BOMBS AT BIKINI 



gard to protocol ; they sweated side by side to get the 

 apparatus ready for recording the full measure of the 

 great explosions of A-Day and B-Day. 



PRESSURE 



Pressure was to be king on A-Day, when the bomb 

 was to explode several hundred feet in the air. It was 

 expected that giant waves or intense gamma radiation 

 might do the worst damage on B-Day, day of the under- 

 water explosion ; but few doubted that pressure would 

 wear the crown on A-Day. 



Air pressure may not sound fearsome. We are — 

 literally — under pressure at all times. The air around 

 us is compressed by the mere weight of overlying air. 

 Every part of our bodies is subjected to a steady pres- 

 sure of 14 or 15 pounds per square inch. Yet we sleep 

 and breathe with ease. 



But although it is true that steady pressures of 

 10 or 20 pounds per square inch go almost unnoticed, 

 it is equally true that sudden increases in pressure 

 (overpressure) can be remarkably effective. Fast, re- 

 current pressure changes as slight as one billionth of a 

 pound per square inch are easily detected by the ear ; 

 many a building can be toppled by a sudden, transient, 

 pressure increase of one pound per square inch. Tran- 

 sient overpressure crtished thousands of buildings at 

 Hiroshima ; it was to sink five ships on A-Day. 



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