Continuity mistake: Near the end of the movie, when Oppenheimer is being interrogated in the small room, his lawyer is on the phone (we later find out it's Kitty). In a wide shot, he gives Oppenheimer the phone, and he puts it to his left ear. The next shot is a tight shot of Oppenheimer's face with the phone to his right ear.
Oppenheimer (2023)
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Directed by: Christopher Nolan
Starring: Matt Damon, Emily Blunt, Cillian Murphy
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More mistakes in Oppenheimer
J. Robert Oppenheimer: When I came to you with those calculations, we thought we might start a chain reaction that would destroy the entire world.
Albert Einstein: I remember it well. What of it?
J. Robert Oppenheimer: I believe we did.
Trivia: Josh Hartnett was one of the final 3 actors in the running to play Batman in Batman Begins, but withdrew. He later said he regretted his decision and wanted to work with Christopher Nolan, finally getting his chance here.
Answer: The short version is "no, not really". Much like in the film, the possibility was considered, a lot of calculations were done, and it was agreed by everyone privy to them that the chance was basically zero. Also like in the film: "what do you want from theory alone?" - it couldn't be guaranteed to be absolutely zero, but then the chance of almost anything happening is never absolutely zero. A 1946 report by three of the scientists stated: "whatever the temperature to which a section of the atmosphere may be heated, no self-propagating chain of nuclear reactions is likely to be started. The energy losses to radiation always overcompensate the gains due to the reactions."