Frayn. OK, well, I should make my remarks extremely brief. Just to say I very much look forward to reading, to seeing, the play about the Swedish academician who tried to keep Einstein under; it's an absolutely wonderful story, and absolutely right in the essence of drama.

The second thing is, Peter, talking about Henning Moritzen saying he still didn't understand why Heisenberg came to Copenhagen at the end of the play. Well, we had similar discussions with the cast in London when we did the play there. The actors, even at the end of rehearsals were saying, "Well, I still don't see why he came to Copenhagen." At that point they were also saying, as actors always do, at the end of a long rehearsal period, "Well, I don't think there's anything more we can do in the rehearsal room, we need to get in front of an audience now to find out about what's going on." And I said, "That is why."

And I do think that the idea of the human confrontation is absolutely of the essence, the whole of art, the whole of literature, the whole of storytelling, the whole possibility of language and communication. One can't communicate with oneself unless one communicates with others. Language is communicating with others. And I'd also be very interested to hear what people feel about Gell-Mann's criticisms of the Copenhagen interpretation and his view that quantum physics is the history of different narratives of the world; whether they feel that those narratives can ever be detached from a human being, or whether once again they're talking about the language of confrontation, of human beings and the world, human beings and each other.

Langdal. Actually, in your play, you invented the theatre. Because when I was in theatre school I read about this Greek person writing plays – much older than you are! (laughter) I think this idea to believe in the audience, not to underestimate the audience's mind, is one of your main achievements. Because theatre very often does that, I think. Having two persons, on stage, man and wife, when the third one comes in, everything happens. Then we have a drama. It's so simple. The thoughts in your play are so huge. Only three persons on stage dealing with that. You have very much courage, I think.

And we have a funny experience when we work with it. The first day of rehearsal, actors, as well as directors, are always very scared. "What am I going to say? I don't understand this shit. I don't understand. I try to understand it. Let's call in some physicists." And all that. OK, what can we do? Let's build up a copy of Niels Bohr's home.

And that's what we did. On stage we had three chairs in the corner, having asked my regissør [stage manager] to put on some cakes and coffee. In another corner we have a dining room. And then, I remember, we had a piano as well. We had that whole scenery filled up. And then, OK, let's get out there and try to read the play. And then for, I think, the first two weeks we walked around in this very normal house, and then after a while I took away all of the furniture, and it ended up like it is now. With three chairs. It's so simple. And I thought if we had continued one more month we wouldn't have had any chairs at all! (laughter) I don't know how long a time we should have been working to have no actors! (laughter) But actually the play is so beautiful, you don't need so much.

I always thought about this wonderful play you wrote, that it's not taking place on the stage; it's not taking place in the audience's mind; it's like the play is taking place somewhere in between. That's the impression I got myself when I watched it. It's not what they're doing on stage; it's not what is in my mind; but it's in between. That's what you wrote at the end of your play. I'm very excited about the way form and content fit together in your play. Yes. (laughter, applause)

I think of what you were saying about the difference between history telling and story telling: this is story telling. That's what we're in the theatre for. Story telling.

Aaserud. So what does the historian say about that?

Friedman. I'm sitting here like a sponge (laughter) soaking in all your words and impressions.

Let me just say that, many many moons ago, when I was actually young, back in the 1960s, and I was studying simultaneously physics, geophysics, and theatre and drama in New York, I had dreams that I, too, would be a great dramatist one day. At that time Harold Pinter was what I could have dreamed of aspiring towards. I remember sitting in a theatre in New York, watching these one-act plays of Pinter, and suddenly, at intermission, I hear next to me: "Harry, what did that mean?" "I dunno, but it's five bucks an hour parking, let's get the hell outta here." (laughter)

At that point I decided, well, I'll just become a historian of science. (laughter) When I thought of trying to use some sort of dramatic impulses to popularize, diffuse, "formidle," as we say, I considered film. And I pretty much, after that – Harry and the parking lot – turned my back on theatre, because if Pinter couldn't hold the New York audience, and I wasn't about to write the new "Hair" or any of the other musicals in the late '60s, I thought that film might be that opportunity. But your play revived my belief in theatre. Your play and your reactions give me confidence that we have to try breaking away from academic pedantry, and also to interpret the material, and, even more, play with it. I hope I'll be able to deliver the goods.

