TIME AND MOTION 67 



torial representations of kinematics as that sci- 

 ence was left by Newton. Without making a 

 great effort to secure completeness or avoid re- 

 dundancy, the essential postulates of Newton's 

 kinematics may be stated about as follows : 



1. There is an absolute measure of lapse of 

 time and an absolute measure of spatial dis- 

 tance. If a set of (perfect) chronometers has 

 once been brought together in a single room 

 and set at the same hour, then however and 

 wherever these chronometers are transported 

 they always measure the lapse of time between 

 two events without ambiguity. If from certain 

 chosen bases we make a number of (perfect) 

 surveys by measurements and triangulations, 

 the distance between the places where two events 

 occur will also be ascertained without ambiguity. 

 This postulate, which we shall have to scrutinize 

 presently, may be called the postulate of a uni- 

 versal or absolute time and space. 



2. However, there is no unique zero hour. 

 The lapse of time between two events is inde- 

 pendent of the particular setting of the chrono- 

 meters. Thus, it is immaterial whether the 

 chronometers when all started together were set 

 at twelve o'clock or six o'clock. This postulate 

 may be called relativity of position in time. 



