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The Nazi Bomb

Failures of the German Nuclear program

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By: John Amacher

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Though the work will not lead in a short time towards the practical use of engines or explosives, it gives on the other hand the certainty that in this field the enemy powers can not have any surprise in store for us. [1] This is an excerpt from a July 1943 letter from Rudolph Mentzel, the head of war research in Germany during World War II, to Reichsmarshal Goering about the state of the German atomic weapons program. The letter shows the most significant problem the Germans faced in their development of a nuclear weapon: themselves. This letter was sent six months after Enrico Fermi produced a stable chain reaction at the University of Chicago. The German physicists had to deal with a regime that cared little for their research, and never made a concerted effort to centralize it. Coupled with poor management, the overconfidence of the Germans involved slowed research to a snails pace in Germany, while the fear of a Nazi nuclear weapon pushed research into high gear in the United States. [2] The German scientists would not learn how much they had underestimated their enemy until August 6, 1945, when the BBC announced that the United States had dropped an atomic bomb on Japan.

German Science was viewed as the most advanced in the world before and during World War II. The German Chemist Otto Hahn discovered nuclear fission in 1938, leading the rest of the world to believe that the Germans would stay ahead of them in this field. It stood to reason therefore that the Germans not only had a head start in nuclear research, but also were better equipped to deal with the problem. An Allied mission called Operation Alsos proved this untrue.

Operation Alsos, which was headed on the scientific side by physicist Samuel Goudsmit, sent a team of researchers to Europe in June of 1944 to determine how far Germany had progressed in the building of a nuclear weapon. By late November 1944 it became clear to the scientists and soldiers assigned to Alsos that the German nuclear scientists were nowhere near reaching their goal of an atomic bomb. The German physicists under Werner Heisenbergs command had been evacuated from Berlin to a small village named Hechingen. There they continued their attempt to build a nuclear reactor in the wine cellar of their new home.[3] The reasons behind the German failure have been hypothesized and debated by scientists and historians since shortly after the discovery was made. The debate continues today with new evidence being found on a regular basis. While scientific failures are usually not debated with such intensity, the issue of the German atomic bomb has led to the publication of a large amount of scholarly work.

Among the sources I used for this article were a variety of books and articles such as Samuel Goudsmits Alsos (1947) and Robert Jungks Brighter than a Thousand Suns (1956). I also examined letters written between two influential physicists, the Danish Niels Bohr and the German Werner Heisenberg. In addition, I used a book by Jeremy Bernstein called Hitlers Uranium Club (1996), which includes the edited transcripts of tape-recorded conversations between the German scientists who were captured in operation Alsos. These were called the Farm Hall transcripts, after the house in Great Britain where they were held captive for six months in 1945. Alsos is an excellent book that was written shortly after the events took place, by the leading scientist in Operation Alsos. One must however, take into account Goudsmits negative feelings towards Germans. Goudsmit was a Dutch Jew who had received a farewell letter from [his] mother and father bearing the address of a Nazi concentration camp.[4] Jungk tends to argue for the German physicists claims that they deliberately failed in building a bomb. Walkers German National Socialism and the Quest for Nuclear Power , and Bernsteins Hitlers Uranium Club are less partial and give a more objective view.

While there are other important reasons for the failure of the Nazi nuclear program, I believe the most important has to do with the attitudes of the regime and the scientists themselves. I believe the Nazi sense of superiority could be seen in every aspect of German life. This attitude made the government discount the importance of nuclear research, and kept the scientists from trying as hard as they might have. I believe most other reasons for the failure are directly related to this reason. It can be seen by advances made in cancer research, rocket science, and jet engine science along with other so-called Aryan Sciences, that when the regime took an interest, science flourished under Nazi rule.[5] This did not hold true for nuclear physics. The regime did not see its value until it was too late, and the scientists did not lobby for their science because they thought any advances were too far off to be interesting to the government. In the end, because of the lack of interest, Hitler lost a chance to build one of his much sought after super-weapons that could have won his war with ease.

