El encuentro de Copenhague

Two Letters from Werner Heisenberg to Robert Jungk,

the author of "Brighter Than a Thousand Suns".



November 17, 1956



Dear Dr. Jungk,



I want to thank you very much for having your publisher send me a copy of your fine and interesting book about the atomic scientists. Since I have been sick these last few days, I had the opportunity to read it through in its entirety and I find that, overall, you characterized the atmosphere among the atomic scientists very well. The fact that you have addressed a few delicate issues may perhaps present some difficulties also for one or the other of them. But these dangers are likely not very great. That you printed the Frank (sic!) report and Bohr's memorandum to Roosevelt at the end seems to me a special distinction of your book. For in retrospect one can hardly deny that right there the natural scientists were better at judging and analyzing the political processes than the statesmen of that time.

Nevertheless, in some details of your book I need to make a few little remarks which may serve you in a second printing by correcting minor mistakes (which tend to be unavoidable with such an undertaking).

First on page 52: This point is really quite important to me. You describe Weizsäcker's political conviction (I assume perhaps derived from conversations with Teller) and near the end you word it "He (Teller) had to assume that his old friend and fellow student would stay loyal to Hitler." Although the subsequent sentence then disputes this assertion, I do believe that the above sentence conveys a completely false impression of Weizsäcker's political conviction. I saw Weizsäcker almost daily during the years 1931 to 1935 and am probably more familiar with his political opinions back then than anyone else. First off, Weizsäcker loathed Hitler's personality and the crimes committed by his movement just as much as any other decent human being. To this revulsion undiminished later on as well, there may have, over time, been added a mix of horrified admiration, when he saw from up close (through his family) how Hitler managed to twist power out of the hands of all those highly qualified people whose efforts were directed towards positive ends in German politics, and how, in addition, he was given from abroad practically without resistance the very concessions that Brüning and Stresemann had always sought in vain. To speak of any kind of loyal feelings from Weizsäcker towards Hitler is quite certainly far off.

With the beginning of the war there arose of course for every German physicist the dreadful dilemma that each of his actions meant either a victory for Hitler or a defeat of Germany, and of course both alternatives presented themselves to us as appalling. Actually, I suppose that a similar dilemma must have existed for the physicists active on the allies' side as well, for once they were signed on during the war, they also were signed on for Stalin's victory and Russia's foray into Europe. Overall, the German physicists acted in this dilemma as conservators of sort of that which was worthy and in need of conserving, and to wait out the end of the catastrophe if one was lucky enough to still be around.

Further: page 91. I can remember the meeting with Fermi in Goudsmit's home quite well, but not at all that Fermi would have mentioned the Uranium problem. The possibility that atomic weapons might already be used in the coming war, I certainly did not consider seriously at that time; perhaps repressed it out of an inner antiestéticar. At any rate, I cannot remember, as I said, the mention of the Uranium problem, and maybe that lack of memory itself is a sign of the repression back then. The conversation with Pegram only took place somewhat later, and I told Pegram at the time with utter conviction that Hitler would lose the coming war, yet I felt I needed to stay in Germany to contribute to preserving the good in as much as it still existed. During this conversation as well, I did not seriously consider that the atomic bomb would possibly be part of a war with Hitler. On the one hand, I was hoping that the war would end sooner and on the other hand, I had a gut feeling that the difficulties with the construction of an atomic bomb (which I had not given any thought to at that time) would be extremely great.

About p.100. You are talking here near the end of the second paragraph of active resistance against Hitler, and I believe - I apologize for writing this so directly - that this passage bespeaks a complete misunderstanding of a totalitarian dictatorship. In a dictatorship active resistance can only be used by people who are perceived as participants in the system. If someone speaks publicly against the system, he most certainly is robbing himself of any possibility of active resistance. Because either he utters this criticism of the system only occasionally in a politically harmless fashion, then his political influence can be easily blocked; for instance with young people one can spread the word: Oh well, the old Professor X may be a nice old man, but of course he is incapable of understanding the enthusiasm of youth, or such thing. Or else, the dissident actually tries to motivate students for political action, then he would within a few days end up in a concentration camp, and even his martyr death would remain practically unknown because to speak of him is not allowed. I do not wish to have this remark misconstrued to imply that I myself have been in a resistance move against Hitler. On the contrary, I have always felt very ashamed before the people of July 20th, (some of whom were my friends), who at the time have put their effort into serious resistance, sacrificing their lives. But even their example shows that real resistance can only come from people who appear to be going along. Our most famous example was Canaris, who, by the way, also at times assisted us in retaining our circle of physicists.

About page 175: In the little episode during my bicycle trip to Urfeld, circumstances were as ***ows. Since all male civilians were drafted to the "Volkssturm", it was not an uncommon occurrence that these civilians fled from the front to the back country. To prevent this, the SS had posted SS guards at the roads to capture such fugitives, whereupon not infrequently they were hanged without a lengthy military tribunal. I had basically prepared for this peril by getting an identity document from the institute. An SS man recognized, however, that such a document could be fashioned quite easily at the institute and told me he would have to bring me in front of his commanding officer. This dangerous turn I was able to prevent by bribing him with the package of Pall-Mall cigarettes. By the way, my departure from the institute was of course neither a flight from the troops of Colonel Pash, nor from the "Volkssturm"; it was prepared carefully at the institute and only conceived out of my belief that I needed to be at the side of my family during the time of the final battles. Therefore I had remained in Hechingen until the moment when the "Volkssturm" was already dissolved and the French tanks were rolling in. I then drove off at 3 am from Hechingen on my bicycle.

