I just finished watching the last episode of the new Norwegian television series "The battle for heavy water", which focuses on the race to build the bomb during World War 2, and the role of Norway's heavy water production.
In the last episode there's a scene where the German scientist Heisenberg is discussing his calculations with his friend and assistant. They don't seem to know why they are wrong until Heisenberg seemingly thinks of something new, does some calculations on a blackboard and smiles to his friend. While they never speak about it, and the scene never outright shows if they are right, it is heavily implied that Heisenberg managed to get the theory and calculations behind the bomb figured out before the war ended. The next scene shows a wet sponge that they've used to erase the calculations.
So my question is, how accurate is the show in this regard? Did Heisenberg really manage to develop the theory behind the bomb before the war ended, but choose not to share the information with German command? Assuming Germany did get the knowledge in the last months of the war, would they even have been able to make a bomb in time?
This question comes up quite a bit. I'm going to forward you to something that /u/restricteddata wrote on his blog:
"Mark Walker’s two books (German National Socialism and the Quest for Nuclear Power, 1939-1949 and Nazi Science: Myth, Truth, And The German Atomic Bomb) are still excellent, though a bit more has come out since then. The basic gist of Walker’s work is that the German program knew a lot on paper, but never quite crystallized everything organizationally or technically to keep their program from being anything more than a side-project, focused primarily on reactor development. They never developed large-scale isotopic enrichment facilities, and they never got a reactor that went critical.
"Their reactor work was sophisticated given the conditions under which it was being done, but it never achieved criticality. Some members of the various teams that worked on the project had some fairly accurate understandings of how a nuclear weapon might be made, but there was also a lot of confusion circulating around (some members of the team understood it would be a fast-neutron fission reaction in enriched material, some were confused and focused on it being basically an out-of-control pile). Some were considering rather advanced designs (Karlsch has convinced me that they thought a bit about implosion, for example), but the whole thing was mostly a exploratory program."
On that show: I saw the previews for it and thought that the major problem was exaggerating German interest and capabilities with regards to nuclear weapons. The focus of the show obviously is the Norsk Hydro sabotage operation, which the Allies did think was important, would be the thing that stopped Germany, etc. But we have long since known that the German program was still-born, and that even if Norsk Hydro had not been sabotaged, there is no way they would have gotten a bomb. I consider this to be one of the unfortunate aspects of how we popularly talk about atomic bombs and World War II — fear of a Nazi bomb did motivate the Allies in the early stages of the project, but it turned out to be an unfounded fear. Often this last part gets left off, even though, in my eyes, it is key to understanding the import of the bomb programs.
As for "developing the theory" — it is hard to say what Heisenberg did and did not know about bomb theory. He was mostly working on reactors, which use a somewhat different type of chain reaction (moderated, slow neutrons). At Farm Hall, at the immediate end of the war, Heisenberg exhibited evidence of sloppy thinking about bombs, thinking they would work like out-of-control reactors. This would not work as a weapon. However earlier in the war Heisenberg did give talks which indicated that he understood the difference between a reactor chain reaction and a bomb chain reaction (the latter relying exclusively on fast, unmoderated neutrons).
But the real silly thing about this is that it is not about having some "theory." It is about industrial effort. The Germans had an adequate "theory" in 1941 — Germany Army Ordnance scientists concluded that it would take between 10 and 100 kilograms of enriched uranium to make a bomb (this is correct — the bare critical mass of U-235 is 52 kg, and the Little Boy bomb used 64 kg, and more sophisticated implosion bombs can get away with 25 kg or less), but that it would be an incredible investment, which major risks associated with it, and lots of uncertainties. They decided, at that point, that it wasn't worth it, and that nobody else was likely to do it. And they were correct — it wasn't likely that the US or UK were going to do it, because it was indeed an incredible expense and risk, but they did it anyway. To give you some idea of how expensive it is in terms of resources, the Manhattan Project employed about 1% of the entire US civilian labor force over the course of its existence — just for one project. To give you an idea of the risk of failure, if the bombs had been delayed by just a couple of months (an easy thing to imagine, especially when one knows the technical surprises the US hit along the way) they probably would not have been ready for use during World War II.
The Germans were nowhere close to making a bomb, theory or no theory.
While you wait for answers, you might be interested in some previous threads on the German nuclear program: