28 Journal of the Mitchell Society [September 



or as Stewart says, "we have the Principle of Relativity destroying 

 a concept which is nsed in one of its postulates," — another instance 

 of Topsyturv.ydom. 



Einstein admits this, but cannot get away from the confidence he, 

 and all other physicists, have always had in Maxwell's great theory 

 of electrodynamics, and the equations in which it is expressed, and 

 so Einstein states in his London "Times" article that for this reason 

 he was led to achieve the logical reconciliation of his two postulates 

 b}- making a change in the doctrine of the physical laws of time and 

 space. In doing so, however, he was obliged to overthrow some of the 

 time-honored ideas of Galileo and Newton, and deal wath four-dimen- 

 sional, instead of three-dimensional space. Of course that also meant 

 using non-Euclidean mathematics, and the difficulties pressing upon 

 him from every side seemed nisuperable. But he was immensely 

 helped by the work of Minkowski, who developed a system of four 

 dimensions, — using time for the fourth dimension, — involving four 

 rectangular axes, of which three are for the three space dimensions, 

 and the fourth is the time axis. Space and time are thus bound to- 

 gether, and no mathematical difference is made between them, the axes 

 being interchangeable. 



It is of course impossible for us to conceive of four dimensions all 

 at right angles to each other, but let us take this example : When we 

 go to the moving-picture show, we see the screen picture in only two 

 dimensions, of course. But we supply a third dimension in our minds 

 by seeing the perspective of the picture. We see a horseman coming 

 in the distance apparently straight towards us, along the third axis 

 wdiich our mind supplies perpendicular to the screen. But there is 

 another element in the picture, the time element. Time is always 

 of the essence in melodrama. The interest centers in the question as 

 to whether the hero, beset with difficulties and dangers, as he always 

 is, will be in time to rescue the fair heroine. This time element, 

 measured along an imaginary time axis, is also mentally present, and 

 the picture is not complete without it. And moreover, as stated before, 

 while we cannot visualize this axis at right angles to the others, the 

 mathematician can make his equations behave exactly as though we 

 could. 



What Tennyson calls our "bourne of time and place," therefore, 

 Minkowski calls a four-dimensional "space-time continuum," and by 

 using four-dimensional geometrv he showed Jww events in nature may 