Now for a few minor details: On p.177 it should read Urfeld, not Urbach. On p.224: I have read almost all the works by the English novelist Anthony Trollope, not Tobias Smollet. And finally p. 225: At the first report, I indeed did not believe in the atomic bomb, because I knew what incredible technical effort was needed to produce atomic bombs. Only at the second radio report where precisely that huge effort was reported, did I come to terms with the fact that in America actually many Billions had been spent on the atomic bomb and that hundreds of thousands of people had worked on it. The idea that the Americans had dropped a pile, I certainly did not consider seriously after the second broadcast, since that would have had only a very limited effect through radio- active contamination. And also because it would have been, in fact, quite simple since we took it for granted that the Americans could produce piles very easily should they be interested in them. But the difference between pile and bomb was completely clear to us, and, I believe, already the next day in a seminar we calculated the approximate dimensions and the workings of a bomb. Perhaps I may mention in connection to this that once in 1944, an emissary from Goering came to my institute, indicated that news had come to Germany through espionage that the Americans were close to dropping an atomic bomb over German territory, and he asked me whether I thought this was possible. I replied at the time that although I thought it still very unlikely at this time (summer 1944), since the production of the atomic bomb necessitated quite an enormous technical effort, I could, however, not completely rule it out.

p.227: The final sentence of the British officer was not addressed to Hahn; actually, Hahn was not present at this conversation at all, and I am firmly convinced that out of sheer tact even the British officer would not have answered in this fashion. This was a conversation taking place between, if I remember correctly, the British officer, Weizsäcker, and me. In this conversation which dealt with the jovenlandesal right of the bombing, the officer eventually felt, in a kind of discomfiture, pressed to the statement that we ought to understand: to them the life of a British or an American soldier was more important than the lives of 70 000 Japanese civilians. One of us then replied "But there you are really very close to the jovenlandesal terms of Herr Hitler". The officer, with whom we had otherwise been on very friendly terms, left us upon this with a very disturbed expression on his face. Very obviously the officer had not meant to wound us with his assertion, and probably he himself was later rather unhappy over this statement.

It would be nice if you could include a few corrections at the second printing, and I assume that you will get suggestions for such corrections from other atomic scientists as well. Once again many thanks for your interesting book.



With many regards

Yours

(Signed)





Los Angeles

12-29-56



Dear and Highly Esteemed Professor Heisenberg,

I want to thank you very much for your kind letter with the accompanying corrections. On January 15th a new edition of my book will appear in which I have already taken note of this communication.

Some of it, however, I was only able to include as a "footnote", in order to not disturb the "layout" too much. In January and February, I am now going to work on the English language edition which will appear in Great Britain with two publishers simultaneously (Gollancz and Hart-Davis) and in the USA with Harcourt, Brace and Co. The book will appear in France already in the spring and in the fall in all West-European countries.

Should you - aside from the corrections- have the desire or the inclination to help fill in one of the many gaps which my book still has of course, I would be very grateful for it. In particular, it would be of interest to me to learn more precisely about your Copenhagen conversation with Bohr during the Second World War. Also I would have liked to know more about the false alarm after the war, when two alleged agents who were later discovered to be frauds, were threatening to abduct you from Göttingen.

Only on one point was I not able to accommodate your letter. Mr von Weizsäcker himself told me a while back in Göttingen that although he had a loathing for the leaders of this "movement"(that is, not just after 1939), in its beginnings he had a certain sympathy or, let's say, understanding for National Socialism, because it appeared to him that there was the thrust of profound forces operating here. For this attitude I have had and still have quite a bit of understanding, since I have lived in and with the German Youth Movement, whose criticism of "intellectualism" was captured by the Nazis and forged into such a crudely mindless weapon.

By the way, my hope is that in the USA my book will also clear up the myth of the "nancy" Heisenberg, which Norbert Wiener only a few months ago has warmed up again in the second volume of his autobiography.

With warm wishes for the coming year, I am respectfully

Yours,

(Signed) Robert Jungk









Jan. 18th, 1957

Dear Dr. Jungk!