Frayn. I think everybody else should be saying their piece now. I should say just that the moral of this story is: never ever listen to what members of the audience are saying when you go out of the theatre. My producer said he was once coming out of a performance which had not gone terribly well – I think not one of my plays, I hope! And he heard a husband say to his wife as they came down the stairs afterwards: "Well, all we need now is to find the dog's been sick in the car!" (laughter)

Aaserud. Yes, I think that… (laughter) What do I think?

This has been mostly about what history can do for drama. But can drama do anything for history? I mean, is it anything in Frayn's play, for example, that contributes to the history, for the historian? Or what does drama do to a physicist, for example? That's just two starting questions. We don't limit our questioning to them, so maybe that should be the occasion to give the word to the audience. We should ask you to be free to ask whomever whatever: that is chaos but I think that's the best we can do. So is there anybody who has some reaction or question? Yes.

Predrag Cvitanovic. The question is for Peter. I'm a physicist This takes like 20, 30 years, and you feel stupid even after 30 years. It's a very long process, and in the process, lots of people get to be white-haired, and a guy like you doesn't have a chance. You can't become a physicist because you have to just be doing the same thing for at least 15–20 years. And it's wrong; it's hurting us. I don't know what the mechanism is, but it's very nice to have this described by a playwright. Actually we need people who just think of this immense training that we lug around. And this is my contribution, this is a provocative thought, I guess. Because you made the most perceptive remark of the whole day: you said when physicists go home they say, "We have a problem." It's really true. Nobody told me I do this, but this is actually very true. We're so happy when we have a problem; there's nothing worse in our life than things are working as they should be working. (laughter) I think it's very insightful in a way – you know I don't get it from [anybody else].

Langdal. I think I got it from Finn, actually!

Gordon Shepherd. I'm a neurobiologist. I think the most courageous thing you did was to bring real science across in dramatic form to a general audience. For those of us who write, who try to bring real science to a larger audience, it seems to me that's a wonderful thing you did. How did you decide on the right balance between what people would understand and what people wouldn't?

Frayn. Can you hear the question in the back, or shall I repeat it? How did I decide the right balance between what people could understand and what I could get into the play? Well, since I don't understand any science myself, if I could understand it I reckoned other people would understand it. So I just worked very hard to try and grasp at any rate some general points.

And I have to say I've made a lot of mistakes. Since the play opened in London, many scientists have seen it, and have very kindly written, saying, "I think you mean atom here," and so forth. And they've also pointed out two mathematical errors so ludicrous that even I could see once they were pointed out that the line didn't make any sense from the beginning to the end of the line. And they were lines I'd read over and over again. I also have to say they were read by the two physicists I asked to read the text of the play for me, and they hadn't noticed them either. So it is possible for things to creep in.

I only put so much science in because it seemed to me that you couldn't really tell the story without it. The story did actually involve the fine print of the consideration, it did involve the fine balance of trying to work out why Heisenberg had not done that equation, when it seemed with hindsight so obvious. You couldn't really make that work without explaining quite a lot.

Woman's voice. I'm a daughter of physicists. My father is Charles Misner who wrote Gravitation [with Thorne and Wheeler, 1973]. And I'm a story teller, a fiction writer myself. And I don't think they're very far apart. My father used to come home and have to explain to Margrethe every day. He came and told us children, well, why couldn't there be another universe, another galaxy. He was always interpreting his physics, and he writes poetry as well, and concludes some of his articles with poetry. I think many of the physicists I've met are very simple, very inclined to want to know more about the humanities because it helps them to communicate their interest in the universe. It is very much an interest in how it all began, how we all began, and I'm very grateful to Niels Bohr because he was the one who introduced my parents to each other. (laughter)

Frayn. I think it's absolutely true about story telling, that there is a parallel with history and with science. Story telling is often attacked by people who say that, well, story telling is a trivialization in literature, and real literature shouldn't be so concerned with telling the story. I don't think that's quite right.

First of all, story telling is a very old tradition. I think that probably human communication began with story telling, even before it got round to factual usages, and I think story telling is likely to go on until the human race ends.

