every paper that comes out. I have spoken to him recently (in the lats year ) and if I do so again and i see an appropriate opportunity Ill try and bring it up
Great to have Skydivephil back. Debates are nice, but I prefer your pithier and more straightforward didactic pieces. I hope you get them up and running again soon. The graphics help along with the narrative
Thanks. we have made a new documentary that we will premiere in the new year but I have another project that is not for youtube but is taking up most of my time. Im really excited about it and think you will be too but cant reveal any details yet
Добавлю немного комментарий со стороны. Не всегда конечно, но бывает такое, что аргументы одного участника сильны, точны и ясны, а его оппонент ходит кругами и не в состоянии ответить. Второй постоянно привлекает новые слова, даже понятия, уходя от точных ответов, не в состоянии ответить нет, не в состоянии признать неправоту, в нашем случае некорректность и необеспеченность теории струн. И что особенно странно, Дэвид ,как ведущий теоретик в этой теории, полностью соответствует духу, сложившемуся вокруг этой теории. Сторонники теории струн наперебой хвалят ее и обещают прекрасное будущее не давая ничего сегодня, и как оказалось завтра. Сотни тысяч молодых ученых зарывают свой талант в зыбко засасывающий песок этой теории. Миллионы вложены в гранды но отдача только в красивой, достаточно сложной математике, которая очевидно прикладывается не к тому месту. Карло, как джентльмен, пытается сказать это мягко, обтекаемо - но Дэвид непробиваем как носорог. Надо честно признать -теория струн увела на десятки лет направление науки в ложную сторону и пара уже остановиться и признать это. Но авторитет корифеев давит, им продолжают, хотя и с неохотой подчиняться. А мужество Ровелли не боявшего идти наперекор этому камнепаду вызывает восхищение . Карло не просто ученый имеющий в своем активе наиболее передовую на данный момент, хоть и не законченную теорию, Карло борец и именно такие в конце концов побеждают. И в жизни и в науке. I'm adding a little comment from the outside. Not always, of course, but it happens that the arguments of one side are strong, accurate and brilliant, but the opponent goes around in circles with his answers and cannot answer. David uses new words, even concepts, avoiding clear answers, is afraid to answer “no”, and is not ready to admit mistakes. And what is especially strange is that David, as a leading theorist of string theory, is completely consistent with the spirit that has developed around it. Supporters of the theory vied with each other in praising it and promising a wonderful future that did not come yesterday, today, and perhaps tomorrow. Hundreds of thousands of young scientists have lost their talent in the sucking swamp of this theory. Millions are invested in grandees, but the result is only complex mathematics leading to nowhere. Carlo, like a gentleman, tries to say this softly and streamlinedly - but David is as impenetrable as a rhinoceros. Here we must honestly admit that string theory has been leading science in the wrong direction for 50 years. But authoritative luminaries put pressure on the whole world of physicists, forcing them to obey. Rovelli was not afraid to go against this. Carlo is both a true scientist and a fighter. people like him always win both in life and in science.
This was a fascinating discussion to me, and I liked the occasional explanations (I have basic scientific background but not to this level ^^). BTW, Carlo mentioned the time from the beginning of "strings" to now, but I think he could also talk about the time x number of people involved. It seems string theory has been pretty prolific in those terms (at least a lot of money has been assigned to researching it, hasn t it ?)
Yes, but absent actual corruption in NSF funding (granted there is some, but it's not horrific), the string people get more people because they attract more grad students, not just because funders like it better. If grad students fall out of love with M-theory it will not get so much funding. M-theory is a social movement. If it cannot produce more goods or if supersymmetry is ruled out then it'll die, but that won't be a bad thing nor will all the research done in the mean time. It gave rise to Gauge-Gravity duality, which will survive string theory, and that's a huge win for everyone. (Contrary to popular press, the bulk gravity theory does not have to be a SUSY string theory.)
String theory is unconstrained to the degree that there are endless possibilities. It is a paper producing machine that earns physicists promotions. I think that's why it's so popular. Sadly, it could be the biggest waste of time ever devised by physicists. Similarly with the fruitless search for dark matter particles.
David Gross always interrupt Carlo Rovelli. He was not able to have enough chance to reply some criticism. He might have been annoyed but because of his respect to David Gross he did not show his reaction. By the way if you are making a discussion meeting for such a complex subject please expect the followers know enough terminology at least to follow the discussion. No need to explain terminology every time by interrupting the talks.
