Continuity 55 



Hence I hold that here is something 

 with which our own motion may theoreti- 

 cally be compared; and I predict that 

 our motion through the ether will some 

 day be detected by help of this very 

 fact, by comparing our speed with that 

 of light: though the old astronomical 

 aberration, which seemed to make the 

 comparison easy, failed to do so quite 

 simply, because it is complicated by the 

 necessity of observing the position of a 

 distant source, in relation to which the 

 earth is moving. If the source and 

 observer are moving together there is 

 no possibility of observing aberration. 

 Nevertheless I maintain that when mat- 

 ter is moving near a beam of light we 

 may be able to detect the motion. For 

 the velocity of light in space is no func- 

 tion of the velocity of the source, nor of 

 matter near it; it is quite unaffected 

 by motion of source or receiver. Once 

 launched it travels in its own way. If 

 we are travelling to meet it, it will be 

 arriving at us more quickly; if we travel 

 away from it, it will reach us with some 



