[ RadSafe ] Death of Carl Friedrich von Weizsäcker -- worked on Nazi atomic bomb project

John Jacobus crispy_bird at yahoo.com
Fri May 4 07:04:22 CDT 2007

>From PhysicWEB at

Carl Friedrich von Weizsäcker: 1912--2007
1 May 2007

The physicist and philosopher Carl Friedrich von
Weizsäcker, who was the last surviving member of the
team that tried and failed to build a nuclear bomb for
Germany during the Second World War, died on 28 April
at the age of 94. After the war, von Weizsäcker
controversially claimed that he and other German
physicists had deliberately chosen not to build the
bomb because they did not want to equip the Nazi
regime with such a dangerous weapon. Von Weizsäcker
also accompanied Werner Heisenberg to visit Niels Bohr
in Nazi-occupied Denmark in September 1941 -- a famous
meeting that was later to inspire Michael Frayn's
stage play Copenhagen.

Carl Friedrich von Weizsäcker 

Carl Friedrich von Weizsäcker was born on 28 June 1912
in the northern German port city of Kiel. Between 1929
and 1933 he studied physics, astronomy and maths in
Berlin, Göttingen and Leipzig, where he worked with
some of the leading physicists of his day, including
Heisenberg, Bohr and Erwin Schrödinger. As a young
physicist, von Weizsäcker became interested in the
binding energy of atomic nuclei and in 1937 determined
what later became known as the "Bethe--Weizsäcker
formula", which predicts the energy of the nucleus in
terms of the number of constituent protons and

In 1939 von Weizsäcker became part of Germany's
"uranium project" -- a loose network of scientists
across the country who began carrying out research
into nuclear reactors, isotope separation and nuclear
explosives. Although these scientists never succeeded
in building a practical nuclear weapon, historians
have long wondered why this was the case. Some have
argued that physicists like Heisenberg and von
Weizsäcker simply lacked the technical knowledge to
build a bomb. Others claim that these physicists did
not bother determining key quantities like the
critical mass of the bomb because they knew the German
government did not have the resources to ever build
such a device, which made it pointless to carry out
such a calculation. 

After the war, von Weizsäcker claimed that the real
reason why he and other German scientists had not
built a bomb was that they had deliberately chosen not
to, fearing its appalling consequences in the hands of
the Nazi regime. Von Weizsäcker first put forward this
version of events in interviews he gave with the
historian Robert Jungk, whose 1957 book Brighter than
a Thousand Suns suggested that von Weizsäcker and
Heisenberg had acted honourably all along. 

The full story only emerged years later when
transcripts of conversations between von Weizsäcker,
Heisenberg and eight other German physicists, who had
been secretly recorded while they were interned by the
British military at Farm Hall, near Cambridge, were
finally published in 1993. It turned out that von
Weizsäcker had deliberately encouraged his fellow
physicists to argue that they had never wanted to
build a bomb, even though they knew this was not
strictly true. 
After the war, von Weizsäcker returned to research,
being appointed director of the department of
theoretical physics at the Max Planck Institute in
Göttingen before taking up a professorship at the
University of Hamburg in 1957. That he year he was one
of 18 prominent scientists to sign the "Göttingen
declaration", which called for West Germany to not
develop nuclear weapons. 

A committed Christian, von Weizsäcker also turned his
attention to philosophy, developing a keen interest in
ethics and responsibility. His books include The World
View of Physics, The Unity of Nature and The Politics
of Peril. Von Weizsäcker's younger brother, Richard
von Weizsäcker, was German president between 1984 and

Von Weizsäcker briefly returned to the spotlight in
2002 when he commented on the release of letters that
Bohr had written -- but never sent -- concerning the
visit of Heisenberg and Von Weizsäcker to Copenhagen
in September 1941. These letters suggest that
Heisenberg and colleagues had indeed been working
flat-out on a bomb between 1939 and 1941.

About the author
Matin Durrani is editor of Physics World

What are the facts? Again and again and again – what are the facts? Shun wishful thinking,. . . avoid opinion, [and] care not what the neighbors think, . . .what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!” 
 "Time Enough for Love," Robert Heinlein, 1973

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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