26 HOLISM AND EVOLUTION chap. 



ical form to what extent it affects our vision and judgment of 

 movement in the world. Let us therefore take the case of 

 moving observers. Now when a moving object (say a train 

 in motion) is viewed by an observer in motion (say an 

 observer in a motor-car moving on a road parallel to the 

 train), certain curious results have been worked out by the 

 mathematicians, of which the following are two important 

 samples: 



(A) The train appears a little shorter than it would to a 

 stationary observer. 



(B) The time taken by the train to pass a point appears a 

 little longer (or the train appears to move somewhat more 

 slowly) than it would to a stationary observer. 



In other words, to a moving observer the length or the 

 space occupied by a moving body is smaller in the direction 

 of its motion than it would appear to a stationary observer; 

 and similarly the time taken by the observed body to pass 

 a point will be longer. And the faster the observer 

 or observed body moves, the more the space and time 

 of the observed body will vary for him, compared to what 

 they would do if he were at rest. These two variations of 

 space and time are joint variations, happening simultane- 

 ously but in an opposite direction, the one becoming less 

 in proportion as the other becomes more to the moving 

 observer. Space contracts and time expands in inverse 

 proportions according to the rate of motion of a moving 

 body of reference or a moving observer. One may gen- 

 eralise this result and say that so long as several 

 observers move at different rates but uniformly and 

 in straight lines with regard to each other, the velocity 

 or speed of the moving body which they are observing 

 appears the same to all of them, as the proportional 

 co-variations of their respective spaces and times cancel each 

 I other out, so to say. This is a popular way of stating the 

 J main principle of Einstein's Special Theory of Relativity, 

 first published in 1905, in rigorous mathematical form. It 

 explained the fact, which had been repeatedly confirmed by 



