MODIFYING OUR IDEAS OF NATURE : THE EINSTEIN 

 THEORY OF RELATIVITY. 1 



By Heney Norris Russell, 

 Professor of Astronomy in Princeton University. 



It is probably a long time since there has been any occasion on 

 which a matter so definitely belonging to pure science as the " the- 

 ory of Einstein " has excited so much popular interest. 



Although the statements in the newspapers concerning " the over- 

 throw of Newton's laws " and similar " scare heads " have gone be- 

 yond the more sober statements of scientific authorities, it is never- 

 theless true that the theory of relativity, of which the recent work 

 of Einstein forms an extension, has modified our conceptions of 

 nature in a very remarkable fashion. 



Einstein's reported statement that there were not more than 12 

 men in the world who could read and fully understand his book 

 was probably quite within the facts. But the elementary ideas on 

 which the theory of relativity is based do not involve any difficult 

 mathematics, and the only obstacle to grasping or holding them is 

 their remarkable novelty. We can understand them easily enough, 

 or at least understand what they are about, if only we begin at the 

 beginning. 



It probably has not occurred to all of you that while I was speak- 

 ing the last sentence we traveled several hundred miles. Yet, of 

 course, we did. If we had not, the earth would have left us behind 

 it somewhere in empty space. 



In fact, we are undergoing a very complicated series of motions, 

 carried around with the rotating earth and swinging along much 

 more rapidly and in a much vaster curve with its orbital motion. 



But of this fact we are blissfully unconscious. Why? Because 

 the motion is perfectly smooth, without jar or shock, and in par- 

 ticular because not merely we ourselves, but all the objects that 

 constitute our environment, are moving together. 



1 Reprinted by permission from Princeton Lectures, No. 2, Princeton, N. J., May 1, 

 1920. 



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