One of the reasons I find physics so enthralling is that it brings scientists closer to a theory of everything than any other subject. When I say a “theory of everything”, you might think of the hit movie starring Eddie Redmayne but this isn’t quite what I mean: I mean a theory which explains what everything humans observed ever seen is made of.
Just like biologists will marvel that a human and a banana share 60% of their genes, physicists can similarly be fascinated by the fact that all matter is made of different arrangements and repetitions of 118 different atoms. Though, over the last century, physicists have been able to peer inside atoms to discover more fundamental building blocks. This can be concisely represented in a periodic table-esque diagram: Ladies and gentlemen, let me introduce you to the Standard Model.
You may be familiar with at least 1 particle in this chart: the electron. Discovered by J.J. Thompson in 1897, most of you will know that these particles orbit nucleons ( protons and neutrons ) and have a mass roughly 1/1836 that of a nucleon. Protons and neutrons themselves are composed out of particles called quarks. A proton is made up of two up quarks and a down quark and a neutron is made from two down quarks and an up quark: these are both elementary particles found in the top left corner of the Standard Model table.
The last particle in the first row is what is known an electron neutrino. These are electrically neutral and minuscule particles which theoretically should have 0 mass yet Kajita and McDonald won the 2015 Physics Nobel Prize by disproving this. You have know understood what is known as the first generation of matter
For some reason, unbeknown to scientists, nature replicated these 4 particles two times ( represented by the second and third columns ). The second generation is comprised of particles which are exactly the same as the particles in the first generation yet these are more massive and more unstable. Since these particles are unstable, they are most often generated in high energy collisions at particle accelerators such as the Large Hadron Collider. The third generation particles are identical to those in the second generation apart from being more massive.
That’s it. These 12 particles are the fundamental building blocks of all matter in existence. Elegant, isn’t it ? One could say that Physicists arrived at this model by applying Occam’s razor to Mendeleev’s 118 element period table. Everything humans have known or seen was known to have been made up of approximately 100 different atoms and now we know that all matter is composed of 12 more fundamental building blocks.
Incredible.
The last ingredients of the standard model are the force particles. One of these particles may be familiar to you as it transmits the electromagnetic force and is responsible for all chemical reactions: the photon ( the particle of light ). Next, we have the gluon which is the force particle of the strong nuclear force, a force which binds quarks together within protons and neutrons. Lastly, the Z and W particles transmit another fundamental force of nature, the weak nuclear force. Unlike the strong nuclear or electromagnetic force, the weak force doesn’t bind particles together but rather causes them to decay.
Until 3rd July 2012, these 16 particles were understood to make up all matter in existence across the entire universe. What is so special about 3rd July 2012, you ask ? It was on this tremendous day that a particle theorised in the 1960s was empirically proven to exist; the Higgs particle.
The theory for the Higgs boson arose from the nonsensical answers arrived at by physicists when large masses were assigned to W and Z particles, particles which transmit the weak nuclear force. The solution to these discrepancies was to invent another particle which, if it exists, provides evidence that a field gave W and Z particles, as well as all other particles in existence, mass when the field interacted with them. To be clear, the Higgs particle doesn’t give mass to all particles but it does prove the existence of the Higgs field which, once interacted with, is responsible for giving particles mass.
I hope to further explore this concept of “fields” in a later article.
The inspiration for this post was this superb and highly insightful lecture by Harry Cliff on the Standard Model, the discovery of the Higgs boson and experiments at the LHC. I would highly recommend to watch and learn from this very insightful journey into particle physics.
Beyond Science 