Einstein’s Contribution to Quantum Theory

Abstract

If new features of the phenomena of nature are discovered that are incompatible with the system of theories assumed at that time, the question arises, which of the known principles used in the description of nature are general enough to comprehend the new situation and which have to be modified or abandoned. The attitude of different physicists on problems of this kind, which makes strong demands on the intuition and tact of a scientist, depends to a large extent on the personal temperament of the investigator. In the case of Planck’s discovery in 1900 of the quantum of action during the course of his famous investigations of the law of the black-body radiation, it was clear that the law of the conservation of energy and momentum and Boltzmann’s principle connecting entropy and probability, were two pillars sufficiently strong to stand unshaken by the development resulting from the new discovery. It was indeed the faithfulness to these principles which enabled Planck to introduce the new constant h, the quantum of action, into his statistical theory of the thermodynamic equilibrium of radiation.

First published in P. A. Schilpp: Albert Einstein: Philosopher Scientist. The Library of Living Philosophers, volume 7. Evanston, I11. 1949, pp. 149–160. The present version is translated from the German edition, Albert Einstein als Philosoph und Naturforscher, ed. P.A. Schilpp, Stuttgart (1955), pp. 74–84, which is believed to be Pauli’s original wording.