Question: how does looking at protons help you to understand the universe better?

Flavia de Almeida Dias answered on 10 Nov 2015:

Hello!

What we do is not necessarily looking at the protons, but smashing the protons together at very very high energies and seeing what comes out of it. And that makes us see how the universe used to be at the time when it was very hot and much smaller, a fraction of time just after the Big Bang! Let me elaborate on that.

We think, given our current understanding of the astronomical and physics data, that the universe had a start, and that start is what we call the Big Bang. The energy was all concentrated in a tiny tiny piece of space, and when the Bang! happened, the universe started to expand, and the energy which was enclosed in the tiny space started to spread out into the now bigger and bigger universe. When the energy is spread out into a bigger space, it starts to cool down – and then when it gets cold enough, particles and molecules are able to form. Nowadays our universe is infinitely big, and quite cold – in fact only about 2 degrees warmer than the coldest temperature which is physically defined (which we call absolute zero, about -273 Celsius).

What we do at the LHC is trying to reproduce some of the conditions we had at the universe at very early stages – we smash protons together at very high energy (and therefore temperature) in a tiny space, and that creates enough energy density which looks more like our young universe than our current one. This makes enough energy available to produce heavy and unstable particles, which then transform (what we call a decay) into lighter and more stable particles, which are the ones we are more used to – such as electrons, and quarks (which make up the protons and neutrons, which make up atoms).
And that’s how we can produce in the lab and discover new particles which we haven’t seen lying around before!

Comment on this answer if you have follow up questions or want to know more details 🙂