Transcript
00:00:00 The following is a conversation with Harry Cliff,
00:00:03 a particle physicist at the University of Cambridge,
00:00:05 working on the Large Hadron Collider beauty experiment
00:00:09 that specializes in investigating the slight differences
00:00:13 between matter and antimatter
00:00:15 by studying a type of particle called the beauty quark
00:00:18 or b quark.
00:00:19 In this way, he’s part of the group of physicists
00:00:22 who are searching for the evidence of new particles
00:00:25 that can answer some of the biggest questions
00:00:26 in modern physics.
00:00:28 He’s also an exceptional communicator of science
00:00:31 with some of the clearest and most captivating explanations
00:00:34 of basic concepts in particle physicists
00:00:37 that I’ve ever heard.
00:00:39 So when I visited London, I knew I had to talk to him.
00:00:42 And we did this conversation
00:00:44 at the Royal Institute Lecture Theatre,
00:00:47 which has hosted lectures for over two centuries
00:00:50 from some of the greatest scientists
00:00:52 and science communicators in history,
00:00:54 from Michael Faraday to Carl Sagan.
00:00:57 This conversation was recorded
00:00:59 before the outbreak of the pandemic.
00:01:01 For everyone feeling the medical and psychological
00:01:03 and financial burden of this crisis,
00:01:05 I’m sending love your way.
00:01:07 Stay strong.
00:01:08 We’re in this together.
00:01:09 We’ll beat this thing.
00:01:11 This is the Artificial Intelligence Podcast.
00:01:13 If you enjoy it, subscribe on YouTube,
00:01:15 review it with five stars on Apple Podcast,
00:01:18 support it on Patreon,
00:01:19 or simply connect with me on Twitter
00:01:21 at Lex Friedman, spelled F R I D M A N.
00:01:25 As usual, I’ll do a few minutes of ads now
00:01:27 and never any ads in the middle
00:01:28 that can break the flow of the conversation.
00:01:30 I hope that works for you
00:01:31 and doesn’t hurt the listening experience.
00:01:35 Quick summary of the ads.
00:01:36 Two sponsors, ExpressVPN and Cash App.
00:01:40 Please consider supporting the podcast
00:01:41 by getting ExpressVPN at expressvpn.com slash lexpod
00:01:46 and downloading Cash App and using code lexpodcast.
00:01:50 This show is presented by Cash App,
00:01:52 the number one finance app in the App Store.
00:01:55 When you get it, use code lexpodcast.
00:01:58 Cash App lets you send money to friends, buy Bitcoin,
00:02:01 and invest in the stock market with as little as $1.
00:02:04 Since Cash App does fractional share trading,
00:02:06 let me mention that the order execution algorithm
00:02:09 that works behind the scenes
00:02:11 to create the abstraction of the fractional orders
00:02:13 is an algorithmic marvel.
00:02:15 So big props to the Cash App engineers
00:02:17 for solving a hard problem that in the end
00:02:20 provides an easy interface that takes a step up
00:02:22 to the next layer of abstraction over the stock market,
00:02:25 making trading more accessible for new investors
00:02:28 and diversification much easier.
00:02:31 So again, you get Cash App from the App Store or Google Play
00:02:34 and use the code lexpodcast, you get $10
00:02:38 and Cash App will also donate $10 to First,
00:02:41 an organization that is helping advance robotics
00:02:43 and STEM education for young people around the world.
00:02:47 This show is sponsored by ExpressVPN.
00:02:50 Get it at expressvpn.com slash lexpod
00:02:54 to get a discount and to support this podcast.
00:02:57 I’ve been using ExpressVPN for many years, I love it.
00:03:01 It’s easy to use, press the big power on button
00:03:04 and your privacy is protected.
00:03:05 And if you like, you can make it look
00:03:08 like your location is anywhere else in the world.
00:03:11 I might be in Boston now, but I can make it look
00:03:13 like I’m in New York, London, Paris, or anywhere else.
00:03:17 This has a large number of obvious benefits.
00:03:20 Certainly, it allows you to access international versions
00:03:23 of streaming websites like the Japanese Netflix
00:03:26 or the UK Hulu.
00:03:28 ExpressVPN works on any device you can imagine.
00:03:31 I use it on Linux, shout out to Ubuntu, Windows, Android,
00:03:35 but it’s available everywhere else too.
00:03:38 Once again, get it at expressvpn.com slash lexpod
00:03:43 to get a discount and to support this podcast.
00:03:46 And now, here’s my conversation with Harry Kliff.
00:03:51 Let’s start with probably one of the coolest things
00:03:54 that human beings have ever created,
00:03:56 the Large Hadron Collider, OHC.
00:04:00 What is it?
00:04:00 How does it work?
00:04:02 Okay, so it’s essentially this gigantic
00:04:05 27 kilometer circumference particle accelerator.
00:04:08 It’s this big ring.
00:04:09 It’s buried about 100 meters underneath the surface
00:04:12 in the countryside just outside Geneva in Switzerland.
00:04:14 And really what it’s for, ultimately,
00:04:17 is to try to understand what are the basic building blocks
00:04:20 of the universe.
00:04:21 So you can think of it in a way
00:04:23 as like a gigantic microscope,
00:04:24 and the analogy is actually fairly precise, so.
00:04:28 Gigantic microscope.
00:04:30 Effectively, except it’s a microscope
00:04:32 that looks at the structure of the vacuum.
00:04:36 In order for this kind of thing to study particles,
00:04:40 which are the microscopic entities, it has to be huge.
00:04:44 It’s a gigantic microscope.
00:04:45 So what do you mean by studying vacuum?
00:04:48 Okay, so I mean, so particle physics as a field
00:04:51 is kind of badly named in a way,
00:04:53 because particles are not the fundamental ingredients
00:04:56 of the universe.
00:04:57 They’re not fundamental at all.
00:04:58 So the things that we believe
00:05:00 are the real building blocks of the universe
00:05:02 are objects, invisible fluid like objects
00:05:05 called quantum fields.
00:05:07 So these are fields like the magnetic field
00:05:10 around a magnet that exists everywhere in space.
00:05:12 They’re always there.
00:05:13 In fact, actually, it’s funny that we’re
00:05:15 in the Royal Institution,
00:05:15 because this is where the idea of the field
00:05:19 was effectively invented by Michael Faraday
00:05:21 doing experiments with magnets and coils of wire.
00:05:23 So he noticed that, you know,
00:05:26 it was a very famous experiment that he did
00:05:28 where he got a magnet and put on top of it a piece of paper
00:05:31 and then sprinkled iron filings.
00:05:32 And he found the iron filings arranged themselves
00:05:34 into these kind of loops,
00:05:37 which was actually mapping out the invisible influence
00:05:40 of this magnetic field, which is a thing, you know,
00:05:42 we’ve all experienced, we’ve all felt, held a magnet
00:05:44 or two poles of magnet and pushed them together
00:05:46 and felt this thing, this force pushing back.
00:05:48 So these are real physical objects.
00:05:51 And the way we think of particles in modern physics
00:05:53 is that they are essentially little vibrations,
00:05:56 little ripples in these otherwise invisible fields
00:06:00 that are everywhere.
00:06:01 They fill the whole universe.
00:06:03 You know, I don’t, I apologize perhaps
00:06:05 for the ridiculous question.
00:06:07 Are you comfortable with the idea
00:06:10 of the fundamental nature of our reality being fields?
00:06:14 Because to me, particles, you know,
00:06:17 a bunch of different building blocks makes more sense
00:06:20 sort of intellectually, sort of visually,
00:06:22 like it seems to, I seem to be able to visualize
00:06:26 that kind of idea easier.
00:06:28 Are you comfortable psychologically with the idea
00:06:31 that the basic building block is not a block, but a field?
00:06:35 I think it’s, I think it’s quite a magical idea.
00:06:38 I find it quite appealing.
00:06:39 And it’s, well, it comes from a misunderstanding
00:06:42 of what particles are.
00:06:43 So like when you, when we do science at school
00:06:45 and we draw a picture of an atom,
00:06:46 you draw like, you know, a nucleus with some protons
00:06:49 and neutrons, these little spheres in the middle,
00:06:50 and then you have some electrons that are like little flies
00:06:53 flying around the atom.
00:06:54 And that is a completely misleading picture
00:06:56 of what an atom is like.
00:06:57 It’s nothing like that.
00:06:58 The electron is not like a little planet orbiting the atom.
00:07:01 It’s this spread out, wibbly wobbly wave like thing.
00:07:05 And we know we’ve known that since, you know,
00:07:07 the early 20th century, thanks to quantum mechanics.
00:07:10 So when we, we, we carry on using this word particle
00:07:13 because sometimes when we do experiments,
00:07:15 particles do behave like they’re little marbles
00:07:17 or little bullets, you know.
00:07:19 So in the LHC, when we collide particles together,
00:07:22 you’ll get, you know, you’ll get like hundreds of particles
00:07:25 all flying out through the detector
00:07:26 and they all take a trajectory and you can see
00:07:28 from the detector where they’ve gone
00:07:29 and they look like they’re little bullets.
00:07:31 So they behave that way, you know, a lot of the time.
00:07:35 When you really study them carefully,
00:07:37 you’ll see that they are not little spheres.
00:07:40 They are these ethereal disturbances
00:07:43 in these underlying fields.
00:07:44 So this is really how we think nature is,
00:07:48 which is surprising, but also I think kind of magic.
00:07:51 So, you know, we are, our bodies are basically made up
00:07:54 of like little knots of energy
00:07:56 in these invisible objects that are all around us.
00:08:00 And what is the story of the vacuum when it comes to LHC?
00:08:07 So why did you mention the word vacuum?
00:08:09 Okay, so if we just, if we go back to like the physics,
00:08:13 we do know.
00:08:13 So atoms are made of electrons,
00:08:16 which were discovered a hundred or so years ago.
00:08:18 And then in the nucleus of the atom,
00:08:20 you have two other types of particles.
00:08:21 There’s an up, something called an up quark
00:08:23 and a down quark.
00:08:24 And those three particles make up every atom in the universe.
00:08:27 So we think of these as ripples in fields.
00:08:30 So there is something called the electron field
00:08:34 and every electron in the universe is a ripple moving
00:08:37 about in this electron field.
00:08:39 So the electron field is all around us, we can’t see it,
00:08:40 but every electron in our body is a little ripple
00:08:42 in this thing that’s there all the time.
00:08:45 And the quark fields are the same.
00:08:46 So there’s an up quark field and an up quark
00:08:48 is a little ripple in the up quark field.
00:08:50 And the down quark is a little ripple
00:08:51 in something else called the down quark field.
00:08:53 So these fields are always there.
00:08:55 Now there are potentially, we know about a certain number
00:08:58 of fields in what we call the standard model
00:09:00 of particle physics.
00:09:01 And the most recent one we discovered was the Higgs field.
00:09:04 And the way we discovered the Higgs field
00:09:07 was to make a little ripple in it.
00:09:08 So what the LHC did, it fired two protons into each other,
00:09:12 very, very hard with enough energy
00:09:14 that you could create a disturbance in this Higgs field.
00:09:18 And that’s what shows up as what we call the Higgs boson.
00:09:20 So this particle that everyone was going on about
00:09:22 eight or so years ago is proof really,
00:09:25 the particle in itself is, I mean, it’s interesting,
00:09:28 but the thing that’s really interesting is the field.
00:09:30 Because it’s the Higgs field that we believe
00:09:33 is the reason that electrons and quarks have mass.
00:09:38 And it’s that invisible field that’s always there
00:09:41 that gives mass to the particles.
00:09:42 The Higgs boson is just our way
00:09:44 of checking it’s there basically.
00:09:46 And so the Large Hadron Collider,
00:09:49 in order to get that ripple in the Higgs field,
00:09:51 it requires a huge amount of energy.
00:09:54 Yeah, I suppose.
00:09:55 And so that’s why you need this huge,
00:09:57 that’s why size matters here.
00:09:58 So maybe there’s a million questions here,
00:10:01 but let’s backtrack.
00:10:02 Why does size matter in the context of a particle collider?
00:10:09 So why does bigger allow you for higher energy collisions?
00:10:15 Right, so the reason, well, it’s kind of simple really,
00:10:18 which is that there are two types of particle accelerator
00:10:21 that you can build.
00:10:21 One is circular, which is like the LHC,
00:10:23 the other is a great long line.
00:10:25 So the advantage of a circular machine
00:10:28 is that you can send particles around a ring
00:10:30 and you can give them a kick every time they go around.
00:10:32 So imagine you have a, there’s actually a bit of the LHC,
00:10:34 that’s about only 30 meters long,
00:10:36 where you have a bunch of metal boxes,
00:10:38 which have oscillating 2 million volt electric fields
00:10:41 inside them, which are timed so that when a proton
00:10:44 goes through one of these boxes,
00:10:45 the field it sees as it approaches is attractive.
00:10:48 And then as it leaves the box,
00:10:49 it flips and becomes repulsive
00:10:51 and the proton gets attracted
00:10:52 and kicked out the other side, so it gets a bit faster.
00:10:55 So you send it, and then you send it back round again.
00:10:57 And it’s incredible, like the timing of that,
00:10:59 the synchronization, wait, really?
00:11:01 Yeah, yeah, yeah, yeah.
00:11:02 I think there’s going to be a multiplicative effect
00:11:05 on the questions I have.
00:11:06 Is, okay, let me just take that attention for a second.
00:11:12 The orchestration of that, is that fundamentally
00:11:15 a hardware problem or a software problem?
00:11:17 Like what, how do you get that?
00:11:20 I mean, I should first of all say, I’m not an engineer.
00:11:22 So the guys, I did not build the LHC,
00:11:24 so they’re people much, much better at this stuff than I.
00:11:26 For sure, but maybe.
00:11:30 But from your sort of intuition,
00:11:33 from the echoes of what you understand,
00:11:37 what you heard of how it’s designed, what’s your sense?
00:11:40 What’s the engineering aspects of it?
00:11:43 The acceleration bit is not challenging.
00:11:45 Okay, I mean, okay, there’s always challenges
00:11:47 with everything, but basically you have these,
00:11:50 the beams that go around the LHC, the beams of particles
00:11:53 are divided into little bunches.
00:11:55 So they’re called, they’re a bit like swarms of bees,
00:11:57 if you like, and there are around,
00:12:00 I think it’s something of the order 2000 bunches
00:12:04 spaced around the ring.
00:12:05 And they, if you’re at a given point on the ring,
00:12:07 counting bunches, you get 40 million bunches
00:12:10 passing you every second.
00:12:11 So they come in like cars going past
00:12:14 on a very fast motorway.
00:12:16 So you need to have, if you’re an electric field
00:12:18 that you’re using to accelerate the particles,
00:12:20 that needs to be timed so that as a bunch of protons arrives,
00:12:23 it’s got the right sign to attract them
00:12:26 and then flips at the right moment.
00:12:27 But I think the voltage in those boxes
00:12:29 oscillates at hundreds of megahertz.
00:12:31 So the beams are like 40 megahertz,
00:12:33 but it’s oscillating much more quickly than the beam.
00:12:35 So I think it’s difficult engineering,
00:12:37 but in principle, it’s not a really serious challenge.
