Hiroshima was destroyed in a flash by a bomb dropped from a propeller-driven B-29 of the U.S. Army Air Corps, on the warm morning of Monday, August 6, 1945. The bomb was not chemical, as bombs until then had been, but atomic, designed to release the energies that Einstein had described. It was a simple cannon-type device of the sort that today any number of people could build in a garage. It was bulbous and black, about ten feet long, and weighed ninety-seven hundred pounds. It fell nose-down for forty-three seconds and, for maximum effect, never hit the ground. One thousand nine hundred feet above the city it fired a dull gray plug of highly enriched uranium down a steel tube into a receiving lump of the same refined material, creating a combined uranium mass of 133 pounds. In relation to its surface area, that mass was more than enough to achieve criticality and allow for an uncontrollable chain of fission reactions, during which subatomic particles called neutrons collided with uranium nuclei, releasing further neutrons, which collided with other nuclei, in a blossoming process of self-destruction. The reactions could be sustained for just a millisecond, and they fully exploited less than two pounds of the uranium atoms before the resulting heat forced a halt to the process through expansion. Uranium is one of the heaviest elements on earth, almost twice as heavy as lead, and two pounds of it amounts to only about three tablespoonfuls. Nonetheless the release of energy over Hiroshima yielded a force equivalent to fifteen thousand tons (fifteen kilotons) of TNT achieved temperatures higher than the suns, and emitted light-speed pulses of lethal radiation. More than 150,000 people died.