BH: Tell us who you are and how you are connected to the CERN project.

David: Sure.  I am a particle theorist, a particle physicist. I received my PhD in 1999. I was an undergraduate at Berkley and a graduate student at the University of Washington and then I did post doctoral research positions, one at University of Chicago and one at Stanford. In 2002, I got a professor faculty job at Johns Hopkins University .

I’ve always loved solving puzzles and this is a job where I can solve puzzles and get paid for it, and teach other people how to solve puzzles. In the world of particle physics, there are people who build the experiments and there are people who develop, understand, and discover theories and they work hand in hand.

The experimentalists are building something based on what theorists think would be interesting to search for, or predict what may be there.  Theorists then attempt to interpret what new physics is discovered in these experiments, especially when it’s unexpected. In detail, you are supposed to carefully discuss as the experiments are being built, what they should cover based on what are the interesting theories.

My whole career, which has been about ten years of really being productive, has been coming up with theories that may explain some of the holes in our current understanding of fundamental laws of nature.

Particle physics is a misnomer; it isn’t the physics of particles. It’s really the study of what the underlying laws are, what the rules are of the game that everything plays by. We understand atoms to an amazing degree, that they make up molecules which make up materials, substances, air, the earth, everything. And we understand to an amazing degree, the basic laws of how those things work, how atoms work. Deep inside the atoms there is access to more fundamental principles about how the world works.

For example, why are atoms allowed to exist in the first place? What give the mass to the electron to allow it to fall into an atom and get stuck there? What allows the proton itself to have a mass, to be heavy, and to be responsible for all mass of all matter? We can ask very deep sounding questions now compared to what we used to be asking, which was, what were things made of? Now we’re really asking, what are the interactions between things and what is the cause of the creation of things, of mass, of matter, of size and structure?

Those questions, as it turns out, can only be answered by going to much higher energy, colliding particles at very high energy and it turns out that at the current, available energy scales that we can approach technologically, we expect a real breakthrough.

BH: Can you do a brief “Particle Physics 101” for us?

David: We call it particle physics because then people won’t balk at us, but really the study is quantum field theory. Quantum field theory is a set of rules, just like quantum mechanics but more complicated that seem to govern nature and are really important at the really smallest distances where you have cosmic rays or, if you ask questions about what gives mass to the electron or what is the structure of the particle and the atom. Those questions are answered by quantum field theory and as far we can tell, there have been no violations of this theory.

The theory says the following: when we talk about a particle like the electron, we think of particles as very hard, solid objects. But electrons can disappear, and a very simple way to make an electron disappear is to collide it with something called a positron which is an anti-electron.

When an electron and an anti-electron collide, they can annihilate each other and literally disappear and what’s left over can be simply radiation or what we would call photons, particles of light.

Even quantum mechanics, and all the other things we know about nature doesn’t actually allow a good description of this process. Quantum mechanics says that we have an electron, we don’t know where it is exactly, it has some fuzzy nature with respect to it, its position is based on probability, and it acts like a wave sometimes, it doesn’t always act like a particle.

Electrons can interfere with each other in the way that waves interfere with each other when you have two waves on the surface of a pond and you throw a rock in one spot and another rock in another spot. The circular waves that come out from the splash may cross through each other and interfere with each other and you can get patterns.

Now if a particle is a wave, when two particles get near each other, they can interfere with each other and that interference is actually different than the way two particles would move past each other. And so at very low energy when they bump off each other, you just have to do a more precise calculation that contains that extra little waviness associated with particles and that waviness is quantum mechanics.

The problem is that when the electrons hit each other at very high energies, if it’s an electron and an anti-electron, they can annihilate each other completely and then it’s not really about the behavior of that electron. It’s the behavior of something more fundamental which allows electrons to appear and disappear and other things to appear in their place. What is the more fundamental object in nature? It’s not solid stuff, it’s not particle, it’s something else. It allows you to change the nature of things at the most fundamental level.

Quantum field theory is the supposition that the fundamental things are fields. They’re not fields in the sense that we’ll feel them, we pass through them like molasses, we’re in stuff that permeates the universe. It says space contains a field and so only certain kinds of objects can live in that space. A particle is a vibration in that field.

So, in the same way that you throw the rock in the lake and see these waves move by, you can look at those waves; the waves exist because the lake exists. You can talk about the waves but the fundamental thing is the lake. These fields are fundamental things, there is an electron field that exists in the universe and you literally have waves in that field. Those waves, while they don’t quite spread out the way they do in the lake, those waves contain energy and in a distance, we say, well that’s a particle, it contains energy.

We are made up of the particles, which means we are made up, in this description, vibrations of these fields. They’re not fundamental, they are just packets of energy and the energy packets are exactly vibrations in fields that we believe are more fundamental particles.

The fields don’t disappear, they’re always there, and they’ve existed from the beginning of time until now. It’s the fluctuations of the fields that change. So for a long time people thought in the beginning of the universe we had stuff, and then as the universe grew and changed in time the stuff in it never changed and actually it turns out that that’s not true.

