The Manhattan Project

J. Robert Oppenheimer's Interview

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In this rare interview, J. Robert Oppenheimer talks about the organization of the Manhattan Project and some of the scientists that he helped to recruit during the earliest days of the project. Oppenheimer discusses some of the biggest challenges that scientists faced during the project, including developing a sound method for implosion and purifying plutonium, which he declares was the most difficult aspect of the project. He discusses the chronology of the project and his first conversation with General Leslie Groves. Oppenheimer recalls his daily routine at Los Alamos, including taking his son Peter to nursery school.
Date of Interview: 
1965
Location of the Interview: 
Unknown
Collections: 
Transcript: 

Stephane Groueff: I want to start from the beginning. My book, I intend to start with the year 1942 because otherwise, there is no limit. A few months before the Manhattan District and decision to go—

J. Robert Oppenheimer: The decision was actually made on December 6, to take the thing seriously.

Groueff: ’41?

Oppenheimer: Right.

Groueff: After Pearl Harbor?

Oppenheimer: Before Pearl Harbor.

Groueff: Before Pearl Harbor.

Oppenheimer: Well, of course, the initial discovery and its interpretation in early 1939 attracted everybody’s interest. I talked in just a friendly way about the critical assemblies and things like that. But I was not interested in fission. I had other professional interests. And I was not brought into it until perhaps September of ’41 and then by an indiscretion—an eminent English visitor started talking to Lawrence and me.

Groueff: You were a professor at Berkeley?

Oppenheimer: That is right. And clearly, his source of his confidence was the work of [Rudolf] Peierls in England. And he said it was terrible that [Enrico] Fermi and I were not involved in this.

Groueff: Who said that, the Englishman?

Oppenheimer: The Englishman. And this gave Lawrence the idea that I should go with him to the academy and committee, which was considering these problems. And in preparation for that, I began to look at it, some reasonable ideas about the possible range of critical masses, the use of the so-called tamper, probable assembly, and discuss them I think in a conservative but affirmative way at that meeting.

Groueff: That was a meeting where?

Oppenheimer: In Schenectady, actually.

Groueff: Schenectady.

Oppenheimer: Maybe in October. I do not have the date.

Groueff: So you came after this meeting with—?

Oppenheimer: After the discussion.

Groueff: After the discussion with Lawrence. Was that [Mark] Oliphant?

Oppenheimer: You will have to provide the name because I will not.

Groueff: Okay.

Oppenheimer: And after that, I got interested. Lawrence had this fantastic electromagnetic method that I went into some ways in increasing its effectiveness by a very large factor, which did work but it was just a question of how to design magnetic fields, really. And after Pearl Harbor, there was a meeting setting up the Metallurgical Laboratory and I attended that.

Groueff: That was in Chicago.

Oppenheimer: That was in Chicago, probably the second of January or the 26th of December—it was just after either Christmas or New Year. You can find that out. And during the spring, I did have a communication from [Gregory] Breit asking me if I would like to work with him. But for reasons which are known but not clearly to me, Compton felt that he should have at the Metallurgical Laboratory some group looking into the actual problems of the bomb and not the reactor. And I think he wanted Carl Anderson, a cosmic ray physicist from CalTech, to be in charge of that but Anderson refused. The Project was in bad order, it was thought that it was badly run, they would never get anywhere, and that there were more useful things to do for the war.

I went to Chicago and Compton asked me to take charge of it and the rest, I think, is recently recorded.

Groueff: So until you joined the Metallurgical Lab you were working sort of part-time—?

Oppenheimer: In fact, I was not officially working at all.

Groueff: You were helping.

Oppenheimer: I met with people and I did one useful, not very exciting, piece of work.

Groueff: You did not have a sort of definite task to finish like Lawrence had or Compton or the other people?

Oppenheimer: No. Although I realized that there was a job to do, I did not think it was mine or recognize that it was mine. But that changed in the spring of ’42 and I first found out what it was and saw that it was suffering—this is all history—from terrible lack of communication, misconceived ideas of secrecy, and from inadequate theoretical guidance.

Groueff: So even then since the beginning, you worked on the problems of critical mass and assembly?

Oppenheimer: Well, that started in the autumn of ’41.

Groueff: I see. Not so much in the separation.

Oppenheimer: No, except for some help to do the California project.

Groueff: I see.

Oppenheimer: And I would say that from the time that fission was discovered and we talked in a romantic way about what I call the Mojave Experiment—it turned out to be the wrong desert—to the time when we picked it up again in the autumn of 1941, I was thinking about a wholly different question. And after that, it is well recorded. I do not need to repeat.