Many thanks for your letter, asking me to write in a little more detail about my Copenhagen conversations with Bohr during WWII. In my memory which may, of course, deceive me after such a long time, the conversation roughly unfolded the ***owing way. My visit to Copenhagen took place in the fall of 1941; I seem to remember that it was about the end of October. At that time, as a result of our experiments with uranium and heavy water, we in our "Uranium Club" had come to the ***owing conclusion: It will definitely be possible to build a reactor from uranium and heavy water which produces energy. In this reactor (based on a theoretical work by v. Weizsäcker) a decay product of 239-uranium will be produced which just like 235-Uranium is a suitable explosive in atomic bombs. We did not know a process for obtaining of 235-Uranium with the resources available under wartime conditions in Germany, in quantities worth mentioning. Even the production of nuclear explosives from reactors obviously could only be achieved by running huge reactors for years on end. Thus we were quite clear on the fact that the production of atomic bombs would be possible only with enormous technical resources. So we knew that in principle atomic bombs could be built, although we estimated the necessary technical effort to be even rather larger than in the end it turned out to have been. This situation seemed to us to be an especially favorable precondition as it enabled the physicists to influence further developments. For, had the production of atomic bombs been impossible, the problem would not have arisen at all; but had it been easy, then the physicists definitely could not have prevented their production. The actual givens of the situation, however, gave the physicists at that moment in time a decisive amount of influence over the subsequent events, since they had good arguments for their administrations - atomic bombs probably would not come into play in the course of the war, or else that using every conceivable effort it might yet be possible to bring them into play. That both kinds of arguments were factually fully justified was shown by the subsequent development; for, in fact, the Americans could not employ the atomic bomb against Germany any more. In this situation we believed that a talk with Bohr might be of value. This talk then took place on an evening walk in the city district near Ny-Carlsberg. Because I knew that Bohr was under surveillance by German political operatives and that statements Bohr made about me would most likely be reported back to Germany, I tried to keep the conversation at a level of allusions that would not immediately endanger my life. The conversation probably started by me asking somewhat casually whether it were justifiable that physicists were devoting themselves to the Uranium problem right now during times of war, when one had to at least consider the possibility that progress in this field might lead to very grave consequences for war technology. Bohr immediately grasped the meaning of this question as I gathered from his somewhat startled reaction. He answered, as far as I can remember, with a counter-question "Do you really believe one can utilize Uranium fission for the construction of weapons?" I may have replied "I know that this is possible in principle, but a terrific technical effort might be necessary, which one can hope, will not be realized anymore in this war." Bohr was apparently so shocked by this answer that he assumed I was trying to tell him Germany had made great progress towards manufacturing atomic weapons. In my subsequent attempt to correct this false impression I must not have wholly succeeded in winning Bohr's trust, especially because I only dared to speak in very cautious allusions ( which definitely was a mistake on my part) out of antiestéticar that later on a particular choice of words could be held against me. I then asked Bohr once more whether, in view of the obvious jovenlandesal concerns, it might be possible to get all physicists to agree not to attempt work on atomic bombs, since they could only be produced with a huge technical effort anyhow. But Bohr thought it would be hopeless to exert influence on the actions in the individual countries, and that it was, so to speak, the natural course in this world that the physicists were working in their countries on the production of weapons. For an explanation of this answer one has to include the ***owing complication which, although it was not talked about as far as I can remember, but of which I was conscious, and which may also have been on Bohr's mind, consciously or unconsciously. The prospect of producing atomic bombs while at war was at the time immeasurably greater on the American side than on the German, due to the whole prior history. Since 1933 Germany had lost a number of excellent German physicists through emigration, the laboratories at universities were ancient and poor due to neglect by the government, the gifted young people often were pushed into other professions. In the United States, however, many university institutes since 1932 had been given completely new and modern equipment, and been switched over to nuclear physics. Larger and smaller cyclotrons had been started up in various places, many capable physicists had immigrated and the interest in nuclear physics even on the part of the public was very great. Our proposition that the physicists on both sides should not advance the production of atomic bombs, was thus indirectly, if one wants to exaggerate the point, a proposition in favor of Hitler. The instinctive human position "As a decent human being one cannot make atomic weapons" thus coincided with an advantage for Germany. How far this was influencing Bohr, I cannot know of course. Everything I am writing here is in a sense an after the fact analysis of a very complicated psychological situation, where it is unlikely that every point can be accurate. - I myself was very unhappy over this conversation. The talk was then resumed a few weeks or months later by Jensen, but was equally unsuccessful. Even now, as I am writing this conversation down, I have no good feeling, since the wording of the various statements can certainly not be accurate anymore, and it would require all the fine nuances to accurately recount the actual content of the conversation in its psychological shading.

The second question in your letter concerned the alleged plans for my abduction from Göttingen in the year 1947. This event can in retrospect only be viewed in a humorous vein, of course. It caused a lot of grief for the Britons who had to care for us and guard us, and they even had to relocate us, that is Hahn and me, for a period of some time from Göttingen. Like clockwork there appeared in the middle of the night in front of my Göttingen house two masked figures who had been promised a high reward if they were delivering me to an agent. These two men turned out after their capture to have been two Hamburg harbor workers who wanted to come into some good money on the cheap. In fact, however, the man who had engaged the harbor workers was identical to the one who had informed the British of the whole caper; he was a fraud who wanted to line himself up for a good position in the Secret Service. Only a year later the whole sham blew up and it has given us much to laugh about, naturally.

What you write about Weizsäcker, I can agree on. Only, there is a great deal of difference between this "Understanding for National Socialism in its beginnings" and the terminology "Loyalty towards Hitler" that you have used in your book. Why, one could in the first years very clearly combine a certain "Understanding for National Socialism" with the loathing of the person of its leader, Hitler, by, let's say, being desolate that "A genuine, idealistic desire of the German people was abused by a figure as unsavory as Hitler". The overlap "Hitler equals National Socialism", while proven through the subsequent years, was not yet clear to many Germans in the early beginnings.

Should you revise the passage about my conversation with Bohr in your book, I would be obliged, if I could see the text before publication and make corrections, if necessary.



With many warm greetings,

Yours

(Signed)

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1. tras*lation.