But also, when you try and tell a story you do have to think about the connections between events. What a story is, is bringing out a series of connections between events. And when you organize a story – whether it's just an anecdote you're telling about what happened at the office that day, or whether it's a three volume novel – you do have to think of a possible series of connections between events. And it's very hard to do, it's very hard work. It seems to me to have a lot of parallels with what scientists are doing. They are actually trying to make a narrative, they're trying to see the connections between different phenomena, and make a story out of them. I don't know if that rings any bells.

Aaserud. Well, you brought up Gell-Mann's narratives, and in your play you have sort of several narratives, or three narratives, of this event that we don't know about. There's a parallel there, too, it seems to me in practical terms, and since none of the physicists want to answer your question I put that question back to you, if you see that as some kind of parallel.

Frayn. Yes, well, I'd very much like to know what people here, physicists here, feel about Gell-Mann's view, whether his parallel universes – his adaptation of Everett's theory – is not anthropocentric, whereas the Copenhagen interpretation is. Do people feel that's a reasonable claim or not? (silence)

Friedman. All those in favour say "aye." (laughter)

Terkel Petersen. Actually I have a different comment. I am working in international relations. I've been very interested in your play, which I went to London to see, and I've seen it in Copenhagen as well. I think they're very good plays in both places, and that's quite remarkable. But I think there are some elements that perhaps – at least to my mind – are more important than the ones that have been stressed right now.

You've researched into the role of Heisenberg. You indicated that he didn't do something, and of course in history the things that have primarily made the headlines are things that were done. I was wondering if you could tell us how you did research on the June '42 thing, on what he actually did present to Speer. I've tried to follow some of the research you might be using. And then I'd like to draw the line between Gavrilo Princip who actually did shoot the Archduke in 1914 – what kind of mind-set did he have – and the people who were put together in 1962 during the Cuban missile crisis, which has been studied for some time in America last year.

I think that there are some elements of this individual choice that are just wonderfully brought out in your play. When you then have put in the quantum ethics, which you mention in your play, it does do something extraordinary, which I haven't seen any time before, and which is so remarkable; I completely share the enthusiasm of Peter Langdal, that this play is quite extraordinary. What made you write this play, and how did you research on the Heisenberg part, more particularly on the thing he did with Speer?

Frayn. To take the last bit first, the research on Heisenberg: I had to use mostly secondary sources, because they're the only ones I understand. I have to say how grateful I am for all the science writers in the world, who do understand science, and can explain it in a nontechnical, nonmathematical way, to laymen; I was very dependent on that. I went back to original sources for certainly correspondence between Heisenberg and Bohr – I couldn't read the Danish side of it – and I certainly read Heisenberg's original paper in German.

The question of why he didn't do the calculation is fiendishly elusive. As you know, it's Thomas Powers's thesis that he did do the calculation and concealed the result in order to sabotage the program. I have to say there is some evidence for this. I've been looking at it again, thinking about it again, because we're going to do the play in New York next year. I've been rewriting the postscript to take into consideration various books that either hadn't been published when I did the play or that I hadn't known about because they were published in America. I didn't realize there was a separate American edition of the Farm Hall papers edited by Jeremy Bernstein with a very good gloss on the physics in the discussions. If I had I would certainly have used it the first time because I found it very difficult to follow it. These are scientists talking to scientists. They're talking very elliptically. And also in a translation which is not always entirely transparent.

So I've been thinking about it all again. And there is some evidence to support Powers's thesis. The German team do seem to have mentioned estimates in the middle of the war of the critical mass of the bomb of around 50 kilograms, which was extremely close to the right figure. And it's very bizarre that at the end of the war, when they were interned at Farm Hall, Heisenberg was talking about a ton or more. Even then, Hahn actually says to him, "But you used to say it was something like 50 kilograms; why do you now say it's a ton or more?"