00:12:41 The bigger problem.
00:12:42 There’s probably engineers like screaming at you right now.
00:12:44 Probably, but I mean, okay.
00:12:46 So in terms of coming back to this thing,
00:12:47 why is it so big?
00:12:48 Well, the reason is you wanna get the particles
00:12:51 through that accelerating element over and over again.
00:12:54 So you wanna bring them back round.
00:12:55 So that’s why it’s round.
00:12:56 The question is why couldn’t you make it smaller?
00:12:58 Well, the basic answer is that these particles
00:13:01 are going unbelievably quickly.
00:13:03 So they travel at 99.9999991% of the speed of light
00:13:09 in the LHC.
00:13:11 And if you think about, say,
00:13:12 driving your car around a corner at high speed,
00:13:16 if you go fast, you need a lot of friction in the tires
00:13:19 to make sure you don’t slide off the road.
00:13:21 So the limiting factor is how powerful a magnet can you make
00:13:26 because what we do is magnets are used
00:13:28 to bend the particles around the ring.
00:13:30 And essentially the LHC, when it was designed,
00:13:33 was designed with the most powerful magnets
00:13:35 that could conceivably be built at the time.
00:13:37 And so that’s your kind of limiting factor.
00:13:40 So if you wanted to make the machine smaller,
00:13:41 that means a tighter bend,
00:13:42 you need to have a more powerful magnet.
00:13:44 So it’s this toss up between how strong are your magnets
00:13:48 versus how big a tunnel can you afford.
00:13:49 The bigger the tunnel, the weaker the magnets can be.
00:13:51 The smaller the tunnel, the stronger they’ve gotta be.
00:13:54 Okay, so maybe can we backtrack to the Standard Model
00:13:57 and say what kind of particles there are, period,
00:14:00 and maybe the history of kind of assembling
00:14:04 that the Standard Model of physics
00:14:06 and then how that leads up to the hopes and dreams
00:14:10 and the accomplishments of the Large Hadron Collider.
00:14:12 Yeah, sure, okay.
00:14:14 So all of 20th century physics in like five minutes.
00:14:16 Yeah, please.
00:14:17 Okay, so, okay, the story really begins properly.
00:14:21 End of the 19th century, the basic view of matter
00:14:24 is that matter is made of atoms
00:14:26 and the atoms are indestructible, immutable little spheres
00:14:30 like the things we were talking about
00:14:31 that don’t really exist.
00:14:32 And there’s one atom for every chemical element.
00:14:35 So there’s an atom for hydrogen, for helium,
00:14:36 for carbon, for iron, et cetera, and they’re all different.
00:14:39 Then in 1897, experiments done
00:14:41 at the Cavendish Laboratory in Cambridge,
00:14:43 which is where I’m still, where I’m based,
00:14:45 showed that there are actually smaller particles
00:14:48 inside the atom, which eventually became known as electrons.
00:14:51 So these are these negatively charged things
00:14:53 that go around the outside.
00:14:54 A few years later, Ernest Rutherford,
00:14:57 very famous nuclear physicist,
00:14:58 one of the pioneers of nuclear physics
00:15:00 shows that the atom has a tiny nugget in the center,
00:15:03 which we call the nucleus,
00:15:04 which is a positively charged object.
00:15:05 So then by like 1910, 11, we have this model of the atom
00:15:09 that we learn in school,
00:15:09 which is you’ve got a nucleus, electrons go around it.
00:15:13 Fast forward a few years, the nucleus,
00:15:16 people start doing experiments with radioactivity
00:15:18 where they use alpha particles
00:15:20 that are spat out of radioactive elements as bullets,
00:15:24 and they fire them at other atoms.
00:15:26 And by banging things into each other,
00:15:28 they see that they can knock bits out of the nucleus.
00:15:31 So these things come out called protons, first of all,
00:15:33 which are positively charged particles
00:15:36 about 2000 times heavier than the electron.
00:15:38 And then 10 years later, more or less,
00:15:41 a neutral particle is discovered called the neutron.
00:15:43 So those are the three basic building blocks of atoms.
00:15:47 You have protons and neutrons in the nucleus
00:15:49 that are stuck together by something called the strong force,
00:15:51 the strong nuclear force,
00:15:53 and you have electrons in orbit around that,
00:15:55 held in by the electromagnetic force,
00:15:57 which is one of the forces of nature.
00:16:00 That’s sort of where we get to by like 1932, more or less.
00:16:04 Then what happens is physics is nice and neat.
00:16:07 In 1932, everything looks great, got three particles
00:16:09 and all the atoms are made of, that’s fine.
00:16:11 But then cloud chamber experiments.
00:16:13 These are devices that can be used to,
00:16:16 the first device is capable of imaging subatomic particles
00:16:18 so you can see their tracks.
00:16:19 And they’re used to study cosmic rays,
00:16:21 particles that come from outer space
00:16:23 and bang into the atmosphere.
00:16:25 And in these experiments,
00:16:28 people start to see a whole load of new particles.
00:16:29 So they discover for one thing antimatter,
00:16:31 which is the sort of a mirror image of the particles.
00:16:34 So we discovered that there’s also,
00:16:35 as well as a negatively charged electron,
00:16:37 there’s something called a positron,
00:16:38 which is a positively charged version of the electron.
00:16:40 And there’s an antiproton, which is negatively charged.
00:16:43 And then a whole load of other weird particles
00:16:45 start to get discovered.
00:16:46 And no one really knows what they are.
00:16:48 This is known as the zoo of particles.
00:16:50 Are these discoveries from the first theoretical discoveries
00:16:55 or are they discoveries in an experiment?
00:16:58 So like, yeah, what’s the process of discovery
00:17:01 for these early sets of particles?
00:17:03 It’s a mixture.
00:17:04 The early stuff around the atom is really
00:17:06 experimentally driven.
00:17:07 It’s not based on some theory.
00:17:09 It’s exploration in the lab using equipment.
00:17:11 So it’s really people just figuring out,
00:17:12 getting hands on with the phenomena,
00:17:14 figuring out what these things are.
00:17:16 And the theory comes a bit later.
00:17:17 That’s not always the case.
00:17:18 So in the discovery of the anti electron, the positron,
00:17:22 that was predicted from quantum mechanics and relativity
00:17:26 by a very clever theoretical physicist called Paul Dirac,
00:17:30 who was probably the second brightest physicist
00:17:33 of the 20th century, apart from Einstein,
00:17:34 but isn’t anywhere near as well known.
00:17:36 So he predicted the existence of the anti electron
00:17:39 from basically a combination of the theories
00:17:41 of quantum mechanics and relativity.
00:17:43 And it was discovered about a year after
00:17:44 he made the prediction.
00:17:46 What happens when an electron meets a positron?
00:17:49 They annihilate each other.
00:17:50 So when you bring a particle and its antiparticle together,
00:17:54 they react, well, they don’t react,
00:17:56 they just wipe each other out and they turn,
00:17:58 their mass is turned into energy,
00:18:00 usually in the form of photons, so you get light produced.
00:18:03 So when you have that kind of situation,
00:18:06 why does the universe exist at all
00:18:08 if there’s matter in any matter?
00:18:10 Oh God, now we’re getting into the really big questions.
00:18:12 So, do you wanna go there now?
00:18:15 Let’s, maybe let’s go there later.
00:18:19 Cause that, I mean, that is a very big question.
00:18:20 Yeah, let’s take it slow with the standard model.
00:18:23 So, okay, so there’s matter and antimatter in the 30s.
00:18:28 So what else?
00:18:29 So matter and antimatter,
00:18:30 and then a load of new particles start turning up
00:18:33 in these cosmic ray experiments, first of all.
00:18:36 And they don’t seem to be particles that make up atoms.
00:18:40 They’re something else.
00:18:41 They all mostly interact with a strong nuclear force.
00:18:44 So they’re a bit like protons and neutrons.
00:18:46 And by, in the 1960s in America, particularly,
00:18:50 but also in Europe and Russia,
00:18:52 scientists started to build particle accelerators.
00:18:54 So these are the forerunners of the LHC.
00:18:55 So big ring shaped machines that were, you know,
00:18:58 hundreds of meters long, which in those days was enormous.
00:19:00 You never, you know, most physics up until that point
00:19:02 had been done in labs, in universities, you know,
00:19:04 with small bits of kit.
00:19:06 So this is a big change.
00:19:07 And when these accelerators are built,
00:19:08 they start to find they can produce
00:19:10 even more of these particles.
00:19:12 So I don’t know the exact numbers, but by around 1960,
00:19:16 there are of order a hundred of these things
00:19:19 that have been discovered.
00:19:20 And physicists are kind of tearing their hair out
00:19:22 because physics is all about simplification.
00:19:25 And suddenly what was simple has become messy
00:19:28 and complicated and everyone sort of wants
00:19:29 to understand what’s going on.
00:19:31 As a quick kind of aside and probably really dumb question,
00:19:34 but how is it possible to take something like a,
00:19:38 like a photon or electron and be able to control it enough,
00:19:44 like to be able to do a controlled experiment
00:19:49 where you collide it against something else?
00:19:51 Yeah.
00:19:52 Is that, is that, that seems like an exceptionally difficult
00:19:55 engineering challenge because you mentioned vacuum too.
00:19:59 So you basically want to remove every other distraction
00:20:03 and really focus on this collision.
00:20:04 How difficult of an engineering challenge is that?
00:20:06 Just to get a sense.
00:20:07 And it is very hard.
00:20:09 I mean, in the early days,
00:20:10 particularly when the first accelerators are being built
00:20:12 in like 1932, Ernest Lawrence builds the first,
00:20:17 what we call a cyclotron,
00:20:18 which is like a little accelerator, this big or so.
00:20:21 There’s another one.
00:20:22 Is it really that big?
00:20:23 There’s a tiny little thing.
00:20:24 Yeah.
00:20:25 So most of the first accelerators
00:20:27 were what we call fixed target experiments.
00:20:31 So you had a ring, you accelerate particles around the ring
00:20:34 and then you fire them out the side into some target.
00:20:37 So that makes the kind of,
00:20:39 the colliding bit is relatively straightforward
00:20:41 because you just fire it,
00:20:42 whatever it is you want to fire it at.
00:20:43 The hard bit is the steering the beams
00:20:46 with the magnetic fields, getting, you know,
00:20:47 strong enough electric fields to accelerate them,
00:20:49 all that kind of stuff.
00:20:50 The first colliders where you have two beams
00:20:53 colliding head on, that comes later.
00:20:56 And I don’t think it’s done until maybe the 1980s.
00:21:01 I’m not entirely sure, but it’s a much harder problem.
00:21:05 That’s crazy.
00:21:06 Cause you have to like perfectly get them to hit each other.
00:21:09 I mean, we’re talking about, I mean, what scale it takes,
00:21:13 what’s the, I mean, the temporal thing is a giant mess,
00:21:18 but the spatially, like the size is tiny.
00:21:23 Well, to give you a sense of the LHC beams,
00:21:26 the cross sectional diameter is I think around a dozen
00:21:31 or so microns.
00:21:32 So, you know, 10 millionths of a meter.
00:21:37 And a beam, sorry, just to clarify,
00:21:39 a beam contains how many,
00:21:41 is it the bunches that you mentioned?
00:21:43 Is it multiple particles or is it just one particle?
00:21:45 Oh no, no.
00:21:45 The bunches contains say a hundred billion protons each.
00:21:48 So a bunch is, it’s not really bunch shaped.
00:21:51 They’re actually quite long.
00:21:51 They’re like 30 centimeters long,
00:21:53 but thinner than a human hair.
00:21:54 So like very, very narrow, long sort of objects.
00:21:58 Those are the things.
00:21:59 So what happens in the LHC is you steer the beams
00:22:02 so that they cross in the middle of the detector.
00:22:06 So they basically have these swarms of protons
00:22:08 that are flying through each other.
00:22:10 And most of the, you have to have a hundred billion
00:22:12 coming one way, a hundred billion another way,
00:22:14 maybe 10 of them will hit each other.
00:22:17 Oh, okay.
00:22:17 So this, okay, that makes a lot more sense.
00:22:19 So that’s nice.
00:22:20 But you’re trying to use sort of,
00:22:21 it’s like probabilistically, you’re not.
00:22:24 You can’t make a single particle collide
00:22:26 with a single other particle.
00:22:26 That’s not an efficient way to do it.
00:22:28 You’d be waiting a very long time to get anything.
00:22:30 So you’re basically, right.
00:22:34 You’re relying on probability to be that some fraction
00:22:37 of them are gonna collide.
00:22:38 And then you know which,
00:22:40 because it’s a swarm of the same kind of particle.
00:22:44 So it doesn’t matter which ones hit each other exactly.
00:22:46 I mean, that’s not to say it’s not hard.
00:22:48 You’ve got to, one of the challenges
00:22:50 to make the collisions work is you have to squash
00:22:52 these beams to very, very,
00:22:54 basically the narrower they are the better
00:22:56 cause the higher chances of them colliding.
00:22:58 If you think about two flocks of birds
00:23:00 flying through each other,
00:23:01 the birds are all far apart in the flocks.
00:23:03 There’s not much chance that they’ll collide.
00:23:04 If they’re all flying densely together,
00:23:06 then they’re much more likely to collide with each other.
00:23:08 So that’s the sort of problem.
00:23:10 And it’s tuning those magnetic fields,
00:23:12 getting the magnetic fields powerful enough
00:23:13 that you squash the beams and focus them
00:23:15 so that you get enough collisions.
00:23:16 That’s super cool.
00:23:17 Do you know how much software is involved here?
00:23:20 I mean, it’s sort of,
00:23:21 I come from the software world and it’s fascinating.
00:23:24 This seems like software is buggy and messy.
00:23:28 And so like, you almost don’t want to rely
00:23:30 on software too much.
00:23:31 Like if you do, it has to be like low level,
00:23:33 like Fortran style programming.
00:23:36 Do you know how much software
00:23:37 is in a large Hadron Collider?
00:23:39 I mean, it depends at which level a lot.
00:23:41 I mean, the whole thing is obviously computer controlled.
00:23:43 So, I mean, I don’t know a huge amount
00:23:45 about how the software for the actual accelerator works,
00:23:49 but I’ve been in the control center.
00:23:51 So at CERN, there’s this big control room,
00:23:53 which is like a bit like a NASA mission control
00:23:55 with big banks of desks where the engineers sit
00:23:57 and they monitor the LHC.
00:23:59 Cause you obviously can’t be in the tunnel
00:24:00 when it’s running.
00:24:01 So everything’s remote.
00:24:03 I mean, one sort of anecdote about the software side,
00:24:07 in 2008, when the LHC first switched on,
00:24:10 they had this big launch event
00:24:11 and then big press conference party
00:24:14 to inaugurate the machine.
00:24:16 And about 10 days after that,
00:24:18 they were doing some tests
00:24:19 and this dramatic event happened
00:24:22 where a huge explosion basically took place
00:24:24 in the tunnel that destroyed or damaged, badly damaged
00:24:26 about half a kilometer of the machine.
00:24:29 But the stories, the engineers
00:24:31 are in the control room that day.
