^36 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



A few years ago, it was difficult to believe that the sun could pro- 

 duce its radiation by the actual annihilation of its substance, but in 

 these few years the short-lived positive electron, or "positron", has 

 been detected in the laboratory. This has given us every reason for 

 thinking that the transformation of matter into radiation is contin- 

 ually going on in ordinary terrestrial matter, as well as the converse 

 process of the creation of matter out of the energy of radiation. With 

 this source of energy to call on, there is no longer any objection to our 

 assigning ages of millions of millions of years to the stars. 



It was not easy to visualize the vastness of astronomical space, and 

 it is even less easy to conceive of the immensity of astronomical time. 

 A fairly lengthy book contains about 200,000 words averaging five 

 letters each. Let us take the whole of such a book to represent the 

 age of the earth. Then the whole of civilization is represented by 

 the last word or two, and the whole of the Christian era by something 

 less than the last letter. A single lifetime is a good deal less than 

 the final full stop with which the book ends. Such is the age of 

 our own planet, and, whatever view we take, the age of the whole 

 universe, on the same scale, is a matter of volumes. If the view 

 I put forward last is correct, it must be represented by a library of 

 some thousands of volumes. 



