132 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



corpuscles is associated with a certain periodic phenomenon called a 

 wave. 



According to physicists, this generalized hypothesis to account for 

 light and matter by wave mechanics explains all the recent experiments 

 which the older physics failed to explain. But it makes a great 

 mystery of physics; in a memoire, written in collaboration by Maurice 

 de Broglie and Louis de Broglie, we read that the photon is a corpuscle 

 of light whose nature remains very mysterious: Wave mechanics 

 associates with motion "the consideration of a wave, without physical 

 reality, but which can be predicted." 8 



In any case, in the new physics, to the idea of the unity of matter 

 and of the interchangeability of energy and matter, it is necessary to 

 add the idea that, for light and for matter, one must always "consider 

 both the corpuscular aspect and the wave aspect, bound together by 

 the same general relations"; 9 we come thus to the "unitarian theory 

 of matter and of light"; Louis de Broglie obtains this unity by the 

 hypothesis that the neutrino, the last born of the constituent particles 

 of matter, a corpuscle as small as or smaller than the electron and 

 having "zero or at least a negligible charge in comparison with that 

 of an electron," may be one of two constituents of the photon, the 

 other being another corpuscle; he calls the neutrino a demiphoton; 10 

 but if the neutrino has a "physical entity" the photon becomes a 

 material corpuscle and not simply a corpuscle of immaterial light. 



We perceive, by these simple indications, to what extent the new 

 physics is still mysterious and how it tends toward unity. It gives 

 at times the impression that all material reality, in the older sense of 

 the word, has disappeared and in its place there is substituted that 

 which one might call a unique substance having corpuscular atomic 

 form and possessing interchangeable attributes of mass and of energy. 

 It seems to lead thus to a kind of materialistic "monism," outside of 

 which the mysteries of life and of mind exist. 



In short, the new physics is distinguished from the old in that it 

 adopts conceptions which destroy the rigorous and universal determin- 

 ism of mechanics and the principle of continuity. 



Atomic physics, it tells us, shows a discontinuous reality, with 

 abrupt transitions, which can only be explained "by the artifice of 

 waves associated" with the motions of corpuscles. The introduction 

 into physics, says Louis de Broglie, about 1900, by Planck, of the 

 quantum of action and of the constant "h" is the origin of the change 

 of view; let us then analyze each of these two new ideas. 



The "quanta" of Planck can be roughly explained by indicating 

 that the radiation of atoms is not continuous; apparently the energy 



8 Matiere et lumiere, pp. 69 and 60. 

 • Matiere et lumiere, p. 147. 

 » Op. cit., p. 153 and following. 



