Transcription
But what is this talk I hear of emergence from the standard model of particle physics? What's going on there? I thought that's a pretty straightforward grid of what exists and what should exist or how they interact, if I understand the question right. So there are things, there are quite basic things about particles that are difficult to derive from the standard model. So the standard model is, you know, that here is the the quarks and the so up quark, down quark, electron, electron. It's an inventory. So, so we have 12 matter particles, the Higgs boson, and then three forces that it describes. It's an inventory. Yeah. And well, and then it and it tells us about the interactions, but it's got so how particles interact with each other and through which forces do they interact.
Can I ask this? I don't care if I feel stupid or if I seem stupid. Why do you guys call them particles when it seems like everything that I read, once I go anywhere in depth, that it's more like a field of, I don't know, I can't, it's just some kind of amorphous field, but you call it a particle, which makes me think like, little piece of something that's kind of floating around and it's a tiny little. But they always are when we observe them. So it's really about the observation.
Well, but you're right. So the standard model of particle physics is a quantum field theory. So you're right that the the the objects in the standard model are fields, but maybe it's historic nomenclature, but but it's true that when you, you always see, we detect in a particle physics detector an electron. Okay. And it, it goes to a place in the detector. Just to be clear, you detect the signature of an electron. You don't actually see the electron. No, we don't see it, but we see it in the, we see its path that it makes or or other things that it has touched on its way through the system that it tracks. We have magnetic fields and so the charged particles that.
So are you seeing a disturbance in the field that shows up as this singular kind of identifier? I think that I think you have to say yes to that. Is this right? Okay. Yeah. Yeah. I mean, listen, I'm just trying to as a layman get my understanding like on point here because sometimes when you guys talk, it makes what happens is my physical association with the world kicks in and I'm like, well, that can't be because it's not that. And so, you know, that's why I'm asking this.
Yeah. And it's, it's a good question about how how are you to picture the the existence of, you know, solid solidness, this existence in terms of quantum fields. You know, it's a rather abstract underlying description. So that's absolutely true. Okay. But but you're right, what you said that they're just the the particles are the, we'd say the excitations in the field. Gotcha. All right. Um, very cool.
Can you start with the standard model and derive quantum field theory from it? No, no, no. The standard model is a quantum field theory. So and there are there are lots of what we call free parameters. So that ultimately things are put in by hand and there are a lot of them put in by hand. Standard model, that much less satisfying to you as. It's not complete. It's certainly not complete. I mean, for example, one of the most wonderful examples, um, is that so how many matter particles are there in the standard model? So there, so to make up you and me. So what's the the minimal description of us? It's up quarks, down quarks, and electrons. That's it. And the up quarks and down quarks make the protons and neutrons which sit inside the atomic nucleus. And the electrons go around to make the atoms. And that's it, right? Three ingredients, basically. And there's another one called the electron neutrino, of which there are a lot streaming through our heads now from the nuclear reactions in the sun. So the four things, that's it. Now, it turns out that there are also two copies of that set. So, there's a thing called the charm quark and the strange quark and the muon and a muon neutrino. So, the muon, for example, it's, it's a heavy electron. It's identical in every way except it's heavier. And then there's another set, the top quark and the bottom quark and the tau and the tau neutrino. So, three sets of these things. So, the the one that makes up everything, and then another two. Why? We don't know. We don't know why there are three.
So the particles of the universe are in triplicate. Except we are familiar only with that lowest energy regime. Yeah. With the with electrons and and. And then we discovered the other ones and and we, with some very straight little caveats, we know there are no more than three.
Why not? Um, how do you know there are no more than three? Because it was so the caveats are very weak. But so at the, uh, LEP collider at CERN, um, throughout the the 1980s, 1990s, that that machine was, well, it was built in the 80s. It was run through the 90s and.
