Yes, Cillian Murphy Really Learned How to Give a Physics Lecture in Dutch for ‘Oppenheimer’

In bringing J. Robert Oppenheimer to life, Cillian Murphy took actorly commitment to the next level.

The Irish actor, 47, has been praised for embodying the titular role in Oppenheimer, Christopher Nolan’s retelling of the creation of the atomic bomb. A new book from Jada Yuan, Unleashing Oppenheimer: Inside Christopher Nolan’s Explosive Atomic-Age Thriller (available for purchase now), includes details about the lengths to which Murphy went to do so. 

For example, there’s no trickery in the film’s early scene featuring the American physicist as he launches into an academic lecture, unexpectedly, in fluent Dutch. 

“It’s a small scene,” Murphy said in interviews published in Unleashing Oppenheimer, but nonetheless one he was “dreading.”

“I remember talking to Chris in preproduction and saying, ‘Chris, what do you want to do about this Dutch scene?’ And he said, ‘What are you going to do about this Dutch scene?’”

The Peaky Blinders star added that Nolan always “works at the top of his game, so he expects everyone else to do their work, to do their due diligence.” Murphy previously collaborated with the Oscar-nominated writer-director on 2010’s Inception, 2017’s Dunkirk and as Batman villain Scarecrow in the Dark Knight trilogy of films. 

Nolan’s regular cinematographer Hoyte van Hoytema, who is Dutch, ended up assisting Murphy. Although the exact lectures that Oppenheimer gave at the Netherlands’ Leiden University in 1928 have been lost, Yuan writes, the producing team took one of his later lectures on quantum mechanics and translated a portion into Dutch. 

As the actor revealed to Deadline in July, he asked van Hoytema to record himself reading the words aloud. “He recorded it and then I slowed it down so I just learned it phonetically over three months.” 

In his interviews with Yuan, he said the snippet of Dutch heard in Oppenheimer is “one of those things that I will never forget because I did it so many times.” 

“I can still say it,” Murphy added, although he admitted that’s the extent of his grasp of the language. 

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Murphy’s Oppenheimer costars have spoken out about his commitment to the role, which included researching theoretical physics and Oppenheimer’s role as director of the Manhattan Project’s Los Alamos Laboratory. 

Robert Downey Jr., who in the film plays Atomic Energy Commission chairman Lewis Strauss, told PEOPLE in July that he had “never witnessed a greater sacrifice by a lead actor,” adding that learning another language was one of Murphy’s many challenges. 

“We’d be like, ‘Hey, we got a three-day weekend. Maybe we’ll go antiquing in Santa Fe. What are you going to do?’” he recalled asking Murphy. “’Oh, I have to learn 30,000 words of Dutch. Have a nice time.’”

Downey Jr. added, “He knew it was going to be a behemoth ask when Chris called him. But I think he also had the humility that is required to survive playing a role like this.”

Emily Blunt, who plays Oppenheimer’s wife Kitty, called Murphy’s work “monumental” in an exclusive interview with PEOPLE. While the rest of the New Mexico-set production felt like “summer camp,” she said, “of course he didn’t want to come and have dinner with us.”

Based on the 2005 biography American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Martin J. Sherwin, Oppenheimer is 2023’s third highest grossing movie and broke the record for highest-grossing biographical movie of all time.