Music. I've made quite a few videos about particle accelerators and why we use the ones that we do. But there is one thing that I haven't mentioned, and it's really pretty cool. That is just exactly how we accelerate particles. And if you make it to the end, I'll let you know why physicists are at least as cool as surfers. I've talked about how we make electric fields to push electrically charged particles around, and that's right to a degree. In the simplest case, we could take two metal plates and connect them to a battery. That creates an electric field between the plates. That electric field can then push an object that carries an electric charge. But that simplified picture isn't how we really do it. It turns out that the electric field in most high-energy particle accelerators isn't static like that. In fact, the electric field in a particle accelerator is actually oscillating. It starts out as zero, then pushes a charged particle in one direction, then pushes it in the opposite direction. The pattern repeats itself over and over and over again. So why do we do it that way, and what consequences are there for that choice? Well, why we do that is perhaps the easiest thing to explain. It's just hard to make very strong static electric fields without a spark occurring. It can be done, but there's an easier way. And it turns out to be pretty cool. Instead, we shoot radio waves into a volume in our accelerator. We call that volume a cavity, and its exact shape and size are very important. We'll get back to that in a minute. Now you may recall that radio waves are just oscillating electromagnetic fields. Focusing only on the electric side, we get an electric field...