@@PhilHalper1 by the way I am sorry I have forgetten to thank you for this discussions. Maybe there will be with Penrose and one of String theory scientists or Sabine with one of the theory of everything guys :)
I think neither David nor Carlo didn't like this conversation very much. It was unequal, uncomfortable. But very much valuable for non professional physicist to see the "conflict" in the physics.
I think that saying frameworks are trivial is kind of a silly point to argue, its a bit like saying an instrument is trivial to make but tuning it is the difficult part, and yeah as long as you never tune the instrument it doesn’t matter if the sound is shit, but you need the right instrument to play the themes and sounds that go into a piece of music, building a framework is a bit like building an instrument before you know how to tune it properly, and both string theory and loop quantum gravity tries to do that very same exercise, all frameworks work like this initially and maybe some of them are flawed or can’t be tunes just right by simple interventions, but the exercise itself is necessary either way.
Glad Rovelli went. Ill followed the idea since the loop representation of quantum general relativity by Ahstekar while studying beyond GR. All this years. I'm still convinced with LCQ than Strings. Btw. Are you still active on Physicsforum Skydivephil?
Superb summaries by the host's choice of words. But, I don't think people who don't know the meaning of "observables" will be interested in watching the video up to the 1:21:10 mark. (Not that "observables" in quantum gravity are easy to define though). But still, I guess the audience might be smarter than the host occasionally thinks :p
I find it funny that people in the comments are so fond of Carlo, the majority of those probably don't understand the essence of his arguments (same for David) and justify this preference on the frustration of David. Sure, if you put a flat-earther next to an astronaut and see the latter being annoyed to hell, you might get sympathetic to the flat-earther. It takes a lot of effort to understand the mathematics of both theories (especially string theory), however there are several flaws in a fundamental physical level in LQG that David mentions (and Lubos Motl has documented in countless posts) that most advanced undergraduates in theoretical physics can understand. This is why one community (string theorists) thrives while the other not. As a final note, I want to stress what David mentions since the beginning. The distinction between string theory and quantum field theory has become pointless in the past decade and essentially one thing means the other (e.g. via M5 brane construction, geometric engineering on toric CY3s etc). Finally, note that within string theory there is a big debate on several aspects and struggles (see Vafa's recent papers) but there is good evidence as to why 1. this is the best approach, 2. LQG is not a viable theory of quantum gravity but it is much better than jokes such as CDT or the (essentially dead by now Entropic Gravity).
@@PhilHalper1 I do but I am sure that an expert on LQG can always find a counter argument on what I say. I believe that somebody like Lubos Motl would be much more suitable than me (in the same way a LQG theorist is limited in their understanding of modern string theory). A point I want to make with the previous argument is that this debate is not decidable in a non technical fashion. Stating argument A (eg fermions are compatible with LQG) is not equivalent than providing the actual mathematical formulation of the same statement and this requires a technical discussion.
@@PhilHalper1 Not sure I follow, but surely one should not expect that either is expert in both fields. In any case, reading a popular science book does not teach you any physics. The citations of papers of LQG cannot be compared to those in the broader string theory and the reason is surely not some conspiracy created by a handful of superminds to promote string theory and kill any other “competitor”. There is a deep reason why, and Davids arguments describe this reason.
@@giominor88 when i see book I didn't mean popular book. I meant the textbook on LQG. I agree string theory has more citations but until there is experimental evidence for it I think these questions are still open.
Carlo: calm, not fidgeting, listening more than interrupting, clear about the limitations of the theory he works on. David: irritable, moving unhappily, constantly talking over panelists, admitting almost NO criticism of StrnThr. One looks to me an open minded scientist, the other closer to “scientific arrogance”.
Great to see two giants brought together and debate. Thanks for organising this as I don't think I've seen something like this on other channels besides promoting a particular theory from an expert. Science needs debates to iron out conflicts to move forward and gain concensus. However, this interaction was more a cussing game rather than each side taking away something new. For example, David made constant allegations that LQG doesn't have matter (which I've heard many times from String Theorists), yet Carlo corrected him that he was mistaken. This correction wasn't elaborated, nor acknowledged from what I coukd see from David, and so came across to not be willing to change his views. At least this debate was a start, and hopefully more to follow that helps collaboration between cutting edge physics.
It would be great if these interviews were friendly and constructive conversations rather than a debate. People cling to their views when attacked. Plus, there wouldn’t be as much interruptions if they were on the “same side”, so to speak.