Groueff: Do you remember the circumstances of your first meeting with Groves?

Oppenheimer: Yes.

Groueff: I think he said it was on the train.

Oppenheimer: No, the first meeting with Groves was at the house of the President of the University for California. It was called Sproul and we had lunch there, I think. And after lunch, I said, “This thing will never get on the rails unless there is a place where people can talk to each other and work together on the problems of the bomb. And this could be at Oak Ridge, it could be some California desert, but someplace, there has got to be a place where people are free to discuss what they know and what they do not know and to find out what they can.” And that made an impression on him.

The next time we met was in Chicago and he asked me to travel with him—probably Nichols.

Groueff: Marshall probably.

Oppenheimer: Marshall, yeah, on the 20th Century Limited. And I did for a certain distance and at that time, we agreed that we would try to set up a laboratory.

Groueff: But was it then that you were assigned with—?

Oppenheimer: I was assigned by Compton but it was a responsibility without any means of doing anything about it.

Groueff: But the decision that you should have the whole project of the assembling of the bomb and all this, the weapon side, was—?

Oppenheimer: That was probably somewhat later. My argument was not that I should head it but that it should exist.

Groueff: I see.

Oppenheimer: Groves would know this better but there was probably a long period of indecision about who the best person was to head it. I know that my friend Ed McMillan was considered, who was then probably not quite right for it. He is now the Director of the Lawrence Laboratory. I think that after a certain amount of uncertainty and vacillation, it was formally confirmed in the first days of 1943. But all this is a record, I just do not have it.

A letter was sent by Groves and Conant to me establishing the laboratory and me as its Director and it is published in—

Groueff: I saw this. But your selection, I think, was made probably between Compton on one side and Groves—?

Oppenheimer: Well, in the nature of things, I am not an expert on it.

Groueff: And so from there?

Oppenheimer: Well, in ’42 in the autumn, things were advanced enough so that we actually started looking for a place. And McMillan and I went off together with one of Groves’ officers and Groves joined us and he liked the Los Alamos site, which I showed him, and it was certainly better than the one the officer had found. Whether it was good or not, I do not know. So the work on the Los Alamos project started in the autumn of ’42 and I was involved in the design of laboratories, houses. All the houses had balconies and fireplaces.

Groueff: That was your big contribution [laughing]?

Oppenheimer: That was my big contribution [laughing]. And I think the actual confirmation of my responsibility may have come very early in ’43, I am not entirely sure, after an awful lot of discussion because all the time I was recruiting people, and all the time I was discovering the idea of going into uniform was completely unwelcome. The letter of Groves and Conant presented a kind of compromise, which in fact, never was carried out. It is always very hard to remember the things that were made difficult and took a long time to settle in retrospect are completely clear.

Groueff: Yes.

Oppenheimer: And we moved out there, my family and I, in mid-March of ’43 and moved up to the May signing of the first scientists.

Groueff: At that time, it existed a little bit—?

Oppenheimer: Well, we actually moved into one of the teacher’s houses that had been there in the old school. The new houses were not yet complete, the laboratory was not complete, but it was possible to establish a headquarters.

Groueff: And you knew that the area—you knew the boys’ school there before from your own childhood?

Oppenheimer: Well, no. Since ’21, I think, I had been going to New Mexico and since ’29, we had a ranch in the Sangre de Cristo, which we still have. It is about three thousand meters high. And it is fifty-five miles by a very rough and terrible trail from there to Los Alamos so we had ridden across it by horse. So I had been there but—

Groueff: And that helped in the selection of the site?

Oppenheimer: That made me know it existed, that about all. It was only that the other site, which was deep in the canyon, had in fact, even for our initial plans, inadequate room. It would have been completely impossible to do the things which we had to do, as it turned out. But also, my feeling was that if you are going to ask people to be essentially confined, you must not put them in the bottom of a canyon. You have to put them on the top of a mesa. I think that was even more important than the technical details.

Groueff: So it turned out to be the good site, the ideal site for the project.

Oppenheimer: Well, I cannot say that; it had many very bad disadvantages. But it was not a place where you felt locked out because you looked out over the whole valley.

Groueff: I visited.

Oppenheimer: And we did not have enough water; that was a perpetual problem. The problem of getting things was very much more terrible than it need have been because of security and because there actually was no transportation. So that I will not say it was the ideal site but it was good enough.