00:24:33 One guy told me this story about,
00:24:35 basically all these screens they have in the control room
00:24:37 started going red.
00:24:38 So these alarms like kind of in software going off
00:24:42 and then they assume that there’s something wrong
00:24:43 with the software, cause there’s no way
00:24:45 something this catastrophic could have happened.
00:24:48 But I mean, when I worked on, when I was a PhD student,
00:24:52 one of my jobs was to help to maintain the software
00:24:56 that’s used to control the detector that we work on.
00:24:59 And that was, it’s relatively robust,
00:25:01 not such, you don’t want it to be too fancy.
00:25:02 You don’t want it to sort of fall over too easily.
00:25:04 The more clever stuff comes
00:25:07 when you’re talking about analyzing the data
00:25:08 and that’s where the sort of, you know.
00:25:10 Are we jumping around too much?
00:25:11 Do we finish with a standard model?
00:25:13 We didn’t, no.
00:25:14 We didn’t, so have we even started talking about quarks?
00:25:17 We haven’t talked to them yet.
00:25:17 No, we got to the messy zoo of particles.
00:25:20 Let me, let’s go back there if it’s okay.
00:25:22 Okay, that’s fine.
00:25:23 Can you take us to the rest of the history of physics
00:25:26 in the 20th century?
00:25:27 Okay, sure.
00:25:29 Okay, so circa 1960, you have this,
00:25:32 you have these a hundred or so particles.
00:25:33 It’s a bit like the periodic table all over again.
00:25:35 So you’ve got like having a hundred elements,
00:25:37 it’s sort of a bit like that.
00:25:39 And people start to try to impose some order.
00:25:41 So Murray Gellman, he’s a theoretical physicist,
00:25:46 American from New York.
00:25:47 He realizes that there are these symmetries
00:25:50 in these particles that if you arrange them in certain ways,
00:25:53 they relate to each other.
00:25:54 And he uses these symmetry principles
00:25:56 to predict the existence of particles
00:25:58 that haven’t been discovered,
00:25:59 which are then discovered in accelerators.
00:26:01 So this starts to suggest
00:26:02 there’s not just random collections of crap.
00:26:04 There’s like, you know, actually some order
00:26:06 to this underlying it.
00:26:08 A little bit later in 1960, again, around the 1960s,
00:26:14 he proposes along with another physicist called George Zweig
00:26:17 that these symmetries arise because
00:26:21 just like the patterns in the periodic table arise
00:26:23 because atoms are made of electrons and protons,
00:26:26 that these patterns are due to the fact
00:26:28 that these particles are made of smaller things.
00:26:30 And they are called quarks.
00:26:31 So these are the particles they’re predicted from theory.
00:26:34 For a long time, no one really believes they’re real.
00:26:36 A lot of people think that they’re a kind of theoretical
00:26:39 convenience that happened to fit the data,
00:26:41 but there’s no evidence.
00:26:42 No one’s ever seen a quark in any experiment.
00:26:45 And lots of experiments are done to try to find quarks,
00:26:48 to try to knock a quark out of a…
00:26:50 So the idea, if protons and neutrons are made of quarks,
00:26:52 you should be able to knock a quark out and see the quark.
00:26:55 That never happens.
00:26:56 And we still have never actually managed to do that.
00:26:58 Wait, really?
00:26:59 No.
00:27:00 So the way that it’s done in the end
00:27:02 is this machine that’s built in California
00:27:04 at the Stanford Lab, Stanford Linear Accelerator,
00:27:08 which is essentially a gigantic,
00:27:10 three kilometer long electron gun.
00:27:12 It fires electrons, almost the speed of light, at protons.
00:27:16 And when you do these experiments,
00:27:17 what you find is at very high energy,
00:27:20 the electrons bounce off small, hard objects
00:27:24 inside the proton.
00:27:25 So it’s a bit like taking an X ray of the proton.
00:27:28 You’re firing these very light, high energy particles,
00:27:31 and they’re pinging off little things inside the proton
00:27:34 that are like ball bearings, if you like.
00:27:36 So you actually, that way,
00:27:38 they resolve that there are three things
00:27:41 inside the proton, which are quarks,
00:27:42 the quarks that Gellman and Zweig had predicted.
00:27:45 So that’s really the evidence that convinces people
00:27:47 that these things are real.
00:27:49 The fact that we’ve never seen one
00:27:50 in an experiment directly,
00:27:51 they’re always stuck inside other particles.
00:27:56 And the reason for that is essentially
00:27:58 to do with a strong force.
00:27:59 The strong force is the force that holds quarks together.
00:28:01 And it’s so strong that it’s impossible
00:28:04 to actually liberate a quark.
00:28:06 So if you try and pull a quark out of a proton,
00:28:08 what actually ends up happening
00:28:09 is that you kind of create this spring like bond
00:28:14 in the strong force.
00:28:15 You imagine two quarks that are held together
00:28:16 by a very powerful spring.
00:28:18 You pull and pull and pull,
00:28:19 more and more energy gets stored in that bond,
00:28:22 like stretching a spring,
00:28:23 and eventually the tension gets so great,
00:28:25 the spring snaps, and the energy in that bond
00:28:28 gets turned into two new quarks
00:28:30 that go on the broken ends.
00:28:32 So you started with two quarks,
00:28:33 you end up with four quarks.
00:28:34 So you never actually get to take a quark out.
00:28:37 You just end up making loads more quarks in the process.
00:28:39 So how do we, again, forgive the dumb question,
00:28:42 how do we know quarks are real then?
00:28:44 Well, A, from these experiments where we can scatter,
00:28:48 you fire electrons into the protons.
00:28:49 They can burrow into the proton and knock off,
00:28:52 and they can bounce off these quarks.
00:28:55 So you can see from the angles,
00:28:56 the electrons come out.
00:28:58 I see, you can infer.
00:28:59 You can infer that these things are there.
00:29:02 The quark model can also be used.
00:29:03 It has a lot of successes that you can use it
00:29:05 to predict the existence of new particles
00:29:07 that hadn’t been seen.
00:29:08 So, and it basically, there’s lots of data
00:29:10 basically showing from, you know,
00:29:12 when we fire protons at each other at the LHC,
00:29:16 a lot of quarks get knocked all over the place.
00:29:18 And every time they try and escape from,
00:29:20 say, one of their protons,
00:29:21 they make a whole jet of quarks that go flying off,
00:29:25 bound up in other sorts of particles made of quarks.
00:29:28 So all the sort of the theoretical predictions
00:29:30 from the basic theory of the strong force and the quarks
00:29:33 all agrees with what we are seeing in experiments.
00:29:35 We’ve just never seen an actual quark on its own
00:29:38 because unfortunately it’s impossible
00:29:39 to get them out on their own.
00:29:41 So quarks, these crazy smaller things
00:29:45 that are hard to imagine are real.
00:29:47 So what else?
00:29:48 What else is part of the story here?
00:29:49 So the other thing that’s going on at the time,
00:29:52 around the 60s, is an attempt to understand the forces
00:29:57 that make these particles interact with each other.
00:30:00 So you have the electromagnetic force,
00:30:01 which is the force that was sort of discovered
00:30:03 to some extent in this room, or at least in this building.
00:30:07 So the first, what we call quantum field theory
00:30:10 of the electromagnetic force is developed
00:30:13 in the 1940s and 50s by Feynman,
00:30:17 Richard Feynman amongst other people,
00:30:19 Julian Schrodinger, Tom Onaga,
00:30:22 who come up with the first,
00:30:23 what we call a quantum field theory
00:30:24 of the electromagnetic force.
00:30:25 And this is where this description of,
00:30:27 which I gave you at the beginning,
00:30:28 that particles are ripples in fields.
00:30:30 Well, in this theory, the photon, the particle of light
00:30:33 is described as a ripple in this quantum field
00:30:36 called the electromagnetic field.
00:30:38 And the attempt then is made to try,
00:30:40 well, can we come up with a quantum field theory
00:30:42 of the other forces, of the strong force and the weak,
00:30:45 the third force, which we haven’t discussed,
00:30:47 which is the weak force, which is a nuclear force.
00:30:50 We don’t really experience it in our everyday lives,
00:30:52 but it’s responsible for radioactive decay.
00:30:54 It’s the force that allows, you know,
00:30:56 on a radioactive atom to turn
00:30:59 into a different element, for example.
00:31:01 And I don’t know if you’ve explicitly mentioned,
00:31:03 but so there’s technically four forces.
00:31:06 Yes.
00:31:06 I guess three of them would be in the standard model,
00:31:09 like the weak, the strong, and the electromagnetic,
00:31:13 and then there’s gravity.
00:31:14 And there’s gravity, which we don’t worry about that,
00:31:16 because it’s too hard.
00:31:17 It’s too hard.
00:31:17 Well, no, maybe we bring that up at the end, but yeah.
00:31:19 Gravity, so far, we don’t have a quantum theory of,
00:31:22 and if you can solve that problem,
00:31:23 you’ll win a Nobel Prize.
00:31:25 Well, we’re gonna have to bring up
00:31:26 the graviton at some point, I’m gonna ask you,
00:31:28 but let’s leave that to the side for now.
00:31:31 So those three, okay, Feynman, electromagnetic force,
00:31:36 the quantum field, and where does the weak force come in?
00:31:41 So yeah, well, first of all,
00:31:43 I mean, the strong force is the easiest.
00:31:44 The strong force is a little bit
00:31:46 like the electromagnetic force.
00:31:47 It’s a force that binds things together.
00:31:49 So that’s the force that holds quarks together
00:31:51 inside the proton, for example.
00:31:52 So a quantum field theory of that force
00:31:55 is discovered in the, I think it’s in the 60s,
00:31:59 and it predicts the existence
00:32:01 of new force particles called gluons.
00:32:04 So gluons are a bit like the photon.
00:32:06 The photon is the particle of electromagnetism.
00:32:09 Gluons are the particles of the strong force.
00:32:13 So just like there’s an electromagnetic field,
00:32:15 there’s something called a gluon field,
00:32:17 which is also all around us.
00:32:19 So some of these particles, I guess,
00:32:21 are the force carriers or whatever.
00:32:23 They carry the force.
00:32:24 It depends how you want to think about it.
00:32:25 I mean, really the field, the strong force field,
00:32:28 the gluon field is the thing that binds the quarks together.
00:32:32 The gluons are the little ripples in that field.
00:32:35 So that like, in the same way that the photon is a ripple
00:32:37 in the electromagnetic field.
00:32:39 But the thing that really does the binding is the field.
00:32:43 I mean, you may have heard people talk about things
00:32:45 like you’ve heard the phrase virtual particle.
00:32:49 So sometimes in some, if you hear people describing
00:32:52 how forces are exchanged between particles,
00:32:54 they quite often talk about the idea
00:32:56 that if you have an electron and another electron, say,
00:32:59 and they’re repelling each other
00:33:00 through the electromagnetic force,
00:33:03 you can think of that as if they’re exchanging photons.
00:33:05 So they’re kind of firing photons
00:33:07 backwards and forwards between each other.
00:33:08 And that causes them to repel.
00:33:11 That photon is then a virtual particle.
00:33:13 Yes, that’s what we call a virtual particle.
00:33:14 In other words, it’s not a real thing,
00:33:15 it doesn’t actually exist.
00:33:16 So it’s an artifact of the way theorists do calculations.
00:33:19 So when they do calculations in quantum field theory,
00:33:22 rather than, no one’s discovered a way
00:33:24 of just treating the whole field.
00:33:25 You have to break the field down into simpler things.
00:33:28 So you can basically treat the field
00:33:30 as if it’s made up of lots of these virtual photons,
00:33:33 but there’s no experiment that you can do
00:33:35 that can detect these particles being exchanged.
00:33:38 What’s really happening in reality
00:33:40 is that the electromagnetic field is warped
00:33:43 by the charge of the electron and that causes the force.
00:33:46 But the way we do calculations involves particles.
00:33:49 So it’s a bit confusing,
00:33:50 but it’s really a mathematical technique.
00:33:53 It’s not something that corresponds to reality.
00:33:55 I mean, that’s part, I guess, of the Feynman diagrams.
00:33:58 Yes.
00:33:59 Is this these virtual particles, okay.
00:34:00 That’s right, yeah.
00:34:01 Some of these have mass, some of them don’t.
00:34:06 What does that even mean, not to have mass?
00:34:09 And maybe you can say which one of them have mass
00:34:11 and which don’t.
00:34:12 Okay, so.
00:34:14 And why is mass important or relevant
00:34:17 in this field view of the universe?
00:34:22 Well, there are actually only two particles
00:34:23 in the standard model that don’t have mass,
00:34:25 which are the photon and the gluons.
00:34:28 So they are massless particles,
00:34:30 but the electron, the quarks,
00:34:32 and there are a bunch of other particles
00:34:34 I haven’t discussed.
00:34:34 There’s something called a muon and a tau,
00:34:36 which are basically heavy versions of the electron
00:34:39 that are unstable.
00:34:40 You can make them in accelerators,
00:34:41 but they don’t form atoms or anything.
00:34:44 They don’t exist for long enough.
00:34:45 But all the matter particles, there are 12 of them,
00:34:48 six quarks and six, what we call leptons,
00:34:51 which includes the electron and its two heavy versions
00:34:54 and three neutrinos, all of them have mass.
00:34:57 And so do, this is the critical bit.
00:34:59 So the weak force, which is the third of these
00:35:02 quantum forces, which is one of the hardest to understand,
00:35:07 the force particles of that force have very large masses.
00:35:13 And there are three of them.
00:35:14 They’re called the W plus, the W minus, and the Z boson.
00:35:19 And they have masses of between 80 and 90 times
00:35:23 that of the protons.
00:35:24 They’re very heavy.
00:35:25 Wow.
00:35:26 They’re very heavy things.
00:35:27 So they’re what, the heaviest, I guess?
00:35:29 They’re not the heaviest.
00:35:30 The heaviest particle is the top quark,
00:35:32 which has a mass of about 175 ish protons.
00:35:38 So that’s really massive.
00:35:39 And we don’t know why it’s so massive,
00:35:41 but coming back to the weak force,
00:35:43 so the problem in the 60s and 70s was that
00:35:47 the reason that the electromagnetic force
00:35:50 is a force that we can experience in our everyday lives.
00:35:51 So if we have a magnet and a piece of metal,
00:35:53 you can hold it, you know, a meter apart
00:35:55 if it’s powerful enough and you’ll feel a force.
00:35:57 Whereas the weak force only becomes apparent
00:36:00 when you basically have two particles touching
00:36:03 at the scale of a nucleus.
00:36:05 So we just get to very short distances
00:36:06 before this force becomes manifest.
00:36:09 It’s not, we don’t get weak forces going on in this room.
00:36:12 We don’t notice them.
00:36:14 And the reason for that is that the particle,
00:36:15 well, the field that transmits the weak force,
00:36:20 the particle that’s associated with that field
00:36:22 has a very large mass,
00:36:23 which means that the field dies off very quickly.
00:36:26 So as you, whereas an electric charge,
00:36:28 if you were to look at the shape of the electromagnetic field,
00:36:30 it would fall off with this,
00:36:32 you have this thing called the inverse square law,
00:36:33 which is the idea that the force halves
00:36:36 every time you double the distance.
