The Infinite Monkey Cage - Higgs Boson

Episode Date: March 20, 2024

Brian Cox and Robin Ince visit CERN’s Large Hadron Collider in Geneva in search of the Higgs Boson. Joining them on their particular quest is comedian Katy Brand, actor Ben Miller and physicists Tevong You and Clara Nellist. They find out which particle is the one you’d most want to spend time with at a party, how cosmology is inspiring experiments in the collider and why the Higgs Boson - known as the 'god' particle' - is of so much interest to science.Producer: Melanie Brown Executive Producer: Alexandra Feachem

This is the BBC. This podcast is supported by advertising outside the UK. In our new podcast, Nature Answers, rural stories from a changing planet, we are travelling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working.

Learn more by listening to Nature Answers wherever you get your podcasts. BBC Sounds. Music, radio, podcasts. Hello, I'm Brian Cox. I'm Robin Ince, and welcome to The Infinite Monkey Cage. And today, for the final episode of this series, we have brought Brian home, because we are in Geneva, at CERN,

home of the ATLAS experiment, the Large Hadron Collider, and, of course, also, as we experiment, the Large Hadron Collider, and of course also, as we know from the British tabloid press, the world's premier creator of bonsai black holes, little mini black holes that will undoubtedly ultimately destroy civilization. So how do you make the black holes here, Brian? Well, the first thing to say to the listeners is this is drivel, but you know when you want to be remembered for a quote, like Carl Sagan's Billions and

Billions, which he never said, or something like that. The cosmos is everything there is, everything there was, and everything there ever will be. We are all made of star stuff. The stuff of us is the stuff of the stars. So what's your equivalent then? So when you look up my most cited quote

in all my career, public engagement, public understanding of science, it's anyone who says the LHC will destroy the world is a twat. That's it. Anyway. Well, also, while we're here, because of course you did also pretend to work here

in the same way you pretend to work at Manchester University. And this is kind of one of the homes, to some extent, of your most cited paper, isn't it? Yeah, just before we get goingC without a Higgs boson. So it was a complete failure in that sense, but it's the thing that's been my most successful paper. So there you go. Failure is rewarded in physics. Anyway, today we are asking what is the Higgs boson and its role in the standard model of particle physics? Why was it so important to discover the Higgs or to prove

its non-existence? And now that we've discovered the Higgs boson, what next for the Large Hadron Collider? We are joined by a particle physicist, a particle physicist, someone who was nearly a solid-state physicist, and a theology student, because it's the god particle after all. And they are... I'm Katie Brand. I'd like to call myself a theology graduate, if you don't mind, because I did leave 20 years ago. But always we are a student of theology, right?

So I'm Katie Brand. I am a writer, sometimes a comedian, and an ignorant but willingly enthusiastic sort of amateur physicist. So that's why I'm here. And the question we were posed tonight was, what was it, what would we like? One project you would most like to gather an international team of scientists to solve. Yeah, well, I mean, this is my dream. It feels like real pie-in-the-sky stuff, right?

But I've been thinking about it all the way here, and I think if I could solve anything with an international team of scientists, it would be what happens when you smash particles together really fast in a massive underground tube. But I know that's a pipe dream, I know. So instead, I'd like them to solve how it is that I can fall asleep so easily on the sofa, but when I go straight to bed, I'm suddenly wide awake because it drives me insane. I feel like that's more realistic. If you guys could help me with that, that would be great. Forget the tube. Forget the tube. I'm slightly worried there's someone at the back worried for me going, Katie, you do understand

that we do have the tube here. You could visit it. Anyway, no, I had a great time with the tube. It was great. Hi, I'm Thabong Yu. I'm a lecturer in theoretical particle physics. And the thing that I would most like to solve with a team of international scientists is the mystery of why is the Higgs boson so lonely? I love that you actually anthropomorphize the Higgs like that. I'm Clara Nellis. I'm a particle physicist working on the ATLAS experiment with the University of Amsterdam. And I

would like an international team of scientists to study the mystery of the disappearing cups of tea. Because whenever I make myself a cup of tea, I go back to coding or watching TV, and then I look down and it's gone. And I hypothesize that there is an alternative

