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The Atoms for Peace conference in 1953. Image: United Nations
On the cold, rainy morning of July 16, 1945, a group of scientists and soldiers gathered in New Mexico’s Jornada del Muerto desert. Atop a 100-foot steel tower they had placed a large metal ball studded with plugs and wires. The “gadget,” as they called it, was a code word for their secret weapon. Inside it sat another globe made of high explosives, and inside that was a core of subcritical plutonium. This device was the first nuclear explosive, a prototype bomb built to end a war.