280 ANNUAL, EEPORT SMITHSONIAIST INSTITUTION", 1931 



within very small limits of uncertainty. This fact alone raises very 

 insistently the query as to whether they are not being built up some- 

 where out of hydrogen now. They certainly were once so put to- 

 gether, and some of them, the radioactive ones, are now actually 

 caught in the act of splitting up. Is it not highly probable, so would 

 say any observer, that the inverse process is going on somewhere, 

 especially since the process would involve no violation either of the 

 energy principle or of the second law of thermodynamics; for hydro- 

 gen, the element out of which they all must be built, has not a 

 weight exactly one in terms of the other 92, but about 1 per cent 

 more than one, so that since mass or weight had been found in the 

 sixth discovery to be expressible in terms of energy, the union of 

 any number of hydrogen atoms into any heavier element, meant that 

 1 per cent of the total available potential energy had disappeared 

 and was therefore available for appearance as heat. 



When, about 1914-15 this fact was fitted by MacMillan, Harkins, 

 and others into the demand made above in the fifth discover}^ for a 

 new source of energy to keep the sun pouring out heat so copiously 

 for such great lengths of time, it seemed to the whole world of 

 physics that the building up of the heavier elements out of hydrogen 

 under the conditions existing within the sun and stars had been 

 practically definitely proved to be taking place. This would not 

 provide an escape from the heat-death, but it would enormously 

 postpone it, that is, until all the hydrogen in the universe had been 

 converted into the heavier elements. 



By this process, however, the suns could stoke at most but 1 per 

 cent of their total mass, assuming they were wholly hydrogen to 

 begin with, into their furnaces, and 99 per cent of the mass of the 

 universe would remain as cold, dead ash when the fires were all gone 

 out and the heat-death had come. But about 1917 the astronomer 

 began to chafe under the time limitation thus imposed upon him, 

 and this introduced the eighth consideration bearing upon our theme. 

 He could get a hundred times more time — from now on, much more 

 than that, because only a small fraction of the matter in the universe 

 is presumably now hydrogen — by assuming that, in the interior of 

 heavy atoms, occasionally a negative electron gets tired of life at the 

 pace it has to be lived in the electron world, and decides to end it all 

 and commit suicide; but, being paired by Nature in electron-fate 

 with a positive, he has to arrange a suicide 2)act with his mate, and so 

 the two jump into each other's arms in the nucleus, and the two 

 complementary electron lives are snuffed out at once ; but not with- 

 out the letting loose of a terrific death-yell, for the total mass of 

 the two must be transformed into a powerful ether pulse which, by 

 being absorbed in the surrounding matter, is supposed to keep up 



