Foundations of the Universe 289 



the general lines on which thought is moving toward the final 

 unification. 



We say "unification," but it would be a grave error to think 

 that ether is the only possible basis for such unity, or to make it 

 an essential part of one's philosophy of the universe. Ether was 

 never more than an imagined entity to which we ascribed the most 

 extraordinary properties, and which seemed then to promise con- 

 siderable aid. It was conceived as an elastic solid of very great 

 density, stretching from end to end of the universe, transmitting 

 waves from star to star at the rate of 186,000 miles a second; yet 

 it was believed that the most solid matter passed through it as if it 

 did not exist. 



Some years ago a delicate experiment was tried for the pur- 

 pose of detecting the ether. Since the earth, in travelling round 

 the sun, must move through the ether if the ether exists, there 

 ought to be a stream of ether flowing through every laboratory; 

 just as the motion of a ship through a still atmosphere will make 

 "a wind." In 1887 Michelson and Morley tried to detect this. 

 Theoretically, a ray of light in the direction of the stream ought 

 to travel at a different rate from a ray of light against the stream 

 or across it. They found no difference, and scores of other ex- 

 periments have failed. This does not prove that there is no 

 ether, as there is reason to suppose that our instruments would 

 appear to shrink in precisely the same proportion as the alteration 

 of the light; but the fact remains that we have no proof of the 

 existence of ether. J. H. Jeans says that "nature acts as if no 

 such thing existed." Even the phenomena of light and magnet- 

 ism, he says, do not imply ether; and he thinks that the hypothesis 

 may be abandoned. The primary reason, of course, for giving 

 up the notion of the ether is that, as Einstein has shown, there is 

 no way of detecting its existence. If there is an ether, then, since 

 the earth is moving through it, there should be some way of detect- 

 ing this motion. The experiment has been tried, as we have said, 

 but, although the method, used was very sensitive, no motion was 



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