Did you have a position at CERN for a while? Yeah. Yeah. Yeah. So I, I worked on the, as we're building the LHC, I worked on some ideas for little detectors close to the beams and and so on on the ATLAS experiment. Before that, there was an electron positron collider there called LEP, which was in the same tunnel, and that was really a factory to make things called Z bosons, or Z bosons, and I call them. And, um, they're to do with one of the forces of nature, the weak force. And by measuring exactly the the what's called the lifetime, the behavior, let's say, of that particle, you can see how many things it can decay into. How many, because it basically the general rule in particle physics is if you're very massive and you can fall to bits into lighter things than you will. And the more chance there is, the more things you can fall to bits into, the the more rapidly you fall to bits, right? Basically, so you can measure how many particles this thing can decay into. And so with some caveats about other other generations, as we call them, being extremely heavy and you wouldn't see them, then you can, you can see how many different kinds of particle this thing can fall into. So it's a very famous measurement. So, so we, we're sure that there are three. There's three copies.
Three and only three. And but that looks like the the periodic table of the elements. Mendeleev went back all those all those years ago. So the the pattern that you can see when you, that we all learn at school in the chemical elements, and there's an underlying reason for that, which is quantum mechanics and the way that everything works. But so there will be a reason why there are only those three families. But we don't know what it is.
Father, son, and Holy Ghost. It could be that. That's the reason. So, yeah, so so there's there's a lot of that in the standard model, right? There are a lot of things that we don't know. We don't fully understand the Higgs particle at all. Okay. We've detected this thing. It is. Got the Nobel Prize given. Yeah. And it's a remarkable, um, new property of nature, a new kind of thing in nature. Um, but exactly how that works, whether and why. So, so we know that it gives masses to the fundamental particles, at least in the standard model, that's its job. But but why it gives the masses to them, you know? So there's a, why is the electron the mass that it is? In the standard model, you say because it interacts in this way with the Higgs field. And you go, why does it do that? And we say, we don't know why it does that. So, so there are there are a lot of things in the standard model that you have to measure. And so it's not a theory of everything by any sense.
How come it doesn't contain gravity? Well, so now you're asking about a quantum theory of gravity and. Einstein up with it. Einstein spent a long, the last what 20 or 30 years of his life trying to find such a thing. Don't cop out on us now, Brian. Einstein tried tried this for a while. So yeah, we don't know. So I, I interviewed, I had a great, it was an honor, actually. I interviewed Roger Penrose a few weeks ago and and chatted to him about these things. And Roger Penrose is one of the greats of the 20th and 21st century. Got the Nobel Prize for his work on black holes for really a very famous paper from 1963, I think it was. 56. Was it? 60s, 60s. Where he showed that with very minimal assumptions, a star, a sufficiently massive star will collapse to form a space-time singularity, a black hole, inevitably. Yeah. Yeah. Inevitably. So with, so Oppenheimer and Snyder did it in the just before the Second World War, but with some assumptions about symmetry. And you could say, well, nothing collapses in a perfectly symmetric way, so you wouldn't form a black hole. But Penrose removed those ideas. But he's a great relativist. He's a great, you know, a real expert in general relativity. So he would not, you know, the, I suppose the fashionable way to think about this is general relativity comes from quantum mechanics, but we don't know how. And there's some support for that from the study of black holes.
But there is another way of thinking that says no spacetime is fundamental. You know, relativity is fundamental. Um, so I'm saying that because there's debate. It's not, it's not more. I think most physicists would say quantum mechanics is the underlying theory. Some kind of quantum description of nature out of that emerges.
It's on a roll for how successful it has been. Yeah. In accounting for everything. Yeah. Right. I mean, so why doubt it at this point? Yeah. So we maybe we don't know enough to start. So, so you, I, he, I think I'm not misrepresenting him. He would, he would question whether you really need to have a quantum theory of gravity in the coming from quantum mechanics. I think he would question that. So it, the reason I'm saying that is to say it's an open question. We don't know.
So what about the fabric of spacetime? Is that emergent? Well, so the recent work in the study of black holes, which is the the tiny bit of research I still do. I had a PhD student and postdoc working on this. It's called emergent spacetime. The. Yeah. What is that? So it's the idea that space and time are not fundamental. So spacetime is not fundamental. There's a, let's say, a deeper description, which is basically a network of qubits, to put to do the shorthand, the shorthand version. So Q-bits, quantum bits. So essentially, it looks like a quantum computer. Not absolutely not to say that we live in a simulation, right? No one's going. A little different. Have you noticed that these sounded? I don't really mean that. I Well, no, I don't know whether we live in a simulation. Nobody does. But I'm just saying it's not, it's not evidence for that. Right? But it's beginning to look like you can say, well, a, let's say, a notion of distance can emerge from a network, an underlying network which doesn't have the notion of distance or geometry in it. So that's the. That's you just described subspace from Star Trek. Kind of possibly. Yeah. It's like this underlying substrate where the laws of physics aren't necessarily in play, which is why you can go faster than the speed of light.
