When he set out to make "Oppenheimer," director Christopher Nolan opted not to use CGI for the film's central nuclear explosion. "It's difficult to make CG threatening," Nolan told IGN on 18 July. "So I first showed the script to Andrew Jackson, my visual effects supervisor, and said, I don't think that tool's going to work for us. So let's see if we can produce all of these effects using analog methods, from the very first imaginings that Oppenheimer has of the quantum world, of atoms, and how they would be interacting with strong force between them. Waves, particles, the duality of that." Ultimately, to show the size and scale of 1945's Trinity test, which was the first time a nuclear weapon had ever been detonated, he chose another route: building an actual bomb.
What Was the Trinity Test?
The Trinity test took place in Los Alamos, the New Mexico town that J. Robert Oppenheimer (played by Cillian Murphy in the film) and the United States government built together to support the Manhattan Project, a nationwide effort to construct a nuclear weapon. At 5:29 A.M. on 16 July, 1945, the Los Alamos team detonated an atomic bomb in the heart of the Jornada del Muerto desert for the first time in history.
The code name "Trinity test" was conceptualised by Oppenheimer, and references a line from a John Donne poem that begins, "Batter my heart, three person'd God." Oppenheimer was a known fan of the poet, as was his former lover Jean Tatlock, according to The New Yorker.
While the Manhattan Project team chose the New Mexico desert partly because it appeared empty, the Trinity test detonation had long-term effects on the surrounding areas. In years after the detonation, thousands of New Mexico residents developed cancers from radiation, and infant death rates spiked, among other consequences, per NGI. Over 70 years after the explosion, consequences are still being identified; for example, via The New York Times, a 20 July study that has yet to be peer-reviewed found that the fallout from the Trinity test may have reached 46 states.
Did "Oppenheimer" Use a Real Bomb?
The "Oppenheimer" team did craft a real bomb to film the Trinity test. Fortunately for everyone involved, though, their bomb was powered by petroleum, not atomic energy.
Instead of splitting atoms, per IGN, Jackson and special effects supervisor Scott Fisher used a blend of gasoline, propane, black powder, aluminium powder, and magnesium flares to craft an explosion that could reflect nuclear bombs' violent red-orange shades and unimaginable force. They also smashed ping-pong balls together and threw paint and glowing chemical solutions into the mix to add to the explosion's texture, according to IGN.
How Did "Oppenheimer" Film Its Trinity Test Explosion?
In order to bring the explosion to the big screen, the team also used some strategic filming tactics. Utilised a strategy called forced perspective, they filmed their bomb's explosion in an extreme close-up, creating an optical illusion that makes the detonation look much larger than it actually was, as per SYFY. In post-production, they layered different shots of the explosion over one another to simulate the massiveness of the world's first mushroom cloud.
To film the explosion, the "Oppenheimer" crew ventured far from Hollywood studios, out into the same desert where Oppenheimer's first bomb fell. "We were out there in the desert of New Mexico, just like the scientists of the Manhattan Project," Nolan told IGN. "We built the bunkers, we built the tower. We're out there at night preparing for these very large-scale explosive events that have to be conducted safely and with great care. So there's a tension, there's an anticipation in what we are doing as filmmakers that I think helps the actors, helps everybody understand, gain some small understanding of what must it have been like to be there that night, that early morning at the Trinity test."
Ultimately, Nolan wanted audiences to feel the visceral, terrifying power of the bomb. "'This can't be safe," he told The Hollywood Reporter, quoting a conversation he'd had with Jackson. "'It can't be comfortable to look at it. It has to have bite. It's got to be beautiful and threatening in equal measure.'"