24 Journal of the Mitchell Society ' [September 



might, by contraction of the stone slab, become exactly equal to the 

 thwartwise path, and if so, no displacement of the interference frinoes 

 would result. Besides, this contraction is to be expected, anyhow, on 

 the basis of the electron tlieory of matter, and in just the amount nec- 

 essary to explain the negative result of the Michelson-Morley ex- 

 periment. Tests were then made with wood and steel beams, in jilace 

 of the stone slab, and it was found that they apparently contracted 

 in the same manner and to the same extent, so we conclude that all 

 matter behaves in the same way. But if such a contraction takes place 

 in crystals, it looks as though double refraction should take place in 

 them. This was tried b^- Lord Rayleigh and b}' Brace, but again 

 with a negative result. 



It seemed as though all the forces of nature were in a conspiracy 

 to defeat our efforts to find a fixed frame of reference, and the deter- 

 mination of the absolute vBlocity of the earth with reference thereto, 

 so that after all our work and experimentation it must be admitted 

 that we have but the slightest real idea of either the magnitude or 

 direction of our motion through space, though it would be of the first 

 importance to us in astronomy and physics if we could only know it. 



Now we come to the Einstein Theory of Relativity, which was at 

 first an attempt simply to explain the negative results of the Michel- 

 son-Morley experiment. We must clearly distinguish three steps or 

 stages in the development of this theory: (1) the Special Relativity 

 theory; (2) the General Relativity theory; and (3) the latter theory 

 as applied to gravitation, or the Einstein Theory of Gravitation. 



To aid us in understanding the theory of Relativity, let us recall 

 a few of the results attained in the development of Newtonian mechan- 

 ics, on which we have built confidently the entire structure of modern 

 physical science. (Of course the Newtonian mechanics, in its turn, 

 is founded on Euclidean geometry, with its dozen axioms and postu- 

 lates and its three-dimensional space.) In our search for the funda- 

 mental, bedrock conceptions, we have adopted, following the lead of 

 Newton, those of Length, Mass and Time, as separate and distinct 

 ideas, independent of each other, and perhaps capable of absolute 

 measurement. For these we have adopted as our fundamental units 

 the centimeter for length, the gram for mass, and the second for time, 

 giving us the centimeter-gram-second or c.g.s. system of units. We 

 have attempted to base all other ideas, such as force, work, energy, 

 etc., on these as derived ideas, and we call their units derived units. 



