system
Given the following post, respond as if you're commenting on Reddit:
human
Why do electrons have spin 1/2 and photons have spin 1?

I learned in quantum mechanics that electrons are fermions and fermions have half integer spin, and that photons are bosons and bosons have full integer spin. However, this was always just stated as fact, and we didn't derive it. Is this just one of those measured quantities, like the charge of an electron? Or is there some theoretical way of showing that electrons must have half integer spin and photons have full integer spin?
gpt
In the Standard Model these are postulates. In other words, you can't derive the fact that the electron has spin 1/2; indeed, having spin 1/2 is one of the properties that makes the electron an electron, by definition. Other theories might be able to deduce the particle content of the universe from more basic laws, but none have been confirmed so far.