Japan did not have a plan for fighting the US if it bombed Japan with nuclear weapons, because Japan did not know that nuclear weapons existed, much less that the US actually had them.
Japan had a research program into nuclear weapons, but they ran into what they considered an insurmountable hurdle, which they believed would stop the US, too. Something to do with the lack of industrial capacity (electricity??) needed to produce enough fissionable material if memory serves.
If memory serves, both the Japanese and Germany nuclear weapons program made a subtle mistake with the cross-section of uranium atoms (or something like that), and wound up calculating that critical mass would be something like a ton of enriched uranium, and so not a useful weapon within WWII’s timeframe.
(I read about this while also reading Copenhagen, but I can’t remember what book. IIRC, Heisenberg claimed he had made this mistake deliberately and this was evidence that he wasn’t cooperating whole-heartedly with the Nazis, but the countercharge is that he seemed as astounded as the rest of the German physicists in custody when told of Hiroshima & Nagasaki.)
Is a duplicated error evidence for or against sabotage?
Heisenberg did not claim to have sabotaged it. Wikipedia claims that the story comes from selective quotation of the last letter here. But, when the bomb was announced, the imprisoned Heisenberg’s reaction of frantic work is suspicious to me: it suggests that he knew where the mistake was and wanted to go back and do the work he had blocked (but I don’t know the details; maybe he was working on something independent of the mistake).
Well, for 2 physicists of equal competency, differing results would suggest sabotage, since for both to give the wrong answer suggests that either they are not good enough to get the right answer at all, or they both got the answer and simultaneously decided to sabotage. Heisenberg was great, though, surely greater than anyone on the Japanese project; so I tend to regard the net as a wash, and focus more on Heisenberg’s reaction—which as I said suggests he genuinely made a mistake and was not engaged in passive resistance, and his surprise & flurry of activity was a give-away.
No numbers, unfortunately. But I did notice:
We did not know a process for obtaining of 235-Uranium with the resources available under wartime conditions in Germany, in quantities worth mentioning. Even the production of nuclear explosives from reactors obviously could only be achieved by running huge reactors for years on end.
Of course, for a few kilograms of enriched uranium or plutonium, you don’t really need huge reactors running for years and years—the hard part is enrichment. Yesterday I was reading a history of modern Korea, and North Korea obtained enough plutonium for a bomb or 3 by running a 20 or 50 megawatt reactor for 2 or 3 years, IIRC. But perhaps by Heisenberg’s 1940s standards such a reactor is beyond huge.
Japan had a research program into nuclear weapons, but they ran into what they considered an insurmountable hurdle, which they believed would stop the US, too. Something to do with the lack of industrial capacity (electricity??) needed to produce enough fissionable material if memory serves.
If memory serves, both the Japanese and Germany nuclear weapons program made a subtle mistake with the cross-section of uranium atoms (or something like that), and wound up calculating that critical mass would be something like a ton of enriched uranium, and so not a useful weapon within WWII’s timeframe.
(I read about this while also reading Copenhagen, but I can’t remember what book. IIRC, Heisenberg claimed he had made this mistake deliberately and this was evidence that he wasn’t cooperating whole-heartedly with the Nazis, but the countercharge is that he seemed as astounded as the rest of the German physicists in custody when told of Hiroshima & Nagasaki.)
Is a duplicated error evidence for or against sabotage?
Heisenberg did not claim to have sabotaged it. Wikipedia claims that the story comes from selective quotation of the last letter here. But, when the bomb was announced, the imprisoned Heisenberg’s reaction of frantic work is suspicious to me: it suggests that he knew where the mistake was and wanted to go back and do the work he had blocked (but I don’t know the details; maybe he was working on something independent of the mistake).
Well, for 2 physicists of equal competency, differing results would suggest sabotage, since for both to give the wrong answer suggests that either they are not good enough to get the right answer at all, or they both got the answer and simultaneously decided to sabotage. Heisenberg was great, though, surely greater than anyone on the Japanese project; so I tend to regard the net as a wash, and focus more on Heisenberg’s reaction—which as I said suggests he genuinely made a mistake and was not engaged in passive resistance, and his surprise & flurry of activity was a give-away.
No numbers, unfortunately. But I did notice:
Of course, for a few kilograms of enriched uranium or plutonium, you don’t really need huge reactors running for years and years—the hard part is enrichment. Yesterday I was reading a history of modern Korea, and North Korea obtained enough plutonium for a bomb or 3 by running a 20 or 50 megawatt reactor for 2 or 3 years, IIRC. But perhaps by Heisenberg’s 1940s standards such a reactor is beyond huge.