dimension where it's just made entirely of tea. And that's where my tea goes to. And I'd like to be able to hack into that dimension so that I could have infinite cups of tea. That's my, but if any grant listeners, grant reviewers are listening, I'd like to also discover dark matter. Thanks. My name is Ben Miller. I am an actor and a children's author. And I actually have approximately three quarters of a PhD

in solid state physics. The puzzle I would like a team of scientists to solve is I'd just like them to write up my PhD for me. And then give me a really easy viva I mean really really really easy but no I suppose uh the question I would like answer but particle physics is a mess isn't it let's be honest let's just get it let's just get it all

out in the open there's too many particles there's too many particles you guys have just not stopped for years and years. I just want to know, is this enough particles now, already, with the Higgs? Is this the last particle, or are there more of these particles? And if there are, what kind of particles are they? That's my...

It's not funny, but that is my question. And this is our panel. Thank you. funny but that is my question and this is our panel i enjoyed that uh big ben because in the sound check you said you'd get between a third and a half of a degree now you've gone up to three quarters i'm beginning to wonder if the fractions were the problem when you were it's asymptotic the number of times i mentioned my PhD, the closer I get to having actually finished it. Do you remember, for a joke once, I think it was on

Monkey Cage, it was a radio show we made and we got your supervisor in and we thought he was going to be really lovely and Ben hasn't seen his supervisor for a long time and he was actually quite annoyed because I think you did all the research and then stopped at the moment you started

writing your thesis didn't you see yes i was actually doing quite well i mean i don't know if there are any fans of cool on blockade um but yeah i was there right back in the early days um it's not my name and uh my my supervisor mike pepper was actually is is actually still absolutely furious with me that i didn't uh i didn't finish my phd very understandably really see i told you brian scientists get really angry when physicists waste their time going into showbiz anyway the um katie i just wanted to ask you first of all before we get into into kind of the full-on science of of you today was your first day of going down seeing the atlas experiment we went was it i think 83 meters underground and

i think that first experience of what what what was it for you well it is it is a sort of weird strangely spiritual experience going down there it's like a you know the sort of journey to the center of the earth moment and all the stuff leading up to it you know it's all quite fun and theatrical i mean i know obviously there's health and safety things but I just mean me as a kind of someone who comes from film and entertainment I'm just like great you have a wire door with no unauthorized entry and and Clara had to have her iris scanned this is amazing this is better than my wildest dreams so the whole lead up to it feels to me as a lay person amateur quite theatrical and it sort of preps you for it so you feel like you're going on a journey to the centre of the earth

where something magical is happening, where people are trying to solve the universe in a giant tube. And then you get down there and you do feel like you're sort of, well, I felt anyway, close to the magic. And I said to Ben, do you feel like you're actually vibrating differently yourself? And I just realised I was just a bit excited and slightly hungry. To actually be there thinking this is where you do it,

this is where you smash particles together to find out what's really going on in our universe. But I was very quiet afterwards. I felt quite subdued. It's more in your mind what's happening in there. It's not the lumps of metal, it's what they're doing. I really felt the sort of magic of that. Well, it's what they're doing. I really felt the sort of magic of that. Well that's what we're going to find out today. So we're going to find out, is it magic

or is it physics? For listeners that don't know so much about CERN and Large Hadron Collider and the detectors, could you give us a brief summary of what this machine is, what it does and how we detect the outcome of the particle collisions? Yeah, so we have the Large Hadron Collider, which is a 27 kilometer long particle accelerator, and it's 100 meters underground. And we accelerate using radio frequency cavities, protons, and sometimes heavy ions like lead, where we strip the electrons away, to very close to the speed of light, and then we smash them together inside essentially giant particle cameras, but they're very complicated detectors that we have developed over many decades in order to study the particles that come from the collision.

