The Spin

Abstract

It is shown that the spin is naturally introduced into classical mechanics if the latter is formulated as dynamics of the phase space density. It is shown that the uncertainty principle, as the amendment in this dynamics, restricts possible spins, and in particular equation for the particle with the spin $\hbar /2$ is derived. Also equation for the charge with this spin is derived when electromagnetic field is included. In one example it is shown that the modulus of the spin changes with the gradient of the magnetic field.