Groueff: It was more attractive than Oak Ridge or Hanford. Very beautiful place, I loved it there.

Oppenheimer: And I will quote Emilio Segre, whom you may have talked to, when he first came there in April of ’43. He stood by this building that is still there called Fuller Lodge, a sort of hotel. And that time, there was nothing in front of it and you looked out over the desert and to the Sangre de Cristo, which were covered with snow. It was extremely beautiful. And Segre said, “We are going to get to hate this view.” [Laughter]

Groueff: But actually, they enjoyed it and I understand later some of them were skiing and you were going on horseback.

Oppenheimer: Well, we had horses in the country and in June, Robert Wilson, my wife, and I went and got them. And my wife and I, we kept a horse and gave the others to others.

Groueff: And you kept them at Los Alamos?

Oppenheimer: Right. There was a rather bizarre notion that secrecy could be preserved by having some poor soldiers ride around the fence on horses. It did not do much good [laugh].

Groueff: But how did you form the nucleus of your team there, the very first men that you recruited? Did you travel personally?

Oppenheimer: Yes.

Groueff: From university to university?

Oppenheimer: I went in the first instance to those who were working on the problem, or on some fringe of the program. We had had a meeting at Berkeley during the summer of ’42 with six or seven quite good theoretical physicists. And most of them agreed with me that they needed a place to get to work. And one of them did not want to come but the other fellow did. There was a center at Stanford, there was a center in Minnesota, there was a center in Princeton, there was a center in Cornell, and a few others but I am not trying to be complete. And I went and visited and saw who would like to come and invited them.

Groueff: Without knowing where the site was?

Oppenheimer: No, at that time, the site was probably vague at first and less vague later. It was always the problem of how much one could say. Of course, I remember visiting Princeton to collect a group of people. And then I started talking to people through at the Radiation Laboratory and the people working on proximity fuses and other projects with some guidance as to who might be spared. And [I spoke to] some people from the Metallurgical Laboratory in Chicago, some people from the radiation laboratory in Berkeley. So it was not trivial to persuade people that this was real but it was not entirely crazy to know where to go to start, you see.

Groueff: You started then from people who had some connection with the Project like Chicago?

Oppenheimer: Right, although I went very soon to the MIT Radiation Laboratory, the Radar Center, to get some really good scientists like Breit and [Luis] Alvarez and [Kenneth] Bainbridge.

Groueff: That is another fantastic thing. It seems to me that in wartime with so many important top-priority projects, one should think that all those scientists, or at least good ones, the top ones will be so much in demand that when you start a new project, to be able to assemble—

Oppenheimer: Well, remember, this was ’43 and the crisis of radar and proximity fuses was over.

Groueff: I see. And also, Chicago group—

Oppenheimer: There was quite a lot that was interesting in this so that people wanted to do it if they could. Some, not all.

Groueff: But you built it so it was not built at once but little by little.

Oppenheimer: No, I think our population doubled every four months.

Groueff: Doubled?

Oppenheimer: So since we were there a couple of years, it was a rather rapid growth.

Groueff: Could you give me a few names of the very first people who came with you to Los Alamos?

Oppenheimer: Yes. John Manley, Robert Wilson, John Williams, [Joseph] Kennedy, [Hans] Bethe very early, [Robert] Serber, [Emil John] Konopinski. I could go on.

Groueff: So you started with them and each one of them had more suggestion for recruitment?

Oppenheimer: Well, the recruitment was in the first instance for more or less my worry. Robert Wilson was there very early and brought [Richard] Dick Feynman, for instance. He was brilliant.

Groueff: Yeah, he is very colorful and gave me a lot of very colorful stories about Pasadena.

Oppenheimer: Well, he was at that time in Princeton.

Groueff: He must have been a kid.

Oppenheimer: He was.

Groueff: When I saw him now, he looks like a young man—very handsome, movie actor type.

Oppenheimer: Yes. Well, he was not so young and handsome then but he was—well, all this is well recorded and there is no point in wasting time.

Groueff: What I want to emphasize in this book is the difficulties and the obstacles in technical or scientific or technological areas and how were they overcome. Now of course, in your part of the work, some of the details are classified.

Oppenheimer: Yeah, I do not know what is classified. This makes it difficult for me.

Groueff: I mean the specification, of course, would be appreciated. I do not intend to do anything and to write anything technical but I would like to find examples that I can give as extraordinary difficult tasks or something which bordered the impossible, which at the first sight, seemed impossible—let’s say like in gas diffusion, to find this kind of barrier or a seal or pump was so difficult that there are moments when probably the whole project, or this part, would fail. For instance, I found examples about the coating of the slugs, which was a fantastic technological part. Or for instance, the nickel plating of the diffusers and things like that. Now, which were in Los Alamos?