A Brief History

The path of discovery that led to fission and nuclear weapons started in the early twentieth century when Ernest Rutherford discovered the composition of the atom. In 1932, Rutherfords disciple James Chadwick hypothesized that the phantom third particle in an atom was a separate elementary particle with a neutral charge that he called a neutron. In 1934 Enrico Fermi had the idea to bombard elements using neutrons, which because of their neutral charge would not be repelled by the elements. When he reached uranium, he viewed a change in the element, and thought he had produced a transuranic (an element more massive than uranium). Unknowingly he actually fissioned or split the element.[6]

Fermi continued this research and in October of 1934 put paraffin wax between the uranium and the neutrons. He discovered that the paraffin acted as a moderator, slowing the oncoming neutrons, and changing the rate at which the nuclear reaction took place. Because he used aluminum shielding to protect from radiation, Fermi was still unable to observe the fission he was creating. The theorist Niels Bohr found Fermis results interesting and used them to invent a model of the atom. He theorized that the atom acted like a drop of water, and if something interacted with it the atom could lose its shape or even break apart. Bohrs theory was published in 1937, giving physicists a blueprint to explain the fission of an atom.[7]

In 1938 Germany, radiochemist Otto Hahn was working with Lise Meitner, a physicist, on irradiating uranium with slow neutrons. When Hitler annexed Meitners homeland, Austria, she was forced to flee because of her Jewish descent. Hahn continued his work with Fritz Strassmann and kept Meitner informed of their discoveries. Hahn expected to find that when uranium was irradiated the product would be an element close to it on the periodic table, such as radium. But time after time his experiments yielded a substance that was chemically indistinguishable from barium which is nearly half as massive as uranium. Hahn revealed his findings to Meitner in December of 1938, and she, along with her Nephew Otto Frisch began to hypothesize that perhaps this fit in with Bohrs water droplet theory of the atom. She wrote to Hahn with their ideas, and together they came up with a working theory.[8]

If their theories were true, the energy released from a single uranium atom fissioning would be massive. They calculated that 2.2 pounds of uranium completely fissioned would release energy equivalent to ten thousand tons of TNT. Bohr was told of their results and realized from Hahns experiments that only the rare isotope uranium 235 underwent the fissioning process. For that reason it became clear that in order to create a weapon, or a reliable reactor, one would have to separate the uranium isotopes. American Physicist Leo Szilard had theorized that in order for a chain reaction to be sustained, each uranium atom must release at least two neutrons. His theory was proven correct in March of 1939 when it was found that on average, 2.42 neutrons were released from each uranium atom. These latest theoretical findings made the possibility of building an atomic weapon a feasible goal.[9]

At nearly the same time in the United States and Germany, physicists alerted their governments to the possibility of producing a bomb from uranium. Some sort of state-sponsored research was started in both nations. It was believed by both nations that because fission was discovered in Germany, the Germans had a head start.[10] This belief was not unfounded, and it led to both nations making false assumptions. The Americans perceived a need to catch up and develop the first bomb. Albert Einsteins famous letter in August of 1939, urged Franklin Roosevelt start the Americans building a bomb quickly in order to beat the Germans to the punch.

I understand Germany has actually stopped the sale of uranium from the Czechoslovakia mines which she has taken over. That she should have taken such early action might perhaps be understood on the ground 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 being repeated.[11]

The same belief that threw the United States headlong into nuclear research gave the German physicists a sense of security. The Americans quickly caught up and passed the German effort.

Miscalculations

On September 16, 1939, a group of prominent German physicists who would be called the Uranverein or Uranium Club, met at the war office in Berlin to calculate the possibility of building a nuclear reactor and an atomic weapon. They agreed it would be difficult and virtually unattainable in the near future, given the amount of government support they predicted. They decided that they must proceed with their study anyway, in the words of Hans Geiger, Gentlemen there is a chance that nuclear energy could be released by fission if there is only a trace of a chance then we have to do it. We cant avoid it.[12] It was decided that the physicists would work on the problem for the government.[13]

After this meeting, Heisenberg produced two technical reports on the problem of nuclear fission. His December 6, 1939 report assessed the feasibility of a stable reactor using uranium 235, and the explosive power of a uranium bomb. Using Heisenbergs calculations, in January of 1941 Walther Bothe experimented with making a reactor with graphite as the moderator. He did not realize that the industrial grade graphite he used was not pure enough to be used as a moderator, because of this his experiment failed. For the remainder of the war the Germans were forced to use the much more scarce heavy water as a moderator.[14] Heisenbergs second, more detailed report followed on February 29, 1940. It incorrectly stated that graphite would not work as a moderator. With his two reports, Heisenberg became Germanys authority on nuclear fission and his findings became the blueprint for the German nuclear project. He judged that for a stable reaction, one metric ton of graphite must be assembled with two to three tons of uranium 235 and 600 liters of heavy water. His estimate about the amount of uranium needed was way off (one needs only about 50 kilos of uranium), as was his supposition that graphite could not be used as a moderator.[15] Unfortunately for German physics, his contemporaries did not disprove Heisenbergs theories.

