Materials from PBS site on Frayn’s Copenhagen and the PBS film version of the play.

The idea for Copenhagen came to me out of my interest in philosophy.

It was when I read a remarkable book called Heisenberg's War by Thomas Powers, that I came across the story of Werner Heisenberg's visit to Niels Bohr in 1941. As soon as I read it I began to think that this story reflected some of the problems that I had been thinking about in philosophy for a long time.

How we know why people do what they do, and even how one knows what one does oneself.

It's a fundamental question... this is the heart of the play.

Indeterminacy

We can [in theory] never know everything about human thinking.

I wanted to suggest with Copenhagen that there is some kind of parallel between the indeterminacy of human thinking, and the indeterminacy that Heisenberg introduced into physics with his famous Uncertainty Principle.

Though I'm not trying to say they're exactly parallel.

The uncertainty principal says that there is no way, however much we improve our instruments, that we can ever know everything about the behavior of a physical object.

And I think it's also true about human thinking.

It took me a long time to figure out how to do this play.

For a start I couldn't quite think what the focus of the play was going to be, or how many characters it was going to have.

One of the wrong alleys I went up was thinking that I would dramatize what are called the Farm Hall Papers. This is the record that was made by the British Intelligence of the conversations of the German physicists after they had been arrested and interned in a country house in England in 1945.

It's an extremely interesting document, one of the best sources of finding out what was going on in the heads of the German physicists.

But then I thought, that's not really the story I want to tell.

Gestapo Point of View 

The story is really about the meeting in 1941. I knew that both men would probably be under surveillance by the Gestapo, and Heisenberg was certainly under surveillance by British intelligence later on.

So I thought I would have the Gestapo and the British Intelligence listen in on the conversations and tell the audience what was going on. But then gradually I thought 'do we need these people?' Do we need these extras just sitting in the darkness listening to what's happening. We've got an audience already, why not use them?

So in the end that's what I have done. I've made the audience who sat in the theatre the audience for the conversations of Bohr and Heisenberg.

On Margrethe
I thought we needed three characters. We obviously needed Werner Heisenberg and Niels Bohr, but I thought we needed Niels Bohr's wife Margrethe as well.

We needed her for two reasons. Partly because she historically had no scientific training and yet her husband discussed all his work with her. And they agree at the beginning that they are going to make everything plain to Margrethe. So Margrethe is our representative there.

The second thing about Margrethe is that she didn't much like Heisenberg. Niels Bohr adored Heisenberg. She always had a much more negative view of him and she was particularly suspicious of that meeting in 1941. She said afterwards, whatever anyone says, that was a hostile meeting.

Margrethe is there in the way that all the other people in the world are attempting to explain his behavior. And almost everyone who is not Heisenberg took a very hostile view of Heisenberg's behavior. So the Margrethe character expressed that side.

Bohr as Father Figure
Bohr and Heisenberg met kind of a need in one another. Bohr was older and a kind of father figure, not only to Heisenberg but for a lot of young scientists.

Their relationship was one of the classic friendships of science.

Bohr did most of his original work as a young man. By the time he reached middle age he was doing some original work, but his best work was done in collaboration with young physicists who came and worked with him in Copenhagen.

Bohr was very good at challenging people to think about what they were saying, to go further in their thinking than they had dared to go before. Heisenberg was exactly the converse of this, someone who needed a father figure.
                       
The Structure 

The play starts in a fairly natural mode.

Heisenberg arrives at Niels Bohr's house and it's a very embarrassing meeting because Bohr did not want to be visited by a German in 1941. He did not want to appear to be collaborating. Heisenberg plainly wanted to say something to Bohr or he wouldn't have insisted on the meeting.

The play begins with this very awkward conversation between them and then they go out for a walk. Something goes wrong with the conversation, we don't discover what, but they come back to the house and Bohr says Heisenberg's leaving.

Then the characters try to reconstruct what it was that was said during the walk, which they never agreed about. And they do three drafts of this. They go through the conversation three times before they come upon some sort of explanation of what was happening.

It never occurred to me when I was writing it, but some interviewer pointed it out afterwards, that it was the same structure as an earlier play of mine called 'Noises Off.' 'Noises Off' is a farce about the theatre and we see the same actor in the same play three times over.

I seem to be plagiarizing my own structure.

History  vs Fiction

I knew that whatever I did, however much I read or studied, I would not be able to catch the manner of being of Heisenberg and Bohr, let alone Margrethe who is much less well recorded in historical record.

I was inhibited when I began to write... it was the first time I based fictitious characters on real people.

But after a time the characters do what fictitious characters always do, they begin to take on a life of their own.

