Our World of Particles with Brian Cox

27:24Does that hole go through more than one country or is it all contained in Switzerland? Yeah, it's France and Switzerland. Wow, okay. Yeah, most of it's in France, actually. Oh, didn't know that. Only a little bit of it's in Switzerland. Okay. So that's one thing. And the other thing is, this Higgs that we've discovered, the question still remains, is it the simplest one, the standard model Higgs? Or is it something more complicated? How does it behave? So the analogy in planetary science would be, here we discovered a moon. And so you go, great. Then you would like to know about the moon. You don't want to just say, we've discovered this moon.

27:57It's a dot. That's fine. As you said, they're interesting worlds. in whatever way you can. For that, you need a lot of them to observe. So it's exciting. And it's challenging because I think for the first time, it's probably true to say in particle physics, we don't know if there's anything else just around the corner, which is bad. But it's also good. I suppose it's just science. I mean, ultimately, it's neither bad nor good. It's the way nature is. That's what triggers whatever next round of physics is complete. You get those people that show up and say there's nothing left in physics to discover.

28:39Well, they'd be so utterly wrong.

28:46There's tremendous progress, FEMA. It's such an exciting time in fundamental physics at the moment. Particle physics, not only particle physics, but we said gravitational astronomy. I mean, the exploration of the force of gravity, black holes, quantum information, which is related to quantum computing and all sorts of, all that stuff is to me utterly fascinating. There's some really interesting stuff. I read some stuff the other day, which I don't fully understand actually, some of the progress in string theory. It's interesting because just as an aside, it's linking, it seems to me, it's linking one of the great mysteries, which is the so-called cosmological constant.

29:29So the fact that we observed that the universe is accelerating in its expansion. And Nobel Prize has been given for the observation, not for the understanding. Yes. He's a friend of mine, who, by the way, didn't believe his... He didn't believe it when he saw it because it wasn't in the air, this idea. He was looking at light from supernova. Right, right. This is supernova. I'm on a paper with Brian Schmidt. Yeah. I'm like a very minor author. You have to scroll down and then my name is... the supernova date, yeah. But it was analysis of high redshift supernovae. Yeah. And I totally enjoyed that work, but he obviously went on and made an entire sort of branch of his career on it.

30:09So there's this remarkable idea which comes from that, which is in Einstein's theory, this idea that you can have a kind of energy in the universe, let's say, or a thing, whatever it is, because we don't know what it is, but something that makes the universe, the rate that space stretches increase, which is, so that's there and it's observed. It's one of the great mysteries because it's, I think it's the smallest number in all of physics by, what is it? It's something like a 10 to the power minus 122 or something in appropriate units, right? Which is absolutely ridiculously, so it's a tiny, tiny, tiny, tiny thing that's causing this rate of expansion.

30:55but it's not zero. And so the question becomes, why is it tiny? Why is it tiny and not zero? Yeah, yeah. And so, because if it were even slightly bigger, we wouldn't be here. So the universe would have been blown apart. So it seems very unusual. But I saw the other week, the other day, actually, that there's some research that's linking that in the framework of a string theory or M theory to dark matter. So there's a kind of an idea that if you fix that, you get a prediction out that there should be dark matter. But it turns out it's to do with extra dimensions and gravitons and extra dimensions and things.

31:35But it's quite interesting. So I think there are some very interesting areas of string theory where progress is being made quite remarkably. Do string theorists need a fuller or better inventory of particles? So for example, are we still looking for a graviton Are we still looking for... You shake a stick and there's a physicist proposing a hypothetical particle to explain dark matter, to explain... Wouldn't it be cool if the dark matter were related to gravitons? This is not my field. I only heard of it the other day, but it sounded interesting. But it just shows you that we... So to go back to LHC, we have the Higgs particle, as you said.

32:20We had expected, I would say most particle physics, expected there would be other particles discovered. There's a particular theory. In that same experiment. Yeah, at LHC. So there's a particular theory, which was motivated by string theory a long time ago, called supersymmetry, which is a property of the universe. It's been around for many decades, this idea. Yeah, and it came initially from, either from string theory or from some other, and got incorporated in. I can't remember historically which way it came. But it essentially predicts that there are double the number of particles that we see, fundamental particles of this energy.

