LA-602: Ignition of the Atmosphere with Nuclear Bombs, a research report from the Manhattan Project, is to the best of my knowledge the first technical analysis ever conducted of an uncertain danger of a human-caused extinction catastrophe.

Previously, Teller and Konopinski had been assigned the task of disproving a crazy suggestion by Enrico Fermi that a fission chain reaction could ignite a thermonuclear reaction in deuterium - what we now know as an H-Bomb. Teller and Konopinski found that, contrary to their initial skepticism, the hydrogen bomb appeared possible.

Good for their rationality! Even though they started with the wrong conclusion on their bottom line, they were successfully forced away from it by arguments that could only support one answer.

Still, in retrospect, I think that the advice the future would give to the past, would be: Start by sitting down and saying, "We don't know if a hydrogen bomb is possible". Then list out the evidence and arguments; then at the end weigh it.

So the hydrogen bomb was possible. Teller then suggested that a hydrogen bomb might ignite a self-sustaining thermonuclear reaction in the nitrogen of Earth's atmosphere. This also appeared extremely unlikely at a first glance, but Teller and Konopinski and Marvin investigated, and wrote LA-602...

As I understand LA-602, the authors went through the math and concluded that there were several strong reasons to believe that nitrogen fusion could not be self-sustaining in the atmosphere: it would take huge energies to start the reaction at all; the reaction would lose radiation from its surface too fast to sustain the fusion temperature; and even if the fusion reaction did grow, the Compton effect would increase radiation losses with volume(?).

And we're still here; so the math, whatever it actually says, seems to have been right.

Note that the Manhattan scientists didn't always get their math right. The Castle Bravo nuclear test on March 1, 1954 produced 15 megatons instead of the expected 4-8 megatons due to an unconsidered additional nuclear reaction that took place in lithium-7. The resulting fallout contaminated fishing boats outside the declared danger zone; at least one person seems to have died.

But the LA-602 calculations were done with very conservative assumptions, and came out with plenty of safety margin. AFAICT (I am not a physi...

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