Once again, as in so many areas, there is no reconciling all the evidence. I've touched on some of the historical irreconcilables in the text of the play. There are many more I didn't put in because there's a limit to the amount of confusion that you sow within one play. I still don't think I accept Powers's thesis. I think by far the most plausible reading of it is that some sort of guesses were made in the middle of the war, and then Heisenberg went back on those guesses, but never actually really did the mathematics. As I say in the play, I don't think there's any objective way of telling why Heisenberg didn't solve the equation. I just think that it's striking that Frisch and Peierls did do it when they felt justified to work on a nuclear program because they were afraid the Nazis were and they wanted to forestall that. They felt justified in what they were doing.

Plainly, if you look at the Farm Hall papers, the German team really had never ever seriously worked on bomb physics. It wasn't just the critical mass. They hadn't done any of the thinking about bomb physics. They really had all stopped at thinking about a reactor. You can't help feeling that was convenient if what they really wanted to do was not build a bomb. And there's no way of proving it. I can't imagine what a proof would be, of either thesis. But it just seems to me the most psychologically plausible reading of what's on offer.

As you know, it's a view that's disputed on the other side, very strongly, by Rose, Paul Lawrence Rose. He cannot stand anything about Heisenberg at all, and is certain the real reason is Heisenberg was too arrogant, too incompetent, that he had absorbed too much of the Nazi ethos himself; and this is why he didn't do the math. Well, it may be so; I don't think you can prove it either way. But I don't think that's a really plausible hypothesis. I don't know whether that goes some ways toward answering your question.

Man's voice. I would like to hear the panel's comments on what you think are the differences and similarities of the creative minds that are necessary for both artists and scientists. You have to think of two ways, probably, of being creative. Would you comment on that, please?

Friedman. I imagine that what everybody likes to hear is that a certain amount of playfulness is essential. I don't know what is necessary, but I do know that the result ought to be modesty and not arrogance; that great creativity should make one aware of the depths that one can achieve and with that a certain degree of modesty. My obsession with Gullstrand is that there's an exact opposite, and perhaps Einstein being an example of the modesty that comes from delving into mysteries of nature or any other mysteries of the human mind.

Frayn. If you read the accounts of scientists about how they've done things, it often seems to me the case that they have some kind of intuition before they've actually done the proof. I mean, they often seem to take a flyer on things, take a guess, and then demonstrate it.

I think people outside science think of science as a sort of linear logical process where people will simply do the experiments, and the experiments suggest this and that thesis, and it's all very logical and organized. But if you read the accounts of the way that a lot of scientists work it often seems to me not like that. It does seem to me what I was saying about writers, they hit upon the story before they discover what the significance of the story is. I mean, scientists often, it seems to me, hit upon the idea before they discover what leads to the idea. I don't know, since there are scientists here, and I'm not one, whether that reflects anyone's experience or not.

Man's voice. There's something which is a mystery for me, and I would ask a question for Peter Langdal. But before I ask that, I should say that I'm an astronomer. I've seen the play the other day, and I enjoyed it very much. But the mystery then, why does it attract such a great audience? I mean, it has run one and a half year in London, and why? It has no special effects. You even take away all decorations. There are so many thoughts in it, so much physics. Isn't that a mystery?

Langdal. I don't consider it as a difficult play, to watch. It's difficult to work with, in the process when you're developing it, but I think one of the bases of its success is that very often scenography takes away the imagination of an audience. If you build up a whole scene, you just sit there as an audience, very passive. The thing about this play is that when doing almost nothing in terms of effects and all that, you challenge the audience's fantasy, and I think they have a very huge great [experience] when they watch it. That's the reason why they are attracted to it.

Frayn. I think that's a very good point. When I wrote the play I didn't think anyone would even perform it or come to see it. I'm absolutely baffled that it has caught people's fancy. But I think there is something. When the theatre really works, it's a confrontation between the performers and the audience. The audience is an absolutely essential part of it.

And I've sometimes thought it's like the original. The Russian Lvov explained it by bringing two halves, two subcritical masses, of uranium 235 together which became a critical mass when they met and started the chain reaction. I think there's something about the theatre that's like that. You've got half a critical mass on the stage, you've got half a critical mass in the auditorium, and when the two are brought into contact the thing really takes off. This is not just a flattering thing to say. This is really vital. And the most wonderful thing is when an audience goes out of itself towards a play and brings its imagination and intelligence to bear on what's happening on the stage, and fills out the very sketchy movements of a few people making a few moves and saying a few words and the audience read into that a whole world. They bring something of themselves to it, just as actors bring something of themselves to a text: the text written by the author is dead until the actors take hold of it and the director takes hold of it, and find something of themselves inside it. The confrontation, again: it does seem to me absolutely fundamental of the world in every possible way.