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Dear Heisenberg,
I have seen a book, “Stærkere end tusind sole” [“Brighter than a thousand suns”] by Robert Jungk, recently published in Danish, and I think that I owe it to you to tell you that I am greatly amazed to see how much your memory has deceived you in your letter to the author of the book, excerpts of which are printed in the Danish edition.
Personally, I remember every word of our conversations, which took place on a background of extreme sorrow and tension for us here in Denmark. In particular, it made a strong impression both on Margrethe and me, and on everyone at the Institute that the two of you spoke to, that 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 and to be reticent as regards all German offers of cooperation. 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 and that you said that there was no need to talk about details since you were completely familiar with them and had spent the past two years working more or less exclusively on such preparations. I listened to this without speaking since [a] great matter for mankind was at issue in which, despite our personal friendship, we had to be regarded as representatives of two

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sides engaged in mortal combat. That my silence and gravity, as you write in the letter, could be taken as an expression of shock at your reports that it was possible to make an atomic bomb is a quite peculiar misunderstanding, which must be due to the great tension in your own mind. From the day three years earlier when I realized that slow neutrons could only cause fission in Uranium 235 and not 238, it was of course obvious to me that a bomb with certain effect could be produced by separating the uraniums. In June 1939 I had even given a public lecture in Birmingham about uranium fission, where I talked about the effects of such a bomb but of course added that the technical preparations would be so large that one did not know how soon they could be overcome. If anything in my behaviour could be interpreted as shock, it did not derive from such reports but rather from the news, as I had to understand it, that Germany was participating vigorously in a race to be the first with atomic weapons.
Besides, at the time I knew nothing about how far one had already come in England and America, which I learned only the ***owing year when I was able to go to England after being informed that the German occupation force in Denmark had made preparations for my arrest.
All this is of course just a rendition of what I remember clearly from our conversations, which subsequently were naturally the subject of thorough discussions at the Institute and with other trusted friends in Denmark. It is quite another matter that, at that time and ever since, I have always had the definite impression that you and Weizsäcker

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had arranged the symposium at the German Institute, in which I did not take part myself as a matter of principle, and the visit to us in order to assure yourselves that we suffered no harm and to try in every way to help us in our dangerous situation.
This letter is essentially just between the two of us, but because of the stir the book has already caused in Danish newspapers, I have thought it appropriate to relate the contents of the letter in confidence to the head of the Danish Foreign Office and to Ambassador Duckwitz.

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Shanchito dijo:

¿El encuentro no fue entre Einstein y los físicos de la escuela hacia los veinte para analizar las discrepancias entre la mecánica cuántica y la relatividad?

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moncton dijo:

Muy aconsejable para el que este interesado

Copenhagen (TV Movie 2002) - IMDb

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Copenhagen, Tuesday night( September 1941 added in Elisabeth's handwriting)

My dear Li! Here I am once again in the city which is so familiar to me and where a part of my heart has stayed stuck ever since that time fifteen years ago. When I heard the bells from the tower of city hall for the first time again, close to the window of my hotel room, it gripped me tight inside, and everything has stayed so much the same as if nothing out there in the world had changed. It is so strange when suddenly you encounter a piece of your own youth, just as if you were meeting yourself. I liked the trip coming over here too: In Berlin we had pouring rain, over Neustrelitz storm and rainshowers as if from buckets, in Rostock it cleared up, from Wenemünde on the sky was scrubbed clean, almost cloudless, but still a stiff north wind; so it remained until I arrived here. Late at night I walked under a clear and starry sky through the city, darkened, to Bohr.
Bohr and his family are doing fine; he himself has aged a little, his sons are all fully grown now. The conversation quickly turned to the human concerns and unhappy events of these times; about the human affairs the consensus is a given; in questions of politics I find it difficult that even a great man like Bohr can not separate out thinking, feeling, and hating entirely. But probably one ought not to separate these ever. Mrs. Bohr too was well, she asked me a lot about you and the children, especially about Maria. The pictures I will show to her tomorrow night, I have a nice enlarged foto of Maria which I had made for Mama. Later I was sitting for a long time with Bohr alone; it was after midnight when he accompanied me to the streetcar, together with Hans. (Bohr)
Thursday night. I will take this letter with me to Germany after all and send it from there. From everything I have heard, the censorship would delay the arrival several days as well, so it makes no sense to me that a censor should read this letter. Unfortunately, you then have to wait for my letter for almost eight days. I for my part have not received any mail here either.- Yesterday I was again with Bohr for the whole evening; aside from Mrs. Bohr and the children, there was a young English woman, taken in by the Bohrs, because she can not return to England. It is somewhat weird to talk with an English woman these days. During the unavoidable political conversations, where it naturally and automatically became my assigned part to defend our system, she retired, and I thought that was actually quite nice of her.- This morning I was at the pier with Weizsäcker, you know, there along the harbor, where the "Langelinie" is. Now there are German war ships anchored there, torpedo boats, auxiliary cruisers and the like. It was the first warm day, the harbor and the sky above it tinted in a very bright, light blue. At the first light buoy near the end of the pier we stayed for a long time looking at life in the harbor. Two large freighters departed in the direction of Helsinor; a coal ship arrived, probably from Germany, two sailboats, about the size of the one we used to sail here in the past, were leaving the harbor, apparently on an afternoon excursion. At the pavilion on the Langelinie we ate a meal, all around us there were essentially only happy, cheerful people, at least it appeared that way to us. In general, people do look so happy here. At night in the streets one sees all these radiantly happy young couples, apparently going out for a night of dancing, not thinking of anything else. It is difficult to imagine anything more different than the street life over here and in Leipzig.- In Bohr's institute we had some scientific discussions, the Copenhagen group, however, doesn't know much more than we do either. Tomorrow the talks in the German scientific institute are beginning; the first official talk is mine, tomorrow night. Sadly the members of Bohr's institute will not attend for political reasons. It is amazing, given that the Danes are living totally unrestricted, and are living exceptionally well, how much hatred or antiestéticar has been galvanized here, so that even a rapprochement in the cultural arena - where it used to be automatic in earlier times - has become almost impossible. In Bohr's institute I gave a short talk in Danish, of course this was just like in the olden days ( the people from the German Scientific Institute had explicitly approved) but nobody wants to go to the German Institute on principle, because during and after its founding a number of brisk militarist speeches on the New Order in Europe were given. - With Kienle and Biermann I have spoken briefly, they were, however, for the most part busy with the observatory.

