PEESENT STATUS OF THEORY AND EXPERIMENT AS 

 TO ATOMIC DISINTEGRATION AND ATOMIC SYN- 

 THESIS ^ 



By ROBEET A. MiLLIKAN 



California Institute of Technology, Pasadena, Calif. 



My task is to attempt to trace the history of the development of 

 scientific evidence bearing on the question of the origin and destiny 

 of the physical elements. I shall list 10 discoveries or developments, 

 all made within the past 100 years, which touch in one way or an- 

 other upon this problem and constitute indications or sign-posts 

 on the road toward an answer. 



Prior to the middle of the nineteenth century little experimental 

 evidence of any sort had appeared, so that the problem was wholly 

 in the hands of the philosopher and the theologian. Then came, 

 first, the discovery of the equivalence of heat and work, and the con- 

 sequent formulation of the principle of the conservation of energy, 

 probably the most far-reaching physical principle ever developed. 



Following this, and directly dependent upon it, came, second, the 

 discovery, or formulation, of the second law of thermodynamics, 

 which was first interpreted, and is still interpreted by some, as ne- 

 cessitating the ultimate " heat-death " of the universe and the final 

 extinction of activity of all sorts; for all hot bodies are observed 

 to be radiating away their heat, and this heat after having been 

 so radiated away into space apparently can not be reclaimed by man. 

 This is classically and simply stated in the humpty-dumpty rhyme. 

 As a natural if not necessary corollary to this was put forward 

 by some, in entire accord with the demands of medieval theology, 

 a Deus ex machina initially to wind up or start off this running- 

 down universe. 



Then came, third, the discovery, through studies both in geology 

 and biology, of the facts of evolution — facts which showed that, 

 so far as the biological field is concerned, the process of creation, 

 or upbuilding from lower to higher forms, has been continuously 



» Retiring presidential address to the American Association for the Advancement of 

 Science, delivered at Cleveland on Dec. 29, 1930. Reprinted, with author's revision, by 

 permission from Nature, vol. 127, No. 3196, Jan. 31, 1931. 



277 



