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The Man Who Found Post-Quantum Reality: Jonathan Oppenheim
September 26, 2023
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The Economist covers math, physics, philosophy, and AI in a manner that shows how different countries perceive developments and how they impact markets. They recently published a piece on China's new neutrino detector. They cover extending life via mitochondrial transplants, creating an entirely new field of medicine. But it's also not just science, they analyze culture, they analyze finance, economics, business, international affairs across every region.
I'm particularly liking their new insider feature was just launched this month it gives you gives me a front row access to the economist internal editorial debates where senior editors argue through the news with world leaders and policy makers and twice weekly long format shows basically an extremely high quality podcast whether it's scientific innovation or shifting global politics the economist provides comprehensive coverage beyond headlines.
Think Verizon, the best 5G network is expensive? Think again. Bring in your AT&T or T-Mobile bill to a Verizon store today and we'll give you a better deal. Now what to do with your unwanted bills? Ever seen an origami version of the Miami Bull?
Jokes aside, Verizon has the most ways to save on phones and plans where you can get a single line with everything you need. So bring in your bill to your local Miami Verizon store today and we'll give you a better deal. Rankings based on root metric true score report dated 1H2025. Your results may vary. Must provide a post-payment consumer mobile bill dated within the past 45 days. Bill must be in the same name as the person who made the deal. Additional terms apply. Because they're these big communities, you're almost like pushed to attach yourself to one of them and become a string theorist or become a loop quantum gravity person. And
I think that is unfortunate and you could say that we always operate in like a digital universe where if gravity is fundamentally classical there needs to be a lot more noise in the gravitational field in comparison to the quantum case.
Jonathan Oppenheim, a professor of physics at Oxford, centers his work on a new approach for combining quantum principles with gravity, specifically sidestepping mainstream frameworks like loop quantum gravity and string theory. His research instead focuses on the stochastic coupling between gravity and quantum mechanics. This is one of the most dense of all the TOE podcasts in terms of informational content per minute, rivaling that of some of the Karl Friston episodes.
Contrary to the ordinarily trodden path of quantum gravity, which often dominate conversations on unifying quantum mechanics and general relativity, Oppenheim introduces stochastic processes as a new access for inquiry. What ramifications does this have for prevailing theories? We explore that. Jonathan's expertise extends to quantum information, and he's done plenty of work on the quantum version of thermodynamic laws.
Like the second law and the third law, something not explored in this episode, but I can't seem to find it anywhere is the connection between the classical and the quantum by making an equivalence between imaginary periodic time and finite temperature. This is also known as analytic continuation and is often just proposed as an unphysical mathematical scheme rather than a profound connection between quantum field theory and statistical mechanics.
If anyone knows more about the bridge between these two, then please let me know. At the end of this episode, there will be lengthy updates. Always feel free to use the timestamps, which are in every single theories of everything episode to jump to the sections that you're interested in most. Also, if you're interested in submitting a question for Jonathan when he comes on again, or any toe guest from this point forward, we're instituting a new system. You comment with the word query, then a colon, and then your question.
This way, it's easy for me to parse through. OK, if I'm interviewing Jonathan again, I just look at the old Jonathan episode, control F for the word query, and then I find all the questions and I can then submit them to Jonathan in the episode itself, crediting your username, either in the description or orally. My name is Kurt Jaimungal and I have a background in mathematical physics and I use that to analyze the various theories of everything that are out there.
Professor Oppenheim, welcome. You were famous a couple months ago, Oppenheimer, the movie came out, you must have gotten a slew of traffic and interest as well and your quanta
Video, which will be on screen right now. Quantum Magazine also came out around the same time. So a flurry of interest for your approach, I'm sure. Yeah, a little bit. We went to see Barbie instead of Oppenheimer. So you didn't watch Oppenheimer? Not yet. It's on my list. Fantastic. Fantastic movie, man. Did you enjoy Barbie? I did, actually. It was fun. What you enjoy most about it?
I thought it was hilarious. It wasn't a fan of some of the messaging, but I thought it was hilarious. Anyhow. Okay. What are you working on these days and what excites you about it?
Well, we've proposed this theory of gravity, which is meant to reconcile general relativity and quantum theory. And so most of you just be working on that. I do a little bit of quantum information theory as well on the side. But the moment most of my group is working on, you know, that they're kind of what follows from this classical quantum theory.
You used an interesting word, which is reconcile quantum mechanics and general relativity or quantum and gravity. Whereas most people, as you know, most of the physics community would say quantize gravity. Right. As almost a synonym of making gravity and quantum harmonious. So why do you use that word reconcile and not quantize? Well, I mean, so people realized, I guess more than 100 years ago that general relativity, because it's a classical theory, is incompatible with
Quantum Theory.
tells us about geometry on the other side, and they'll say, in almost every lecture on quantum gravity, they'll say, well, you can't have a operator representing matter in quantum theory equal to some classical number representing geometry in general relativity. So that's usually how it's presented. And the usual statement is that we therefore need to quantize gravity in order to make these two things compatible.
To be clear, classical in this case means what? Definite values? I mean, that's a good question. In classical mechanics, objects take a definite value. And for example, if I have a particle, it might have a definite value for its position and a definite value for its momentum. I could also imagine that I have a probability distribution of classical systems. So for example, you might imagine that someone slipped a coin.
and with some probability they prepared a particle to have a certain position in momentum and with some other if the coin comes up say heads they will prepare the particle with one position in momentum and if the coin comes up tails they'll prepare the particle to have a different position and momentum. So classical systems can don't need to be in definite states they can be in a probability distribution of definite states but
We imagine that there's a fact of the matter about them, even though we might not know, you know, what values of position and momentum the system has, it does have those values in some way. Whereas the quantum system, I mean, the main thing about a quantum system is it doesn't even, you know, a particle never actually has a definite position. So that's the one way to see the difference.
Is that a controversial statement? Because there are different quantum theories or interpretations of quantum mechanics where they do. It's just that the wave function represents our knowledge or their hidden variable theories. Right. I mean, so, you know, one of the most famous and I think most important results in physics is Bell's theorem, which essentially says that
At least if you have a local theory, then the particles don't have a position and a momentum. So I think most physicists and most of the lay public is used to Heisenberg's Uncertainty Principle, which says that a particle, we can never know a particle's position and momentum at the same time. And what Bell's theorem says is it goes one step further. It says that the particle doesn't even have a position and a momentum until we measure it.
That assumes that there's a slight caveat to that. You can imagine a theory which is very non-local, which somehow keeps track of the particle's position and momentum. But I think most physicists don't believe that such a theory makes a lot of sense. And so I think most physicists have accepted the fact that the particle doesn't actually have a definite position in momentum. You once said that quantum mechanics, I think quantum mechanics or quantum field theory
comes with plenty of ontological baggage. Yeah, what do you mean by that? Well, I guess I've described myself as a quantum mechanic with a lot of ontological baggage. And the term actually comes, I think, probably coined by Lucien Hardy, who essentially says that if we, you know, he proves some results, which essentially say that if we want to have a hidden variable theory, then the amount of
Information that we need to somehow have, the amount of information that we need to keep track of becomes incredibly large, becomes infinite. So any sort of a hidden variable theory which describes quantum mechanics needs to keep track of a huge amount of information and it calls that ontological baggage.
It's one of the reasons that people tend not to like hidden variable theories. They're rather unwieldy, they have to be non-local, they need to keep track of an infinite amount of information and so it's much easier just to believe in quantum theory. I recall Nima said that, I'm unsure if it's Nima, but someone said that even in general relativity you don't have
Knowing anything with arbitrary accuracy because if you were to know something with like infinite accuracy you'd have to store that somewhere so that information would carry with that energy and that would create a black hole. I mean in some sense you know because if you believe in the continuum then in some ways any particle has an infinite amount of information that's required to really store
store the information about a particle but when we perform measurements we tend to think of our measurements as being relatively weak and not containing you know they don't reveal to us all that information so we're always somehow operating in a kind of an approximate landscape where we don't keep track or we don't even learn you know for example we don't learn the position of a system to arbitrary accuracy to an infinite number of digits we just learn about it to some small number of digits so
some sense, you could say that we always operate in like a digital universe where the amount of digits that we keep track of is not the full is not infinite, but it's some finite precision. Now, a popular topic these days is the simulation hypothesis. And so when you say digital physics, you just mean that there's something discrete about it rather than simulated. Right. I mean, yeah, if this often will just
Often considered like a discrete space versus a continuous space, which has just a finite amount of information. And there's a question about whether that is good enough and is equivalent. Do we ever need to consider systems which have an infinite, which are infinite dimensional and have an infinite amount of information? That's actually a popular topic right now in, you know, for example, string theorists now are spending a lot of time looking at
Von Neumann Algebras and you know can we actually in a field theory really define in a nice way the entropy of a system because that actually you know the continuum is really difficult to define. So in physics we tend to mostly think that we can describe things with just a finite with finite precision and not worry about the fact that you know really
These are continuous systems which really require an infinite amount of information to describe properly. Yeah Nicholas justin also had this argument about there not being a continuum because he said like look let's imagine the electrons classical or just some particle if it's characterized by a real number and most of the time most real numbers are not computable they have an infinite amount of okay.
But then that would mean that the particle would carry with it that information and what does that mean that the particle would carry with it that information it just is just moving along it doesn't have a coordinate we don't think that it carries with it it chooses a basis to describe itself with coordinates. What's exactly meant when someone says that in a continuum a particle would have infinite information carried with it.
Well, I suppose this is just a question of like, if there's a particle out there, could I, is there, can I, if you just ask the question, could I learn, well, I guess one can get quite philosophical here, like does the particle carry an infinite amount of information and I just can't know all of it, or I can only know a finite amount of it, or
Or does it actually just have a finite amount of information? And that's all I need to describe it. And I'm not sure that as physicists, we would necessarily make a big distinction between the two cases. If we can't measure and learn its position to arbitrary accuracy, then does it have a position to arbitrary accuracy? I don't know.
Yeah, you mentioned the word philosophy, philosophical there. What role does and Lucian Hardy, I believe, is a physicist, but also considers himself to be a philosopher. Yeah, well, at least I consider himself to I consider him to be a philosophical end of physics. In some circles, the philosophy of physics is not looked down upon. And then in some it is. And I'd say most it is. Now, in your view, where do you stand? Like, what are the pros and cons of philosophy as applied to physics?
Well, I think if you, right, I mean, I think if you study quantum theory, then there is an element of philosophy about it. I would say that Bell's theorem, which is a theorem in physics, has huge philosophical implications. So it's somehow hard to get away from you. I think if we're doing quantum theory or
Gravity for that matter, I think we're definitely on the boundary of physics and philosophy. I'm not even sure that I would know how to tell you where physics ends and philosophy starts. Now, it's true that there was a time when, say, for example, the interpretations of quantum theory, which is on the philosophical end of
All right, now I want to get to your specific advantage as a quantum informationalist. Is it quantum informationist or quantum informationalist?
Quantum information theorist. Yeah. Okay. So as a quantum information theorist. Okay. Well, actually, let me spell out the way that I see it from the outside. It seems like if you love general relativity, if you're a relativist, the approach that most resonates with you is loop quantum gravity. And then if you're a quantum field theorist, the approach that most resonates with you is string theory. It's like seen as an extension of quantum field theory. And those are the large two broad ones.
But then there's quantum information. So if you go into quantum gravity, sorry for saying the word quantum gravity, but you understand the reconciliation of quantum mechanics and gravity from a quantum information perspective, you generate different ideas, much like you do if you're a relativist versus quantum field theorist. So there's Chiara Marletto, who also came to constructor theory from being in quantum computing slash quantum information. And you have a different approach. So can you talk about the advantages that someone who's trained in quantum information has when
Attempting to make coherent quantum mechanics and gravity. Right. I mean, it's a good question. And I'm not sure how much of it is related to the community of quantum quantum information theory versus the actual study of quantum information theory. But I would I would say that in terms of having a deep understanding of quantum theory, that is, I think,
I think the quantum information theory community and the quantum computation theory community really has a very deep understanding of quantum mechanics. So one of the reasons I got interested in quantum information theory is because I felt I needed to understand quantum theory better. If you come in the
Hi, everyone.
are studying, say, computation, you're interested in classical computation and quantum computation, and you can start thinking about other forms of computation from other, you know, how could you modify our physical laws and how would that change the laws of computation? And so for whatever reason, I think there's a deep understanding of how you can change quantum theory and how you shouldn't change quantum theory.
A good example of that is linearity. If you come from quantum information theory, you know there are certain parts of quantum theory which we wouldn't change. We would want our theory to be linear, meaning that if you flip coins and prepare different sorts of systems, depending on the outcome of the coin toss, then your dynamics shouldn't
shouldn't be sensitive to what the values of those coins are. Or for example, we would say that any theory of nature, if it's a theory that acts on the density matrix of a quantum system, it should make sure that probabilities get mapped to probabilities and then it has certain mathematical properties. So I think the quantum information theory community is just quite used to
considering different sorts of dynamics and what sort of dynamics is allowed. Maybe that comes a little bit because we study things like decoherence and we study quantum systems which interact with other quantum systems like an environment which we ignore and forget about. And so the dynamics is in some sense a bit more general than what is considered in straight up quantum theory that you might learn in an undergraduate quantum mechanics course.
What's the name of the approach? Does it have a name? So it I guess has gone by, you know, it has many names in some sense. So I called it a post quantum theory of classical gravity because gravity is classical, but quantum mechanics is modified slightly. It doesn't need the measurement postulate. So it's like a post quantum theory.
It had been, you know, people have proposed for probably almost as long as there's been an idea that we should quantize gravity. There's also been people who have suggested that maybe gravity could be classical. And so there's something that goes by the name of hybrid gravity or classical quantum gravity that has also existed out there.
Okay, you don't call it by a moniker. You just write papers about it. But when you're referring to it, you don't call it this is classical quantum gravity or this is post because calling it post quantum is a description. It's not like a title like geometric unity or causal dynamic triangulation. What I'm asking for is, is there a title?
I don't yet have a good name, but maybe someone once said that it was a mongrel theory because it's a blend of a quantum theory and a classical theory. I thought about calling it mongrel relativity, but I don't have a good name for it.
For the sake of this discussion, we're going to call it Mongrel Relativity. Why not? I want you to explain what MG is, but do so with the transition of why you don't like the current approaches to making gravity and quantum mechanics cooperate. Well, let's start with that. I wouldn't say I don't like the current approaches. I think I'm more of the view that
There's been this assumption and I think based on some incorrect arguments there's been this assumption that we have to quantize gravity and we started off by starting with the Einstein equation where you have matter on one side which is quantum and it should be equal to something which is classical and that doesn't make sense so people have thought we have to quantize gravity. And there's been a bit of a discussion about that I think in part because
We've spent more than a hundred years of failing to quantize gravity. And so because there's been about this hundred years of failure, one can, you know, it's useful to think, well, is this really the right approach or is it possible that we've gone down and are taking a wrong direction? So I don't know what the correct answer is. I don't know if gravity is quantum or classical or something else.
I suppose my perspective is just that we should, because the arguments that people marshaled claiming that we had to quantize gravity, because those have turned out to be incorrect, I think it's important to revisit the issue and to explore the possibility that maybe gravity could somehow be fundamentally classical. And I think there's some motivation for that. I don't think it is just a random idea that, okay, maybe
Gravity is special and classical. I think there's some, you know, good arguments you can make in favor of not quantizing gravity. So that's my perspective, just that it's possible that it could be classical gravity. And there's some reason to believe that gravity is special and different to the other forces and therefore should remain classical. What would some of those reasons be? So I think that, you know,
Gravity is different from other forces in that it is what Einstein's general relativity tells us is that matter causes space-time to bend and it's that curvature of space-time that is the manifestation of gravity. So we're just following a straight line, we're just free-falling in a geodesic and that's because space-time is curved that gives us the appearance of a force which we call gravity.
