What do Charge, Color, and Flavor have in common? -- Fundamental Interactions

To our knowledge there are four fundamental forces of nature. Electromagnetism, Strong Nuclear, Weak Nuclear, and Gravitational. All the processes we observe in nature are combinations of these four ways that fundamental particles interact.

Electromagnetism is the force we all know and love which forms the basis of much of our modern technology. The messenger of the Electromagnetic force is the photon (particles of light!), and a particle communicates with the Electromagnetic field through its electric charge.

The Strong Force is responsible for holding together quarks inside of hadrons like protons and neutrons. The messenger of the Strong force is the gluon (there are actually eight different kinds of gluons!), and a particle communicates with the Strong field through its color (another quantum number associated to each particle).

The Weak Force is responsible for the radioactive decay of subatomic particles. The messengers of the Weak Force are the W and Z bosons, and a particle communicates with the Weak field through its flavor – which is a way of describing its quark and lepton content.

Fundamentally speaking, there is a deep commonality in the operation of the Electromagnetic, Strong, and Weak forces. Each force is a dialogue between particles about one of their quantum numbers, or attributes, mediated by a messenger particle. To summarize:

Noticeably absent from this party is the Gravitational Force, which, as a matter of fact, is quite regrettably absent from the Standard Model entirely. This, my friends, is perhaps the deepest question currently nagging at Theoretical Physicists, and, to that end, deserves its own explanation in a later article – stay tuned!

In order to conceptualize the interactions between fundamental particles, Physicists use a visual device known as a Feynman Diagram. Feynman Diagrams are an infinitely fascinating and integral part of High Energy Physics and, as such, should also get their own article! For the time being, here are the Feynman Diagrams for the three fundamental interactions of the Standard Model:

The Electromagnetic Interaction:

Recipe -- Initial State: Electron + Electron. Final State: Electron + Electron. Messenger Particle: Photon. Quantum Number: Electric Charge.

The Strong Interaction:

Recipe -- Initial State: Quark + Quark. Final State: Quark + Quark. Messenger Particle: Gluon. Quantum Number: Color..

The Weak Interaction:

Recipe -- Initial State: Neutron = Up + Down + Down. Final State: Electron + Electron Neutrino + Proton = Up + Up + Down. Messenger Particle: W Boson. Quantum Number: Flavor Charge.