One of the more chastening, and also one of the most intelligent things that was said about the play, happened the first night in New York. I went backstage and I met a very tall, very charming young man who said, I am Werner Heisenberg's son.

'Of course your Heisenberg is nothing like my father,' he said, 'I never saw my father express emotion about anything except music.' Well that was quite a chastening reminder that I was not actually going to have hit the real characters.

But then he continued, 'But in a play, I recognize you have to have characters who are rather more forthcoming than that.'

And I thought that this was a terrific understanding of what plays are doing. They are not just recording the historical record... but trying to find the truth that never quite got expressed in life.

Learning The Physics

I knew nothing about science at all.

When I began to do the play, I read everything I could possibly read about the subject comprehensible to a lay audience.

When I finished the play I sent it to two scientists to check the physics. One of them made some suggestions which I adopted, but there were still mistakes that survived.

In the early months of the production in London, I kept getting letters from scientists who said often, very sweetly and very politely, I think you should take another look at this section. 'I don't think you mean atoms of water vapor, I think you mean molecules of water vapor.' And of course I adopted these suggestions too.

Filming the Play

When the proposal came up to make a film of this I was extremely cautious...

I was very reserved about making a film of Copenhagen. But I was convinced by Howard Davies, who is directing it, that he could see a way of making it work.

He adapted the script for television, and he has had to cut a great deal out including a lot of the science. But I think it still makes sense.

It is a pretty bold venture. It uses film in a way in which its not normally used.

Naturalism is the natural mode for film it seems to me. But you can't really stick to naturalism in this film, if only because everyone has come back from beyond the grave to have this conversation.
When the play opened in New York it aroused much more controversy than it had in London.

There were a number of American scientists and historians of science who think I have been too soft on Heisenberg, although he is bitterly attacked by Margrethe in the play.

Heisenberg is allowed to make his own case to try and argue out why he did what he did, not only in the meeting in Copenhagen with Bohr, but also during the war in serving German science.
Bohr's Position

Niels Bohr never commented publicly on the meeting in his lifetime. He only told one or two family members and colleagues what he thought had happened at the 1941 meeting. He didn't say anything more about it until after the war when Heisenberg tried to establish with Bohr what had occurred.

Heisenberg was very eager to have some agreed version of the meeting established. But they couldn't agree, so they abandoned the idea.
                       
Heisenberg's Version

Neither of them said anything more about it until some point in the 1950's, when Robert Jungk wrote a book exculpating the German scientists, suggesting that they had tried to run some kind of resistance movement to Hitler.

Heisenberg gave Jungk his version of the 1941 meeting, which appeared in the book. When Niels Bohr read Heisenberg's account he was very angry. He thought that Heisenberg had completely misstated what had happened.
                       
The Bohr Letter

Bohr wrote a letter to Heisenberg, but characteristically he didn't send it. He went on redrafting it, just as he had always redrafted his scientific papers. In fact he went on redrafting it for the rest of his life.

What he was trying to do -- also very characteristic of Bohr -- was to be very precise about what had happened in the meeting as he recalled it. I also think he was trying to find some way of disagreeing with Heisenberg, without hurting Heisenberg's feelings.

The letter was found after his death among his papers.
           
Niels Bohr 1885 - 1962
           
Niels Bohr was one of the most influential scientists of the 20th Century and a major force in the field of quantum physics. He won the 1922 Nobel Prize in physics for his study of the structure and radiation of atoms. [See the animation of "The Bohr Atom", below, right.] Bohr recognized that Ernest Rutherford's model of the atom, in which electrons emitted radiation continuously, was unstable according to the laws of classical physics. Bohr postulated that radiation is emitted from atoms not as a result of the periodic motion of the electron in its orbit, but only when an electron "jumps" from one orbit to another losing energy that is emitted as radiation. Bohr's theory of the compound nucleus, in which the repulsion between positively charged protons is countered by huge amounts of energy in order to hold the nucleus together, helped lead to the hypothesis that splitting an atom would produce enough energy to fabricate a powerful weapon.

Bohr's father was a well-known Danish physiologist, his mother came from a wealthy family of Jewish bankers. Bohr earned his Ph.D. at the University of Copenhagen in 1911, then worked in Cambridge, England with J.J. Thomson, discoverer of the electron, and in Manchester with Rutherford, who proposed the first nuclear model of the atom.

Margrethe Norlund and Niels Bohr engaged, 1911
In 1909 when his brother Harald left to pursue his own academic endeavors, Bohr hired Margrethe Norlund to type his numerous papers. One year later, the two became engaged and married in 1912. The marriage would produce six sons.