00:36:38 No, sorry, it doesn’t half.
00:36:39 It quarters every time you double the distance
00:36:42 between say the two particles.
00:36:44 Whereas the weak force kind of,
00:36:45 you move a little bit away from the nucleus
00:36:47 and just disappears.
00:36:49 The reason for that is because these fields,
00:36:51 the particles that go with them have a very large mass.
00:36:55 But the problem that theorists faced in the 60s
00:36:59 was that if you tried to introduce massive force fields,
00:37:04 the theory gave you nonsensical answers.
00:37:06 So you’d end up with infinite results
00:37:08 for a lot of the calculations you tried to do.
00:37:11 So the basically, it seemed that quantum field theory
00:37:13 was incompatible with having massive particles,
00:37:17 not just the force particles actually,
00:37:18 but even the electron was a problem.
00:37:21 So this is where the Higgs
00:37:23 that we sort of alluded to comes in.
00:37:25 And the solution was to say, okay, well,
00:37:28 actually all the particles in the Standard Model are mass.
00:37:30 They have no mass.
00:37:31 So the quarks, the electron, they don’t have a mass.
00:37:33 Neither do these weak particles.
00:37:34 They don’t have mass either.
00:37:36 What happens is they actually acquire mass
00:37:38 through another process.
00:37:40 They get it from somewhere else.
00:37:41 They don’t actually have it intrinsically.
00:37:43 So this idea that was introduced by,
00:37:46 well, Peter Higgs is the most famous,
00:37:47 but actually there are about six people
00:37:49 that came up with the idea more or less at the same time,
00:37:52 is that you introduce a new quantum field,
00:37:55 which is another one of these invisible things
00:37:56 that’s everywhere.
00:37:58 And it’s through the interaction with this field
00:38:01 that particles get mass.
00:38:02 So you can think of say an electron in the Higgs field,
00:38:07 the Higgs field kind of bunches around the electron.
00:38:10 It’s sort of drawn towards the electron.
00:38:12 And that energy that’s stored in that field
00:38:15 around the electron is what we see
00:38:17 as the mass of the electron.
00:38:19 But if you could somehow turn off the Higgs field,
00:38:21 then all the particles in nature would become massless
00:38:23 and fly around at the speed of light.
00:38:26 So this idea of the Higgs field allowed other people,
00:38:32 other theorists to come up with a, well,
00:38:36 it was another, basically a unified theory
00:38:39 of the electromagnetic force and the weak force.
00:38:41 So once you bring in the Higgs field,
00:38:43 you can combine two of the forces into one.
00:38:45 So it turns out the electromagnetic force
00:38:47 and the weak force are just two aspects
00:38:49 of the same fundamental force.
00:38:52 And at the LHC, we go to high enough energies
00:38:54 that you see these two forces unifying effectively.
00:38:59 So first of all, it started as a theoretical notion,
00:39:04 like this is some, and then, I mean,
00:39:07 wasn’t the Higgs called the God particle at some point?
00:39:10 It was by a guy trying to sell popular science books, yeah.
00:39:13 Yeah, but I mean, I remember because when I was hearing it,
00:39:17 I thought it would, I mean, that would solve a lot of,
00:39:22 that unify a lot of our ideas of physics was my notion.
00:39:26 But maybe you can speak to that.
00:39:29 Is it as big of a leap as a God particle
00:39:32 or is it a Jesus particle, which, you know,
00:39:37 what’s the big contribution of Higgs
00:39:39 in terms of this unification power?
00:39:40 Yeah, I mean, to understand that,
00:39:42 it maybe helps know the history a little bit.
00:39:45 So when the, what we call electroweak theory
00:39:47 was put together, which is where you unify electromagnetism
00:39:50 with the weak force and Higgs is involved in all of that.
00:39:53 So that theory, which was written in the mid 70s,
00:39:55 predicted the existence of four new particles,
00:39:59 the W plus boson, the W minus boson,
00:40:01 the Z boson and the Higgs boson.
00:40:03 So there were these four particles
00:40:04 that came with the theory,
00:40:06 that were predicted by the theory.
00:40:07 In 1983, 84, the W’s and the Z particles
00:40:11 were discovered at an accelerator at CERN
00:40:14 called the super proton synchrotron,
00:40:15 which was a seven kilometer particle collider.
00:40:19 So three of the bits of this theory had already been found.
00:40:22 So people were pretty confident from the 80s
00:40:25 that the Higgs must exist
00:40:27 because it was a part of this family of particles
00:40:30 that this theoretical structure only works
00:40:33 if the Higgs is there.
00:40:34 So what then happens,
00:40:36 and so you’ve got this question about
00:40:37 why is the LHC the size it is?
00:40:39 Well, actually the tunnel that the LHC is in
00:40:41 was not built for the LHC.
00:40:42 It was built for a previous accelerator
00:40:45 called the large electron positron collider.
00:40:48 So that began operation in the late 80s, early 90s.
00:40:53 They basically, that’s when they dug
00:40:55 the 27 kilometer tunnel.
00:40:56 They put this accelerator into it,
00:40:58 the collider that fires electrons
00:40:59 and anti electrons at each other, electrons and positrons.
00:41:02 So the purpose of that machine was,
00:41:05 well, it was actually to look for the Higgs.
00:41:06 That was one of the things it was trying to do.
00:41:08 It didn’t have enough energy to do it in the end.
00:41:11 But the main thing it achieved was it studied
00:41:13 the W and the Z particles at very high precision.
00:41:17 So it made loads of these things.
00:41:19 Previously, you can only make a few of them
00:41:20 at the previous accelerator.
00:41:21 So you could study these really, really precisely.
00:41:24 And by studying their properties,
00:41:25 you could really test this electroweak theory
00:41:28 that had been invented in the 70s
00:41:29 and really make sure that it worked.
00:41:31 So actually by 1999, when this machine turned off,
00:41:36 people knew, well, okay, you never know
00:41:39 until you find the thing.
00:41:41 But people were really confident
00:41:43 this electroweak theory was right.
00:41:44 And that the Higgs almost,
00:41:46 the Higgs or something very like the Higgs had to exist
00:41:49 because otherwise the whole thing doesn’t work.
00:41:52 It’d be really weird if you could discover
00:41:54 and these particles, they all behave exactly
00:41:55 as your theory tells you they should.
00:41:57 But somehow this key piece of the picture is not there.
00:42:00 So in a way, it depends how you look at it.
00:42:03 The discovery of the Higgs on its own
00:42:07 is obviously a huge achievement in many,
00:42:09 both experimentally and theoretically.
00:42:12 On the other hand, it’s like having a jigsaw puzzle
00:42:15 where every piece has been filled in.
00:42:17 You have this beautiful image, there’s one gap
00:42:19 and you kind of know that piece must be there somewhere.
00:42:22 So the discovery in itself, although it’s important,
00:42:29 is not so interesting.
00:42:30 It’s like a confirmation of the obvious at that point.
00:42:34 But what makes it interesting
00:42:36 is not that it just completes the standard model,
00:42:38 which is a theory that we’ve known
00:42:39 had the basic layout offs for 40 years or more now.
00:42:44 It’s that the Higgs actually is a unique particle.
00:42:48 It’s very different to any of the other particles
00:42:50 in the standard model.
00:42:51 And it’s a theoretically very troublesome particle.
00:42:55 There are a lot of nasty things to do with the Higgs,
00:42:59 but also opportunities.
00:43:00 So that we basically, we don’t really understand
00:43:02 how such an object can exist in the form that it does.
00:43:06 So there are lots of reasons for thinking
00:43:08 that the Higgs must come with a bunch of other particles
00:43:12 or that it’s perhaps made of other things.
00:43:15 So it’s not a fundamental particle,
00:43:16 that it’s made of smaller things.
00:43:17 I can talk about that if you like a bit.
00:43:19 That’s still a notion, so the Higgs
00:43:23 might not be a fundamental particle,
00:43:24 that there might be some, it might, oh man.
00:43:27 So that is an idea, it’s not been demonstrated to be true.
00:43:31 But I mean, all of these ideas basically come
00:43:33 from the fact that this is a problem
00:43:37 that motivated a lot of development in physics
00:43:40 in the last 30 years or so.
00:43:42 And it’s this basic fact that the Higgs field,
00:43:44 which is this field that’s everywhere in the universe,
00:43:47 this is the thing that gives mass to the particles.
00:43:49 And the Higgs field is different from all the other fields
00:43:51 in that, let’s say you take the electromagnetic field,
00:43:54 which is, if we actually were to measure
00:43:56 the electromagnetic field in this room,
00:43:57 we would measure all kinds of stuff going on
00:43:58 because there’s light, there’s gonna be microwaves
00:44:00 and radio waves and stuff.
00:44:02 But let’s say we could go to a really, really remote part
00:44:04 of empty space and shield it and put a big box around it
00:44:07 and then measure the electromagnetic field in that box.
00:44:10 The field would be almost zero,
00:44:12 apart from some little quantum fluctuations,
00:44:14 but basically it goes to naught.
00:44:16 The Higgs field has a value everywhere.
00:44:19 So it’s a bit like the whole,
00:44:20 it’s like the entire space has got this energy
00:44:23 stored in the Higgs field, which is not zero,
00:44:25 it’s finite, it’s a bit like having the temperature
00:44:28 of space raised to some background temperature.
00:44:33 And it’s that energy that gives mass to the particles.
00:44:36 So the reason that electrons and quarks have mass
00:44:40 is through the interaction with this energy
00:44:42 that’s stored in the Higgs field.
00:44:44 Now, it turns out that the precise value this energy has
00:44:50 has to be very carefully tuned if you want a universe
00:44:55 where interesting stuff can happen.
00:44:58 So if you push the Higgs field down,
00:45:00 it has a tendency to collapse to,
00:45:03 well, there’s a tendency,
00:45:04 if you do your sort of naive calculations,
00:45:05 there are basically two possible likely configurations
00:45:08 for the Higgs field, which is either it’s zero everywhere,
00:45:11 in which case you have a universe
00:45:12 which is just particles with no mass that can’t form atoms
00:45:15 and just fly about at the speed of light,
00:45:18 or it explodes to an enormous value,
00:45:20 what we call the Planck scale,
00:45:21 which is the scale of quantum gravity.
00:45:24 And at that point, if the Higgs field was that strong,
00:45:27 even an electron would become so massive
00:45:28 that it would collapse into a black hole.
00:45:31 And then you have a universe made of black holes
00:45:33 and nothing like us.
00:45:34 So it seems that the strength of the Higgs field
00:45:37 is to achieve the value that we see
00:45:40 requires what we call fine tuning of the laws of physics.
00:45:42 You have to fiddle around with the other fields
00:45:45 in the Standard Model and their properties
00:45:47 to just get it to this right sort of Goldilocks value
00:45:50 that allows atoms to exist.
00:45:53 This is deeply fishy.
00:45:54 People really dislike this.
00:45:57 Well, yeah, I guess, so what would be,
00:45:59 so two explanations.
00:46:00 One, there’s a god that designed this perfectly,
00:46:03 and two is there’s an infinite number
00:46:05 of alternate universes,
00:46:07 and we just happen to be in the one in which life
00:46:10 is possible, complexity.
00:46:12 So when you say, I mean, life, any kind of complexity,
00:46:15 that’s not either complete chaos or black holes.
00:46:21 I mean, how does that make you feel?
00:46:22 What do you make of that?
00:46:23 That’s such a fascinating notion
00:46:25 that this perfectly tuned field
00:46:28 that’s the same everywhere is there.
00:46:31 What do you make of that?
00:46:33 Yeah, what do you make of that?
00:46:34 I mean, yeah, so you laid out
00:46:35 two of the possible explanations.
00:46:36 Really?
00:46:37 Some, well, yeah, I mean, well,
00:46:38 someone, some cosmic creator went,
00:46:41 yeah, let’s fix that to be at the right level.
00:46:43 That’s one possibility, I guess.
00:46:44 It’s not a scientifically testable one,
00:46:45 but theoretically, I guess, it’s possible.
00:46:48 Sorry to interrupt, but there could also be
00:46:50 not a designer, but couldn’t there be just,
00:46:54 I guess I’m not sure what that would be,
00:46:55 but some kind of force that,
00:46:58 that some kind of mechanism
00:47:03 by which this kind of field is enforced
00:47:09 in order to create complexity,
00:47:11 basically forces that pull the universe
00:47:16 towards an interesting complexity.
00:47:19 I mean, yeah, I mean, there are people
00:47:21 who have those ideas.
00:47:22 I don’t really subscribe to them.
00:47:23 As I’m saying, it sounds really stupid.
00:47:25 No, I mean, there are definitely people
00:47:27 that make those kind of arguments.
00:47:29 There’s ideas that, I think it’s Lee Smolin’s idea,
00:47:33 or one, I think, that universes are born inside black holes.
00:47:38 And so, universes, they basically have
00:47:40 like Darwinian evolution of the universe,
00:47:42 where universes give birth to other universes.
00:47:44 And if universes where black holes can form
00:47:46 are more likely to give birth to more universes,
00:47:48 so you end up with universes which have similar laws.
00:47:51 I mean, I don’t know, whatever.
00:47:52 Well, I talked to Lee recently on this podcast,
00:47:57 and he’s a reminder to me that the physics community
00:48:02 has like so many interesting characters in it.
00:48:05 It’s fascinating.
00:48:06 Anyway, sorry, so.
00:48:08 I mean, as an experimentalist, I tend to sort of think,
00:48:10 these are interesting ideas, but they’re not really testable,
00:48:12 so I tend not to think about them very much.
00:48:14 So, I mean, going back to the science of this,
00:48:17 there is an explanation.
00:48:19 There is a possible solution to this problem of the Higgs,
00:48:21 which doesn’t involve multiverses or creators fiddling about
00:48:25 with the laws of physics.
00:48:26 If the most popular solution
00:48:28 was something called supersymmetry,
00:48:30 which is a theory which involves a new type of symmetry
00:48:34 of the universe.
00:48:35 In fact, it’s one of the last types of symmetries
00:48:37 that it’s possible to have
00:48:38 that we haven’t already seen in nature,
00:48:40 which is a symmetry between force particles
00:48:43 and matter particles.
00:48:44 So what we call fermions, which are the matter particles
00:48:47 and bosons, which are force particles.
00:48:49 And if you have supersymmetry, then there is a super partner
00:48:52 for every particle in the standard model.
00:48:55 And without going into the details,
00:48:57 the effect of this basically is that you have
00:48:59 a whole bunch of other fields,
00:49:01 and these fields cancel out the effect
00:49:04 of the standard model fields,
00:49:05 and they stabilize the Higgs field at a nice sensible value.
00:49:09 So in supersymmetry, you naturally,
00:49:11 without any tinkering about with the constants of nature
00:49:14 or anything, you get a Higgs field with a nice value,
00:49:17 which is the one we see.
00:49:18 So this is one of the,
00:49:20 and supersymmetry’s also got lots of other things
00:49:22 going for it.
00:49:22 It predicts the existence of a dark matter particle,
00:49:25 which would be great.
