WAVE-THEORY OF MATTER 201 



turn; and the extension of a quantum in space has no 

 real meaning. To apply these conceptions to a single 

 quantum is like reading the Riot Act to one man. A 

 single quantum has not travelled 50 billion miles from 

 Sirius; it has not been 8 years on the way. But when 

 enough quanta are gathered to form a quorum there 

 will be found among them statistical properties which 

 are the genesis of the 50 billion miles' distance of Sirius 

 and the 8 years' journey of the light. 



Wave-Theory of Matter. It is comparatively easy to 

 realise what we have got to do. It is much more diffi- 

 cult to start to do it. Before we review the attempts 

 in the last year or two to grapple with this problem we 

 shall briefly consider a less drastic method of progress 

 initiated by De Broglie. For the moment we shall be 

 content to accept the mystery as a mystery. Light, we 

 will say, is an entity with the wave property of spread- 

 ing out to fill the largest object glass and with all the 

 well-known properties of diffraction and interference; 

 simultaneously it is an entity with the corpuscular or 

 bullet property of expending its whole energy on one 

 very small target. We can scarcely describe such an 

 entity as a wave or as a particle; perhaps as a com- 

 promise we had better call it a "wavicle". 



There is nothing new under the sun, and this latest. 

 volte-face almost brings us back to Newton's theory of 

 light — a curious mixture of corpuscular and wave-theory. 

 There is perhaps a pleasing sentiment in this "return 

 to Newton". But to suppose that Newton's scientific 

 reputation is especially vindicated by De Broglie's 

 theory of light, is as absurd as to suppose that it is 

 shattered by Einstein's theory of gravitation. There 

 was no phenomenon known to Newton which could not 



