In chemistry, we deal with spin to explain why there is a limit to the number of electrons that can occupy an orbital, ie. no two electrons can have the same quantum numbers. We are not required to know much more than that. But I am curious, what is spin? My chemistry book explained an experiment where hydrogen was passed through a magnetic field and half of the atoms were attracted to one side, and the other half where attracted to the other. So does spinning charge induce a magnetic field? Is that why electrons are said to have spin? Also, if that is so, and two electrons with opposing spin occupy the same area, should not they attract each other since that have opposite poles? And why are spin of particles always simple rational numbers, why are there no 3/12344 spins?