The Origin and Development of the Quantum Theory Translated.

Excerpt from The Origin and Development of the Quantum Theory

Moreover, my suggestion that the resonator might be able to exert a one-sided, i. E. Irreversible, action on the energy of the surrounding radiation field called forth the emphatic protest of Ludwig Boltzmann who with his more mature experience in these questions succeeded in showing that according to the laws of the classical dynamics every one of the processes I was considering could take place in exactly the opposite sense. Thus a spherical wave emitted from a resonator when reversed shrinks in concentric spherical surfaces of continually de creasing size on to the resonator, is absorbed by it, and so permits the resonator to send out again into space the energy formerly absorbed in the direction from which it came. And although I was able to exclude such singular processes as inwardly directed spherical waves by the introduction of a special restriction, to wit the hypothesis of natural radiation yet in the course of these investiga tions it became more and more evident that in the chain of argument an essential link was missing which should lead to the comprehension of the nature of the entire question.

Planck, Institute for Physics, Munich.