underwent fission, and only seven hundred milligrams of mass—the weight of a butterfly—was converted into energy. But it was enough to obliterate an entire city in a fraction of a second. Some seventy-eight thousand people died instantly, or immediately afterward—vaporized, crushed, or incinerated in the firestorm that followed the blast wave. But by the end of the year, another twenty-five thousand men, women, and children would also sicken and die from their exposure to the radiation liberated by the world’s first atom bomb attack.
