Because of their shapes. Fat Man used plutonium. A sphere of plutonium was surrounded by conventional explosives which were designed to send the force of their explosion inward to crush the sphere into a smaller shape (thus higher density) in order to trigger the nuclear reaction. Thus the bomb had a very rounded shape to it, suggestive of a fat man. In contrast the other bomb, which used uranium, had the nuclear reaction triggered by firing a small slug of uraniun down a track into a larger mass of the same element. Thus that bomb looked long and slender by comparison and so picked up the moniker Little Boy in contrast. Michael Montagne
Little Boy was employed at Hiroshima and Fat Man at Nagasaki.
"Little Boy" was dropped on Hiroshima and "Fat Man" was dropped on Nagasaki .
'Little Boy' was dropped upon Hiroshima whereas 'Fat Man' was dropped upon the Japanese city of Nagasaki .
Fat Man and Little Boy
The atomic bomb that was dropped on Hiroshima was named "Little Boy." The atomic bomb that was dropped on Nagasaki was named "Fat Man."
Little Boy was dropped on Hiroshima Fat Man was dropped on Nagasaki
Little Boy was employed at Hiroshima and Fat Man at Nagasaki.
"Little Boy" was dropped on Hiroshima and "Fat Man" was dropped on Nagasaki .
Fat man and little boy.
The planes were both B29 Superfortress'; the Enola Gay (Hiroshima) and Bock's Car (Nagasaki).
Little boy was dropped over Hiroshima and fat boy was dropped over Nagasaki.
'Little Boy' was dropped upon Hiroshima whereas 'Fat Man' was dropped upon the Japanese city of Nagasaki .
They were called Little Boy and Fat man. (see related question link below)
Fat Man and Little Boy
'Little Boy' (Hiroshima) 'Fat Man' (Nagasaki)
Hiroshima and Nagasaki Japan.
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