33:00And they would have been great candidates for dark matter, by the way, which is an astrophysical discovery. So we should say, I suppose, the one sentence description of dark matter is that we see the universe. There's far much more matter in the universe than we can see. See, I would put it differently. I would say there's far, it's not dark matter, it's dark gravity. You say matter, we don't know what it is. Well, it's true. So you see it through its gravitation interaction. So it's dark gravity. See, otherwise you get newspaper headlines say, oh, we must abandon our ideas of dark matter. Well, if it's not matter, it's still there.

33:40It's misnamed. Yes, I see what you mean. I mean, that's a cool newspaper, by the way, that would have a headline like that. That it goes there at all. It's usually about a football player. So I'm on board with that newspaper. I'm just saying, if we don't know what it is, we had no business calling it matter at all. So the thing to say, though, is that - Call it dark gravity. The best - Which sounds cool. So you build models, and it is true that the best model that fits all the data, which is not just the way that galaxies rotate and collide and the way that galaxies kind of lens light and all those things, but also the cosmic microwave background radiation, which is the oldest light in the universe, and how that worked and how the ripples, the sound waves went through the early universe and all that.

34:25You put it all together and it fits if you have a light-ish particle that does not interact with light, but interacts weakly. So this would be another category of particle in the particle soup. that has gravity but doesn't interact electromagnetically or only very weakly. So you can't see it. And so it's just, all right. So that's a model, though. You're right. So that's a model, which is kind of, I would say, the baseline model. Yeah, it's the assumption. People assume that. And I don't have a problem with it, but if anything happens to that model, it gets shown it can't be true. People say, oh, then there is no dark matter.

35:04No, there's still dark. It is a measurement in the universe. Yeah, I understand. We've just misnamed it. Yeah, I agree. The measurement is just galaxies spin around too fast. But too fast, there it is. Or the way they collide and so on. There's quite a lot of independent measurements of this thing. So tell me about a graviton. I mean, is that a real particle? I think most physicists would say that quantum mechanics is the base theory. I think the reason I'm careful is because there are some people who would say general relativity is a thing. Space-time is a real thing and all that. But I think generally most people would say quantum mechanics is underlying it.

35:41And that, if you have an interaction... In other words, quantum physics is foundational to the universe in ways that even general relativity would not be. Yeah, so we could talk about this later, but the idea that space and time, or space-time, emerge from a quantum theory is very fashionable at the moment. Partly because of the study of black holes, so we could talk about that. So given that, then you... So I should say, just for people who are watching and listening, so how would we picture the electromagnetic force in particle physics? So we know that if you put light charges together, they repel and so on.

36:18So what's happening there? Or if you bring magnets together, right, they repel each other. Everybody knows the North Pole together and they repel. So what's happening? In particle physics terms, you picture that as the exchange of a photon. It's a particle of light that goes from one particle to the other, and essentially carries the force. So that's what our particle physicists would picture, that force, all forces. Have we successfully applied that to gravity? No, so that's the point. Give me a more resonant no. They're very strong. I suppose I'm trying to find the right word for it. That's why I said conviction.

37:01I don't know if any physicist would disagree. Because if you can't fold it into the quantum world, you don't really have a right to start looking for a graviton. Because you're going to say the graviton is the mediating particle. Yes, so it's the photon. In the way the photon is the mediating particle. So, and that's, I don't think you'd find anyone who would disagree with that statement. Okay. Although, I don't think you would. Although, it is true to say that because gravity is so weak, so this is the other thing to say, It is tremendously weak compared to the other three forces of nature of which electromagnetism is one.

37:38Here's what I tell people. You've surely done this in class. They say, well, how weak is gravity? Well, I can pick something up off the floor against the wishes of Earth. Exactly, yeah. The whole Earth is pulling on this ball, and I can just pick it up off and kick it into the goal. And you're using electromagnetism. That's what's happening. So your muscles and all that things. This is all electromagnetic force, which completely destroys, as you said, the gravitational force. but gravity is only additive so it only adds up in the universe so it is the dominant force on cosmic distance scales that's the point about gravity here's a calculation I haven't verified but it sounded legit very verifiable I was too lazy if you take the space shuttle in its glory days and you take one remove the electrons from one cubic centimeter in the nose of the main tank and take all those electrons and put it at the base of the launch pad, it would not be able to launch.

38:38The attraction between the electrons at the base of the launch pad and the net positive charge at the top is enough to prevent it from launching. Yeah. That's a cool idea. Yeah, yeah. I can see that that would be good. Yeah, yeah. Actually, it would burrow a hole. so it's not a realistic experiment but to get some sense of the forces involved yeah that's a really nice okay so gravity's weak that somehow bails you out of this problem well it just means that you can't we don't have experimental access to them okay because it's so weak and so whereas we do have experimental access to photons yeah unless you could potentially have access if there were extra dimensions in the universe that are configured in the right way.

