BOMBS AT BIKINI 



Although the fireball itself was rich in ultraviolet 

 light, including light of the ''vacuum ultraviolet" re- 

 gion, much of this light was cut off from observers by 

 the intervening atmosphere. Practically no light of 

 wavelengths less than 3000 Angstrom units was de- 

 tected near sea level at ranges of twenty miles. Much 

 infrared light was detected, although here again ab- 

 sorption by the atmosphere was severe. The water vapor 

 content of the atmosphere was of course great, and such 

 vapor is well known for its reluctance to transmit 

 infrared light. 



THE MUSHROOM 



The mushroom, now the common sjaiibol of the 

 atomic age, was far more spectacular than any still 

 photograph can suggest. Its height and statuesque 

 beauty were impressive ; but even more impressive was 

 the speed of its writhing upward surge. 



The speed of its ascent is understandable enough. 

 When the bomb exploded, Avhite hot gases instantly 

 spread and filled a region about one-third of a mile in 

 diameter. But these gases were ver}^ thin ; their aggre- 

 gate weight was extremely slight — about the same, in 

 fact, as the weight of a hydrogen-filled balloon of equal 

 diameter. Now a hydrogen-filled balloon of this fan- 

 tastic size would have enough lift to raise tJwusands of 

 tons. Such, then, was the magnitude of the buoyant 

 force urging the fireball upward. 



18 



