SCIENTIFIC OFFENSIVE 



Size and rate of growth of the fireball came in for 

 much attention. The creation of the atomic bomb had 

 fascinated experts on thermodynamics who were ask- 

 ing themselves : When the explosion first occurs, which 

 gets oft' to the fastest start: the pressure wave? the 

 optical radiation ? the nuclear radiation ? or actual ma- 

 terials from the bomb ? Satisfactory answers were non- 

 existent. Everyone agreed that at the instant of det- 

 onation, the bomb, or at least what had been the bomb, 

 is extremely hot. Its temperature is perhaps of the 

 order of a million degrees Centigrade. And everyone 

 agreed that every bit of matter which has that temper- 

 ature cannot fail to emit enormous quantities of op- 

 tical radiation. (It is well known, for example, that 

 doubling tlie temperature of a hot body causes it to 

 emit sixteen times as much energy, so that the rate of 

 emission of energy from a body raised to a million de- 

 grees must be staggering indeed.) But a tremendous 

 complication at once sets in. The bulk of the energy is 

 of very short wavelength, a wavelength which the at- 

 mosphere refuses to transmit. Thus a curious kind of 

 leapfrog must be taking place: the short- wavelength 

 energy starts outw^ard, but before it has gone more than 

 a few feet, it is absorbed by the surrounding air. The 

 surrounding air, however, is so heated by having ab- 

 sorbed this energy that it becomes highly luminous 

 and itself radiates energy. This energy fares little 

 better than the previous generation and is in turn ab- 

 sorbed. So a sort of leapfrogging chain-reaction is set 



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