Saturday night. Now there is only this one night left in Copenhagen. How will the world have changed, I wonder, when I come back here. That everything in the meantime will continue just the same, that the bells in the tower of city hall will toll every hour and play the little melody at noon and midnight, is so weird to me. Yet the people, when I return, will be older, the fate of each one will have changed, and I do not know how I myself will fare. Last night I gave my talk, made a nice acquaintance too. The architect Merck who had built the Reich Sports Arena in Berlin is slated to build a new German school here in Copenhagen, and he came to my talk. On a joint trip aboard the streetcar we had a pretty good time conversing. I always enjoy people who are especially good at something.- Today at noon there was a big reception at the German embassy, with the meal being by far the best part of it. The ambassador was talking animatedly in English to the lady seated next to him, the American ambassador. When she left, I believe I heard her say to somebody: We will meet again, definitely at Christmas, unless something quite unexpected comes up. One has to take these diplomatic dinners in a humorous vein.
Today I was once more, with Weizsäcker, at Bohr's In many ways this was especially nice, the conversation revolved for a large part of the evening around purely human concerns, Bohr was reading aloud, I played a Mozart Sonata (a-Major). On the way home the night sky was again starstudded. - By the Way: two nights ago a wonderful northern light was visible, the whole sky was covered with green, rapidly changing veils.
It is now a quarter of one a.m. and I am rather tired. Tomorrow I will post this letter in Berlin, so you will receive it Monday most likely. In one week I will be with you again and tell you everything that happened to me. And then we all will be together for the winter in Leipzig.
Good night for now! Your Werner

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Spiegel: profesor Heisenberg, ¿cree que su papel en el proyecto atómico alemán - como el principal teórico que, por así decirlo, ha señalado el camino matemático para la energía atómica para los alemanes - se retrata con precisión en la serie Spiegel por el historiador británico David Irving?

Heisenberg: Permítanme comenzar diciendo que nunca tuve autoridad completa para la organización - como por ejemplo Oppenheimer tenía en los Estados Unidos. Yo era, como otros, que se supone para trabajar en los fundamentos teóricos - aunque sólo sea para saber qué posibilidades del otro lado, los Estados Unidos, tenía - y asesorar a aquellas personas que hicieron los experimentos. Además, yo era jefe de la Kaiser-Wilhelm-Institut de Berlín-Dahlem, a partir de 1942. Pero no lo hice, por ejemplo, tienen que tomar decisiones relativas a cualquier experimentos realizados fuera de mi instituto.

Spiegel: Probablemente esto se hizo evidente en el experimento de 1940 del profesor Bothe en Heidelberg. Bothe era aclarar en un experimento si pura de carbono - grafito - sería conveniente como un moderador en un reactor nuclear, y en esta medición se ha producido un error. En opinión de Irving de que este error se convirtió en un obstáculo importante en el proyecto de la bomba atómica alemana.

Heisenberg: En el terreno teórico, que supuso que un reactor nuclear podría ser construido. La medición de Bothe parecía indicar que no podía. Sin embargo, no tuvimos ningún motivo para dudar de la validez de la medición de Bothe, ya que la teoría proporciona sólo una estimación y no un cálculo exacto, porque el estado de la teoría del núcleo atómico en ese momento aún no habría hecho esto posible.

Spiegel: ¿Acaso resultado erróneo de Bothe decidir la carrera por la bomba atómica como supone Irving?

Heisenberg: Nunca hubo una carrera por la bomba atómica; en cambio, hubo, por parte alemana, también, los esfuerzos para construir reactores nucleares. Naturalmente, la medición de Bothe influyó eso, pero tampoco debemos exagerar esta influencia. Es cierto: Si hubiéramos sabido que también se puede hacer con el grafito, podríamos haber salvado a nosotros mismos todos los esfuerzos con respecto al agua pesada como moderador. Por otro lado: Sabíamos que se podía hacer con el agua pesada. Y, la producción de agua pesada, técnicamente no era demasiado difícil.

Spiegel: ¿Hubiera sido más sencillo en Alemania con el grafito?

Heisenberg: La industria habría tenido que producir grandes cantidades de grafito muy puro en vez de agua pesada. Técnicamente que habría sido más sencillo, sin duda más barato y más rápido también.

