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Carl Friedrich von Weizsäcker

Carl Friedrich von Weizsäcker, 1993
Born June 28, 1912
Kiel, Schleswig-Holstein
Died April 28, 2007 (aged 94)
Starnberg, Bavaria
Citizenship Germany
Nationality German
Ethnicity German
Fields Physics
Doctoral advisor Friedrich Hund
Notable awards Templeton Prize

Carl Friedrich Freiherr von Weizsäcker (June 28, 1912 – 28 April 2007) was a German physicist and philosopher. He was the longest-living member of the research team which performed nuclear research in Germany during the Second World War, under Werner Heisenberg's leadership. There is ongoing debate as to whether he, and the other members of the team, actually willingly pursued the development of a nuclear bomb for Germany during this time.

Weizsäcker was the son of the diplomat Ernst von Weizsäcker, the elder brother of the former German President Richard von Weizsäcker, father of the physicist and environmental researcher Ernst Ulrich von Weizsäcker and father-in-law of the former General Secretary of the World Council of Churches Konrad Raiser.

Born in Kiel, Schleswig-Holstein, Weizsäcker was raised in Stuttgart, Basel, and Copenhagen. From 1929 to 1933, Weizsäcker studied physics, mathematics and astronomy in Berlin, Göttingen and Leipzig supervised by and in cooperation, e.g., with 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).



He is the grandson of Karl Hugo von Weizsäcker, the Prime Minister of the Kingdom of Württemberg. His grandfather was ennobled in 1897, and raised to the hereditary nobility with the title of Baron (Freiherr) in 1916. As such Carl Friedrich Weizsäcker became Baron Carl Friedrich von Weizsäcker at the age of four. After 1919, noble titles have legally been considered parts of the family name.

Work on atomic weapons

During the Second World War, Weizsäcker joined the German nuclear energy project, participating in efforts to construct an atomic bomb. As a protégé of Heisenberg, he was present at a crucial meeting at the Army Ordnance 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]

As early as August 1939, Albert Einstein had warned U.S. President Franklin D. Roosevelt about this research and that: "... the son of the German Under-Secretary of State, von Weizsäcker, is attached to the Kaiser-Wilhelm-Institut in Berlin where some of the American work on uranium is now being repeated."[4]

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. In a 1957 interview with the German weekly Der Spiegel, Weizsäcker frankly admitted to the scientific ambitions of those years "We wanted to know if chain reactions were possible. No matter what we would end up doing with our knowledge - we wanted to know."[5]

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 under Operation Epsilon at Farm Hall, near Cambridge in late 1945, were published. The "Farm Hall Transcripts" 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."[6] It was this version of events which was given to Jungk as the basis of his book.

Weizsäcker stated himself that Heisenberg, Wirtz and he had a private agreement to study nuclear fission to the fullest possible in order to "decide" themselves how to proceed with its technical application. "There was no conspiracy, not even in our small three-men-circle, with certainty not to make the bomb. Just as little, there was no passion to make the bomb...." [7]

Ivan Supek (one of Heisenberg's students and friends) claimed[8] that Weizsäcker was the main figure of the famous and controversial Heisenberg - Bohr meeting in Copenhagen in September 1941. Allegedly, he tried to persuade Bohr to mediate for peace between Germany and Great Britain.

Postwar career

Carl Friedrich von Weizsäcker.

Weizsäcker was allowed to return to Germany in 1946 and became director of a department for theoretical physics in the Max Planck Institute for Physics in Göttingen (successor of Kaiser Wilhelm Institute). 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 "Weltinnenpolitik" (world internal policy). From 1970 to 1980, he was head of the "Max Planck Institute for the Research of Living Conditions 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, and intensified his work on the conceptual definition of quantum physics, particularly on the Copenhagen Interpretation.

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.

Weizsäcker died in Söcking near Starnberg. On the question on whether he accepted his share of responsibility for the German scientific community's efforts to build a nuclear weapon for Nazi Germany, opinions are split.

Theory of Ur-Alternatives

Carl Friedrich von Weizsäcker pioneered the theory of ur-alternatives in his books "Einheit der Natur" (1971) (The Unity of Nature, New York, 1980 (0-374-28100-9) and deeply developed it in his book Aufbau der Physik, Munich 1985 (ISBN 3446141421, English : The Structure of Physics, Heidelberg 2006 (ISBN 1-4020-5234-0; ISBN 978-1-4020-5234-7) and again in his main work "Zeit und Wissen" (1992). The theory axiomatically constructs quantum physics from distinguishing between empirically observable, binary alternatives. Weizsäcker uses it to derive the 3-dimensionality of space and to estimate the entropy of a proton falling into a black hole. The theory represents an important contribution to digital physics.

Awards and honours

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 Mérite.

There is a Gymnasium named after him, in the town of Barmstedt, which lies northwest of Hamburg, in Schleswig-Holstein, the Carl Friedrich von Weizsäcker Gymnasium in Barmstedt.


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


  • Zum Weltbild der Physik, Leipzig 1946 (ISBN 3-7776-1209-X), 2002, 14th edition, renewed and with introduction by Holger Lyre[1]
    • translation into English The World View of Physics, London, 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 (ISBN 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)
    • translation 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)

See also


  1. ^ John Cornwell, Hitler's Scientists (Viking 2003), 232
  2. ^ Cornwell, Hitler's Scientists, 235
  3. ^ Cornwell, Hitler's Scientists, 335
  4. ^ Einstein's letter to Roosevelt, 2 August 1939
  5. ^ DER SPIEGEL, "...und führe uns nicht in Versuchung: Vom gespaltenen Atom zum gespaltenen Gewissen - Die Geschichte einer menschheitsgefährdenden Waffe", vol. 11(19) (Mai 8, 1957), p. 52
  6. ^ Cornwell, Hitler's Scientists, 398
  7. ^ CFvW August 5, 1990, Letter to Mark Walker in: CFvW, Lieber Freund, lieber Gegner. München (Hanser) 2002, pp 277-283
  8. ^ Jutarnji list. "A March 2006 interview with Ivan Supek relating to 1941 Bohr - Heisenberg meeting (Croatian)". Jutarnji list.,3,19,supek_intervju,17440.jl?artpg=1. Retrieved 2007-08-13.  

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