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The question of whether heisenberg deliberately nudged the german a-bomb effort up a blind alley is intriguing. The surveillance wiretaps from the english country house where the Hun boffins were all held at war's end indicate otherwise, that his calculations were simply wrong and that he would have given Hitler the bomb had he not simply screwed up the math.

But could the father of the uncertainty principle have committed such a dopey error? And would he have admitted as much to his incarcerated colleagues? Inquiring minds want to know -- and will probably go on wanting to know forever and a day.

otherwise, that his calculations were simply wrong and that he would have given Hitler the bomb had he not simply screwed up the math.

Possibly you're referring to the fission cross section of the U235 nucleus, which was subject to an unanticipated, and at first unnoticed, experimental error. This was published in the international scientific literature; the Germans read it and used it in their calculations of critical mass, arriving at a value much too large.

Some lab in the Allied countries replicated the experiment, found a different (and much more optimistic) value, and found the bug in the original procedure, thus lending credence to the new value. By this time, however, wartime security had clamped a lid on open publication of all research in this area; so the Allied scientists saw it and the Germans didn't.

It's an interesting question why the Germans themselves didn't replicate the cross-section experiment and find the correct value themselves. Maybe they didn't think it would be worth the nontrivial resources it would take. If they had come up with the right value, they might have oriented their program toward bombs rather than reactors. But then again, maybe not, because they could have calculated the cost to produce even the smaller, correct quantity of enriched U and found it infeasible.

In the end, with the reactors they built, they probably found the correct value for the cross section, but by then it would have been too late to do anything about it anyway.

(This note contains more speculation than I would really like, but I'm not up to slogging through my references today, especially because the most detailed one is in German, and I'm just too damn rusty +-<)B^).