So when these collisions happen, we use Einstein's equation E equals mc squared, happen we use einstein's equation e equals mc squared where matter and energy are equivalent and we can change these particles into different types or they are changed into different types depending on the quantum mechanics and from these collisions they change into other types of particles which spread out in like a firework shape. And then we surround this collision point with the detector, which, depending on where we are in the layers of the onion of the detector, have a different purpose. So very close to the center, we're measuring the tracks of charged particles. And then we're measuring the energy of the particles. And then we're measuring muons. These incredibly tiny particles are going at such high energies that we need a lot of material in order to stop them or to measure

them. Timo, I wanted to ask you about why was it necessary? It's the 1960s, I think, when Peter Higgs and his colleagues kind of, they postulated this idea of the Higgs field. What was it about the universe? What was it about we understood about the universe that meant that the LHC was required? So if we go back to the 1960s, then the state of knowledge at the time was that everything was made up of matter and force particles. So we had the electron, we had the atoms that are made of nucleons and there was a puzzle of how to give them mass and the theory at the time that described things like the weak force just couldn't account for the fact that the particles had mass

and the theory itself then also gave you nonsense if you tried to calculate what happens when you smash things together at high energies so the Higgs mechanism and the Higgs boson that is a consequence of this mechanism was the thing that was necessary to make sense of this theory. When Clara was talking about those collisions, new particles are made, are they actually made, those new particles, or is it basically like smashing a clock and the bits come out, the bits that make it, or is it at the point of collision that that particle comes into existence so it's

at the point of collision that the particle comes into existence based on the energy that that was put in so you don't think of the proton as like a bag that contains the higgs boson and all the other particles but in the actual energy when you smash them together from E equals mc squared, as Clara said, the energy is converted into the mass of the particles that come out of, you could say, a quantum effect where you have all these quantum fluctuations from the energy and out of this quantum vacuum pops out these particles. So this is why we need the LHC with a high enough energy to then produce something like the Higgs boson. It might be worth just listing the known particles, because you mentioned the quarks, you mentioned the gluons,

you mentioned the electron. So could you give us the complete zoo, the family as we know them today? I think the standard model of particle physics is really quite simple. There's just two types of particles, matter and force particles. And the matter particles are the quarks and the electrons, and they come in three copies for reasons that no one knows. And the force particles are the familiar force of electromagnetism, which is carried by the photon. You have the strong force that holds the nucleus together. This is called the gluon that carries the strong force. And then

we know about radioactivity, which is why we need the weak force. And we call these W and Z bosons. And of course, gravity is the thing that's keeping you all in your seats. That's carried by the graviton. But that's basically it. I reckon for every

particle you've named, I can give you a role in show business. Try me with a particle, and I'll see if I can tell you what role in show business that particle would have. Bottom quark. A bottom quark. It's quite an easy start, that one, actually,

for any fans of Shakespeare. Quarks are fermions. Fermions are a nightmare. Can't share billing. Because of the Pauli exclusion principle. So quarks are basically

It turns out you weren't right. No, no, hang on, hang on. A quark would be a character actor. Quite distinctive. Kind of not the most important name on the marquee. Try me again. A neutrino. A neutrino is a special guest star.

You don't see them very often, but when they do turn up, create a big impact. Yeah. That makes more sense than the quark. Why do you think quarks are not important? I'm not saying they're not important. You did. Character actors are important.

I'm a character actor. Character actors are important, but they're not like show-offs like electrons, which basically, like electron, very like a lot of lead film actors, quite small, insignificant physically, get massive billing. Everything's about electrons.

Oh, we had this chemical interaction. Oh, I turned into an alkali. But yeah, they don't really justify it. They get all this attention and they're just nothing. Fermions get far too much attention. Bosons do all the work.

You've got your gluon that would basically be a supporting actor. They're there to really carry the story, hold everything together, make sure it all works, but they don't really get any glory. Sivan, you mentioned that the Higgs was a theoretical idea in the 1960s. And you said that that was to build a consistent theory. So what do you mean by that? So when we have a fundamental theory that's

supposed to describe everything in the universe, then we calculate what's supposed to happen, and it's supposed to give a definite answer. And if the theory doesn't give a definite answer, then it's just a approximate theory. It's a model. It works for the things that you're measuring, maybe at a certain energy scale that you could only access in the 1960s. But you know that nature does something when you collide particles at higher energies. So the Higgs mechanism is the thing that Peter Higgs, as well as lots of people came up with in the 60s, came up with this mechanism, was essentially solving this very mathematical problem. You couldn't just write down in your equations

