Professor Jon Butterworth
Jon Butterworth is Particle Physics Professor at University College London. He is a member of the High Energy Physics Group on the ATLAS Experiment at the Large Hadron Collider at CERN and worked on the discovery of the Higgs Boson. He also writes a regular popular science column for the Guardian newspaper in the UK.
It’s an odd concept that something that is not made of anything else actually has mass because it has no internal structure.
On your earliest memories of science
I think the first one I can think of, me and my little brother and a friend of ours got into space and stars, I think that starts a lot of people off, and we decided we would write a book about everything there was to know about the solar system and planets and stars, I think I was about nine, my brother was about six. And we quite quickly got to the point where we realised we were never going to do this, not because there was too much known already because – arrogance of youth – we could deal with that, we were going to be around forever anyway, but because the amount that was getting known was growing faster than we could possibly write it down, and that was a really good moment, that was when we actually realised that science was an ongoing process of exploration and that we were exploring so fast that by the time we’d finished the book it would already be out of date. So we gave up on the book but I didn’t give up on science.
On what a particle physicist does
My research is on high energy particle physics which is really studying the smallest things we’re aware of in the universe. So if you take a piece of matter and break it up into small bits you get atoms, and you get nuclei, and you break them up and you get protons and neutrons and then you break them up you get quarks and, basically, trying to break quarks is what I do. So it’s really the fundamental particles and forces, fundamentally in the sense that we know they’re not made of anything else, they’re what everything else is made of.
On the history of particle physics
I might get some of the history wrong but the key facts are that it’s all tied in with the development of quantum mechanics. You see that atoms will typically emit and absorb light, only particular frequencies, and this is a real puzzle and the solution that people came up with, not only led us to, there must be structure inside the atom and therefore the atom is not the fundamental particle, it’s made up of stuff. It has an internal life of its own but then it also becomes the electron going around the nucleus, and the Bohr Atom is the first realistic picture of an atom where the really weird thing is the electrons only have particular orbits that they can go on and it’s when they jump between two particular orbits they emit or absorb light of a particular energy. And this was very odd, and in the end that led to quantum mechanics because those loud orbits are not really orbits because what they are loud frequencies, the electron behaves like a wave, as with a guitar string you’ve only got certain harmonics you can have, the electrons only fit around an atom in certain modes, vibrational modes, when you put light in or get light out with a laser or whatever, or the lights that we’re using now even, you have to move between specific harmonics, you can’t just do it continuously. And that’s quantum mechanics, that’s the birth of quantum mechanics, so the understanding that atoms were not really, that there was an internal structure to atoms, that they were made of other things is very closely tied to the realisation that actually nature, when you get to those scales, is very weird and is actually quantum rather than the classical continuum that physicists were happy with until then.
On the work being done at the LHC
The LHC (Large Hadron Collider) is a huge project. It’s taken many years, many years of my life and thousands of other people too, and it collides protons together, it’s that simple, it’s what it does. We get the highest particle beams we’ve ever had in a lab and we collide them together. In fact it’s more useful to think of it as colliding quarks and gluons together because that’s what’s inside the proton. So it’s doing that. Now that’s always a good idea at some level if you’re into understanding nature of the smallest scale because with the highest energies you essentially have the highest frequency probes of what’s going on, so if you want to see something, you need a probe that has a wave length that is of the same size or smaller than the thing you want to see. With radar you can see aeroplanes and boats but I couldn’t see you if my eyes were sensitive to radar so we have hundreds of nanometre. Optical light, that is what we are sensitive to, if you want to see finer detail, you need higher energy protons which are shorter frequency, so you need X-rays for instance, electrons have got even shorter frequencies so electron microscopes can see very small distances. What we’re doing is using gluons and quarks to probe each other at really short distances, the shortest distances ever seen, and that means the highest energies ever so, in general, going in high energies is the way to look at nature at a short distance scales.
The LHC is more special than that though, it’s not just exploring the highest energies ever, there’s good reason to know that this energy is special and that’s because we’ve measured two of the fundamental forces in nature: the electromagnetismand the weak nuclear force which is basically what makes the sun work. We know that those two forces unify at the energies where the LHC gets us to, and we can do physics above this energy scale where they unify and we know even more than that, even before we built the experiment we knew the reason they unify is because the force carriers of the weak force, the W and the Z boson, have mass and the photon has no mass so they unify at this energy and the reason they unify is because above that energy there is effectively no mass and below that energy the W and Z pick up mass and the photon doesn’t. This is a very special energy scale now in nature that we’re studying, not only are two forces unified but actually this is to do with the origin of mass, this is where mass comes from, and this is the mass of things that are not made of anything. So it’s an odd concept that something that is not made of anything else actually has mass because it has no internal structure.
And the model, the theory, the Standard Model of particle physics solves that conundrum by introducing the field that fills the whole universe, which you probably shouldn’t call the Higgs Field because there are other people involved in inventing it, but the evidence of whether that field is there or not is to make a ripple in it and that ripple is a boson and you an certainly call it the Higgs Boson because that was in Peter Higgs’ paper and that’s what we seem to have found.
