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. He was born in Würzburg,
Germany and died in Munich. Heisenberg was the head of the
German nuclear energy project, 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.
Family
He was the son of Dr. August Heisenberg, professor of Byzantine studies at the University of Würzburg, Germany and Annie Heisenberg (née Wecklein). In 1937, he married
Elisabeth Schumacher with whom he had seven children, including 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 20s 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.
During the early days of the Nazi regime in Germany, Heisenberg was harassed as a "White Jew"
for teaching theories that Albert Einstein, a prominent Jew, had conceived. Teaching these theories was in contradiction to the Nazi-sanctioned Deutsche Physik movement. After a character investigation that Heisenberg himself instigated and
passed, SS chief Heinrich Himmler banned any
further political attacks on the physicist.
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.
There has been speculation that Heisenberg had moral qualms and tried to slow down the project. Heisenberg himself may have
attempted to paint this picture after the war, and Thomas Powers' book Heisenberg's War and Michael Frayn's play Copenhagen adopted this
interpretation. This is because during a June 1942 meeting with Albert Speer, the minister
for Nazi munitions, Heisenberg did not champion the project in a way which got it much attention or funding (which
Samuel Goudsmit of the Alsos project
interpreted as being partially because Heisenberg himself was not fully aware of the feasibility of an atomic bomb). At best, he
tried to hinder the German project; at worst, he was just unable to create an atomic bomb.
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 which 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."[1]
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 [where Heisenberg was chief of theoretical work in Berlin] purposely raised 'difficulties' to slow
down work on the project." (Powers, id.)
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 was not 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."[2]
According to Bohr's later notes,
- "Heisenberg said explicitly that he did not wish to enter into technical details but that Bohr should understand that he knew
what he was talking about as he had 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 was not 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."[3]
Later, Heisenberg told Hahn,
- "Quite honestly I have 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 [the German 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 would
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 is 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 could not be used to full advantage."
Curiously, albeit perhaps tellingly, Heisenberg did not mention the cyclotron in Copenhagen as a possible source for enriching uranium.
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 had 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 did not 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 had met with
Bohr to signal that Germany's scientists would not 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 cannot 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 cannot 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.
References
- David C. Cassidy, "Uncertainty: The Life and Science of Werner Heisenberg", (W. H. Freeman) ISBN 0-7167-2503-7
- James Glanz, "New Twist on Physicist's Role in Nazi Bomb". The New York Times, February 7, 2002.
- Mark Walker, German National Socialism and the Quest for Nuclear Power, 1939-1949 (London: Cambridge University Press,
1990). ISBN 0-521-36413-2 (Hardcover) ISBN 0-521-43804-7 (Paperback)
- Thomas Powers. Heisenberg's War: The Secret History of the German Bomb (Knopf) ISBN 0-394-51411-4 (Hardcover) ISBN
0-316-71623-5 (Paperback)
- Paul Lawrence Rose. Heisenberg and the Nazi Atomic Bomb Project, 1939-1945: A Study in German Culture. University of
California Press, 1998, ISBN 0-520-21077-8
- Heisenberg, Werner. Across the frontiers ; translated from the German by Peter Heath. (Ox Bow Press, 1990) ISBN
0-918024-80-3 (Hardcover) ISBN 0-918024-81-1 (Paperback)
- -- Encounters with Einstein: and other essays on people, places, and particles. Princeton University Press; Reprint
edition (October 1, 1989) ISBN 0-691-02433-2
- -- Introduction to the unified field theory of elementary particles. 1966
- -- Natural law and the structure of matter English version by the author. 1970 Warm Wind Books (July 1, 1981) ISBN
0-900615-27-3
- -- Nuclear physics. 1953
- -- et al ,On modern physics. English translation by M. Goodman and J.W. Binns. 1961
- -- Philosophic problems of nuclear science. Translated by F. C. Hayes. 1952; Ox Bow Press (June 1, 1979) ISBN
0-918024-14-5 (Hardcover) ISBN 0-918024-15-3 (Paperback)
- -- Physical principles of the quantum theory, translated into English by Carl Eckart and Frank C. Hoyt ... 1930
- -- Physicist's conception of nature. Translated from the German by Arnold J. Pomerans. Greenwood Press Reprint (March
9, 1970) ISBN 0-8371-3107-3
- -- Physics and beyond; encounters and conversations. Translated from the German by Arnold J. Pomerans. 1971 ISBN
0-04-925020-5
- -- Physics and philosophy : the revolution in modern science, introduction by F.S.C. Northrop. 1999 ISBN
1-57392-694-9 (Paperback) ISBN 0-06-130549-9 (also Paperback)
- -- Tradition in science. 1981 Continuum Intl Pub Group (November 1, 1982) ISBN 0-8264-0063-9
- -- Two lectures. 1949
- -- et al. Uncertainty principle and foundations of quantum mechanics : a fifty years' survey, edited by William
C. Price, Seymour S. Chissick. 1977
- -- The Part and The Whole about his life, his friendship with Bohr,
and the evolution of quantum physics.
External links
Wikimedia Commons has media related to:
Wikiquote has a collection of quotations related to:
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
