Pacific: The Ocean of the Future. Simon Winchester

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      Infamously disdainful of the supposed dangers of atomic fallout, the nuclear accident survivor Alvin Graves ordered the fateful firing of the Castle Bravo thermonuclear weapon, the biggest of all American nuclear tests. National Nuclear Security Administration.

He eventually became well enough to be appointed—though at this remove, and considering what then happened, it is surely right to wonder at the wisdom of his appointment—scientific director of the Castle series of thermonuclear bomb tests. He swiftly became the most enthusiastic advocate of these new weapons—not least because he was well aware that the Soviet Union’s nuclear program was catching up fast.8 Once he arrived at the Enewetak headquarters of what were now called the Pacific Proving Grounds, he made one thing abundantly clear to his staff: since he had survived the very worst that the atom could throw at him, he would stop at nothing to detonate the Bikini-based fusion device that was now in his care.

      The bomb designated for the Castle Bravo detonation was an innocent-looking steel cylinder fifteen feet long, four feet in diameter. It looked rather like a large propane tank. It had been designed at Los Alamos, where, to suggest its innocence of purpose, it had been given the code-name the Shrimp. It had been shipped in great secrecy—lights off at night, aircraft and destroyers keeping pace with the cargo ship—to Enewetak in February, and was taken by barge to Bikini, with tarpaulin wraps to prevent the unauthorized curious glimpsing its size and shape. There it was suspended from the ceiling of a large shed, called the shot cab, that had been erected on an artificial island built on a reef off Nam Island, at the very northern tip of the atoll. A causeway connected the shot cab with dry land; the wires that would lead to the electronic firing bunker snaked across the sandbanks and coral reefs and past the Bikinians’ now long-abandoned houses, to the tiny sliver of Enyu Island, twenty miles away.

      At the end of February, all staff members were evacuated from Bikini and all ships were removed from the lagoon. Only the firing crew, nine men buried beneath concrete a dozen feet belowground, stayed behind.

      Before the firing button was pressed, there were two serious uncertainties. The first was just how big this bomb would be. The Ivy Mike explosion of sixteen months before had been a thumping ten megatons, spectacular and memorable—and when that bomb blew up, it did so exactly as powerfully as the physicists had predicted. But Castle Bravo was using a solid rather than a liquid source of hydrogen—the hydrogen that would be compressed with such force and heat as to make it undergo fusion, and release the massive amount of energy that would cause the explosion. The solid compound in the new bomb was lithium deuteride, an amalgam of lithium and isotopic hydrogen. And no one knew exactly how much hydrogen it would release, or how big the detonation would be.

      The testers would soon find out. And because of the other uncertainty—over the weather and, more specifically, the direction of the winds on detonation day—a great many others would find out as well.

      For several days before the test date, the winds had been blowing in what was considered an acceptable direction: toward the west, where they would carry any radioactive fallout over an empty expanse of sea. The United States had declared a 57,000-square-mile “danger area” in an official Notice to Mariners, suggesting that craft keep away if possible, but without stating why. Had matters stayed as they were, the detonation would have caused little obvious harm.

      However, on the night before the planned blast, February 28, the wind began to veer toward the east, away from this designated danger zone. Matters then got worse. As the sun inched up on the morning of the shot, meteorologists started reporting that at upper altitudes a powerful gale was now blowing directly from Bikini and toward the other populated atolls of the Marshalls, most notably in the direction of Rongelap, a hundred miles away, and forty miles farther on toward Rongerik, where the Bikinians had first been sent. On Rongerik there was still an American duty weatherman; he later told the newspapers that the wind, even at sea level, had been blowing directly at his island home from the west—from the direction, in other words, of Bikini, where they were counting down to firing the bomb.

      Alvin Graves was aboard the command ship, the USS Curtiss, a venerable seaplane tender that was well accustomed to bombs, since she had been damaged by and had survived both the Pearl Harbor attacks and then a kamikaze strike in mid-Pacific. And though this bomb was a military device, Graves, the civilian chief of the project, had been given ultimate authority over the army general who was in command of the task force operating the weapon.

      Graves was told of the wind direction and knew that radiation would spread downwind and contaminate, at the very least, Rongelap Atoll. But he had his orders, which were to proceed with the test without delay. Moreover, whatever the wind direction might be, no one had any idea how much radiation would be produced. Not that this was strictly relevant, of course, since Graves still cleaved robustly to his views about the malingerers who had concocted all this fuss about radiation being so terribly dangerous.

      So he gave his orders to activate the automatic firing mechanisms. The Castle Bravo bomb should be allowed to explode. The men in the bunker took cover, and then pressed the brilliant red firing button.

      At 6:45 a.m. on that clear, windy, blue-sky Pacific morning, it was as if the world had suddenly stopped, blinded by a vast white light of an intensity never before experienced. The iron gates guarding some terrible inferno seemed to clang wide open and unleash a ball of fire and shock waves and roarings of unimaginable speed, violence, and loudness. A white fireball four miles across was created in less than one second. A minute later, a cloud of debris ten miles tall and seven across rocketed into the sky. Ten minutes on, it was twenty-five miles tall and sixty СКАЧАТЬ