The Untold Truth Of Christopher Nolan's Oppenheimer

Christopher Nolan broke out in 2000 with "Memento," and helped reboot the Caped Crusader in 2005 with "Batman Begins." He's the rare director who's arguably never made a bad movie, and audiences know that a ticket to a Nolan film will deliver heart-stopping suspense, stirring performances, and plenty of captivating drama. His 2023 effort, "Oppenheimer," however, is unlike any film he's ever made: A biopic centered on the man who invented the first atomic bomb.

Led by Cillian Murphy in the title role, the film's all-star cast includes the likes of Robert Downey Jr., Matt Damon, Florence Pugh, and Emily Blunt. The film has left critics stunned, with Lindsey Bahr of the Associated Press dubbing it "a spectacular achievement in its truthful, concise adaptation," and it was no easy feat to assemble. It may in fact be Nolan's most epic film yet, but if you think you knew everything about it, think again. From the ins and outs of filming the movie's most jaw-dropping scenes to problems between the actors on set, this is the untold truth of Christopher Nolan's "Oppenheimer."

With director Christopher Nolan's insistence on zero CGI, it's fair to wonder how the film was able to capture the test detonation of the first nuclear device in what was known as the "Trinity Test." But contrary to much speculation, Nolan didn't actually film the dropping of a real nuclear bomb, though he did manage to recreate its effects with state-of-the-art pyrotechnic technology. 

In an interview with Total Film (via SyFy), Nolan talked about how they filmed the climactic test of the first nuclear device called Trinity, discussing how they used forced perspective to turn an otherwise ordinary explosion into a nuclear one. "We don't call them miniatures; we call them 'big-atures,'" Nolan said. "We do them as big as we possibly can, but we do reduce the scale so it's manageable. It's getting it closer to the camera, and doing it as big as you can in the environment."

Though they didn't use a real nuke or CGI, what they did use was a massive amount of gasoline and propane. Additional quantities of aluminum powder and magnesium were also used to create the brilliant flash of light that accompanies a nuclear detonation, which was key to the effect. "We really wanted everyone to talk about that flash, that brightness. So we tried to replicate that as much as we could."

Christopher Nolan is no stranger to working with actors who will physically transform themselves for a role. Still, he probably didn't expect to see his "Oppenheimer" star Cillian Murphy make the kind of radical body changes he did for the role — after all, the renowned physicist wasn't any kind of superhero. But Nolan was surprised when he learned that Murphy had dropped an unhealthy amount of weight for the role to better embody J. Robert Oppenheimer physically.

Murphy really wanted to capture the likeness of the famed Oppenheimer, who was known for his thin frame. "[He] had a very distinct physicality and silhouette, which I wanted to get right. I had to lose quite a bit of weight," he said in an interview with The New York Times. "He was very slim, almost emaciated, existed on martinis and cigarettes." 

To achieve the look, Murphy put himself to the test, often refusing to eat at all. "You become competitive with yourself a little bit which is not healthy," Murphy told The Guardian. "I don't advise it." The all-consuming aspect of the production helped, too. "I was running on crazy energy," he said in an interview with IndieWire. "I went over a threshold to where I was not worrying about food or anything. I was so in it, a state of hyper something. But it was good because the character was like that. He never ate."

To make "Oppenheimer," Christopher Nolan didn't just look to history, but also to lessons he learned in his earlier productions. And perhaps surprisingly, it was an experience during the filming of "The Dark Knight" that gave him the inspiration and experience with effects to create the incredible Trinity Test sequence. "I think I've done a lot of large-scale practical effects, they come together on 'Oppenheimer' in the Trinity Test which we knew had to be a showstopper," he said in a chat with Jake's Takes while doing promotion for the film. "I think that the single most influential for me was that truck flip [in "The Dark Knight"]," Nolan revealed. 

Though the two sequences are vastly different, with very little in common story-wise (after all, one takes place within a comic book universe, the other in WWII-era New Mexico), the one thing they do share is the fact that nobody thought they could be pulled off without significant CGI help. "At first everybody felt that it was too difficult and too complicated to do for real." But after mulling it over with his carefully selected team of effects people, the skepticism faded. "I learned that if you challenge people and you come to them earlier — and said to them right from the beginning, 'let's show the first atomic bomb without using computer graphics. Let's find real ways to photograph this so the audience can get that particularly hypnotic and dangerous feeling that you would have had watching the first example of nuclear fire that had ever been unleashed."

In a biopic like "Oppenheimer," authenticity is key, particularly as a period piece that takes place nearly 80 years ago. That means period-specific sets, props, and wardrobe, and with the famously meticulous Christopher Nolan in the director's chair, you know special attention is going to be given to these details. Well, when it came to capturing the look of Oppenheimer himself, that meant more than having Cillian Murphy lose weight, but also recreating his uniquely identifiable "porkpie" hat that he wore everywhere, which shows up in a number of iconic portraits.

Unfortunately for Nolan and his crew, this hat wasn't something that could simply be purchased off the shelf, or even loaned out from a Hollywood prop house. In fact, getting the right hat proved so troublesome that the filmmaker opted to have the accessory custom-made just for the film. "It was very difficult to build it," Nolan revealed to the Los Angeles Times. "The brim can't be too stiff or too floppy. It's like artfully disheveled hair — it takes a lot of fussing, and I often fussed with the hat just before a take."

There was a time in the early 2000s when actor Josh Hartnett was one of the hottest up-and-coming stars in Hollywood. In addition to starring alongside Ben Affleck and Kate Beckinsale in Michael Bay's "Pearl Harbor," he was in a modern-day retelling of "Othello" and the war movie "Black Hawk Down." Though he had his share of struggles — including the disastrous Harrison Ford cop comedy "Hollywood Homicide" — he was still something of a hot name when Christopher Nolan started work on "Batman Begins." 

Before Christian Bale entered the picture, Hartnett was offered the lead role, but ultimately declined, afraid that a superhero movie could hurt his burgeoning career in the days before the genre had really hit it big. Well, Nolan was reportedly miffed at Hartnett passing on the offer, and the actor realized too late that it might have been a bad move. "I've definitely said no to some of the wrong people," the actor told Playboy (via /Film). "I learned my lesson when [writer-director] Christopher Nolan and I talked about 'Batman.' I decided it wasn't for me. Then he didn't want to put me in 'The Prestige.' They not only hired their Batman for it, they also hired my girlfriend at the time."

While Nolan went on to become the biggest director around, and often cast actors over and over — like Michael Caine, Gary Oldman, and Christian Bale — Hartnett never got a second chance. Until now, that is.

With one of the most sprawling A-list casts ever assembled for a single film, "Oppenheimer" is like few biopics ever made. With so much talent together in one place, you might think there would have been a clash of egos, but from all accounts that doesn't appear to have been the case. In fact, during the production of the film, when they were all assembled in New Mexico for location shooting, most of the cast actually lived together. All cooped up together, actress Emily Blunt described the experience as being like a "summer camp" while speaking to People Magazine. 

"We were all in the same hotel in the middle of the New Mexican desert," Blunt reminisced. "We only had each other. Me and Matt [Damon] were roommates and we were like, 'Let's go to have dinner.'" There was one notable exception to the cast get-togethers, and that was the movie's principal star, Cillian Murphy.  "The sheer volume of what he had to take on and shoulder is so monumental," recalled Blunt. "Of course he didn't want to come and have dinner with us." Damon echoed Blunt's sentiment, saying, "He couldn't. His brain was just too full."