Um, but it's, it's the only force which can be described universally as a geometry. So, um, in that way, gravity is, is special. It's, it universally describes as background causal structure, um, which the rest of, you know, which all the other fields live in this arena of this curved background geometry.
And so there's, you know, there are reasons to imagine that that background structure has to be fundamentally classical. And I think one of the main reasons I would give for that is that the causal structure seems to be, which gravity gives us, so it gives us this causal structure. I don't think that we really know how to do quantum theory without that causal structure. At least I don't know any way of doing it.
And we can try and quantize it, but then in some sense, I feel like we lose our legs, we lose all this background structure which we needed in order to perform quantum theory. And is this related to you make a non-canonical choice at some point? Right. And so you lose something that's special about general relativity. That's right. So, you know, you can imagine, I mean, let's just even start with how physicists, you know, like what is physics?
Usually what we do is we specify some system at some initial time and then we ask how does it evolve and predict what's going to happen to it in some future time. And in a quantum theory of gravity, just merely those statements are difficult.
So, for example, if we want to specify the initial state of the system, well, in occurred space time, that's not so easy because you have to find some hypersurface across all of space and you label that and say this represents an initial time slice. That choice is not, you know, there's a number of ways that you can slice up space time into
Some family of hyper surfaces, these spatial couchy surfaces that are kind of evolving in time like this. And you can do that in quantum field theory because you have a definite causal structure. So if I want to say that this curve slice here represent, you know, represents the state of the system at time t equals zero, then that's a well defined statement.
But I don't know how to make that statement if the geometry itself is the thing I'm quantizing because then I don't have that causal structure. Now I can imagine just choosing one and I just choose some particular slice and I then just quantize it as I would any other field theory. But it's
As far as we can, as best we understand, the quantum theory of gravity that we would come up with will be dependent on this choice of how we chose to slice up our space. What if the loop quantum theorist would say, hey, the constraints on such a system in our theory are such that it's independent of this, even though we chose the Cauchy surface, the observables are independent of such foliations. So does that not get over the objection?
Well, so I guess the problem with, you know, so there's two approaches you can do. One is you can say it. One is you can just hope that your theory will be independent of the choices.
You can try and make a completely background independent approach, which is what loop quantum gravity tries to do. And in particular with the spin foam, they use something called spin foam networks, which is the object of interest, and take a background independent approach. And the problem then they face is that they have no idea how to recover
The classical geometry at the end so there's no way of for them to know or they haven't at least been able to show that in some low energy limit they will recover gravity. On the other hand in string theory they can take the other approach where they have a background dependent theory and hope that
They'll be able to either show that it's independent of that choice or come up with a background independent approach. And some would say that a lot of string theory now is something called ADSCFT or holography. And there's some claim that that is to some extent or to a larger extent background independent. So this post quantum theory of yours, can you please describe it?
So the main idea is that you somehow take seriously the idea that maybe we need this classical background structure of space-time and then it has to be classical. And so you just start simply by saying, can we consistently couple classical systems and quantum systems? Is there any way to do that? And at the moment we have
Only two frameworks for physics. We have quantum theory and classical mechanics. We don't really have at the moment any credible other frameworks which are beyond quantum theory, for example. And so the first question you can just ask is, is it possible to consistently couple a quantum system with a classical system? And there's been a huge number of kind of
Approaches to that where people have tried to consistently couple a quantum system with the classical system and Almost all of those have been unsuccessful But actually in you know, the early nire the mid 90s there's there's actually a few examples of such consistent coupling due to Doshi and due to two people named Blanchard and Yajic and
And they found some examples where you can consistently couple a quantum system with a classical system. And so the first thing we had to do was just to say, OK, what is the most general form of dynamics that we can come up with which couples a classical system with a quantum system? So that's the first thing you do is you derive the most general dynamics that could do that. Before we go to the second thing that you do, can you describe what it means to couple?
Right. So we're used to the following coupling between the classical system and the quantum system. You imagine that we are doing a double slit experiment. So we have, say we fire a bunch of electrons or some photons through two slits and they form a diffraction pattern at the far end and they interfere. So we see a nice interference pattern at the screen behind these two slits.
That's a coupling between a quantum system and a classical system because we treat the two slits as classical, we treat the slits, we treat the screen at the back as classical and there's this little photon gun which is firing photons or firing electrons and that's, we treat classically. So, or a particle in a potential, you know, we treat this potential that's sitting there, that's like a classical potential which is produced by a magnetic field or something like that.
We treat that as classical and the particle moves. So that's an example where the classical system exerts a force onto the quantum system. And we do that all the time in physics. So we know very well how to couple a classical system which acts onto a quantum system. What we
didn't know how to do except for these examples that there were these examples in the 90s which curiously were not, I don't think, really known except in a very small community. So the question that you want to address now is can a quantum system back react onto a classical system? Can it exert a force onto a classical system without causing a contradiction?
And there were arguments that were given as to why that will always result in a contradiction. And I think the most famous argument is due to Feynman at one of the first Chapel Hill conferences, these famous conferences that were organized to discuss general relativity.
Actually, on this channel, there's a documentary on the Chapel Hill Conference, particularly with antigravity's connection with quantum gravity. These famous conferences that were organized to discuss general relativity. And the argument was as follows. He imagines a double-stud experiment
and he imagines this particle which you know sometimes you could imagine a particle which goes through slit number one and sometimes it goes through slit number two and then he says well imagine that this particle has a gravitational field and imagine that we measure this gravitational field and imagine that we can measure the gravitational field to arbitrary accuracy then we could by measuring the gravitational field to arbitrary accuracy we can discover
Where this particle is because we measure its gravitational field and then we would know if it went through the left slit or the right slit and if we know whether it went through the left side of the right side then we shouldn't have an interference pattern. Yet we see interference patterns and therefore Feynman argued that you know we would have to quantize the gravitational field. Why can't someone say look we've never done that experiment where we've detected gravitationally whether it's gone through A or B
And if we were to do that, we would see that there would be no interference pattern. Right. That's a good question. And it turns out that if you merely try to write down the state of a quantum system in the classical system such that the classical system knows which, you know, which let the particle went through, then that's enough.
for you not to have an interference pattern. So whether or not you measure the gravitational field, the mere fact of the gravitational field knowing which that the particle went through would be enough to cause the interference pattern to not be there.
And that's the same with like, you know, people often ask about quantum theory, you know, do I have to look at the cat, whether it's dead or alive in order to collapse it? Does a person have to look at it? Well, no, just the environment measuring, you know, the environment measures the cat. And here the gravitational field is measuring the cat and is measuring which that the particle went through. So
If your environment is classical, then just the fact that in theory it could be measured to arbitrary accuracy to determine which that the particle went through, that would be enough to destroy your interference pattern. Thus the conclusion is that the particle is in a superposition, like even a gravitational field is in a superposition? Yeah, that's what Feynman concluded that the gravitational field had to also be in a superposition with the particle. That was the only way to consistently think of the double slit experiment in which the particle
produced a gravitational field because it was a massive particle. Maybe this comes from thinking about things from a quantum information perspective. One thing that we've learned about quantum theory is that the state of the wave function, the quantum state, is more analogous to a classical probability distribution
than it is to say you know a single c number or you know a single position and momentum of a particle. So one way to think of the it's a good analogy you know the ket of a quantum state is a bit analogous to a probability distribution and so and because we think about probability distributions all the time in quantum information theory it's quite natural to
To think about Feynman's no-go argument and to just say, well, wait a second, what if the gravitational field is in a probability distribution of different configurations, then measuring the gravitational field will not determine which that the particle went through. So, for example, if the particle goes through the left slit, it might produce some
random, slightly random gravitational field. And if it goes through the right slit, it will produce a slightly different random distribution of gravitational fields. But because we have a random distribution of two different gravitational fields, measuring the gravitational field does not determine which slit the particle went through. Is the C number supposed to be thought of as a scalar or a complex number like C stands for what?
Oh, sorry. Yeah. So, uh, I guess in this case, when I, when I talk about a C number, I just mean that, uh, sorry, I guess this is in say the context of, uh, looking at Einstein's equation where you have an operator on one side and then that's just, you know, it's just a number, the Einstein tensor. So it's a, it's a single number versus an operator or say a vector, which is, you know, in quantum theory, observables are
operators which act on quantum states which are vectors, whereas in classical mechanics we just have the particles just described by a number. This is the particle's position in momentum. I've heard the term c number, I've heard it, but I've never read it, so I don't know what is the definition of c number. So what's the difference between classical randomness and quantum randomness?
You mentioned it before, but can you briefly outline it once more? Because you're about to make the connection between, well, you're about to explain how randomness solves a harmony issue. Right, right. So a quantum system, so a classical system can be
It can have a probability. So we can imagine, for example, a particle has a position and momentum, and we can also imagine that we have a probability distribution of different positions and momentums. So, you know, there's some probability that the particle has position X equals zero and momentum, you know, 10 units.
We can imagine such a distribution and the probabilities, both of its particular values that the position can take and the values that the momentum can take, those are all positive and they all sum to one if we were to sum them up. On the other hand, a quantum states, we cannot ascribe probabilities to a particular outcome of a position and a momentum measurement. That just doesn't exist.
We can because we're either going to perform the position measurement or we're going to perform the momentum measurement, but we don't perform both. And so the quantum state does not need to be described by a probability distribution over position momentum whose values are all positive. It's describable by something else, which is, you know, it can be described, for example, by something called a Wigner distribution, which looks a lot like a probability distribution except
Its values are not always positive. And that's okay because I will never measure and get a negative probability because I can't measure both the position and the momentum of the particle. So it's okay if a quantum state, if its distribution has negative values, that's not okay for a classical distribution. It has to always have positive values because
You know, the probability that a particle has a particular position momentum needs to be positive. So now what's meant by that? The coupling between gravity or some gravitational system, some classical system and some quantum system has to be stochastic. Also, can you outline what the difference between randomness as stochasticity is? OK, I don't know that there's a so I use those words interchangeably. Maybe there's a more technical
Terminology and maybe they do mean different things, but I tend to use them interchangeably Although I guess when I think of a stochastic process I think of a dynamical process so you know the particle is going through the left slit and in a deterministic theory it would bend space-time in a particular way and in a stochastic theory it would
You know, it almost like flips a coin and depending on the value of the coin, it bends space time in a slightly different way. So you can imagine that there's these coins being tossed all the time, which determines if the particle goes to the left slit and it produces some different gravitational fields with different probabilities. And if it goes through the other slit, the right slit, it will produce some it'll bend space time in some other way. But it's
The way in which it bends space-time is determined not just by which slit it went through but also by it flipping a coin. Now I want to be careful when I say flipping a coin because that one is almost imagining that there is some physical process by which it determines which of these gravitational fields to produce but actually I don't believe that there is actually any physical process which is determining which gravitational field is being produced.
Let's make it simple and imagine that someone's walking through two doors. Does that mean that they're constantly carrying with them a coin? And even before they encounter those two doors, they're flipping it and they're making some other decision. And then when they get to the door, then they flip it and then it's a left right decision. Is this coin just being flipped for them? How does this work? There's no physical process. Yeah, I mean, maybe even another way of saying it is imagine that, um,
Someone's going through the right door, someone goes through the right door or the left door. If I'm far away, I can sit there with a pendulum and I could actually figure out, I could try and figure out which door they went through by trying to measure their gravitational field. But now imagine that at every point in space, the gravitational field is just
Okay, then the way that I'm imagining it is that you have a pendulum and it's
I don't know how the pendulum apparatus is supposed to be when you actually measure, but I'm just going to say that it's completely still. And then you see, does it move slightly to the left or move slightly to the right because it's attracted to the person who goes to the left or to the right. Okay. You're saying that actually if you were to look at that pendulum, it would be constantly jittery because just even without anyone going through the doors. Right. Oh, okay. So what I was about to say is because this not be solved with more precision, but then you would have to do a series of measurements. Yeah.
The most famous gravity measurement is probably the Cavendish experiment where they sit there with this beam with two weights on the end and it's held up by a string and it kind of rotates like this and you use that to measure say the gravitational field of the earth or of two balls of a kilogram mass for example.
If you ever have seen that experiment or you've tried to do it in, say, an undergraduate physics lab, you'll see that the torsion pendulum kind of moves about quite a lot and is jiggling much in the way that we just described. And the reason it's jiggling is mostly because air molecules are hitting it and the system is very noisy and there's heat and we don't have very good control of gusts of air which push and pull the pendulum.
But imagine that we got rid of all those gusts of air and had everything in a perfect vacuum and didn't have any stray electromagnetic fields or gravitational fields around but we cleaned up everything. Would there still be some fundamental noise? And this theory predicts that there will be. And it's this noise which somehow allows interference patterns because
Now the quantum field theorists would say there is noise anyhow because there's some fluctuations. So is there a way of you distinguishing the noise from the fluctuations versus I don't know what type of noise this is called but this post quantum noise? Yeah, that's a very good question and
There is disagreement, so I've had disagreement with some of my colleagues about this, but we've calculated how much noise there has to be and there has to be a lot more noise. If gravity is fundamentally classical, there needs to be a lot more noise in the gravitational field in comparison to the quantum case.
And it's true that in the quantum case you also need some noise there because you can imagine the same experiment, the double slit experiment that I just gave. You can imagine the same argument being made about the electromagnetic field. How is it that if the particle goes through the left slit and the right slit, I can measure the electromagnetic field? And what is it about the electromagnetic field which doesn't allow me to determine which slit the particle went through?
We can't measure the electromagnetic field to arbitrary accuracy. Because the electromagnetic field has a quantum nature, then I can't measure with exact precision the electromagnetic field and say it's conjugate degrees of freedom.
So because we can't measure the electromagnetic field to arbitrary accuracy, we're not able to determine which step the particle went through. Or another way of saying it is this. In quantum mechanics, you can have two different states which cannot be distinguished. In other words, the electromagnetic field will be in a different state depending on whether the particle went through the left slip or the right slip.
But even though the state of electromagnetic field is different, I still can't tell it apart. It has some overlap. There's overlap between the two states and those two states are not orthogonal, we would say. In other words, they can't be distinguished perfectly. And it's because those two different states of the electromagnetic field are not distinguishable. It's that which allows you to still have an interference pattern.
Now, sometimes you don't, right? Sometimes the particle will go through the left slit and it will emit a photon because it happened to hit the wall in a certain way. And if I were to measure that photon, I would be able to determine which slit the particle went through. So there is some decoherence. The interference pattern does get disturbed a little bit by the electromagnetic field, but not by very much. This theory of yours doesn't have predictions. So one prediction I see is that it's a null prediction, namely that there is no graviton.
Right. Does it have other predictions? And am I even correct by saying that there is no gravitation? Right. There's gravitational waves, but there is no quantized particle which is responsible for carrying the gravitational force. And so one of the big predictions is this noise in the gravitational field. So, you know, we predict that you should go into the Cavadish experiment and you will have to see
a large amount of noise in the gravitational field. Now the problem is that there is already a large amount of noise in the gravitational field. If you ask the people at NIST who are responsible for keeping the one kilogram mass and telling us how keeping that and doing these precise measurements of say a one kilogram mass, they will tell you that it's actually very difficult experiment to perform and that their measurements do have quite a large variance.
and inaccuracy. So the experiment we're proposing is higher precision tests of those measurements of say a one kilogram mass in order to put a bound on how much noise there is in the system. I mean what's exciting, even if you, whether or not you believe in, you know, if we, I feel like this question of whether gravity is fundamentally quantum or classical is
a real one and I think what's exciting is that this actually allows us through these precision Cavendish measurements to actually determine whether gravity has a quantum or classical nature. With the noise, if you were to with precision measure the gravitational field, would that noise still be there even in other approaches to harmonizing gravity with quantum mechanics like string theory where you sum over metrics
So like, there is some uncertainties to what the gravitational field is in string theory. So would they say that that should also produce noise or is this noise distinguishable from the noise that you're talking about? So there will be some noise and it has in some ways a similar form, but the amount of it is just much less in a quantum theory. And the reason is, is that in, is, you know,
In classical theory, you can perform in some sense two different experiments. You can do a precision test of gravity and see if there's noise in the gravitational field. And the other thing you can do is you can do an interference experiment. So I can take a gold atom, for example, a very heavy atom, and see if I get an interference pattern. And if you get an interference pattern, you can keep pushing how coherent you can make a gold atom. So I might imagine a gold atom that
can follow two different paths and be in a superposition of these two different paths. If I can keep the gold atom in superposition for a very long time, then it would mean that I need a large amount of noise in the gravitational field in order to keep that coherence. There's a trade-off in some sense between how long I can keep a gold atom in superposition and how much noise there needs to be in the gravitational field in order for the gold atom to keep
Being in a coherent superposition and there's a trade-off between those two things and so I can perform both those experiments and if I can and the longer I'm able to to extend the coherence time of gold atom the more noise I know there must be in the gravitational field if the gravitational field is classical. So between those two experiments you could either rule you know you could potentially say rule out the classical theory of gravity
Whereas in the quantum case, there's no such trade off. You don't need to have, I mean, there's a related trade off, but it's not quite the same. And so it turns out that for a quantum system, if a gravitational field is quantized, then there doesn't need to be nearly as much noise in it. Understood. If one wants to read up more about this, which I'm sure many, many people do, what would be, forgive the pun, the canonical paper of yours to read?
