Carl Friedrich Freiherr von Weizsäcker (28 June 1912 – 28 April 2007) was a German physicist and philosopher. He was the longest-living member of the team which performed nuclear research in Nazi Germany during the Second World War, under Werner Heisenberg's leadership. There is ongoing debate as to whether or not he and the other members of the team actively and willingly pursued the development of a nuclear bomb for Germany during this time.
. . .After nuclear fission became known in early 1939 through the work of Otto Hahn and Lise Meitner, Weizsäcker (and by his own estimate, 200 other physicists) quickly recognised that nuclear weapons could potentially be built. He discussed the upsetting implications in February 1939 with philosopher friend Georg Max Friedrich Valentin Picht (1913–1982).
During the Second World War, Weizsäcker joined the German nuclear weapons program, participating in efforts to construct an atomic bomb, while based at the Kaiser Wilhelm Institute in Berlin. As early as August 1939, Albert Einstein warned U.S. President Franklin D. Roosevelt about this research and highlighted 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."
As a protégé of Werner Heisenberg, Weizsäcker 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. Early in the war — possibly until 1942 — he hoped a successful nuclear weapons project would earn him political influence. In July 1940 he was co-author of a report to the army on the possibility of "energy production" from refined uranium. The report also predicted the possibility of using plutonium for the same purpose including the production of a new type of explosives. During summer 1942 Weizsäcker filed a patent on a transportable "process to generate energy and neutrons by an explosion... e.g. a bomb". The patent application was found in the 1990s in Moscow.
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." Only by "divine grace", Weizsäcker said, were they spared the temptation to build the bomb as the German war economy was unable to mobilize the necessary resources.
Original sources about this question were 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. In the conversation after the group of detainees had listened to the BBC Radio news on dropping of the atomic bomb on 6 August 1945, Weizsäcker said: "I believe the reason we didn't do it was because all the physicists didn't want to do it, on principle. If we had wanted Germany to win the war we would have succeeded!"
But the "Farm Hall Transcripts" also 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. It was this version of events which was given to Jungk as the basis of his book. This story was untrue at least to the extent that the detainees also included scientists actively engaged in eager attempts to build a nuclear bomb, namely Kurt Diebner and Walther Gerlach. Max von Laue later called this agreement "die Lesart" (the Version). Although the memorandum which the scientists drew up was drafted by Heisenberg, von Laue wrote: "The leader in all these discussions was Weizsäcker. I did not hear any mention of any ethical point of view."
Weizsäcker himself stated that Heisenberg, Karl Wirtz and he had a private agreement to study nuclear fission to the fullest possible extent in order to "decide" themselves how to proceed with its technical application. "There was no conspiracy, not even in our small three-man-circle, with certainty not to make the bomb. Just as little, there was no passion to make the bomb..." In a recent report based on additional documents from Russian archives, historian Mark Walker concludes that "in comparison with Diebner [and] Gerlach ... Heisenberg and finally Weizsäcker did obviously not use all power they commanded to provide the National Socialists with nuclear weapons".
However, historian of science and technology Wolf Schäfer has concluded, that Weizsäcker did want to build the bomb for Hitler. In a detailed study about Weizsäcker’s contributions to both Nazi Germany and West Germany, he distinguished between the young and the older (pacifistic) Weizsäcker, that is, the person he was from 1939 to 1945, and the person he became thereafter.
The young von Weizsäcker was no clairvoyant; he expected a German victory and wanted to offer Hitler the superweapon to guarantee Germany's supremacy, not to prevent the dictator's suicide and the devastation of the country. What von Weizsäcker foresaw in 1941 was Germany's emergence as the world's first nuclear power. The highly talented Hitler would jump at this, he thought. The power of the atomic bomb would enable the dictator, who had already conquered Western Europe, to keep the "Anglo-Saxons" in check (USA), or rather bring them to their knees (Great Britain), and to colonize Russia. We can assume that the policy of peace, which the young von Weizsäcker wanted to discuss with Hitler, was the reorganization of Europe under German domination.
Ivan Supek (one of Heisenberg's students and friends) claimed that Weizsäcker was the main figure behind 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. According to Weizsäcker's own account, he had persuaded Heisenberg to meet Bohr in order to broker an accord of the international nuclear physicist "community" not to build the bomb. However, according to Bohr's (posthumously published) account of the events, Heisenberg enthusiastically promoted the prospect of German victory and wanted Bohr and his colleagues to assist in the German atomic program.
Later during the war Weizsäcker worked as a professor at the Reichsuniversität Straßburg. The American capture of his laboratory and papers there in December 1944 revealed to the Western Allies that the Germans had not come close to developing a nuclear weapon.
Weizsäcker was allowed to return to the part of Germany administered by the Western Allies in 1946, and became director of a department for theoretical physics in the Max Planck Institute for Physics in Göttingen. In 1952, he became the first director of the IFT (Institute of Theoretical Physics) in São Paulo which would later become part of UNESP. 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 degradation.
. . .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 that time, gave Weizsäcker an interest in questions of ethics and responsibility. In 1957, he was one of the Göttinger 18, a group of prominent German physicists who protested against the idea that the Bundeswehr (West German armed forces) should be equipped with tactical nuclear weapons. He further suggested that West Germany should declare its definitive abdication of all kinds of nuclear weapons.
Born into German nobility in 1912, Weizsäcker studied physics, astronomy, and math at various German institutions between 1929 and 1933, including the University of Göttingen and Leipzig University. He received his Ph.D. in physics from the latter in 1933 and became a physics professor at the university shortly thereafter. Later, he taught physics at the Kaiser-Wilhelm Institute of Physics and the University of Strasbourg from 1936-1942 and 1942-1944 respectively. During his time in academia, Weizsäcker worked alongside notable scientists such as Werner Heisenberg and Niels Bohr. His early research focused on planetary formation and the energy in stars.
Weizsäcker was involved in the German nuclear weapons program as early as August 1939. Albert Einstein wrote in his famous August 2, 1939 letter to President Franklin D. Roosevelt, “I understand that the son of the German Under-Secretary of State, von Weizsäcker, is attached to the Kaiser-Wilhelm Institute in Berlin where some of the American work on uranium is now being repeated.”
He was among the lead scientists of the Uranverein or “Uranium Club” working on the German atomic bomb project and attended the group’s first meeting in September 1939. Over the course of the war, he researched the means by which German scientists could produce fissionable uranium and plutonium isotopes and drafted two patents, found in Moscow in the 1990s, on methods to generate energy from neutrons.
Weizsäcker conducted his research at both Kaiser-Wilhelm Institute of Physics and the University of Strasbourg. In December 1944, after they captured his Strasbourg laboratory, American forces discovered the Germans had abandoned their atomic bomb program.