Mottelson. I would like to heartily agree with Michael Frayn in his vision of the scientist developing an idea as a kind of dream, a vision, that he doesn't know where it comes from or why, and he believes it's going to be this way, and then, gradually, can explain it more. Mathematics and detailed formulation comes after the imagination that it's going to fit together in some sort of structure. That I believe is a very common experience.

Frayn. I've forgotten who the scientist was who dreamed of the structure of benzene.

Mottelson. Kekule, yes.

Frayn. And you might say in a way it's how Heisenberg did uncertainty. The reason, in the original paper, he proposed uncertainty was then rejected by Bohr, and he then accepted Bohr's criticism. So Heisenberg, in a sense, with hindsight at any rate, stumbled upon an idea for the wrong reason; the right reason came along later.

Langdal. In the play the scientists walk a lot, around whole Zealand, and then they got all their good ideas from throwing stones in the water or something. That's something I know from my kind of art. Every time I lie down on the pillow in the night – then I know (chuckles) what to do the next day.

To your question about what differs in the way of work. When I was a kid I had some blocks I put on top of each other. When I make a play – I don't know whether physicists work like that, but I'll ask them – we put these blocks on top [of each other] – one, …, thirteen, fourteen, fifteen, sixteen, seventeen, and then, what is the best thing to do – YAAAH! My little brother ate up two of them, one is underneath the sofa, and then we put it on again. And then we had thirteen. I remember that Morten Grunwald, a Danish producer, came to me when I did this for the third time. (laughter) But that's the way we work! (laughter)

Sometime you feel very secure when you're doing it, sometimes you feel very uncertain of what is going on, and it differs all the way through the process. Monday you're very sure what you're doing, Tuesday you think this is shit; my dreaming and all my believing I can't use for anything. Then when I start to speak to other people – my colleagues, my actors, my scenographers or what – I experience they've got the same feeling: "Oh, you feel insecure as well?" OK, you start there.

What I noticed from my very short experiences with physicists is that this is so important. I mean, your play has relationships, but it's also a very interesting theme in the play that you do things on your own. Somebody asks Heisenberg, "What about this uncertainty principle; did we make it together or did I make it alone?" This is a place where people invented something together, I think, actually. That's a very big part of creative work, I think – human relationships. For me, as an artist, that's where it all begins. A bit like music – pop a diddle oo – tk tk tk – and something develops.

Frayn. Alternating confrontation and withdrawal into oneself, and the two elements do seem to be, usually, essential in everything: artistic creation, scientific thinking. I'm still hoping somebody's going to say something about Gell-Mann. (laughter)

Friedman. "Waiting for Gell-Mann."

Frayn. I don't know whether people here have read Deutsch, who's another great follower of Everett. It seems to be a rather extreme version of Everett's multiple-universe idea. Deutsch certainly says hardly anybody now accepts the Copenhagen interpretation – hardly any physicist now accepts the Copenhagen interpretation. Is that true?

Woman's voice. I can throw in Einstein's statement which applies to several of the things that have been talked about here. Einstein said, "The most beautiful thing we can experience is the mysterious. It is the source of all great science and art."

Frayn. The universe theory I find extremely mysterious. But Finn, are you not going to rise to this provocation?

Aaserud. No, I'm not. That is not my specialty. I leave that to the physicists. But while we are waiting for the physicists I might take up something else, perhaps. When we were preparing this we e-mailed a little bit, and I asked Michael Frayn to what extent he saw "Copenhagen" as some kind of dissemination of science; whether there was an educational aspect to it. You objected to that fairly strongly and said that your issue was epistemological not pedagogical, or something to that effect. That is one side of it. "Copenhagen" is probably to you more in the continuation of your writing than it is a sudden historical contribution or a sudden pedagogical tract.

