130 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 8 



Nevertheless, there is uncertainty regarding the elements of this 

 unity. It was thought until very recently that all atoms could be 

 reduced to a nucleus composed of protons of positive electricity (each 

 proton having a mass 2,000 times greater than an electron) and of 

 electrons of negative electricity; the infinitely small atom appeared 

 to be a sub in miniature with his planet or planets, and matter seemed 

 composed of electrified particles oscillating in space; Thibaut, director 

 of the institute of atomic physics of the University of Lyon, supposes, 

 in order to visualize the atom, that the atom of hydrogen be as big 

 as the whole of Paris; the nucleus would be the size of the Arc de 

 Triomphe, the electron would be represented by a billiard ball situated 

 in the Place de la Concorde and the remainder of the atom would be 

 empty space. 3 



But in these last years, the profound studies of matter from every 

 angle have more and more complicated the problem. Much uncer- 

 tainty exists; in effect man has discovered: First, an electron of posi- 

 tive electricity (called a positron), very difficult to obtain, which 

 scarcely born, seems to unite with other particles; its size is similar 

 to that of the negative electron, of which it is the brother; second, a 

 particle called the neutron, thus named because it is not electrified; 

 it is analogous to the proton in mass (2,000 times that of the electron) 

 and sometimes unites with the nucleus of the atom; third, a fifth 

 mysterious particle called a neutrino, because it is not electrified; it 

 is neutral like the neutron, but with a mass as small as the electron, 

 perhaps even smaller and almost negligible. 



Our impression is that the new physics is still in its infancy. Some 

 physicists conceive of matter as electrified particles surrounded by 

 empty space; Thibaud asks whether the neutron cannot be separated 

 into two corpuscles, one positive and the other negative, and whether 

 the "hypothetical neutrino," as he calls it, would not be the accom- 

 paniment of such a breaking up. 4 Louis de Broglie looks with more 

 favor on the breaking up of the proton into neutron and positive 

 electron. 8 Thus, according to this last authority, the atom and 

 matter are compounded of three elements: neutrons, not electrified, 

 possessing nearly all the mass, negative electrons and positive elec- 

 trons both of very small mass but electrified. 



Nevertheless, the new physics is plainly built upon the idea of the 

 unity of matter. 



3 Physicists and astrophysicists know but little about empty space in the atom or between celestial 

 bodies; they no longer believe in the "ether" of Fresnel. The astronomer Esclangon conceives space not as 

 nothingness but as an entity, furrowed with radiations, composed perhaps of unknown elements which 

 constitute a substratum of matter and radiation, capable of reactions similar to those of matter. 



* Thibaud, Jean, Vie et transmutation des atomes, p. 110, Paris, Albin Michel, 1937. 



• Matiere et lumiere, p. 32. 



