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FAST FACT
It seems like particle accelerators are some of the few things that we keep building bigger and bigger, and not smaller and smaller. And there's a good reason for that: the bigger the accelerator, the faster you can smash particles together, and that's one of the best ways of creating and detecting rare particles.

But now, some scientists are interested in a new type of accelerator: one that could be small enough to fit in a shoebox. It probably wouldn't be smashing particles, at least not in the near future, but it could be incredibly useful for things like medicine and sanitation.

Traditional accelerators like the Large Hadron Collider in Switzerland get particles moving close to the speed of light, and that is no easy task. In these machines, particles travel through a bunch of metal chambers containing electromagnetic fields. As the particle enters each chamber, it gets accelerated by that field.

But the thing is, you can only get so much power from each chamber. If you try to amp up the electromagnetic field too much, the metal chambers will spark. So you can't get bigger kicks. The only way to reach higher speeds is by getting more kicks, which means more chambers and bigger accelerators. That's why accelerators are so enormous today. 

But scientists have known for a while that there might be one shortcut. See, traditional accelerators use radio waves to set up electromagnetic fields in each chamber. But in principle, they could use something more energetic: infrared lasers. Infrared waves are thousands of time shorter than radio waves, so they have much more energy. And they could speed up particles faster over shorter distances. But it's tricky, because the size of the chamber needs to match whatever wavelength is setting up the electromagnetic field. That's important because the way these chambers amp up the energy of these fields is by making the waves resonate, kind of like how the body of a guitar amplifies the sound of a plucked string. The waves will only resonate like that if the chamber is on the same scale as the waves. Radio waves used in traditional accelerators have wavelengths of around a meter, so it's easier to make chambers that are the right size for them. They'd have to be a lot smaller to work with infrared waves. Like, smaller than a human hair. Which is hard to even imagine, but it's actually been done.

In two papers published in 2013, two separate teams of scientists announced that they'd made a tiny accelerator out of glass. In both cases, they did it by carving tiny chambers into the glass, placing it in a vacuum, and shining a laser onto it to set up an electromagnetic field. When electrons were placed at one end, they blew right through a thin tube in the glass. Granted, they moved pretty slowly compared to particles in other accelerators, but the experiment proved a point: you could build a tiny accelerator and use a laser to give particles their kick. Plus, glass doesn't spark the way metal does, so by using glass chambers, you could deliver even more energy with each kick. This suggests that, in principle, you could shrink kilometers of accelerator tunnels down to the size of a room. And less powerful accelerators could even be as small as a shoebox.

Scientists aren't sure if these mini accelerators could ever have the power of the Large Hadron Collider, and they won't be doing things like creating rare particles anytime soon, but they could have other uses. For instance, in some hospitals, surgeons use high-speed electrons to kill cancerous tissue that's hard to remove with a normal scalpel. Getting a refrigerator-sized scanner lined up with a surgical incision is no small feat, but a smaller accelerator could make that easier and more accessible. These tiny accelerators could also be used to blast medical equipment with electrons, which helps kill microbes and keep it super clean.

So you might not have thought that the world needed a shoebox-sized particle accelerator, but these tools have the potential to be cheap, small, and mass-produced in a way that could change our world.

Thanks for watching this episode of SciShow, and if you enjoy videos like this, I bet you would like our podcast. It's called SciShow Tangents. It's a lightly competitive weekly podcast produced by Complexly and WNYC Studios, and it's made by some of the same people who bring you SciShow, including me. It's full of weird science and poetic insights on the world around us, and if you'd like to check it out, you can find it wherever you get your podcasts.

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