122 GRAVITATION— THE LAW 



Astronomical observations show that within certain 

 limits of accuracy both Einstein's and Newton's laws 

 are true. In confirming (approximately) Newton's law, 

 we are confirming a statement as to what the appear- 

 ances would be when referred to one particular space- 

 time frame. No reason is given for attaching any 

 fundamental importance to this frame. In confirming 

 (approximately) Einstein's law, we are confirming a 

 statement about the absolute properties of the world, 

 true for all space-time frames. For those who are try- 

 ing to get beneath the appearances Einstein's statement 

 necessarily supersedes Newton's; it extracts from the 

 observations a result with physical meaning as opposed 

 to a mathematical curiosity. That Einstein's law has 

 proved itself the better approximation encourages us in 

 our opinion that the quest of the absolute is the best way 

 to understand the relative appearances; but had the suc- 

 cess been less immediate, we could scarcely have turned 

 our back on the quest. 



I cannot but think that Newton himself would rejoice 

 that after 200 years the "ocean of undiscovered truth" 

 has rolled back another stage. I do not think of him as 

 censorious because we will not blindly apply his formula 

 regardless of the knowledge that has since accumulated 

 and in circumstances that he never had the opportunity 

 of considering. 



I am not going to describe the three tests here, since 

 they are now well known and will be found in any of 

 the numerous guides to relativity; but I would refer to 

 the action of gravitation on light concerned in one of 

 them. Light-waves in passing a massive body such as 

 the sun are deflected through a small angle. This is 

 additional evidence that the Newtonian picture of 

 gravitation as a tug is inadequate. You cannot deflect 



