Summary

• Oppenheimer and Einstein's conversation in the movie was not about Lewis Strauss, contrary to his paranoid belief. They were discussing the consequences of creating the atomic bomb and the potential destruction it could cause.
• Oppenheimer expresses his fear that the creation of the bomb will lead to a chain reaction of other nations developing nuclear weapons, ultimately destroying the world.
• The final scene of the movie showcases modern nuclear weapons being activated worldwide, reflecting Oppenheimer's realization that he unintentionally started a race to build destructive weapons that could ravage the planet.

The question of "What did Oppenheimer say to Einstein" is a running plot point in the Oscar-nominated Oppenheimer since a conversation between J. Robert Oppenheimer and Albert Einstein is frequently referred to. The Christopher Nolan-directed movie isn't just about the titular physicist leading a group of scientists to create the atomic bomb, it's about how Lewis Strauss attempted to publicly humiliate Oppenheimer and destroy his name after being embarrassed by him. The film is also about Oppenheimer's inner conflict regarding leading The Manhattan Project, and the scientist's conversation with Einstein in the final scene perfectly explains the movie's meaning.

In the movie, Lewis Strauss becomes immediately paranoid when Einstein ignores him following Einstein and Oppenheimer's conversation by the lake. Strauss is convinced that Oppenheimer uttered something negative about the chairman of the AEC to the celebrated scientist, and that's the very catalyst that strains Strauss and Oppenheimer's working relationship. In Strauss' last scene, Strauss' Senate aide tells the AEC chairman that maybe Einstein and Oppenheimer weren't talking about him, and that Strauss is being totally paranoid and narcissistic, and that's when the fabled conversation is finally unveiled.

Oppenheimer's Last Line To Einstein Explained

It Wasn't At All What Strauss Thought

It turns out that Oppenheimer didn't say anything negative about Strauss to Einstein whatsoever, and Strauss' name wasn't even mentioned. Instead, the two scientists were discussing the inner conflict Oppenheimer had during the creation of the atomic bomb and what the consequences may be now that the project has been completed.

Oppenheimer tells Einstein that he fears that the creation of the bomb will start a chain reaction where other nations attempt to outdo the atomic bomb, creating endless amounts of nuclear weapons, and as a result, destroying the world. What follows is the movie's final line when Einstein asks, "What of it?" to which Oppenheimer responds, "I believe we did."

What Oppenheimer Really Meant When He Said "I Believe We Did" To Einstein

They Started Something Incredibly Damaging To The Planet

The final moment of Oppenheimer is a mini-montage of modern nuclear weapons being activated across the world and Earth being torched, which is what Oppenheimer meant by "I Believe We Did," and exactly what he was afraid of. Oppenheimer's reasoning behind leading The Manhattan Project was that he'd rather have a potentially world-ending bomb in the hands of the U.S. government than the Nazis so he raced against to build the bomb and won. However, while creating the bomb, he realized that he had simply started a chain reaction where every nation would have nuclear weapons of their own.

Instead of building a bomb to end the war, Oppenheimer sped up a planet-ravaging race in nuclear weapon building, as every other country learned how to build bombs with atoms and hydrogen. After the events of Oppenheimer, he became an advocate against the creation of nuclear weapons, including the hydrogen bomb, which was created by Oppenheimer's Edward Teller, the Hungarian scientist who betrayed him during his hearing. While "I believe we did" is such a haunting line, especially as the end-of-the-world visual follows, the sequence essentially adapts the scientist's most famous quote: "Now I become death, destroyer of worlds."