@@bendavis2234 The rather sad or funny thing is that both of these scientists are on the "same side" - the side seeking Truth. Yet act like their views are superior to each others, rather than working together more effectively.
I love these conversations because they promote free thinking and expose different nuances on the understanding of the substance. I 100% agree with David’s comment that what we are doing is looking at the same physical reality form a variety of perspectives. The experimental data determines the boundaries which any alternative perspective must remain consistent with. The Announcement of the Higgs Field was my interest awakening into particular physics and string theory. The perspective I choose to explore Presumes that there is only one prime component to the Universe, that being energy. However Energy exists in two forms, Dynamic Energy and Static Energy. The native form of Dynamic energy is infinite and dimensionless but in the presence of Static or Loop Energy Dynamic energy is constrained to the speed of light. The creation of the Big Bang in this perspective came about when Dynamic Energy spontaneously transitioned to Static energy and in the process Time and Space began. This perspective requires that Dynamic Energy and Static Energy cannot occupy the same space so the Universe is essentially an Energy Emulsion of Dynamic Energy immersed and constrained by a Static Energy field. Matter is effectively a quantity of Dynamic energy attempting to travel through the Static Energy Field but unable to do so due to the amount of it so it becomes deflected into a ball which becomes a quark. In this perspective Dynamic Energy can operate at above light speed within its containment and it is this feature which creates the perceived strong force. The dynamic activity of the particle imparts energy to the Static Energy boundary which affects the broad Static Energy field logarythmically and this energy is essentially Gravity. In this perspective Gravity is actually a repulsion created particles against the broad field of Static Energy. The more matter you have the greater the accumulated energy applied to the field So the Strong Force, the Weak Force and Gravity are all the same mechanism. Electro magnetism on the other hand is induced energy created by the tiny gap created by the geometry of the Proton’s quarks. This gap produces a flux tube loop which is essentially the Proton’s positive charge and the loop to which the electron attaches to the Proton. Magnetism is I suggest a similar induced flux tube created by the geometry of certain atomic Nuclei assemblies rather than a Nucleus on its own. To my thinking String Theory should be looking at the Quantum Field as a loop energy field rather than a wave field. There is no doubt that unconstrained energy wants to travel in straight lines as fast as space will allow it to, which we see when you smash particles in accelerators or nuclear explosions. So the nature of the energy within quarks is something that would rather be elsewhere and not confined. The essential understanding is the reaction between straight energy (Dynamic Energy) and loop energy (Static Energy) and how that reaction imparts energy to the field. The consequences of this are that the broad field effectively pushes matter together while also pushing bodies of matter apart creating the effect of universal expansion meaning the Dark Energy is effectively the Static Energy Field (Higgs Field), and I speculate further that Dark Matter is in fact Phantom Matter or areas of space with elevated field energy, free floating energy created by the collapse o Neutron Stars where the field energy can no longer contain particle energy and the particle containment expands to an event horizon containing the stars energy in the form of a black hole. In the transition energy goes in both directions some escaping to space and the rest to be confined by an event horizon, however in that transition I speculate the energy imparted to the field by the matter as particles becomes detached as the matter energy boundary area changes dramatically and the difference in confinement energy can relocate.
Gravity in absence of matter is just a lens, how do you quantize a theory that acts upon nothing? You don’t but even gravity without matter will give you a form of matter just by virtue of light interacting with light, giving the lensing effects, but beyond that its hopeless to go on because the matter is already interacting in the context of a fully fleshed out universe and most of the important details of a gravitational theory outside weak lensing in a classical are dependent on the details of the matter as it exists couplings and all.
One of the main arguments in favour of string theory that we're listening all the time is that " it has a nice classical limit: General Relativity", yet, in the case of the infamous firewalls many people from the string theory community were willing to abandon completely the equivalence principle that General Relativity is based on... The same also happens with the proponents of " fuzzballs". Isn't there an obvious contradiction? Its worth noting, also, that the violation of GR / QFT in the above cases is supposed to happen even in spacetime regions with arbitrarily low curvature! Also, their proposed solution to the black hole information problem massively violates relativistic causality/ locality, again, in regions that nothing similar is expected... There is not even the slightest observational indication that such violations are happening, or that will ever happen in our universe.
I used to think that Carlo was a polite chap but he keeps interrupting instead of writing down his points of disagreement and addressing them when it's his turn to speak. Same for David.
