CLASSICAL AND NEW MECHANICS 181 



is his definition of time. He says, our idea of time 

 is defined by synchronism or the simultaneous occur- 

 rence of an event and the position of the hour-hand 

 of a clock at a certain position, the number seven for 

 example. This is certainly not our idea of time but 

 merely our method of measuring it quantitatively. If 

 we did not have an adequate idea of time as the mere 

 succession of events, we should have no conception of 

 what simultaneous occurrences are nor of how to 

 measure time. His definition gives me the feeling 

 that if I could make clocks go slower my life would 

 become longer. In the review of his memoir, it was 

 pointed out that his definition of simultaneity or isoch- 

 ronism, when combined with the constancy of V, led 

 to the conclusion that two clocks which were syn- 

 chronous, when relatively at rest, would not remain so, 

 if one of them were given a velocity. Moreover the 

 length of a body in motion decreases with respect to 

 its length when at rest. It is certain that these re- 

 sults depend on the constancy of V. If we are willing 

 to rest our knowledge of time and space on a value 

 which by the nature of things can never be put to a 

 direct test, I am convinced of the theoretical correct- 

 ness of these results. But I am not willing to do this. 

 I prefer to trust to the invariability of time and space 

 phenomena, even if it requires V to be a variable and 

 time measurements to contain an unavoidable dis- 

 crepancy. By so doing, I am aware that I forfeit an 