39:24These physicists are always throwing in extra dimensions. Whenever you need it, you know. It is interesting, though, that string theory works in 10 dimensions and only 10 dimensions mathematically. So that's an interesting observation, right? I don't have the background to be an authentic string theory skeptic, but I know physicists who are, and so. Yeah, I think there are. I mean, it depends. I think it depends what you mean by string theory. I mean, there was, if you go back, you know, a few decades, you talk to Brian Green, for example, and when he started working in this area, he was - He's a friend of StarTalk.

40:02Yeah, yeah. He's been honest several times. He would have, and his great book, The Elegant Universe, is a beautiful description of string theory. And so I think the idea initially with the hope was that you'd have a theory and you could write it down. It's a theory of everything and it would predict the universe as we see it. And then you go home and you're done. I think that's gone as an idea. But the basic idea of these... I mean, why is it called string theory? It's because particles are not point-like. These strings are like little strings, little loops. But that idea, I think, is still at the foundation of most modern theoretical physics in this area.

40:40But it's got much more complicated, and it's been much harder. I think the initial idea that you could just predict everything from one number maybe has gone away. One simple equation on one line. But there is tremendous progress being made in string theory. So it's not gone away. It's just become more complicated, I would say. Well, thanks for catching me up on this. At this conference, you're giving a talk on black holes. Yeah. And there was some recent announcement, the biggest jet from a black hole ever discovered ever, ever. However, when I was asked about it by the press, I simply said, there's always a biggest jet in the universe.

41:19And so now this one is that. It's the A380. Okay. The Airbus A380. It's a fantastic aircraft. Did I undersell the significance of this huge jet? So what if it's the biggest one, unless there's some interesting physics that's coming out of it? the area that i have i share a phd student who's working in the area is more is more theoretical it's about quantum information the way the information behaves inside and outside a black hole what happens to things that fall in but um in terms of the astrophysical work that if you go back you know not long ago we didn't really have any observation of how uh things behave in the vicinity of black holes and so i would put it in that box we've got several observations now we've We've got the radio telescope observations from the Event Horizon collaboration that has shown us how the magnetic fields work, for example, around the black hole in the Milky Way.

42:15We've got these jets, which are giving you access to the magnetic structure, presumably in the way that they spin. Thank you for putting it in that context. Now I can understand. It broadens the astrophysical data set on which we can sharpen our hypotheses for what's going on. Yeah, because they're hard things to observe. And of course, you can't observe the interior because it's inside this thing called the Event Horizon. But what you can do, and we are doing, is observe the way that material behaves in the vicinity of them. Or the other remarkable thing we've been able to do in the last few years is watch them collide and see how the ripples in the fabric of the universe come out, and we can detect those ripples.

42:54So all these things are allowing us to probe these objects. And it's worth remembering that they were present. They were described. non-spinning ones were described fully by the work that Carl Schwarzschild did in 1916 so months after Einstein had published the theory of general relativity he didn't know it at the time but the mathematical description he found which describes how space and time are distorted in the presence of a star a non-spinning star is kind of important those fully describe a black hole that isn't spinning If I remember correctly, he would die in the First World War. I don't think he made it out of the war.

43:37No, he died in 1916, so shortly after. Not in action. Oh, it was not in action. I think he died from diseases. It was on the Russian front. Okay. It could be war-related, but not from an injury. Yeah, it was. I think it was, you would argue, war-related. Yeah, so we've got more than a century of mathematical foundation for this. And then you go forward to 60s. With no data. No data. No, and then, so it takes another 50 years, by the way, for someone to work out what it looks like for a spinning one, which is Roy Kerr. It's a famous Kerr solution. But those two solutions are there. They're in Einstein's theory in a sense.

44:17And they describe the black hole. But observing them is something that we haven't been able to do until recently. And multi-wavelengths as well. Yeah, so now we have radio observations, the gravitational wave observations. I'll be a little kinder to that. Because the thing is, as you said right at the start, science is about, yes, having ideas, building theories, and so on. But it's really fundamentally about testing those theories. And so we can talk about these theoretical objects, black holes, but really, and they are rich theoretically, but ultimately you've got to make observations. And that's where these jets and seeing how material behaves which gives you access to the magnetic fields and how the thing's spinning and what it's...

45:03That's important.