The Regime

With a few miscalculations, Heisenberg inadvertently perpetuated the belief that an atomic bomb was out of reach for Germanys near future, while in the United States this belief fell by the wayside. One main reason Heisenbergs theories perpetuated was lack of central leadership. Thomas Powers explains the situation in Germany well:

For convenience we may speak of the German bomb program as if it were a coherent organization marching to a single drummer, but Uranium Club comes closer to defining the unruly mailing list of competing [German] scientists whose only shared hope was to survive the war.[16]

While in America the government took control and made a concerted effort, in Germany control was passed between many different institutions, and at times was under the control of more than one government agency.[17]

The Nazi regime made it difficult for nuclear physics to thrive in Germany. Goudsmit argues that science has trouble surviving in a fascist regime; The failure of German nuclear physics can in large measure be attributed to the totalitarian climate in which it lived.[18] His argument has merit, but he overlooks the early success of nuclear physics in Germany, as well as that of other sciences. A few tendencies and policies did a large amount of the damage to the German nuclear effort. The Nazi State deported numerous Jews and undesirables from the universities. Theoretical physics was labeled as Jewish Science, which dropped its funding, and made it less popular to new students. Few replacements among new students arose to account for the purge of Jewish academics. The Nazis steadfast belief in a short war, combined with its managed economy, created a negative environment for scientific study. On top of this, the scientists themselves gave no reason for the state to believe nuclear weapons were possible. Goudsmit Wrote: They forgot that they themselves had not been very convinced of their own chances of success.[19] Together these reasons created an atmosphere that led to a lack of progress in nuclear physics.

The Nazi persecution of Jews reached into every aspect of society, and Physics was not exempt. By 1935 one out of four physicists had been driven from their posts,[20] forcing nearly 2,000 academics (most of them Jewish) to emigrate.[21] These losses hurt nuclear physics tremendously, as many of Germanys top minds left the country. National Socialism created a belief in the uselessness of theoretical sciences.[22] The Nazi Nobel laureate in physics Philipp Lenard claimed that Einstein's work was peculiar physics, and that Einstein and other Jewish scientists were overly concerned with theory.[23] It was believed by the Nazi Regime that there was no promise of weapons from theoretical physics. As historian Jonathan Harwood writes,

Campaigns for an "Aryan" or "German" science were much stronger in some disciplines than others has generally been attributed to the extent of a discipline's perceived utility to industry or the military. Thus, theoretical physics was suspect, not just because of its many Jewish practitioners, but also because of its apparent lack of utility.[24]

Theoretical physics was not welcomed by National Socialism for some time. The State only started to see prospects of nuclear physics in the middle of World War II.

In addition to the lack of respect came a lack of necessity. Even though it had been assumed early on that uranium could provide a power source and perhaps a weapon, the regime felt it had the weapons it needed. Jungk writes, On the outbreak of war the German leaders erroneously believed that they could achieve final victory with the weapons they already had.[25] Weapons research was not a necessity in the Reich until the Germans started losing the war. Jungk points out that It was not until 1942 that the development of new weapons attracted any attention in the Reich.[26]

The changes made by the Nazis to the German economy managed to bring Germany out of the depression, but they did not rework it into a war economy. It was acceptable for a short war, but a long drawn-out conflict showed its limitations. In addition, the managed economy (gelenkte Wirtschaft) that emerged in Germany in the late 1930s introduced layer upon layer of economic bureaucracy.[27] The bureaucracy of the Nazi economy worked to slow industry and scientific research. The Regime stifled initiatives from industry and science and created a slow and cumbersome apparatus of control without any clear central authority.[28] The German scientists decided that their primary goal in the National Socialist state was to guard their science and themselves from destruction by the State or the war.

