TIME AND MOTION 79 



limitation of individual freedom. But let these 

 people try to conceive of a temperature below 

 — 273° C, let them think of an anMe whose sine 



does not lie below zero and one. 



We have seen that the first postulate of New- 

 tonian kinematics required that there be no 

 limit to possible velocities. Einstein's discovery 

 therefore means that w^e must abandon the pos- 

 tulate of a universal time and the geometry that 

 went with it. We thus arrive at what may be 

 called a non-Newtonian kinematics, and when 

 we look for a geometry to express the new kine- 

 matics we find one which proves to be adequate 

 even in the minutest detail. It is the remaining 

 one of the flat non-Euclidean geometries; the 

 geometry of asymptotic rotation that we owe 

 to the genius of Minkowski. 



If we remind ourselves of this geometry by 

 means of Figure 5 of the last chapter, we see 

 that the singular (broken) lines divide all the 

 lines through O into two classes, represented by 

 OA' and OA. And now we correlate this geome- 

 try T\dth kinematics by stating that any distance 

 along a line such as OA' corresponds to read- 

 ings with a measuring rod, while any distance 

 along a line such as OA corresponds to read- 



