84 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 34 



For instance, when the iindulatory theory had made it clear that 

 light was of the nature of waves, the scientists of the day elaborated 

 this by saying that light consisted of waves in a rigid, homogeneous 

 ether which filled all space. The whole content of ascertained fact 

 in this description is the one word " wave " in its strictly mathe- 

 matical sense; all the rest is pictorial detail, introduced to help out 

 the inherited limitations of our minds. 



Then scientists took the pictorial details of the parable literally, 

 and so fell into error. For instance, light waves travel in space and 

 time jointly, but by filling space and space alone with ether, the 

 I^arable seemed to make a clear-cut distinction between space and 

 time. It even suggested that they could be separated out in prac- 

 tice — by performing a Michelson-Morley experiment. Yet, as we all 

 know, the experiment when performed only showed that such a 

 separation is impossible; the space and time of the parable are 

 found not to be true to the facts — they are revealed as mere stage 

 scenery. Neither is found to exist in its own right, but only as a way 

 of cutting up something more comprehensive — the space-time 

 continuum. 



Thus we find that space and time cannot be classified as realities 

 of nature, and the generalized theory of relativity shows that the 

 same is true of their product, the space-time continuum. This can 

 be crumpled and twisted and warped as much as we please without 

 becoming one whit less true to nature — which, of course, can only 

 mean that it is not itself part of nature. 



In this way space and time, and also their space-time product, 

 fall into their places as mere mental frameworks of our own con- 

 struction. They are, of course, very important frameworks, being 

 nothing less than the frameworks along which our minds receive 

 their whole knowledge of the outer world. This knowledge comes 

 to our minds in the form of messages passed on from our senses; 

 these in turn have received them as impacts or transfers of electro- 

 magnetic momentum or energy. Now Clerk Maxwell showed that 

 electromagnetic activity of all kinds could be depicted perfectly as 

 traveling in space and time — this was the essential content of his 

 electromagnetic theory of light. Thus space and time are of pre- 

 ponderating importance to our minds as the media through which 

 the messages from the outer world enter the " gateways of know- 

 ledge ", our senses, and in terms of which they are classified. Just 

 as the messages which enter a telephone exchange are classified by 

 the wires along which they arrive, so the messages which strike our 

 senses are classified by their arrival along the space-time framework. 



Physical science, assuming that each message must have had a 

 starting point, postulated the existence of " matter " to provide such 



