6 PHENOMENA, ATOMS, AND MOLECULES 



which could be given, show that it is possible for single unpredictable 

 quantum events to alter the course of human history. 



The formation of crystals on cooling a liquid involves the. formation 

 of nuclei or crystallization centers that must originate from discrete, 

 atomic phenomena. The spontaneous formation of these nuclei often de- 

 pends upon chance. 



At a camp at Lake George, in winter, I have often found that a pail of 

 water is unfrozen in the morning after being in a room far below freezing, 

 but it suddenly turns to slush upon being lifted from the floor. 



Glycerine is commonly known as a viscous liquid, even at low tempera- 

 tures. Yet if crystals are once formed they melt only at 64° F. If a minute 

 crystal of this kind is introduced into pure glycerine at temperatures below 

 64° the entire liquid gradually solidifies. 



During a whole winter in Schenectady I left several small bottles of 

 glycerine outdoors and I kept the lower ends of test-tubes containing 

 glycerine in liquid air for days, but in no case did crystals form. 



My brother, A. C. Langmuir, visited a glycerine refinery in Canada 

 which had operated for many years without ever having any experience 

 with crystalline glycerine. But suddenly one winter, without exceptionally 

 low temperatures, the pipes carrying the glycerine from one piece of ap- 

 paratus to another froze up. The whole plant and even the dust on the 

 ground became contaminated with nuclei and although any part of the 

 plant could be temporarily freed from crystals by heating above 64° it was 

 found that whenever the temperature anywhere fell below 64° crystals 

 would begin forming. The whole plant had to be shut down for months 

 until outdoor temperatures rose above 64°. 



Here we have an example of an inherently unpredictable divergent 

 phenomenon that profoundly affected human lives. 



Every thunderstorm or tornado must start from a small beginning and 

 at least the details of the irregular courses of such storms across the coun- 

 try would be modified by single quantum phenomena that acted during 

 the initial stages. Yet small details such as the place where lightning strikes 

 or damage occurs from a tornado may be important to a human being. 



Much more obvious examples of divergent phenomena which affect 

 human life are those involved in the mechanism of heredity and the origin 

 of species. Whether the genes are inherited from the mother or from the 

 father seems to be fundamentally a matter of chance, undoubtedly involv- 

 ing changes in single atoms. It is known definitely that changes in genes 

 or mutations can be produced by x-rays, and it has even been proved that 

 a single quantum is sufficient to bring about such an alteration. The growth 

 of any animal from a single cell is a typical illustration of a divergent 

 phenomenon. The origins of species and all evolutionary processes, in- 



