# Particle Physics and the Great Particle Accelerator

FROM THE LECTURE SERIES: THE JOY OF SCIENCE

## Let’s take a look at the great particle accelerators and daunting mathematical theories that are used to tackle the nature of the subatomic world. As physicists probe nature at smaller scales, they have to use higher energies to smash apart their particles, and so they need bigger and bigger machines; these machines are called particle accelerators.

### Particle Physics and Mathematical Relationship

There is an arsenal of mathematical theory that goes with particle physics because you need to understand matter and forces and interpret them as mathematical relationships. Ironically, the mathematics is extremely complex, even though it’s trying to describe the basic physical world around us – just the stuff and substance around us.

Mathematics is almost indecipherable by all but just a few people around the world. They start talking about models in 10 dimensions, or in 26 dimensions, as opposed to the three dimensions of space and the dimension of time, that we experience in our everyday life. This becomes very abstract indeed.

This is a transcript from the video series The Joy of ScienceWatch it now, on Wondrium.

### How Particle Accelerators Work in Physics

The particle accelerators are less abstract; in fact, the concept is quite straightforward. These are machines that employ powerful electromagnetic fields to accelerate particles, and they basically act as bullets, just like in Rutherford’s original experiment that discovered the nucleus.

You have massive detectors that record these collision events, as the atomic bullets, the subatomic bullets, smash into other particles, sending out a spray of particles, including some subatomic beasts.

The earliest of the high-energy physics experiments used the irregular and unpredictable stream of cosmic rays that constantly stream down to the surface of the Earth. To run an experiment like that, you just had to wait around until a cosmic ray hit your experimental apparatus and hope that something interesting would happen.

### Cyclotrons and Synchrotrons: The Great Particle Accelerators

In the 1930s, the first of particle accelerators, machines that control all these high-energy particles, was made. Ernest O. Lawrence invented the first particle accelerator; it was called a cyclotron.

It actually was something you could hold in your hand, and it accelerated electrons to very high speeds, approaching light speeds, in later versions. Once the electrons were up to speed, they were allowed to collide with other particles.

There have been subsequent machines, huge machines, called synchrotrons and linear accelerators; some of these are several kilometers in length. Indeed, the largest of all the synchrotrons was going to be the Superconducting Supercollider. This is a giant accelerator that was being planned and was then canceled by the U.S. Government because of its cost. This machine was in Texas, and it was going to be 85 kilometers around.

### Search for More Massive Particles

As physicists search for more and more massive particles, more ephemeral particles that only come to exist for a tiny fraction of a second and then disappear, they need these larger machines.

You need high energies to make massive particles, according to Einstein’s equation: E=mc2; the energy is proportional to the mass.

For larger masses, to make more massive particles in an accelerator, you need more energy. An electron’s mass is on the order of a million electron-volts; here, electron-volts is a unit of energy that particle physicists use. A proton’s mass is approximately a billion electron volts. Particle accelerators reached tens of billions of volts in the 1950s; they got to hundreds of billions of volts in the 1970s, and then they reached a trillion volts in the 1980s.

Things like the Superconducting Supercollider, and some of the other machines that are now on the books, might reach ten trillion electron-volts to make very massive particles. These are very expensive facilities, and they require huge staff. Indeed, there are some papers that are published in which the list of co-authors is longer than the article itself.

### Discovery of Elementary Particles

Gradually, as particle accelerators became more and more powerful, more elementary particles had been discovered. At one point in the 1960s, there were hundreds of seemingly different elementary particles, each with a different characteristic set of properties: different mass, different electric charge, different spin in a magnetic field, and other different properties.

Making sense of these particles, of course, was very similar to the task that confronted Dmitri Mendeleev 100 years earlier. There couldn’t possibly be hundreds of fundamental particles, so the first step was to look for patterns, distinctive patterns, amongst those particles.

One of the key steps was recognizing that some particles never took part in the atomic nucleus. That is, they always resided outside the nucleus, while other particles always seemed to be associated, in one way or another, with the atom’s nucleus. This is one way of separating particles, at least into two large groups.

### Common Questions about Particle Physics and the Great Particle Accelerator

Q: How do particle accelerators work?

Particle accelerators are machines that employ powerful electromagnetic fields to accelerate particles that basically act as bullets. There are massive detectors that record the collision events, as the atomic bullets, the subatomic bullets, smash into other particles, sending out a spray of particles, including some subatomic beasts.

Q: Who invented the first particle accelerator and when?

Ernest O. Lawrence invented the first particle accelerator, called a cyclotron, in the 1930s.

Q: How can particles be separated in two large groups?

Some particles always reside outside the nucleus, while other particles always seem to be associated, in one way or another, with the atom’s nucleus. This is one way of separating particles into two large groups.