The stuff now is not the stuff then. The stuff now has the same energy as the stuff then but it’s not made of the same stuff. So now we have a particle, then that energy could have been contained either in the same particle or in a different particle or just in the energy of things moving around.

The fundamental objects of the universe at this point in our knowledge is that there are fields and the fields tell us which particles can and cannot exist and that list of fields then tells us what everything is or could be or could have been or has been in the universe. It gives us a much broader description of the nature of reality.

BH: Why do you need such high energy for these experiments?

David: Well, in some sense, these experiments are about as mundane as you can imagine. Richard Feynman says that particle physics is asking the question how does a Volkswagen work and trying to answer it by taking two Volkswagens and smashing them together as hard as possible and watching the bits of them fly out, and trying to interpret what they were before the two cars crashed.

That’s the best we can do to understand the underlying structure. If we smash it hard enough that the inner part of the carburetor comes flying out and we can see it, in this case in a very crude way, we’re doing the same things. We’re smashing things together so hard that the inner guts of protons or electrons or what look like the fundamental particles of matter produce stuff that we wouldn’t see otherwise because it’s hidden inside these particles.

The only difference is, in a Volkswagen, you could just park it and lift up the hood and use your tools to take it apart. In the case of particles, there are no tools that small because the tools themselves are made of particles that are bigger than those things. The tools are made of atoms. How can you take a knife made of atoms and cut something that is smaller than an atom? It will pass right through it. So just scale-wise, we can’t do it. What makes things better is quantum mechanics lends a veil over extremely small sizes. It makes everything very fuzzy at those scales.

So in some sense that tiny size doesn’t exist. It’s spread out over a blob and so what you do, by hitting things together at extraordinarily high energy, is you have some fractional probability that when they hit, they release the majority of the energy put into that collision. They release it into something that is underlying the nature of that particle. That too, is a very quantum effect.

It’s not literally that a piece of a proton comes out. When the protons collide, it’s enormously high energy. It excited the quantum effects inside of the proton and produces the other underlying stuff that allows the proton to be what it is. It sort of makes up the rules of the proton.

We’re probing all the probabilistic part of the proton. What lives inside there in the sense of what makes the proton work the way it does. Not exactly slicing it up into pieces and looking at the pieces.  It’s all going to sound very vague until we go directly into what quantum field theory is.

BH:  Tell me about CERN.

David: In the ‘50’s, in the aftermath of WWII, when Germany , Austria , England , France , all these countries were rebuilding themselves, people were looking for some real peaceful projects that these countries could do together. A few great scientists recommended the development of a large, cross-European laboratory that only studied basic science, or just basic fundamental understanding, and not for things like weapons research or industry even. Something pure, in a sense, that required real investment, intellectual and monetary investment to be done in a totally peaceful way.

In mid 1954, CERN was established and its location was on the border of Switzerland and France ; France being a NATO country and incorporating Switzerland as a neutral country. This laboratory consisted of 12 member states, which, 10 years earlier were fighting wars with each other and now came together for the sole purpose of really redeeming the name of science - for pure research and pure knowledge in a setting of peaceful trust and cooperation. And so from that time until now, they did basic science research.

In the ‘80’s, they agreed to take on a proposal for an enormously large project which was a collider. They dug a circular tunnel that is almost 17 miles around and they put equipment in there, magnets and other accessories to produce beams of particles. This is just because this is where basic research landed in the ’80’s. Their ability to probe basic laws, or how things work at the really deepest level turned out to require smashing things together at very high energies. To do that, you need really large beams to get them to be accelerated close to the speed of light. In the 80’s, they dug this insanely long tunnel and put these magnets and produced an experiment called LAPC (Large Electron Positron Collider.)

At the time, they had envisioned another collider, which would be even higher energy, called the LHC (Large Hydron Collider) and so that experiment, which is about to turn on this year, has been in development for over 20 years.  Actual construction began in the beginning of the ‘90’s. Now not only are the experiments on a larger scale, but the membership is on a larger scale. CERN now has 20 member states, and well over 100 nationalities that are committed to the experiments. (For a list of the 20 states and non-member states currently involved in CERN programs, click HERE.) So, you not only have all of Europe working and not just Western Europe , but Eastern Europe – old enemies become collaborators- but also the far east, Japan , Korea , India , and even the Middle East . Sworn enemies like Israel and Iran both have Universities with research groups that work on the LHC. Again in the interest of just basic research and pure science.

The scale of the experiment is 8 billion dollars, roughly – give or take 2 billion, nobody actually knows the cost. There are ten thousand people who are building it, although that number is not totally known either. There are physicists of all scales and engineers of all scales; we’re getting help from outside contractors too. There is just an enormous effort being put into it.

When they originally proposed this experiment in the 80’s, the technology didn’t actually exist yet. They proposed it based on the hope that the technology could be developed and that the stronger magnets could be discovered sometime in the future. So there was just a lot of pure research on the experimental side and then of course, the research on the theory side which is the proposal for what we could see and why we are even going to these energies and what it’s going to mean in terms of basic laws of nature.