Longest Nuclear weapons can be delayed

What is the longest nuclear weapons can be delayed, with any POD after 1900 and not causing butterflies so that everything up until mid1945 proceeds more or less as OTL.
 
If you just got rid of the World Wars, I guess that would get rid of an instant need for nuclear weapons by a couple decades. Or cause some massive geological disaster or plague that kills off a large number of people, that could also be an effective way.
 
The only POD I can think of which fits is the Frisch-Peierls memorandum - before that point everyone knew an atomic bomb was possible but were thinking in terms of something weighing many tonnes which would have to be delivered to the target by ship, and so wasn't a practical weapon. With the F-P memorandum that changed, and it was realised that it was a practical air-dropped weapon. That's where the funding for all the research comes from - kill (well, delay - once nuclear power becomes widespread, and it isn't stopped by losing the F-P memorandum, then the science will be far better understood) and the fact that it is a practical weapon will rapidly become obvious to anybody. At best that probably gets you a decade.
 
Arthur Jeffrey Dempster is killed by Spanish flu, so he doesn't discover U-235, which possibly delays the discovery until say 1938-39, or even 1940, which means there's no chance of getting a bomb until after the war at the very least.
 
If you just got rid of the World Wars, I guess that would get rid of an instant need for nuclear weapons by a couple decades. Or cause some massive geological disaster or plague that kills off a large number of people, that could also be an effective way.

Um, I said it happens in a way that wouldn't change history from OTL more or less until mid1945, before the US contemplated nuking Japan. So the POD can be well before 1945, but won't cause any butterflies that causes TTL to deviate from OTL until around the time the US was about to nuke Japan.

Arthur Jeffrey Dempster is killed by Spanish flu, so he doesn't discover U-235, which possibly delays the discovery until say 1938-39, or even 1940, which means there's no chance of getting a bomb until after the war at the very least.

Is there a way to prevent it from being discovered to the present day given the constraints in the OP, or is it ASB?
 
The Theory or Relativity was such a stroke of genius, I'd say the best bet for a long delay would be removing Einstein. The Michelson-Morley experiment had indicated the speed of light was constant in all reference frames back in 1887, but it seems no-one except Einstein was ready to take the conceptual leap that this was a real, invariable fact of how the universe worked, with many still clinging to the aether model.

Without Einstein, the formulation of a theory of relativity could easily be pushed back a couple of decades, meaning no-one would even consider nuclear energy a possibility before the late 1930s, or even into the '40s. That of course has massive repercussions on the end of WWII in the Pacific, as well as the development of the early Cold War, and probably means any development programme gets less resources focused on it than OTL's Manhattan Project (it would be hard to get more resources focused on it...). In this scenario, I could easily see the first atom bomb appearing as late as the 1980s.
 
@nixonshead: The General Theory of Relativity, perhaps, but the Special theory probably would have been found within 5 years. Other people had developed a version of it (admittedly, not as complete as Einstein's), so there's no reason to assume others couldn't.
 
@nixonshead: The General Theory of Relativity, perhaps, but the Special theory probably would have been found within 5 years. Other people had developed a version of it (admittedly, not as complete as Einstein's), so there's no reason to assume others couldn't.
The other issue is that you don't need relativity to realise that nuclear fission gives off a hell of a lot of energy - that was measured experimentally, and even without the theory to explain it they'd have figured out what was going on over much the same timescale. Once you've measured it, the theory will follow quickly.
 
@nixonshead: The General Theory of Relativity, perhaps, but the Special theory probably would have been found within 5 years. Other people had developed a version of it (admittedly, not as complete as Einstein's), so there's no reason to assume others couldn't.
Didn't Einstein himself say that Poincare was getting there, and that he might have discovered Relativity if Einstein couldn't?
 
Is there a way to prevent it from being discovered to the present day given the constraints in the OP, or is it ASB?
Not really, someone's going to stumble across it sooner or later. The only reason I didn't go all-out and suggest killing both him and Francis William Aston in 1918/19 is because I didn't know how important mass spectrometry was in other fields.
 
Didn't Einstein himself say that Poincare was getting there, and that he might have discovered Relativity if Einstein couldn't?

Poincare may have already discovered special relativity before Einstein did. Heck, James Clerk Maxwell could have done it if he'd tried - it follows on from his equations, coupled with the Michelson–Morley experiment that demonstrated that the speed of light is constant regardless of the observer's own motion.

The thing about the Great Man theory is that there are always plenty more great (wo)men around to fill any gap. Hail Hydra. :)D)
 
Oh sometimes with the right Great Man you can do it. Without the two I named you could potentially set back mass spectrometry as a whole by half a decade, and possibly the discovery of U-235 by a decade (or more perhaps, given the war).
 
I'd say that removing the First and then the Second World War would be enough, which doesn't take that much. Just delay things long enough for the social democrats to become influential enough in Germany that the focus moves to internal reform rather than external relations, and then let things wind on.

Nuclear weapons were both very expensive and rather unproven, so I think you could easily see them simply not being developed.
 
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