So there's just, you know, I mean, there's a there's a recent quanta article which you mentioned, which is, you know, probably reasonably accessible to a popular audience. I'll put the link to that in the description as well as to the quantum video of yours. Great, thanks. And then, you know, the first article was called a post quantum theory of classical gravity. And that is quite a detailed article, but at least the first two or three pages, you know,
tries to explain this Feynman argument and why it doesn't rule out a classical theory of gravity and then it also discusses one of the big reasons that people disregarded the fact that we could have a classical theory of gravity was that they essentially assumed that having a classical theory of gravity was equivalent to something called the semi-classical Einstein's equation where
Where you just take the expectation value of the stress energy tensor and then stick that into Einstein's equation. And that's been known for a long time to be a pathological equation. If we take it as fundamental, it leads to all kinds of problems. And so people somehow associated semi classical gravity with, you know, with attempts to keep the gravitation field classical.
What's so pathological about it? It doesn't satisfy this principle of linearity, which I said is so important and which I think any theory ought to be linear. When you have a theory which depends on expectation values,
then it allows you to do all kinds of things like superluminarily signal faster than light or in some sense violate the uncertainty principle because if you can measure an average value then that's a pretty weird thing, right? Like in a single go. Here's a way of explaining it. Imagine that I flip a coin and with some probability I put a planet on the right
And with some, so if I get heads, I put the planet on the right. And if I get tails, I put the planet on the left. And now imagine that I have a theory where I am attracted to the expectation value of those two state of affairs. So on average, the planet is neither on the left or the right, it's in the middle.
And so what happens in a theory where you take expectation values is that if I drop a test particle and watch the test particle freefall towards the planets, they will fall straight down the middle between the two places where I would have put the planet. So here's the planet if I get heads, here's the planet if I get tails,
If I take the expectation value, the expectation value is somehow down the middle and that's where the particle falls. And that's of course not what we expect to happen. So a theory where you use expectation values rather than say something else is going to lead you into a world of pain essentially because of that.
In your post quantum theory, is then the conservation of momentum something that is just emergent or not fundamental? Because if you're shooting a particle, let's say a planet, like you mentioned, the planet could go here or there. Does that not then send the planet off to another slightly different trajectory than it was before? So there is a so
The theory conserves momentum, but it doesn't conserve all, you know, there are things which are not conserved in it, which would be conserved in the deterministic theory. So Noether's theorem, which is a famous theorem which connects symmetries with conservation laws, because we believe in time translate, you know, our theories of physics are invariant under a time translation.
And they're also invariant. If we move three meters to the right or three meters to the left, the laws of physics don't change. And that tells us that momentum and energy are conserved. Noether's theorem assumes that the laws of physics are deterministic and are given by a unitary transformation. If they're not, as in these theories, then you don't have the same connection between symmetries and conservation laws.
And it turns out in this theory that because you have lost this connection between symmetry and conservation laws, then energy does not need to be conserved. And so you can get something which may look like some kind of anomalous heating coming from these sorts of theories. Now, in general relativity, energy is very difficult to define in the first place.
understanding what exactly that means to such a theory where you don't really have a locally defined energy. That's another matter, but it's quite complicated in terms of how conservation laws are respected in such a theory. Speaking of laws, you have a paper, I believe it's called the second laws of quantum thermodynamics. So firstly, what is quantum thermodynamics? And then why are there multiple second laws? Right.
When I was an undergrad we were taught that thermodynamics is a theory that you get in the thermodynamic limit. In other words, I have a gas and it has many particles and I take the limit that the volume goes to infinity and that's what thermodynamics is. It's that theory of large systems. But you can ask
What happens to, if I just have to say, a single gas molecule or a single quantum system, does it still obey things which look like the second law? And can I still define some laws of thermodynamics for those systems? And it turns out you can. So for a single particle, the entropy also has to increase.
But it turns out there's a whole bunch of other quantities which has to increase as well. So I can think of, in some sense, the second law of thermodynamics as placing a restriction on what will happen to my system as time goes on. So I know that the entropy has to increase, but there's a bunch of other entropies that you can also define, and it turns out those also have to increase as well.
There's all kinds of entropies which are different to the standard one and it turns out those all have to increase and what happens is as I have more and more particles and as I make my system size grow larger and larger it turns out that all these other second laws and all these other entropies become equivalent to each other and so in the thermodynamic limit I only have one
entropy. But on the small scale, I have a whole bunch of other entropies, which turns out they also obey some kind of a second law. We corresponded over email, you and I, and I spoke about Flaminia, who's also working on quantum information and gravity. And I was curious to what the relationship between her approaches and yours. Right. So so she's her and some of her colleagues have
Proven various theorems about what happens if the gravitational field is classical. And they've done it in a more general framework than we often work in. So they haven't made any assumption. For example, they haven't assumed that matter obeys laws of quantum theory. They've allowed
They're considered more general sorts of interactions. In fact, you can there's all kinds of machinery that has been developed called, say, general. It goes by the name of generalized probabilistic theories, which is a huge class of theories which go beyond quantum theory. And we don't know if they actually exist, these theories or whether they are well defined or not. But you can certainly think about the kinds of some of the properties they may have.
I mentioned these experiments we proposed where we show that if gravity is fundamentally classical, then it has to be stochastic. It has to have randomness. One of the results, for example, is that even if we go beyond quantum theory, if gravity is classical, then it somehow
We'll still have to be stochastic, even if we're able to modify the laws of matter. So if we go beyond quantum theory from the matter distribution. And what about Chiara Marletto? What about constructor theory's relationship to yours? Yeah, so that's another example where she has looked at theories which go beyond quantum theory.
I guess in both cases the claim is being that it rules out the classical theory of gravity but usually there's some assumption for example of reversibility or an assumption of determinism and so what these theorems tend to show is that if we have a classical theory of gravity then they have to be irreversible or have some sort of indeterminism or randomness in them. So I think
This is kind of establishing that if gravity is classical, it has to be stochastic. I think from their point of view that that is so unpalatable that for them and for maybe many other people, it is enough to rule out the classical theory of gravity. So if you believe that the laws of physics should be deterministic and you don't believe in fundamental randomness, then you probably are unlikely to believe that gravity could be classical.
I also spoke to you over email again about a no-go theorem by, I believe it's Marletto, I believe it's her, or maybe she referenced it, but either way, can you talk about what that is and how yours escapes it? Right. So yeah, there's a no-go theorem due to Marletto and Vedral, which essentially
I mean, in some sense, it's related to this Feynman thought experiment we mentioned where we have a particle that is in some superposition and it produces a gravitational field. And if I can measure the gravitational field, then that would seem to determine which that the particle goes through and therefore rules out having an interference pattern. You can imagine that you have some other theory, which is not quantum theory.
And what they've shown is that that argument still holds. But again, there's that loophole that I mentioned where if the gravitational field has some randomness in it, then those sorts of arguments don't rule out classical gravity in that case. So I think the big question is, do we believe? Well, first of all, for me, it has now become an experimental question. We should go out and measure whether gravitational field has randomness in it. If it doesn't,
You know, then we've essentially ruled out a classical theory of gravity. Is it conceivable that we can perform this measurement within the next 20 years or so? Right. I mean, in some sense, we already have placed bounds on such a theory. So, you know, we can it's just a question of how much and I feel like we need to better understand the theory before I would be able to tell you exactly what those numbers are.
Because what we've essentially been able to, it seems that in order to correctly predict how much noise you need in the gravitational field, you need to go, it's a fully relativistic calculation, so you need to go beyond the weak field limit. And so we're still performing those calculations. Now Bohmian mechanics was something else that
I mentioned to you, I'm curious to see the relationship between yours and what's the relationship between your theory and Bohmian mechanics. Right. I mean, there's not there's not an immediate one, but there is. Like, does yours rule out Bohmian mechanics, for instance?
Well, it's hard to see how you could rule out Bohmian. So I guess that's we discussed before this kind of philosophical side of physics, in particular in terms of the measurement theory of, you know, in terms of these various interpretations of quantum mechanics. And so depending on your flavor of Bohmian mechanics or many worlds interpretation or et cetera, you know, many of them are equivalent from a physics point of view.
Although there are flavors of those interpretations or those theories where there is a physical difference between, say, Bohmian mechanics and some other interpretation of quantum theory. What I will say is that the one thing I like about these classical quantum theories
is that you don't need the measurement postulate of quantum theory. So I think one of the reasons we have all this discussion of interpretations of quantum theory is because it's very unsatisfying how quantum theory deals with measurement. And we seem to have
The standard rules of quantum theory where things evolve deterministically and then we perform a measurement and we get the state supposedly collapses and we get a random result and that's not very well understood. On the other hand, in this theory of gravity, in some sense the gravitational field is doing the work for you and is causing states to localize and for the wave function to collapse.
Because the gravitational field is in some sense always measuring where the particle is, one doesn't need to invoke the measurement postulate of quantum mechanics. So in some sense, it's its own interpretation of quantum theory. I see, I see. So for the people who are researching this field of quantum gravity or
Making quantum mechanics coherent with general relativity. What advice do you have for them for people who are going into this field for young people as well? Just entering math and physics for people who are going into specifically what you study and for people who are researching. Right, I mean, so. I think that so I guess one thing I would say is that I feel like the landscape of
of gravity research for example is quite a difficult terrain at the moment in the sense that if you're a student and you want to study say quantum gravity or reconciling gravity with quantum theory there's very few games in town. If you're a graduate student for example you can
work in the string theory group or a loop quantum gravity group. There's a few of those, although that's a much smaller field. And then there's a few of these kind of individual programs which may be involved as a couple, three or four researchers. And it's a very difficult terrain as a student because, you know, the history of physics is that usually it's young people that make, you know, new paradigm shifts or great physics discoveries. And
I feel like it's difficult these days to work on your own stuff. Because there are these big communities, you're almost like pushed to attach yourself to one of them and become a string theorist or become a loop quantum gravity person. I think that is unfortunate and I think
What we really need is people to kind of go off in their own direction and do their own stuff. And I think that invariably will mean attaching yourself to some group, but hopefully being given the freedom to go in a different direction. And I think that's
You really have to find something you're really interested in and maybe a supervisor who has the same interest or you have to somehow go off on your own and that's a lot harder and I fear that is one of the
One of the reasons that it's so difficult to make progress in quantum gravity is part because it's a really hard problem, but in part it's because there's not a large scope for just going off on your own. You are often just, in some sense, drafted into an existing program. When you say that there's not a large scope, you mean there's no funding or there's not opportunities? Well, opportunities equals funding. Well, it's hard to know exactly
Yeah, it's a multifaceted problem. I think part of it is that for whatever reason, people like to work on the same thing as everyone else. And I mean, we are social creatures and we want to be part of the community. And so if there's a big community doing something, then it's very natural to want to be part of that community and do that research. But I feel like it's gotten to quite an extreme
It feels quite extreme at the moment. I feel like even when I was a student, there were various researchers who, I would say, didn't have a firm allegiance to, say, string theory or loop quantum gravity, and you could kind of work with one of them and work on your own approach. Whereas I think now, for whatever reason, the landscape has just become a lot more
divided into different communities who do different things. And it's much harder to go off on your own. And maybe that's just because it's students worry that if they go off on their own, they won't get a job. I think that's probably a big part of it. Speaking of being a student, my brother was a student, a graduate student, or maybe a PhD student at the same time you were studying physics. That's right. Yeah. You remember Sebastian?
Of course I do, yeah. He was brilliant. I think we maybe even have shared an office for a while. I think he was working with Gordon Seminoff, is that right? Yes, right, right, right. Do you say hello to him for me? Yeah, I will. Do you have any teachers that have changed your life or gave you a new perspective, ones that are particularly memorable to you, whether in high school or even in university?
Yeah, I mean... But not your supervisor, because that's obviously... That's obvious, yeah. It's like your father, isn't it? I mean, in high school, I had, I think, a great science teacher, Ping Lai, and so he had a PhD in physics, and I think I learned special relativity from him, and he just gave us a lot of scope to kind of
explore and think about our own things and so that was definitely you know important that I think I had him as a physicist as a physics teacher in high school and you know in elementary school as well I had a really good it wasn't even my science teacher but it was just a teacher that let you just kind of go off on your own and study whatever you wanted and I feel like
that letting letting me and letting other students just do whatever you go off on your own and and study what you want is, I think, a really important part of learning. And for me, obviously, is being able to like, you know, I'm fortunate enough that that kind of way of learning has been able to continue into, you know, my middle age. So that's quite lucky. But I'm definitely grateful that I had teachers who let me who let me do that at a young age.
And before I let you go, I'm curious, what has been the reception since your quanta article from the public and then from the physics community? Um, actually the, you know, I'd have to say that the people have been quite open to it. I feel like, um, there's definitely been, um, especially from the relativist community. Well, I would say even from string theorists, I feel like there's been an openness
Often it's of the form of, well, I don't believe that gravity is classical, but I'm glad that you're, you know, exploring the consequences of that. I'm glad someone is doing that. And so, you know, that's I feel like that's at the at one end. And so there hasn't been there haven't been many people who have who most people have been, I think, quite engaged with the
For me, what is the most exciting engagement I've had is this community of people who are interested in actually performing the experiment. And so that has been exciting in the sense of I think what we're going to see is a large scale effort to test the quantum nature of gravity. Because I think for a while there was always this assumption that in order to test quantum gravity, we needed to go to the Planck scale. We needed to go to incredibly high energies
before we could ever make a prediction about gravity and what we're learning now is that actually there's all kinds of things that you can test for in terms of a quantum theory of gravity which do not require Planck energies. So for example, testing whether gravitons can create entanglement
That's something that doesn't require Planck energies and which we hope is maybe feasible within the next decade or so. So I think that's been the most exciting kind of experimentally. Well, it's been exciting. It's been illuminating to speak to you. Thank you. I appreciate you coming on to the podcast and I look forward to speaking with you again. Likewise. Thanks very much. Appreciate it.
All right. I hope you enjoyed that episode with Jonathan Oppenheim. Something that you should keep in mind is that for this guest and for any of the guests, including all of the backlog of toe, you can leave a question for the guest in this specific format of writing the word query with a colon and then your question.
This applies to any episode, like I mentioned, like if you want to leave a question for Lou Elizondo when he comes on next, if you want to leave a question for Jonathan Oppenheim or Edward Frankel, by the way, the Edward Frankel episode, which is listed on screen now and in the description, in my opinion, is one of the best toe episodes that we've ever recorded. You'll see that we both skirt between technical and personal and emotional and it's super revealing.