45:28let's talk about your work with the public you you said earlier you you share this commitment that Feynman declared duty to bring science to the public. You don't, you not only talk the talk, you walk the walk and you have spillage everywhere. You know, you've given tours, public tours in, in, in Australia, across Europe. And if I remember correctly, you're coming back to the United States next spring to give a tour across the country. Yeah, yeah. It's a tour that's been going on for quite a long time. It wasn't meant to, really, but we've ended up playing to over 400 ,000 people across the world with this tour.

46:12Wait, wait, wait. You're not a musician. You say playing. Playing. Get your vocabulary straight. No, look, I'm rock and roll, basically. I always have been at it. Playing to 400 ,000. We have five trucks and two tour buses. It's brilliant. So I'm reliving my life as a... So did I see a version of that when you came to the city? Yeah, it was very early on, just after. It was just after. Yeah, you have these screens that interlock. Yeah. And then the whole stage is. Yeah. And that was a very early iteration of this. And so it's changed a lot. Before I laid it to rest, this tour, and develop another one, I wanted to bring it back here in the form that it is now, which is so radically different from what it was three years ago.

46:50Okay, and it's celebrating the universe with and for the public. It is. The public. It also morphed into, there's a version that I do with the symphony orchestra, which is great fun. So I did it at Sydney Opera House, actually, initially, last year. And it's a big orchestra, because it's a 90-piece symphony orchestra because of the music that I chose. And so the reason, by the way, as a slight digression, it's part of this tour. The classical music is a big part of the tour. So it starts with Sibelius' Fifth Symphony, third movement and that was because a conductor friend of mine called Daniel Harding I said to him what should Stanley Kubrick have used in 2001 as a joke like what should he have used he immediately said Sibelius Fifth Symphony and it is it was written in 1915 same year that General Relcivisy was published but it's the basis of almost every science fiction theme you've ever heard you'll hear everything and it's beautiful and so the idea which I've always strongly believed but it came to my mind as I was doing this tour, is that if we're talking about deeper philosophical questions, which are raised by cosmology, I say right at the start, what does it mean to live a finite, fragile life in an infinite, eternal universe?

48:06And I say, of course, I don't know the answer to that. Is that uplift people or depress them? Well, but as you know, the moment you contemplate the scale of the universe, and I should say, we don't know whether it's infinite. We don't know whether it's eternal, right? But it could well be infinite and eternal for all purposes it kind of is right on a human scale anyway human scale yeah so so the immediately when you contemplate the size and scale of the universe you ask questions about our place and quite vividly what does it mean to live these little finite fragile lives and so i think i try to approach those questions and you realize so i realize that there are other lights you can shine on that problem and science is a necessary bright and vivid light that casts a very well delineated shadow, which is giving us some, obviously, it's the framework within which we operate.

48:58But there are other lights. So you realize that Mahler, for example, so we use Mahler in the classical concepts. Mahler thought a lot about what it means to live a finite, fragile life. And he gave a very eloquent answer, many eloquent answers in his symphonies. And he was once asked, by the way, what are you trying to say? What's this answer you and he said well if i if i could say it i wouldn't have written the music good answer you have this music i love that so so the music so there's composers that i chose and that part that they are in the tour that we're going to do this coming year uh next next day 2025 um they're in there as music the composers were chosen because they explored this question and gave very eloquent answers.

49:43So it adds to, I think, the more philosophical exploration of the questions that are raised by the science. What's the name of the tour? It's called Horizons. Horizons. That's easy enough to remember. Okay, very cool. But there's a lot of black holes in it as well, I should say. So it's an exploration of the ideas that I find interesting. Black holes are horizon of its own. They have horizons, yes. But also life in the universe, the origin, evolution of life, with speculations on, we could talk about it, speculations on how many civilizations there might be as a guess. Well, this thing about life in the universe, you've done many, many TV series, and most recently one on the solar system, where the search for life is a main theme.

50:28Well, yeah, we just saw, as we speak, last week the Europa Clipper spacecraft was launched on the way to Europa. We have an entire show devoted just to that. We visited the Jet Propulsion Labs and felt the excitement of everyone there. It's great, isn't it? It's the first spacecraft I've seen, major spacecraft being built. So I saw the Clipper. And the thing is, the scale of that thing, it's the largest spacecraft, isn't it, that's ever been sent into the Air Force. Well, if you add the... Oh, the most massive, I think. It may be, but there's another important fact. Solar panels have gotten more efficient.

