A freestanding concrete-block seawall stood between the bunker and the lagoon, engineered to help protect the men against a potentially massive tidal wave. Everything but the bunker's entrance had now been buried under ten feet of sand. The bunker, code-named Station 70, was an odd sight to behold, squat, rectangular, with blast-proof doors and three-foot concrete walls. Salt-loving sea lavender plants covered the lowlands, and little penny-sized geckos scampered across wet white sands. An intense tropical rainfall the night before had left the fronds on the coconut palms and pandanus trees soaking wet. The Castle Bravo bomb would likely explode with one thousand times the force of the atomic bomb dropped on Hiroshima in August 1945, and yet it weighed just a little more than twice as much. Nuclear weapons in particular were getting smaller and more efficient in ways that scientists could not have imagined a decade before. Thanks to recent advancements in defense science, by 1954 machines were being miniaturized at an astonishing rate. With a predicted yield of 6 megatons, Castle Bravo would deliver twice as much power as all the bombs dropped on Germany and Japan during World War II together, including both atomic bombs. No human being had ever before been this close to the kind of power this bomb was expected to deliver. In a little more than two hours, the most powerful bomb in the history of the world to date was going to be detonated just nineteen miles away. On one end of Bikini Atoll, ten men, each with a top secret Q clearance for access to nuclear secrets, waited inside a concrete bunker, facing an unknown fate. Because the bomb's existence had been kept secret from the American public, the test that the scientists were about to witness had been given a code name. Air Force bomber and dropped on an enemy city like Moscow. The machine was a thermonuclear, or hydrogen, bomb, small enough to be loaded onto a U.S. But it was built anyway, and now it was about to explode. Enrico Fermi and Isidor Rabi, both Manhattan Project scientists, called this machine an 'evil thing,' and they told President Truman it should never be created. Some of the scientists in the group had warned of this moment. local time on Bikini Atoll in the Marshall Islands, a small island chain in the vast Pacific Ocean, 2,650 miles west of Hawaii.

One day in the winter of 1954, a group of American scientists found themselves entering into a time when a machine they had created could trigger the end of the world.

The Pentagon's Brain by Annie Jacobsen