Everything about Heisenberg totally explained
Werner Karl Heisenberg (
December 5,
1901 –
February 1,
1976) was a celebrated
German physicist and
Nobel laureate, one of the founders of
quantum mechanics and acknowledged to be one of the most important physicists of the twentieth century. Heisenberg was the head of the
German nuclear energy project under the
Nazi regime, though the nature of this project, and his work in this capacity, has been heavily debated. He is most well-known for discovering one of the central principles of modern physics, the
Heisenberg uncertainty principle, and for the development of
quantum mechanics, for which he was awarded the
Nobel Prize in Physics in 1932.
In addition to the development of quantum mechanics, Heisenberg made many other notable contributions to physics. He discovered
isospin, co-discovered and heavily developed the
Kolmogorov theory of turbulent scaling, and introduced
S-matrix theory.
Family
He was the son of Dr. August Heisenberg, professor of the middle and modern Greek language at the
University of Munich, Germany and Annie Wecklein. In 1937, he married Elisabeth Schumacher with whom he'd seven children; Maria, University of New Hampshire physics professor
Jochen Heisenberg, Barbara, Wolfgang, Christine, Verena, and neurobiologist and geneticist
Martin Heisenberg.
Quantum mechanics
As a student, he met
Niels Bohr in
Göttingen in 1922. A fruitful and life long collaboration developed between the two.
He invented
matrix mechanics, the first formalization of quantum mechanics in 1925, which he developed with the help of
Max Born and
Pascual Jordan. His
uncertainty principle, developed in 1927, states that the simultaneous determination of two paired quantities, for example the position and momentum of a particle, has an unavoidable uncertainty. Together with Bohr, he formulated the
Copenhagen interpretation of quantum mechanics.
He received the
Nobel Prize in physics in 1932 for "
the creation of quantum mechanics, the application of which has, inter alia, led to the discovery of the allotropic forms of hydrogen".
In the late 1920s and early '30s, Heisenberg collaborated with
Wolfgang Pauli, and along with
Paul Dirac, developed an early version of
quantum electrodynamics. However, at the time, nobody could get rid of the infinities plaguing the theory, and it was only after World War II that a technique called
renormalization was invented to take care of the infinities.
After the discovery of the
neutron by
James Chadwick in 1932, Heisenberg proposed the proton-neutron model of the
atomic nucleus and used it to explain the
nuclear spin of
isotopes.
Controversy in prewar Germany
On 1 April 1935
Arnold Sommerfeld, Heisenberg’s teacher and doctoral advisor at the
University of Munich, achieved emeritus status. However, Sommerfeld stayed on as his own temporary replacement during the selection process for his successor, which took until 1 December 1939. The process was lengthy due to academic and political differences between the Munich Faculty’s selection and that of both the
Reichserziehungsministerium (REM, Reich Education Ministry.) and the supporters of
deutsche Physik, which was
anti-Semitic and had a bias against
theoretical physics, especially including
quantum mechanics. In 1935, the Munich Faculty drew up a candidate list to replace Sommerfeld as ordinarius professor of theoretical physics and head of the Institute for Theoretical Physics at the University of Munich. There were three names on the list: Werner Heisenberg, who received the
Nobel Prize in Physics in 1932,
Peter Debye, who would receive the
Nobel Prize in Chemistry in 1936, and
Richard Becker - all former students of Sommerfeld. The Munich Faculty was firmly behind these candidates, with Heisenberg as their first choice. However, supporters of
deutsche Physik and elements in the REM had their own list of candidates and the battle commenced, dragging on for over four years. During this time, Heisenberg, came under vicious attack by the supporters of
deutsche Physik. One such attack was published in
Das Schwarze Korps, the newspaper of the
Schutzstaffel, or SS, headed by
