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Carl Friedrich von Weizsäcker and Friedrich Hund, 1993, Goettingen DPI . Image: Ian Howard

Carl Friedrich Freiherr von Weizsäcker (28 June 1912 - 28 April 2007 Starnberg) was a German physicist and philosopher. He was the last living member of the research team which tried and failed to develop a nuclear weapon for Nazi Germany.

Weizsäcker was born in Kiel, Germany, the son of the German diplomat Ernst von Weizsäcker. He was the elder brother of the former German President Richard von Weizsäcker, and father of the physicist and environmental researcher Ernst Ulrich von Weizsäcker.

From 1929 to 1933, Weizsäcker studied physics, mathematics and astronomy in Berlin, Göttingen and Leipzig, under the tutelage of such luminaries as Werner Heisenberg and Niels Bohr. The supervisor of his doctoral thesis was Friedrich Hund.

His special interest as a young researcher was the binding energy of atomic nuclei, and the nuclear processes in stars. Together with Hans Bethe he found a formula for the nuclear processing in stars, called the Bethe-Weizsäcker formula and the cyclic process of fusion in stars (Bethe-Weizsäcker process, published 1937).

Work on atomic weapons

During the Second World War, he joined the German nuclear energy project, participating in efforts to construct an atomic bomb. As a protegee of Heisenberg, he was present at a crucial meeting at the Army Ordinance headquarters in Berlin on 17 September 1939, at which the German atomic weapons program was launched.[1] In July 1940 he was co-author of a report to the Army on the possibility of "energy production" from refined uranium, and which also predicted the possibility of using plutonium for the same purpose.[2] He was later based at Strasbourg, and it was the American capture of his laboratory and papers there in December 1944 that revealed to the Western Allies that the Germans had not come close to developing a nuclear weapon.[3]

Historians have been divided as to whether Heisenberg and his team were sincerely trying to construct a nuclear weapon, or whether their failure reflected a desire not to succeed because they did not want the Nazi regime to have such a weapon. This latter view, largely based on postwar interviews with Heisenberg and Weizsäcker, was put forward by Robert Jungk in his 1957 book Brighter Than a Thousand Suns.

The truth about this question was not revealed until 1993, when transcripts of secretly recorded conversations among ten top German physicists, including Heisenberg and Weizsäcker, detained at Farm Hall, near Cambridge in late 1945, were published. The "Farm Hall Transcipts" revealed that Weizsäcker had taken the lead in arguing for an agreement among the scientists that they would claim that they had never wanted to develop a German nuclear weapon. This story, which they knew was untrue, was called among themselves "die Lesart" (the Version). Although the memorandum which the scientists drew up was drafted by Heisenberg, one of those present, Max von Laue, later wrote: "The leader in all these discussions was Weizsäcker. I did not hear any mention of any ethical point of view."[4] It was this version of events which was given to Jungk as the basis of his book.

William Sweet wrote recently in the Bulletin of the Atomic Scientists:

Although memories fade and Heisenberg and von Weizsäcker surely talked themselves into believing that what they said after the war... was really true, just about everything either one of them ever said on the subject - right down to von Weizsäcker's latest comments... - has been flatly untrue.[5]

Postwar career

Weizsäcker was allowed to return to Germany in 1946 and became head of the theoretical section of the Kaiser Wilhelm Institute (soon renamed the Max Planck Institute in Göttingen. From 1957 to 1969, Weizsäcker was professor of philosophy at the University of Hamburg. In 1957 he won the Max Planck medal. In 1970 he formulated a "Weltinnenpoltik" (world internal policy). From 1970 to 1980, he was head of the "Max Planck Institute for the Research of Living Condition in the Modern World, in Starnberg. He researched and published on the danger of nuclear war, what he saw as the conflict between the first world and the third world and the consequences of environmental destruction. In the 1970s he founded, together with the Indian philosopher Pandit Gopi Krishna, a research foundation "for western sciences and eastern wisdom". After his retirement in 1980 he became a Christian pacifist.

His experiences in the Nazi era, and with his own behavior in this time, gave Weizsäcker an interest in questions on ethics and responsibility. He was one of the Göttinger 18 - 18 prominent German physicists - who protested in 1957 against the idea that the Bundeswehr should be armed with tactical nuclear weapons. He further suggested that West Germany should declare its definitive abdication of all kinds of nuclear weapons. However he has never accepted his share of responsibility for the German scientific community's efforts to build a nuclear weapon for Nazi Germany, and continues to repeat the "version" of these events agreed on at Farm Hill, despite its exposure as a deliberate falsehood.[6]


In 1963 Weizsäcker was awarded the Friedenspreis des Deutschen Buchhandels (peace award of the German booksellers). In 1989, he won the Templeton Prize for Progress in Religion. He also received the Order Pour le Merite.


Zum Weltbild der Physik, Leipzig 1946 (ISBN 3-7776-1209-X)

- translation into English The World View of Physics, Londres 1952 - translation into French Le Monde vu par la Physique, Paris 1956

Die Geschichte der Natur, Göttingen 1948 (ISBN 3-7776-1398-3)

Die Einheit der Natur, Munich 1971 (ISBN 342333083X)

- translation The Unity of Nature, New York, 1980 (0-374-28100-9)

Wege in der Gefahr, Munich 1976

- translation The Politics of Peril, New-York 1978

Der Garten des Menschlichen, Munich 1977 (ISBN 3-446-12423-3)

- traduction The Ambivalence of progress, essays on historical anthropology, New York 1988 (ISBN 0-913729-92-2)

The Biological Basis of Religion and Genius, Gopi Krishna, New York, intro. by Carl Friedrich von Weizsäcker, which is half the book, 1971, 1972 (ISBN 0060647884)

Aufbau der Physik, Munich 1985 (ISBN 3446141421

- translation The Structure of Physics, Heidelberg 2006 (ISBN 1-4020-5234-0; ISBN 978-1-4020-5234-7)

Der Mensch in seiner Geschichte, Munich 1991 (ISBN 3-446-16361-1)

Zeit und Wissen, Munich 1992 (ISBN 3-446-16367-0)

Große Physiker, Munich 1999 (ISBN 3-446-18772-3)

Note regarding personal names: Freiherr is a title, translated as Baron, not a first or middle name. The female forms are Freifrau and Freiin.


Liquid drop model


  1. ^ John Cornwell, Hitler's Scientists (Viking 2003), 232
  2. ^ Cornwell, Hitler's Scientists, 235
  3. ^ Cornwell, Hitler's Scientists, 335
  4. ^ Cornwell, Hitler's Scientists, 398
  5. ^ William Sweet, "The Bohr Letters", Bulletin of the Atomic Scientists, May/June 2002, 20-27
  6. ^ Cornwell, Hitler's Scientists, 416


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