In classical electrodynamics, the motion of the magnetic dipole moment of an electron is governed by the Bloch equation. We investigate the transition from classical physics to the space-independent Schrödinger–Pauli equation for electron spin. Most notably, Feynman used the path integral to attain the same equation. generalized the Hamilton–Jacobi equation to reach the Schrödinger equation.
Various approaches to obtaining the time-dependent Schrödinger equation have been investigated. The transition from classical physics to quantum mechanics, however, remains a mystery. The Schrödinger equation, as a postulate, is a corner stone in quantum mechanics.