We both got more personal in this episode than we've gotten in any other podcast, both of us. Again, Edward Frankel is in the description. I encourage you to listen to at least the halfway point and you won't be disappointed. I've also started this tradition where on every episode or every other episode, I'll highlight a comment and read it because, hey, if you're like me, then you don't have many people to speak to about these subjects outside of conversing online and digitally. This is my way of not only highlighting a certain comment, but also encouraging the community that we've established.
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have been the driving force behind this endeavor. We've built a community that shares a fervor for science and philosophy, and for that, I'm eternally grateful. Truly. Despite our 240,000 subscribers and the vibrant community that we've built, the past 11 months have been challenging. Behind the scenes, our channel has been grappling with financial struggles.
Our content, deeply rooted in science and philosophy, unfortunately falls into a category that doesn't fetch the highest ad revenue on YouTube, to say the least. This isn't just our struggle. Even Sabine Hassenfelder recently mentioned a similar issue. During 2023, I've been working harder than ever, which I didn't think was possible, often at the expense of personal and family time. The effort that goes into each Toh episode is immense. I pour my heart and soul into researching and studying for each episode to ensure that we deliver
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they've simultaneously been the most rapturous of my life it's a blessing thank you dearly man thank you thank you so much after the posting of that letter there's been a flurry of support not only from you from the audience but also from other podcasters coincidentally enough theo von a channel with over two million subscribers just talked about this same issue happening to him
A KFC tale in the pursuit of flavor. The holidays were tricky for the Colonel. He loved people, but he also loved peace and quiet. So he cooked up KFC's $4.99 chicken pot pie.
So yeah, you can keep that money, but you can't get me to shut up, man. You know how many other podcasters wanted to say this shit right now, but can't say it?
The way that people are able to cheat and lie and manipulate the system. Fuck. It's just fucking kind of sad, man. And yeah, but I just wanted to speak up for myself, man. I've waited a year to speak up for myself. They put us through so much bullshit. And I don't know if there's other people over there that did it, too. And maybe we'll get more information. I don't know. Yeah, I wouldn't do that to somebody. And they did it, man, they did it to some of these people's podcasts is all they had, man. And these motherfuckers did that, bro. So I'm sorry about that.
And I'm sorry for them. And yeah, I'm just happy to have a voice for myself. And that's one thing that we built here that he had nothing to do with. He had nothing to do with. In fact, he stole on our backs once. And I'm not letting these people do it to me two times. So for anybody that had to take that sucker deal over there, I'm speaking for all of us, man. Because I know that some of you guys have said to me that you wanted to say some of these same things.
One comment that stood out was this one by my baloney has a first name.
Kurt, I recall another YouTube channel about a year ago, who was trying to recover from being demonetized, censored and blocked. One day he post and asked all the listeners to do three things that day. Hit like, leave a comment and go back and watch one of the past videos. I think he said just watching the past videos serves the same purpose. As I recall, he got a huge boost because everyone jumped on the opportunity to give moral support through YouTube. But he also gave the PayPal and the Patreon link like you've done. So today on Toe, I hit like I left the comments and I'm going to go back and watch past videos.
So it turns out that watching past videos does wonders for Toe for the algorithm on YouTube especially. So look through and see if there's one that you normally wouldn't click on. That's important because it shows YouTube, hey, the audience that ordinarily likes topic X also likes topic Y. It's not just narrowly topic X. So click on a Toe episode that you think, man, there's no way out. I don't even understand the title of that, let alone think I like it. Click on it, watch it, and I think you'll be surprised
And at the very least, YouTube will start pushing toe to more people. There's also playlists. So if you want, you can look in the YouTube description. There's several playlists for toe. You can click on that so you can go through episodes one by one if you like. Every episode on toe is edited so there's no large spikes in the volume or loud jumps with music so that people can listen as they sleep. Because I know I used to listen to podcasts as I sleep and I would dislike when they would just quote someone and then the levels were
I've seen it would wake me and then i can fall back asleep cuz i'm worried it's not gonna happen again that won't happen for tell if you personally want to message me to get in contact for whatever reason for sponsorships for donations for support just telling me what is meant to you if that's what you want and you can email me directly at toe at indy film to dot com so that's.
The podcast is now concluded. Thank you for watching. If you haven't subscribed or clicked that like button, now would be a great time to do so as each subscribe and like helps YouTube push this content to more people.
You should also know that there's a remarkably active Discord and subreddit for theories of everything where people explicate toes, disagree respectfully about theories and build as a community our own toes. Links to both are in the description. Also, I recently found out that external links count plenty toward the algorithm, which means that when you share on Twitter, on Facebook, on Reddit, et cetera, it shows YouTube that people are talking about this outside of YouTube, which in turn greatly aids the distribution on YouTube as well.
Last but not least, you should know that this podcast is on iTunes. It's on Spotify. It's on every one of the audio platforms. Just type in theories of everything and you'll find it. Often I gain from re-watching lectures and podcasts and I read that in the comments. Hey, toll listeners also gain from replaying. So how about instead re-listening on those platforms?
iTunes, Spotify, Google Podcasts, whichever podcast catcher you use. If you'd like to support more conversations like this, then do consider visiting Patreon.com slash Kurt Jymungle and donating with whatever you like. Again, it's support from the sponsors and you that allow me to work on toe full time. You get early access to ad free audio episodes there as well. For instance, this episode was released a few days earlier. Every dollar helps far more than you think. Either way, your viewership is generosity enough.
▶ View Full JSON Data (Word-Level Timestamps)
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"text": " The Economist covers math, physics, philosophy, and AI in a manner that shows how different countries perceive developments and how they impact markets. They recently published a piece on China's new neutrino detector. They cover extending life via mitochondrial transplants, creating an entirely new field of medicine. But it's also not just science, they analyze culture, they analyze finance, economics, business, international affairs across every region."
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"text": " Think Verizon, the best 5G network is expensive? Think again. Bring in your AT&T or T-Mobile bill to a Verizon store today and we'll give you a better deal. Now what to do with your unwanted bills? Ever seen an origami version of the Miami Bull?"
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"text": " Jokes aside, Verizon has the most ways to save on phones and plans where you can get a single line with everything you need. So bring in your bill to your local Miami Verizon store today and we'll give you a better deal. Rankings based on root metric true score report dated 1H2025. Your results may vary. Must provide a post-payment consumer mobile bill dated within the past 45 days. Bill must be in the same name as the person who made the deal. Additional terms apply. Because they're these big communities, you're almost like pushed to attach yourself to one of them and become a string theorist or become a loop quantum gravity person. And"
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"text": " I think that is unfortunate and you could say that we always operate in like a digital universe where if gravity is fundamentally classical there needs to be a lot more noise in the gravitational field in comparison to the quantum case."
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"text": " Jonathan Oppenheim, a professor of physics at Oxford, centers his work on a new approach for combining quantum principles with gravity, specifically sidestepping mainstream frameworks like loop quantum gravity and string theory. His research instead focuses on the stochastic coupling between gravity and quantum mechanics. This is one of the most dense of all the TOE podcasts in terms of informational content per minute, rivaling that of some of the Karl Friston episodes."
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"text": " Contrary to the ordinarily trodden path of quantum gravity, which often dominate conversations on unifying quantum mechanics and general relativity, Oppenheim introduces stochastic processes as a new access for inquiry. What ramifications does this have for prevailing theories? We explore that. Jonathan's expertise extends to quantum information, and he's done plenty of work on the quantum version of thermodynamic laws."
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"text": " Like the second law and the third law, something not explored in this episode, but I can't seem to find it anywhere is the connection between the classical and the quantum by making an equivalence between imaginary periodic time and finite temperature. This is also known as analytic continuation and is often just proposed as an unphysical mathematical scheme rather than a profound connection between quantum field theory and statistical mechanics."
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"text": " If anyone knows more about the bridge between these two, then please let me know. At the end of this episode, there will be lengthy updates. Always feel free to use the timestamps, which are in every single theories of everything episode to jump to the sections that you're interested in most. Also, if you're interested in submitting a question for Jonathan when he comes on again, or any toe guest from this point forward, we're instituting a new system. You comment with the word query, then a colon, and then your question."
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"text": " This way, it's easy for me to parse through. OK, if I'm interviewing Jonathan again, I just look at the old Jonathan episode, control F for the word query, and then I find all the questions and I can then submit them to Jonathan in the episode itself, crediting your username, either in the description or orally. My name is Kurt Jaimungal and I have a background in mathematical physics and I use that to analyze the various theories of everything that are out there."
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"text": " Professor Oppenheim, welcome. You were famous a couple months ago, Oppenheimer, the movie came out, you must have gotten a slew of traffic and interest as well and your quanta"
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"text": " Video, which will be on screen right now. Quantum Magazine also came out around the same time. So a flurry of interest for your approach, I'm sure. Yeah, a little bit. We went to see Barbie instead of Oppenheimer. So you didn't watch Oppenheimer? Not yet. It's on my list. Fantastic. Fantastic movie, man. Did you enjoy Barbie? I did, actually. It was fun. What you enjoy most about it?"
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"text": " I thought it was hilarious. It wasn't a fan of some of the messaging, but I thought it was hilarious. Anyhow. Okay. What are you working on these days and what excites you about it?"
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"text": " Well, we've proposed this theory of gravity, which is meant to reconcile general relativity and quantum theory. And so most of you just be working on that. I do a little bit of quantum information theory as well on the side. But the moment most of my group is working on, you know, that they're kind of what follows from this classical quantum theory."
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"text": " You used an interesting word, which is reconcile quantum mechanics and general relativity or quantum and gravity. Whereas most people, as you know, most of the physics community would say quantize gravity. Right. As almost a synonym of making gravity and quantum harmonious. So why do you use that word reconcile and not quantize? Well, I mean, so people realized, I guess more than 100 years ago that general relativity, because it's a classical theory, is incompatible with"
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"text": " Quantum Theory."
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"text": " tells us about geometry on the other side, and they'll say, in almost every lecture on quantum gravity, they'll say, well, you can't have a operator representing matter in quantum theory equal to some classical number representing geometry in general relativity. So that's usually how it's presented. And the usual statement is that we therefore need to quantize gravity in order to make these two things compatible."
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"text": " To be clear, classical in this case means what? Definite values? I mean, that's a good question. In classical mechanics, objects take a definite value. And for example, if I have a particle, it might have a definite value for its position and a definite value for its momentum. I could also imagine that I have a probability distribution of classical systems. So for example, you might imagine that someone slipped a coin."
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"text": " and with some probability they prepared a particle to have a certain position in momentum and with some other if the coin comes up say heads they will prepare the particle with one position in momentum and if the coin comes up tails they'll prepare the particle to have a different position and momentum. So classical systems can don't need to be in definite states they can be in a probability distribution of definite states but"
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"text": " We imagine that there's a fact of the matter about them, even though we might not know, you know, what values of position and momentum the system has, it does have those values in some way. Whereas the quantum system, I mean, the main thing about a quantum system is it doesn't even, you know, a particle never actually has a definite position. So that's the one way to see the difference."
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"text": " Is that a controversial statement? Because there are different quantum theories or interpretations of quantum mechanics where they do. It's just that the wave function represents our knowledge or their hidden variable theories. Right. I mean, so, you know, one of the most famous and I think most important results in physics is Bell's theorem, which essentially says that"
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"text": " At least if you have a local theory, then the particles don't have a position and a momentum. So I think most physicists and most of the lay public is used to Heisenberg's Uncertainty Principle, which says that a particle, we can never know a particle's position and momentum at the same time. And what Bell's theorem says is it goes one step further. It says that the particle doesn't even have a position and a momentum until we measure it."
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"text": " That assumes that there's a slight caveat to that. You can imagine a theory which is very non-local, which somehow keeps track of the particle's position and momentum. But I think most physicists don't believe that such a theory makes a lot of sense. And so I think most physicists have accepted the fact that the particle doesn't actually have a definite position in momentum. You once said that quantum mechanics, I think quantum mechanics or quantum field theory"
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"text": " comes with plenty of ontological baggage. Yeah, what do you mean by that? Well, I guess I've described myself as a quantum mechanic with a lot of ontological baggage. And the term actually comes, I think, probably coined by Lucien Hardy, who essentially says that if we, you know, he proves some results, which essentially say that if we want to have a hidden variable theory, then the amount of"
},
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"end_time": 614.974,
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"text": " Information that we need to somehow have, the amount of information that we need to keep track of becomes incredibly large, becomes infinite. So any sort of a hidden variable theory which describes quantum mechanics needs to keep track of a huge amount of information and it calls that ontological baggage."
},
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"text": " It's one of the reasons that people tend not to like hidden variable theories. They're rather unwieldy, they have to be non-local, they need to keep track of an infinite amount of information and so it's much easier just to believe in quantum theory. I recall Nima said that, I'm unsure if it's Nima, but someone said that even in general relativity you don't have"
},
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"text": " Knowing anything with arbitrary accuracy because if you were to know something with like infinite accuracy you'd have to store that somewhere so that information would carry with that energy and that would create a black hole. I mean in some sense you know because if you believe in the continuum then in some ways any particle has an infinite amount of information that's required to really store"
},
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"text": " store the information about a particle but when we perform measurements we tend to think of our measurements as being relatively weak and not containing you know they don't reveal to us all that information so we're always somehow operating in a kind of an approximate landscape where we don't keep track or we don't even learn you know for example we don't learn the position of a system to arbitrary accuracy to an infinite number of digits we just learn about it to some small number of digits so"
},
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"text": " some sense, you could say that we always operate in like a digital universe where the amount of digits that we keep track of is not the full is not infinite, but it's some finite precision. Now, a popular topic these days is the simulation hypothesis. And so when you say digital physics, you just mean that there's something discrete about it rather than simulated. Right. I mean, yeah, if this often will just"
},
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"text": " Often considered like a discrete space versus a continuous space, which has just a finite amount of information. And there's a question about whether that is good enough and is equivalent. Do we ever need to consider systems which have an infinite, which are infinite dimensional and have an infinite amount of information? That's actually a popular topic right now in, you know, for example, string theorists now are spending a lot of time looking at"
},
{
"end_time": 776.596,
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"text": " Von Neumann Algebras and you know can we actually in a field theory really define in a nice way the entropy of a system because that actually you know the continuum is really difficult to define. So in physics we tend to mostly think that we can describe things with just a finite with finite precision and not worry about the fact that you know really"
},
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"end_time": 798.353,
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"text": " These are continuous systems which really require an infinite amount of information to describe properly. Yeah Nicholas justin also had this argument about there not being a continuum because he said like look let's imagine the electrons classical or just some particle if it's characterized by a real number and most of the time most real numbers are not computable they have an infinite amount of okay."
},
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"text": " But then that would mean that the particle would carry with it that information and what does that mean that the particle would carry with it that information it just is just moving along it doesn't have a coordinate we don't think that it carries with it it chooses a basis to describe itself with coordinates. What's exactly meant when someone says that in a continuum a particle would have infinite information carried with it."
},
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"end_time": 849.701,
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"text": " Well, I suppose this is just a question of like, if there's a particle out there, could I, is there, can I, if you just ask the question, could I learn, well, I guess one can get quite philosophical here, like does the particle carry an infinite amount of information and I just can't know all of it, or I can only know a finite amount of it, or"
},
{
"end_time": 875.06,
"index": 34,
"start_time": 850.316,
"text": " Or does it actually just have a finite amount of information? And that's all I need to describe it. And I'm not sure that as physicists, we would necessarily make a big distinction between the two cases. If we can't measure and learn its position to arbitrary accuracy, then does it have a position to arbitrary accuracy? I don't know."
},
{
"end_time": 904.77,
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"start_time": 875.981,
"text": " Yeah, you mentioned the word philosophy, philosophical there. What role does and Lucian Hardy, I believe, is a physicist, but also considers himself to be a philosopher. Yeah, well, at least I consider himself to I consider him to be a philosophical end of physics. In some circles, the philosophy of physics is not looked down upon. And then in some it is. And I'd say most it is. Now, in your view, where do you stand? Like, what are the pros and cons of philosophy as applied to physics?"
