How do you end up nervously joking about maybe ending the world?
What in the world moves decent, intelligent, careful, and thoughtful people — and many of the people working on the atomic bomb, including Oppenheimer himself most of the time, were decent, intelligent, careful, and thoughtful — to behavior that from the outside can look gravely irresponsible?
Ordinary people would presumably not agree to a scientific experiment with even a very small chance of destroying the world. That wouldn’t seem like an acceptable risk. We would want researchers to wait until they understood the science better and could be wholly confident that their project wouldn’t ignite the atmosphere.
Much of the answer lies in the geopolitical competition that the Manhattan Project scientists believed themselves to be in with the Nazis. The terrible logic of building the bomb was that if Hitler built it first, he could hold the whole world hostage and spread an ideology of unparalleled evil and destructiveness, so the only thing that mattered was getting there first.
That was the conviction in which the Manhattan Project was initiated. Of course, it eventually became clear that the Nazis were never close to completing an atomic bomb. In fact, by the time of the Trinity test — on July 16, 1945 — Germany had already surrendered. Even if taking risks with the fate of every single person alive was justified to stop Hitler, it had stopped being justified months before the Trinity countdown began.
If Oppenheimer leaves you with more questions than answers, Richard Rhodes’s The Making of the Atomic Bomb is a book I highly recommend to learn more about the Manhattan Project, the extraordinary personalities driving it, and how they made the decisions that eventually introduced atomic weapons to the world. It’s where I found my answer to this question, though it’s far from a fully satisfying one.
That answer is that they were too busy thinking about how to build the bomb to revisit the question of whether they should as the strategic situation changed around them. A project of the scope and scale of the Manhattan Project has stunning inertia. At extraordinary expense and great personal costs, under unimaginable pressure, the researchers had spent years of their lives building something wholly transformative and unprecedented.
Psychologically, they simply didn’t have it in them to quit their life’s work on the brink of completion just because the geopolitical justification they’d originally had was no longer valid, even if there were vague worries about igniting the atmosphere and more concrete worries about permanently changing the world for the worse.