Oppenheimer: Have you read the technical history of Los Alamos?

Groueff: The history?

Oppenheimer: Technical history.

Groueff: Is that the one in two volumes by—?

Oppenheimer: Hawkins.

Groueff: Hawkins, yes.

Oppenheimer: That is a good place to find this out.

Groueff: Yes that is enough for my purposes but I would like to hear your opinion if I have to single out, let’s say, three, four, five problems, like say the problems of the new metallurgy of known metals or the tamper problem or the initiator or implosion?

Oppenheimer: Well, I think the set of problems connected with implosion was the most difficult and it required very new experimental techniques. And it was not a branch of physics which anyone was very familiar with.

Groueff: It did not exist before then?

Oppenheimer: No, no. And this was, both from a theoretical, from an observational, and from a practical point of view, quite an adventure and it was still a very reasonable opinion that one of the many things that were needed to make it work was not completely in order on July 16. The doubts which then existed were not of a metaphysical quality [laugh]. I think that was the main thing; we had always had this in mind as a possibly more effective and more sensible way to assemble a bomb. But as you undoubtedly know, we were forced to it in the case of plutonium.

Groueff: The gun method you could not use.

Oppenheimer: It is a very stumpfsinnig [dull] method anyway. And I think that at the time, when the laboratory had a sense of agonia was when we knew we had to do this and did not know whether we could. And the initial hopes we had, we never were able to prove out in a way which was convincing observationally and therefore retreated to a method which we could prove out and which worked but which was not the ideal one. But now we get very close to things of which I am sure the Russians know everything but I am not sure I am supposed to tell you.

Groueff: Was the principle of implosion known before in Europe?

Oppenheimer: No.

Groueff: What was the contribution for that of [Seth] Neddermeyer, a young scientist?

Oppenheimer: Well he did suggest it. He had been working on explosives, but he missed two of the essential points. The first is that under conditions of a good implosion, one would not be dealing with the assembly of solids but with fluid dynamics. And the second was that one would not be dealing with the materials of constant density but materials which could be compressed. Neither of these were in Neddermeyer’s mind. He just said, “Why, if you want to get things together quickly, don’t you send them in from all sides at once?”

Groueff: So the general idea?

Oppenheimer: The general idea and I would think in developing the point [John] Von Neumann played a quite decisive part because he had worked on the shaped charge problems.

Groueff: He did not work on the implosion.

Oppenheimer: Yes, sure, he did.

Groueff: But not in the whole project.

Oppenheimer: He was not responsible; he was a consultant but he certainly had very useful ideas.

Groueff: So you had people who worked on the explosives or the tamper part of it or the initiator or the decompression?

Oppenheimer: Well we had people, first of all, who tried to get the nuclear physics straight because this was not known.

Groueff: The theoretical department?

Oppenheimer: No, no, the experimental department. When we went to Los Alamos, it was not known how many neutrons were emitted when nuclear had fission with fast neutrons. And of course, without knowing that, you did not know if it would work or not. It was not known whether there were any time delays and if so, how long they were. Without that you could not have an explosive. So our first experiments were directed towards these fundamental questions of feasibility.

Groueff: From a number of questions as far as neutrons go, were they developed in laboratories only about slow neutrons?

Oppenheimer: Right, and very incompletely because no one had studied the problem of time delay.

Groueff: Chicago people did not work on fast neutrons?

Oppenheimer: Well, they never asked that question. Then there was, of course, a large and in the end, unavailing effort to purify plutonium so it could be slowly assembled. And a whole division of the laboratory worked on that and then found out that it was not relevant, unusable, and started working on other things.

Groueff: So it is correct if I assume and what I want to point out in the chapters about Los Alamos was entirely new scientists had to be—

Oppenheimer:  The technologists.

Groueff: or technologists but also even some fundamental—

Oppenheimer: Experiments. Yes, plutonium turned out not to be a cozy metal and one could actually take advantage of its peculiar properties and we did. But they were very hard to get straight in adequate amounts.

For a year, Chicago and Los Alamos got different densities from plutonium. Since the densities closely connected to the critical size, this was not trivial.

Groueff: I talked to some of your—

Oppenheimer: Have you talked to Cyril Smith?

Groueff: I was given his name and I intend to talk to him.