a mass term. The other way to understand why the Higgs boson is necessary is to simply take the WW scattering and take the kind of paper that you wrote where you didn't have a Higgs boson in there and then simply

try to make it work by just adding things to it. Can I just ask a quick question? So the scattering is part of the experiment, and that's what happened? No. Yeah, you just take two W particles and smash them together. And as they scatter, that's what you're measuring. So that's what you call the W-W

scattering. And out of that, you find the Higgs boson that creates this drag. That's one way in which you could discover the Higgs, yes, by smashing together two W bosons. And then the Higgs comes out, and then it decays into some other particles, and you look for those other particles. And if you see enough of them,

and they reconstruct the energy of the Higgs, then you've discovered the Higgs boson. Clara, Tevong's a theorist and made that sound really simple. Yeah, I was thinking the same thing. You smash a few particles together, make a Higgs and then detect it. Could you elaborate? It's not easy. I mean, we had to wait until we had the energy of the LHC to be able to even create the Higgs bosons. But then the other big challenge is designing and building these detectors that can measure all of the particles that come from the collisions. We also have to decide which particles to select. We have to understand our detector in incredible detail because the way that each particle interacts with each section of the detector isn't so simple. It's not like we always know the correct answers.

And then also the Higgs boson particle that changes into most is the bottom quark. But because quarks don't like to be by themselves, they're very sociable. They hadronize, so they form pairs, and then they create these jets in our detector, which are just sprays of particles. And we have a lot of jets in our detector

because of all those quarks and gluons also in the proton. And so being able to distinguish these B quarks from other jets is very difficult. So the actual discovery of the Higgs boson was with events it was less likely to change into, but that were a much cleaner signal in our detector. So we had to collect enough data of this very rare process to be able to see that there was a new particle. It's a remarkable thing to think about, isn't it? You have 7,000 tons of detectors. You described it as this onion, a tremendously complex machine. And you're looking for two photons, two particles of light. That's all. It's remarkable. That's all. It's remarkable.

In our new podcast, Nature Answers, rural stories from a changing planet, we are travelling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts.

Idea. Just to reverse a bit, so there'll be people at home in the audience. There may be people asking why well yeah well no I'm yeah I'm not going to attempt to answer that but as a lay person trying to get to grips with this physics that's exactly what I was thinking Brian as well is that like you always want to have this feeling of like yeah this is really really interesting and it gets more and smaller and smaller and it gets more and more complex and but what's like the real world application like what's the impact on a person like me my motivation to do this research

my first most motivation is to understand the universe better and it might not have any direct impact on the day-to-day life right now so discovering the Higgs boson was a huge achievement. It's one of the greatest scientific achievements of the last 15 years. But right now, it has no impact on anybody's day-to-day life. But for me, it's what makes us human. The same reason that we make art, and that we listen to music, and that we love to dance, we want to know how our universe works. And for me, that's a good enough reason in and of itself. But the technology that we want to know how our universe works and for me that's a good enough reason in and of itself but the technology that we need to answer those questions is technology that doesn't exist yet and so the challenges of having to build a large hadron collider to build these detectors to measure these highly energetic but tiny particles is has to be invented and through

doing this process and also because of the ethos of CERN and the whole reason it was set up we just release all of our results and all of our technology to everybody and from that there's medical technology that's come from the research we do so PET scanners I mean now we have anti-matter machines that can look inside the human body and are able to see what's going on inside of there. And that's come from particle physics and physics research. And there's also hadron therapy, which is a new and better way to do cancer therapy. So the medical technology that comes from this research is really important. And there's also some really cool stuff

too, like being able to look behind paintings without damaging them. And that's not something we're specifically setting out to do at CERN when we do this research. But the technology that comes from it does impact a lot of everyday lives. I mean, televisions used to be particle accelerators before they got flat. And Ben, you write very widely about science. You write children's books about science. So how children's books about science. So how would you answer that question if someone was to say to you, well, why, what is the use of this, just acquiring knowledge?

