BOMBS AT BIKINI 



up, in \Yhich energy is l^eing constantly absorbed and 

 re-radiated. The velocity of light is well known; but 

 who knows the velocity of such a halting process ? The 

 process cannot be imitated successfully in the labora- 

 tory ; we have little to go on except estimates by ther- 

 mod\^iamics experts — and close study of Test A at 

 Bikini. 



The rate of spreading of this optical radiation zone 

 (rate of growth of the fireball) was to be measured 

 principally by cameras. But no ordinary camera would 

 do. Two special types, the O 'Brien and the Bowen, were 

 obtained. Each of these had microsecond resolution; 

 that is, each could distinguish what happened from one 

 millionth of a second to the next millionth. Each was 

 set up several miles from the target area center ; each 

 was capable of charting the fireball 's development from 

 birth to old age, a total span of only one or two sec- 

 onds. 



The lowly human eye was used also. In order to 

 escape temporarj^ blindness, it had to be protected by 

 dark goggles* or by the ingenious device called an 

 Icaroscope. It was realized in advance that goggles 

 could not be a perfect solution. Goggles satisfactory 

 for the instant of greatest brightness would, of course, 

 be too dark for the ensuing less-bright intervals. It 



* Most of the 6000 users of the special goggles found them too 

 dark. This was due partly to the abnormally great extent to which 

 light was absorbed in traveling for mayiy miles just above the 

 surface of the water; also it ivas due partly to the desire of the 

 safety advisers to make doubly sure that no one would suffer any 



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