‘Now I Am Become Death’: The Legacy of the First Nuclear Bomb Test

Since the Trinity test 75 years ago, at least eight countries have conducted more than 2,000 nuclear bomb tests, said Jenifer Mackby, a senior fellow at the Federation of American Scientists. More than half of those tests have been conducted by the United States, a legacy of the Trinity explosion, as the United States and several other countries have continued to refuse to ratify the treaty prohibiting nuclear weapon test explosions.

“You could say it unleashed the nuclear age, really,” Ms. Mackby said. “It unleashed a whole new class of destruction.”

Many of the scientists who witnessed the blast quickly realized the “foul and awesome” power they had set free, according to historians.

Mr. Oppenheimer said a Hindu scripture ran through his mind at the sight of the explosion: “Now I am become Death, the destroyer of worlds.”

Kenneth T. Bainbridge, the test director, was less poetic.

“Now we are all sons of bitches,” he said.

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The goal of the test was to see if the military could harness plutonium into a weapon that would destroy whole cities, said Alex Wellerstein, a science historian at the Stevens Institute of Technology in Hoboken, N.J., who studies the history of nuclear weapons.

The effects of radiation were not well understood by most scientists on the project at the time, according to historians, and the preparations that were made to keep civilians safe reflected that ignorance.

They placed crude monitors around the small towns within 40 miles of the testing site. A scientist who was seven months pregnant and her husband, who was also a scientist, were sent to a motel in one of the towns with a Geiger counter, a device used to detect radioactive emissions, to measure the radiation. If the needle hit a certain mark, she was instructed to alert officials so that they could evacuate the town, Professor Wellerstein said.

Officials did not warn any of the residents — many of them ranchers, Navajos, Mexican settlers and their descendants who raised cattle and drank water from cisterns — about the test. Should anyone ask about the blast, officials had proposed several cover stories, including telling the public that a remote ammunitions depot had exploded, Professor Wellerstein said.

“They took some effort” to protect the public, he said. “Would we consider it adequate today? No, not at all. It’s not considered adequate to set off a nuclear bomb, not tell anyone about it and set up a pregnant scientist in a motel with a Geiger counter to monitor radiation.”