Nuclear Tests Marked Life on Earth With a Radioactive Spike
On the morning of March 1, 1954, a hydrogen bomb went off in the middle of the Pacific Ocean. John Clark was only 20 miles away when he issued the order, huddled with his crew inside a windowless concrete blockhouse on Bikini Atoll. But seconds went by, and all was silent. He wondered if the bomb had failed. Eventually, he radioed a Navy ship monitoring the test explosion.
“It’s a good one,” they told him.
Then the blockhouse began to lurch. At least one crew member got seasick—“landsick” might be the better descriptor. A minute later, when the bomb blast reached them, the walls creaked and water shot out of the bathroom pipes. And then, once more, nothing. Clark waited for another impact—perhaps a tidal wave—but after 15 minutes he decided it was safe for the crew to venture outside.
The mushroom cloud towered into the sky. The explosion, dubbed “Castle Bravo,” was the largest nuclear-weapons test up to that point. It was intended to try out the first hydrogen bomb ready to be dropped from a plane. Many in Washington felt that the future of the free world depended on it, and Clark was the natural pick to oversee such a vital blast. He was the deputy test director for the Atomic Energy Commission, and had already participated in more than 40 test shots. Now he gazed up at the cloud in awe. But then his Geiger counter began to crackle.
“It could mean only one thing,” Clark later wrote. “We were already getting fallout.”
That wasn’t supposed to happen. The Castle Bravo team had been sure that the radiation from the blast would go up to the stratosphere or get carried away by the winds safely out to sea. In fact, the chain reactions unleashed during the explosion produced a blast almost three times as big as predicted—1,000 times bigger than the Hiroshima bomb.
Within seconds, the fireball had lofted 10 million tons of pulverized coral reef, coated in radioactive material. And soon some of that deadly debris began dropping to Earth. If Clark and his crew had lingered outside, they would have died in the fallout.
Clark rushed his team back into the blockhouse, but even within the thick walls, the level of radiation was still climbing. Clark radioed for a rescue but was denied: It would be too dangerous for the helicopter pilots to come to the island. The team hunkered down, wondering if they were being poisoned to death. The generators failed, and the lights winked out.
“We were not a happy bunch,” Clark recalled.
They spent hours in the hot, radioactive darkness until the Navy dispatched helicopters their way. When the crew members heard the blades, they put on bedsheets to protect themselves from fallout. Throwing open the blockhouse door, they ran to nearby jeeps as though they were in a surreal Halloween parade, and drove half a mile to the landing pad. They clambered into the helicopters, and escaped over the sea.
[Read: The people who built the atomic bomb]
As Clark and his crew found shelter aboard a Navy ship, the debris from Castle Bravo rained