Oppenheimer: Oh, he would be very good.

Groueff: I talked to one of his men, [Robert] Bacher, and generally, people from lab. I saw [Raemer] Schreiber and [John] Manley and [Charles] Critchfield—each one gave me a piece. But from all those pieces, I think that what impressed me very much is being fantastically difficult or new without precedent, were the problems of implosion, which involves several things.

Oppenheimer: Well, and of course, the determination of critical mass, which we started when we had only a few hundred grams of uranium-235 and in which we had to become expert because it was serious. The detailed experimental study of the dynamics of implosions—this was very hard. And the initiator was nontrivial just because it had to be quiet—and really quiet—and then suddenly burst. This was nontrivial and the implosion was technologically nontrivial just on the small scale to make a thing, which was non-neutron emitting to a very high degree and then suddenly made the necessary burst. There are better initiators now but this caused people a lot of trouble.

And plutonium was a terrible test from beginning to end and never stayed quiet: it gets hot, it is radioactive, you cannot touch it, you have to coat it, and the coating always peels. It is just a terrible substance and it is one reason why—

Groueff: And the length changes with different temperatures.

Oppenheimer: Yes, and different impurities. So it has never been used for peaceful atomic power because you cannot buy anyone to pay any attention to it [laugh]. And we had to do it for other reasons.

Groueff: So plutonium is much more difficult than uranium 235?

Oppenheimer:  Oh yes.

Groueff: Which also was unknown.

Oppenheimer:  Yes, but which is, from a chemical point of view, so like uranium-238. The radioactivity is very minor. It does not warm up, it does not have many different allotropic forms. It is perfect permeable—you can look it up in a book. Plutonium we could not look at it the same way. And problems understanding the process of the explosion in order to get some rough idea of how big to make the bomb were very difficult theoretical problems and not really solved because we did not know how big the explosion would be.

And of understanding the partition of energy in different media after the bomb had detonated—these were all novel problems, not fundamental. There was not a single fundamental problem involved but all novel, technological problems involving quite unusual equipment because we were working with microseconds for the implosion and nanoseconds for the explosion.

Groueff: What is a microsecond?

Oppenheimer: Ten to the minus nine. And there was no electronic equipment to do that. We had to invent it.

Groueff: That is a fantastic aspect to the project; everything went on single-handedly from the theoretical, experimental, and even that mathematical prediction.

Oppenheimer: Technological, yes.

Groueff: So in other words, your people working on plutonium characteristics could not have a sample to work with.

Oppenheimer: Not for a long time.

Groueff: They had to wait.

Oppenheimer: Well, they turned out to be a remarkable lot with very little [to work with].

Groueff: Sometimes by luck, I understand, or even sometimes with the wrong assumption, I was given some examples about the chemists doing the right job on the wrong assumption—I think it was about chemistry of plutonium, assuming for certain things that plutonium would behave like uranium. And the whole thing worked, but for different reasons.

Oppenheimer: Right. I think this may be a Chicago invention because we came a little later.

Groueff: The [Glenn] Seaborg group.

Oppenheimer: You must remember that all the time we were monitoring radiation, measuring spontaneous fission, trying to find out the nature of the territory we were in, and also exploring radical things, many of which would never have worked, some of which have worked since but which were beyond our assured means at the time. So for a long time, Los Alamos continued essentially doing the things which we had decided were too dangerous, too unsure to do during war. Not all of them worked but most of them did.

Groueff: These are fantastic examples.

Oppenheimer: Well there were a lot of very bright people.

Groueff: I’m going back in to see Dr. Bacher, he was one of the important ones, one of the top people.

Oppenheimer: And so was Cyril Smith.

Groueff: Smith, yeah, he is at MIT.

Oppenheimer: Now the chemist, Kennedy, died.

Groueff: He was a very young man, no?

Oppenheimer: He was a very young man, a six-foot-three Texan. But a man who was very close to him was Arthur Wahl, who was at Washington University. Who was at Brookhaven and who had a lot to do with the initiator and many other things.

Groueff: Dodson.

Oppenheimer: Dodson. He is head of the Chemistry Division at Brookhaven. I think [Bruno] Rossi played a very large part. And in fact, the group leaders are all listed and it is worth to talking to all of them if they are still available. Some of them are English and that might be a little more complicated.

Groueff: I intend to see Bethe and Cyril Smith and Bainbridge.

Oppenheimer: Bacher?

Groueff: Bacher, I saw him in Pasadena. Feynman I saw—he gave me very interesting things.

