Explain spin in a featurless particle.

[emcelhannon]

Is spin just a substitute for an unknowable quality in elementary particles? I just assume color is. How is spin possible in something fundamental. Are there actual surface features on or around a particle that literally rotate around it?

[ajb]

It should not be thought of in terms of something rotating, like angular momentum. It is an intrinsic property of fundamental particles as well as composites. It is really a consequence of Lorentz symmetry and is very natural in special relativity. In non-relativistic quantum theory it is simply "bolted-on" to the theory to reflect empirical evidence.

 

To understand spin properly one needs to think about representations of the Lorentz group. Do you know a little group theory?

[emcelhannon]

Not yet, but give me a week. Thanks for the response. That's just the kind of information I was looking for.