},
{
"end_time": 931.561,
"index": 36,
"start_time": 904.957,
"text": " Well, I think if you, right, I mean, I think if you study quantum theory, then there is an element of philosophy about it. I would say that Bell's theorem, which is a theorem in physics, has huge philosophical implications. So it's somehow hard to get away from you. I think if we're doing quantum theory or"
},
{
"end_time": 951.34,
"index": 37,
"start_time": 932.108,
"text": " Gravity for that matter, I think we're definitely on the boundary of physics and philosophy. I'm not even sure that I would know how to tell you where physics ends and philosophy starts. Now, it's true that there was a time when, say, for example, the interpretations of quantum theory, which is on the philosophical end of"
},
{
"end_time": 978.2,
"index": 38,
"start_time": 951.817,
"text": " All right, now I want to get to your specific advantage as a quantum informationalist. Is it quantum informationist or quantum informationalist?"
},
{
"end_time": 1005.708,
"index": 39,
"start_time": 978.626,
"text": " Quantum information theorist. Yeah. Okay. So as a quantum information theorist. Okay. Well, actually, let me spell out the way that I see it from the outside. It seems like if you love general relativity, if you're a relativist, the approach that most resonates with you is loop quantum gravity. And then if you're a quantum field theorist, the approach that most resonates with you is string theory. It's like seen as an extension of quantum field theory. And those are the large two broad ones."
},
{
"end_time": 1034.411,
"index": 40,
"start_time": 1005.964,
"text": " But then there's quantum information. So if you go into quantum gravity, sorry for saying the word quantum gravity, but you understand the reconciliation of quantum mechanics and gravity from a quantum information perspective, you generate different ideas, much like you do if you're a relativist versus quantum field theorist. So there's Chiara Marletto, who also came to constructor theory from being in quantum computing slash quantum information. And you have a different approach. So can you talk about the advantages that someone who's trained in quantum information has when"
},
{
"end_time": 1056.749,
"index": 41,
"start_time": 1034.735,
"text": " Attempting to make coherent quantum mechanics and gravity. Right. I mean, it's a good question. And I'm not sure how much of it is related to the community of quantum quantum information theory versus the actual study of quantum information theory. But I would I would say that in terms of having a deep understanding of quantum theory, that is, I think,"
},
{
"end_time": 1076.323,
"index": 42,
"start_time": 1057.756,
"text": " I think the quantum information theory community and the quantum computation theory community really has a very deep understanding of quantum mechanics. So one of the reasons I got interested in quantum information theory is because I felt I needed to understand quantum theory better. If you come in the"
},
{
"end_time": 1103.456,
"index": 43,
"start_time": 1076.681,
"text": " Hi, everyone."
},
{
"end_time": 1128.148,
"index": 44,
"start_time": 1103.882,
"text": " are studying, say, computation, you're interested in classical computation and quantum computation, and you can start thinking about other forms of computation from other, you know, how could you modify our physical laws and how would that change the laws of computation? And so for whatever reason, I think there's a deep understanding of how you can change quantum theory and how you shouldn't change quantum theory."
},
{
"end_time": 1158.336,
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"start_time": 1129.94,
"text": " A good example of that is linearity. If you come from quantum information theory, you know there are certain parts of quantum theory which we wouldn't change. We would want our theory to be linear, meaning that if you flip coins and prepare different sorts of systems, depending on the outcome of the coin toss, then your dynamics shouldn't"
},
{
"end_time": 1186.544,
"index": 46,
"start_time": 1158.951,
"text": " shouldn't be sensitive to what the values of those coins are. Or for example, we would say that any theory of nature, if it's a theory that acts on the density matrix of a quantum system, it should make sure that probabilities get mapped to probabilities and then it has certain mathematical properties. So I think the quantum information theory community is just quite used to"
},
{
"end_time": 1216.834,
"index": 47,
"start_time": 1187.039,
"text": " considering different sorts of dynamics and what sort of dynamics is allowed. Maybe that comes a little bit because we study things like decoherence and we study quantum systems which interact with other quantum systems like an environment which we ignore and forget about. And so the dynamics is in some sense a bit more general than what is considered in straight up quantum theory that you might learn in an undergraduate quantum mechanics course."
},
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"end_time": 1244.565,
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"start_time": 1217.978,
"text": " What's the name of the approach? Does it have a name? So it I guess has gone by, you know, it has many names in some sense. So I called it a post quantum theory of classical gravity because gravity is classical, but quantum mechanics is modified slightly. It doesn't need the measurement postulate. So it's like a post quantum theory."
},
{
"end_time": 1267.91,
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"start_time": 1244.957,
"text": " It had been, you know, people have proposed for probably almost as long as there's been an idea that we should quantize gravity. There's also been people who have suggested that maybe gravity could be classical. And so there's something that goes by the name of hybrid gravity or classical quantum gravity that has also existed out there."
},
{
"end_time": 1283.951,
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"start_time": 1268.166,
"text": " Okay, you don't call it by a moniker. You just write papers about it. But when you're referring to it, you don't call it this is classical quantum gravity or this is post because calling it post quantum is a description. It's not like a title like geometric unity or causal dynamic triangulation. What I'm asking for is, is there a title?"
},
{
"end_time": 1304.258,
"index": 51,
"start_time": 1284.872,
"text": " I don't yet have a good name, but maybe someone once said that it was a mongrel theory because it's a blend of a quantum theory and a classical theory. I thought about calling it mongrel relativity, but I don't have a good name for it."
},
{
"end_time": 1328.063,
"index": 52,
"start_time": 1304.65,
"text": " For the sake of this discussion, we're going to call it Mongrel Relativity. Why not? I want you to explain what MG is, but do so with the transition of why you don't like the current approaches to making gravity and quantum mechanics cooperate. Well, let's start with that. I wouldn't say I don't like the current approaches. I think I'm more of the view that"
},
{
"end_time": 1357.449,
"index": 53,
"start_time": 1328.507,
"text": " There's been this assumption and I think based on some incorrect arguments there's been this assumption that we have to quantize gravity and we started off by starting with the Einstein equation where you have matter on one side which is quantum and it should be equal to something which is classical and that doesn't make sense so people have thought we have to quantize gravity. And there's been a bit of a discussion about that I think in part because"
},
{
"end_time": 1384.394,
"index": 54,
"start_time": 1358.37,
"text": " We've spent more than a hundred years of failing to quantize gravity. And so because there's been about this hundred years of failure, one can, you know, it's useful to think, well, is this really the right approach or is it possible that we've gone down and are taking a wrong direction? So I don't know what the correct answer is. I don't know if gravity is quantum or classical or something else."
},
{
"end_time": 1411.527,
"index": 55,
"start_time": 1384.718,
"text": " I suppose my perspective is just that we should, because the arguments that people marshaled claiming that we had to quantize gravity, because those have turned out to be incorrect, I think it's important to revisit the issue and to explore the possibility that maybe gravity could somehow be fundamentally classical. And I think there's some motivation for that. I don't think it is just a random idea that, okay, maybe"
},
{
"end_time": 1438.763,
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"start_time": 1412.09,
"text": " Gravity is special and classical. I think there's some, you know, good arguments you can make in favor of not quantizing gravity. So that's my perspective, just that it's possible that it could be classical gravity. And there's some reason to believe that gravity is special and different to the other forces and therefore should remain classical. What would some of those reasons be? So I think that, you know,"
},
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"index": 57,
"start_time": 1439.377,
"text": " Gravity is different from other forces in that it is what Einstein's general relativity tells us is that matter causes space-time to bend and it's that curvature of space-time that is the manifestation of gravity. So we're just following a straight line, we're just free-falling in a geodesic and that's because space-time is curved that gives us the appearance of a force which we call gravity."
},
{
"end_time": 1494.77,
"index": 58,
"start_time": 1469.497,
"text": " Um, but it's, it's the only force which can be described universally as a geometry. So, um, in that way, gravity is, is special. It's, it universally describes as background causal structure, um, which the rest of, you know, which all the other fields live in this arena of this curved background geometry."
},
{
"end_time": 1524.821,
"index": 59,
"start_time": 1495.674,
"text": " And so there's, you know, there are reasons to imagine that that background structure has to be fundamentally classical. And I think one of the main reasons I would give for that is that the causal structure seems to be, which gravity gives us, so it gives us this causal structure. I don't think that we really know how to do quantum theory without that causal structure. At least I don't know any way of doing it."
},
{
"end_time": 1553.473,
"index": 60,
"start_time": 1525.333,
"text": " And we can try and quantize it, but then in some sense, I feel like we lose our legs, we lose all this background structure which we needed in order to perform quantum theory. And is this related to you make a non-canonical choice at some point? Right. And so you lose something that's special about general relativity. That's right. So, you know, you can imagine, I mean, let's just even start with how physicists, you know, like what is physics?"
},
{
"end_time": 1575.742,
"index": 61,
"start_time": 1553.968,
"text": " Usually what we do is we specify some system at some initial time and then we ask how does it evolve and predict what's going to happen to it in some future time. And in a quantum theory of gravity, just merely those statements are difficult."
},
{
"end_time": 1604.974,
"index": 62,
"start_time": 1576.032,
"text": " So, for example, if we want to specify the initial state of the system, well, in occurred space time, that's not so easy because you have to find some hypersurface across all of space and you label that and say this represents an initial time slice. That choice is not, you know, there's a number of ways that you can slice up space time into"
},
{
"end_time": 1634.787,
"index": 63,
"start_time": 1605.794,
"text": " Some family of hyper surfaces, these spatial couchy surfaces that are kind of evolving in time like this. And you can do that in quantum field theory because you have a definite causal structure. So if I want to say that this curve slice here represent, you know, represents the state of the system at time t equals zero, then that's a well defined statement."
},
{
"end_time": 1664.838,
"index": 64,
"start_time": 1635.52,
"text": " But I don't know how to make that statement if the geometry itself is the thing I'm quantizing because then I don't have that causal structure. Now I can imagine just choosing one and I just choose some particular slice and I then just quantize it as I would any other field theory. But it's"
},
{
"end_time": 1692.858,
"index": 65,
"start_time": 1665.418,
"text": " As far as we can, as best we understand, the quantum theory of gravity that we would come up with will be dependent on this choice of how we chose to slice up our space. What if the loop quantum theorist would say, hey, the constraints on such a system in our theory are such that it's independent of this, even though we chose the Cauchy surface, the observables are independent of such foliations. So does that not get over the objection?"
},
{
"end_time": 1706.852,
"index": 66,
"start_time": 1693.78,
"text": " Well, so I guess the problem with, you know, so there's two approaches you can do. One is you can say it. One is you can just hope that your theory will be independent of the choices."
},
{
"end_time": 1732.483,
"index": 67,
"start_time": 1707.517,
"text": " You can try and make a completely background independent approach, which is what loop quantum gravity tries to do. And in particular with the spin foam, they use something called spin foam networks, which is the object of interest, and take a background independent approach. And the problem then they face is that they have no idea how to recover"
},
{
"end_time": 1761.22,
"index": 68,
"start_time": 1732.654,
"text": " The classical geometry at the end so there's no way of for them to know or they haven't at least been able to show that in some low energy limit they will recover gravity. On the other hand in string theory they can take the other approach where they have a background dependent theory and hope that"
},
{
"end_time": 1790.486,
"index": 69,
"start_time": 1761.664,
"text": " They'll be able to either show that it's independent of that choice or come up with a background independent approach. And some would say that a lot of string theory now is something called ADSCFT or holography. And there's some claim that that is to some extent or to a larger extent background independent. So this post quantum theory of yours, can you please describe it?"
},
{
"end_time": 1819.633,
"index": 70,
"start_time": 1790.981,
"text": " So the main idea is that you somehow take seriously the idea that maybe we need this classical background structure of space-time and then it has to be classical. And so you just start simply by saying, can we consistently couple classical systems and quantum systems? Is there any way to do that? And at the moment we have"
},
{
"end_time": 1849.394,
"index": 71,
"start_time": 1819.957,
"text": " Only two frameworks for physics. We have quantum theory and classical mechanics. We don't really have at the moment any credible other frameworks which are beyond quantum theory, for example. And so the first question you can just ask is, is it possible to consistently couple a quantum system with a classical system? And there's been a huge number of kind of"
},
{
"end_time": 1877.875,
"index": 72,
"start_time": 1849.872,
"text": " Approaches to that where people have tried to consistently couple a quantum system with the classical system and Almost all of those have been unsuccessful But actually in you know, the early nire the mid 90s there's there's actually a few examples of such consistent coupling due to Doshi and due to two people named Blanchard and Yajic and"
},
{
"end_time": 1905.674,
"index": 73,
"start_time": 1878.268,
"text": " And they found some examples where you can consistently couple a quantum system with a classical system. And so the first thing we had to do was just to say, OK, what is the most general form of dynamics that we can come up with which couples a classical system with a quantum system? So that's the first thing you do is you derive the most general dynamics that could do that. Before we go to the second thing that you do, can you describe what it means to couple?"
},
{
"end_time": 1936.613,
"index": 74,
"start_time": 1907.261,
"text": " Right. So we're used to the following coupling between the classical system and the quantum system. You imagine that we are doing a double slit experiment. So we have, say we fire a bunch of electrons or some photons through two slits and they form a diffraction pattern at the far end and they interfere. So we see a nice interference pattern at the screen behind these two slits."
},
{
"end_time": 1965.026,
"index": 75,
"start_time": 1937.261,
"text": " That's a coupling between a quantum system and a classical system because we treat the two slits as classical, we treat the slits, we treat the screen at the back as classical and there's this little photon gun which is firing photons or firing electrons and that's, we treat classically. So, or a particle in a potential, you know, we treat this potential that's sitting there, that's like a classical potential which is produced by a magnetic field or something like that."
},
{
"end_time": 1989.65,
"index": 76,
"start_time": 1965.299,
"text": " We treat that as classical and the particle moves. So that's an example where the classical system exerts a force onto the quantum system. And we do that all the time in physics. So we know very well how to couple a classical system which acts onto a quantum system. What we"
},
{
"end_time": 2019.36,
"index": 77,
"start_time": 1989.906,
"text": " didn't know how to do except for these examples that there were these examples in the 90s which curiously were not, I don't think, really known except in a very small community. So the question that you want to address now is can a quantum system back react onto a classical system? Can it exert a force onto a classical system without causing a contradiction?"
},
{
"end_time": 2042.449,
"index": 78,
"start_time": 2019.718,
"text": " And there were arguments that were given as to why that will always result in a contradiction. And I think the most famous argument is due to Feynman at one of the first Chapel Hill conferences, these famous conferences that were organized to discuss general relativity."
},
{
"end_time": 2063.968,
"index": 79,
"start_time": 2042.944,
"text": " Actually, on this channel, there's a documentary on the Chapel Hill Conference, particularly with antigravity's connection with quantum gravity. These famous conferences that were organized to discuss general relativity. And the argument was as follows. He imagines a double-stud experiment"
},
{
"end_time": 2093.285,
"index": 80,
"start_time": 2064.224,
"text": " and he imagines this particle which you know sometimes you could imagine a particle which goes through slit number one and sometimes it goes through slit number two and then he says well imagine that this particle has a gravitational field and imagine that we measure this gravitational field and imagine that we can measure the gravitational field to arbitrary accuracy then we could by measuring the gravitational field to arbitrary accuracy we can discover"
},
{
"end_time": 2123.353,
"index": 81,
"start_time": 2093.729,
"text": " Where this particle is because we measure its gravitational field and then we would know if it went through the left slit or the right slit and if we know whether it went through the left side of the right side then we shouldn't have an interference pattern. Yet we see interference patterns and therefore Feynman argued that you know we would have to quantize the gravitational field. Why can't someone say look we've never done that experiment where we've detected gravitationally whether it's gone through A or B"
},
{
"end_time": 2145.674,
"index": 82,
"start_time": 2123.814,
"text": " And if we were to do that, we would see that there would be no interference pattern. Right. That's a good question. And it turns out that if you merely try to write down the state of a quantum system in the classical system such that the classical system knows which, you know, which let the particle went through, then that's enough."
