J. Robert Oppenheimer’s Grandson on What the Movie Gets Right and the One Scene He Would Have Changed

Moviegoers turned out in droves this weekend for writer-director Christopher Nolan's new film Oppenheimer, fueling an expectations-shattering domestic box office debut of $80 million. The three-hour-long biopic recounts the life story of J. Robert Oppenheimer (played by Cillian Murphy), the theoretical physicist widely known as the “father of the atomic bomb,” and has been praised by critics for its nuanced examination of a complicated historical figure.

The movie is based on Kai Bird and Martin J. Sherwin’s Pulitzer Prize-winning 2006 biography American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer, one of numerous accounts of Oppenheimer's life and legacy. But according to Oppenheimer's grandson, Charles Oppenheimer, the famous physicist's family has their own their own approach to depictions of him and additional nuance to include.

Charles was born near Santa Fe, N.M., in April 1975, after both his grandfather and grandmother, Katherine "Kitty" Puening Oppenheimer (played by Emily Blunt), had passed away. However, he says he grew up having a very open dialogue about his grandfather's work with his father, Peter Oppenheimer, who spent several years of his early childhood at Los Alamos during the Manhattan Project.

TIME spoke with Charles about what Oppenheimer gets right about his grandfather, what he would have changed, and the work he's doing to further Oppenheimer's legacy today.

This interview has been condensed and edited for clarity.

TIME: How was your grandparents' story told to you when you were growing up?

Charles Oppenheimer: Like most kids, I heard about my grandparents through my parents, and there was a marker at one point that stands out in my memory of speaking about Robert Oppenheimer being a famous person who had done his duty during World War II. He might have been a soldier, but his skills were in science, so he used science to do what he had to do during the war. But within the family, we had very open conversations. So my dad was always there if I had a question once I started hearing more about how we were related to a person that other people were talking about. I was always able to initiate a conversation and I do that to this day, especially with my father Peter.

So there was ongoing, open communication about who your grandfather was.

With a very big dividing line. Within the family, we absolutely talked about it as much as possible. With anyone outside of the family, my father doesn't discuss anything [about him] if he can avoid it.

Do you feel there are misconceptions about your grandfather?

There's such an incredible historical record of him. It's impressive, like every detail of every conversation of his spring break in 1924 is analyzed. If you have that much information and enough people writing and rewriting and interpreting, you can pick up any thread of meaning and narrative. The one that's developing right now is about as positive and as famous of an interpretation of him as you could have. And I find that being related to him and having insight into who he was doesn't always seem that interesting to other people. They're happy to ask a historian or a writer, and it's not necessarily true that my impression of his values is taken as the answer. So I kind of struggle with saying that I have a view of who he is and what he cared about and it not always getting across. That being said, I think with as much attention as is put on him, there is a large understanding of the complexity of the stuff he dealt with and the problems and opportunities of ushering science into the world.

Read more: Here's How Faithfully Oppenheimer Captures Its Subject's Real Life

You saw the movie. Were there parts that hit you the hardest, emotionally?

I was bracing myself for not feeling great about it, even though I talked to Chris Nolan and was very impressed by him. I saw him work on the set with an amazing intensity when I visited once or twice, and we had a great conversation. But I didn't know, am I going to love it? Am I going to hate it? I often have that reaction to biographies and pundits when they talk about my grandfather. I feel like they're missing something. And sometimes it really feels personal. Like when somebody wants to start a fight with you on the schoolyard, they'll talk about your family member. But during the movie, I found myself accepting and liking it. I thought it told a compelling story and I could just take it as art that was really engaging. I was really happy to have that reaction. I didn't expect it.

Were there parts that struck you as historically or emotionally inaccurate?

When I talked to Chris Nolan, at one point he said something roughly like, 'I know how to tell a story out of this subject. There are going to be parts that you have to dramatize a bit and parts that are changed. As family members, I think you're going to like some parts and dislike some parts.' That's probably led into my acceptance of the movie, even though I saw it very late, just when it came out. As a dramatized representation of the history, it was really largely accurate. There are parts that I disagree with, but not really because of Nolan.

The part I like the least is this poison apple reference, which was a problem in American Prometheus. If you read American Prometheus carefully enough, the authors say, 'We don't really know if it happened.' There's no record of him trying to kill somebody. That's a really serious accusation and it's historical revision. There's not a single enemy or friend of Robert Oppenheimer who heard that during his life and considered it to be true. American Prometheus got it from some references talking about a spring break trip, and all the original reporters of that story—there was only two maybe three—reported that they didn't know what Robert Oppenheimer was talking about. Unfortunately, American Prometheus summarizes that as Robert Oppenheimer tried to kill his teacher and then they [acknowledge that] maybe there's this doubt.

Sometimes facts get dragged through a game of telephone. In the movie, it's treated vaguely and you don't really know what's going on unless you know this incredibly deep backstory. So it honestly didn't bother me. It bothers me that it was in the biography with that emphasis, not a disclaimer of, this is an unsubstantiated rumor that we want to put in our book to make it interesting. But I like some of the dramatization. I thought Einstein's conversation with Oppenheimer at the end was really effective even though it wasn't historical.

What was your role, if any, in the movie?

The family policy around media, books, and what I'd call the cult of Oppenheimer, is not to participate in it. It's a business to write and talk about Oppenheimer, and the model that my dad chose is: 'It's not very classy, and I'm not going to be involved in publicly representing Oppenheimer in ways that other people do as a business.' But when I saw this movie was coming out, I said, 'Wow, that's going to be really big.' I also have a big interest in representing my grandfather's values for today's world. That's the most important thing in my opinion. So I reached out said, 'Hey, could I get involved?', and Chris Nolan was nice enough to give me a courtesy call through Kai Bird—whose book I just criticized. I do think American Prometheus is really good, I just had a complaint about that one part.

