Since the particles aren’t rotating, but just traveling in a straight line, there should be no angular momentum whatsoever. Since the magnetic moment of magnetic dipoles can be theoretically represented as coming from a loop of electric current, or particle orbiting, thus magnetic moments are related to orbital angular momentum. Now, the Stern-Gerlach experiment sees a deflection of the beam, where deflection should only be due to orbital angular momentum, therefore we infer the existence of an intrinsic (spin) angular momentum. First question: is this correct? Then we observe a quantization of spin angular momentum, i.e. only discrete possibilities of deflection angles. But how can we say that this is in contrast with orbital angular momentum (as the latter normally gives a continuum of angles), given that we assume there is no orbital momentum in this experiment? Thanks!