1,920] The Theory of Relativity 35 



technikiim, from which he went to the University of Prague. Just 

 before the war he was called to the University of Berlin, at the 

 age of forty. He did not sympathize with the militarists and pro- 

 tested vehemently against the famous, or rather infamous, manifesto 

 of the German professors in 1915. His frank statement expressing 

 his thanks to the English government and to his ''English colleagues" 

 for going to so much trouble and expense to verify his predictions, 

 when he was himself helpless to do so, shows a fine spirit, and has 

 gained for him both admiration and respect. It was, in part, as 

 follows : "It was in accordance with the high and proud tradition 

 of English science that English scientific men should have given their 

 time and labor, and that English institutions should have provided the 

 material means, to test a theory that had been completed and published 

 in the country of their enemies in the midst of war." 



Some of the more mathematical and theoretical conclusions drawn 

 from his equations may be interesting. If a circle be imagined in 

 empty space, its circumference bears to its diameter the usual ratio 

 of 3.14159 to 1, but if a heavj^ mass be placed at its center, the ratio 

 of circumference to diameter is changed, because of a ''warp in space" 

 produced by the mass. Again, suppose a wheel is rotating in space. 

 The rim of the wheel, because it is at every point moving in the direc- 

 tion of its length, suifers the contraction already explained in connec- 

 tion with the Michelson-Morley experiment, but the. spokes of the 

 wheel are not moving in the direction of their length, and hence do 

 not suffer contraction. Here again the circumference of the wheel 

 changes length while the diameter does not, so the ratio is again not 

 the usual one. This same contraction in the direction of motion is 

 suffered by electrical, optical and gravitational fields. If a system 

 is moving with respect to us, the unit of time in the moving system 

 seems longer to us than to an observer on that system, and 

 when the system is moving with respect to ours with the velocity of 

 light, their second would seem infinitely long to us. That is, if we 

 could watch a clock face on a system receding from us with the 

 velocity of light, although an observer on the system with the clock 

 would see it running as usual, we would forever see the clock hand 

 at exactly the same point. 



This sounds as crazj' as anything in "Alice in Wonderland," and 

 in fact the Mad Hatter must have been the originator of Relativity, 

 and to have had this very point in mind when he claimed that for 