00:49:27 It potentially suggests that the strong force
00:49:30 and the electroweak force unify at high energy.
00:49:32 So lots of reasons people thought this was a productive idea.
00:49:35 And when the LHC was, just before it was turned on,
00:49:37 there was a lot of hype, I guess,
00:49:39 a lot of an expectation that we would discover
00:49:42 these super partners because,
00:49:44 and particularly the main reason was
00:49:46 that if supersymmetry stabilizes the Higgs field
00:49:50 at this nice Goldilocks value,
00:49:52 these super particles should have a mass
00:49:55 around the energy that we’re probing at the LHC,
00:49:58 around the energy of the Higgs.
00:49:59 So it was kind of thought, you discover the Higgs,
00:50:01 you probably discover super partners as well.
00:50:03 So once you start creating ripples in this Higgs field,
00:50:06 you should be able to see these kinds of,
00:50:08 you should be, yeah.
00:50:09 So the super fields would be there.
00:50:11 When I, at the very beginning I said,
00:50:12 we’re probing the vacuum.
00:50:13 What I mean is really that, you know,
00:50:15 okay, let’s say these super fields exist.
00:50:16 The vacuum contains super fields.
00:50:18 They’re there, these supersymmetric fields.
00:50:20 If we hit them hard enough, we can make them vibrate.
00:50:22 We see super particles come flying out.
00:50:24 That’s the sort of, that’s the idea.
00:50:26 That’s the whole, okay.
00:50:27 That’s the whole point.
00:50:29 But we haven’t.
00:50:30 But we haven’t.
00:50:31 So, so far at least, I mean,
00:50:33 we’ve had now a decade of data taking at the LHC.
00:50:38 No signs of super partners have,
00:50:41 supersymmetric particles have been found.
00:50:43 In fact, no signs of any physics, any new particles
00:50:46 beyond the Standard Model have been found.
00:50:47 So supersymmetry is not the only thing that can do this.
00:50:49 There are other theories that involve
00:50:51 additional dimensions of space
00:50:53 or potentially involve the Higgs boson
00:50:55 being made of smaller things,
00:50:56 being made of other particles.
00:50:58 Yeah, that’s an interesting, you know,
00:50:59 I haven’t heard that before.
00:51:00 That’s really, that’s an interesting,
00:51:02 but can you maybe linger on that?
00:51:03 Like what, what could be,
00:51:06 what could the Higgs particle be made of?
00:51:08 Well, so the oldest, I think the original ideas about this
00:51:11 was these theories called technicolor,
00:51:14 which were basically like an analogy with the strong force.
00:51:17 So the idea was the Higgs boson was a bound state
00:51:21 of two very strongly interacting particles
00:51:24 that were a bit like quarks.
00:51:25 So like quarks, but I guess higher energy things
00:51:29 with a super strong force.
00:51:30 So not the strong force, but a new force
00:51:31 that was very strong.
00:51:33 And the Higgs was a bound state of these, these objects.
00:51:36 And the Higgs would in principle, if that was right,
00:51:38 would be the first in a series of technicolor particles.
00:51:42 Technicolor, I think not being a theorist,
00:51:45 but it’s not, it’s basically not done very well,
00:51:48 particularly since the LHC found the Higgs,
00:51:49 that kind of, it rules out, you know,
00:51:52 a lot of these technicolor theories,
00:51:53 but there are other things that are a bit like technicolor.
00:51:55 So there’s a theory called partial composite,
00:52:00 which is an idea that some of my colleagues
00:52:02 at Cambridge have worked on,
00:52:04 which is a similar sort of idea that the Higgs
00:52:06 is a bound state of some strongly interacting particles,
00:52:10 and that the standard model particles themselves,
00:52:13 the more exotic ones like the top quark
00:52:16 are also sort of mixtures of these composite particles.
00:52:20 So it’s a kind of an extension to the standard model,
00:52:23 which explains this problem
00:52:25 with the Higgs bosons, Goldilocks value,
00:52:28 but also helps us understand we have,
00:52:31 we’re in a situation now, again,
00:52:32 a bit like the periodic table,
00:52:34 where we have six quarks, six leptons in this kind of,
00:52:38 you can arrange in this nice table
00:52:40 and you can see these columns where the patterns repeat
00:52:42 and you go, okay, maybe there’s something deeper
00:52:46 going on here, you know,
00:52:47 and so this would potentially be something,
00:52:49 this partial composite theory could explain,
00:52:52 a sort of enlarge this picture
00:52:54 that allows us to see the whole symmetrical pattern
00:52:56 and understand what the ingredients, why do we have,
00:52:59 so one of the big questions in particle physics is,
00:53:02 why are there three copies of the matter particles?
00:53:06 So in what we call the first generation,
00:53:07 which is what we’re made of,
00:53:08 there’s the electron, the electron neutrino,
00:53:11 the up quark and the down quark,
00:53:13 they’re the most common matter particles in the universe,
00:53:15 but then there are copies of these four particles
00:53:18 in the second and the third generations,
00:53:20 so things like nuons and top quarks and other stuff,
00:53:23 we don’t know why, we see these patterns,
00:53:25 we have no idea where it comes from,
00:53:26 so that’s another big question, you know,
00:53:28 can we find out the deeper order that explains
00:53:32 this particular periodic table of particles that we see?
00:53:36 Is it possible that the deeper order includes
00:53:40 like almost a single entity,
00:53:42 so like something that I guess like string theory
00:53:44 dreams about, is this essentially the dream,
00:53:50 is to discover something simple, beautiful and unifying?
00:53:54 Yeah, I mean, that is the dream,
00:53:55 and I think for some people, for a lot of people,
00:53:59 it still is the dream,
00:54:00 so there’s a great book by Steven Weinberg,
00:54:03 who is one of the theoretical physicists
00:54:05 who was instrumental in building the Standard Model,
00:54:08 so he came up with some others with the electroweak theory,
00:54:12 the theory that unified electromagnetism and the weak force,
00:54:14 and he wrote this book,
00:54:15 I think it was towards the end of the 80s, early 90s,
00:54:18 called Dreams of a Final Theory,
00:54:20 which is a very lovely, quite short book
00:54:22 about this idea of a final unifying theory
00:54:26 that brings everything together,
00:54:27 and I think you get a sense reading his book
00:54:29 written at the end of the 80s, early 90s,
00:54:31 that there was this feeling that such a theory was coming,
00:54:37 and that was the time when string theory
00:54:39 was very exciting, so string theory,
00:54:41 there’s been this thing called the superstring revolution,
00:54:44 and theoretical physicists were very excited,
00:54:46 they discovered these theoretical objects,
00:54:47 these little vibrating loops of string
00:54:49 that in principle not only was a quantum theory of gravity
00:54:52 but could explain all the particles in the Standard Model
00:54:54 and bring it all together,
00:54:55 and as you say, you have one object, the string,
00:54:59 and you can pluck it, and the way it vibrates
00:55:02 gives you these different notes,
00:55:03 each of which is a different particle,
00:55:05 so it’s a very lovely idea,
00:55:08 but the problem is that, well, there’s a few,
00:55:11 people discover that mathematics is very difficult,
00:55:14 so people have spent three decades or more
00:55:17 trying to understand string theory,
00:55:19 and I think if you spoke to most string theorists,
00:55:21 they would probably freely admit
00:55:22 that no one really knows what string theory is yet,
00:55:24 I mean, there’s been a lot of work,
00:55:26 but it’s not really understood,
00:55:27 and the other problem is that string theory
00:55:31 mostly makes predictions about physics
00:55:34 that occurs at energies far beyond
00:55:36 what we will ever be able to probe in the laboratory.
00:55:40 Yeah, probably ever.
00:55:42 By the way, so sorry to take a million tangents,
00:55:44 but is there room for complete innovation
00:55:48 of how to build a particle collider
00:55:50 that could give us an order of magnitude increase
00:55:52 in the kind of energies,
00:55:55 or do we need to keep just increasing the size of things?
00:55:58 I mean, maybe, yeah, I mean, there are ideas,
00:56:00 to give you a sense of the gulf that has to be bridged.
00:56:03 So the LHC collides particles at an energy
00:56:09 of what we call 14 tera electron volts,
00:56:13 so that’s basically the equivalent
00:56:15 if you’ve accelerated a proton through 14 trillion volts.
00:56:19 That gets us to the energies
00:56:20 where the Higgs and these weak particles live.
00:56:23 They’re very massive.
00:56:24 The scale where strings become manifest
00:56:27 is something called the Planck scale,
00:56:29 which I think is of the order 10 to the,
00:56:31 hang on, get this right,
00:56:33 it’s 10 to the 18 giga electron volts,
00:56:35 so about 10 to the 15 tera electron volts.
00:56:41 So you’re talking trillions of times more energy.
00:56:44 Yeah, 10 to the 15th or 10 to the 14th larger, I don’t even.
00:56:49 It’s of that order.
00:56:50 It’s a very big number.
00:56:52 So we’re not talking just an order
00:56:54 of magnitude increase in energy,
00:56:55 we’re talking 14 orders of magnitude energy increase.
00:56:58 So to give you a sense of what that would look like,
00:57:01 were you to build a particle accelerator
00:57:03 with today’s technology.
00:57:04 Bigger or smaller than our solar system?
00:57:07 The size of the galaxy.
00:57:09 The galaxy.
00:57:10 So you’d need to put a particle accelerator
00:57:11 that circled the Milky Way to get to the energies
00:57:14 where you would see strings if they exist.
00:57:17 So that is a fundamental problem,
00:57:20 which is that most of the predictions
00:57:22 of these unified theories, quantum theories of gravity,
00:57:26 only make statements that are testable at energies
00:57:29 that we will not be able to probe,
00:57:32 and barring some unbelievable,
00:57:35 completely unexpected technological
00:57:37 or scientific breakthrough,
00:57:38 which is almost impossible to imagine.
00:57:40 You never say never, but it seems very unlikely.
00:57:42 Yeah, I can just see the news story.
00:57:45 Elon Musk decides to build a particle collider
00:57:48 the size of our galaxy.
00:57:51 We’d have to get together
00:57:51 with all our galactic neighbors to pay for it, I think.
00:57:55 What is the exciting possibilities
00:57:56 of the Large Hadron Collider?
00:57:58 What is there to be discovered
00:58:00 in this order of magnitude of scale?
00:58:04 Is there other bigger efforts on the horizon in this space?
00:58:09 What are the open problems, the exciting possibilities?
00:58:12 You mentioned supersymmetry.
00:58:14 Yeah, so, well, there are lots of new ideas.
00:58:17 Well, there are lots of problems that we’re facing.
00:58:18 So there’s a problem with the Higgs field,
00:58:20 which supersymmetry was supposed to solve.
00:58:23 There’s the fact that 95% of the universe
00:58:25 we know from cosmology, astrophysics, is invisible,
00:58:29 that it’s made of dark matter and dark energy,
00:58:31 which are really just words
00:58:33 for things that we don’t know what they are.
00:58:35 It’s what Donald Rumsfeld called a known unknown.
00:58:37 So we know we don’t know what they are.
00:58:39 Well, that’s better than unknown unknown.
00:58:42 Yeah, well, there may be some unknown unknowns,
00:58:43 but by definition we don’t know what those are, so, yeah.
00:58:47 But the hope is a particle accelerator
00:58:52 could help us make sense of dark energy, dark matter.
00:58:55 There’s still, there’s some hope for that?
00:58:57 There’s hope for that, yeah.
00:58:58 So one of the hopes is the LHC could produce
00:59:01 a dark matter particle in its collisions.
00:59:03 And it may be that the LHC
00:59:08 will still discover new particles,
00:59:09 that it might still, supersymmetry could still be there.
00:59:11 It’s just maybe more difficult to find
00:59:14 than we thought originally.
00:59:15 And dark matter particles might be being produced,
00:59:18 but we’re just not looking in the right part of the data
00:59:20 for them, that’s possible.
00:59:22 It might be that we need more data,
00:59:23 that these processes are very rare
00:59:24 and we need to collect lots and lots of data
00:59:26 before we see them.
00:59:27 But I think a lot of people would say now
00:59:29 that the chances of the LHC
00:59:33 directly discovering new particles
00:59:36 in the near future is quite slim.
00:59:37 It may be that we need a decade more data
00:59:40 before we can see something, or we may not see anything.
00:59:43 That’s the, that’s where we are.
00:59:45 So, I mean, the physics, the experiments that I work on,
00:59:48 so I work on a detector called LHCb,
00:59:50 which is one of these four big detectors
00:59:52 that are spaced around the ring.
00:59:54 And we do slightly different stuff to the big guys.
00:59:57 There’s two big experiments called Atlas and CMS,
01:00:00 3000 physicists and scientists
01:00:02 and computer scientists on them each.
01:00:04 They are the ones that discovered the Higgs
01:00:06 and they look for supersymmetry and dark matter and so on.
01:00:08 What we look at are standard model particles
01:00:11 called bequarks, which depending on your preferences,
01:00:14 either bottom or beauty,
01:00:16 we tend to say beauty because it sounds sexier.
01:00:18 Yeah, for sure.
01:00:20 But these particles are interesting
01:00:22 because they have, we can make lots of them.
01:00:25 We make billions or hundreds of billions of these things.
01:00:28 You can therefore measure their properties very precisely.
01:00:31 So you can make these really lovely precision measurements.
01:00:34 And what we are doing really is a sort of complimentary thing
01:00:39 to the other big experiments, which is they,
01:00:41 if you think of the sort of analogy they often use is,
01:00:44 if you imagine you’re looking in, you’re in the jungle
01:00:45 and you’re looking for an elephant, say,
01:00:48 and you are a hunter and you’re kind of like,
01:00:52 let’s say there’s the relevance, very rare.
01:00:53 You don’t know where in the jungle, the jungle’s big.
01:00:55 So there’s two ways you go about this.
01:00:56 Either you can go wandering around the jungle
01:00:58 and try and find the elephant.
01:01:00 The problem is if the elephant,
01:01:01 if there’s only one elephant and the jungle’s big,
01:01:02 the chances of running into it are very small.
01:01:04 Or you could look on the ground
01:01:07 and see if you see footprints left by the elephant.
01:01:09 And if the elephant’s moving around, you’ve got a chance,
01:01:11 that you’re better chance maybe
01:01:12 of seeing the elephant’s footprints.
01:01:13 If you see the footprints, you go, okay, there’s an elephant.
01:01:16 I maybe don’t know what kind of elephant it is,
01:01:18 but I got a sense there’s something out there.
01:01:20 So that’s sort of what we do.
01:01:21 We are the footprint people.
01:01:23 We are, we’re looking for the footprints,
01:01:25 the impressions that quantum fields
01:01:28 that we haven’t managed to directly create the particle of,
01:01:32 the effects these quantum fields have
01:01:33 on the ordinary standard model fields
01:01:35 that we already know about.
01:01:36 So these B particles, the way they behave
01:01:39 can be influenced by the presence of say,
01:01:41 super fields or dark matter fields or whatever you like.
01:01:45 And the way they decay and behave can be altered slightly
01:01:48 from what our theory tells us they ought to behave.
