Question: How does thinking about the coldest things in the universe help you to unravel the weirdest forces in nature?

Steven Thomson answered on 14 Jun 2015:

Great question!

Cold things are interesting to think about because heat is the natural enemy of quantum mechanics, and it’s quantum mechanics that leads to what I think are the weirdest bits of physics. So if we want to learn about these weird forces, we’ve got to get rid of heat!

Heat comes from the random movement of particles – the warmer the temperature, the faster the particles are moving. At high temperatures, particles are just zooming around all over the place and it’s too hard to understand what they’re doing or where they’re going. If we make things really cold, as cold as it’s possible to go, the all the particles we want to study slow right down. All the movement from heat disappears, and all that’s left is movement due to quantum mechanics alone. We can learn about quantum physics by watching what the really cold particles do!

So by making stuff really cold, we make understanding quantum physics simpler for ourselves!