In 1921 Bohr was named director of the new Institute for Theoretical Physics in Copenhagen, which soon became a requisite destination for atomic physicists from around the world. During a lecture series in Gottingen, Germany, Bohr befriended the young Werner Heisenberg, [see video above] initiating their famous collaboration. In 1933, after the Nazis authorized German universities to fire staff on the grounds of politics and race, Bohr enabled young refugee physicists to come to his institute.
           
After Germany occupied Denmark, Bohr fled with his family to Sweden, and then to the United States where he helped develop the atomic bomb. As early as 1944, however, his concern about harnessing the power of nuclear energy led him to advocate control of nuclear weapons and world peace through the open sharing of knowledge among nations. He expressed these ideas to Winston Churchill and President Franklin Roosevelt, both of whom rejected his recommendations. After the war, he helped establish CERN, the European nuclear physics laboratory, and organized the first Atoms for Peace Conference in Geneva in 1955. He was the first recipient of the Atoms for Peace Award.

In 1956, Robert Jungk published a book, Brighter than a Thousand Suns, about the German atomic bomb effort during the war. The book included an excerpted letter from Werner Heisenberg detailing his recollection of his meeting with Bohr in Copenhagen in 1941. Heisenberg's recasting of the events so angered Bohr that he drafted a letter to Heisenberg renouncing his version of the meeting. However, the letter was never sent. But in February of 2002, in order to clarify Bohr's position about the meeting, the Bohr family posted on the internet the draft letter and other documents pertaining to the 1941 meeting.

Niels Bohr died in 1962 and is buried in Copenhagen.

Margrethe Bohr 1890 - 1984
           
Margrethe Norlund grew up the daughter of a pharmacist in the small Danish town of Slagelse, some 50 miles south-west of Copenhagen. She was studying French for a private teacher's certificate, when in 1910 she met the brothers Niels and Harald Bohr, friends of her own brothers. A year later she was engaged to Niels, and in 1912 they were married in a brief civil ceremony. They had six sons.

Margrethe acted for years as her husband's assistant, taking dictation and typing the numerous drafts of his scientific papers he was in the habit of producing. She was more than just his assistant, however, she was also a sounding board for many of his scientific ideas.

In the early 30s, the Danish government honored Niels by moving him and his family into the "Residence of Honor," a palatial mansion on the Carlsberg Brewery grounds reserved for the country's foremost scientist. There, Margrethe officiated with great warmth and charm over the many receptions held for visiting scientists and high dignitaries, from England's Queen Elizabeth II to the Indian Prime Minister Jawaharlal Nehru.
           
When the Germans occupied Denmark in 1940, life for the Bohrs became difficult. Although Niels was baptized a Christian, his mother was Jewish, marking him in the eyes of the Nazis. Because of this Jewish heritage, and because she did not want her family to appear to be collaborators to the Danes, Margrethe was concerned when Werner Heisenberg came to Copenhagen in 1941 to talk with her husband. In 1943, when the Gestapo rounded up Danish Jews and had orders to arrest Niels, the family divided up and escaped by separate fishing boats to Sweden, where they were reunited. Bohr continued on to England, and then with his son Aage later traveled to America. Margrethe remained in Sweden for the duration of the war with the rest of the family.

After Niels Bohr's death, a friend of the family spoke about Margrethe and Niels' marriage: "It was not luck, rather deep insight, which led him to find in young years his wife, who, as we all know, had such a decisive role in making his whole scientific and personal activity possible and harmonious."

In 1984, thirty-one years after the death of her beloved Niels, Margrethe Bohr passed away at the age of 95.
She is buried with her husband in Copenhagen.

Werner Heisenberg 1901-1976
Werner Heisenberg won the Nobel Prize in physics in 1932 for establishing the field of quantum mechanics. Heisenberg suggested that any theory of the atom must be based on observable phenomenon, such as the spectral lines emitted by atoms, and not pictorial constructs such as Bohr's nuclear model of the atom. For Heisenberg, this observable data could be culled to formulate a set of possible values for a hypothetical particle. These values could then be used to calculate, by mean of mathematical formulas, the probabilities of particular energy states and transitions among those states.

Quantum mechanics had a profound influence on the development of atomic and nuclear physics by providing a model for calculating such formulations as critical mass. Using mathematical laws of probability, nuclear physicists were able to determine how much fissionable material would be necessary to ensure the likelihood that enough neurons would collide with the material to cause fission, thus leading to the development of nuclear reactors and atomic bombs.

Heisenberg is best known for his uncertainty principle of 1927. The principle posits limits to the accuracy of knowledge about atomic behavior, since the means by which the researcher measures such phenomena -- short wave radiation bounced off a particle, for example -- alters the behavior itself.

