N'afọ 1941, mgbe Agha Ụwa nke Abụọ na-aga n'ihu na Europe ma United States ka na-alụ agha, Feynman nọrọ n'oge okpomọkụ na-arụ ọrụ na nsogbu ballistics na Frankford Arsenal na Pennsylvania. Mgbe mwakpo ahụ na Pearl Harbor wetara United States n'agha ahụ, Robert R. Wilson, onye na-arụ ọrụ na-arụ ọrụ iji mepụta uranium bara ọgaranya maka iji bọmbụ atọm, dị ka akụkụ nke ihe ga-aghọ Manhattan Project. Ndị otu Wilson na Princeton nọ na-arụ ọrụ na ngwaọrụ a na-akpọ isotron, nke ezubere iji kewapụ electromagnetically uranium-235 site na uranium-238. Emere nke a n'ụzọ dị nnọọ iche na nke ahụ nke otu ndị otu nọ n'okpuru onye nkụzi Wilson, bụ Ernest O. Lawrence, na-arụ ọrụ na Laboratory of Radiation of California. Na Los Angeles, California, Feynman nọrọ n'oge okpomọkụ na-arụ ọrụ nke ọma karịa Paul Olynheyn, bụ onye na-arụ ọrụ na United States. Mgbe mwakpo ahụ mere ka United States banye n'agha ahụ, Robert R. Wilson,
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