The other side of the coin, perhaps, is the audience problem – well, it's not a problem, but this play is so incredibly popular. I remember, I was reading your play first in bed as a regular novel. I couldn't understand anything about why this was so popular. You were dropping names, you were talking about technical terms, and it boggled my mind. And then my wife and I, in connection with cleaning the Danish translation, read it aloud to each other, and all of a sudden it worked. So that's part of it, you know, it's the craft of theatre. When I was in London and saw it, you had almost as many reactions and understandings of the play as there were people (I didn't speak to everybody, but I spoke to a few). As a historian of science with some knowledge of physics and all that, I think I was in a minority of how I understood the play. It's not dissemination of science in that respect either, because you give people something else. So, perhaps, if you could on the one hand say a little bit about how and whether you fit this into your own way of writing and what to you is a good audience in some respects. I don't know if the question is clearly phrased.

Frayn. I certainly didn't have any pedagogical intentions. Sending for me to expound science would be like asking a tone-deaf man to write a symphony – I wouldn't be the right person to do it. As I said before, I felt I had to explain the science in some detail in order to make the story clear, because the story turns so much on why it was so difficult to build the bomb, for instance, why you had to separate the uranium 235, why it was so difficult to separate the uranium 235, and the whole significance of the critical mass had to be explained – you couldn't really tell the story without it. But it was the philosophical point I think I was aiming at.

Aaserud. There are passages in this book [Headlong] here that I found very parallel to this. I'm not going to read them because Benny has just asked to pose a question.

Benny Lautrup. It's more rising to the challenge that you've thrown out a couple of times now. I'm a physicist, but I'm not particularly deeply involved with the foundations of quantum mechanics. But let me say that the Copenhagen interpretation, the way I see it, is at least that you should not speak of things of which you have no way of knowing. In this way, I find, for example, the Wheeler–Everett idea about the multi-universe splitting off is talking about things that you have no way of actually getting any knowledge of. So I find it quite unattractive, this multi-universe theory. However, let me say about the Copenhagen interpretation, it's certainly not dead. It is living in every textbook on quantum mechanics today, and all students learn it. The Everett–Wheeler idea is perhaps mentioned in some very late books, but definitely not standard teaching, so I would rather conclude that the Copenhagen interpretation is well and alive.

Frayn. I've certainly put the question to various physicists in Britain, who've been astonished at this claim. But Deutsch makes it very strongly. He's a physicist working on a theoretical program to build a quantum computer. That's his line, at Oxford. I was astonished at the sheer boldness of it. And Gell-Mann is very dismissive too, and very sweeping, but it seems not to be so, to me.

Lautrup. That doesn't make it right.

Frayn. No.

Aaserud. Thank you, Benny, for rising to the occasion. There's a question there.

Åsa Melldahl. I'm a director and going to work with this wonderful play at the Dramat in Stockholm. I hope that God will not punish me for even trying to have a hypothesis or talking about that out loud when it comes to this play, that I have only started together with the actors to try to get into.

But since the question of why is this so immensely popular has come up. We started to discuss that of course in Stockholm, too, and someone said that it is probably partly at least because it melts together an Oedipus drama and a Faust drama. And it does it in such a modern way and in modern surroundings. So that we, all people living now, in this new millenium soon coming, can start this traveling into, I mean, why, why are we here, what is the meaning of it all, and so on – and what is our guilt, what are the sins that we have committed, so that Thebe is now struck by pests, like in Oedipus. Do we have the right to start to freeze time. And so on? The sins that we are committing. This play gives us the opportunity to search for the sources of the sins and maybe also some of the answers – I mean, like in Helsingør, in the darkness of the human soul – and in a very humoristic way, too. I think that is why it's so popular, because it's so serious when it comes to these profound questions.

Frayn. Doing the research was an object lesson for me in the difficulties that historians face in establishing any agreed version of the – everyone's memories' variance over absolutely everything.

One of the great ambiguities, controversies, that I've left out completely is about "the drawing." Hans Bethe insists that Niels Bohr brought a drawing to Los Alamos which he had been given by Heisenberg during the 1941 meeting, and that it was handed round a meeting of the team at Los Alamos to try and establish what it showed. Did it show some form of bomb, or did it show some form of reactor? Hans Bethe remembers this absolutely clearly; various other people in the team remember that it was shown around. I hope I'm pronouncing it right, Aage Bohr – Niels Bohr's son, who was with his father here in 1941 and in Los Alamos with his father in 1944 – is absolutely insistent that there was no drawing. How can you possibly reconcile these things? I don't think there is any way of reconciling them. All you can do is record – I suppose it's "complementarity" again (laughter) – record these versions of what people recall. I've left that one out of the play because I've just got so many in already. Again, all the stuff about whether the German team had actually made any calculations, how they seem to have hit upon this weirdly accurate figure of around fifty kilograms if the calculation hadn't been done.

Langdal. I think the reason why it's so interesting to me is that the story is so interesting, so fascinating, from a historical point of view as well: I thought, is it actually a play about science? I think it's a play about human beings, how they react to each other, and not actually a play about science.

Frayn. Everything about the events that the play treats is just so extraordinary. It's an extrordinary story, whatever you make of it, Heisenberg's trip to Copenhagen.

But the whole history of atomic physics in this century is even more extraordinary when you think that in the twenties the work that was being done here was entirely abstract, it was absolutely abstract science, which would have no practical consequences in the world whatsoever. It was like theology, or something, and it turned out to have this collossal huge and terrifying physical consequence in the world. But when the work was originally done in the first forty years of this century, that was completely unforeseen, until fission. It was assumed that people realized that huge quantities of energy would be released in fission, and suddenly people thought, well, maybe there is something, maybe it does have a practical application. It's almost as if people in some quiet theological college debating some absolutely abstract thing about the nature of God and sin, and suddenly the whole future of the world turns out to depend upon their discussions. Seems a strange story.

Aaserud. Talking about the relationship between history and physics, which is part of our discussion today, I'm reminded of the end of your play which is somewhat perplexing to me, because – and it would be interesting to hear whether I've completely misunderstood – it seems to me there that you propose a kind of uncertainty principle for history. And that it was because we have this uncertainty principle even in history that we survive. Something to that effect. Have I read that completely wrong?

Frayn. I haven't quite grasped your thesis.

Aaserud. Well, I don't know if I can find it. If it doesn't strike you at once it might be difficult to find it.

Frayn. While you're looking it up, I once, while I was a student at Cambridge, saw a debate between a philosopher and a scientist, at the philosophy of science club. The philosopher was Professor of Philosophy Wisdom; the biologist was going to put a paper proposing some question, some problem, in the philosophy of science, and Professor Wisdom was going to reply. The biologist read his paper, and as it went on I realized I couldn't understand anything about it at all; I simply could not understand what the general drift of the paper was at all. When he finally sat down, Professor Wisdom rose to reply. Wisdom had been one of Wittgenstein's people, and he was very given to doing philosophy in the lecture room in the way that Wittgenstein had; he'd like to switch off and think. So it was not very surprising that what he did, first of all, was to put his head back and clap his hands (laughter) and think. He thought and he thought and he thought, in absolute silence. First of all, we all waited politely. Then it became slightly comic, then it became embarassing. It's very embarassing just sitting in silence as the minutes go by. Gradually the audience began to trickle out of the room. Finally, after literally something like ten minutes, when the chairmen didn't know whether to bring the meeting to a close, finally, Wisdom took his hand away from his forehead, and said to the biologist: "Would you mind repeating your question?" (loud laughter) That was exactly what I was thinking; I didn't understand a word, what was he talking about! Anyway … (laughter)

Aaserud. It's at the very end, and it says, "Our children, and our children's children. Preserved, just possibly by that one short moment in Copenhagen. By some event that will never quite be located or defined. By that final core of uncertainty at the heart of things." There I interpreted the event as a historical event; that is why I was asking about it.

Frayn. My thesis at the end of the play is that, if the meeting had gone as Heisenberg had planned, and if Bohr had remained calm about it, Heisenberg would have said, "We now realize that you can make a bomb with plutonium, if we can get the reactor running, but there's no chance of ever getting enough uranium 235 because you'd need tons of it."