Oppenheimer: So there is no point in my giving you these lists because they are published. But actually, every group—and they vary from time to time in what they were doing—had something important to do and any one of them is worth talking to. The man who did the circuitry for these very short-time scales is Willy Higinbotham, who was at Brookhaven. Now by today’s standards it is not much but it was a lot then.

Groueff: Right. And each group had a story, which is worthwhile?

Oppenheimer: Most groups, I would say. They were loosely organized in divisions and the divisions represented in the governing body. And I would not like to tell you who had the hardest problem.

Groueff: But how much didn’t you know about the other projects? You and your main group leaders, did you know about Hanford or about Oak Ridge?

Oppenheimer: Well, I had to know how it was going because I had to know about the flow of material. I happen to know pretty much about Hanford and essentially everything about the electromagnetic method. I learned more or less by accident about the thermal diffusion method and asked Groves to look into it. And I actually do not, to this day, know how to make a barrier. I do not care. But I had to know the scheduling.

Groueff: But you did not go to Oak Ridge?

Oppenheimer: I went to Oak Ridge. I went more than once to Berkeley. I went to Washington. I think I never went to Hanford, it was not necessary, but I went to Chicago quite often, which was the headquarters.

Groueff: So this compartmentalization they talk about—

Oppenheimer: Was not relevant in my case.

Groueff: Yes, for most of the top people, it did not apply.

Oppenheimer: Well, I am sure there are things I did not know about counterintelligence operations.

Groueff: The military side.

Oppenheimer: Well, about the truly military side, we had to know. But about the military intelligence side, we did not know too much. About the barrier problems, it would have been easy to find out but it never bothered me because I understood that finally it was coming out all right, that is really all I needed to know. But I needed to know production schedules and I needed to know them in great detail because we could not schedule the work at the laboratory in any other way. A few milligrams of uranium-233, a few grams of plutonium made all the difference in the world to us, and we could not make them.

Groueff: How long did you continue to believe that the Germans were working on the same thing? Was it until D-Day that all of you—

Oppenheimer: Well, it is different from person to person. I think probably [Eugene] Wigner believed it until there were no Germans left. I was never quite as frantic about this. I think I understood a deep destruction the National Socialist business had made in the German scientific scene. I was more worried about the campaign in Africa and the campaign in Russia when I went to New Mexico than I was about the Germans making a bomb. I thought they might very well be winning the war.

Groueff: By conventional weapons.

Oppenheimer: If you called it conventional.

Groueff: But you assume that they were at least working on it?

Oppenheimer: Yes. In fact, we talked at length with [Niels] Bohr to see what he knew about it. But what he knew was very reassuring.

Groueff: So Bohr knew more, right, that they were behind.

Oppenheimer: They were not doing this. They were doing something else and we wondered if they saw some way with slow neutrons to make something. But you cannot, of course, and we just worked on it long enough to reassure ourselves.

Groueff: Now one question that I can get from other people is what would be a typical working day for you at Los Alamos? That is one where did you live?

Oppenheimer: We lived about a third of a mile from the laboratory. I would try to get to the laboratory on normal days about eight or something like that and take our son, who was around, to the nursery school on the way.

Groueff: You would walk them to school?

Oppenheimer: We would just walk there and I would usually break for a little while between twelve and one because there was nowhere to eat, no food. And I would come home and then get back and I worked until six. And perhaps two or three times a week or four times a week, I would go back in the evening.

Groueff: After dinner?

Oppenheimer: After dinner. And we often found it possible to go off on our horses Saturday or Sunday, usually not both days. And of course, not in the dead of winter. My wife did a little skiing. Once every two or three months, we would spend Saturday night in Santa Fe and feel somewhat more human. And then I went to Washington occasionally.

Groueff: Now what is your opinion now that there is twenty years’ difference? My opinion being that this is probably one of the greatest performances or achievements of this system.

Oppenheimer: Well, I am not the man to answer that question. I do not know what it took to produce the hundred thousand airplanes that Roosevelt asked for but it was certainly not trivial.

Groueff: But as far as a scientific or technological effort?

Oppenheimer: Well, it was certainly sui generis—it was the first thing of just that kind.

Groueff: We do not in history have many examples of such intense and condensed in time.

Oppenheimer: No, it was certainly something novel.

Groueff: Enormous.

Oppenheimer: Novel.

Groueff: Novel. I would like to ask you several things but when I sit down and write, if I can ask you some [other things].

Oppenheimer: Of course.