The Scientists

Powers argument that the German physicists were mainly interested in surviving the war seems correct. Many of the scientists who were truly capable in the field of nuclear physics were not members of the Nazi party. Of those who were, many joined to keep their job, not for love of the party. Most did not fight against the regime, however, most also did not follow the party line. Only a few physicists joined the party, and fewer still believed. The regime that was hostile to nuclear physics never gained the support of most German nuclear physicists (with good reason). Jonathan Harwood points out that the great majority of scientists were neither ideologically committed Nazis nor political opponents, in fact they were politically indifferent individuals whose primary concern was the well-being of their discipline.[29] There was negligible resistance from academia to the Nazi takeover. The only opposition came when the scientist own research was threatened, lending credence to the belief that the scientists loyalties were to their limited branches of science and not even academia as a whole.[30]

Once the Allies invaded the European continent in June 1944, the Alsos team captured locations and individuals deemed important to German science. The evidence gathered on the state of the Nazi Nuclear program showed how far behind the German physicists had been. The attitudes of the German scientists made for an amusing and ironic situation for the investigators. Goudsmit wrote:

They (German physicists) ascribed our special interest in them to their supposed vastly important work in nuclear physics The situation was indeed ironic, but we were to meet again and again in our encounters with German scientists. To the very end they remained serenely confident of the superiority of German Science.[31]

The scientists continued to believe in their own superiority and importance when they were taken to Britain for internment. Even the Germans internment perpetuated their belief in their superiority--Why else would the Allies want them? Although they were not in the top of their class any longer, these men were still extremely intelligent physicists. One reason was to keep them out of other nations hands, such as Russia and France. Another reason was that the Allies were looking for scientists to help German science proceed past the Nazi era. Hahn and von Laue, because of their anti-Nazi wartime activity, were interned because Goudsmit and others in Allied circles would have liked to place them in charge of German science.

I strongly recommend that they [Hahn and von Laue] be given an early

opportunity to confer with Allied colleagues on the state of science in Germany before and during the war If any small-scale revival of German scientific education occurs it would be desirable to have these men in key positions.[32]

The Germans, oblivious to the real reasons for their internment, continued believing in their superiority. There are many instances in the Farm Hall transcripts when the scientists show just how important they considered themselves, and how incorrect they were about many scientific matters. In one instance Carl Friedrich von Weizsäcker says, These people have detained us firstly because they think we are dangerous; that we have really done a lot with uranium.[33] Throughout the text, the Germans discussed ideas and theories as if they were new while in reality they had been known to the Allies for years.

In conversations between the scientists interned at Farm Hall a great deal can be learned about the extent of their knowledge of nuclear physics. Although they seemed to have many of the right ideas, they still debated and fumbled with theories that Allied scientists had already proven correct or incorrect. Two of the physicists interned, Erich Bagge and Horst Korsching discussed the progress made in isotope separation, but did not know yet how to do it. They end their discussion assuming that the Allies would want the apparatus they were using to attempt separation, even though they were unsuccessful.[34] In another segment Bagge, Otto Hahn, and Max von Laue discussed how Plutonium is formed. While Bagge was on the right track, the other two find fault in his logic. When they were in captivity, it became clear that the German scientists had not discovered the very first steps to building a nuclear weapon.[35]

During their captivity in Farm Hall, the scientists made many references to the conferences between the Big Three (Stalin, Churchill, and Roosevelt). The scientists seemed to believe that they were so important that their future was being discussed in the conferences. Kurt Diebner and Weizsäcker among others, made remarks such as I imagine that they will decide at the Big Three conference which scientists are to go to Russia.[36] And I would say we must wait for the Big Three. The whole thing is connected with that.[37] Statements like this show the continued high opinion in which the German physicists held themselves. The news of an atomic bomb being dropped by the United States brought reality crashing down on the German physicists interned at Farm Hall.

Rewriting Failure

Shortly before dinner on the sixth of August I informed Professor Hahn that an announcement had been made by the BBC that an atomic bomb had been dropped.[38] At this point came a period of disbelief at Farm Hall. The scientists simply would not believe that the Americans had succeeded where they had failed. After dinner they crowded around the radio and heard a full report. At this point, the full data of the bomb was released and there was no doubt among the scientists that the Americans had succeeded. In the following two days there were a great many conversations between the Germans about the logistics and their reasons for failure. It was still very apparent that they did not understand the complete workings of the bomb or a reactor, but they were piecing things together.[39]

Of the men who were there all but von Laue were in the Uranium Club. Of those in the Uranium Club, Otto Hahn (the discoverer of fission) was the only one to show definite reservations about building a bomb in their first meeting September 16, 1939.[40] After reluctantly agreeing to join the club, he said to Weizsäcker, but if my work should lead to a nuclear weapon, I would kill myself.[41] Proven by their own recorded words, the other members of the Uranium Club definitely participated in the German bomb project in an effort to build a weapon.