What is the point? Well, it's about exploration, isn't it? We're an explorative species. We want to know what's at the boundary and beyond the boundary. We also have a spiritual dimension. We have a desire to know whether there's design in the universe. We have a desire to know whether there's design in the universe.

We have a desire to know what came before the universe. We so enjoy asking questions that we are prepared to pursue them to any length. I think that's one of the reasons we've been so successful as a species. I find it strange the other way around. You know, there's an announcement. We've discovered that the Higgs boson is... Guess what? Particles haven't got mass. They're getting the mass from this incredible field.

The field is communicated by a particle called the Higgs boson, and they go, yeah, not really turning me on. And you think, what is the matter with you? These are the fundamental questions that underpin it all. But that seems to me one of the great things that came out of CERN and the LHC. It was on mainstream television, on primetime news shows, there were

people explaining the Higgs field, explaining the Higgs boson. This should be the Trojan horse to get people more excited to know what they're made of and what everything they see around them is made of. I think the fact that the Higgs boson has become a household name really speaks volumes about the fact that the public

is interested in these big fundamental questions. There's sometimes a sense where it is a bit esoteric, that we're just discovering particles left and right, and that, oh, look, the W mass is a bit different than what we thought it was. And I think this is not really capturing what we're doing it for. It's not like we're playing Pokemon

and we've got to catch them all, you know. It's not because they... That would be fun. That would be really fun. Oh, yes, that's also part of the fun. But the Higgs boson, you know, wasn't just the last missing piece that we had to find because we wanted to collect them all, but because it is fundamentally different to anything we've ever seen before.

And it's something that is at the heart of many mysteries of things we still don't understand about the universe. So getting to higher energies, getting to measure things more precisely, looking not just at particles but at the cosmos and what's out there, is a way of getting closer to nature's fundamental truth what is the underlying elementary particles and the basic fundamental forces that governs everything you said something powerfully true there with the higgs boson is is like nothing we've ever seen before. Could you dig a little bit more deeply into what the Higgs mechanism is and how the Higgs mechanism entered the universe as far as we know? We've basically seen all the different types of things that nature can do. And we've seen the

matter particles, the force particles that are allowed. And the last thing in a sense that could also be allowed is the Higgs boson. And this was what was needed to give masses to all the other particles. So the way in which the Higgs does this is to break what's called electroweak symmetry. So this is a symmetry between the weak force and electromagnetism. To explain what a symmetry is, I would give the analogy of if you have two twins that are naked, you can't tell them apart. But if you put clothes on them, then now you can tell one of the twins from the other. So the weak force particles are like these twins, but there are three of them. So they're actually triplets. And these triplets, you can interchange them in your theory, and the theory

stays the same. You can't tell the difference. So the Higgs boson is the thing that dresses one of these and distinguishes them from the other two twins. And this other particle is dressed up and looks kind of fancy, so it goes off and marries another particle. What sort of things do they wear? Retro-punkpunk or what's the ideal kind of outfit for each one? So this Higgs boson dresses up one of the triplets and dresses that in a nice suit. This particle goes off and marries another force particle. Let's say they're wearing a nice Vivienne Westwood outfit,

something quite attractive, a bit sexy. And we give them a name. We call them the photon and the Z boson. They pair up, and that's what we call the electromagnetic force and the weak force, the Ws and the Zs. Ben mentioned the linked cosmology. So what do we know about the way the Higgs began to play that role as the universe unfolds from the Big Bang onwards?

Everywhere around us is the Higgs boson with an energy configuration that enables it to do its job, to give masses to the other particles. But as you go back to the Big Bang and as you go back to the early universe, when the temperature was higher, then the energy configuration of the Higgs boson was different. configuration of the Higgs boson was different. So you think of this energy configuration as being above the kind of energy configuration that it is in now, and we visualize this by, say, a Mexican hat, where right now it's sitting at the bottom of the Mexican hat, and in the early universe it had more energy, and it was sitting somewhere at the center of the Mexican hat, at the top of the hat.