51:01In the day, back if you were going to explore beyond the asteroid belt, You couldn't use solar panels if the intensity of the sun wasn't high enough. This one has a very deployable, large solar panel that'll help it along without having to rely entirely on the nuclear decay of plutonium. Yeah. So it's a huge spacecraft. Yes. And the point is that Europa, Jupiter's moon, is a prime candidate for a habitable world. What we know, almost certainly, And I'm always, the people who I know who work on the mission say, don't say we know. We're almost sure there's a saltwater ocean below the surface. I think it's pretty indisputable now.

51:44So we're pretty sure it's there. Yeah, but whatever is the skepticism, what would it be were it not a global ocean? Yeah, it's very difficult to be because, and that's from many measurements. Was it made of ammonia? I mean, there's not, you know, water molecule is not rare. Yeah. So it looks like saltwater. Yeah, and we have a lot of comparative planetology with is it the Arctic? When it freezes over, you have these chunks of ice that will break and refreeze and readjust, and you can compare the images, and you'd think you were looking at the frozen Arctic. Yeah, yeah. So it looks, and there's more water in that ocean than all the oceans of the Earth combined, geologically active.

52:24There are questions about how the ice cracks and moves on the surface. So it's a fascinating mission. So that's Europa. Mars, of course, which you've probably spoken about many times on this podcast. Enceladus is another one, Saturn's moon. Even out to Pluto. Enceladus is the ones we see the plumes, geysers, I guess. Yeah, yeah. At the right sun angle, you can see. Who took those pictures? That must have been Cassini. Right, right, right. Yeah. And also there's some measurements from Cassini, the particles in those jets of water, which are consistent with hydrothermal vent activity. on the floors.

53:02And hydrothermal vents are one of the plausible candidates for the origin of life on Earth. Yes. So you seem to have everything. The one thing I think Europa's got that arguably nowhere else has is it looks like that ocean has been there for many billions of years. That's the baseline scenario. And we evolve life in less time than that here on Earth. Yeah, yeah. It was present, what, 3.8 billion years ago? Yeah, 3.8-ish, yeah, yeah. And the Earth's four and a half billion years old. Right. Yes, so it looks like you have a habitat that's been stable there. And I think that you can't claim that with anyone else.

53:36In fact, you know, it was taught that it took about a half a billion years on Earth to get life going. But we were able to revise that number down. Because in the early Earth, these periods of heavy bombardment, it's not fair to start the clock while we're still getting slammed by, you know, still accreting leftover rocks from the solar system. As the temperature of the surface of the Earth is high enough to prevent complex molecules. Give us a chance, please. So the periods of bombardment subside, Earth's surface cools, now start the clock. And then it's about 100 million years. Yeah, yeah. And it's like that.

54:12Yeah, which is one of the reasons I think that, I think if you speak to many biologists, they would say, that might suggest that given the right conditions, then whatever the origin of life is, there's a reasonable probability given the right conditions because it happened quickly here. Right. But that's not definitive in any sense. But it's certainly tempting to go there. But what I find very interesting, Dan, is though, when you ask, okay, but when did life get more complex than a single cell? Then, I don't think there's any evidence in the fossil record back beyond about 600 million years ago.

54:47It took a while. Yeah, we languished as single-celled creatures. Three billion years plus, it seems. So I think people who think about this problem are honest about that. And so in the search for life on other planets, we're really looking for a single-celled organism. Well, it would be remarkable to see anything more complex. Well, it would be remarkable to see a single cell. Because then you'd know, especially if it were biologically different. So you can really show that it's got a different origin. Because it's worth saying that on Mars, the material is exchanged between Earth and Mars. So it's not obvious that you couldn't have life exchange.

55:22And you make all these points in your series. Yeah. Right. So where can people find your series? It's streaming, I presume. Yeah, yeah. We've got the new one is just on the moment, actually. That's what I'm about to say. So the solar system. So that will appear on Apple, I suppose, at some point. Apple Plus. And other places. Yeah. I mean, it's the moment. It's on the BBC. So it's streaming on the BBC, and then it will head off around the world. One of the coolest things, I think, about Europa is that the habitat, the potential habitat requires Jupiter because of the heating. It's liquid because it's orbiting around a big planet.

55:57But it also seems to require, well, it requires the other moons, Io and Ganymede, to keep it in this orbital resonance, which keeps feeding the energy into the gravitational field. The family affair, yes. But it also might need the material from the volcanoes of Io on the surface of Europa, because they might provide what we call the oxidant, right? So life is... So you're saying that the Io, which is badly stressed... It's just one big volcano. It's one big volcano. So it spews volcanic substance faster than escape velocity, apparently. Which lands on Europa. And it goes into pathways that intersect other moons, Europa included.

56:44You can do this for a billion years. And then the chemistry... and then it gets irradiated. It helps out the chemistry. Yeah, so one of the theories that I've spoken to people who are on the Clipper mission said is that that's part of the battery of life, that chemistry. So life, I can't remember who said it, but he said life, someone said it's an electron looking for a place to land. That's what life is. In one way, you can see life as electrons moving around. But that means you need the chemistry. Is that all we are? Just electrons looking for a place to land? But that's what a description of life.

57:19I'd rather be dust in the wind. Whatever. Oh, yeah. But I find that wonderful because then you've got this habitat, which is a system. And as you said, comparative planetology you mentioned earlier, it's also true of Earth, isn't it? You can't understand Earth without understanding the system, the solar system. You need to understand the moon and how it stabilizes the spin axis, and you need to understand, of course, the sun, the way it interacts with Earth, and so on. I'm a few years your senior. I don't know if you would remember this, but I definitely do. The era where no one was thinking or caring about moons in the solar system.

57:55We have a dead moon orbiting us, oddly large, but fine. Let's go look at the planets. And so every mission out to the planets, they looked over their shoulder and found moons, which had way more geologic diversity than anything we're finding on the planet. I found it interesting. I mean, when you were in school, Did, where were we in the... No, pre-Voyager, well, Voyager, so... See, I'm pre-Voyager, and Voyager turned the moons into worlds. Yeah. That's what happened. Yeah. Yeah. So the idea you have a habitable zone in a solar system, which is the zone within which, if you have a rocky planet orbiting and everything's right, and the atmosphere's right, you could have the conditions to support life on the surface.

58:36Or liquid water on the surface, let's say. Right, right. And so... But that turned out to be needlessly limiting. Well, exactly. So you just say, well, Mars, Earth, Venus in our solar system. That's it. But then you find inhabitable zones around gas giants. And that, as you said, that was the great discovery of Voyager, I would say. Yeah, it began with Voyager, really, for sure. Yeah, which would be early 1980s, right? So I'm delighted, even as a particle physicist, you get to also platform the solar system because you have the name recognition. But that's why I said I started with astrophysics.

59:11I really just wanted to be an astronomer. So I've always been. I've got a telescope. You confessed to me. No, I did. It's a safe space to do that. I ended up in particle physics. It was almost, so I was doing astrophysics. That's what I was doing. And I thought, I want to be an astronomer. The University of Manchester has the Jodwell Bank radio telescope, for example, which is one of the big radio telescopes in the world still. And so I - That wasn't the one that discovered the first pulsar, was it? No, that was Cambridge. Cambridge. Cambridge, okay. Jocelyn Bell-Bernel. Jodwell Bank discovered something else.

59:39I mean, Jocelyn, Jodwell Bank. It was one of the first, so it's one of the pioneering. It does a lot of the work. the crab pulsar and so on. But it was, so I thought I'd be an astronomer and I have a telescope. That's what I do. I sit there and look at my telescope. You're in the club. We'll accept you in the club. Even though you drifted to particle physics, we'll accept you. And space exploration. So that's all, but it was at university. I just got interested in mathematics. I didn't think I was very good at mathematics at school. But I found out with a bit of practice, then I enjoyed it. So I ended up really getting more into theoretical physics and went that way.

1:00:17So that's why I ended up in particle physics, really. But then now, of course, every opportunity I get, I seem to drift back. Because the universe is cool. I don't want to brag about the universe. And black holes, actually, are where they intersect. Absolutely, particle physics and general relativity, astronomy, intersect. And the Big Bang itself, of course. Yeah. Yeah. Yeah. With your particle physics hat, where are we with neutrinos now? I thought they're sort of fully understood. We solved the neutrino problem in the sun. A Nobel Prize was given for that. Is there anything left to discover about this elusive particle that belongs in the, I would say, tree of life, in the particle tree of life?

1:01:02Yeah, I mean, neutrinos are fascinating things. They're very, very, very, they're almost massless, but not quite. light and that matters that should ring bells you know it's like why that's the thing about science isn't it you go well why is this unusually light or maybe it isn't maybe the other things are unusually heavy but what but but it's telling us something and it's only neutrinos that how hard it is to interact with them that gives me any belief at all in some other set of particles that might exist that we don't interact with because neutrinos are our own species well they interact through a the weak force.