01:01:52 And it’s easier to collect huge amounts of data
01:01:54 on B quarks.
01:01:56 We get billions and billions of these things.
01:01:58 You can make very precise measurements.
01:02:00 And the only place really at the LHC
01:02:03 or really in high energy physics at the moment
01:02:05 where there’s fairly compelling evidence
01:02:08 that there might be something beyond the standard model
01:02:10 is in these B, these beauty quarks decays.
01:02:15 Just to clarify, which is the difference
01:02:18 between the different, the four experiments,
01:02:20 for example, that you mentioned,
01:02:21 is it the kind of particles that are being collided?
01:02:24 Is it the energies which they’re collided?
01:02:27 What’s the fundamental difference
01:02:28 between the different experiments?
01:02:30 The collisions are the same.
01:02:32 What’s different is the design of the detectors.
01:02:34 So Atlas and CMS are called,
01:02:37 they’re called what are called general purpose detectors.
01:02:39 And they are basically barrel shaped machines
01:02:42 and the collisions happen in the middle of the barrel
01:02:44 and the barrel captures all the particles
01:02:46 that go flying out in every direction.
01:02:48 So in a sphere effectively that can fly out
01:02:49 and it can record all of those particles.
01:02:51 And what’s the, sorry to be interrupting,
01:02:54 but what’s the mechanism of the recording?
01:02:57 Oh, so these detectors, if you’ve seen pictures of them,
01:02:59 they’re huge, like Atlas is 25 meters high
01:03:03 and 45 meters long, they’re vast machines,
01:03:07 instruments, I guess you should call them really.
01:03:09 They are, they’re kind of like onions.
01:03:11 So they have layers, concentric layers of detectors,
01:03:15 different sorts of detectors.
01:03:16 So close into the beam pipe,
01:03:18 you have what are called usually made of silicon,
01:03:20 they’re tracking detectors.
01:03:21 So they’re little made of strips of silicon
01:03:23 or pixels of silicon.
01:03:24 And when a particle goes through the silicon,
01:03:26 it gives a little electrical signal
01:03:28 and you get these dots, electrical dots
01:03:30 through your detector, which allows you
01:03:31 to reconstruct the trajectory of the particle.
01:03:34 So that’s the middle
01:03:34 and then the outsides of these detectors,
01:03:36 you have things called calorimeters,
01:03:37 which measure the energies of the particles
01:03:39 and the very edge you have things called muon chambers,
01:03:42 which basically these muon particles,
01:03:44 which are the heavy version of the electron,
01:03:46 they’re like high velocity bullets
01:03:48 and they can get right to the edge of the detectors.
01:03:50 If you see something at the edge, that’s a muon.
01:03:52 So that’s broadly how they work.
01:03:54 And all of that is being recorded.
01:03:55 That’s all being fed out to, you know, computers.
01:03:58 Data must be awesome, okay.
01:04:00 So LHCb is different.
01:04:02 So we, because we’re looking for these be quarks,
01:04:04 be quarks tend to be produced along the beam line.
01:04:07 So in a collision, the be quark tend to fly
01:04:10 sort of close to the beam pipe.
01:04:12 So we built a detector that sort of pyramid cone shaped
01:04:15 basically, that just looks in one direction.
01:04:18 So we ignore, if you have your collision,
01:04:20 stuff goes everywhere.
01:04:21 We ignore all the stuff over here and going off sideways.
01:04:23 We’re just looking in this little region
01:04:26 close to the beam pipe
01:04:27 where most of these be quarks are made.
01:04:28 So is there a different aspect of the sensors involved
01:04:34 in the collection of the be quark trajectories?
01:04:37 There are some differences.
01:04:38 So one of the differences is that,
01:04:40 one of the ways you know you’ve seen a be quark
01:04:42 is that be quarks are actually quite long lived
01:04:44 by particle standards.
01:04:45 So they live for 1.5 trillionths of a second,
01:04:49 which is if you’re a fundamental particle
01:04:50 is a very long time.
01:04:51 Cause the Higgs boson, I think lives for about
01:04:54 a trillionth of a trillionth of a second,
01:04:57 or maybe even less than that.
01:04:58 So these are quite long lived things
01:05:00 and they will actually fly a little distance
01:05:02 before they decay.
01:05:03 So they will fly a few centimeters maybe if you’re lucky,
01:05:06 then they’ll decay into other stuff.
01:05:07 So what we need to do in the middle of the detector,
01:05:10 you wanna be able to see,
01:05:12 you have your place where the protons crash into each other
01:05:14 and that produces loads of particles that come flying out.
01:05:16 So you have loads of lines, loads of tracks
01:05:18 that point back to that proton collision.
01:05:21 And then you’re looking for a couple of other tracks,
01:05:23 maybe two or three that point back to a different place
01:05:25 that’s maybe a few centimeters away
01:05:27 from the proton collision.
01:05:28 And that’s the sign that a little B particle has flown
01:05:31 a few centimeters and decayed somewhere else.
01:05:33 So we need to be able to very accurately resolve
01:05:36 the proton collision from the B particle decay.
01:05:39 So the middle of our detector is very sensitive
01:05:42 and it gets very close to the collision.
01:05:44 So you have this really beautiful delicate
01:05:46 silicon detector that sits,
01:05:48 I think it’s seven millimeters from the beam.
01:05:52 And the LHC beam has as much energy
01:05:53 as a jumbo jet at takeoff.
01:05:55 So it’s enough to melt a ton of copper.
01:05:57 So you have this furiously powerful thing sitting next
01:05:59 to this tiny delicate silicon sensor.
01:06:03 So those aspects of our detector that are specialized
01:06:07 to measure these particular B quarks
01:06:09 that we’re interested in.
01:06:10 And is there, I mean, I remember seeing somewhere
01:06:12 that there’s some mention of matter and antimatter
01:06:15 connected to the B, these beautiful quarks.
01:06:18 Is that, what’s the connection?
01:06:23 Yeah, what’s the connection there?
01:06:25 Yeah, so there is a connection, which is that
01:06:29 when you produce these B particles,
01:06:31 these particles, because you don’t see the B quark,
01:06:33 you see the thing that B quark is inside.
01:06:35 So they’re bound up inside what we call beauty particles,
01:06:37 where the B quark is joined together with another quark
01:06:40 or two, maybe two other quarks, depending on what it is.
01:06:43 They’re a particular set of these B particles
01:06:46 that exhibit this property called oscillation.
01:06:49 So if you make a, for the sake of argument,
01:06:52 a matter version of one of these B particles,
01:06:55 as it travels, because of the magic of quantum mechanics,
01:06:58 it oscillates backwards and forwards
01:07:01 between its matter and antimatter versions.
01:07:03 So it does this weird flipping about backwards and forwards.
01:07:06 And what we can use this for is a laboratory
01:07:09 for testing the symmetry between matter and antimatter.
01:07:12 So if the symmetry between antimatter is precise,
01:07:15 it’s exact, then we should see these B particles decaying
01:07:20 as often as matter, as they do as antimatter,
01:07:21 because this oscillation should be even.
01:07:23 It should spend as much time in each state.
01:07:26 But what we actually see is that one of the states,
01:07:29 it spends more time and it’s more likely to decay
01:07:31 in one state than the other.
01:07:32 So this gives us a way of testing this fundamental symmetry
01:07:36 between matter and antimatter.
01:07:39 So what can you, sort of returning to the question
01:07:42 before about this fundamental symmetry,
01:07:44 it seems like if there’s perfect symmetry
01:07:46 between matter and antimatter,
01:07:50 if we have the equal amount of each in our universe,
01:07:54 it would just destroy itself.
01:07:57 And just like you mentioned,
01:07:58 we seem to live in a very unlikely universe
01:08:00 where it doesn’t destroy itself.
01:08:03 So do you have some intuition about why that is?
01:08:07 I mean, well, I’m not a theorist.
01:08:10 I don’t have any particular ideas myself.
01:08:11 I mean, I sort of do measurements
01:08:13 to try and test these things,
01:08:14 but I mean, so the terms of the basic problem
01:08:16 is that in the Big Bang,
01:08:17 if you use the standard model to figure out
01:08:19 what ought to have happened,
01:08:20 you should have got equal amounts of matter
01:08:21 and antimatter made,
01:08:22 because whenever you make a particle
01:08:23 in our collisions, for example,
01:08:25 when we collide stuff together,
01:08:26 you make a particle, you make an antiparticle.
01:08:28 They always come together.
01:08:29 They always annihilate together.
01:08:30 So there’s no way of making more matter than antimatter
01:08:33 that we’ve discovered so far.
01:08:35 So that means in the Big Bang,
01:08:36 you get equal amounts of matter and antimatter.
01:08:38 As the universe expands and cools down during the Big Bang,
01:08:41 not very long after the Big Bang,
01:08:43 I think a few seconds after the Big Bang,
01:08:45 you have this event called the Great Annihilation,
01:08:47 which is where all the particles and antiparticles
01:08:49 smack into each other, annihilate, turn into light mostly,
01:08:53 and you end up with a universe later on.
01:08:55 If that was what happened,
01:08:55 then the universe we live in today would be black and empty,
01:08:58 apart from some photons, that would be it.
01:09:01 So there is stuff in the universe.
01:09:03 It appears to be just made of matter.
01:09:04 So there’s this big mystery as to how did this happen?
01:09:08 And there are various ideas,
01:09:09 which all involve sort of physics going on
01:09:13 in the first trillionth of a second or so of the Big Bang.
01:09:17 So it could be that one possibility
01:09:20 is that the Higgs field is somehow implicated in this,
01:09:22 that there was this event that took place
01:09:25 in the early universe where the Higgs field
01:09:27 basically switched on, it acquired its modern value.
01:09:31 And when that happened,
01:09:33 this caused all the particles to acquire mass
01:09:35 and the universe basically went through a phase transition
01:09:37 where you had a hot plasma of massless particles.
01:09:41 And then in that plasma,
01:09:42 it’s almost like a gas turning into droplets of water.
01:09:44 You get kind of these little bubbles forming in the universe
01:09:47 where the Higgs field has acquired its modern value,
01:09:50 the particles have got mass.
01:09:52 And this phase transition in some models
01:09:55 can cause more matter than antimatter to be produced,
01:09:57 depending on how matter bounces off these bubbles
01:10:00 in the early universe.
01:10:01 So that’s one idea.
01:10:02 There’s other ideas to do with neutrinos,
01:10:04 that there are exotic types of neutrinos
01:10:06 that can decay in a biased way to just matter
01:10:09 and not to antimatter.
01:10:10 So, and people are trying to test these ideas.
01:10:12 That’s what we’re trying to do at LHCb.
01:10:14 There’s neutrino experiments planned
01:10:15 that are trying to do these sorts of things as well.
01:10:17 So yeah, there are ideas, but at the moment,
01:10:19 no clear evidence for which of these ideas might be right.
01:10:22 So we’re talking about some incredible ideas.
01:10:25 By the way, never heard anyone be so eloquent
01:10:28 about describing even just the standard model.
01:10:31 So I’m in awe just listening.
01:10:34 Oh, thank you.
01:10:35 Yeah, just having fun enjoying it.
01:10:38 So the, yes, the theoretical,
01:10:40 the particle physics is fascinating here.
01:10:42 To me, one of the most fascinating things
01:10:44 about the Large Hadron Collider is the human side of it.
01:10:47 That a bunch of sort of brilliant people
01:10:51 that probably have egos got together
01:10:54 and were collaborate together and countries,
01:10:57 I guess, collaborate together for the funds
01:11:00 and everything’s just collaboration everywhere.
01:11:03 Cause you may be, I don’t know what the right question here
01:11:07 to ask, but almost what’s your intuition
01:11:09 about how it was possible to make this happen
01:11:11 and what are the lessons we should learn
01:11:14 for the future of human civilization
01:11:16 in terms of our scientific progress?
01:11:17 Cause it seems like this is a great, great illustration
01:11:21 of us working together to do something big.
01:11:24 Yeah, I think it’s possibly the best example.
01:11:27 Maybe I can think of international collaboration
01:11:30 that isn’t for some unpleasant purpose, basically.
01:11:33 You know, I mean, so when I started out in the field
01:11:37 in 2008 as a new PhD student,
01:11:39 the LHC was basically finished.
01:11:41 So I didn’t have to go around asking for money for it
01:11:44 or trying to make the case.
01:11:45 So I have huge admiration for the people who managed that.
01:11:48 Cause this was a project that was first imagined
01:11:51 in the 1970s, in the late 70s
01:11:53 was when the first conversations about the LHC were mooted
01:11:56 and it took two and a half decades of campaigning
01:12:00 and fundraising and persuasion
01:12:03 until they started breaking ground
01:12:05 and building the thing in the early noughties in 2000.
01:12:08 So, I mean, I think the reason just from a sort of,
01:12:11 from the point of view of the sort of science,
01:12:13 the scientists there,
01:12:14 I think the reason it works ultimately
01:12:16 is that everywhere, everyone there is there
01:12:19 for the same reason, which is, well, in principle, at least
01:12:23 they’re there because they’re interested in the world.
01:12:25 They want to find out, you know,
01:12:27 what are the basic ingredients of our universe?
01:12:29 What are the laws of nature?
01:12:31 And so everyone is pulling in the same direction.
01:12:32 Now, of course, everyone has their own
01:12:34 things they’re interested in.
01:12:35 Everyone has their own careers to consider.
01:12:37 And, you know, I wouldn’t pretend that
01:12:38 there isn’t also a lot of competition.
01:12:40 So there’s this funny thing in these experiments
01:12:42 where your collaborators,
01:12:43 your 800 collaborators in LHCb,
01:12:46 but you’re also competitors
01:12:47 because your academics in your various universities
01:12:49 and you want to be the one that gets the paper out
01:12:51 on the most exciting, you know, new measurements.
01:12:53 So there’s this funny thing where you’re kind of trying
01:12:55 to stake out your territory while also collaborating
01:12:58 and having to work together to make the experiments work.
01:13:00 And it does work amazingly well,
01:13:03 actually considering all of that.
01:13:05 And I think there was actually,
01:13:06 I think McKinsey or one of these big management
01:13:08 consultancy firms went into CERN maybe a decade or so ago
01:13:11 to try to understand how these organizations function.
01:13:15 Did they figure it out?
01:13:16 I don’t think they could.
01:13:16 I mean, I think one of the things that’s interesting,
01:13:18 one of the other interesting things
01:13:19 about these experiments is, you know,
01:13:21 they’re big operations like say Atlas has 3000 people.
01:13:24 Now there was a person nominally
01:13:26 who was the head of Atlas, they’re called the spokesperson.
01:13:29 And the spokesperson is elected by,
01:13:32 usually by the collaboration,
01:13:34 but they have no actual power really.
01:13:36 I mean, they can’t fire anyone.
01:13:38 They’re not anyone’s boss.
01:13:39 So, you know, my boss is a professor at Cambridge,
01:13:43 not the head of my experiments.
01:13:45 The head of my experiment can’t tell me what to do really.
01:13:47 And there’s all these independent academics
01:13:50 who are their own bosses who, you know,
01:13:52 so that somehow it, nonetheless,
01:13:54 by kind of consensus and discussion and lots of meetings,
01:13:58 these things do happen and it does get done, but.
