CONTRIBUTIONS FROM THE RESEARCH LABORATORY OF 

 PHYSICAL CHEMISTRY OF THE MASSACHUSETTS 

 INSTITUTE OF TECHNOLOGY.— No. 42. 



THE PRINCIPLE OF RELATIVITY, AND NON-NEWTONIAN 



MECHANICS. 



By Gilbert N. Lewis and Richard C. Tolman. 



Presented May 18, 1009. Received May 18, 1900. 



Until a few years ago every known fact about light, electricity, and 

 magnetism was in agreement with the theory of a stationary medium 

 or ether, pervading all space, but offering no resistance to the motion 

 of ponderable matter. This theory of a stagnant ether led to the belief 

 that the absolute velocity of the earth through this medium could be 

 determined by optical and electrical measurements. Thus it was pre- 

 dicted that the time required for a beam of light to pass over a given 

 distance, from a fixed point to a mirror and back, should be different 

 in a path lying in the direction of the earth's motion, and in a path lying 

 at right angles to this line of motion. This prediction was tested in 

 the crucial experiment of Michelson and Morley, 1 who found, in spite 

 of the extreme precision of their method, not the slightest difference in 

 the different paths. 



It was also predicted from* the ether theory that a charged condenser 

 suspended by a wire would be subject to a torsional effect due to the 

 earth's motion. But the absence of this effect was proved experi- 

 mentally by Trouton and Noble. 2 



The skill with which these experiments were designed and executed 

 permits no serious doubt as to the accuracy of their results, and we are 

 therefore forced to adopt certain new views of far-reaching importance. 



It is true that the results of Michelson and Morley might be simply 

 explained by assuming that the velocity of light depends upon the 

 velocity of its source. Perhaps this assumption has formerly been dis- 

 missed without sufficient reason, but recent experimental evidence to 

 which we shall revert seems to prove it untenable. 



1 Amer. Jour. Sci., 34, 333 (1887). 



2 Phil. Trans. Roy. Soc. (A), 202, 165 (1904). 