},
{
"end_time": 2158.831,
"index": 83,
"start_time": 2146.101,
"text": " for you not to have an interference pattern. So whether or not you measure the gravitational field, the mere fact of the gravitational field knowing which that the particle went through would be enough to cause the interference pattern to not be there."
},
{
"end_time": 2181.271,
"index": 84,
"start_time": 2159.428,
"text": " And that's the same with like, you know, people often ask about quantum theory, you know, do I have to look at the cat, whether it's dead or alive in order to collapse it? Does a person have to look at it? Well, no, just the environment measuring, you know, the environment measures the cat. And here the gravitational field is measuring the cat and is measuring which that the particle went through. So"
},
{
"end_time": 2211.408,
"index": 85,
"start_time": 2181.886,
"text": " If your environment is classical, then just the fact that in theory it could be measured to arbitrary accuracy to determine which that the particle went through, that would be enough to destroy your interference pattern. Thus the conclusion is that the particle is in a superposition, like even a gravitational field is in a superposition? Yeah, that's what Feynman concluded that the gravitational field had to also be in a superposition with the particle. That was the only way to consistently think of the double slit experiment in which the particle"
},
{
"end_time": 2240.401,
"index": 86,
"start_time": 2211.732,
"text": " produced a gravitational field because it was a massive particle. Maybe this comes from thinking about things from a quantum information perspective. One thing that we've learned about quantum theory is that the state of the wave function, the quantum state, is more analogous to a classical probability distribution"
},
{
"end_time": 2271.084,
"index": 87,
"start_time": 2241.152,
"text": " than it is to say you know a single c number or you know a single position and momentum of a particle. So one way to think of the it's a good analogy you know the ket of a quantum state is a bit analogous to a probability distribution and so and because we think about probability distributions all the time in quantum information theory it's quite natural to"
},
{
"end_time": 2293.695,
"index": 88,
"start_time": 2271.51,
"text": " To think about Feynman's no-go argument and to just say, well, wait a second, what if the gravitational field is in a probability distribution of different configurations, then measuring the gravitational field will not determine which that the particle went through. So, for example, if the particle goes through the left slit, it might produce some"
},
{
"end_time": 2319.531,
"index": 89,
"start_time": 2294.019,
"text": " random, slightly random gravitational field. And if it goes through the right slit, it will produce a slightly different random distribution of gravitational fields. But because we have a random distribution of two different gravitational fields, measuring the gravitational field does not determine which slit the particle went through. Is the C number supposed to be thought of as a scalar or a complex number like C stands for what?"
},
{
"end_time": 2349.462,
"index": 90,
"start_time": 2319.735,
"text": " Oh, sorry. Yeah. So, uh, I guess in this case, when I, when I talk about a C number, I just mean that, uh, sorry, I guess this is in say the context of, uh, looking at Einstein's equation where you have an operator on one side and then that's just, you know, it's just a number, the Einstein tensor. So it's a, it's a single number versus an operator or say a vector, which is, you know, in quantum theory, observables are"
},
{
"end_time": 2379.241,
"index": 91,
"start_time": 2349.991,
"text": " operators which act on quantum states which are vectors, whereas in classical mechanics we just have the particles just described by a number. This is the particle's position in momentum. I've heard the term c number, I've heard it, but I've never read it, so I don't know what is the definition of c number. So what's the difference between classical randomness and quantum randomness?"
},
{
"end_time": 2399.394,
"index": 92,
"start_time": 2379.838,
"text": " You mentioned it before, but can you briefly outline it once more? Because you're about to make the connection between, well, you're about to explain how randomness solves a harmony issue. Right, right. So a quantum system, so a classical system can be"
},
{
"end_time": 2425.026,
"index": 93,
"start_time": 2400.043,
"text": " It can have a probability. So we can imagine, for example, a particle has a position and momentum, and we can also imagine that we have a probability distribution of different positions and momentums. So, you know, there's some probability that the particle has position X equals zero and momentum, you know, 10 units."
},
{
"end_time": 2454.77,
"index": 94,
"start_time": 2425.538,
"text": " We can imagine such a distribution and the probabilities, both of its particular values that the position can take and the values that the momentum can take, those are all positive and they all sum to one if we were to sum them up. On the other hand, a quantum states, we cannot ascribe probabilities to a particular outcome of a position and a momentum measurement. That just doesn't exist."
},
{
"end_time": 2483.387,
"index": 95,
"start_time": 2455.077,
"text": " We can because we're either going to perform the position measurement or we're going to perform the momentum measurement, but we don't perform both. And so the quantum state does not need to be described by a probability distribution over position momentum whose values are all positive. It's describable by something else, which is, you know, it can be described, for example, by something called a Wigner distribution, which looks a lot like a probability distribution except"
},
{
"end_time": 2508.78,
"index": 96,
"start_time": 2483.677,
"text": " Its values are not always positive. And that's okay because I will never measure and get a negative probability because I can't measure both the position and the momentum of the particle. So it's okay if a quantum state, if its distribution has negative values, that's not okay for a classical distribution. It has to always have positive values because"
},
{
"end_time": 2535.811,
"index": 97,
"start_time": 2509.684,
"text": " You know, the probability that a particle has a particular position momentum needs to be positive. So now what's meant by that? The coupling between gravity or some gravitational system, some classical system and some quantum system has to be stochastic. Also, can you outline what the difference between randomness as stochasticity is? OK, I don't know that there's a so I use those words interchangeably. Maybe there's a more technical"
},
{
"end_time": 2560.452,
"index": 98,
"start_time": 2536.596,
"text": " Terminology and maybe they do mean different things, but I tend to use them interchangeably Although I guess when I think of a stochastic process I think of a dynamical process so you know the particle is going through the left slit and in a deterministic theory it would bend space-time in a particular way and in a stochastic theory it would"
},
{
"end_time": 2590.162,
"index": 99,
"start_time": 2560.879,
"text": " You know, it almost like flips a coin and depending on the value of the coin, it bends space time in a slightly different way. So you can imagine that there's these coins being tossed all the time, which determines if the particle goes to the left slit and it produces some different gravitational fields with different probabilities. And if it goes through the other slit, the right slit, it will produce some it'll bend space time in some other way. But it's"
},
{
"end_time": 2619.582,
"index": 100,
"start_time": 2590.742,
"text": " The way in which it bends space-time is determined not just by which slit it went through but also by it flipping a coin. Now I want to be careful when I say flipping a coin because that one is almost imagining that there is some physical process by which it determines which of these gravitational fields to produce but actually I don't believe that there is actually any physical process which is determining which gravitational field is being produced."
},
{
"end_time": 2643.336,
"index": 101,
"start_time": 2619.684,
"text": " Let's make it simple and imagine that someone's walking through two doors. Does that mean that they're constantly carrying with them a coin? And even before they encounter those two doors, they're flipping it and they're making some other decision. And then when they get to the door, then they flip it and then it's a left right decision. Is this coin just being flipped for them? How does this work? There's no physical process. Yeah, I mean, maybe even another way of saying it is imagine that, um,"
},
{
"end_time": 2664.855,
"index": 102,
"start_time": 2644.667,
"text": " Someone's going through the right door, someone goes through the right door or the left door. If I'm far away, I can sit there with a pendulum and I could actually figure out, I could try and figure out which door they went through by trying to measure their gravitational field. But now imagine that at every point in space, the gravitational field is just"
},
{
"end_time": 2695.162,
"index": 103,
"start_time": 2665.452,
"text": " Okay, then the way that I'm imagining it is that you have a pendulum and it's"
},
{
"end_time": 2724.224,
"index": 104,
"start_time": 2695.52,
"text": " I don't know how the pendulum apparatus is supposed to be when you actually measure, but I'm just going to say that it's completely still. And then you see, does it move slightly to the left or move slightly to the right because it's attracted to the person who goes to the left or to the right. Okay. You're saying that actually if you were to look at that pendulum, it would be constantly jittery because just even without anyone going through the doors. Right. Oh, okay. So what I was about to say is because this not be solved with more precision, but then you would have to do a series of measurements. Yeah."
},
{
"end_time": 2747.858,
"index": 105,
"start_time": 2724.599,
"text": " The most famous gravity measurement is probably the Cavendish experiment where they sit there with this beam with two weights on the end and it's held up by a string and it kind of rotates like this and you use that to measure say the gravitational field of the earth or of two balls of a kilogram mass for example."
},
{
"end_time": 2777.961,
"index": 106,
"start_time": 2748.848,
"text": " If you ever have seen that experiment or you've tried to do it in, say, an undergraduate physics lab, you'll see that the torsion pendulum kind of moves about quite a lot and is jiggling much in the way that we just described. And the reason it's jiggling is mostly because air molecules are hitting it and the system is very noisy and there's heat and we don't have very good control of gusts of air which push and pull the pendulum."
},
{
"end_time": 2805.299,
"index": 107,
"start_time": 2778.729,
"text": " But imagine that we got rid of all those gusts of air and had everything in a perfect vacuum and didn't have any stray electromagnetic fields or gravitational fields around but we cleaned up everything. Would there still be some fundamental noise? And this theory predicts that there will be. And it's this noise which somehow allows interference patterns because"
},
{
"end_time": 2829.906,
"index": 108,
"start_time": 2806.323,
"text": " Now the quantum field theorists would say there is noise anyhow because there's some fluctuations. So is there a way of you distinguishing the noise from the fluctuations versus I don't know what type of noise this is called but this post quantum noise? Yeah, that's a very good question and"
},
{
"end_time": 2853.336,
"index": 109,
"start_time": 2830.179,
"text": " There is disagreement, so I've had disagreement with some of my colleagues about this, but we've calculated how much noise there has to be and there has to be a lot more noise. If gravity is fundamentally classical, there needs to be a lot more noise in the gravitational field in comparison to the quantum case."
},
{
"end_time": 2882.363,
"index": 110,
"start_time": 2853.729,
"text": " And it's true that in the quantum case you also need some noise there because you can imagine the same experiment, the double slit experiment that I just gave. You can imagine the same argument being made about the electromagnetic field. How is it that if the particle goes through the left slit and the right slit, I can measure the electromagnetic field? And what is it about the electromagnetic field which doesn't allow me to determine which slit the particle went through?"
},
{
"end_time": 2909.377,
"index": 111,
"start_time": 2883.131,
"text": " We can't measure the electromagnetic field to arbitrary accuracy. Because the electromagnetic field has a quantum nature, then I can't measure with exact precision the electromagnetic field and say it's conjugate degrees of freedom."
},
{
"end_time": 2937.432,
"index": 112,
"start_time": 2910.162,
"text": " So because we can't measure the electromagnetic field to arbitrary accuracy, we're not able to determine which step the particle went through. Or another way of saying it is this. In quantum mechanics, you can have two different states which cannot be distinguished. In other words, the electromagnetic field will be in a different state depending on whether the particle went through the left slip or the right slip."
},
{
"end_time": 2964.309,
"index": 113,
"start_time": 2938.012,
"text": " But even though the state of electromagnetic field is different, I still can't tell it apart. It has some overlap. There's overlap between the two states and those two states are not orthogonal, we would say. In other words, they can't be distinguished perfectly. And it's because those two different states of the electromagnetic field are not distinguishable. It's that which allows you to still have an interference pattern."
},
{
"end_time": 2993.131,
"index": 114,
"start_time": 2965.452,
"text": " Now, sometimes you don't, right? Sometimes the particle will go through the left slit and it will emit a photon because it happened to hit the wall in a certain way. And if I were to measure that photon, I would be able to determine which slit the particle went through. So there is some decoherence. The interference pattern does get disturbed a little bit by the electromagnetic field, but not by very much. This theory of yours doesn't have predictions. So one prediction I see is that it's a null prediction, namely that there is no graviton."
},
{
"end_time": 3019.497,
"index": 115,
"start_time": 2993.353,
"text": " Right. Does it have other predictions? And am I even correct by saying that there is no gravitation? Right. There's gravitational waves, but there is no quantized particle which is responsible for carrying the gravitational force. And so one of the big predictions is this noise in the gravitational field. So, you know, we predict that you should go into the Cavadish experiment and you will have to see"
},
{
"end_time": 3050.299,
"index": 116,
"start_time": 3022.329,
"text": " a large amount of noise in the gravitational field. Now the problem is that there is already a large amount of noise in the gravitational field. If you ask the people at NIST who are responsible for keeping the one kilogram mass and telling us how keeping that and doing these precise measurements of say a one kilogram mass, they will tell you that it's actually very difficult experiment to perform and that their measurements do have quite a large variance."
},
{
"end_time": 3075.009,
"index": 117,
"start_time": 3050.742,
"text": " and inaccuracy. So the experiment we're proposing is higher precision tests of those measurements of say a one kilogram mass in order to put a bound on how much noise there is in the system. I mean what's exciting, even if you, whether or not you believe in, you know, if we, I feel like this question of whether gravity is fundamentally quantum or classical is"
},
{
"end_time": 3100.93,
"index": 118,
"start_time": 3075.265,
"text": " a real one and I think what's exciting is that this actually allows us through these precision Cavendish measurements to actually determine whether gravity has a quantum or classical nature. With the noise, if you were to with precision measure the gravitational field, would that noise still be there even in other approaches to harmonizing gravity with quantum mechanics like string theory where you sum over metrics"
},
{
"end_time": 3127.073,
"index": 119,
"start_time": 3101.357,
"text": " So like, there is some uncertainties to what the gravitational field is in string theory. So would they say that that should also produce noise or is this noise distinguishable from the noise that you're talking about? So there will be some noise and it has in some ways a similar form, but the amount of it is just much less in a quantum theory. And the reason is, is that in, is, you know,"
},
{
"end_time": 3157.585,
"index": 120,
"start_time": 3128.097,
"text": " In classical theory, you can perform in some sense two different experiments. You can do a precision test of gravity and see if there's noise in the gravitational field. And the other thing you can do is you can do an interference experiment. So I can take a gold atom, for example, a very heavy atom, and see if I get an interference pattern. And if you get an interference pattern, you can keep pushing how coherent you can make a gold atom. So I might imagine a gold atom that"
},
{
"end_time": 3187.568,
"index": 121,
"start_time": 3158.08,
"text": " can follow two different paths and be in a superposition of these two different paths. If I can keep the gold atom in superposition for a very long time, then it would mean that I need a large amount of noise in the gravitational field in order to keep that coherence. There's a trade-off in some sense between how long I can keep a gold atom in superposition and how much noise there needs to be in the gravitational field in order for the gold atom to keep"
},
{
"end_time": 3217.705,
"index": 122,
"start_time": 3188.2,
"text": " Being in a coherent superposition and there's a trade-off between those two things and so I can perform both those experiments and if I can and the longer I'm able to to extend the coherence time of gold atom the more noise I know there must be in the gravitational field if the gravitational field is classical. So between those two experiments you could either rule you know you could potentially say rule out the classical theory of gravity"
},
{
"end_time": 3246.63,
"index": 123,
"start_time": 3218.558,
"text": " Whereas in the quantum case, there's no such trade off. You don't need to have, I mean, there's a related trade off, but it's not quite the same. And so it turns out that for a quantum system, if a gravitational field is quantized, then there doesn't need to be nearly as much noise in it. Understood. If one wants to read up more about this, which I'm sure many, many people do, what would be, forgive the pun, the canonical paper of yours to read?"
},
{
"end_time": 3275.725,
"index": 124,
"start_time": 3247.261,
"text": " So there's just, you know, I mean, there's a there's a recent quanta article which you mentioned, which is, you know, probably reasonably accessible to a popular audience. I'll put the link to that in the description as well as to the quantum video of yours. Great, thanks. And then, you know, the first article was called a post quantum theory of classical gravity. And that is quite a detailed article, but at least the first two or three pages, you know,"
},
{
"end_time": 3303.268,
"index": 125,
"start_time": 3277.056,
"text": " tries to explain this Feynman argument and why it doesn't rule out a classical theory of gravity and then it also discusses one of the big reasons that people disregarded the fact that we could have a classical theory of gravity was that they essentially assumed that having a classical theory of gravity was equivalent to something called the semi-classical Einstein's equation where"
},
{
"end_time": 3333.2,
"index": 126,
"start_time": 3304.087,
"text": " Where you just take the expectation value of the stress energy tensor and then stick that into Einstein's equation. And that's been known for a long time to be a pathological equation. If we take it as fundamental, it leads to all kinds of problems. And so people somehow associated semi classical gravity with, you know, with attempts to keep the gravitation field classical."