If he'd been able to explain that, and if their relationship had gone on as it had been in the twenties, when they thrashed out everything to the bottom, Bohr would surely at some point have said, "Well, hold on, have you actually done the calculation of the critical mass? Have you calculated it?" And Heisenberg would have said, "Well, I don't need to because, you know, we all know the figures for natural uranium." And Bohr would have said: "Well, but that's for natural uranium, you need to do it for uranium 235." They would have then done it, and Heisenberg would then have been faced with the knowledge that they could in fact produce a bomb with relatively very small quantities of uranium 235.

I think it's still wildly unlikely that Germany could have ever produced a bomb, but it is just possible, had they realized that it was a matter of kilograms and not a matter of tons. It was the failure of that conversation, the failure of Bohr to find that out, which may have preserved us from a German bomb. The world would have been a very different place if the Germans had built their bomb, as they would have had to do before the Allies built their bomb.

Aaserud. Well, Peierls and Frisch too, of course, made the wrong calculation; they just made it the other way around, so it looked more likely.

Frayn. That's one of my appalling errors that remained in the play for at least a year. Frisch and Peierls estimated the critical mass of a bomb would be, in their first rough calculation, about half a kilogram, and in fact it's around fifty kilograms. In my original line I say their calculation was ten times under. That remained in the play, I regret to say – seen by many many scientists, physicists, mathematicians, and so forth – until about six months ago when someone said, "Sure you don't mean a hundred times?" (chuckles) And of course I do.

Man's voice. I have one question. During the meeting of the play, which has not been discussed at all here, it seems to me that you bring uncertainty to bear on moral choices, because you say you never know the reason why people do things. Now is this the true idea or a kind of value needed, or is it a warning for us, not to fall back on that to justify things which we don't know can be justified?

Frayn. I think there is a wider parallel between the psychological-moral question, on the one hand, and the physical question on the other, in that for most practical day-to-day questions, classical physics are absolutely adequate. You can tell the position of most objects in the world absolutely adequately, even for very precise purposes like astronomy, by the use of classical physics. It's only in certain special cases you have to take into consideration the difficulties introduced by uncertainty.

I think it's somewhat the same with moral questions, and motivational questions, that for most practical reasons – most practical matters from day-to-day – we know more or less why people do things. They eat because they're hungry, they lose their tempers because they feel insecure; it's all reasonably straightforward. But there are difficult cases, as there are difficult cases with determining the position and the other qualities of particles, where one has to be very cautious and say that no objective knowledge is possible. You still have to make estimations of whether Heisenberg was really trying to build a bomb or really trying not to build a bomb. But I think one has to recognize there is no absolute objective correlative to this, that we have to make interpretations, and the interpretations and stories, images, projections, sympathetic guesses is the best we can do.

Aaserud. Now, of course, we get to the difference between drama and history and literature and history, perhaps. Because you know that is something history can't do, to make those guesses. I was corresponding with a colleague of mine who said that she has never been able to deal with this particular episode historically. And when she experienced your drama she said, well, that's perhaps the way to deal with it. Maybe the historian can't and the dramatist can.

Friedman. I would say what you just said is exactly the way I, and I think most of us, would work as an historian. The difference is that in a piece of historical scholarship it's possible for the author, either in a footnote or some formulation, to indicate this is the best we can do. You could also look at it this way, or this evidence says that, etc, etc. When we're on stage or on film this note certainly would interrupt the dramatic flow, as well as the fact that you can only absorb so much.

I think both a good dramatist and a good historian will try to go into the mind of the person and create the full social, personal life to understand motives and intentions as best one can. And then it's a question I think of the integrity of both the historian and the dramatist to draw conclusions from that, that you can live with – that you can look in the eye of somebody and say that you really believe this is the case, that you don't take the opportunity, perhaps, to find a little bit more dramatic interest by putting some nasty motive or imputing a certain dark secret part of their soul. Because when people walk out, most people – maybe some – have heard of Heisenberg and Bohr [for the first time], and this is the only picture they have of these two individuals. What type of people are they, I think, is important. I think the ethical problem is when you manipulate to get an effect that isn't true. But I think the historian and dramatist would work the same way. As we know there are plenty of historians, even academic historians with good names, who occasionally will cross the line and try to create something a little bit more sensational that isn't justified.