Heinrich Himmler. In the editorial, Heisenberg was called a “White Jew” who should be made to “disappear.” These verbal attacks were taken seriously, as there was physical violence against the Jews and they were incarcerated. Heisenberg fought back with an editorial and a letter to Himmler, in an attempt to get a resolution to this matter and regain his honor. At one point, Heisenberg’s mother visited Himmler’s mother to help bring a resolution to the affair. The two women knew each other as a result of Heisenberg’s maternal grandfather and Himmler’s father being rectors and members of a Bavarian hiking club. Eventually, Himmler settled the Heisenberg affair by sending two letters, one to SS-Gruppenführer
Reinhard Heydrich and one to Heisenberg, both on 21 July 1938. In the letter to Heydrich, Himmler said Germany couldn't afford to lose or silence Heisenberg as he'd be useful for teaching a generation of scientists. To Heisenberg, Himmler said the letter came on recommendation of his family and he cautioned Heisenberg to make a distinction between professional physics research results and the personal and political attitudes of the involved scientists. The letter to Heisenberg was signed under the closing “Mit freundlichem Gruss und, Heil Hitler!” (With friendly greetings, Heil Hitler!”) Overall, the Heisenberg affair was settled with a victory for academic standards and professionalism, however, with Wilhelm Müller taking over for Sommerfeld on 1 December 1939, this appointment was a political victory over academic standards. Müller wasn't a theoretical physicist, hadn't published in a physics journal, and wasn't a member of the
Deutsche Physikalische Gesellschaft; his appointment as a replacement for Sommerfeld was considered a travesty and detrimental to educating a new generation of theoretical physicists.
Work during the War
Nuclear fission was discovered in Germany in 1938. Heisenberg remained in
Germany during
World War II, ostensibly to help rebuild German science after the extensive
brain drain that occurred in the 1930s as a result of Nazi policies banning Jews from government jobs, which led to the expulsion of Jewish physics professors from the state universities. Heisenberg by all accounts was loyal to Germany, but not the Nazi regime . The
Kaiser Wilhelm Institute for Physics (of which he was the Director) was appropriated by the
Nazi Heereswaffenamt (Army Ordnance Board). He belonged to a team led by
Walther Bothe to develop one of Germany's many
nuclear weapon/
nuclear power programs, but the extent of his cooperation in the development of weapons has been a subject of much controversy. Heisenberg's work consisted of various efforts to create sustained fission reactions . A rival atomic bomb project was led by
Kurt Diebner for Heereswaffenamt, who, with
Paul Harteck worked on
uranium enrichment and a uranium-based atomic bomb. Neither team was successful before the end of the war, because of various factors including complications from various invasions toward the end of the war and lack of funding from the government. After the military reversals the Wehrmacht (German Army) suffered at the Russian Front during the winter of 1941-42, uranium research was downgraded in priority by the Reich's director of military research.
Ever since World War II, there has been speculation that Heisenberg had moral qualms and tried to slow down the project, and substantial evidence has been put forth that has conventionally been considered reflective of Heisenberg's ethical dilemma . One event that speaks to Heisenberg's difficulties with his situation is a June 1942 meeting Heisenberg had with
Albert Speer, the minister for Nazi munitions. During this discussion, Heisenberg didn't champion the project in a way that got it much attention or funding .
Allegations have been made, however, that Heisenberg himself may have attempted to paint this picture of innocence after the war. Thomas Powers' book
Heisenberg's War and
Michael Frayn's play
Copenhagen adopted this interpretation of the events. Although it's traditionally considered evidence in favor of Heisenberg's innocence, even the aforementioned meeting between Heisenberg and Speer have received other interpretations, including one from
Samuel Goudsmit of the
Alsos project stating that the reason Heisenberg didn't promote his project further is that he wasn't fully aware of the feasibility of an atomic bomb . At best, Heisenberg tried to hinder the German project; at worst, he was just unable to create an atomic weapon.