01:14:01 It’s like the queen here in the UK is the spokesperson.
01:14:04 I guess so.
01:14:05 No actual power. Except we don’t elect her, no.
01:14:07 No, we don’t elect her.
01:14:08 But everybody seems to love her.
01:14:10 I don’t know, from my outside perspective.
01:14:16 But yeah, giant egos, brilliant people.
01:14:19 And moving forward, do you think there’s.
01:14:22 Actually, I would pick up one thing you said just there,
01:14:24 just the brilliant people thing.
01:14:25 Cause I’m not saying that people aren’t great.
01:14:28 But I think there is this sort of impression
01:14:30 that physicists all have to be brilliant or geniuses,
01:14:32 which is not true actually.
01:14:34 And you know, you have to be relatively bright for sure.
01:14:37 But you know, a lot of people,
01:14:39 a lot of the most successful experimental physicists
01:14:41 are not necessarily the people with the biggest brains.
01:14:43 They’re the people who, you know,
01:14:45 particularly one of the skills that’s most important
01:14:47 in particle physics is the ability to work
01:14:49 with others and to collaborate and exchange ideas
01:14:51 and also to work hard.
01:14:52 And it’s a sort of, often it’s more a determination
01:14:55 or a sort of other set of skills.
01:14:57 It’s not just being, you know, kind of some great brain.
01:15:01 Very true.
01:15:02 So, I mean, there’s parallels to that
01:15:04 in the machine learning world.
01:15:05 If you wanna solve any real world problems,
01:15:08 which I see as the particle accelerators,
01:15:11 essentially a real world instantiation
01:15:14 of theoretical physics.
01:15:16 And for that, you have to not necessarily be brilliant,
01:15:20 but be sort of obsessed, systematic, rigorous,
01:15:26 sort of unborable, stubborn, all those kind of qualities
01:15:29 that make for a great engineer.
01:15:31 So, scientists purely speaking,
01:15:34 that practitioner of the scientific method.
01:15:36 So you’re right.
01:15:37 But nevertheless, to me that’s brilliant.
01:15:39 My dad’s a physicist.
01:15:41 I argue with him all the time.
01:15:43 To me, engineering is the highest form of science.
01:15:46 And he thinks that’s all nonsense,
01:15:48 that the real work is done by the theoretician.
01:15:50 So, in fact, we have arguments about like people
01:15:54 like Elon Musk, for example,
01:15:56 because I think his work is quite brilliant,
01:15:58 but he’s fundamentally not coming up
01:16:00 with any serious breakthroughs.
01:16:02 He’s just creating in this world, implementing,
01:16:07 like making ideas happen that have a huge impact.
01:16:09 To me, that’s the Edison.
01:16:12 That to me is a brilliant work,
01:16:17 but to him, it’s messy details
01:16:22 that somebody will figure out anyway.
01:16:25 I mean, I don’t know whether you think
01:16:26 there is a actual difference in temperament
01:16:29 between say a physicist and an engineer,
01:16:31 whether it’s just what you got interested in.
01:16:33 I don’t know.
01:16:34 I mean, a lot of what experimental physicists do
01:16:37 is to some extent engineering.
01:16:40 I mean, it’s not what I do.
01:16:40 I mostly do data stuff,
01:16:42 but a lot of people would be called electrical engineers,
01:16:45 but they trained as physicists,
01:16:46 but they learned electrical engineering, for example,
01:16:48 because they were building detectors.
01:16:50 So, there’s not such a clear divide, I think.
01:16:52 Yeah, it’s interesting.
01:16:53 I mean, but there does seem to be,
01:16:55 like you work with data.
01:16:57 There does seem to be a certain,
01:16:59 like I love data collection.
01:17:01 There might be an OCD element or something
01:17:03 that you’re more naturally predisposed to
01:17:06 as opposed to theory.
01:17:07 Like I’m not afraid of data.
01:17:08 I love data.
01:17:10 And there’s a lot of people in machine learning
01:17:11 who are more like,
01:17:14 they’re basically afraid of data collection,
01:17:16 afraid of data sets, afraid of all of that.
01:17:18 They just want to stay in more than theoretical
01:17:20 and they’re really good at it, space.
01:17:22 So, I don’t know if that’s the genetic,
01:17:24 that’s your upbringing, the way you go to school,
01:17:28 but looking into the future of LHC and other colliders.
01:17:33 So, there’s in America,
01:17:35 there’s whatever it was called, the super,
01:17:37 there’s a lot of super.
01:17:38 Superconducting super colliders.
01:17:39 Yeah, superconducting.
01:17:40 The desertron, yeah.
01:17:41 Desertron, yeah.
01:17:43 So, that was canceled, the construction of that.
01:17:45 Yeah.
01:17:48 Which is a sad thing,
01:17:50 but what do you think is the future of these efforts?
01:17:54 Will a bigger collider be built?
01:17:56 Will LHC be expanded?
01:17:58 What do you think?
01:17:59 Well, in the near future, the LHC is gonna get an upgrade.
01:18:03 So, that’s pretty much confirmed.
01:18:04 I think it is confirmed, which is,
01:18:07 it’s not an energy upgrade.
01:18:08 It’s what we call a luminosity upgrade.
01:18:10 So, it basically means increasing
01:18:11 the data collection rates.
01:18:13 So, more collisions per second, basically,
01:18:15 because after a few years of data taking,
01:18:18 you get this law of diminishing returns
01:18:19 where each year’s worth of data
01:18:20 is a smaller and smaller fraction
01:18:21 of the lot you’ve already got.
01:18:23 So, to get a real improvement in sensitivity,
01:18:25 you need to increase the data rate
01:18:27 by an order of magnitude.
01:18:28 So, that’s what this upgrade is gonna do.
01:18:30 LHCb, at the moment, the whole detector
01:18:32 is basically being rebuilt to allow it to record data
01:18:36 at a much larger rate than we could before.
01:18:38 So, that will make us sensitive
01:18:39 to whole loads of new processes
01:18:40 that we weren’t able to study before.
01:18:42 And I mentioned briefly these anomalies that we’ve seen.
01:18:45 So, we’ve seen a bunch of very intriguing anomalies
01:18:49 in these b quark decays,
01:18:52 which may be hinting at the first signs
01:18:55 of this kind of the elephant,
01:18:57 the signs of some new quantum field
01:18:59 or fields maybe beyond the standard model.
01:19:01 It’s not yet at the statistical threshold
01:19:02 where you can say that you’ve observed something,
01:19:06 but there’s lots of anomalies in many measurements
01:19:08 that all seem to be consistent with each other.
01:19:11 So, it’s quite interesting.
01:19:12 So, the upgrade will allow us
01:19:13 to really home in on these things
01:19:15 and see whether these anomalies are real,
01:19:17 because if they are real,
01:19:19 and this kind of connects to your point
01:19:20 about the next generation of machines,
01:19:23 what we would have seen then is,
01:19:26 we would have seen the tail end of some quantum field
01:19:29 in influencing these b quarks.
01:19:31 What we then need to do is to build a bigger collider
01:19:34 to actually make the particle of that field.
01:19:37 So, if these things really do exist.
01:19:40 So, that would be one argument.
01:19:41 I mean, so at the moment,
01:19:42 Europe is going through this process
01:19:44 of thinking about the strategy for the future.
01:19:47 So, there are a number of different proposals on the table.
01:19:49 One is for a sort of higher energy upgrade of the LHC,
01:19:53 where you just build more powerful magnets
01:19:55 and put them in the same tunnel.
01:19:56 That’s a sort of cheaper, less ambitious possibility.
01:19:59 Most people don’t really like it
01:20:00 because it’s sort of a bit of a dead end,
01:20:02 because once you’ve done that, there’s nowhere to go.
01:20:05 There’s a machine called Click,
01:20:06 which is a compact linear collider,
01:20:08 which is a electron positron collider
01:20:10 that uses a novel type of acceleration technology
01:20:13 to accelerate at shorter distances.
01:20:15 We’re still talking kilometers long,
01:20:17 but not like 100 kilometers long.
01:20:19 And then probably the project that is,
01:20:22 I think getting the most support,
01:20:23 it’d be interesting to see what happens,
01:20:25 something called the Future Circular Collider,
01:20:28 which is a really ambitious longterm multi decade project
01:20:32 to build a 100 kilometer circumference tunnel
01:20:35 under the Geneva region.
01:20:38 The LHC would become a kind of feeding machine.
01:20:40 It would just feed.
01:20:41 So the same area, so it would be a feeder for the.
01:20:44 Yeah.
01:20:44 So it would kind of, the edge of this machine
01:20:46 would be where the LHC is,
01:20:47 but it would sort of go under Lake Geneva
01:20:49 and round to the Alps, basically,
01:20:51 up to the edge of the Geneva basin.
01:20:52 So it’s basically the biggest tunnel you can fit
01:20:55 in the region based on the geology.
01:20:57 100 kilometers.
01:20:58 Yeah, so it’s big.
01:20:58 It’d be a long drive if your experiment’s on one side.
01:21:01 You’ve got to go back to CERN for lunch,
01:21:03 so that would be a pain.
01:21:04 But you know, so this project is,
01:21:07 in principle, it’s actually two accelerators.
01:21:09 The first thing you would do
01:21:09 is put an electron positron machine
01:21:11 in the 100 kilometer tunnel to study the Higgs.
01:21:14 So you’d make lots of Higgs bows
01:21:15 and study it really precisely
01:21:16 in the hope that you see it misbehaving
01:21:18 and doing something it’s not supposed to.
01:21:20 And then in the much longer term,
01:21:22 100, that machine gets taken out,
01:21:24 you put in a proton proton machine.
01:21:26 So it’s like the LHC, but much bigger.
01:21:29 And that’s the way you start going
01:21:30 and looking for dark matter,
01:21:32 or you’re trying to recreate this phase transition
01:21:35 that I talked about in the early universe,
01:21:37 where you can see matter anti matter being made,
01:21:39 for example.
01:21:40 There’s lots of things you can do with these machines.
01:21:41 The problem is that they will take,
01:21:43 you know, the most optimistic,
01:21:45 you’re not gonna have any data
01:21:46 from any of these machines until 2040,
01:21:49 or, you know, because they take such a long time to build
01:21:51 and they’re so expensive.
01:21:52 So you have, there’ll be a process of R&D design,
01:21:55 but also the political case being made.
01:21:57 So LHC, what costs a few billion?
01:22:01 Depends how you count it.
01:22:03 I think most of the sort of more reasonable estimates
01:22:05 that take everything into account properly,
01:22:07 it’s around the sort of 10, 11, 12 billion euro mark.
01:22:10 What would be the future, sorry,
01:22:12 I forgot the name already.
01:22:13 Future Circular Collider.
01:22:14 Future Circular Collider.
01:22:15 Presumably they won’t call it that when it’s built,
01:22:16 cause it won’t be the future anymore.
01:22:18 But I don’t know, I don’t know what they’ll call it then.
01:22:20 The very big Hadron Collider, I don’t know.
01:22:25 But that will, now I should know the numbers,
01:22:28 but I think the whole project is estimated
01:22:31 at about 30 billion euros,
01:22:32 but that’s money spent over between now and 2070 probably,
01:22:37 which is when the last bit of it
01:22:39 would be sort of finishing up, I guess.
01:22:42 So you’re talking a half a century of science
01:22:46 coming out of this thing, shared by many countries.
01:22:48 So the actual cost, the arguments that are made
01:22:51 is that you could make this project fit
01:22:53 within the existing budget of CERN,
01:22:56 if you didn’t do anything else.
01:22:57 And CERN, by the way, we didn’t mention, what is CERN?
01:23:00 CERN is the European Organization for Nuclear Research.
01:23:03 It’s an international organization
01:23:05 that was established in the 1950s
01:23:07 in the wake of the second world war as a kind of,
01:23:10 it was sort of like a scientific Marshall plan for Europe.
01:23:12 The idea was that you bring European science back together
01:23:16 for peaceful purposes,
01:23:17 because what happened in the forties was,
01:23:20 a lot of particular Jewish scientists,
01:23:21 but a lot of scientists from central Europe
01:23:22 had fled to the United States
01:23:25 and Europe had sort of seen this brain drain.
01:23:27 So there was a desire to bring the community back together
01:23:29 for a project that wasn’t building nasty bombs,
01:23:32 but was doing something that was curiosity driven.
01:23:34 So, and that has continued since then.
01:23:37 So it’s kind of a unique organization.
01:23:38 It’s you, to be a member as a country,
01:23:41 you sort of sign up as a member
01:23:43 and then you have to pay a fraction of your GDP
01:23:45 each year as a subscription.
01:23:47 I mean, it’s a very small fraction, relatively speaking.
01:23:49 I think it’s like, I think the UK’s contribution
01:23:51 is a hundred or 200 million quid or something like that.
01:23:54 Yeah, which is quite a lot, but not so.
01:23:57 That’s fascinating.
01:23:58 I mean, just the whole thing that is possible,
01:24:00 it’s beautiful.
01:24:01 It’s a beautiful idea,
01:24:02 especially when there’s no wars on the line,
01:24:05 it’s not like we’re freaking out,
01:24:06 as we’re actually legitimately collaborating
01:24:08 to do good science.
01:24:09 One of the things I don’t think we really mentioned
01:24:11 is on the final side, that sort of the data analysis side,
01:24:15 is there breakthroughs possible there
01:24:17 and the machine learning side,
01:24:18 like is there a lot more signal to be mined
01:24:22 in more effective ways from the actual raw data?
01:24:25 Yeah, a lot of people are looking into that.
01:24:27 I mean, so I use machine learning in my data analysis,
01:24:31 but pretty naughty, basic stuff,
01:24:33 cause I’m not a machine learning expert.
01:24:35 I’m just a physicist who had to learn to do this stuff
01:24:37 for my day job.
01:24:38 So what a lot of people do is they use
01:24:40 kind of off the shelf packages
01:24:42 that you can train to do signal noise.
01:24:46 Just clean up all the data.
01:24:48 But one of the big challenges,
01:24:50 the big challenge of the data is A, it’s volume,
01:24:52 there’s huge amounts of data.
01:24:53 So the LHC generates, now, okay,
01:24:56 I try to remember what the actual numbers are,
01:24:57 but if you, we don’t record all our data,
01:24:59 we record a tiny fraction of the data.
01:25:02 It’s like of order one 10,000th or something, I think.
01:25:04 Is that right?
01:25:05 Around that.
01:25:07 So most of it gets thrown away.
01:25:08 You couldn’t record all the LHC data
01:25:10 cause it would fill up every computer in the world
01:25:11 in a matter of days, basically.
01:25:13 So there’s this process that happens on live,
01:25:17 on the detector, something called a trigger,
01:25:18 which in real time, 40 million times every second
01:25:21 has to make a decision about whether this collision
01:25:23 is likely to contain an interesting object,
01:25:26 like a Higgs boson or a dark matter particle.
01:25:28 And it has to do that very fast.
01:25:29 And the software algorithms in the past
01:25:33 were quite relatively basic.