Well, information goes faster. Information goes faster. So they communicate in subspace in a in a with witty repartee. Exactly. Even though they're. Even though they're half a galaxy apart. Right? Yeah. It's interesting. I I was thinking about this in another context, actually, because I. So, there would be laws of physics, by the way, that the, there'd be underlying laws, right? And then our laws would emerge from them. We call them effective theories, right? So it's an effective theory, right? Which is which works in the regimes we observe things. But. Effective theory. But I was thinking about this and I have no evidence for this at all. So I I might cause lots of people to write in. But I think that that notion, causality, for example, cause and effect, which is what you're saying, when things, if things can go faster than light, then you can essentially build a time machine and go into the past. You can send messages back into the past if you can go faster than the speed of light, basically. My guess is that that's absolutely fundamental. Um, and so that, so you wouldn't just because you can skip, if you could skip beneath relativity, so to a deeper picture of spacetime, I still guess that causality will be there. Will still be there. I will now, I'm not aware of anyone who's really who's proved that or I'm not aware of any any other anyone's opinion on it. It is my opinion. Yeah. Uh, I don't have any, I don't think I have any evidence for that other than Stephen Hawking.
How is that different from Stephen Hawking's time travel conjecture? Yeah, the chronology protection, protection conjecture. Sorry. So, it's called a conjecture because he conjectured it. Conjecture. It was conjecture. And that was his conjecture. You're right. He said that whatever the underlying laws of physics are, they prevent time travel into the past, which is to say that causality. Protecting causality. Right. Exactly. But I think we're absolutely miles away. We're miles away. This might not be right. This idea of spacetime emerging, although it's quite a popular research field.
It is interesting because quantum mechanics can seem to violate the spirit of that. So we, you probably discussed before on the show, quantum entanglement. Yeah. Want to know about quantum entanglement, spooky action at a distance, he called it. Right. So he didn't like the idea that you can have these widely separated things that can appear to be correlated in such a way that something happens instantly. Now, we know John Bell and others showed, and it's been experimentally tested, that information can't travel faster than the speed of light.
But still, the idea that some kind of, call it configuration, that the quantum state can change instantly seems to violate that somehow, doesn't it? This is again. I heard from the other Brian, Brian. So I was having lunch with him and I just, he said something that just blew my mind. The what might be fundamental in spacetime is this sea of entangled virtual particles where the particles are entangled via what are essentially wormholes. Yeah. Because a wormhole has instantaneous contact from one side to the other. And the wormholes then are the stitching of the fabric of spacetime.
It's called ER equals EPR, which is Einstein-Rosen equals Einstein-Podolsky-Rosen. So EPR is the spooky action at a distance paper, and ER is Einstein-Rosen, which is 1935, I think. Where where they showed that the, the, uh, Schwarzschild geometric, the eternal Schwarzschild geometric, which is the description of the, the, a non-spinning black hole, which discovered very early in relativity, um, has in it, if you extend it as far as you can, a wormhole geometry. So that was Einstein-Rosen. So it's called, I think Leonard Susskind coined the term ER equals EPR.
So what does that mean to you as a thinker in this space? Can can wormholes be the fabric of anything? Yeah, it's part of the answer, one of the answers for how information might get out of a black hole. So it's what's called the black hole information paradigm. Okay, that's that's very cool. Go ahead. Yeah. Well, one of the, one of the pictures people have for that, very hand-wavy picture, is that wormholes somehow connect the interior of the black hole to the external universe.