Spiegel: Si los físicos alemanes habían utilizado grafito en lugar de agua pesada, ¿tendrían, durante la guerra, se logró una reacción en cadena en un reactor, el requisito previo para la construcción de una bomba atómica?

Heisenberg: Probablemente, pero en el panorama general de la evolución de la energía atómica sería aún han cambiado muy poco. Vamos a suponer que teníamos en 1943-1944 - nada anteriormente era muy poco probable - logró terminar un reactor crítico. Entonces, cada agencia a cargo de armamento que quería contemplar bombas atómicas habría tenido que argumentar: Si ahora se quiere producir plutonio esta manera, habrá que aumentar los gastos, al menos por un factor de cien, a invertir una gran cantidad de mano de obra, se lo quite de otras producciones de armas, y así sucesivamente. Y eso era realmente imposible en la situación de guerra entonces.

Spiegel: Irving afirma que los físicos alemanes hasta 1942 fueron por delante o por lo menos aún con la investigación atómica estadounidense.

Heisenberg: Eso no es del todo correcto. En Alemania ya sabíamos lo que los estadounidenses también sabían, a saber, que y cómo la energía atómica, en principio, se puede usar y técnicamente aplica. Por lo tanto, yo diría: Algo igual en el conocimiento, no es igual en lo que ya en ese momento había comenzado, o se había preparado en términos de organización en los EE.UU..

Spiegel: ¿cuántos se necesitan kilogramos de uranio 235 para construir una bomba atómica físicos alemanes sabían de sus cálculos - y estas cifras, que apareció después de la guerra, de acuerdo con los del lado americano?

Heisenberg: La mayoría de los números de este tipo, no sólo con respecto al tamaño de la bomba atómica acordó casi completamente, excepto para la medición de carbono antes mencionado. En ambos lados de la física, por supuesto, tiene el mismo aspecto, y en ambos lados de trabajo se hace correctamente. Esto es por qué entonces - más o menos durante el otoño de 1941 -no llegó este descubrimiento sorprendente de los físicos, probablemente, también en el lado americano: es realmente posible, uno puede construir bombas atómicas. Pero al mismo tiempo que el choque se produjo para nosotros también el reconocimiento: es posible - pero sólo con un esfuerzo técnico tremenda, y que, gracias a Dios, no podemos en absoluto permitirse en Alemania. Mirando el tremendo esfuerzo, habíamos esperado que los estadounidenses también podría optar por no, ya que probablemente ganar la guerra más rápido sin una bomba atómica.

Spiegel: ¿Quieres decir, si estos recursos utilizados para la bomba atómica en vez habían sido invertidos en otras armas de guerra?

Heisenberg: Toda la razón - que resultó ser cierto, y no se puede enfatizar suficientemente este punto - americanos utilizaron una parte bastante significativa de sus recursos totales de armamento en estos trabajos atómicos. Si en lugar de haber invertido todo en, digamos, aviones y tanques, entonces Alemania probablemente habría perdido la guerra incluso antes. ¿Qué hubiera pasado en la guerra de Estados Unidos contra Japón, no puedo presumir de juzgar.

Spiegel: ¿Cómo es que el en 1939 bastante fuerte interés inicial por el Ministerio de la artillería en Berlín tomó un giro tan tarde? ¿No es asombroso cómo el Ministerio de Artillería recogió apresuradamente los físicos atómicos alemanes en 1939?

Heisenberg: El interés de los organismos oficiales alemanes desde el principio era bastante desigual. Cuando, en 1938, Hahn y Strassmann en Alemania descubrieron la fisión del uranio, el mundo entero informó extensamente con enormes grandes titulares. Físicos estadounidenses, me han dicho, que estaban reunidos en una conferencia y se les informó sobre el descubrimiento de Hahn, de inmediato se sentó con sus instrumentos y día medido y noche y luego, todavía en la conferencia, confirmó: Hahn es correcto. La fisión del uranio fue considerado en los periódicos un descubrimiento del más alto rango. Pero en Alemania nadie se enteró de ello, excepto los físicos.

Spiegel: El éxito de Hahn fue esencialmente silenciada.

Heisenberg: En Alemania, todos los periódicos estaban durmiendo oficialmente, y probablemente tenía que dormir, esencialmente sólo los especialistas sabían sobre este asunto. Y luego, en el verano de 1939 el Dr. Siegfried Flügge, asistente de Otto Hahn en el momento, escribió en la revista "Die Ciencia Natural", un documento en el que se refirió a la reacción en cadena y la posibilidad de las materias de la potencia explosiva máxima. Fue este documento que suscitó un considerable entusiasmo. El Ministerio de la artillería podría haber argumentado: Si en Estados Unidos informan sobre este tema con tanto énfasis, entonces es obvio que no es completamente irracional y tenemos que ver en esto.

Spiegel: A pesar de esto, el proyecto no fue iniciado en una gran forma. Irving ve la razón de esto, al menos en parte, en que no está siendo informado el liderazgo alemán, o ser informado de forma incompleta.

Heisenberg: yo no creo que uno puede describir de esa manera.

