AT two seconds past 8:16 on the morning of Aug. 6, 1945 — 79 years ago today — the world's second atomic bomb exploded 1,938 feet (591 meters) directly above the Shima Surgical Clinic in downtown Hiroshima, Japan. Today is marked as a solemn day of remembrance in Hiroshima and Japan, and just as it is every year, the anniversary has also been acknowledged by well-meaning but patronizing messages of peace from the rest of the world. Centuries or millennia from now, when some voyagers from another part of the galaxy find their way to this dusty corner of the cosmos to gaze upon the fossilized corpse of this civilization, the date will be marked as the moment we destroyed ourselves.

Mankind's brightest minds had been working up to that moment for about seven years by the time the bomb named 'Little Boy' exploded over Hiroshima. Almost the very first thought inspired by the discovery of nuclear fission in December 1938 was 'bomb.' German chemists Otto Hahn and Fritz Strassman identified fission on December 19. Austrian physicists Lise Meitner and Otto Frisch published a paper explaining it theoretically the following month. About three weeks later, in February 1939, Hahn and Strassman published their second paper, pulling all the early calculations together to reach a dependable conclusion: 'Hey, this would make a good bomb.'