2 Bateman, The Physical Aspect of Time. 



there is no fixed method by which two sequences of events 

 may be compared in the mind. The comparisons which 

 actually occur give a qualitative description of events, 

 inasmuch as the sequence of processes is generally 

 unaltered in direct perception and in memory, but the 

 lack of a standard set of units invariably connected 

 v/ith the method of comparison, prevents the description 

 from being a true quantitative one. 



This being the case, we are met with a fundamental 

 difficulty when we try to analyse the idea of simultaneity 

 as presented to us by the mind. 



If we could represent an event by a point on a line, 

 the idea of simultaneity would be quite simple, for two 

 events could be regarded as simultaneous when their 

 representative points were coincident. In reality such a 

 representation is not valid, there is no sensation of such a 

 simple nature that it can be represented by a point on 

 a line. If we adopt a representation by means of an 

 interval on a line, we obtain what is probably a truer 

 representation of an event as regards its duration ; but if 

 we suppose that two events are simultaneous when their 

 representative intervals have a common part, it is clear 

 that two events which are simultaneous with the same 

 event would not necessarily be simultaneous with one 

 another. 



It will be realised after a little thought that we can 

 only obtain a satisfactory definition of simultaneity by 

 introducing the idea of the measurement of time ; we are 

 thus obliged to consider the physical aspect of time in 

 order to understand the idea of simultaneity. 



An observer provided with an instrument for measur- 

 ing time, such as a clock or a pendulum, can attach a 

 definite number to each event that occurs. In some 

 cases he may find it difficult to decide as to which of two 



