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The Nuclear Yield Hidden in a Photograph
A physicist recovered the first atomic bomb’s yield from public photographs using nothing but the algebra of units
In 1950 the British physicist Geoffrey Ingram Taylor published a number the United States still regarded as classified: the energy released by the first atomic bomb. Taylor was no outsider — a member of the British delegation to the Manhattan Project, he had worked at Los Alamos and watched the Trinity fireball rise over the New Mexico desert himself. But his published derivation drew on none of that: not a briefing, not a vault, not the hydrodynamics of a nuclear explosion. He read the number off a handful of photographs.
The images — frames of the Trinity fireball swelling over the New Mexico desert, each stamped with the time since detonation and printed beside a scale bar — had appeared in the open press. Taylor measured how the luminous ball of hot gas grew from one frame to the next, and from that growth alone recovered a yield on the order of twenty kilotons of TNT, close to the true figure. He integrated no shock equations. He solved no differential equation for the blast. He used dimensional analysis — the principle that a correct physical law must balance in its units, which is often enough to rebuild a quantity from the handful of ingredients it can…