01:25:36 They did things like measure mementos
01:25:37 and energies of particles and put some requirements.
01:25:40 So you would say, if there’s a particle
01:25:42 with an energy above some threshold,
01:25:43 then record this collision.
01:25:44 But if there isn’t, don’t.
01:25:46 Whereas now the attempt is get more and more
01:25:47 machine learning in at the earliest possible stage.
01:25:51 That’s cool, at the stage of deciding
01:25:53 whether we want to keep this data or not.
01:25:55 But also maybe even lower down than that,
01:25:57 which is the point where there’s this,
01:26:01 so generally how the data is reconstructed
01:26:02 is you start off with a set of digital hits
01:26:06 in your detector.
01:26:07 So channels saying, did you see something?
01:26:08 Did you not see something?
01:26:10 That has to be then turned into tracks,
01:26:12 particles going in different directions.
01:26:14 And that’s done by using fits
01:26:15 that fit through the data points.
01:26:17 And then that’s passed to the algorithms
01:26:18 that then go, is this interesting or not?
01:26:20 What’d be better is you could train machine learning
01:26:22 to just look at the raw hits,
01:26:24 the basic real base level information,
01:26:26 not have any of the reconstruction done.
01:26:28 And it just goes, and it can learn to do pattern recognition
01:26:31 on this strange three dimensional image that you get.
01:26:34 And potentially that’s where you could get really big gains
01:26:36 because our triggers tend to be quite inefficient
01:26:38 because they don’t have time to do
01:26:41 the full whiz bang processing
01:26:43 to get all the information out that we would like,
01:26:45 because you have to do the decision very quickly.
01:26:46 So if you can come up with some clever
01:26:48 machine learning technique,
01:26:50 then potentially you can massively increase
01:26:52 the amount of useful data you record
01:26:54 and get rid of more of the background
01:26:58 earlier in the process.
01:26:59 Yeah, to me, that’s an exciting possibility
01:27:01 because then you don’t have to build a sort of,
01:27:04 you can get a gain without having to.
01:27:08 Without having to build any hardware, I suppose.
01:27:10 Hardware, yeah.
01:27:11 Although you need lots of new GPU farms, I guess.
01:27:13 So hardware still helps.
01:27:15 But I got to talk to you,
01:27:20 sort of I’m not sure how to ask,
01:27:22 but you’re clearly an incredible science communicator.
01:27:27 I don’t know if that’s the right term,
01:27:29 but you’re basically a younger Neil deGrasse Tyson
01:27:32 with a British accent.
01:27:33 So, and you’ve, I mean,
01:27:36 can you say where we are today, actually?
01:27:39 Yeah, so today we’re in the Royal Institution in London,
01:27:42 which is a very old organization.
01:27:45 It’s been around for about 200 years now, I think.
01:27:47 Maybe even I should know when it was founded.
01:27:49 Sort of early 19th century,
01:27:51 it was set up to basically communicate science to the public.
01:27:55 So it was one of the first places in the world
01:27:57 where famous scientists would come and give talks.
01:28:01 So very famously Humphrey Davy, who you may know of,
01:28:05 who was the person who discovered nitrous oxide.
01:28:07 He was a very famous chemist and scientist.
01:28:11 Also discovered electrolysis.
01:28:12 So he used to do these fantastic,
01:28:13 he was a very charismatic speaker.
01:28:15 So he used to appear here.
01:28:15 There’s a big desk that they usually have in the theater
01:28:18 and he would do demonstrations to the sort of the,
01:28:21 the folk of London back in the early 19th century.
01:28:23 And Michael Faraday, who I talked about,
01:28:25 who is the person who did so much work on electromagnetism,
01:28:27 he used, he lectured here.
01:28:28 He also did experiments in the basement.
01:28:29 So this place has got a long history
01:28:31 of both scientific research,
01:28:33 but also communication of scientific research.
01:28:35 So you gave a few lectures here.
01:28:38 How many, two?
01:28:39 I’ve given, yeah, I’ve given a couple of lectures
01:28:41 in this theater before, so.
01:28:42 I mean, that’s, so people should definitely go watch online.
01:28:46 It’s just the explanation of particle physics.
01:28:48 So all the, I mean, it’s incredible.
01:28:50 Like your lectures are just incredible.
01:28:53 I can’t sing it enough praise.
01:28:54 So it was awesome.
01:28:55 But maybe can you say, what did that feel like?
01:29:00 What does it feel like to lecture here, to talk about that?
01:29:03 And maybe from a different perspective,
01:29:06 more kind of like how the sausage is made is,
01:29:09 how do you prepare for that kind of thing?
01:29:12 How do you think about communication,
01:29:14 the process of communicating these ideas
01:29:16 in a way that’s inspiring to,
01:29:18 what I would say your talks are inspiring
01:29:21 to like the general audience.
01:29:22 You don’t actually have to be a scientist.
01:29:25 You can still be inspired without really knowing much of the,
01:29:28 you start from the very basics.
01:29:30 So what’s the preparation process?
01:29:33 And then the romantic question is,
01:29:34 what did that feel like to perform here?
01:29:38 I mean, profession, yeah.
01:29:39 I mean, the process, I mean, the talk,
01:29:42 my favorite talk that I gave here
01:29:43 was one called Beyond the Higgs,
01:29:44 which you can find on the Royal Institute’s YouTube channel,
01:29:46 which you should go and check out.
01:29:48 I mean, and their channel’s got loads of great talks
01:29:50 with loads of great people as well.
01:29:52 I mean, that one, I’d sort of given a version of it
01:29:55 many times, so part of it is just practice, right?
01:29:57 And actually, I don’t have some great theory
01:29:59 of how to communicate with people.
01:30:00 It’s more just that I’m really interested
01:30:02 and excited by those ideas and I like talking about them.
01:30:05 And through the process of doing that,
01:30:07 I guess I figured out stories that work
01:30:09 and explanations that work.
01:30:10 When you say practice, you mean legitimately
01:30:12 just giving talks? Just giving talks, yeah.
01:30:14 I started off when I was a PhD student
01:30:17 doing talks in schools and I still do that as well
01:30:20 some of the time and doing things,
01:30:21 I’ve even done a bit of standup comedy,
01:30:23 which sort of went reasonably well,
01:30:25 even if it was terrifying.
01:30:26 And that’s on YouTube as well.
01:30:27 That’s also on, I wouldn’t necessarily recommend
01:30:29 you check that out.
01:30:30 I’m gonna post the links several places
01:30:33 to make sure people click on it.
01:30:35 But it’s basically, I kind of have a story in my head
01:30:37 and I kind of, I have to think about what I wanna say.
01:30:41 I usually have some images to support what I’m saying
01:30:43 and I get up and do it.
01:30:44 And it’s not really, I wish there was some kind of,
01:30:47 I probably should have some proper process.
01:30:48 This is very sounds like I’m just making up as I go along
01:30:50 and I sort of am.
01:30:52 Well, I think the fundamental thing that you said,
01:30:54 I think it’s like, I don’t know if you know
01:30:58 who a guy named Joe Rogan is.
01:31:01 Yes, I do.
01:31:02 So he’s also kind of sounds like you in a sense
01:31:05 that he’s not very introspective about his process,
01:31:08 but he’s an incredibly engaging conversationalist.
01:31:13 And I think one of the things that you and him share
01:31:15 that I could see is like a genuine curiosity
01:31:19 and passion for the topic.
01:31:22 I think that could be systematically cultivated.
01:31:26 I’m sure there’s a process to it,
01:31:28 but you come to it naturally somehow.
01:31:30 I think maybe there’s something else as well,
01:31:31 which is to understand something.
01:31:34 There’s this quote by Feynman, which I really like,
01:31:35 which is what I cannot create, I do not understand.
01:31:38 So I’m not particularly super bright.
01:31:43 So for me to understand something,
01:31:44 I have to break it down into its simplest elements.
01:31:47 And if I can then tell people about that,
01:31:49 that helps me understand it as well.
01:31:51 So I’ve learned to understand physics a lot more
01:31:55 from the process of communicating,
01:31:57 because it forces you to really scrutinize the ideas
01:32:00 that you’re communicating and it often makes you realize
01:32:02 you don’t really understand the ideas you’re talking about.
01:32:06 And I’m writing a book at the moment,
01:32:08 and I had this experience yesterday where I realized
01:32:09 I didn’t really understand a pretty fundamental
01:32:12 theoretical aspect of my own subject.
01:32:14 And I had to go and I had to sort of spend
01:32:15 a couple of days reading textbooks and thinking about it
01:32:18 in order to make sure that the explanation I gave
01:32:21 captured the, got as close to what is actually happening
01:32:24 in the theory.
01:32:26 And to do that, you have to really understand it properly.
01:32:29 Yeah, and there’s layers to understanding.
01:32:31 It seems like the more,
01:32:33 there must be some kind of Feynman law.
01:32:35 I mean, the more you understand sort of the simpler
01:32:39 you’re able to really convey the essence of the idea, right?
01:32:46 So it’s like this reverse effect that it’s like
01:32:52 the more you understand, the simpler the final thing
01:32:54 that you actually convey.
01:32:56 And so the more accessible somehow it becomes.
01:32:58 That’s why Feynman’s lectures are really accessible.
01:33:03 It was just counterintuitive.
01:33:04 Yeah, although there are some ideas
01:33:06 that are very difficult to explain
01:33:09 no matter how well or badly you understand them.
01:33:12 Like I still can’t really properly explain
01:33:15 the Higgs mechanism.
01:33:16 Yeah.
01:33:17 Because some of these ideas only exist
01:33:19 in mathematics really.
01:33:21 And the only way to really develop an understanding
01:33:24 is to go unfortunately to a graduate degree in physics.
01:33:29 But you can get kind of a flavor of what’s happening,
01:33:31 I think, and it’s trying to do that in a way
01:33:33 that isn’t misleading, but always also intelligible.
01:33:36 So let me ask them the romantic question of
01:33:39 what to you is the most, perhaps an unfair question,
01:33:44 what is the most beautiful idea in physics?
01:33:49 One that fills you with awe is the most surprising,
01:33:52 the strangest, the weirdest.
01:33:54 There’s a lot of different definitions of beauty.
01:33:57 And I’m sure there’s several for you,
01:33:59 but is there something that just jumps to mind
01:34:01 that you think is just especially beautiful?
01:34:07 There’s a specific thing and a more general thing.
01:34:08 So maybe the specific thing first,
01:34:10 which I can now first came across as an undergraduate.
01:34:12 I found this amazing.
01:34:13 So this idea that the forces of nature,
01:34:17 electromagnetism, strong force, the weak force,
01:34:19 they arise in our theories as a consequence of symmetries.
01:34:24 So symmetries in the laws of nature,
01:34:27 in the equations essentially
01:34:29 that used to describe these ideas,
01:34:32 the process whereby theories come up
01:34:34 with these sorts of models is they say,
01:34:36 imagine the universe obeys this particular type of symmetry.
01:34:39 It’s a symmetry that isn’t so far removed
01:34:42 from a geometrical symmetry, like the rotations of a cube.
01:34:44 It’s not, you can’t think of it quite that way,
01:34:46 but it’s sort of a similar sort of idea.
01:34:49 And you say, okay, if the universe respects the symmetry,
01:34:51 you find that you have to introduce a force
01:34:54 which has the properties of electromagnetism
01:34:57 or a different symmetry, you get the strong force
01:35:00 or a different symmetry, you get the weak force.
01:35:01 So these interactions seem to come from some deeper,
01:35:05 it suggests that they come
01:35:06 from some deeper symmetry principle.
01:35:07 I mean, it depends a bit how you look at it
01:35:09 because it could be that we’re actually
01:35:10 just recognizing symmetries in the things that we see,
01:35:12 but there’s something rather lovely about that.
01:35:15 But I mean, I suppose a bigger thing that makes me wonder
01:35:17 is actually, if you look at the laws of nature,
01:35:20 how particles interact when you get really close down,
01:35:22 they’re basically pretty simple things.
01:35:24 They bounce off each other by exchanging
01:35:26 through force fields and they move around
01:35:27 in very simple ways.
01:35:29 And somehow these basic ingredients,
01:35:31 these few particles that we know about in the forces
01:35:34 creates this universe, which is unbelievably complicated
01:35:37 and has things like you and me in it,
01:35:39 and the earth and stars that make matter in their cores
01:35:43 from the gravitational energy of their own bulk
01:35:46 that then gets sprayed into the universe
01:35:47 that forms other things.
01:35:48 I mean, the fact that there’s this incredibly long story
01:35:52 that goes right back to the beginning,
01:35:55 and we can take this story right back to a trillionth
01:35:58 of a second after the Big Bang,
01:35:59 and we can trace the origins of the stuff
01:36:01 that we’re made from.
01:36:02 And it all ultimately comes from these simple ingredients
01:36:05 with these simple rules.
01:36:06 And the fact you can generate such complexity from that
01:36:08 is really mysterious, I think, and strange.
01:36:11 And it’s not even a question that physicists
01:36:12 can really tackle because we are sort of trying
01:36:15 to find these really elementary laws.
01:36:19 But it turns out that going from elementary laws
01:36:21 and a few particles to something even as complicated
01:36:24 as a molecule becomes very difficult.
01:36:26 So going from a molecule to a human being
01:36:28 is a problem that just can’t be tackled,
01:36:31 at least not at the moment, so.
01:36:34 Yeah, the emergence of complexity from simple rules
01:36:37 is so beautiful and so mysterious.
01:36:40 And we don’t have good mathematics
01:36:43 to even try to approach that emergent phenomena.
01:36:47 That’s why we have chemistry and biology
01:36:48 and all the other subjects, yeah, okay.
01:36:52 I don’t think there’s a better way to end it, Harry.
01:36:55 I can’t, I mean, I think I speak for a lot of people
01:36:59 that can’t wait to see what happens
01:37:01 in the next five, 10, 20 years with you.
01:37:03 I think you’re one of the great communicators of our time.
01:37:06 So I hope you continue that and I hope that grows.
01:37:09 And I’m definitely a huge fan.
01:37:12 So it was an honor to talk to you today.
01:37:13 Thanks so much, man.
01:37:14 It was really fun, thanks very much.
01:37:16 Thanks for listening to this conversation with Harry Kliff.
01:37:19 And thank you to our sponsors, ExpressVPN
01:37:22 and Cash App.
01:37:23 Please consider supporting the podcast
01:37:25 by getting ExpressVPN at expressvpn.com slash lexpod
01:37:29 and downloading Cash App and using code lexpodcast.
01:37:34 If you enjoy this podcast, subscribe on YouTube,
01:37:36 review it with five stars on Apple Podcast,
01:37:39 support it on Patreon or simply connect with me
01:37:41 on Twitter at lexfreedman.
01:37:45 And now let me leave you with some words from Harry Kliff.
01:37:48 You and I are leftovers.
01:37:51 Every particle in our bodies is a survivor
01:37:53 from an almighty shootout between matter and antimatter
01:37:57 that happened a little after the Big Bang.
01:37:59 In fact, only one in a billion particles created
01:38:02 at the beginning of time have survived to the present day.
01:38:06 Thank you for listening and hope to see you next time.