MATTER, SPACE, AND TIME 259 



the Island of Principe in the Gulf of Guinea, on 

 29th May 1 9 19. The result was in accordance 

 with Einstein's prediction. 



(3) On the principle of relativity, the electrons 

 in a gravitational field should vibrate more slowly 

 than the normal. Hence the lines in the spectrum 

 of the sun, where gravity is strong, should be 

 slightly shifted towards the red. For long this 

 effect was looked for in vain, but lately evidence 

 in its favour has been obtained. 



The balance of experimental evidence, then, 

 leans decidedly towards Einstein's interpretation 

 of nature, or possibly some modification of it such 

 as that put forward by Professor A. N. Whitehead, 

 and we must learn to regard as merely relative, 

 many concepts we had come to accept as 

 absolute. 



Doubtless this new outlook has not only a 

 physical but also a philosophical importance. 

 Space and time no longer exist independently of 

 each other and of events which happen. Nature 

 is a complex continuum, in which matter, space, 

 and time are all inextricably involved. The 

 separation is no more than a question of human 

 convenience like the separation of science into 

 physics, chemistry, and biology. Many of the 

 familiar concepts in which, first by the ordered 

 common sense of successive generations of men, 

 and then by the more subtle analysis of science, 

 we had come to express our mental picture of the 

 world, have been proved to be merely relative to 

 ourselves. The length of a rod, the time beaten 

 out by a pendulum, the mass of a chemical atom, 

 so constant and absolute to our fathers, are now 

 seen to be relations between us and the body 