On the problems people have with physics
It’s different for different people but I think one of the big problems is that the mystical side of physics tends to get the attention: if you’re not a professional physicist, then you’ll encounter black holes and string theory and the Higgs Boson, which is all very advanced stuff, the cutting edge of physics if you like, and you’ll encounter that before you’ll encounter and understand Archimedes’ principle and Newton’s laws and things and so it’s hard to relate to everyday life, and it becomes, the chain of, there is a chain of evidence and deduction that takes you from an apple falling on the ground to quantum gravity and string theory, or at least it takes us to general relativity. It may not take us to quantum gravity yet, but at least that takes us to the cutting edge, but it’s very hard to make that connection if you’ve never really understood the physics of the everyday world around you. I really think that understanding things like, why does water stay in a bucket when I whirl it round my head, that’s beautiful physics, and that’s what made me, er, that’s why I got into physics, was not to understand the which-ness of what, in the end you want to understand how the universe works and that is the driving force, but it was the fact that it could help me understand weird things in everyday life thats first got me into it and that of course leads you to weird things in the universe, weird things inside the atom, but its starts with everyday life for me, and I think that that connection isn’t made often enough. To me it’s the connection between maths and the everyday world actually that does it and I had a maths teacher called Mr Vernon, that was another of my turning points in science if you like; we were doing differentiation and he made us measure the gradient of a graph, by drawing a tangent and a triangle and calculating it like an experimentalist on graph paper, and then he, and then we were getting answers that were roughly right, and then he said actually, we know the equation of this curve, if you can differentiate it you’ll get exactly the right answer without making a single measurement and I thought that was amazing, so I went and tried to understand differentiation and it’s that application of some simple rules that you devise experimentally but they explain much more than the thing you’ve actually learnt them from because they’re another line principle. So that’s what does it for me and I think that often, we get to, people encounter the physics that we’re confused and puzzled by which isn’t a bad thing, it’s good that people know physics is not finished, erm, but I think it would also be good if people saw the beautiful physics underlying some of the stuff in everyday life which it really does and maybe that should be put across more often and people should encounter that at least as often as they encounter Hawking radiationround a black hole somewhere out in the middle of the universe.
On everyday physics
Connections between the edge of physics and everyday phenomena happen all over the place and one of the ones I like best is why is the LHC so big? Why have we got 27km of tunnel? Why don’t we do it here? Why don’t we just build it in my office? And the reason is centripetal force, it’s actually Newton’s law in the end, and it’s the same reason that cars skid when you go round a corner too fast, it’s the same reason water stays in a bucket when you whirl it round your head, it’s because things want to go on in a straight line, so the water is not glued to the bucket, it’s trying to go in a straight line, and you keep pulling it round with your arm, so it’s being pushed up against the bucket and similarly a car wants to go in a straight line and if it’s rainy it will carry on in a straight line whatever you do with the steering wheel because Newton’s law just tells you that momentum is conserved, well it’s conserved anyway, and it will stay constant unless you act with a force, and that means momentum being conserved; it just means things carry on at the same speed in the same direction so the protons in the LHC want to carry on at the same speed in the same direction, they want to do that, if you don’t mind my anthropomorphising protons, they want to do that more than any particle we’ve ever had in the lab, they’re the highest momentum particles we’ve ever had anywhere so they really want to go in a straight line, so if you bend them it has to be a very gentle bend and a very powerful magnet and a small bend means a huge radius of curvature, that’s why the machine has to be 27km round and it’s also why it’s packed with some of the strongest magnets in the world to bend those protons but it’s the same physics that keeps the water in the bucket.
On how to entice people into physics
I don’t think there’s one way that works for everyone. The two places I would start, one is with this amazing correspondence between the natural universe that we can observe and the ideas of mathematics which at some level live in our heads; where does maths come from? But yet there’s this amazing correspondence between mathematical techniques that you can apply, for a particle physicist, the fact that symmetry seems to be so intimately tied up with the way the universe works, where all the fundamental forces come from. That’s a very particle physicist way of doing it but you could do it also in any science, there are mathematical concepts which seem to be borne out again and again in nature, and maths and nature obviously don’t have anything to do with each other. So it’s teaching simple tricks that will allow you to make accurate predictions of stuff that is going on around you, it’s really amazing and physics does that par excellence. I think there’s a lot of good, fairly detailed stuff you can find now on the internet, books that will take you a long way to understanding that. I do think sometimes it’s a little bit daunting to start on that, and I even feel that when it’s an area that’s not my own area, it’s a bit of a commitment to start even a very good popular science book, and I think, er, there’s a lot of room for little nuggets of stuff that you could write, I mean it’s why I write a blog, I think you can put in 500 words and put some nice ideas together, and there are books that do that which I think are very good, you can read them on the toilet, you can leave them in the bathroom and you pick them up and you learn something interesting from a chapter – that doesn’t build you a body of knowledge but it can drag you in, it can lead you in. For me that works very well, I’m a very lazy reader. I like to read short things but if I read a short thing and I think that was interesting then I might go and read the longer book later and really find out what was going on there. So I’m a great believer in meeting people where you find them and for me that’s on the loo very often.