1:01:39Yes, but that's us. That's our little world here, right? Any other symmetric particles, there are other forces that mediate them? Is that correct? There would be. So if you have extensions to the standard model of particle physics, then you can have forces that change things into other things and so different forces. But as far as we know, the zoo that we have discovered is described by the three forces. the strong nuclear force, the weak nuclear force, electromagnetism, and then hanging out there, as we've discussed, is gravity in really a different framework at the moment. So I corralled Steve Weinberg in the elevator one day, and a physicist, I'm telling you, I'm telling the audience, a particle physicist.

1:02:28One of the greats. Yeah, and he went to my high school. Did he? Allow me to add one of our eight Nobel laureates from my high school. and I said, how can you live with yourself at night given how many particles there are? Come on, I lost count. What does this mean about our universe? And he said, it's not how many particles there are. It's how many laws we have that describe them all. Yeah. And it's only just a few. Yeah. I said, damn, good answer. Yeah. Yeah, I remember Steven Weinberg. Good answer. I think I'm right in quoting him as saying that he almost wished black holes didn't exist because they're so perplexing that it would be just easier.

1:03:20And he was kind of joking, of course, because physicists love a mystery, but he was almost like, this is too difficult. This is too bizarre. Maybe nature doesn't make them. Oh, I got it. So you see he's invoking human limitations on the capacity of nature. Well, he was kind of joking. and he was just saying these things are so baffling and so weird. In some ways, I'd rather they weren't there. Did he say that in his old age so that he was getting tired of solving the universe? He was joking. So we're still trying to explore neutrinos. And as I understand, there's a new neutrino experiment that just came online.

1:03:54I mean, there are several. I mean, the fundamental question, they do seem, the reason we're interested in them, just we're interested in them because they're three of the 12 fundamental particles. So we are made of basically three particles. That's us. And the electron, protons, neutrons. Well, no. So the protons and neutrons are made of quarks. Oh, so, okay. So quarks, down quarks. Let's start from the Greek. We're made of atoms. You can start with we're made of atoms and we're atoms made of. In Greek means indivisible. Yeah. That's what that word means. Yeah, and it is remarkable, by the way.

1:04:35You say the Greeks 2 ,000 years ago. We only discovered the structure of atoms in the 20th century. Or that atoms existed. Yeah, it was up for debate. The turn of the 20th century, it was one of the debates in science. Is there such a thing as an atom? Yeah. It's incredible. Incredible, yeah, yeah. And Einstein, indeed, in 1905, one of his famous papers was on Brownian motion, which one of the three famous papers in that year. The other one was special relativity, and the other one he got the Nobel Prize for was the photoelectric effect, the third one. Yeah, Einstein, we should just retroactively give him like a dozen Nobel Prizes.

1:05:10It's astonishing. He didn't get the Nobel Prize for relativity. He got it for basically the foundations of quantum mechanics. Yeah, yeah. We discover that matter's made of atoms, and then we very quickly discover after that that the atom is electrons. Initially, we have this almost solar system-like model that it's a nucleus, a dense nucleus with an electron going around it. And then we discover the nucleus is made of protons and neutrons. That's 1930s, by the way. That orbit model is still the symbol for an atom. Yeah, the atomic energy. We kept it just because it's classic, but atoms look nothing like that.

1:05:46No, no, no. So then quantum mechanics comes in, tells you you can't have that because charged particles moving around in the vicinity of other charged particles radiate energy away and they wouldn't be stable. and that was known, of course. And so then you find the nucleus is made of presence of neutrons. And as I said, the neutron, it's a 1930s discovery. So we're not that long ago. I'm amazed when so much, you know, we're now in the centennial decade of the discovery of quantum physics back in the 1920s. And the whole 1920s was done before we discovered the neutron. That's crazy. Yeah, it's almost living, it is living memory for some people just about this.

1:06:25Okay, so let's get back to the fundamental particles. Then we discovered that the protons and neutrons are made of quarks. Quarks. So they are, as far as we can tell, point-like objects. So they're fundamental. They won't be, but as far as we can tell, they are experimentally. So we have the photon, the electron, three quarks. Well, let's take the matter particles. So the up and down quarks make up protons and neutrons. So a proton is two ups and a down, and a neutron is two downs and an up. Got it. And we have two quarks per energy stratum here, correct? Well, so then we discovered, so we have this nice thing.

