What is the spin of a particle?
A. The elementary particles that constitute matter can be represented as spheres of ultramicroscopic dimensions, with a radius of the order of tenths of millionth of millionth of centimetre, and they can be neutral or with a positive or negative electric charge. Besides exists another property, typical of the microcosm, that differentiates a particle from another: the spin. A particle can have a zero or a non-zero spin, if it is characterized or not by an intrinsic rotation around an its axis; if a particle has an angular momentum is said to have the spin, and behaves as an ultramicroscopic spinning top. Besides, an electrically charged particle as, for example, electron or proton, or a neutral one, as neutron, can be considered, provided it has the spin, as a spinning top containing virtual charged particles that are rotating inside it around its axis, so that the particle is equivalent, because of the Ampere equivalence theorem, to an elementary magnet of microscopic dimensions. The