The debate about Heisenberg's views on the use of atomic weapons is centered on the period from 1939–1942, during which time Germany made a decision not to pursue a nuclear weapons programme. During this period, several events give insight into Heisenberg's role in that decision. At various points, evidence during the period suggested that Heisenberg was deliberately steering Germany's research efforts toward developing nuclear energy, rather than nuclear weapons. Some evidence suggests, that Heisenberg attempted to communicate these views to the Allies. For example, in April 1941 a German Jewish physicist,
Fritz Reiche, arrived in the United States bearing a message from Heisenberg's colleague and friend
Fritz Houtermans which was relayed to American officials in the following handwritten note:
» "a reliable colleague [Houtermans] who is working at a technical research laboratory asked him [Reiche] to let us know that a large number of German physicists are working intensively on the problem of the uranium bomb under the direction of Heisenberg, that Heisenberg himself tries to delay the work as much as possible, fearing the catastrophic results of a success." (Thomas Powers,
Heisenberg's War: The Secret History of the German Bomb.)
Next, there was Heisenberg's visit with an old friend
Niels Bohr in occupied
Copenhagen in September 1941. The purpose of this visit has been the subject of great debate . Further, German scientist Hans Peter Jensen visited Niels Bohr in Copenhagen during 1943, of which Bohr wrote that Jensen
» "talked [about] efforts to increase the production of
heavy water in Norway and hinted in this connection that the German physicists were only considering general technical energy generation."
Finally, in May 1943, the German spy Erwin Respondek passed a report to Sam Woods, an American consular official in Zurich, that
» "the Kaiser Wilhelm group [whereHeisenberg was chief of theoretical work in Berlin] purposely raised 'difficulties' to slow down work on the project." (Thomas Powers,
Heisenberg's War: The Secret History of the German Bomb.)
According to some Heisenberg critics, the German war efforts stalled in 1940 not because of moral qualms, but because Heisenberg had made a gross overestimate of the "critical mass" of fissionable material (Uranium 235) required for a bomb.
An estimate of this amount was crucial to the decision about proceeding with a serious nuclear weapons program because of the enormous difficulty and expense of separating the
U235 from the
U238 that makes up the vast bulk of natural
uranium and the length of time it would take to develop a reactor capable of transmuting the uranium into
plutonium.
According to some critics, Heisenberg had miscalculated the "critical mass" by not taking into account the "
drunkard's walk" trajectory of the slow
neutrons emitted, thereby overestimating the amount needed as being in the order of
tons, not
kilograms as was in fact the case.
However, the contention that Heisenberg had wrongly determined in 1940 that a uranium bomb wasn't technically feasible is at odds with other evidence. First, during the 1941 visit with Bohr, Heisenberg stated that
» "in the preceding years [Heisenberg] had devoted [him]self almost exclusively to the question and were quite certain that it could be done," and that he "felt certain that the war, if it lasted sufficiently long, would be decided with atomic weapons."
According to Bohr's later notes,
» "Heisenberg said explicitly that he didn't wish to enter into technical details but that Bohr should understand that he knew what he was talking about as he'd spent 2 years working exclusively on this question."
It is unclear why Heisenberg would report to Bohr in 1941 that his research efforts had led him to conclude that a usable nuclear weapon was feasible if, in fact, a miscalculation in 1940 had led him to conclude that it wasn't feasible.
Second, after the war, Heisenberg and other German physicists were taken by the British to
Farm Hall, where their conversations were monitored. The transcripts, however, are ambiguous and subject to debate. At points, it appeared that Heisenberg had miscalculated the
critical mass of uranium required for an atomic bomb—covert eavesdropping revealed that, on hearing of the Allied
bombing of Hiroshima, he was at first convinced it was a
propaganda trick, so sure was he that the critical mass was impracticably large. Some historians have questioned the reliability of the transcripts, as Heisenberg probably knew he was being monitored.
Indeed, there are indications that Heisenberg had made the correct calculation earlier. In June 1942, Heisenberg answered a question about the size of the fissionable core of a bomb by holding his hands to suggest something the size of a football or pineapple, which would have been roughly right. Indeed, after presenting the "incorrect" calculation to the Farm Hall scientists (including those sympathetic to the Nazi regime), one of Heisenberg's confidants,
Otto Hahn, questioned Heisenberg's remark that "tons" of U-235 were needed for a bomb, "But tell me why you used to tell me that one needed 50 kilograms of 235 in order to do anything. Now you say one needs two tons."