The son of a university professor, Heisenberg studied theoretical physics under Arnold Sommerfeld at the University of Munich. During a 1922 lecture given by Niels Bohr at Gottingen, Heisenberg publicly questioned the mathematics of the Nobel Prize winner, earning Bohr's attention. Bohr invited Heisenberg for a hike, initiating their famous collaboration. Heisenberg received his doctorate in 1923, then went to work with Niels Bohr in Copenhagen. In 1927, Heisenberg returned to Germany to teach physics at the University of Leipzig.

Early in World War II, the deeply patriotic Heisenberg had conducted for the Germans chain reaction experiments with heavy water that led him to believe in the feasibility of a nuclear weapon. Heisenberg visited his mentor and former teacher, Niels Bohr, in Copenhagen in 1941, perhaps to ask his advice on the right course of action for the development of atomic energy. It is not certain what was said during this meeting, however Bohr came away with the impression that the Nazis were actively developing a nuclear bomb. Within a few days before Germany's surrender, Heisenberg was captured by Allied forces and incarcerated with other German atomic scientist at Farm Hall, a country estate near Cambridge, England. It was later determined that the Germans were never close to developing an atomic bomb. [For more on this topic, refer to the Journal of Chemical Education Webite.]

After World War II, Heisenberg directed the Max Planck Institute at Berlin, and then moved to the Max Planck Institute for Physics at Gottingen where he remained for the rest of his career.

In 1955, while working on a book about the development of atomic physics in Germany during the war, Robert Jungk queried Werner Heisenberg about his Copenhagen meeting with Niels Bohr. Heisenberg complied by sending a letter back recollecting what happened. An excerpted version of his letter was subsequently published in Jungk's book "Brighter Than a Thousand Suns."

Heisenberg's account of their meeting so upset Bohr that he dictated a letter to Heisenberg detailing his own, and very different, recollection of what had transpired. In the end, Bohr never sent his letter. In February of 2002, the Bohr family published Bohr's draft letter to Heisenberg on the Internet. The issue of what Heisenberg and Bohr said to one another in 1941 Copenhagen is still open for debate.

Werner Heisenberg died in Munich in 1976.

The Moral Dilemma of The Bomb

While Niels Bohr and Werner Heisenberg were meeting in Copenhagen in 1941, the American nuclear bomb program was still in its genesis. Colonel Leslie R. Groves, an Army Corps engineer who had just finished building the Pentagon, took charge of the program -- now called the Manhattan Project -- in September of 1942. Groves quickly hired Dr. J. Robert Oppenheimer, a brilliant physicist, to be the project's scientific director.

           
Because secrecy was of paramount importance, both men knew they needed a central laboratory in some remote location where they could build and test a bomb. In the fall of 1943, Oppenheimer and his team found the perfect site -- a mesa of 7,200 feet above sea level completely isolated from any major city.

The site they chose was Los Alamos, New Mexico.

Construction on cheap barracks-like buildings not meant to outlast the war began almost immediately. Within three years, the Los Alamos Laboratory had designed and was very close to completing two prototype atomic bombs.

Meanwhile, the war in Europe had ground to an end. V-E Day was declared on May 8, 1945, with Germany in ruins and 39million people dead. With the war against Japan still raging in the Pacific, however, the pace at Los Alamos did not let up.

By the summer of 1945 a bomb was ready for testing. A flat and desolate area was chosen 200 miles south of Los Alamos near the Alamogordo Bombing Range. Oppenheimer named the test site "Trinity."

On July 16, 1945, at about 5:30 in the morning, soon after a thunderstorm had swept clean the area, the first nuclear bomb was exploded.

Letters from the Niels Bohr Archive

Opening Letter

Why the Bohr family in February of 2002 decided to publish the documents.

"The family of Niels Bohr has decided to release all documents deposited at the Niels Bohr Archive, either written or dictated by Niels Bohr, pertaining specifically to the meeting between Bohr and Heisenberg in September 1941. There are in all eleven documents..."

View the entire document at the Niels Bohr Archive, Copenhagen website:  http://www.nbi.dk/NBA/webpage.html

            View the entire document at the Niels Bohr Archive, Copenhagen website:  http://www.nbi.dk/NBA/papers/introduction.htm

                       
Do they Reveal Anything New? 

Finn Aaserud, Director of the Niels Bohr Archive in Copenhagen believes the documents do shed new light on the 1941 meeting, but with reservations.

"...it was Bohr's definite impression that Heisenberg simply informed him - in general terms - of the existence of a German atomic bomb project and his own involvement in it...."

View the entire document at the Graduate Center, CUNY website:
http://web.gc.cuny.edu/ashp/nml/artsci/aaserud.htm