what was the feared runaway nuclear reaction from Oppenheimer?

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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?

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Anonymous 0 Comments

While they were quite sure that it wasn’t a realistic probability (the movie very much played up the probability calculation of this happening) but there was a tiny tiny tiny chance that the nuclear explosion could cause a sufficiently large neutron burst (at sufficiently high pressure and temperature) to trigger an action where two nitrogen atoms (the most common element in earths atmosphere) and a hydrogen atom (hydrogen is everywhere) fuse together, release energy and create a runaway cascade that would set the entire planets atmosphere ablaze.

Both Oppenheimer and his top colleagues considered the chance vanishingly small, but it was (at the time) a non-zero probability. They couldn’t 100% say it wouldn’t happen, but it would require that this reaction was more likely than they had calculated (by several magnitudes) and that the nuclear bombs themselves proved multiple times more powerful than they had previously calculated. Based on how powerful the first bomb turned out to be they could immediately afterwards rule out the possibility of it ever happening (regardless of how powerful they made their bombs), the neutron capture rate just wasn’t high enough.

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