Viewing the hidden world of particles

A simple table-top device known as a 'cloud chamber' can be used to see beyond our everyday world
12 October 2021

Interview with 

Tina Potter, University of Cambridge


Abstract art depicting showers of particles.


This week’s topic is about the tiniest things in the universe that nevertheless have a massive impact upon us all; and yet, despite trillions of them coursing through our bodies right now, we all remain oblivious. So how do we know it’s even happening? Because we can see some of them with a gadget called a cloud chamber - a bath of extremely cold alcohol fumes in which, periodically, as particles arriving from space and elsewhere stream through, mysterious plumes and trails like shooting stars appear. Cambridge University physicist Tina Potter showed Cameron Voisey one in action...

Cameron - I'm looking at this big box and looking through a glass pane into this sort of black surface. On top, there are these wisps constantly changing, these white wisps, and some are super long and straight, some are very bendy, they curve here and there, even forming like U shapes or V's. And there's a crisscrossing and zigzagging all over the place. Tina, what am I looking at?

Tina - We have a fog there, essentially, a very cold fog. And when a particle travels across that fog, it disturbs it. You can think about it like a motorbike traveling through fog. It leaves this sort of disturbed path. So what you're looking at is the result of unstable nuclei inside the air. And what happens is those nuclei are unstable and they kick out a fragment of themselves or turn into something else. And those are electrons or positrons.

Cameron - So are these particles actually always around us?

Tina - Absolutely. They are all around you. You are radioactive as well. You are emitting a lot of these, but thank goodness, your skin is actually pretty good protection against the most damaging ones, and everything else your body has evolved to live alongside some of these radioactive decays. And the particles that come out, of course, are very, very important for things like gene mutations that are responsible for evolution and things like that. So actually particles and radiation are a fact of our world and are actually very beautiful, and necessary.


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