Most of the performances have a bit of an "old movie" feeling, with the actors snapping off their lines and not moving their faces as much as they would in a more modern story. A lot of the dialogue is delivered quickly, producing a screwball comedy energy. This comes through most strongly in the arguments between Robert and Kitty about his sexual indiscretions and refusal to listen to her mostly superb advice; the more abstract debates about power and responsibility between Robert and General Groves, and the scenes between Strauss and a Senate aide (Alden Ehrenreich) who is advising him as he testifies before a committee that he hopes will approve him to serve in President Dwight Eisenhower's cabinet.
But as a physical experience, "Oppenheimer" is something else entirely—it's hard to say exactly what, and that's what's so fascinating about it. I've already heard complaints that the movie is "too long," that it could've ended with the first bomb detonating, and could've done without the bits about Oppenheimer's sex life and the enmity of Strauss, and that it's perversely self-defeating to devote so much of the running time, including the most of the third hour, to a pair of governmental hearings: the one where Oppenheimer tries to get his security clearance renewed, and Strauss trying to get approved for Eisenhower's cabinet. But the film's furiously entropic tendencies complement the theoretical discussions of the how's and why's of the individual and collective personality. To greater and lesser degrees, all of the characters are appearing before a tribunal and bring called to account for their contradictions, hypocrisies, and sins. The tribunal is out there in the dark. We've been given the information but not told what to decide, which is as it should be.