So when it's sitting at the center, then it's switched off. It's not giving mass to any of the other particles. And as the temperature of the universe drops since the Big Bang, then at some point the energy configuration allows it to go to this value that it has nowadays and do its job. But we still don't know how that transition happened, and this is one of the reasons why we want to understand the Higgs better so we understand this cosmology. Claire, I just wanted to, because that's very,

there was a point there about five minutes ago where we had possibly the first time where subatomic particles were beginning to enter RuPaul's Drag Race. And I'm kind of intrigued because also talking about when you mentioned, for instance, you know, the Mexican hat, the physics, it seems to me, especially particle physics, it's always looking for good metaphors and for good similes. So how difficult is it to find the best translation, the best visual translation for something which is very hard to picture in itself did you have a favorite one so yeah my favorite one is a snow field

so the the higgs field is a field of snow throughout the whole universe and then the particles get their mass depending on how much they interact with that field and so if for example you imagine a skier who's got some very nice skis going across the top of the snow field, this is like a photon. It's just essentially not... Well, a photon, I would imagine, was on a paraglide,

not even interacting with the field at all. And then somebody on skis is like an electron. It's kind of touching it a little bit, but not interacting too much. And then my favorite particle is the top quark so a top quark is like in in snow boots so they've taken the skis off and they're just trudging through the snow and then the Higgs boson itself is an excitation of the Higgs field so the Higgs boson is a snowball and so once you've discovered the snowball you know

that there must be this field of snow somewhere that the snowball came from is there a department here at CERN that comes up with the metaphors is there the metaphor department because like Ben and I could maybe sort of with a bit of practice just man that for you like you could come and explain it to us and we'll sort of mostly understand it and then we'll come up with just a list of metaphors that you can use we can have a little booth yeah somewhere near you know somewhere near reception you've got that little kiosk as you go in uh that sells the hats which i think is a bit mercantile frankly yes sells the hard hats with cern written on you know i did get a cern have a care people um yeah we

can have a little booth there and and you basically you know you can just sketch an outfit and i'll tell you which type of actor that particle is i think we'll um we'll get there very quickly i do want to ask though uh in all seriousness uh you know my question at the beginning you know about other particles and um you know we've talked about where we've got to so far and we found the higgs and we know what it's it's uh it's masses but you know, what other things might there be out there? What other particles might there be to discover? Presumably they'd be heavier than the Higgs, is that right? They'd be either heavier or too weakly coupled for us to have detected so far, so they could just be very, very shy.

But they could also be much heavier than what we expected. You know, the reason why I said that the Higgs boson is lonely is because we expected it to have friends. In many of the theories that we thought would have solved the mysteries associated with the Higgs and other aspects of the Sander model, all of these theories predicted that we'd discover not just the Higgs boson, but maybe a second Higgs boson. Maybe we'd discover other matter particles. Maybe other forces would have shown up.

So there was a lot of excitement when we found the Higgs as expected, followed by a lot of disappointment and puzzling and, you know, self-doubt and questioning whether or not we even had the right principles and the right theories to begin with. So we still haven't seen these particles and this is making the situation actually very interesting and in some ways more exciting because it means that we may be missing theoretically some new idea, something radically different to what we expected or anticipated. I was wondering is there anything you're sort of scared to discover that would make you nervous or that you think, oh, I think that might exist mathematically? One of the biggest mysteries in the universe is what is dark matter?

This has been measured and observed cosmologically, but we don't know. What is it, by the way? So dark matter is, it's been observed by galaxies rotating too fast. So through many different observations, we've seen that there's something very massive in our universe everything that we understand the standard model that we've been talking about it only makes up five percent of our universe and so we don't we don't know what dark matter is the only thing that we know it has is gravitational effect right um but we're also and it's one of the reasons that sometimes people say you've discovered the h Higgs, great, are you done now? Is it time to turn the LHC off?

And it's not, because first of all, we want to understand as much about the Higgs as possible. But also, because we know that dark matter has a gravitational effect, it could be that it gets its mass if it's a particle, and it might not be, that it might get its mass from the Higgs mechanism the same way that other particles do. And in that case, by studying the Higgs boson as precisely as possible, we're looking for differences between the standard model predictions and what we actually measure in our experiments. And then that could show that something else

was happening with the Higgs field that can't be accounted for with the quarks and the other particles that we've measured. So it's a really great way that we can use it as a link between the Higgs boson and potentially being able to understand dark matter. Oh, I just wanted to say that we also see dark matter in the early universe. So it can't be planets because we see the effects of dark matter in the light from the Big Bang, the cosmic microwave background. So we know already from that that there was some kind of dark matter particle.

