176 PROGRESS OF SCIENCE IN THE CENTURY. 



idea; but it may be that what we call matter will turn 

 out to be conceivable as loops and knots in the threads 

 of ether. 



THEORY OF THE ETHER. 



Among the concepts which have come to stay in 

 scientific thinking, that of the ether must now be in- 

 cluded. It is as real as the concept of " atom " or 

 " molecule," but hardly more so. Perhaps the most 

 natural way of appreciating its validity is by con- 

 sidering some of the facts which have made it seem to 

 many a necessary hypothesis. 



Premonition of the Idea. Long before the nine- 

 teenth century, the scientific mind, e.g., Newton's, 

 seemed to feel the need of supposing that there was 

 " something " occupying space between the heavenly 

 bodies. 



It does not seem very evident why the extent of 

 distance should make much difference, but, for his- 

 torical purposes at least, it is well to recall the im- 

 pression made by the discovery or rather demonstra- 

 tion of the fact that most of the heavenly bodies are 

 at a literally immense unmeasurable distance 

 from the earth. 



Light travels at a rate of about 186,000 miles in 

 a second, and could flash nearly eight times round the 

 earth in that time; but if a hypothetical inhabitant 

 of the nearest star could by any means see the earth, 

 he would see the events of three or four years ago. 

 Now, as we are sure that light is not any kind of 

 stuff or substance, but a form of energy or power, we 

 may, in some measure, understand why to some 

 minds it has seemed necessary to suppose that there 

 is some sort of something linking that star to us. 



