TIME 133 



as the others: it bears the same name. Now, if the three 

 dimensions are necessary for the conception of all the directions 

 in space, they are also sujficient to account for our material 

 universe, and there is no place for the intruder in the familiar 

 trihedron of Euclidean space. As the dimensions of space 

 are schematized by three straight lines converging rectangularly 

 the layman tries to figure the 'fourth' in spite of himself as 

 another 'direction'. At any rate this is the impression I 

 received when talking to most people. And this notion is 

 absolutely erroneous. The fourth dimension, as stated above, 

 only represents the existence of the three others, the existence 

 of the trihedron or any other system of reference. It simply 

 indicates the birth in our consciousness of the notion of the 

 three-dimensional space. The history of material points, 

 whether stationary or not, in the system of reference deter- 

 mined by our three rectangular co-ordinates begins the moment 

 this birth has taken place. The phenomena have a point of 

 departure; they evolve; our senses and our memory register 

 them and draw conclusions and laws from them. They are 

 alive for us. Suppress time and nothing remains. The 

 antithesis can be found in Herodotus: 'Let time be lavished 

 and all that is possible will come to pass.' The theory of 

 probability gives this sentence a profound meaning. 



Minkowski's own words: 'Space and time considered in 

 themselves and individually must henceforth retire into the 

 shade, and only a kind of combination of the two must keep 

 a certain reality', do not sufficiently bring out the fact that 

 all reality is the direct co7iseqiience of the conjugation of space 

 and time. The physicist does not have the same difficulty in 

 conceiving the fourth dimension, perhaps because of the 

 habit he has of giving a much broader meaning to the word 

 'dimension'. He reduces the quantities which he measures 

 to three units: centimetre, gram, second, with which he can 

 describe his universe. But the C.G.S. system comprises 

 precisely the four dimensions and, in addition, a more complex 

 dimension of mass. The phj^sicist brings the most diverse 

 magnitudes back to these three basic units and establishes 



