THE EINSTEIN THEORY. 



By E. p. ADAMS. 

 (Read April 24, 1920.) 



When your Programme Committee, through the President, asked 

 me to read a paper on the subject of Relativity and the Gravitation 

 Theory at the General Meeting of the Society, I assumed that it 

 was in the thought that one who had occupied himself mainly with 

 the study of concrete physical phenomena might be able to contribute 

 something towards a definite physical conception of the new theory. 



I shall not take more time to go into the question as to how the 

 theory of relativity was developed than merely to say that a number 

 of physical phenomena are known which appear to be in contradic- 

 tion to the system of mechanics founded on Newton's laws of mo- 

 tion. Now Newton's laws are based upon the fundamental concepts 

 of space, time and matter. The space of Newton is the space of 

 Euclid — the space of our ordinary experience. The time of Newton 

 is the time that we ordinarily think of — a conception wholly inde- 

 pendent of our space conception. And matter for Newton is the 

 matter that is perceived by our senses. 



Equally fundamental in Newton's mechanics to the three con- 

 cepts of space, time and matter is that of force — the cause of every 

 change in motion. That the idea of force is as fundamental a 

 notion to us as that of matter there is little doubt ; they are both 

 revealed to us by our senses ; our muscular sense gives us very 

 directly a realization of force. When, however, a system of me- 

 chanics is built up with force as one of the four fundamental 

 concepts a certain indeterminateness arises. I need mention only 

 the controversy that still goes on as to the exact interpretation of 

 centrifugal force, and other forces that we have to consider that 

 are certainly not the cause but the result of motion. And when 

 we extend our system of mechanics so as to cover all physical phe- 

 nomena forces of other kinds must be postulated — electric, magnetic, 



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