},
{
"end_time": 3353.848,
"index": 127,
"start_time": 3334.036,
"text": " What's so pathological about it? It doesn't satisfy this principle of linearity, which I said is so important and which I think any theory ought to be linear. When you have a theory which depends on expectation values,"
},
{
"end_time": 3380.452,
"index": 128,
"start_time": 3354.241,
"text": " then it allows you to do all kinds of things like superluminarily signal faster than light or in some sense violate the uncertainty principle because if you can measure an average value then that's a pretty weird thing, right? Like in a single go. Here's a way of explaining it. Imagine that I flip a coin and with some probability I put a planet on the right"
},
{
"end_time": 3402.739,
"index": 129,
"start_time": 3380.913,
"text": " And with some, so if I get heads, I put the planet on the right. And if I get tails, I put the planet on the left. And now imagine that I have a theory where I am attracted to the expectation value of those two state of affairs. So on average, the planet is neither on the left or the right, it's in the middle."
},
{
"end_time": 3429.104,
"index": 130,
"start_time": 3403.08,
"text": " And so what happens in a theory where you take expectation values is that if I drop a test particle and watch the test particle freefall towards the planets, they will fall straight down the middle between the two places where I would have put the planet. So here's the planet if I get heads, here's the planet if I get tails,"
},
{
"end_time": 3452.995,
"index": 131,
"start_time": 3430.094,
"text": " If I take the expectation value, the expectation value is somehow down the middle and that's where the particle falls. And that's of course not what we expect to happen. So a theory where you use expectation values rather than say something else is going to lead you into a world of pain essentially because of that."
},
{
"end_time": 3482.261,
"index": 132,
"start_time": 3453.865,
"text": " In your post quantum theory, is then the conservation of momentum something that is just emergent or not fundamental? Because if you're shooting a particle, let's say a planet, like you mentioned, the planet could go here or there. Does that not then send the planet off to another slightly different trajectory than it was before? So there is a so"
},
{
"end_time": 3512.176,
"index": 133,
"start_time": 3483.609,
"text": " The theory conserves momentum, but it doesn't conserve all, you know, there are things which are not conserved in it, which would be conserved in the deterministic theory. So Noether's theorem, which is a famous theorem which connects symmetries with conservation laws, because we believe in time translate, you know, our theories of physics are invariant under a time translation."
},
{
"end_time": 3539.172,
"index": 134,
"start_time": 3512.858,
"text": " And they're also invariant. If we move three meters to the right or three meters to the left, the laws of physics don't change. And that tells us that momentum and energy are conserved. Noether's theorem assumes that the laws of physics are deterministic and are given by a unitary transformation. If they're not, as in these theories, then you don't have the same connection between symmetries and conservation laws."
},
{
"end_time": 3569.377,
"index": 135,
"start_time": 3539.65,
"text": " And it turns out in this theory that because you have lost this connection between symmetry and conservation laws, then energy does not need to be conserved. And so you can get something which may look like some kind of anomalous heating coming from these sorts of theories. Now, in general relativity, energy is very difficult to define in the first place."
},
{
"end_time": 3599.36,
"index": 136,
"start_time": 3570.52,
"text": " understanding what exactly that means to such a theory where you don't really have a locally defined energy. That's another matter, but it's quite complicated in terms of how conservation laws are respected in such a theory. Speaking of laws, you have a paper, I believe it's called the second laws of quantum thermodynamics. So firstly, what is quantum thermodynamics? And then why are there multiple second laws? Right."
},
{
"end_time": 3626.698,
"index": 137,
"start_time": 3599.974,
"text": " When I was an undergrad we were taught that thermodynamics is a theory that you get in the thermodynamic limit. In other words, I have a gas and it has many particles and I take the limit that the volume goes to infinity and that's what thermodynamics is. It's that theory of large systems. But you can ask"
},
{
"end_time": 3650.623,
"index": 138,
"start_time": 3627.227,
"text": " What happens to, if I just have to say, a single gas molecule or a single quantum system, does it still obey things which look like the second law? And can I still define some laws of thermodynamics for those systems? And it turns out you can. So for a single particle, the entropy also has to increase."
},
{
"end_time": 3674.224,
"index": 139,
"start_time": 3651.203,
"text": " But it turns out there's a whole bunch of other quantities which has to increase as well. So I can think of, in some sense, the second law of thermodynamics as placing a restriction on what will happen to my system as time goes on. So I know that the entropy has to increase, but there's a bunch of other entropies that you can also define, and it turns out those also have to increase as well."
},
{
"end_time": 3702.79,
"index": 140,
"start_time": 3675.145,
"text": " There's all kinds of entropies which are different to the standard one and it turns out those all have to increase and what happens is as I have more and more particles and as I make my system size grow larger and larger it turns out that all these other second laws and all these other entropies become equivalent to each other and so in the thermodynamic limit I only have one"
},
{
"end_time": 3730.623,
"index": 141,
"start_time": 3703.558,
"text": " entropy. But on the small scale, I have a whole bunch of other entropies, which turns out they also obey some kind of a second law. We corresponded over email, you and I, and I spoke about Flaminia, who's also working on quantum information and gravity. And I was curious to what the relationship between her approaches and yours. Right. So so she's her and some of her colleagues have"
},
{
"end_time": 3755.879,
"index": 142,
"start_time": 3732.637,
"text": " Proven various theorems about what happens if the gravitational field is classical. And they've done it in a more general framework than we often work in. So they haven't made any assumption. For example, they haven't assumed that matter obeys laws of quantum theory. They've allowed"
},
{
"end_time": 3784.65,
"index": 143,
"start_time": 3756.732,
"text": " They're considered more general sorts of interactions. In fact, you can there's all kinds of machinery that has been developed called, say, general. It goes by the name of generalized probabilistic theories, which is a huge class of theories which go beyond quantum theory. And we don't know if they actually exist, these theories or whether they are well defined or not. But you can certainly think about the kinds of some of the properties they may have."
},
{
"end_time": 3810.759,
"index": 144,
"start_time": 3784.957,
"text": " I mentioned these experiments we proposed where we show that if gravity is fundamentally classical, then it has to be stochastic. It has to have randomness. One of the results, for example, is that even if we go beyond quantum theory, if gravity is classical, then it somehow"
},
{
"end_time": 3839.275,
"index": 145,
"start_time": 3811.288,
"text": " We'll still have to be stochastic, even if we're able to modify the laws of matter. So if we go beyond quantum theory from the matter distribution. And what about Chiara Marletto? What about constructor theory's relationship to yours? Yeah, so that's another example where she has looked at theories which go beyond quantum theory."
},
{
"end_time": 3868.558,
"index": 146,
"start_time": 3839.906,
"text": " I guess in both cases the claim is being that it rules out the classical theory of gravity but usually there's some assumption for example of reversibility or an assumption of determinism and so what these theorems tend to show is that if we have a classical theory of gravity then they have to be irreversible or have some sort of indeterminism or randomness in them. So I think"
},
{
"end_time": 3898.643,
"index": 147,
"start_time": 3869.241,
"text": " This is kind of establishing that if gravity is classical, it has to be stochastic. I think from their point of view that that is so unpalatable that for them and for maybe many other people, it is enough to rule out the classical theory of gravity. So if you believe that the laws of physics should be deterministic and you don't believe in fundamental randomness, then you probably are unlikely to believe that gravity could be classical."
},
{
"end_time": 3922.637,
"index": 148,
"start_time": 3899.633,
"text": " I also spoke to you over email again about a no-go theorem by, I believe it's Marletto, I believe it's her, or maybe she referenced it, but either way, can you talk about what that is and how yours escapes it? Right. So yeah, there's a no-go theorem due to Marletto and Vedral, which essentially"
},
{
"end_time": 3949.753,
"index": 149,
"start_time": 3923.251,
"text": " I mean, in some sense, it's related to this Feynman thought experiment we mentioned where we have a particle that is in some superposition and it produces a gravitational field. And if I can measure the gravitational field, then that would seem to determine which that the particle goes through and therefore rules out having an interference pattern. You can imagine that you have some other theory, which is not quantum theory."
},
{
"end_time": 3979.667,
"index": 150,
"start_time": 3950.401,
"text": " And what they've shown is that that argument still holds. But again, there's that loophole that I mentioned where if the gravitational field has some randomness in it, then those sorts of arguments don't rule out classical gravity in that case. So I think the big question is, do we believe? Well, first of all, for me, it has now become an experimental question. We should go out and measure whether gravitational field has randomness in it. If it doesn't,"
},
{
"end_time": 4006.766,
"index": 151,
"start_time": 3980.333,
"text": " You know, then we've essentially ruled out a classical theory of gravity. Is it conceivable that we can perform this measurement within the next 20 years or so? Right. I mean, in some sense, we already have placed bounds on such a theory. So, you know, we can it's just a question of how much and I feel like we need to better understand the theory before I would be able to tell you exactly what those numbers are."
},
{
"end_time": 4032.295,
"index": 152,
"start_time": 4007.688,
"text": " Because what we've essentially been able to, it seems that in order to correctly predict how much noise you need in the gravitational field, you need to go, it's a fully relativistic calculation, so you need to go beyond the weak field limit. And so we're still performing those calculations. Now Bohmian mechanics was something else that"
},
{
"end_time": 4049.684,
"index": 153,
"start_time": 4032.688,
"text": " I mentioned to you, I'm curious to see the relationship between yours and what's the relationship between your theory and Bohmian mechanics. Right. I mean, there's not there's not an immediate one, but there is. Like, does yours rule out Bohmian mechanics, for instance?"
},
{
"end_time": 4079.684,
"index": 154,
"start_time": 4050.196,
"text": " Well, it's hard to see how you could rule out Bohmian. So I guess that's we discussed before this kind of philosophical side of physics, in particular in terms of the measurement theory of, you know, in terms of these various interpretations of quantum mechanics. And so depending on your flavor of Bohmian mechanics or many worlds interpretation or et cetera, you know, many of them are equivalent from a physics point of view."
},
{
"end_time": 4104.343,
"index": 155,
"start_time": 4079.889,
"text": " Although there are flavors of those interpretations or those theories where there is a physical difference between, say, Bohmian mechanics and some other interpretation of quantum theory. What I will say is that the one thing I like about these classical quantum theories"
},
{
"end_time": 4128.439,
"index": 156,
"start_time": 4105.299,
"text": " is that you don't need the measurement postulate of quantum theory. So I think one of the reasons we have all this discussion of interpretations of quantum theory is because it's very unsatisfying how quantum theory deals with measurement. And we seem to have"
},
{
"end_time": 4158.524,
"index": 157,
"start_time": 4129.087,
"text": " The standard rules of quantum theory where things evolve deterministically and then we perform a measurement and we get the state supposedly collapses and we get a random result and that's not very well understood. On the other hand, in this theory of gravity, in some sense the gravitational field is doing the work for you and is causing states to localize and for the wave function to collapse."
},
{
"end_time": 4179.189,
"index": 158,
"start_time": 4158.865,
"text": " Because the gravitational field is in some sense always measuring where the particle is, one doesn't need to invoke the measurement postulate of quantum mechanics. So in some sense, it's its own interpretation of quantum theory. I see, I see. So for the people who are researching this field of quantum gravity or"
},
{
"end_time": 4208.899,
"index": 159,
"start_time": 4179.582,
"text": " Making quantum mechanics coherent with general relativity. What advice do you have for them for people who are going into this field for young people as well? Just entering math and physics for people who are going into specifically what you study and for people who are researching. Right, I mean, so. I think that so I guess one thing I would say is that I feel like the landscape of"
},
{
"end_time": 4234.138,
"index": 160,
"start_time": 4209.309,
"text": " of gravity research for example is quite a difficult terrain at the moment in the sense that if you're a student and you want to study say quantum gravity or reconciling gravity with quantum theory there's very few games in town. If you're a graduate student for example you can"
},
{
"end_time": 4264.531,
"index": 161,
"start_time": 4235.026,
"text": " work in the string theory group or a loop quantum gravity group. There's a few of those, although that's a much smaller field. And then there's a few of these kind of individual programs which may be involved as a couple, three or four researchers. And it's a very difficult terrain as a student because, you know, the history of physics is that usually it's young people that make, you know, new paradigm shifts or great physics discoveries. And"
},
{
"end_time": 4293.131,
"index": 162,
"start_time": 4265.23,
"text": " I feel like it's difficult these days to work on your own stuff. Because there are these big communities, you're almost like pushed to attach yourself to one of them and become a string theorist or become a loop quantum gravity person. I think that is unfortunate and I think"
},
{
"end_time": 4313.626,
"index": 163,
"start_time": 4293.729,
"text": " What we really need is people to kind of go off in their own direction and do their own stuff. And I think that invariably will mean attaching yourself to some group, but hopefully being given the freedom to go in a different direction. And I think that's"
},
{
"end_time": 4338.183,
"index": 164,
"start_time": 4314.189,
"text": " You really have to find something you're really interested in and maybe a supervisor who has the same interest or you have to somehow go off on your own and that's a lot harder and I fear that is one of the"
},
{
"end_time": 4369.36,
"index": 165,
"start_time": 4340.111,
"text": " One of the reasons that it's so difficult to make progress in quantum gravity is part because it's a really hard problem, but in part it's because there's not a large scope for just going off on your own. You are often just, in some sense, drafted into an existing program. When you say that there's not a large scope, you mean there's no funding or there's not opportunities? Well, opportunities equals funding. Well, it's hard to know exactly"
},
{
"end_time": 4397.09,
"index": 166,
"start_time": 4370.179,
"text": " Yeah, it's a multifaceted problem. I think part of it is that for whatever reason, people like to work on the same thing as everyone else. And I mean, we are social creatures and we want to be part of the community. And so if there's a big community doing something, then it's very natural to want to be part of that community and do that research. But I feel like it's gotten to quite an extreme"
},
{
"end_time": 4422.637,
"index": 167,
"start_time": 4398.166,
"text": " It feels quite extreme at the moment. I feel like even when I was a student, there were various researchers who, I would say, didn't have a firm allegiance to, say, string theory or loop quantum gravity, and you could kind of work with one of them and work on your own approach. Whereas I think now, for whatever reason, the landscape has just become a lot more"
},
{
"end_time": 4451.613,
"index": 168,
"start_time": 4423.524,
"text": " divided into different communities who do different things. And it's much harder to go off on your own. And maybe that's just because it's students worry that if they go off on their own, they won't get a job. I think that's probably a big part of it. Speaking of being a student, my brother was a student, a graduate student, or maybe a PhD student at the same time you were studying physics. That's right. Yeah. You remember Sebastian?"
},
{
"end_time": 4478.404,
"index": 169,
"start_time": 4452.159,
"text": " Of course I do, yeah. He was brilliant. I think we maybe even have shared an office for a while. I think he was working with Gordon Seminoff, is that right? Yes, right, right, right. Do you say hello to him for me? Yeah, I will. Do you have any teachers that have changed your life or gave you a new perspective, ones that are particularly memorable to you, whether in high school or even in university?"
