216 THE NEW QUANTUM THEORY 



are sometimes slow enough to come within the octave 

 covered by the eye. These beats are the source of the 

 light coming from the hydrogen atom, and mathematical 

 calculation shows that their frequencies are precisely 

 those of the observed light from hydrogen. Hetero- 

 dyning of the radio carrier waves produces sound; 

 heterodyning of the sub-aethereal waves produces light. 

 Not only does this theory give the periods of the dif- 

 ferent lines in the spectra, but it also predicts their in- 

 tensities — a problem which the older quantum theory had 

 no means of tackling. It should, however, be under- 

 stood that the beats are not themselves to be identified 

 with light-waves; they are in the sub-aether, whereas 

 light-waves are in the aether. They provide the oscil- 

 lating source which in some way not yet traced sends out 

 light-waves of its own period. 



What precisely is the entity which we suppose to be 

 oscillating when we speak of the waves in the sub- 

 aether? It is denoted by op, and properly speaking we 

 should regard it as an elementary indefinable of the 

 wave-theory. But can we give it a classical interpreta- 

 tion of any kind? It seems possible to interpret it as a 

 probability. The probability of the particle or electron 

 being within a given region is proportional to the amount 

 of ip in that region. So that if ip is mainly concentrated 

 in one small stormy area, it is practically certain that 

 the electron is there; we are then able to localise it 

 definitely and conceive of it as a classical particle. But 

 the ip-waves of the hydrogen atom are spread about 

 all over the atom; and there is no definite localisation of 

 the electron, though some places are more probable than 

 others.* 



* The probability is often stated to be proportional to ty 2 , instead of 

 \p, as assumed above. The whole interpretation is very obscure, but it 



