TESTA: EXPLOSION IN AIR 



The fireball rose initially at a rate of more than one 

 hundred miles per hour. Within twenty seconds it 

 transformed itself into the fireless head of the mush- 

 room, now one mile high. Two minutes later the mush- 

 room's altitude was five miles; five minutes later it 

 was seven miles, one mile higher than Mt. Everest. 



As the mushroom head rose at express-train speed, 

 it sucked air in beneath it. Scooped up in this turbulent 

 trailing festoon, called the stem, were soot from the 

 stacks of the nearer target vessels, smoke from the 

 flash-burned decks and equipment, and water vapor.* 



The mushroom head broadened as it rose; event- 

 ually it attained a width of nearly two miles. The air 

 rising in the mushroom head became cooler as it rose 

 and expanded; air pushed upw^ard just above the 

 mushroom head was cooled also. This cooling resulted, 

 of course, in condensation. A remarkable phenomenon 

 occurred: a thin white cap or scarf cloud appeared 

 lying just above the mushroom top and cleanly sep- 

 arated from it. It is probable, although not certain, 

 that this consisted not of water droplets but of very 



* The mushroom contained also various unusual gases created hy 

 the bomb's ionizing radiations. These radiations were partially ab- 

 sorbed by the nitrogen and oxygen molecules of the air and the 

 result was: nitrogen molecules were broken up into individual 

 nitrogen atoms; and the oxygen molecules were broken into indi- 

 vidual oxygen atoms. When the unmated nitrogen and oxygen atoms 

 collided, they immediately joined to form molecules containing 

 oxygen and nitrogen together. Such molecules have an apricot 

 color, and traces of this color were clearly visible in the A-Day 

 mushroom. 



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