},
{
"end_time": 4509.155,
"index": 170,
"start_time": 4479.872,
"text": " Yeah, I mean... But not your supervisor, because that's obviously... That's obvious, yeah. It's like your father, isn't it? I mean, in high school, I had, I think, a great science teacher, Ping Lai, and so he had a PhD in physics, and I think I learned special relativity from him, and he just gave us a lot of scope to kind of"
},
{
"end_time": 4530.657,
"index": 171,
"start_time": 4509.991,
"text": " explore and think about our own things and so that was definitely you know important that I think I had him as a physicist as a physics teacher in high school and you know in elementary school as well I had a really good it wasn't even my science teacher but it was just a teacher that let you just kind of go off on your own and study whatever you wanted and I feel like"
},
{
"end_time": 4558.575,
"index": 172,
"start_time": 4531.135,
"text": " that letting letting me and letting other students just do whatever you go off on your own and and study what you want is, I think, a really important part of learning. And for me, obviously, is being able to like, you know, I'm fortunate enough that that kind of way of learning has been able to continue into, you know, my middle age. So that's quite lucky. But I'm definitely grateful that I had teachers who let me who let me do that at a young age."
},
{
"end_time": 4587.892,
"index": 173,
"start_time": 4559.258,
"text": " And before I let you go, I'm curious, what has been the reception since your quanta article from the public and then from the physics community? Um, actually the, you know, I'd have to say that the people have been quite open to it. I feel like, um, there's definitely been, um, especially from the relativist community. Well, I would say even from string theorists, I feel like there's been an openness"
},
{
"end_time": 4614.087,
"index": 174,
"start_time": 4588.268,
"text": " Often it's of the form of, well, I don't believe that gravity is classical, but I'm glad that you're, you know, exploring the consequences of that. I'm glad someone is doing that. And so, you know, that's I feel like that's at the at one end. And so there hasn't been there haven't been many people who have who most people have been, I think, quite engaged with the"
},
{
"end_time": 4640.845,
"index": 175,
"start_time": 4614.684,
"text": " For me, what is the most exciting engagement I've had is this community of people who are interested in actually performing the experiment. And so that has been exciting in the sense of I think what we're going to see is a large scale effort to test the quantum nature of gravity. Because I think for a while there was always this assumption that in order to test quantum gravity, we needed to go to the Planck scale. We needed to go to incredibly high energies"
},
{
"end_time": 4661.613,
"index": 176,
"start_time": 4641.271,
"text": " before we could ever make a prediction about gravity and what we're learning now is that actually there's all kinds of things that you can test for in terms of a quantum theory of gravity which do not require Planck energies. So for example, testing whether gravitons can create entanglement"
},
{
"end_time": 4686.783,
"index": 177,
"start_time": 4662.415,
"text": " That's something that doesn't require Planck energies and which we hope is maybe feasible within the next decade or so. So I think that's been the most exciting kind of experimentally. Well, it's been exciting. It's been illuminating to speak to you. Thank you. I appreciate you coming on to the podcast and I look forward to speaking with you again. Likewise. Thanks very much. Appreciate it."
},
{
"end_time": 4702.927,
"index": 178,
"start_time": 4687.773,
"text": " All right. I hope you enjoyed that episode with Jonathan Oppenheim. Something that you should keep in mind is that for this guest and for any of the guests, including all of the backlog of toe, you can leave a question for the guest in this specific format of writing the word query with a colon and then your question."
},
{
"end_time": 4724.002,
"index": 179,
"start_time": 4702.927,
"text": " This applies to any episode, like I mentioned, like if you want to leave a question for Lou Elizondo when he comes on next, if you want to leave a question for Jonathan Oppenheim or Edward Frankel, by the way, the Edward Frankel episode, which is listed on screen now and in the description, in my opinion, is one of the best toe episodes that we've ever recorded. You'll see that we both skirt between technical and personal and emotional and it's super revealing."
},
{
"end_time": 4752.193,
"index": 180,
"start_time": 4724.275,
"text": " We both got more personal in this episode than we've gotten in any other podcast, both of us. Again, Edward Frankel is in the description. I encourage you to listen to at least the halfway point and you won't be disappointed. I've also started this tradition where on every episode or every other episode, I'll highlight a comment and read it because, hey, if you're like me, then you don't have many people to speak to about these subjects outside of conversing online and digitally. This is my way of not only highlighting a certain comment, but also encouraging the community that we've established."
},
{
"end_time": 4777.961,
"index": 181,
"start_time": 4752.193,
"text": " Dear friends, as I sit down to write this, I want to express my deepest gratitude. Your support, engagement, and the passion for the Theories of Everything podcast"
},
{
"end_time": 4798.592,
"index": 182,
"start_time": 4778.302,
"text": " have been the driving force behind this endeavor. We've built a community that shares a fervor for science and philosophy, and for that, I'm eternally grateful. Truly. Despite our 240,000 subscribers and the vibrant community that we've built, the past 11 months have been challenging. Behind the scenes, our channel has been grappling with financial struggles."
},
{
"end_time": 4828.387,
"index": 183,
"start_time": 4798.865,
"text": " Our content, deeply rooted in science and philosophy, unfortunately falls into a category that doesn't fetch the highest ad revenue on YouTube, to say the least. This isn't just our struggle. Even Sabine Hassenfelder recently mentioned a similar issue. During 2023, I've been working harder than ever, which I didn't think was possible, often at the expense of personal and family time. The effort that goes into each Toh episode is immense. I pour my heart and soul into researching and studying for each episode to ensure that we deliver"
},
{
"end_time": 4851.561,
"index": 184,
"start_time": 4828.387,
"text": " The most in-depth and high-quality content, forcing myself to watch myself even, which is extremely cringe-worthy as you can imagine, so that I can improve on each episode. Despite my love for studying for Tohs and the joy I derive from interacting with our guests and community, the financial returns have been far from promising. This letter is a discussion or disclosure by me on what's been going on behind the scenes at Toh."
},
{
"end_time": 4868.2,
"index": 185,
"start_time": 4851.903,
"text": " our struggles have been exacerbated"
},
{
"end_time": 4884.292,
"index": 186,
"start_time": 4868.2,
"text": " Dealing with the sponsor intermediaries, acquiring products for review that were sent across the border, and then paying our dedicated editor have strained our resources. There were even instances where we unknowingly did sponsored spots for free, believing that we were being paid."
},
{
"end_time": 4902.722,
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"start_time": 4884.292,
"text": " That's right. For free. This is unheard of. However, I take full responsibility for these mishaps and I sincerely apologize for any disruption they may have caused to our content. I've had and still have no podcasting mentors nor connections. Zero. Everything's been built from the ground up."
},
{
"end_time": 4922.79,
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"text": " I've learned some hard lessons along the way. There were several times when we interviewed large names and they didn't so much as tweet about Toe, despite them promoting other podcasters. I would be disingenuous if I were to pretend I'm not a tad bit hurt, but that's just how it goes. Luckily, the depth and breadth of our content have always been a point of pride at Theories of Everything."
},
{
"end_time": 4946.544,
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"text": " In fact, the guests themselves invariably remark, on air and off air, how this is the most thorough, the most in-depth of any conversation with them out there. Wonderfully, even the comment sections seem to echo this sentiment. Like, man oh man, that's fantastic. I believe in quality over quantity, at least for Toe, and work to ensure that every single episode is not just informative with meticulous timestamps,"
},
{
"end_time": 4971.561,
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"text": " but also thought provoking and engaging. Hearing from you and the community about how TOA has ignited intellectual curiosity, changed lives, inspired you, helped you through your own dark nights, and provided a platform for discussions that might otherwise be out of reach fuels my commitment. It's an honor and a privilege. I too know what it feels like to be lonely in this space of physics, math, AI, consciousness,"
},
{
"end_time": 4981.578,
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"start_time": 4971.561,
"text": " Without anyone to talk to who doesn't look at you like a nerdy quantum quirkster other than say virtually to keep toe alive and thriving. We're working on several projects."
},
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"text": " So for instance, number one, we're developing an artificial intelligence tool to recover old audio and improve the sound of episodes like the old Chomsky episodes. Number two, there's a lost lecture of Stephen Wolframs from MindFest that we're recovering the audio from by developing again an AI tool. And this tool should prove helpful for future podcasts as well. Number three, we're working on translating our episode into different languages to reach a wider audience."
},
{
"end_time": 5036.323,
"index": 193,
"start_time": 5006.544,
"text": " You'll now see there are several accurately captioned languages. Number four, I would like to do more in-person interviews. Number five, I would like to do compilation episodes on specific topics from several guests. So usually you have one guest speaking on several topics. What about if we just said, hey, does quantum mechanics give rise to consciousness? Yes or no. And then we have every guest on that subject. Or hey, what is the physics of free will? And we have every guest on that subject. Number six, the upcoming Edward Frankel video. Actually, now it's released. And again, it's in the description."
},
{
"end_time": 5057.944,
"index": 194,
"start_time": 5036.323,
"text": " We talk about esoteric topics like the Langlands program, but also childhood trauma and how it's shaped us for better or worse. Most channels of our size have teams, but Toe doesn't. It's just me and the editor, and we each work more than full time. I would be remiss if I didn't mention the darling angel that is my wife, of course. Without her, there would be no Toe. There may not even be a Kurt."
},
{
"end_time": 5087.381,
"index": 195,
"start_time": 5058.251,
"text": " You'll see many other YouTubers interviewing the same people, and that's because it pays significantly more to go with what works. On toe, I've purposefully chosen not to interview high profile guests that I feel like are featured on the podcast circuit repeatedly. Now, the positive side of interviewing people repeatedly is that it opens you up to massive connections and influence. But on the deleterious side, I feel like it would sacrifice a modicum of character in my likely wrong opinion. Instead, I've opted to bring hidden gems like Michael Levin."
},
{
"end_time": 5117.363,
"index": 196,
"start_time": 5087.381,
"text": " who has astounding theories and studies to the forefront and to delve extensively into them. Therefore, I'm reaching out to you, our loyal subscribers, for support. Your contribution would go a long way in helping us maintain and improve the quality of our content, ensuring the longevity of Toe. If you would like to contribute to Toe, there are two primary ways, both listed in the description. There's number one, Patreon at patreon.com slash Kurt Jaimungal. There's number two, PayPal at tiny URL."
},
{
"end_time": 5136.954,
"index": 197,
"start_time": 5117.363,
"text": " In fact, PayPal gives more to the creator. Every dollar helps. It's difficult to underestimate how your support keeps To and myself and my wife going, both financially in terms of the emotional support, knowing there are people who will voluntarily donate something that they could have spent"
},
{
"end_time": 5158.268,
"index": 198,
"start_time": 5136.954,
"text": " warm regards"
},
{
"end_time": 5178.353,
"index": 199,
"start_time": 5158.626,
"text": " Kurt Jaimungal."
},
{
"end_time": 5200.811,
"index": 200,
"start_time": 5178.353,
"text": " they've simultaneously been the most rapturous of my life it's a blessing thank you dearly man thank you thank you so much after the posting of that letter there's been a flurry of support not only from you from the audience but also from other podcasters coincidentally enough theo von a channel with over two million subscribers just talked about this same issue happening to him"
},
{
"end_time": 5225.435,
"index": 201,
"start_time": 5200.811,
"text": " A KFC tale in the pursuit of flavor. The holidays were tricky for the Colonel. He loved people, but he also loved peace and quiet. So he cooked up KFC's $4.99 chicken pot pie."
},
{
"end_time": 5252.278,
"index": 202,
"start_time": 5225.435,
"text": " So yeah, you can keep that money, but you can't get me to shut up, man. You know how many other podcasters wanted to say this shit right now, but can't say it?"
},
{
"end_time": 5285.094,
"index": 203,
"start_time": 5255.094,
"text": " The way that people are able to cheat and lie and manipulate the system. Fuck. It's just fucking kind of sad, man. And yeah, but I just wanted to speak up for myself, man. I've waited a year to speak up for myself. They put us through so much bullshit. And I don't know if there's other people over there that did it, too. And maybe we'll get more information. I don't know. Yeah, I wouldn't do that to somebody. And they did it, man, they did it to some of these people's podcasts is all they had, man. And these motherfuckers did that, bro. So I'm sorry about that."
},
{
"end_time": 5310.964,
"index": 204,
"start_time": 5285.486,
"text": " And I'm sorry for them. And yeah, I'm just happy to have a voice for myself. And that's one thing that we built here that he had nothing to do with. He had nothing to do with. In fact, he stole on our backs once. And I'm not letting these people do it to me two times. So for anybody that had to take that sucker deal over there, I'm speaking for all of us, man. Because I know that some of you guys have said to me that you wanted to say some of these same things."
},
{
"end_time": 5332.688,
"index": 205,
"start_time": 5311.305,
"text": " One comment that stood out was this one by my baloney has a first name."
},
{
"end_time": 5362.585,
"index": 206,
"start_time": 5332.688,
"text": " Kurt, I recall another YouTube channel about a year ago, who was trying to recover from being demonetized, censored and blocked. One day he post and asked all the listeners to do three things that day. Hit like, leave a comment and go back and watch one of the past videos. I think he said just watching the past videos serves the same purpose. As I recall, he got a huge boost because everyone jumped on the opportunity to give moral support through YouTube. But he also gave the PayPal and the Patreon link like you've done. So today on Toe, I hit like I left the comments and I'm going to go back and watch past videos."
},
{
"end_time": 5388.524,
"index": 207,
"start_time": 5362.585,
"text": " So it turns out that watching past videos does wonders for Toe for the algorithm on YouTube especially. So look through and see if there's one that you normally wouldn't click on. That's important because it shows YouTube, hey, the audience that ordinarily likes topic X also likes topic Y. It's not just narrowly topic X. So click on a Toe episode that you think, man, there's no way out. I don't even understand the title of that, let alone think I like it. Click on it, watch it, and I think you'll be surprised"
},
{
"end_time": 5414.48,
"index": 208,
"start_time": 5388.524,
"text": " And at the very least, YouTube will start pushing toe to more people. There's also playlists. So if you want, you can look in the YouTube description. There's several playlists for toe. You can click on that so you can go through episodes one by one if you like. Every episode on toe is edited so there's no large spikes in the volume or loud jumps with music so that people can listen as they sleep. Because I know I used to listen to podcasts as I sleep and I would dislike when they would just quote someone and then the levels were"
},
{
"end_time": 5436.101,
"index": 209,
"start_time": 5414.48,
"text": " I've seen it would wake me and then i can fall back asleep cuz i'm worried it's not gonna happen again that won't happen for tell if you personally want to message me to get in contact for whatever reason for sponsorships for donations for support just telling me what is meant to you if that's what you want and you can email me directly at toe at indy film to dot com so that's."
},
{
"end_time": 5459.241,
"index": 210,
"start_time": 5436.101,
"text": " The podcast is now concluded. Thank you for watching. If you haven't subscribed or clicked that like button, now would be a great time to do so as each subscribe and like helps YouTube push this content to more people."
},
{
"end_time": 5489.275,
"index": 211,
"start_time": 5459.445,
"text": " You should also know that there's a remarkably active Discord and subreddit for theories of everything where people explicate toes, disagree respectfully about theories and build as a community our own toes. Links to both are in the description. Also, I recently found out that external links count plenty toward the algorithm, which means that when you share on Twitter, on Facebook, on Reddit, et cetera, it shows YouTube that people are talking about this outside of YouTube, which in turn greatly aids the distribution on YouTube as well."
},
{
"end_time": 5510.196,
"index": 212,
"start_time": 5489.565,
"text": " Last but not least, you should know that this podcast is on iTunes. It's on Spotify. It's on every one of the audio platforms. Just type in theories of everything and you'll find it. Often I gain from re-watching lectures and podcasts and I read that in the comments. Hey, toll listeners also gain from replaying. So how about instead re-listening on those platforms?"
},
{
"end_time": 5539.48,
"index": 213,
"start_time": 5510.196,
"text": " iTunes, Spotify, Google Podcasts, whichever podcast catcher you use. If you'd like to support more conversations like this, then do consider visiting Patreon.com slash Kurt Jymungle and donating with whatever you like. Again, it's support from the sponsors and you that allow me to work on toe full time. You get early access to ad free audio episodes there as well. For instance, this episode was released a few days earlier. Every dollar helps far more than you think. Either way, your viewership is generosity enough."
}
]
}No transcript available.