Oppenheimer's famous quote 'I am become Death' isn't really his. The ominous words come from Hindu scripture.

The Trinity Test made Oppenheimer think, "Now I am become Death, the destroyer of worlds." Three weeks later, the US dropped atom bombs on Japan.

• J. Robert Oppenheimer watched the first atom bomb explode and thought, "Now I am become Death."
• The famous quote is not an Oppenheimer original. The god Vishnu says it in Hindu scripture.
• Watch the moment Oppenheimer spoke those foreboding words on NBC, below.

J. Robert Oppenheimer once declared himself — or, possibly, the power of the atom bomb he had unleashed — "Death, the destroyer of worlds." The title is bleak but fitting.

"Uh, yeah. That's right," Alan Robock, a climatologist and leading expert on nuclear winter, told Insider. "But it wasn't just him."

Oppenheimer led a team of scientists to develop the world's first nuclear weapon in 1945, creating what Robock calls "the greatest danger that the world has been faced with."

Their race to get the bomb before the Nazis, an effort called the Manhattan Project, is the subject of Christopher Nolan's film "Oppenheimer," where the ominous death quote makes an appearance.

The real Oppenheimer uttered these words during an interview for a 1965 NBC broadcast on the decision to drop the atom bombs on Hiroshima and Nagasaki.

He was talking about the much smaller Trinity Test in the New Mexico desert just three weeks prior. It was the first atom bomb explosion, ever.

Watch Oppenheimer recall the moment of the historic detonation in the clip from the NBC documentary:

With a thousand-yard stare and plenty of long pauses, the physicist says:

"We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita. Vishnu is trying to persuade the Prince" — here Oppenheimer dabs the corner of his eye with a knuckle, as both eyes begin to glisten, seemingly with gathering tears — "that he should do his duty and, to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that one way or another."

The next person to speak in the documentary is physicist Kenneth Bainbridge, who directed the Trinity Test.

He described his sense of responsibility a little differently: "When I shook hands with Oppenheimer, I said 'Now we're all sons of bitches.'"

The scripture is about a god telling a soldier not to feel responsible for who lives and who dies

The fact that Oppenheimer turned to Sanskrit scripture at such a pivotal moment suggests that, at least in part, Hindu writings helped him make sense of the destructive power he was bringing into the world.

"He was obviously very attracted to this philosophy," Rev. Dr. Stephen Thompson, a Sanskrit scholar who has taught the Bhagavad Gita, told Wired in 2017.

In the line that Oppenheimer recalled, the god Vishnu is speaking to the warrior prince Arjuna, incarnated as his charioteer, Lord Krishna.

"Arjuna is a soldier, he has a duty to fight. Krishna, not Arjuna, will determine who lives and who dies, and Arjuna should neither mourn nor rejoice over what fate has in store but should be sublimely unattached to such results," Thompson told Wired. "And ultimately the most important thing is he should be devoted to Krishna. His faith will save Arjuna's soul."

Similarly, the Nolan film grapples with the question of how much Oppenheimer was (or wasn't) responsible for how the US used the atom bomb, and for the people it killed.

In the NBC interview, Oppenheimer discussed the justifications for developing the nuclear bomb — that it would end the atrocities of World War II and "save countless lives" — and the hope that it would never be used.

"On the whole we were inclined to think that, if it was needed to put an end to the war and had a chance of so doing, we thought that was the right thing to do," he said.