what was the feared runaway nuclear reaction from Oppenheimer?

Question

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

Answer 1

>Can someone explain the feared runaway nuclear reaction that Oppenheimer presented Einstein in the film?

A group of Manhattan Project scientists were talking and one jokingly brought up the idea that the fission reaction from setting off the nuke would trigger a chain reaction that would temporarily turn the Earth’s entire atmosphere into a glorified star. The whole nuke worked on the idea that by inciting an atom to break, these two new atoms would then bump into 2 other atoms and repeat trillions of times to create a level of heat and pressure somewhat comparable to taking a chunk out of the sun. What this whole dilemma, introduced, though, was a new aspect that wasn’t previously taken into account; could that chain reaction then carry into the atmosphere until that same level of heat and pressure was being applied by every gas particle on the planet?

>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?

Yes, it would take magnitudes more power than what we have even today, and we’re well aware of that now. But now isn’t then. You have to keep in mind our knowledge of radiation at this time was still juvenile, and as far as we knew then this would be the first time a fission reaction would have even happened on Earth. Every aspect of what they were doing was surrounded by the shroud of the unknown.

That said, though, I’m not sure how the movie portrays it but it really wasn’t that big of a dilemma during the real project. After it being proposed the same scientists almost immediately began running the numbers of it, since they weren’t going to test something that could destroy the whole planet in an instant, and it didn’t take long for them to realize the scenario was so improbable it could be practically labelled as impossible.