62 TIME 



certain events in the past or future occur Here but not 

 Now; knowledge of absolute simultaneity would tell us 

 that certain events occur Now but not Here. Removing 

 these artificial sections, we have had a glimpse of the 

 absolute world-structure with its grain diverging and 

 interlacing after the plan of the hour-glass figures. By 

 reference to this structure we discern an absolute dis- 

 tinction between space-like and time-like separation of 

 events — a distinction which justifies and explains our 

 instinctive feeling that space and time are fundamentally 

 different. Many of the important applications of the 

 new conceptions to the practical problems of physics 

 are too technical to be considered in this book; one of 

 the simpler applications is to determine the changes of 

 the physical properties of objects due to rapid motion. 

 Since the motion can equally well be described as a 

 motion of ourselves relative to the object or of the 

 object relative to ourselves, it cannot influence the abso- 

 lute behaviour of the object. The apparent changes in 

 the length, mass, electric and magnetic fields, period of 

 vibration, etc., are merely a change of reckoning intro- 

 duced in passing from the frame in which the object is 

 at rest to the frame in which the observer is at rest. 

 Formulae for calculating the change of reckoning of 

 any of these quantities are easily deduced now that the 

 geometrical relation of the frames has been ascertained. 