Spiegel: Irving informa que Hitler fue informado oficialmente sobre el proyecto atómico sólo una vez, es decir, por el Ministro de armamentos, Speer, después de que usted y otros físicos hubieras presentado una charla a los armamentos personas en 1942. El Sr. Speer confirmó esto a nosotros en estos días .

Heisenberg: Yo diría que en esta reunión se ha mencionado con frecuencia en la Casa Harnack en junio de 1942, los líderes de más alto rango en la industria de armamento fueron informados totalmente correcta acerca de todo. Nosotros les dijimos que principalmente vimos un camino hacia una bomba atómica, pero también de inmediato agregamos que esta evolución sin duda tomar varios años. Por cierto, si no recuerdo mal, en el momento en que nos pidieron por el Mariscal de Campo General, Milch, el tiempo que en nuestra opinión se necesitarían los estadounidenses para terminar un reactor nuclear y una bomba atómica. Nuestra estimación rigurosa era: Incluso si los estadounidenses trabajaron en esto con pleno esfuerzo, que no acabarían su reactor antes de finales de 1942 - que era la mitad de un año en el camino a continuación - y una bomba atómica muy probablemente no antes de finales de 1944 . En realidad, creíamos que tomaría mucho más tiempo.

Spiegel: Su pronóstico, al menos en relación con el reactor nuclear, era correcta.

Heisenberg: Sólo hay un punto que Irving no ver a la derecha: El liderazgo alemán era - contrariamente a la opinión de Irving - en el verano de 1942 bastante lógico y consistente en no ordenar un intento de producir bombas atómicas. Irving afirma: Los alemanes sabían que podían construir reactores que utilizan agua pesada, que un reactor de este tipo generaría plutonio a partir del cual se podría construir bombas. Pero luego continúa: Parece extraño que después de la reunión en 1942 - donde todo esto se había presentado al armamento superior Liderazgo no pasó nada, no se solicitaron recursos financieros y el gobierno no ordenó un programa. Pero en realidad esto era bastante comprensible porque entonces la situación de guerra se destacó a un nivel tal que no quedó aliento para tales desarrollos a largo plazo.

Spiegel: Y sin embargo, los proyectos de V1 y V2 se sacó adelante.

Heisenberg: Supuestamente hubo una orden del Führer - que yo mismo nunca he visto por escrito, sin embargo, - según la cual todos los acontecimientos que no condujeran a aplicaciones militares dentro de medio año en realidad estaban prohibidos. Es cierto que la V1 y V2 tomaron más tiempo también, pero la gente de Peenemnde podría decirle al liderazgo: En uno o dos años vamos a estar ahí. Pero nosotros, los físicos sabíamos con certeza y podríamos afirmar con la conciencia tranquila: en menos de tres o cuatro años nada se podía hacer. Y que teníamos razón en ese sentido y que el liderazgo alemán evaluado correctamente la situación en este caso fue confirmado: A pesar de que los estadounidenses tenían un potencial mucho mayor en científicos, ingenieros y materiales, ni un solo ataque aéreo, y una industria que podría trabajar 24 horas al día en condiciones totales de luz - a pesar de todas estas posibilidades los estadounidenses no terminaron la bomba antes del final de la guerra con Alemania.

Spiegel: Parece claro que la investigación atómica alemana después de la reunión en la Casa Harnack se arrastraba.

Heisenberg: Era como flotando en el agua. Irving lo describe muy acertadamente. Pero permítanme quizás agregar aquí un comentario crítico a su informe de otra manera muy fiable: Irving es un historiador que se esforzó en estudiar las fuentes, documentos y fotografías, para entrevistar a las personas que aún viven - y él ha hecho esto con mucho cuidado. Dondequiera que se refiere a los hechos, Irving puede, basado en su investigación a fondo, el informe de forma fiable y precisa. Es diferente con el aspecto psicológico: cuando se trata de los motivos, Irving se mete en dificultades. Tendría que poseer un conocimiento profundo de la situación psicológica en un Estado totalitario participado en la guerra - y esto no puede tener y ni siquiera puede adquirir después de los hechos, decir a través de las conversaciones. Y ahí no acababa de evitar el peligro de llenar el vacío resultante con los estereotipos. Un estereotipo favorito que probablemente influirá en las opiniones por algún tiempo en el futuro es la "carrera por la bomba atómica" muy ...

Spiegel: ... entre Estados Unidos y Alemania.

Heisenberg: Irving está presuponiendo inconscientemente este escenario como un hecho . Pero eso no es lo que realmente era. Ciertamente, había gente en Alemania que se preguntaban: ¿No es posible, después de todo, para construir algo como una bomba atómica. Obviamente, el liderazgo alemán también tenía que pensar en esas posibilidades. Pero nunca hubo un verdadero esfuerzo, ordenó desde arriba y financiado, en el que, como en cualquier proyecto de armas, miles de personas han participado - que nunca existió.

Spiegel: Irving cita una serie de hechos que, en su opinión, actuaron como un freno para el desarrollo, entre ellos, por poner algunos ejemplos, las reservas del liderazgo NS hacia la investigación en las ciencias naturales ...

Heisenberg: Jugó un papel, por supuesto. Existía por adelantado una desconfianza enorme entre la dirección socialista nacional en un lado y los físicos atómicos, por el otro que iban en ambos sentidos.

Spiegel: Probablemente el problema con la raza también ...

Heisenberg: ... sin duda jugó un papel .

