It has been estimated that there are 7.5 million undiscovered species of animals, plants and fungi. Most of these species are insects. If someone wanted billions of dollars to search the Amazon rainforest with the goal of cataloging every species of insect, you’d want them to have a pretty good reason. Maybe they are searching for genes that could cure diseases, or trying to understand why an ecosystem is dying.
The primary goal of the Large Hadron Collider is to search for new subatomic particles. If we’re spending billions searching for these things, they must have some use, right? After all, it’s all well and good knowing about a bunch of different particles, but there must be a whole lot of sorts of particles out there, at least if you judge by science fiction (these two are also relevant). Surely we could just focus on finding the useful ones, and ignore the rest?
The thing is, particle physics isn’t like that. Particles aren’t like insects, you don’t find rare new types scattered in out-of-the-way locations. That’s because each type of particle isn’t like a species of animal. Instead, each particle is a fundamental law of nature.
It wasn’t always like this. In the late 50’s and early 60’s, particle accelerators were producing a zoo of new particles with no clear rhyme or reason, and it looked like they would just keep producing more. That impression changed when Murray Gell-Mann proposed his Eightfold Way, which led to the development of the quark model. He explained the mess of new particles in terms of a few fundamental particles, the quarks, which made up the more complicated particles that were being discovered.
Nowadays, the particles that we’re trying to discover aren’t, for the most part, the zoo of particles of yesteryear. Instead, we’re looking for new fundamental particles.
What makes a particle fundamental?
The new particles of the early 60’s were a direct consequence of the existence of quarks. Once you understood how quarks worked, you could calculate the properties of all of the new particles, and even predict ones that hadn’t been found yet.
By contrast, fundamental particles aren’t based on any other particles, and you can’t predict everything about them. When we discover a new fundamental particle like the Higgs boson, we’re discovering a new, independent law of nature. Each fundamental particle is a law that states, across all of space and time, “if this happens, make this particle”. It’s a law that holds true always and everywhere, regardless of how often the particle is actually produced.
Think about the laws of physics like the cockpit of a plane. In front of the pilot is a whole mess of controls, dials and switches and buttons. Some of those controls are used every flight, some much more rarely. There are probably buttons on that plane that have never been used. But if a single button is out of order, the plane can’t take off.
Each fundamental particle is like a button on that plane. Some turn “on” all the time, while some only turn “on” in special circumstances. But each button is there all the same, and if you’re missing one, your theory is incomplete. It may agree with experiments now, but eventually you’re going to run into problems of one sort or another that make your theory inconsistent.
The point of discovering new particles isn’t just to find the one that will give us time travel or let us blow up Vulcan. Technological applications would be nice, but the real point is deeper: we want to know how reality works, and for every new fundamental particle we discover, we’ve found out a fact that’s true about the whole universe.