But all the other virtual particles that fill the vacuum of space. Yeah. Those are particle pairs that come in and out of existence. Yeah, they're entangled. Why wouldn't they be? They're entangled. Why wouldn't that also be in this wormhole discussion? Yeah, it, yeah. So that's it. That's, so, so it seems there's some sense of a, a link. The, the reason it's, it came in in the black hole context is the, people did very complicated mathematical calculations about what happens to the Hawking radiation. So this is the the radiation that is emitted from a black hole from the, and it's really one way to think about it is it's the event horizon of a black hole is disrupting these particles that you talked about, these entangled particles that that are really the structure of the vacuum of space, right? And it kind of disrupts them. And so people were calculating how that radiation, which is entangled with the black hole, how everything behaves as the black hole shrinks. Because because if you think about this black hole is glowing. It has a temperature, losing energy. Through Hawking radiation. Through the Hawking radiation. So not at the moment, because they're much colder than the cosmic microwave background. So the cold things at the moment, but eventually in the universe, they'll be, there'll be hot things and they'll start, they'll shrink. They'll. Be hotter than the background. Yeah. So they'll be net, net flow of energy is out. Yeah. Hot is, I mean, we're talking about, whatever Kelvin. It don't really. But eventually they'll shrink. They're entangled with the Hawking radiation because of what you said, because of these pairs that are coming out of the vacuum. And so you get to a point where you get a crisis, really, where the entanglement can't be supported. It's one way of thinking about one of the problems with the black hole information paradox. So it's all to do with entanglement and what happens. And, um, so from that research, some calculations were done, which are just mathematical, that say that ultimately the Hawking radiation ends up essentially entangled with itself again, right? Is one way to think about it. Um, because, so, so you don't lose information. But those those calculations, can be pictured with hand-waving as representing wormhole holes, some sort of wormholes. They're not the Einstein-Rosen wormholes, actually. So it gets very complicated and and people aren't clear on the interpretation. But that's where the modern resurgence in this idea has come from. I think it's coming from these really very technical calculations about black holes and how information behaves in the in the presence of black holes and wormhole-like structures appear to be one interpretation of what's happening. But I, I'm choosing my words carefully because it really isn't fully fleshed out by a long way.
It's interesting, isn't it? Is it. It is really fascinating to think about, like this is how the, it's like an information tunnel, just for that for the purposes of getting it out. Yeah. Yeah. And then you go, why? And and even, you know, you see the language, for the purposes of, why is it that information is conserved? That looks quite basic. So it looks like another of these basic ideas. Information is not destroyed, right? It becomes massively scrambled. So you can't, in any conceivable future, read the stuff. But it's, you know, the example that's often given is if you, if you burn, but it's the iPad. Let's say you set fire to the iPad. You might say, "Well, surely I destroy the memory." But the, the idea is that you don't. If you could measure everything that came off, somehow all the photons and the whole thing, then in there, scrambled up, the you could reconstruct would be the iPad, even though you set it on fire and all those atoms, like, and every particle that was in there, if you could get them all together, use you would be able to say, "Oh, that was the iPad." Yeah. And you'd have that, your photos in there, whatever it is, you know, you could, in very principle, but really in principle, not practice, reconstruct. So you don't destroy information.
You don't destroy information. It's also determinism. It's also it's called unitary evolution in our language, right? Really, you don't, you don't destroy information. Gotcha. So energy and information, conservation of energy, conservation of information, is, can we think about them like that, or is it not, is that a wrong way to think about it? Well, it's less about information, more about entropy, right? I mean, the entropy, you can move from one place to another, and then there, you can measure that or think about it as an entity. Whereas, okay, I get, I mean, the point we're raising before, obviously, if I send a molecule that has structure, a DNA molecule, into a black hole and it gets ripped apart and then it comes out as separate atoms, I lost all that DNA information. However, that DNA became DNA at the expense of the sun or whatever other input energy that went into it.
That's correct. Gotcha. Right. So, so a, a, you draw a sphere around all the action. So then we could talk about sort of entropy moving, right? You know, without having to to inventory the shape of the DNA molecule. Right? Because the the DNA molecule is a result of the taking energy from another source that put it in that maker. Correct. Oh, wow. Okay. This is great. You're not, you're right. I mean, it is, it's, it's so fascinating, this work on on black holes, black hole information paradox, emergent spacetime, but it's, it's such an early stage that I don't think there are popular articles that really, you know, the language isn't there yet. It's just mathematically. Please.