1:07:02So we have the electron, as you said, the up and down quark, and then the thing called the electron neutrino. So we just talked about neutrinos. Okay, so only four fundamental particles in anything we know or care about. So we have four of them. Yep, that's it. So I can construct you out of these particles. Yes. If I had the recipes. Yes. But then, so we have four of them. So that's it. There's four of them, and then the forces that mediate the interactions, right? Okay. And which we can also think of as being carried by particles, as we said. Okay. We have the photons. The massless particles.

1:07:35The electromagnetic force. We have the W and Z bosons, which do the weak nuclear force, and the gluons, which do the strong nuclear force and stick the quarks together. Aptly named gluons. The gluons, yeah. Okay. And so that's it, it seems, except that there are two copies. of those that are identical, except they're more massive. So there's the charm and strange quarks and the muon and the mu neutrino. That's another family. That's the next level up in energy. They're more massive. More massive, okay, okay. So you have the charm and strange and the muon and the mu neutrino. And then - Then you have another one.

1:08:14Yeah, which are the bottom and top are sometimes called beauty and truth, depending on how you want to do it, the quarks. and then the tau and the tau neutrino. And that's it, as far as we can tell. So those are the matter particles. So 4, 8, 12 fundamental particles. And their antimatter counterparts. Yeah, and then the antimatter counterparts. And so that, why, we don't know. So why there are three, and experimentally proven, really, with some very small caveats, only three generations, only three families of these things. Is there a reason for there to be only three? Could there be five or ten?

1:08:52So we don't know. It must be something to do with the underlying. So it looks like a periodic table. So remember, you go back to Mendeleev and the periodic table. How do you understand that pattern in the chemical properties of the elements? You understand it when you know that everything's made of atoms. Yeah, I mean, the chemists arranged it but didn't have any understanding of it. No. So quantum physics. Well, you need to know the structure. You need to know that there's a nucleus and there's, you know, hydrogen's got one electron and helium's got two and carbon's. Alchemy only gets you so far.

1:09:23Yeah. So you understand chemistry. You understand the pattern when you understand the building blocks. Okay. So we don't know why that pattern is there, but it's clearly telling us about the building blocks or the underlying theory, which we don't know. So it's one of the great mysteries. So that's the zoo of particles as we know. And then there's the Higgs. And just to be clear, when I attacked Steven Weinberg in the elevator, most of the particle identities I was referencing are different combinations of different quarks that come together. Yeah, so all these, like you said, in the 50s, people were discovering all these things.

1:10:00And they're different combinations of ups and downs and strange and charm and bottom and so on. So they exist in our universe, but again, they're made of more fundamental properties. Yeah, so basically these things, the proton and neutron, they're kind of analogous to an atom in a way. So they're a thing, they're quite big things in particle physics, and they have an internal structure. Within themselves, yeah. And one of the things that I was involved in that we did back in Hamburg all those years ago was we were mapping the structure of the proton. So we're saying, what is in the proton? How does it work?

1:10:35Mapping the interior structure of the proton. Yeah, and we need that. We needed that for the LHC. So we need, because we collide protons together. So we have very detailed maps, if you like. They're called structure functions, but they're maps of the proton. Well, Brian, thank you. Hi, pleasure. For joining me. I always love talking to you and being on this podcast. Oh, no, we're kindred spirits in this world, and I wish you great success with your spring tour. Does it go beyond the United States? Is it a world tour? It has been a world tour. We've been to, I don't know, 20 or 30 countries. As I said, we're probably approaching half a million people who've come to this.

1:11:12Okay, so that's the... We're at the end, really, of this one. Oh, okay. And so I just wanted to bring it back here. It's changed so much. We kind of started in the States, actually, in its proto-form. And now I've loved doing it so much, and I just wanted to bring it back. I just like the idea that a science talk is being given, but there are trucks that have to unload the staging for it. It's proper rock and roll. I got roadies I got everything Do you have a tour t-shirt with the cities on it? Yeah Oh yeah I should have brought one to show you I want one of those shirts Oh my gosh Oh we've got everything And we've done so many shows I don't know how many it is 150, 200 They don't all fit on one t-shirt So we've got different t-shirts for different regions of the world Physics takes the world Very good Brian Again thanks for being on the show This has been an exclusive conversation between me and my good friend Brian Cox from the UK, who's coming stateside with a tour.

1:12:11And we're going to look for the solar system on Apple. It should be around, yeah. Yeah, it does its BBC. How many episodes is it? Five. Five episodes, we'll look for it. All right. This has been StarTalk. I'm your host, Neil deGrasse Tyson. As always, keep looking up.

1:12:35Thank you.