Can someone explain the feared runaway nuclear reaction that Oppenheimer presented Einstein in the film? The one where detonating a nuke would’ve exploded the whole world?
Wouldn’t that scenario require many orders of magnitude more energy than the output of the what the first (or current) nuclear weapons were capable of?
In: Physics
I’d like to add that the final line of the movie “I believe we did” when he was disscussing the posibility of a runaway reaction with Einstein is a reference to a belief that inevitably nukes will be used to destroy the world. Not from a chain reaction, but because ultimately nuclear war will occur.
If you want more of a back story, here is [a pop-sci article](https://www.discovermagazine.com/the-sciences/the-fear-of-setting-the-planet-on-fire-with-a-nuclear-weapon) about this.
Two things:
1. A real but theoretical and highly unlikely chance that the detonation of an atomic bomb could result in a runaway fusion reaction that would destroy the world. It wasn’t true (nitrogen can fuse of course and this happens in very large stars at the end of their life – but at immense temperatures and pressures that far exceed any conditions that could be produced by a mere atomic detonation), but they ran the numbers to make sure.
2. A clever narrative device to create a second climax in the movie.
The challenge of telling Oppenheimer’s story is he has the mid-career climax of all climaxes at Trinity. You really can’t top that. But the second half of his career is kind of a long denouement in which not much dramatic happens. There’s the dispute over nuclear secrets and the development of The Super (H Bomb) and ultimately the security clearance issues and ultimate rehabilitation of Oppenheimer before an early cancer death. But it’s all. . .a big of a let down after Trinity.
But the use of the concern about the atmosphere burning was a very clever way to use a minor concern the scientists had to create a second climax which revolves around Oppenheimer’s fictionalized conversation with Einstein at Princeton. And I can’t remember the line, but we see it once early without the dialog and then at the end of the movie we see the scene play out again with the dialog and Oppenheimer says something like, do you remember when we ask you about the possibility of starting a chain reaction that would destroy the world? What if we did? And we see cuts to missiles launching presumably with thermonuclear warheads on them. And it creates this wonderful second climax as a way to tie in Oppenheimer’s career, his interest in the paradoxes of quantum mechanics, and the heightened concerns over an increasingly dangerous world.
Short tl;dr
Atmosphere is full of nitrogen
If nitrogen get very very hot it can fuse which creates energy
If you explode bomb then nitrogen fusion will happen
Question is; Does the bomb lose more energy from just normal thermal radiation than it can possible get from nitrogen fusion?
Answer: Yes no matter what the temperature is, you always get more thermal loss than fusion gain, and thus a run-away reaction is not possible. But it took some math to actually prove that.
Imagine you’re playing with matches, and you’re worried that if you light one, it might set the whole house on fire. That’s kind of what the scientists were worried about with the first atomic bomb. They thought that if they set it off, it might be like lighting a match that could start a fire so big it would burn up the whole world.
They were afraid that the explosion might make the air or the ocean catch fire and keep burning, like when one domino knocks over another, and it just keeps going. But before they lit the ‘match’ (set off the bomb), the scientists did a lot of math and figured out that the bomb wasn’t powerful enough to start such a huge fire. It was more like a sparkler—it could burn really bright and hot, but it would burn out quickly and not catch everything else on fire.
So, even though they were nervous at first, they realized that it was safe to set off the bomb without worrying about burning up the whole planet
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