Later Heisenberg refuted his role in the bomb project. In a 1965 interview with historian David Irving, Heisenberg said: In Germany it was different: Everyone here had to be convinced that it would be horrible to put something like that into Hitlers hands.[42] The revisionist history given by the German scientists who worked on the German bomb project told of physicists sabotaging research to prevent a bomb from being built. While this would be a noble goal if it were true, it seems apparent that it is not. The Farm Hall documents, and letters drafted in the 1950s and 1960s by Niels Bohr about his 1941 meeting with Heisenberg and Weizsäcker give evidence that the Germans did indeed try to build an atomic weapon.

In 1941 Heisenberg went to Denmark to meet his longtime friend and mentor Niels Bohr. When he was there they discussed nuclear research and the war, and on both accounts Heisenberg was optimistic.[43] After the Danish publication of Jungks book Brighter than a Thousand Suns in 1957, Bohr wrote him discussing his memory of the meeting. Bohr wrote: You and Weizsäcker expressed your definite conviction that Germany would win and that it was therefore quite foolish for us to maintain the hope of a different outcome of the war.[44] On the subject of nuclear weapons research, Bohr said:

I also remember quite clearly our conversation in my room at the Institute, where in vague terms you spoke in a manner that could only give me the firm impression that, under your leadership, everything was being done in Germany to develop atomic weapons[45]

In the Farm Hall transcripts Heisenberg said that the first time large funds were made available in Germany was in the spring of 1942 after the meeting with Rust when we convinced him that we had absolutely definite proof that it could be done.[46] In another section, Weizsäcker and Hahn were speaking about the German project, I think the reason we didnt do it was because all the physicists didnt want to do it, on principle. If we had all wanted Germany to win the war we would have succeeded. To this statement Hahn replied, I dont believe that but I am thankful we didnt succeed.[47] The reality of the situation was then summarized by Heisenberg:

The point is that the whole structure of the relationship between the scientists and the state in Germany was such that although we were not 100% anxious to do it, on the other hand we were so little trusted by the state that even if we wanted to do it it would not have been easy to get it through.[48]

It is clear that the Germans did try to build a nuclear weapon, and that they failed in doing so. It would seem that some of the scientists may have had some reservations about the project, but it did not stop it from proceeding. Their later argument that they were deliberately trying to sabotage the project is unlikely. There were already undertones of this argument during their last days at Farm Hall. After the war there were obvious reasons for claiming to work against the Nazis, and it is understandable that these scientists made their claims.

Conclusion

Without a historical context, it is difficult to understand the debate over the lack of a Nazi nuclear weapon. But when one looks at Germany in the 1920s and 1930s, one sees a scientific powerhouse. Nazism, it is important to remember, took root in the world's most powerful scientific culture, one that boasted nearly a third of the world's Nobel prizes in science.[49] Academics flocked to Germany before and during the early Nazi years. Germans held a large percentage of the world's patents. German science and medicine were the envy of the world long before the Nazis came to power.[50] It could therefore be reasoned that the decline in science in general, and nuclear physics in particular, was due to the Nazi regimes assumption of power.

The Nazi regimes relationship to scientific research was not as simple as the above decline might imply. During the Nazi era:

Certain kinds of science flourished, while others were destroyed Sciences of an applied, practical nature were particularly encouraged, as were the hands-on disciplines, including medicine At the same time, many of the most abstract scientific fields were condemned--much to the benefit, as it turned out, of the Allies.[51]

This dichotomy between what the Nazis found important and what they did not, led to the delay of their nuclear bomb project. The German physicists refused to see this shortcoming, and remained extremely confident in their superiority. The Nazi society that gave the world jet engines, guided missiles, and advances in the television and electronic computers, failed in producing a stable nuclear reaction.[52] The issue of the German nuclear bomb continues to be a disputed topic among historians regardless of how close the German effort came. Historians are looking at what might have been if German nuclear physics was successful in their task. What if the Germans had managed to build a nuclear weapon? Do we want to imagine a world in which Hitler was a nuclear power?