And it's not as exotic as it sounds. We already know of a particle that doesn't interact with the light that exists everywhere in the universe. Even here and right now? Even right now, going through us. So the Large Hadron Collider is full of it? Everywhere. You're full of it. I'm full of it. That's fatty talk, right?

So there's a billion of these particles going through your eyeball every second, right? Just to clarify, because we're coming towards the end, Tivong is talking about neutrinos, which are particles that interact only via the weak force. And I thought, he said this remarkable thing, that billions of them are passing through your head now. But only you.

Is that why I'm here? So one of the ideas, to bring it back to dark matter, one of the ideas is that perhaps dark matter is a particle that interacts via the weak force, but then you'd need an awful lot of them passing through your detectors to have a very slim chance of seeing them. And we have experiments that try to do that. Or it would be very unlikely you would make a dark matter particle

in a collision at the Large Hadron Collider, but we might. Yeah, so we're often looking for things that are missing in our measurement. So we don't just measure the particles that come out and only measure those. We also look for, for example, missing momentum. So we have conservation of momentum in our detector, and so we can tell when stuff is missing. And neutrinos are very, very light. So if we got stuff missing that was very heavy then that would be an indication for example that there could be dark matter in the measurements and we're also doing some new techniques because we've always assumed that the collisions happen and

these particles are so short-lived that whatever they change into happens right at the heart of the detector and so we've trained all of our algorithms to select for the data to look for stuff happening in the center but it could be that dark matter or some other new physics travels a bit of a distance through the detector before it then changes into something we could measure and we call these long lived particles and so it could be that they're interacting at the edge and so we have to redesign all of our algorithms to look for things that are happening there yeah it's great isn't it so they could be there yeah in the data yeah they could already be there and we've just not been looking for them in that sense so that's one of the the other ways

that we're trying to innovate and think well how else could it show up in our detector this idea of the universe having mass it was the first time that I'd ever thought of when I started reading about the research that was going on. Could you have a universe without mass? You could have all kinds of universes, it just wouldn't be one in which we could survive or live. If the Higgs, in fact, its energy configuration

right now in our universe, in the standard model of particle physics, as best as we've measured the parameters of this theory, is telling us that the energy configuration is not stable. So it could change to another energy configuration and

induce a catastrophic vacuum decay death of the universe that would just wipe out the entire universe. I would like to very clearly state here that the Large Hadron Collider would have nothing to do with this. No, we will be cutting out your bit at the end.

We're keeping, if I was Dan Brown, I'd keep that answer there. Wait a minute, wait a minute. You're saying that we've built this collider to find the Higgs, which holds everything in the universe together, and you've

discovered it's unstable. That's what you're telling me. Within the standard model of particle physics yes, which is why we really hope that there's something beyond it. Also, it's only very slightly unstable. You need to get building the next one now.

You need to get on it. This is what we call a cliffhanger. That's just one reason. Why are you sitting here doing a radio show? You need to be getting off backstage. Get your toolbox out. Start making the next one. Well, just to reassure you, if it is indeed unstable, it was unstable

whether we detected it or not. It's got nothing to do with us. It's got nothing to do with us. I didn't know then. Now you've told me. That's just really inconsiderate. You're advocating for ostrich-like behaviour. Why does it matter? You're saying that if you don't know

it's fine. Let's just enjoy these last few minutes we've all got together and see what we ask the audience. It's a nice moment, Ben, after the audition where you still don't know if you've got the part or not and for a while you'd rather not know, it's like that, isn't it? That's probably what you'd expect. How are you just sort of, yeah, well, if we knew the universe was unstable,

then it would have all gone to pieces by now. How are you so relaxed? How are you so relaxed about this situation? Is not everyone else really stressed by this? I'll tell you why, because he finished his degree and he's worked out a get-out clause. stressed by this. I'll tell you why, because he finished his degree and he's worked out a get-out clause.

