Famously, Oppenheimer and co worked out how close a nuclear bomb test would be to causing a chain reaction of nitrogen fusion in the atmosphere. They made a lot of worst-case-scenario assumptions and still came to the conclusion that no, a nuclear bomb test wouldn’t scour the surface of the world....
I don't know what chain reaction exactly they were thinking of, but from modern fusion research, I believe we can confidently say that the atmosphere would need to be interior-of-a-large-star-level dense, and even then I'm not sure you'd get nitrogen fusing with anything without a lot of hydrogen or helium around. Nitrogen-nitrogen fusion seems extremely implausible for sure
How dense would the atmosphere need to be to result in a cataclysmic chain reaction during a nuclear explosion?
Famously, Oppenheimer and co worked out how close a nuclear bomb test would be to causing a chain reaction of nitrogen fusion in the atmosphere. They made a lot of worst-case-scenario assumptions and still came to the conclusion that no, a nuclear bomb test wouldn’t scour the surface of the world....