Lights! Camera! Matter?

Lights! Camera! Matter? Wait, what? Yes, that's right - we can now get matter from light. The Large Hadron Collider (LHC) has the ability to transform matter into energy and then back into different forms of matter. Even cooler, on rare occasions, the Large Hadron Collider can skip the first step and collide pure energy. In 2019, the "A Toroidal LHC Apparatus" (ATLAS) experiment at the LHC observed two photons (aka particles of light) hitting each other and producing two new photons. Last year this was taken a step further and researchers discovered photons merging and transforming into something even more interesting: W bosons (particles that carry the weak force which governs nuclear decay). Yeah, we know that was a lot of jargon, so in short: light particles banged against each other until researchers got something a bit more solid. In other words, this research confirms the central concept governing processes inside the LHC: that energy and matter are two sides of the same coin. 

So how exactly does this work? We can tell you that it isn't as simple as shining two flashlights together and is certainly not a "try this at home DIY" sort of project. Let's go back to physics and take a look at Maxwell's equations for classical electromagnetism. According to Maxwell, you'll see that two colliding waves sum up to a bigger wave (ie: two flashlight lights make bigger light). What was recently observed by ATLAS happens when Maxwell's equations are combined with special relativity and quantum mechanics in the theory of quantum electrodynamics.

It is also important to note that the generation of W bosons from high-energy photons shows that at extremely high energies, electromagnetism and the weak force are one in the same. Electricity and magnetism often feel like separate forces; you're not going to plug a magnet into the wall and you are not thinking about electromagnetism resulting from your power lines on a day to day basis. Your cellphone isn't going to stick to the refrigerator door by itself, even if you plug it in. You may be thinking that you've never even seen magnetism and electricity mentioned in the same breath, but you would be wrong. Have you ever noticed that there are warnings on electrical stations about their high magnetic fields? That is because a magnet is one manifestation of electromagnetism, and electricity is another. We see this unification in our everyday lives of magnets and electricity, for example, cell phones communicate through electromagnetic waves and must be charged with electricity to run.

At extremely high energies, electromagnetism combines with the weak force. The weak force governs nuclear reactions, including the fusion of hydrogen into helium that powers the sun and the decay of radioactive atoms. So, just as photons carry the electromagnetic force, W and Z bosons carry the weak force. The reason photons can collide and produce W bosons in the LHC is that at the highest energies, those forces combine to make the electroweak force. Sounds good, right?