What is the difference between bosons and fermions?
MARTIN: So, in nature, you only have two kinds of particles, bosons or fermions, and if you want to figure out whether you are a boson or a fermion, just count the number of elementary particles, protons, neutrons, electrons, or equivalently count how much spin you have. If the outcome is, I have an even number of elementary particles, therefore I have an integer spin, well then, I am a boson. Then I can be together with other bosons in the same state. If the outcome is, I have an uneven number of elementary particles or, equivalently, I have a half integer spin, then I am a fermion, and I cannot be together in the same state with another fermion at the same time. That is the difference between bosons and fermions. Turns out, fermions are the building blocks of nature. If you think about it, all massive elementary particles are fermions. We have the quarks, turns out they have half integer spin. The quarks form the protons and the neutrons which have half integer spin because they cons