Later, Heisenberg told
Hahn,
» "Quite honestly I've never worked it out as I never believed one could get pure 235. I always knew it could be done with 235 with fast neutrons. That's why 235 only can be used as an explosive. One can never make an explosive with slow neutrons, not even with the heavy water machine [theGerman nuclear reactor], as then the neutrons only go with thermal speed, with the result that the reaction is so slow that the thing explodes sooner, before the reaction is complete."
Ultimately, upon seeing the reports of the bombing of Hiroshima, Heisenberg told his friend,
von Weizsäcker » "I was absolutely convinced of the possibility of our making an uranium engine [reactor] but I never thought that we'd make a bomb and at the bottom of my heart I was really glad that it was to be an engine and not a bomb. I must admit that."
Whatever the cause, it's clear that on
4 June,
1942, Heisenberg met with German Minister
Albert Speer concerning possible uses of Heisenberg's nuclear research, and particularly its potential suitability for the development of nuclear weapons. Notwithstanding Heisenberg's September 1941 report to
Bohr that he felt certain nuclear weapons could be constructed and powerful enough to conclude the war if it lasted long enough, during this meeting with Speer he highlighted the technical difficulties and vast time and materials required to separate the uranium needed for the project.
It was this meeting, and Speer's report on it to
Hitler, that effectively scuttled any military applications for his work, and limited Heisenberg's work during the remainder of the war to theoretical uses of nuclear energy. As Speer wrote,
» "Difficulties were compounded, Heisenberg explained, by the fact that Europe possessed only one
cyclotron, and that of minimal capacity. Moreover, it was located in
Paris and because of the need for secrecy couldn't be used to full advantage."
Curiously, albeit perhaps tellingly, Heisenberg didn't mention the cyclotron in
Copenhagen as a possible source for enriching uranium.
Heisenberg (1946) also proposed an enhancement of
Kolmogorov's model of turbulence, to explain the mechanism of transfer of energy from large to small eddies.
Postwar biography and controversy
In 1956, journalist
Robert Jungk published a book titled
Brighter Than a Thousand Suns, which painted Heisenberg as having single-handedly and purposely derailed the German project for moral reasons. To justify the claim, in the Danish edition of the book, Jungk printed an excerpt from a personal letter from Heisenberg. The excerpt, however, was taken heavily out of context, and in the
full letter
Heisenberg was far more demure about whether he'd taken a strong moral stance. After reading the excerpt, Bohr was understandably flustered that Heisenberg was (apparently) claiming to have purposely derailed the Nazi bomb project, as it didn't match his own perception of Heisenberg's war work at all.
Some historians of science have taken Bohr's draft letters as evidence against Heisenberg's contention that he'd met with Bohr to signal that Germany's scientists wouldn't pursue the development of nuclear weapons. Others have argued that Bohr profoundly misunderstood Heisenberg's intentions at the 1941 meeting, and that his reaction to Jungk's work was overly passionate. Significantly, Bohr's draft letters confirm virtually all of Heisenberg's recollection to Jungk of the substance of the meeting. However, as a piece of evidence the letters can't provide an answer to the question of why Heisenberg broached the topic of nuclear weapons—but not their technical aspects—with Bohr, or whether Bohr formed the correct "impression" of what Heisenberg wanted to say. Heisenberg's motives will most certainly continue to be debated, but it can't be questioned that he knew Bohr was going to be escaping to the allies when he spoke to him in 1941, and that Heisenberg was risking his life by speaking to anyone about atomic power or atomic weapons.
It is also thought that Italian scientist
Gian Carlo Wick approached Heisenberg in January 1944 as an emissary for the
OSS as part of
Operation Sunrise, to negotiate the capitulation of
Nazi scientists to the Allies'
Operation Alsos. Allied intelligence through
Stockholm continued to sound the alarm about
Nazi uranium research right up to war's end, but this was part of
Diebner's project, not Heisenberg's.
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