Oppenheimer is also a very intense, enigmatic mysterious human being...polymath who loves French poetry and the novels of Ernest Hemingway. And he acquired a fascination with Hindu mysticism and the Hindu scriptures, the Bhagavad Gita. And he got Arthur Ryder, the only Sanskrit scholar at Berkeley University to tutor him in Sanskrit so that he could read the Gita in the original. Our book is 700 pages long and deals with his odyssey as a quantum physicist, but also his love life, his politics, and both the building of the bomb, but also what happened to him in 1954.

From being associated with Left-wing causes in the 1930s, Oppenheimer plunged into the Manhattan Project. How did he reconcile himself intellectually to it?

It came very much out of his political Left-wing political views. He feared the rise of Fascism. He was of Jewish ancestry, but not a practising Jew. He gave money to help rescue Jewish refugees from Germany. He feared that German physicists were going to give Hitler an atomic bomb, that Hitler would be able to win the war, and this would be a terrible outcome, a victory for fascism around the world. So he felt this was necessary to do.

What did he think of the use of the bomb?

He had very mixed emotions. By the spring of 1945, Germany was defeated. And that spring, some of the physicists and scientists at Los Alamos held an impromptu meeting to discuss the future of the gadget, and to ask why are we working so hard to build this terrible weapon of mass destruction when we know the Germans are defeated and Hitler is dead, and the Japanese can’t possibly have a bomb project?

Oppenheimer stepped forward at one point and said, I just want to remind you all that the war is not over. The Japanese still fight on. And he said I am reminded of the one question that Niels Bohr, the great Danish physicist asked me when he arrived here in Los Alamos on the last day of 1943. He had asked Robert, “Tell me, is it big enough? Is this gadget you are building big enough to end all wars?” He’s essentially making the argument that if we do not demonstrate the power and destructiveness of this weapon in this war, then the next war is going to be fought by two or three adversaries, all of whom will be armed with nuclear weapons. And that would be Armageddon…And yet he was terribly troubled as well. He felt enormous empathy for the victims on the ground.

After 1945, Oppenheimer appears to have become more concerned. What form did it take?

He read the accounts of what had happened in Hiroshima and Nagasaki and understood that tens of thousands of people had been instantly burned to death. And he actually plunged into a deep depression right after the two bombings. Then he recovers, but almost immediately, begins to speak out. So in October of 1945, just three months after Hiroshima, he gives a speech in which he says, you may think that this weapon was expensive because it cost $2 billion, but actually, it is cheap. And any country, however, poor or rich, if they decide they want to acquire these weapons, they will be able to do so. And he says these are weapons for aggressors. These are weapons of terror. They are not defensive weapons. And they were used on an essentially already defeated enemy. That’s an extraordinary thing for him to say just three months after Hiroshima. But he had come to understand from conversations with people in Washington that the Japanese were actually very close to surrendering. He spent the rest of his life trying to persuade policymakers that we should create an international arms control regime.

What drew him to the Gita? Did he have any other connections with India?

I think what drew him to the Gita was a fascination with mysticism and with some of the philosophical notions in the Gita that were sort of parallel to quantum about the nature of the world. And that famous line that he used to describe what he thought when he saw the Trinity explosion — “I am death, destroyer of the world” — some Sanskrit scholars, as I understand it, think that the more accurate translation would be “I am Time, destroyer of worlds”. He is a quantum physicist, so he is trying to understand time and space, and these are issues that the Gita sort of addresses on some level. After he was humiliated in 1954, Prime Minister [Jawaharlal] Nehru offered him to come to India and become a citizen... But I don’t think Oppenheimer considered it seriously because he was a deeply patriotic American.

Tell us about your collaboration with your co-author, Martin Sherwin on the book.

Marty Sherwin signed a contract with Knopf in 1980 to do a biography of Oppenheimer. He did incredible research, and eventually accumulated 50,000 pages of archival documents. But Marty got what is called biographers disease, which is when you can’t stop researching. And you never start writing because there’s always more research. Marty came to me in about 1999, and he said, Kai, you need to join me on this project, and if you don’t, my gravestone is going to read: He took it with him. We signed a new contract in 2000, and then I started to write the first chapters on the childhood years and this instigated Marty to start writing. And we went back and forth, and it turned into a wonderful friendship and collaboration. But it still took almost five years for the book to come out.

And when it did it, it was very well reviewed. And it won the Pulitzer in 2006. And, even before the Pulitzer, it was auctioned for film, but nothing ever happened in Hollywood. But then in September 2021, I got a phone call saying that Christopher Nolan wanted to speak to me. And it emerged that he had been given the book early in 2021, and I think he fell in love with it and sat down that spring and summer and wrote a 180-page screenplay without talking to us. He just wanted to see if he could do it. Before they started filming, Nolan did share with me the screenplay, so I had a chance to review it and make sure that there were no historical errors. Unfortunately, tragically, just about two weeks after we learned that Nolan was doing the film, Marty died at the age of 84.

What did you think of the film?

When I first saw the film, in May, Nolan flew me out to Los Angeles, and the next morning, he met me at 10am and escorted me into this empty, huge IMAX theater. And he sat me down right in the middle of the best seat, walked away, and left me alone. He sat on the far edge of the row and gave me the privacy to watch this thing unfold over three hours. And it brought me to tears at times. I kept thinking, what would Marty think of this scene? Or that? And it was just stunning. I was very moved. I have seen it four times now. It’s very layered, complicated, fast-moving, and heavy on dialogue, but artistically beautiful. It’s a stupendous cinematic achievement, and, yet, as the biographer speaking, I am just stunned that Nolan’s cinematic version of Oppenheimer is actually quite historically accurate.

Why is Oppenheimer relevant today?

His story is incredibly relevant because we are still trying to live with the bomb. Just look at the war in Ukraine and the way Vladimir Putin has been threatening to use tactical nuclear weapons in Ukraine. The story is not over. And it may end badly still, these weapons could still be used again.

But it’s also relevant because what happened to him in 1954 explains America’s current divisive politics. You know, the phenomena of [Donald] Trump and his anti-intellectualism, right-wing, populous, xenophobic, paranoid style of politics comes straight out of the McCarthy era. And indeed, Joe McCarthy’s chief counsel was Roy Cohn and Cohn later became Trump’s personal lawyer and taught him this paranoid style of politics. So Oppenheimer’s story is also about the crazy anti-intellectual strain of politics in America today.

And it’s relevant because his life as a scientist sheds light on our world today which is drenched in science and technology, and we are struggling to figure out how to absorb this technology and make it part of a humane society. So we are on the verge of yet another revolution in artificial intelligence (AI). And this is going to have dire consequences for employment, and our whole culture, it raises issues of privacy. And people are talking about AI being used to trigger the use of nuclear weapons. And that’s a frightening prospect

I hope it jump-starts a serious civil conversation, not only here in America, but around the world and in places like India that have nuclear weapons, a huge tech industry, and are facing the same philosophical questions with regard to this.