Spiegel: Usted se suponía que no debía creer en Einstein, pero hacía uso de él.

Heisenberg: Sí, todas estas tonterías. Pero el punto decisivo fue que en el verano de 1942 una decisión diferente se hizo en Alemania que en los Estados Unidos. La decisión en Estados Unidos, dijo: ahora sabemos que las bombas atómicas se pueden construir, por lo tanto superior esfuerzo hacia esta meta. En Alemania, en cambio, fue: esto va más allá del potencial industrial alemán de todos modos, y la guerra acabará muy probablemente más antes de que tales armas jugarían un papel - por lo tanto no vamos a hacerlo en absoluto.

Spiegel: Bajo un sistema diferente, sería simple curiosidad no haber tentado a darse cuenta de tal proyecto, similar a lo que Oppenheimer dijo una vez, que todas las cosas 'técnicamente' dulces deben ser tentador para un físico?

Heisenberg: No hace falta decir que todo físico está bajo esta tentación. La pregunta es siempre lo que los otros componentes de la conciencia de uno, por así decirlo, contribuyen. Una vez escribí en una carta al Sr. Bethe, quien conocía bien, que nunca iba a apoyar la tesis adelanta en algunos periódicos o en el libro de Robert Jungk que los físicos alemanes habían sido jovenlandesalmente superiores a los estadounidenses. Me gustaría mantener siempre que la situación en la que estábamos era muy diferente de la de nuestros colegas estadounidenses, y que cualquier persona racional en nuestra situación tenido que reaccionar como lo hicimos. Nunca se puede adivinar a ti mismo lo que habría hecho, si ... La única cosa que puedo decir es lo que está haciendo en una situación particular en la que usted tiene que tomar una decisión.

Spiegel: Mediante el libro de Robert Jungk, sobre todo, la impresión pública de que se había creado una decisión jovenlandesal había conducir en última instancia a, digamos, un "ir lento" de los físicos alemanes. Ahora parece, sin embargo, como si nunca se había enfrentado a una decisión de este tipo.

Heisenberg: En estas zonas no hay nunca verdades al ciento por ciento, todo es tan inmensamente complicado y entremezclado. Sin lugar a dudas, era conveniente para nosotros que después de un examen cuidadoso de todos los factores, honestamente, podríamos decir que en el tiempo disponible durante la guerra que no podíamos construir bombas atómicas.

Spiegel: Por otro lado, existe su visita con Niels Bohr ...

Heisenberg: .. que no encaja exactamente con esto.

Spiegel: Si usted permite que recordemos, en octubre de 1941 que visitó el físico danés y premio Nobel Niels Bohr en Copenhague y dio a entender a la sugerencia de que los físicos alemanes y estadounidenses podrían secretamente llegado a un acuerdo de no construir la bomba. ¿No era que un intento de instigar una decisión jovenlandesal?

Heisenberg: La historia de esta era que en Alemania de repente vimos un camino a una bomba atómica que, al menos en principio, era técnicamente factible y esta situación en sí era bastante horrible para nosotros. Teníamos confianza ilimitada en Bohr como uno de los físicos atómicos principales; su consejo humano tenía que importa mucho para nosotros. Lamentablemente, sin embargo, en esta conversación que no estábamos muy capaz de comunicarse.

Spiegel: Después de la guerra, ¿Habló con Niels Bohr sobre esta visita una vez más?

Heisenberg: En el año 1947, un oficial británico que estaba a cargo de nosotros en Gotinga, me llevó a Copenhague, y que luego pasó toda una noche en la casa de campo de Niels Bohr en Tisvilde hablando de este evento. Ambos tuvimos la impresión de que esta charla, en 1941 había resultado bastante malograda. Bohr me dijo en 1947 que llegó a ser tan extremadamente sorprendido por mi afirmación de que ahora sabíamos que uno podría construir bombas atómicas. Bohr no estaba a la altura de este lado de la física a continuación y al parecer tenía sólo a través de mí en esa visita se enteró de que es posible fabricar bombas atómicas. Y esto lo había excitado hasta el punto de que ya no escuchó o comprendió lo demás que le estaba diciendo. Más tarde, en 1943, en Estados Unidos, Niels Bohr sólo informó: Los alemanes saben que uno puede hacer bombas atómicas ....

Spiegel: .. y con lo que terminó la aceleración del desarrollo en los EE.UU.?

Heisenberg: No. La decisión en Estados Unidos por aquel entonces hacía tiempo que había sido tomado.

Spiegel: Usted se enteró de las consecuencias de esta decisión, a todos los efectos prácticos, sólo en 1945, mientras que fueron internados en la granja Hall y escuchado un anuncio en la radio acerca de la explosión de la bomba atómica estadounidense sobre Hiroshima. ¿Cómo, en retrospectiva, usted evalúa el papel de los físicos atómicos en este evento?

Heisenberg: he aprendido que los descubrimientos científicos se prestan no sólo a lo positivo, sino también a consecuencias terribles. Tenemos que hacer esfuerzos para evitar este tipo de consecuencias en el futuro.

Spiegel: profesor Heisenberg, le damos gracias por esta conversación.

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Shanchito dijo:

¿El encuentro no fue entre Einstein y los físicos de la escuela hacia los veinte para analizar las discrepancias entre la mecánica cuántica y la relatividad?

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