Relativistic Invariance of Quantum-Mechanical Equations

Abstract

Relativity Theory, of which we are celebrating the 50th anniversary, and quantum theory, which is about equally old, originated and developed in very different ways. The theory of relativity owes its origin to a set of experimental facts which can be epitomised as the independence of light velocity from the state of motion of emitter and absorber. However, its guiding stars in the course of its development were conceptual problems, problems of the measurement of space and time and of observation. Experimental facts played a relatively subordinate role in the development of relativity theory at least for the last 25 years. Quantum theory, on the contrary, originated as the result of the discussion of a conceptual problem, the inconsistencies in the classical description of black body radiation. However, the guiding stars of quantum theory were experimental facts: the photoelectric effect, the Stern-Gerlach phenomenon, the Bothe-Geiger-Compton-Simon experiments and, before all, the immense amount of detailed information which was accumulated before the war on atomic spectra and is being accumulated now on nuclear forces and ‘elementary particles’. The discovery of much of this information is traceable to the stimulus provided by quantum theory, all of it exerted a profound influence on quantum theory’s development.