What are Feynman diagrams, how are they used (theoretically & practically), and are there alternative/competing diagrams to Feynman’s?
Physicist: Feynman diagrams are primarily a way to keep track of what you’re doing. Physicists aren’t geniuses or anything, and they get distracted pretty easily. When you’re trying to calculate the probability of a particular particle interaction you’ll find yourself integrating over (adding up) every possible position and momentum of every involved particle. Moreover, when there are several different ways that you can get a particular result you need to keep track of all the different ways that the result can happen. Feynman diagrams are not technically necessary, but they do help you keep track of variables and permutations. It turns out that particle physics is a lot more complicated than you’d think. That holds true even if you think it’s really, really complicated. Feynman diagrams were created alongside the field of quantum electrodynamics and (as far as I know) no one has suggested another diagram system (if it ain’t broke…). They allow you to write down the important integrals
