
The Private Heisenberg and the Absent Bomb - al_olpimo
http://www.nybooks.com/articles/2016/12/22/private-heisenberg-absent-bomb/
======
Animats
That's been a speculation for decades. Here's a more technical analysis of
Heisenberg's calculation of critical mass.[1] He had a figure of tons of
uranium. In reality, the bare-sphere critical mass of U-235 is 52Kg. The
Hiroshima bomb, which was a very simple design, used 62Kg. With reflectors and
compression, smaller amounts can be used.

Whether Heisenberg miscalculated this by intent or mistake remains unknown.

[1] [https://www.mpiwg-
berlin.mpg.de/sites/default/files/p467_3.p...](https://www.mpiwg-
berlin.mpg.de/sites/default/files/p467_3.pdf)

~~~
M_Grey
It's an interesting and somewhat romantic idea, but frankly I doubt that
someone as intelligent as Heisenberg wouldn't have understand that whatever
his calculation claimed, this wasn't going to stop with him.

~~~
Nomentatus
But as the last part of the article explains, Heisenberg could probably count
on his peers not looking too closely at whatever calculation he made, so long
as it discouraged the project. And his peers, in this matter, at that time,
were not many.

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amai
Popp 2016: "Misinterpreted Documents and Ignored Physical Facts: The History
of ‘Hitler's Atomic Bomb’ needs to be corrected" is obviously unknown to the
author of this article:

[http://onlinelibrary.wiley.com/doi/10.1002/bewi.201601794/ab...](http://onlinelibrary.wiley.com/doi/10.1002/bewi.201601794/abstract)

"It is shown that until the end of the war the German physicists did not know
that an atomic bomb can only be made with fast neutrons, except Heisenberg,
who, however, discovered it rather late, did not communicate it clearly and
did not study any bomb physics. The physically correct interpretation of the
documents reveals that the German physicists worked unsuccessfully on a
reactor, which would have been a prerequisite for a plutonium bomb. But they
did not know how to build a bomb because they never worked on a realistic bomb
theory."

~~~
mannykannot
I don't know whether Thomas Powers is acquainted with this particular paper,
but the paper itself makes it clear that Mr. Powers is well acquainted with
many of the documents that form the basis of the paper. Popp's paper and
Powers' article are about two different, albeit related, issues: Popp's
purpose is to show that the German scientists' grasp of bomb-making has often
been exaggerated (though not particularly so by Powers, who has been
criticized by Walker for the opposite), while Powers' article considers
whether Heisenberg's recently-published letters to his wife shed any more
light on his purpose and motives. While knowing what he knew (and thought he
knew) of bomb-making helps in analyzing his words and actions, physics alone
cannot resolve the matter.

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ghaff
It's fairly fictionalized but the play Copenhagen uses a visit between
Heisenberg and Bohr to explore this topic. There's a decent BBC version.

~~~
mannykannot
My impression (recalled over a decade or more) is that the play uses the
meeting to launch into an exploration of the moral ambiguity and - yes -
uncertainty surrounding Heisenberg's wartime role. The fictional dialog is
much longer than the actual meeting apparently was, and it refers to events
that were subsequent to that meeting. IIRC, it followed the publication of
Thomas Powers' book on the topic but preceded the publication of the Farm Hall
transcripts. I thoroughly recommend it.

~~~
ghaff
There's also a play (Operation Epsilon) based on the Farm Hall transcripts.
It's perhaps a bit too literal and has a lot of characters. That said, while I
don't think it's in the same class as a work of theater as Copenhagen, I
definitely recommend it if it comes around.

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Genro
A lot has been said about Heisenberg’s calculation of the critical mass of U
235. Many believe it to be his miscalculation. I think most people would agree
that he was quite a ’good’ mathematician and yet the analysis in the Farm Hall
transcript is at a level one would expect from a first year undergraduate. No
mention of ’Laplace transform into spherical coordinates’, or more simply
’Fick Law’ on diffusion. When he talks about 10 tons of U235, Hahn (a chemist)
reminds him that he has told him that only 50 Kg is needed. And later when
Hahn askes how the bomb works Heisenberg talks of ’each neutron begets two
children’ and that 1 ton is needed. A week later Heisenberg gives a very
‘polished’ lecture on the subject using the appropriate mathematical concepts.
The question is did he work this all out in a few days or did he already know?
Perhaps he had some ambivalence about putting such a weapon in the hands of
someone slightly ‘unhinged’, a dilemma we have today!

~~~
Genro
As a foot note. Heisenberg was not the only one to foster the idea that the
weight of such a bomb would be an impediment to its realisation. Both
Heisenberg and Yoshio Nishina were students under Niels Bohr. Nishina went on
to become Japan’s eminent physicist and to work on Japan’s own atomic bomb but
even he had some ambivalence about such a weapon. As recorded in the minutes
of the meeting on the 2nd July 1943 at Riken, Tokyo, after describing some
technical aspects to Lt. Gen. Nobu-uji, Nishina adds “ that is to say, the
weight of this thing would be enormous and because of this, the opinion is
that it would not be suitable (as a bomb)”.
すなわちボンブの重量甚大なるものとなるを以て、適当ならざるべしとの見解なり Sunawachi bombu no jyuryo jindai naru
mono to naru wo motte tekito narazarubeshi tono kenkai nari.”

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andyv
"Heisenberg's War" is about the possibility that Heisenberg either didn't try
very hard or perhaps deliberately sabotaged the German bomb effort. Very
controversial, great read.

[https://www.amazon.com/Heisenbergs-War-Secret-History-
German...](https://www.amazon.com/Heisenbergs-War-Secret-History-
German/dp/0306810115/ref=sr_1_1?ie=UTF8&qid=1487032563&sr=8-1&keywords=heisenberg%27s+war)

~~~
peterbecich
Heisenberg is a smaller part of this book; gripping read:
[https://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb](https://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb)

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ChuckMcM
I think it would be horrible to be in a country with a leader like Hitler
knowing a way to deliver them extraordinary power to do damage and
destruction.