So Chris Nolan gave me a call. He had finished the script and he said, 'I have so much material with American Prometheus.' I explained that my dad probably would be unlikely to talk. But I don't think he needed input from the family. And as an artist, he obviously has every right to do that. You need art to tell this story. And it's just a fact that when somebody writes a biography about our family, we don't have input or the ability to make decisions. The chain of this movie was American Prometheus was published and then Nolan licensed it. I tried to give my perspective, but there wasn't any official involvement.

Is there anything you would have advised them to do differently, had you been asked?

I definitely would have removed the apple thing. But I can't imagine myself giving advice about movie stuff to Nolan. He's an expert, he's the artist, and he's a genius in this area. But one amusing family story is that, if I invited myself to the set, they would entertain me coming, which I did twice. And so one time I visited the set in New Mexico. I saw them film and, in that particular scene, Cillian Murphy walks into a room and part of his line was calling someone an 'asshole.' And when I went back to Santa Fe and told my dad, he was horrified. He said, 'Robert Oppenheimer never swore. He was such a formal person. He would never, ever do that.' And I was like, 'Well, it's a dramatization.' But I was worried that in the movie he would be this swearing, abusive guy. Anyway, I think he said one swear word in the movie and I just happened to be in the room. So there is a chance that if we had been consultants, we could have added some details and depth. But there's such a complete record. It was enough for Nolan to tell the story he intended to.

Did the movie help you come to any kind of deeper understanding of your grandfather?

When I saw how Nolan put this together, I was like, wow, there are thousands of pages of more details than what he put in there. But he was able to summarize it to the effect of: are we going to destroy ourselves as a species? That told as a story is really important. It's not exactly a revelation, but it's an important message. I always look at my grandfather's actual words instead of what other people said about him. And I think his advice is really relevant today, because he was right about how to manage atomic energy. If we had followed his actual hard policy proposals, we could have avoided an arms race right after World War II.

Robert Oppenheimer saw where we should go and he was right at that time. That really counts for a lot. It's not just the fact of like, ‘Oh, I regret something I did.' He put in effort to affect policy that could have literally changed history, and being overruled and discredited, which is what Nolan tells the story of, is important in that light. The way he told this story through [Lewis] Strauss’ perspective was really masterful.

There have always been two facts in tension: on the one hand, Oppenheimer helped create a weapon of mass destruction that was used to kill hundreds of thousands of people. On the other hand, the existence of nuclear weapons has succeeded as a deterrent for nearly 80 years, with superpowers like the U.S., Russia, and China avoiding war for fear of what would happen if those weapons again got into play. What are your thoughts on that complex legacy?

To me, that's the most interesting part and the most relevant today. The movie, while really good, had less emphasis than I would have put on the period of 1945 right before the bomb dropped to 1947, which was the time where we could have avoided an arms race. It is true that he ushered these weapons in, and then we went into an arms race, and we haven't destroyed ourselves. But the difference is him and [Niels] Bohr saw the arms race coming and said, ‘We really must avoid this.' It's not good enough that we just haven't died yet. It was a disaster that we got into an arms race and it was based on a fundamental misunderstanding of science, as illustrated in the scene they have in there with Truman where Oppenheimer had been telling people that if we don't co-manage this with our allies, which were the U.K. and Russia at the time, we're going to get into an arms race and it's going to be extremely dangerous.

The gut reaction from Truman and others was, let's just make as many of these bombs as fast as possible and we'll keep it secret and the Russians will never get the bomb. So you have a scientific expert that's telling the government, this is what we need to do, and you have the government doing the opposite. We got into an arms race not because of a hard-nosed, pragmatic understanding of we need to build these bombs, but a scientific misunderstanding that we could keep it secret. Robert Oppenheimer's deepest message is that the world had changed around the atomic bomb dropping. But it wasn't just atomic bombs, it was the fact that the scope of our technologies had increased to the point where we could destroy ourselves and we had to unite in a new way. And that's exactly what he said: Mankind must unite or we will perish. That's the message that we can bring into today's world.

You started the Oppenheimer Project to continue your grandfather's work today. Can you tell me a little bit about what the organization does?

Even though I spent a lot of time in this interview trying to correct some historical detail, you never win that discussion. But if you look at Robert Oppenheimer's values, what he wrote, what he said, how he led scientists, it’s clearly an amazing record. He led scientists to solve a hugely difficult technical problem under the threat of existential risk. And then he talked about, how do we manage the outcome of improving science and technology at that speed? He had a poetic way of talking. So when he spoke about what should we do about it, it wasn't just an engineered answer. He had a really deep, rounded view of it because of his education and interest. And what he said was, we need to unite in a new way—and his policy tried to put that in place.

It's exactly what we need to do today in the world. We can draw dots between the idea that if we hadn't gone into an arms race, we would have actually been able to use that scientific discovery for abundant nuclear energy. The same science could have made unlimited energy. We had a little bit of a push there of making it, but we were making bombs constantly at the same time, and that eventually sabotaged the public acceptance of nuclear energy. Now, we've gotten carbon output and climate change. So if we could use the idea of ushering in technology in an industrial scale effort to affect a really threatening problem, like climate change and lack of enough energy, we could apply the same type of effort that we had in the Manhattan Project towards today's problems. And it wouldn’t include creating a bunch of bombs, because that method of warfare stopped working in 1945. It doesn't work. Our institutions haven't caught up with that insight.