When a particle is said to have "spin," does that mean it actually spins or is it simply an arbitrary label of a property like "charm"?

When a particle is said to have "spin," does that mean it actually spins or is it simply an arbitrary label of a property like "charm"?

 

 

No, it's is not physically spinning, and no, this is not arbitrary. Spin is angular momentum, as the classical concept suggests, but it is intrinsic to the particle rather than from physical motion.

As swansont says, you should not think of a particle as a tiny spinning ball. The intrinsic spin does not have such a simple interpretation, but it is similar to angular momentum when you take special relativity into account - you could look up the Pauli–Lubanski pseudovector.

 

The usual way to include spin in nonrelativistic quantum mechanics is to simply 'bolt it on' to the theory - you then think of total angular momentum, which is the sum of the orbital angular momentum and the spin.

Interesting. I've got some reading to do on angular momentum, Pauli-Lubanski, etc. Thank you for the answers.