The Demon Core

The demonstration began on the afternoon of May 21, 1946, at a secret laboratory tucked into a canyon some three miles from Los Alamos, New Mexico, the birthplace of the atom bomb. Louis Slotin, a Canadian physicist, was showing his colleagues how to bring the exposed core of a nuclear weapon nearly to the point of criticality, a tricky operation known as “tickling the dragon’s tail.” The core, sitting by itself on a squat table, looked unremarkable—a hemisphere of dull metal with a nub of plutonium sticking out of its center, the whole thing warm to the touch because of its radioactivity. It had been quickly molded into shape after the bombing of Nagasaki, to be used in another attack on Japan, then reallocated when it turned out not to be needed for the war effort. At that time, Slotin was perhaps the world’s foremost expert on handling dangerous quantities of plutonium. He had helped assemble the first atomic weapon, barely a year earlier, and a contemporary photograph shows him standing beside its innards with his shirt unbuttoned and sunglasses on, cool and collected. Back then, the bomb was a handmade, artisanal product.