Bibliography

Books:

Bernstein, Jeremy, Hitlers Uranium Club: The Secret Recordings

at Farm Hall (Copernicus Books, New York, 2001). This is an excellent source for examining what the scientist knew. Also contains a good bibliography.

Goudsmit, Samuel, Alsos (Henry Schuman Inc., New York, 1947). A

good text, written by a man who was there during the first discoveries of the Nazis atomic bomb progress. Goudsmit is a Jew, and tends to write harshly about most of the German scientists.

Jungk, Robert, Brighter than a Thousand Suns: A Personal History

of the Atomic Scientists (Harcourt Brace & Co. Orlando, FL., 1958). Jungk takes the side that the Germans sabotaged the production of nuclear weapons. Includes a good history.

Irving, David, The German Atomic Bomb: The History of Nuclear

Research in Nazi Germany (Simon and Schuster, New York, 1967). Revisionist history, used only as background reading, when facts could be backed-up from other sources.

MacPherson, Malcolm C., Time Bomb: Fermi, Heisenberg, and the

Race for the Atomic Bomb (E. P. Dutton, New York, 1986). Also only used as background reading.

Macrakis, Kristie, Surviving the Swastika: Scientific Research

in Nazi Germany (Oxford University Press, New York, 1993). I could not find this book in time, looks to be good for a comparison of the sciences.

Powers, Thomas, Heisenbergs War: The Secret history of the

German Bomb (Alfred A. Knopf, Inc., New York, 1993). Like Jungk, takes the position that Heisenberg may have sabotaged. Contains good sources.

Walker, Mark, German National Socialism and the Quest for

Nuclear Power (Cambridge University Press, New York, 1989). Another good history of the German project, well written.

Essays and articles:

Harwood, Jonathan, German Science and Technology under National

Socialism. Perspectives on Science , vol.5, no.1 (Spring, 1997):128.

Overy, Richard, The Nazi Economy; Was it Geared for War?

History Review , no.31, (September, 1998):4. Cited only a small amount from this article. Good review of the Nazi economy.

Proctor, Robert N., Bitter Pill, Nazi Research on Cancer and

Public Health. Sciences , v39, n3 (May, 1999):14. Proctor gives a good argument for the success of certain types of Nazi science.

Proctor, Robert N., Nazi Science and Nazi Medical Ethics: Some

Myths and Misconceptions. Perspectives in Biology and Medicine , vol.43, no.3 (Spring, 2000):335.

Rose, Paul Lawrence, Did Heisenberg Misconceive A-Bomb?

Physics Today 45, (February), 126 (1992).

Websites:

Aaserud, Finn, Niels Bohr Archive, released 2/6/02, Release of

documents relating to 1941 Bohr-Heisenberg meeting , February, 2002 <http://www.nbi.dk/NBA/webpage.html> (February 12, 2002).

World Government Documents Archive, Declassified Documents

Reference System-US <http://www.ddrs.psmedia.com/> (February 18, 2002). This site contains CIA biographies of many of the top German scientists, and their usefulness as scientists to other nations.





[5] Proctor, Robert N., Nazi Science and Nazi Medical Ethics: Some

[6] Much of the historical facts are taken from Bernsteins book. The footnotes at the end of each paragraph represent the relative location of each part of the history within Bernsteins work. Bernstein, Jeremy, Hitlers Uranium Club: The Secret Recordings at Farm Hall (Copernicus Books, New York, 2001). pp.4-7.

[20] Walker, Mark, German National Socialism and the Quest for Nuclear Power (Cambridge University Press, New York, 1989). p.9.

[21] Harwood, Jonathan, German Science and Technology under National

[26] Jungk, Brighter than a Thousand Suns , 1958, p.87.

[43] Document 1, this is a draft of letter from Bohr to Heisenberg that was never sent. It is in the handwriting of Niels Bohr's assistant, Aage Petersen. It is undated, but written after the first publication, in 1957, of the Danish translation of Robert Jungk, Heller als Tausend Sonnen ( Brighter that a Thousand Suns ), the first edition of Jungk's book to contain Heisenberg's letter. Three numbered pages. Aaserud, Finn, Niels Bohr Archive, released 2/6/02, Release of documents relating to 1941 Bohr-Heisenberg meeting , February, 2002 <http://www.nbi.dk/NBA/webpage.html> (February 12, 2002).p.1.