The Conceptual Completion and the Extensions of Quantum Mechanics (1932–1941)

Abstract

The invention of quantum and wave mechanics and the great, if not complete, progress achieved by these theories in describing atomic, molecular, solid-state and—to some extent—nuclear phenomena, established a domain of microphysics in addition to the previously existing macrophysics. To the latter domain of classical theories created since the 17th century applied—principally, the mechanics of Newton and his successors, and the electrodynamics of Maxwell, Hertz, Lorentz, and Einstein. The statistical mechanics of Maxwell, Boltzmann, Gibbs, Einstein, and others indicated a transition to microphysics; when applied to explain the behaviour of atomic and molecular ensembles, it exhibited serious limitations of the classical approach. Classical theories were closely connected with a continuous description of matter and the local causality of physical processes. The microscopic phenomena exhibited discontinuities, ‘quantum’ features, which demanded changes from the classical description.