Just to finish, this is pointing towards the future. It's a signal that there's something deep that we don't understand. Right, so some theorists like myself and many of my colleagues do try to explain this by saying it wasn't an accident. Maybe some dynamics in the early universe actually balanced the higgs boson right at the edge of this precipice

and this is something that we're actively trying to look for other signals for is this supposed to be reassuring we're on a precipice at least we're still on the precipice look at the bright side yeah anyway we've been a bit we've run out of time so we're going to just uh we asked our audience question as well as we always do and we wanted to know what is the secret of the universe you would most like to uncover and why brian what have you got you know we asked you before how many of you are physicists um and you said about most of you are physicists right usually when we ask this question the the aim is to generate humorous answers. In this case, they're all very specific and precise. There actually are

answers to the question as posed. So, for example, where does it stop? So the joke is, what is the secret of the universe you'd most like to uncover and why? Where does it end? Do jazz hands. I'll do jazz hands for my one dark matter so there we go yeah that didn't still didn't quite get it

working did it is is space time just a side effect of all a selection of quantum fields trying to achieve their respective lowest possible energy states. Right. I think you... Yes, yes it is. Yeah, I've got that one. Yes, it is. Right. I wasn't open with it.

Right. This one, right. Now I'm going to do it... Right. Okay, so... All right, ladies and gentlemen. Oh, no, gentlemen. Now.

Oh, so. What is the secret of the universe you'd most like to uncover and why? I'll tell you my one. My one is, what's the rest difference between rest and virtual particles? I gave it everything my one. My one is, what's the rest difference between rest and virtual particles? I gave it everything, mate.

I gave it absolutely everything there. This is from one of the few non-physicists here. Where do all the socks end up? So that's a... Yeah, the one that I particularly like here is, why in the UK are bathroom hot and cold taps separate? Oh, man.

If that was the biggest issue the UK were dealing with now, what joy that would be. And then finally, of course, how come, and this is a science question, how come Brian Cox doesn't age? Because I do all his ages for him, right? I'm one year younger than him.

When we started working together. In fact, if you might have seen, there was a visual beforehand where I had lovely dark hair and it was all over my head. Not since I've worked with him. I was going to say, I do age at the normal rate. It's just the contrast. I was wondering if one of you just moves much faster through space-time than the other.

Well, that's all we've got time for. Thank you to our panel, Dr Clara Nellist, Dr Tevong Yu, not doctor or professor, but he should have been if he'd completed his PhD, Ben Miller, and not Archbishop or Dean, but she's glad that I believe

she's not an Archbishop or Dean, Katie Brand. That's a fitting end to our series. We've learned that we are on a precipice. We began with Egyptian mummification and we've ended up with elementary particles. Now, of course, what Brian didn't actually know about today's episode

is that this was actually a honey trap to get him back to Geneva under the instructions of CERN's governing board because apparently 12 years ago he was in the instructions of CERN's governing board, because apparently, 12 years ago, he was in the middle of the meeting and just suddenly went, hang on a minute, I've just got to pop out, I've just got to get into a helicopter for a while and talk about superluminous supernova for the BBC, but I'll be back in a minute, and he never returned,

thus breaking his contract. So now he is here, he's not allowed to leave CERN for two and a half years until his contractual obligation is met so I'm going off on holiday for a few weeks you have work to do to make sure we don't fall down that precipice bye bye

bye bye thank you In the infinite monkey cage In the infinite monkey cage Without your trousers In the infinite monkey cage Turned out nice again. Hello, my name's Greg Jenner. I am the host of You're Dead to Me,

the Radio 4 comedy show that takes history seriously and then laughs at it. And I just wanted to say that if you like laughing, if you like learning, if you like history, or if you hated history at school, well, we are the show for you. Yes, every episode I pair up a top historian with a fantastic comedian,

and we have a lovely, funny, fascinating chat about a different subject from world history. We do stuff you did at school and we do stuff you've never even heard of. So if that sounds like fun, you can check out our back catalogue

and our new series on BBC Sounds. Just type in You're Dead to Me and hit subscribe. Thank you. Bye. In our new podcast, Nature Answers, rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change.

We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts.