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The foundation also seeks to portray the lives of men and women

Engaged in scientific and technological pursuit;

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From viewers like you. Thank you.

"Copenhagen" will begin after this brief introduction.

Michael frayn: A lot of people think the play

Is about moral questions--

About whether scientists should work on weapons.

And of course, moral questions do come into it.

Before we can make any moral judgments of anyone,

We have to understand why they are doing what they do.

You can't make a moral judgment about anyone

Unless you have some knowledge of their intentions.

My play, "Copenhagen,"

Is based on a real event and a real mystery.

It's about a meeting between two great scientists

During the second world war,

In nazi-occupied Denmark--

Werner Heisenberg, the german physicist;

And Niels Bohr, the danish physicist.

Now the two men had been close friends

And colleagues for over 20 years.

They had pioneered the field of atomic physics,

And eventually, their work would lead

To the development of the first atomic bomb.

And the problem was

That at the time of the meeting in Copenhagen

They were on opposite sides in the war.

So the meeting was fraught with difficulty from the beginning.

And ever since then, people have argued

About what it was the two men said to each other at the meeting,

And what it was that Heisenberg wanted to say.

They were two of the greatest physicists of the 20th century,

Because they had begun to establish

What happens inside the tiny world of the atom.

When they first met at the beginning of the '20s,

Niels Bohr was already extremely famous.

He was a great physicist who had won the Nobel prize for his work.

And Heisenberg was a young man at the very beginning of his career.

A very cheeky and brilliant young student.

And they did a lot of their very best work together.

They had taken the lead in developing quantum mechanics,

Possibly the most important and successful theory

Ever to be introduced into physics.

Michio kaku: It was a match made in heaven.

With Bohr pioneering the physical picture

That he could see in his mind's eye.

And Heisenberg, the mathematician,

The person who could then put into concrete mathematical language

The dance of atoms.

The dance of electrons that Bohr could only dream about.

And that's where Niels Bohr and Heisenberg worked so well.

Heisenberg's famous "uncertainty principle"

That he introduced into quantum mechanics in the 1920s,

Demonstrates that we can never have total knowledge

Of the behavior of physical objects.

It only matters when we are talking

About very fast moving ones, like particles.

But in theory, it applies to everything.

And if we can't know everything

About a physical object,

We can't make predictions about it.

Heisenberg's uncertainty principle

Challenges our normal understanding of the world.

Michio kaku: We physicists go crazy

When we think about the uncertainty principle.

Some people think that physics is a finished question;

We know everything given enough information--

You know where objects are.

You know how they are gonna perform.

You can predict the outcomes of things.

So it's really upsetting-- it's really upsetting

To some people at a very deep fundamental level

That we physicists really don't know

Where things really are at any given time.

That ultimately, there is this uncertainty

That goes to the very heart of reality itself.

Frayn: Heisenberg was still only 33 when he won the Nobel prize

For the uncertainty principle.

But it was also the year in which Hitler came to power.

Heisenberg could have left Germany--

He was offered jobs in various american universities.

( crowd chanting ) seig heil! Seig heil!

Heisenberg has been much criticized because he didn't go.

Absolutely no one thinks Heisenberg was a nazi

Or a nazi sympathizer.

The criticism that's made of him is that he acquiesced,

That he was too prepared to compromise with the nazi regime.

The advent of Hitler began to place

A great strain on the friendship between the two men.

Then there was a discovery in the field of atomic physics

Which changed everything.

In the 1930s, it was demonstrated that if you fissioned the nucleus,

If you split the nucleus of an atom, it released energy.

It suddenly seemed theoretically possible

To use atomic physics to produce power

For other constructive or destructive purposes.

This was the moment

When atomic physics ceased to be purely abstract

And took on an immense significance

For the future of the human race.

Niels Bohr, because he liked to think in terms of physical pictures,

Had the idea that the nucleus of the atom was like a droplet of water,

Where surface tension kept the droplet of water intact and spherical.

However, if you came in and hit it with an outside object,

This liquid drop could then fission in half,

Into two smaller liquid drops. And then he realized

That perhaps you could release fantastic amounts of energy,

The energy that was known to be stored in the nucleus of the atom,

By splitting it with this liquid drop.

And then, he very rapidly calculated

That you had to have an exotic form of uranium,

U235.

Then began an international chase

To see who could get this fabulous u235,

This rare form of uranium.

What was at stake was the fate of humanity itself.

Bohr and Heisenberg were the leaders in a kind of physics

That could now be used to produce,

In theory, a most terrible weapon.

But they were cut off from each other.

When the war broke out in 1939, Heisenberg knew

That that was the end of his contact with Bohr in Copenhagen.

And he wrote a very moving letter to Bohr,

Which goes right to the heart

Of the father-son relationship they had.

"dear Bohr, since I don't know whether

And when our destiny will lead us together again,

I will once again thank you for all your friendship,

For everything I have learned from you

And for everything you have done for me.

In old friendship, yours, Werner Heisenberg."

Frayn: In 1941, the two men

Had been out of contact for two years.

And Bohr had been living precariously,

Because he was half-jewish, under nazi occupation.

And what he didn't know was that his old friend Heisenberg

Was now running the german atomic research program.

Now this enormous difficulty--

Heisenberg managed to go to Copenhagen,

And he was very insistent

On a personal meeting with Bohr.

According to Heisenberg,

They began some kind of conversation.

Niels Bohr became upset and then angry

And the conversation was broken off,

According to Heisenberg,

Before he could explain what it was he wanted to say.

And people have been arguing ever since about two things:

What it was they did actually manage to say to each other;

And what it was Heisenberg wanted to go on to say.

I thought the meeting suggested a very good parallel

Between Heisenberg's uncertainty principle

And the psychological uncertainty that I think exists,

The theoretical barrier in knowing why people do what they do.

And the particular difficulty of knowing

Why Heisenberg went to Copenhagen

Seemed to focus the difficulty in one particular incident.

And what the play is about is whether we can

Really have any absolute knowledge of anyone's intentions.

Announcer: And now "pbs hollywood presents:'Copenhagen.'"

( tower bell rings )

( steeple bells ring )

( doors hiss )

Margrethe Bohr: But why?

Niels Bohr: You're still thinking about it?

Margrethe: Why did he come to Copenhagen?

Does it matter, my love, now that we're all three of us dead and gone?

Margrethe: Some questions remain

Long after their owners have died.

Some questions have no answers to find.

Why did he come? What was he trying to tell you?

He did explain later.

He explained over and over again.

Each time he explained, it became more obscure.

It was probably very simple, when you come right down to it.

He wanted to have a talk.

"a talk"? To the enemy? In the middle of a war?

Margrethe, my love, we were scarcely "the enemy."

It was 1941.

Bohr: Heisenberg was one of our oldest friends.

Margrethe: Heisenberg was german.

We were danes.

We were under german occupation.

It put us in a difficult position, certainly.

I've never seen you as angry with anyone

As you were with Heisenberg that night.

Not to disagree, but I believe I remained remarkably calm.

I know when you're angry.

It was as difficult for him as it was for us.

Margrethe: So why did he do it?

Bohr: I doubt if he ever really knew himself.

And he wasn't a friend...

Not after that visit.

That was the end of the famous friendship

Between Niels Bohr and Werner Heisenberg.

Heisenberg: Now we're all dead and gone, yes,

And there are only two things the world remembers about me.

One is the uncertainty principle,

The other is my mysterious visit to Niels Bohr in Copenhagen in 1941.

Everyone understands uncertainty, or thinks he does.

No one understands my trip to Copenhagen.

Time and time again I've explained it--

To Bohr himself and Margrethe;

To interrogators and intelligence officers;

To journalists and historians.

The more I've explained, the deeper the uncertainty has become.

Well, I shall be happy to make one more attempt.

Now we're all dead and gone.

Now no one can be hurt,

Now no one can be betrayed.

Margrethe: I never entirely liked him, you know.

Perhaps I can say that to you now.

Bohr: Yes, you did.

When he was first here in the '20s? Of course you did.

On the beach at tisvilde with us and the boys?

He was one of the family.

Something alien about him, even then.

Well, he was a very great physicist.

I never changed my mind about that.

They were all good-- all the people

Who came to Copenhagen to work with you.

You had most of the great pioneers in atomic theory here

At one time or another.

And the more I look back on it, the more I think

Heisenberg was the greatest of them all.

Heisenberg: So what was Bohr?

He was the first of us all,

The father of us all.

Modern atomic physics began when Bohr realized

That quantum theory applied to matter as well as to energy,

1913.

Everything we did was based on that great insight of his.

When you think that he first came here to work with me in 1924

And in just over a year he'd invented quantum mechanics...

It came out of his work with you.

Mostly out of what he'd been doing with max born

And pascual jordan at gottingen.

Another year or so and he'd got uncertainty.

And you'd done complementarity.

We argued them both out together.

Heisenberg: We did most of our best work together.

And we went on working together

Long after he ceased to be my assistant.

Heisenberg: Long after I'd left Copenhagen in 1927

And gone back to Germany.

Margrethe: Then the nazis came to power.

Then the war broke out and it became more and more difficult...

Until that day in 1941.

When it finished forever.

Yes... Why did he do it?

( train whistle toots )

( whistle toots )

( grinding, hissing )

Heisenberg: September, 1941, Copenhagen.

And at once here I am,

Getting off the night train from berlin.

Among all the field gray wehrmacht uniforms arriving with us.

All the naval gold braid,

All the well-tailored black of the ss.

Margrethe: He wants to see you?

I assume that's why he's come.

You're not really thinking of inviting him to the house?

That's obviously what he's hoping.

Niels, they've occupied our country!

He is not "they."

He is one of them.

First of all, there's an official visit to Bohr's workplace,

The institute for theoretical physics.

No doubt an awkward lunch in the old familiar canteen.

The lunch was a disaster.

He made a very bad impression.

Occupation of Denmark, "unfortunate."

Occupation of poland, however, "perfectly acceptable."

Germany now "certain to win the war."

Our tanks are almost at moscow.

What can stop us?

Well, one thing, perhaps... One thing.

He knows he's being watched, of course.

One must remember that. He has to be careful about what he says.

Or he won't be allowed to travel abroad again.

My love, the gestapo planted microphones in his house.

He told goudsmit when he was in america.

The ss brought him in for interrogation.

And then they let him go again.

Margrethe: I still think of him as a boy.

Bohr: He's nearly 40.

A middle-aged professor,

Fast catching up with the rest of us.

You still want to invite him here?

Let's add up the arguments

In a reasonably scientific way.

Firstly, Heisenberg is a friend.

Firstly, Heisenberg is a german.

"a white jew."

That's what the nazis called him.

He taught relativity and they said it was "jewish physics."

He couldn't mention Einstein by name,

But he stuck with relativity,

In spite of the most terrible attacks.

All the real jews have lost their jobs.

He's still teaching.

He's still teaching relativity.

Wouldn't leave Germany.

He wants to be there to rebuild german science when Hitler goes.

And if he is being watched it will all be reported upon--

Who he sees, what he says to them,

And what they say to him.

Heisenberg: I carry my surveillance around like an infectious disease.

But then I happen to know that Bohr is also under surveillance.

You know you're being watched yourself?

By the gestapo? I've nothing to hide.

By our fellow danes.

It would be the most terrible betrayal of all their trust in you

If they thought you were collaborating.

Inviting an old friend to dinner is hardly "collaborating."

It might appear to be collaborating.

Yes...

He's put us in a difficult position.

I shall never forgive him.

He must have good reason.

He must have very good reason.

- You won't talk about politics? - We'll stick to physics.

I assume it's physics he wants to talk to me about.

I think you must also assume that you and I

Aren't the only two people who hear what's being said in this house.

If you want to speak privately

You'd better go out into the open air.

I shan't want to speak privately.

You could go for another of your walks together.

I don't think we'll be going for any walks.

Whatever he has to say, he can say where everyone can hear it.

Some new idea he wants to try out on you, perhaps?

What can it be, though?

Where are we off to next?

So now of course your curiosity is aroused,

In spite of everything.

Heisenberg: So now here I am,

Walking out through the autumn light

To the bohrs' house at ny-carlsberg,

Followed, presumably, by my invisible shadow.

What am I feeling? Fear, certainly.

The touch of fear that one always feels for a teacher,

For an employer, for a parent.

Much worse fear about what I have to say,

About how to express it, how to broach it in the first place.

Worse fear still about what happens if I fail.

Margrethe: It's not something to do with the war?

Heisenberg is a theoretical physicist.

I don't think anyone has yet discovered a way

You can use theoretical physics to kill people.

It couldn't be something about fission?

Fission? Why would he want to talk to me about fission?

( sighs ) because you're working on it.

Heisenberg isn't.

Isn't he?

Everybody else in the world seems to be

And you're the acknowledged authority.

He hasn't published on fission.

It was Heisenberg who did all the original work

On the physics of the nucleus.

He consulted you then-- consulted you at every step.

That was back in 1932.

Fission's only been around for the last three years.

But if the germans were developing

Some kind of weapon based on nuclear fission--

My love, no one is going to develop a weapon based on nuclear fission.

But if they were trying to, then Heisenberg would be involved.

There's no shortage of good german physicists.

There's no shortage of good german physicists in america and britain.

The jews have gone, obviously.

So Heisenberg would be in charge of the work?

Margrethe, there is no work.

There's no way in the foreseeable future

In which fission can be used to produce any kind of weapon.

Then why is everyone still working on it?

Because there's an element of magic in it.

You fire a neutron at the nucleus of a uranium atom

And it splits into two different elements.

It's what the alchemists were trying to do--

To turn one element into another.

So why is he coming?

Heisenberg: I crunch over the familiar gravel

To the bohrs' front door, and tug at the familiar bell pull.

( bell rings )

What am I feeling?

Fear, yes.

And another sensation,

That's become painfully familiar over the past year.

A mixture of self-importance and sheer helpless absurdity

That of all the 2,000 million people in this world

I'm the one who's been charged with the impossible responsibility--

( gate clanks )

My dear Heisenberg!

My dear Bohr.

Come in, come in.

Thank you.

Margrethe: And of course, as soon as they catch sight of each other

All their caution disappears.

The old flames leap up from the ashes.

If we can just negotiate

All the treacherous little opening civilities...

I'm so touched you felt able to ask me.

We must try to go on behaving like human beings.

I do realize how awkward this is.

We scarcely had a chance to do more than shake hands at lunch.

And Margrethe I haven't seen since--

You were here four years ago.

Niels is right... You look older.

I had been hoping to see you both

In 1938, at the congress in warsaw.

I believe you had some personal trouble.

A little business in berlin.

In the prinzalbrecht-strasse with the ss?

- A slight misunderstanding. - We heard, yes. I'm so sorry.

These things happen.

The question is now resolved. Happily resolved.

We should all have met in zurich--

- In September 1939. - Only of course...

There was an unfortunate clash with the outbreak of war.

Sadly.

Sadly for us, certainly.

A lot more sadly still for many people.

- Heisenberg: Yes, indeed. - Bohr: Well, there it is.

- What can I say? - What can any of us say...

In the present circumstances?

No.

And your sons, they're...?

Are well, thank you. Elisabeth? The children?

Oh, very well. They send their love, of course.

Margrethe: They so much wanted to see each other,

In spite of everything.

But now the moment has come,

They're so busy avoiding each other's eye,

That they can scarcely see each other at all.

Heisenberg: I wonder if you realize... Quite how much it means to me

To be back here in Copenhagen, in this house.

I've been rather isolated over the past few years.

I can imagine.

Margrethe: Me, he scarcely notices.

I watch him discreetly from behind my expression of polite interest

As he struggles on.

Have things here been difficult?

Difficult?

Margrethe: Of course, he has to ask.

He has to get it out of the way.

"difficult"? What can I say?

We've not so far been treated to the gross abuses

That have occurred elsewhere.

The race laws have not been enforced.

Yet.

A few months ago they started deporting communists

And other anti-german elements.

- But you personally...? - Have been left strictly alone.

I've been anxious about you.

Kind of you.

No call for sleepless nights in leipzig so far, though.

Margrethe: Another silence.

He's done his duty.

Now he can begin to steer the conversation round

To pleasanter subjects.

- Are you still sailing? - Sailing?

Not a good start.

- No, no sailing. - The sound is...?

Mined.

Of course.

I assume he won't ask Niels if he has been skiing.

You've managed to get some skiing?

Skiing? In Denmark?

Norway. You-- you used to go to Norway.

I did, yes.

But since Norway is also...

Well...

Also occupied?

Yes, that might make it easier.

In fact I suppose we could now holiday almost anywhere in Europe.

I'm sorry. I hadn't thought of it quite in those terms.

Perhaps I'm being a little oversensitive.

Of course not. No, I should have thought.

He must almost be starting to wish he was back

In the prinzalbrecht-strasse with the ss.

I don't suppose you feel you could ever come to Germany?

Margrethe: The boy is an idiot.

My dear Heisenberg...

It would be an easy mistake to make

To think that the citizens of a small nation,

A small nation overrun--

Wantonly and cruelly overrun

By its more powerful neighbor--

Don't have exactly the same feelings

Of national pride as their conquerors...

Exactly the same love of their country.

Niels, we agreed.

To talk about physics, yes.

Not about politics.

- I'm sorry. - No, no...

I was simply going to say...

That I still have my old ski hut in bayrischzell.

So if by any chance...

At any time...

For any reason--

Perhaps Margrethe would be kind enough

To sew a yellow star on my ski jacket.

Yes, yes. Stupid of me.

Those first brief sparks have disappeared,

And the ashes have become very cold, indeed.

So now of course I'm starting to feel almost sorry for him.

He looks younger again,

Like the boy who first came here in 1924.

Younger than christian would have been now.

Shy and arrogant, and anxious to be loved.

Homesick and pleased to be away from home at last.

And, yes, it's sad...

Because Niels loved him.

He was like a father to him.

So-- what are you working on?

Fission, mostly. And you?

- Various things. - Margrethe: Fission?

Sometimes I'm very envious of your cyclotron.

Why? Are you working on fission yourself?

Heisenberg: There are over 30 in the United States.

Whereas in the whole of Germany--

Well...

"whereas in Germany"-- you were saying?

There is not one single cyclotron.

Bohr: You haven't come to borrow the cyclotron, have you?

That's not why you've come to Copenhagen?

No. That's not why I've come to Copenhagen.

I'm sorry. We mustn't jump to conclusions.

No, we must, none of us,

Jump to conclusions of any sort.

We must wait patiently to be told.

It's not always easy to explain things to the world at large.

I realize that we must always be conscious

Of the wider audience our words may have,

But the lack of cyclotrons in Germany is surely not a military secret.

I've no idea what's a secret and what isn't.

No secret either, about why there aren't any.

You can't say it, but I can. It's because the nazis

Have systematically undermined theoretical physics.

Why?

Because so many people working in the field were jews.

Margrethe: Physics, yes? Physics?

- This is physics. - It's also politics.

The two are sometimes painfully difficult to keep apart.

Are you in touch with any of our friends in England?

Born? Chadwick?

Heisenberg... We're under german occupation.

Germany's at war with britain.

I thought you might have contacts of some sort...

Or people in america? We're not at war with america.

Yet.

You've not heard from pauli in princeton? Goudsmit? Fermi?

What do you want to know?

I was simply... Curious.

You realize...

We both have good friends in the german embassy here...

Who are quite old-fashioned

In the way they use their influence.

They would certainly be trying to see

That distinguished local citizens were able to work undisturbed.

Are you telling me

That I'm being protected by your friends in the embassy?

What I'm saying is that...

You might find congenial company there.

I know people who would feel very honored

If you were able to accept the occasional invitation.

To cocktail parties in the german embassy?

Coffee and cakes with the nazi plenipotentiary?

Lectures, perhaps...

Discussion groups.

Social contacts of any sort

Could be... Helpful.

I'm sure they could.

Essential, perhaps, in certain circumstances.

- In what "circumstances"? - I think we both know.

Because I'm half jewish?

We all at one time or another may need the help of our friends.

Is this why you've come to Copenhagen?

To invite me to watch the deportation of my fellow danes

From a grandstand seat in the windows of the german embassy?

Bohr, please! Please!

What else can I do? How else can I help?

It's an impossibly difficult situation for you,

I understand that.

It's also an impossibly difficult situation for me.

( sighs )

( door creaks )

I'm sure you have the best of intentions.

Forget what I said.

- Unless-- - unless I need to remember it.

In any case, that's not why I've come.

Do you remember where we first met?

Of course. At gottingen in 1922.

At a lecture festival... Held in your honor.

It was a high honor. I was very conscious of it.

You were being honored for two reasons.

Firstly, because you were a great physicist.

- Yes, yes. - And secondly...

Because you were one of the few people in Europe

Who was prepared to have dealings with Germany.

The war had been over for four years,

We were still lepers. You held out your hand to us.

You bit it.

Bit it?

Bit my hand. You did.

I held it out in my most statesmanlike and reconciliatory way,

And you gave it a very nasty nip.

I did?

The first time I ever set eyes on you,

One of those lectures I was giving in gottingen.

- What are you talking about? - You stood up and laid into me.

- I offered a few comments. - Beautiful summer's day...

The scent of roses drifting in from the gardens.

Rows of eminent physicists and mathematicians,

All nodding approval of my benevolence and wisdom.

Suddenly up jumps a cheeky young pup

And tells me my mathematics are wrong.

They were wrong.

How old were you?

20.

( chuckles )

Margrethe: And Niels has suddenly decided to love him again,

In spite of everything.

Why? What happened?

Was it the recollection of that summer's day in gottingen?

Or everything? Or nothing at all?

Whatever it was, by the time we sat down to dinner,

The cold ashes have started into flame once again.

You were always so combative!

It was the same when we played table tennis at tisvilde.

Well, I wanted to win. Of course, I wanted to win. You wanted to win.

I wanted an agreeable game of table tennis.

You couldn't see the expression on your face.

I could see the expression on yours.

What about those games of poker, then, at the ski hut at bayrischzell?

You once cleaned us out, you remember that?

With a nonexistent straight!

We're all mathematicians. We're all counting cards.

We're all 90% certain he hasn't got anything.

But on he goes, raising us, and raising us.

This insane confidence.

Till our faith in mathematical probability

Begins to waver, and one by one we all throw in.

I thought I had a straight! I misread the cards. I bluffed myself!

( laughs ) poor Niels.

"poor Niels"? He won! He bankrupted us!

- You were insanely competitive! - Bohr: At bayrischzell...

We'd ski down from the hut to get provisions,

And he'd make even that into some kind of race!

Do you remember when we were there with weizsacker and someone?

You got out a stopwatch!

It took poor weizsacker 18 minutes.

- You were down there in 10, of course. - Eight!

- I don't recall how long I took. - 45.

Thank you.

Some rather swift skiing going on here, I think.

Heisenberg: Your skiing was like your science.

I mean, what were you waiting for? Me and weizsacker

To come back and give you a slight change of emphasis?

Probably.

You were doing 17 drafts of each slalom.

Bohr: At least I knew where I was. At the speed you were going,

You were up against the uncertainty relationship.

If you knew where you were when you were down,

You didn't know how fast you'd got there.

If you knew how fast you'd been going, you didn't know you were down.

The faster you ski, the sooner you're over cracks and crevasses.

The faster you ski, the better you think.

Not to disagree, but... That is most...

Most interesting.

( laughs )

By which he means, "it's nonsense."

But it's not nonsense. Decisions make themselves

When you're coming downhill at 70 kilometers an hour.

Suddenly, there is the edge of nothingness--

Swerve left or swerve right?

Or think about it and die?

( piano plays softly )

I've always been envious of the way you and Margrethe

Manage to talk to each other about everything--

Your work... Your problems... Me, no doubt.

I was formed by nature to be a mathematically curious entity.

Not one, but half of two.

Mathematics becomes very odd

When you apply it to people.

One and one can add up to so many different sums.

Heisenberg: Silence...

And of course they're thinking about their children again.

Margrethe: Silence.

What's he thinking about now?

His life...

Or ours?

Bohr: So many things we think about at the same time--

Our lives and our physics.

Margrethe: All the things that come into our heads out of nowhere.

Bohr: Our private consolations.

Our private agonies.

Margrethe: The same bright things... The same dark things.

Back and back they come.

Heisenberg: Their four children living,

And their two children dead.

Margrethe: Harald, lying alone in that boat.

Bohr: She's thinking about christian and harald.

Heisenberg: The two lost boys... Harald...

Bohr: All those years alone in that terrible ward.

Heisenberg: ...And christian.

The first born. The eldest son.

Bohr: And once again I see

Those same few moments that I see every day.

Heisenberg: Those short moments on the boat,

When the tiller slams over in the heavy sea...

And christian is falling.

Bohr: If I hadn't let him take the helm...

Heisenberg: Those long moments in the water.

Bohr: Those endless moments in the water.

About some things even we only think.

Margrethe: Because there's nothing to be said.

( piano music continues )

You suggested a stroll. We shan't be long.

- Heisenberg: A week at most. - Bohr: What?

Our great hike through zealand?

We went to elsinore.

I often think about what you said there.

You don't mind, my love? Half an hour.

- An hour, perhaps. - ( soft chuckle )

No, the whole appearance of elsinore, you said,

Was changed by our knowing that hamlet had lived there.

Every dark corner there reminds us...

Of the darkness inside the human soul.

Margrethe: So, they're walking again. He's done it.

Then if they're walking, they're talking.

Talking in a rather different way, no doubt.

I knew Niels would never hold out

If they could just get through the first few minutes...

If only out of curiosity. Now they're started,

An hour will mean two, of course, perhaps three.

The first thing they ever did was to go for a walk together.

At gottingen, after that lecture...

Niels immediately went to look for the presumptuous young man

Who'd queried his mathematics,

And swept him off for a tramp in the country.

Walk... Talk, make his acquaintance.

And when Heisenberg arrived here to work for him,

Off they go again on their great tour of zealand.

A lot of this century's physics they did in the open air,

Strolling around the forest paths at tisvilde.

Going down to the beach with the children,

Heisenberg holding christian's hand.

Yes...

And every evening in Copenhagen after dinner,

They'd walk around faelled park--

Walk and talk.

( door slams )

But this time...

Heisenberg wants to say goodbye. He's leaving.

Thank you for a delightful evening. Almost like old times.

It was kind of you.

Margrethe: You'll have some coffee? A glass of something?

I must prepare for my lecture.

But you'll come and see us again before you leave?

He has a great deal to do.

Forgive me if I've done or said anything...

Yes, yes.

Perhaps, when this war is over--

If we're all spared--

Goodbye.

( door echoes )

Politics?

Physics.

- What did he say? - Nothing.

I don't know. I was too angry to take it in.

Something about fission?

Margrethe: But what exactly had Heisenberg said?

That's what everyone wanted to know.

Then and forever after.

Bohr: That's what the british wanted to know

As soon as chadwick managed to get in touch with me--

"what exactly did Heisenberg say?"

Heisenberg: "and what exactly did Bohr reply?"

That was of course, the first thing

My colleagues asked me when I got back to Germany.

Margrethe: What did Heisenberg tell you?

What did you reply?

The one person who wanted to know was Heisenberg himself.

You mean when he came back to Copenhagen after the war, in 1947?

Bohr: I think he wanted various things.

Margrethe: Two things. Food parcels.

Bohr: For his family in Germany. They were on the verge of starvation.

Margrethe: And for you to agree on what you'd said to each other in 1941.

The conversation went wrong almost as fast as it did before.

You couldn't even agree where you'd walked that night.

Where we walked? Faelled park, of course.

Where we went so often in the old days.

Margrethe: No, no, not faelled park. That's behind the institute,

Four kilometers away from where we lived!

But I can see the street lamps next to the bandstand.

It was 1941-- no street lamps.

Bohr: I thought we hadn't got any further than my study.

I can see the drift of papers

Under the reading lamp on my desk.

It must have been outside.

What I was going to say was treasonable.

If I'd been overheard I would have been executed.

So what was this mysterious thing you said?

There's no mystery about it. There never was any mystery.

Heisenberg: I remember it absolutely clearly,

Because my life was at stake,

And I chose my words very carefully.

Does one, as a physicist...

Have the moral right

To work on the practical exploitation of atomic energy?

Bohr: The implication was obvious that you were working on it.

That I was trying to provide Hitler with nuclear weapons.

- Bohr: And you were! - No! A reactor!

That's what we were trying to build!

A machine to produce power, to generate electricity,

- To drive ships! - But then I asked you...

Do you actually think uranium fission

Can be used for the construction of weapons?

I now know that it can be.

Bohr: This is what really horrified me.

What happens in fission?

You fire a neutron at a uranium nucleus,

It splits, and it releases energy.

A huge amount of energy, yes?

About enough to move a speck of dust,

But it also releases two or three more neutrons.

Each of which has the chance of splitting another nucleus.

So then those two or three split nuclei

Each release energy in their turn?

And two or three more neutrons.

You start a trickle of snow sliding as your ski,

The trickle becomes a snowball.

An ever-widening chain of split nuclei

Forks through the uranium, doubling and quadrupling

In millionths of a second from one generation to the next.

The thunder of the gathering avalanche

Echoes from all the surrounding mountains.

Until eventually, after let's say 80 generations,

280 specks of dust have been moved.

Enough specks of dust to constitute a city,

And all who live in it.

But there is a catch.

There is a catch, thank god.

Natural uranium consists of two different isotopes, u238 and u235.

Less than 1% of it is u235, and this tiny fraction

Is the only part of it that's fissionable by fast neutrons.

What we'd realized, though...

That if we could once get the reactor going...

The u238 and the natural uranium would absorb the fast neutrons

And be transformed by them into a new element altogether.

Plutonium.

Plutonium.

Heisenberg: If we could build a reactor, we could build bombs.

That's what had brought me to Copenhagen.

But none of this could I say.

And at this point, you'd stopped listening.

The bomb had already gone off inside your head.

Bohr: Because I'd grasped the central point already.

One way or another, you saw the possibility

Of supplying Hitler with nuclear weapons.

You "grasped" at least four different central points,

All of them wrong.

You told rozental that I'd tried to pick your brains on fission.

You told weisskopf that I'd asked you

What you knew about the allied nuclear program.

Chadwick thought I was hoping to persuade you

There was no german program. But then it seems

You told some people that I'd tried to recruit you to work on it!

Very well, let's start all over again from the beginning.

No gestapo in the shadows this time. No british intelligence officer.

- No one watching us at all. - Only me.

Bohr: Only Margrethe.

We're going to make the whole thing clear to Margrethe.

You know how strongly I believe

That we don't do science for ourselves,

That we do it so we can explain to others--

- Heisenberg: In plain language. - In plain language.

Not your view, I know. You'd be happy to describe

What you were up to purely in differential equations

If you could, but for Margrethe's sake...

- In plain language. - Plain language.

Bohr: All right, so here we are, walking along once more.

And this time, I'm absolutely calm,

I'm listening intently.

- What is it you want to say? - It's not just what I want to say.

The whole german nuclear team in berlin,

They all wanted me to come and discuss it with you.

Go back to Germany, Heisenberg.

Gather your colleagues together in the laboratory.

Get up on a table and tell them... What?

Niels Bohr says that in his considered judgment,

Supplying a homicidal maniac

With an improved instrument of mass murder is...

What shall I say? An interesting idea.

No, not even an interesting idea.

A really rather seriously uninteresting idea.

What happens? You all fling down your geiger counters?

- Obviously not. - Because they'll arrest you.

My one hope is to remain in control.

So you don't want me to say yes, and you don't want me to say no.

What I want is for you to listen

Very carefully to what I'm going on to say next.

Very well. Here I am, listening most carefully as you tell me...

That nuclear weapons will require an enormous technical effort.

- True. - They will suck up huge resources.

- Huge resources. Certainly. - That sooner or later,

Governments will have to turn to scientists and ask them

Whether it's worth committing those resources,

Whether there is any hope

Of producing the weapons in time for them to be used.

Wait-- so they will have to turn to you and me.

We are the ones

Who will have to advise them whether to go ahead or not.

In the end,

The decision will be in our hands, whether we like it or not.

That's what you want to tell me?

That's what I want to tell you.

That's why you have come all this way with so much difficulty?

That's why you have thrown away nearly 20 years of friendship?

- Simply to tell me that? - Simply to tell you that.

But Heisenberg, this is more mysterious than ever.

What are you telling me it for?

What am I supposed to do about it?

The government of occupied Denmark isn't going to come to me

And ask me whether we should produce nuclear weapons.

No, but sooner or later,

If I manage to stay in control of our program,

The german government is going to come to me.

They are going to ask me whether to continue or not.

I will have to decide what to tell them.

Then you have an easy way out of your difficulties.

You tell them the same truth that you've just told me.

You tell them how difficult it will be.

And perhaps they'll be discouraged, perhaps they'll lose interest.

There was a report in a stockholm newspaper

That the americans are working on an atomic bomb.

Ah. Now it comes,

Now it comes. Now I understand everything.

You think I have contacts with the americans.

Well, you may. It's just conceivable.

If anybody in occupied Europe does, it will be you.

So you do want to know about the allied nuclear program.

I simply want to know if there is one.

Some hint. Some clue.

I've just betrayed my country and risked my life

To warn you of the german program.

And now I'm supposed to return the compliment?

Bohr, I have to know. I'm the one who has to decide.

If the allies are building a bomb, what am I choosing for my country?

Germany is where I was born.

Germany is where I became what I am.

Germany is all the faces of my childhood,

All the hands that picked me up when I fell,

All the voices that encouraged me, that set me on my way,

All the hearts that speak to my heart.

Germany is my widowed mother,

My impossible brother, my wife! Germany is our children!

I have to know what I'm deciding for them!

Another defeat?

Another nightmare like the nightmare I grew up with?

Bohr, my childhood ended in anarchy and civil war.

Are more children going to starve as we did?

But my dear Heisenberg, there's nothing I can tell you.

I've no idea whether there's an allied nuclear program.

Heisenberg: But that allied nuclear program

Is just getting underway even as we're talking.

And the bomb they're building is to be used on us.

On the evening of Hiroshima, oppenheimer said

It was his one regret

That they hadn't produced the bomb in time to use on Germany.

He tormented himself afterwards.

Afterwards, yes. At least we tormented ourselves beforehand.

Did a single one of them stop to think

Even for a brief moment about what they were doing?

Did you when you went to los alamos?

My dear good Heisenberg, we weren't supplying the bomb to Hitler.

You weren't dropping it on Hitler, either.

You were dropping it on anyone within reach--

On old men and women in the street-- on mothers and their children--

And if you had produced it in time,

They would have been my fellow countrymen,

My wife, my children. That was the intention, yes?

That was the intention.

You never had the slightest conception

Of what happens when bombs are dropped on cities.

Even conventional bombs. None of you ever experienced it.

You know why allied scientists worked on the bomb?

Of course. Fear.

The same fear that consumed you,

Because they were afraid that you were working on it.

But Bohr, you could have told them.

- Told them what? - What I told you in 1941...

That the choice is in our hands-- mine and oppenheimer's.

That if I can tell them the simple truth when they ask me,

The simple discouraging truth, so can he.

This is what you wanted from me?

Not to tell you what the americans were doing, but to stop them?

To tell them we can stop it together.

I had no contact with the americans.

You did with the british.

Only later.

The gestapo intercepted the message you sent them about our meeting.

- And passed it to you? - Why not?

They began to trust me. That's what gave me the opportunity

Of remaining in control of events.

Not to criticize, Heisenberg,

But if this was your plan in coming to Copenhagen,

It's-- what can I say?

It's most interesting.

It wasn't a plan, it was a hope. Not even a hope--

A microscopically fine thread of possibility.

A wild improbability.

Worth trying though, Bohr. Worth trying, surely.

But already you were too angry to understand what I was saying.

No, why he was angry was because he was beginning to understand.

The germans drive out most of their best physicists

Because they're jews; america and britain give them sanctuary.

Now it seems that this might offer the allies a hope of salvation.

And at once you came howling here to Niels,

Begging him to persuade them to give it up.

Margrethe, my love, perhaps we should express ourselves a little more temperately.

But the gall of it. The sheer, breathtaking gall of it.

Bold skiing, I have to say.

But, Bohr,

We weren't skiing then.

I refused to believe it when I first heard the news of Hiroshima.

I thought it was just one of those

Strange dreams we were living in at the time--

But you'd done it. You'd built the bomb.

- Bohr: Yes. - And used it on a living target.

- On a living target. - You're not suggesting

That Niels did anything wrong by working at los alamos?

- Of course not. - The decision had been taken

Long before Niels arrived.

The bomb would have been built whether he'd gone or not.

In any case, my part was very small.

Oppenheimer described you as the team's "father-confessor."

It seemed to be my role in life.

He said you made "a great contribution."

Spiritual, possibly, not practical.

Fermi said it was you worked out how to trigger the Nagasaki bomb.

I put forward an idea.

You're not implying that there's anything

That Niels needs to explain or defend?

No one has ever expected him to explain or defend anything.

He is a profoundly good man.

It's not a question of goodness, I was spared the decision.

Yes, and I was not.

So, explaining and defending myself

Was how I spent the last 30 years of my life.

When I went to america in 1949,

A lot of the physicists wouldn't even shake my hand.

Hands that had actually built the bomb wouldn't touch mine.

Let me tell you, if you think you're making yourself

Any clearer to me now, you're not.

Margrethe, I understand his feelings.

I don't. I'm as angry as you were before.

It's so easy to make you feel conscience-stricken.

Why should he transfer his burden to you?

Because what does he do after his great consultation with you?

He goes back to berlin and tells the nazis

That he can produce atomic bombs.

But what I stress is the difficulty in separating 235.

You tell them about plutonium?

I tell some of the minor officials.

I have to keep people's hopes alive.

And you ask albert speer for the funding to continue?

To continue with the reactor? Of course I do.

But I ask him for so little that he doesn't take the program seriously.

Do you tell him the reactor will produce plutonium?

I don't tell him the reactor will produce plutonium, not speer,

No, I don't tell him the reactor will produce plutonium.

A striking omission, I have to admit.

And what happens? It works.

He gives us barely enough money

To keep the reactor program ticking over

And that is the end

Of the german atomic bomb. That is the end of it.

You go on with the reactor, though.

We go on with the reactor, of course, because now

There's no risk of getting it running in time

To produce enough plutonium for a bomb.

No, we go on with the reactor, all right.

I keep that program going. I keep it under my control, till the bitter end.

Everything was still under your control?

Under my control, yes, that's the point. Under my control!

Nothing was under anyone's control by that time.

Perrin examined it after the allied troops took over.

They said it had no cadmium control rods.

There was nothing to absorb any excessive neutrons

To slow down the reaction when it overheated.

You were no longer running that program, Heisenberg,

- The program was running you. - But we were almost there.

Two more weeks. Two more blocks of uranium,

And it would have been german physics that achieved

The world's first self-sustaining chain reaction.

Except that fermi had already done it in chicago,

Two years earlier.

But we didn't know that.

You didn't know anything.

Perrin said there wasn't even anything

To protect you all from the radiation.

We didn't have time to think about it.

So if it had gone critical--

Margrethe: You'd have all died of radiation sickness.

My dear Heisenberg.

My dear boy.

Yes, but by then the reactor would've been running.

I should've been there to look after you.

That's all we could think about at the time--

To get the reactor running. To get the reactor running.

You always needed me there to slow you down a little.

If I had died then, what should I have missed?

30 years of attempting to explain.

30 years of reproach and hostility.

Even you turned your back on me.

Look at him, he's lost.

He is like a lost child.

So, Heisenberg, why did you come to Copenhagen in 1941?

It was right that you told us about all the fears you had.

But you didn't really think I'd tell you whether

The americans were working on a bomb?

No.

You didn't seriously hope that I'd stop them?

No.

You were going back to work on that reactor whatever I said.

Yes.

So, Heisenberg... Why did you come?

Why did I come?

Tell us once again-- another draft of the paper--

And this time, we shall get it right.

This time, we shall understand.

You might even understand yourself.

Why did I come?

And once again, I go through that evening in 1941.

I crunch over the familiar gravel, and tug at the familiar bell pull.

( bell rings )

What's in my head? Fear, certainly...

And the absurd and horrible importance

Of someone bearing bad news.

But yes...

Something else as well.

Here it comes again-- I can almost see its face--

Something good, something bright and eager and hopeful.

( gate clanks )

- Bohr: I open the door... - Heisenberg: And there he is...

I see his eyes light up at the sight of me.

Bohr: He's smiling his wary "schoolboy" smile.

Heisenberg: And I feel a moment of such consolation...

Bohr: A flash from such pure gladness...

Heisenberg: ...As if I'd come home after a long journey,

Bohr: ...As if a long-lost child had appeared on the doorstep.

Margrethe: Look at them-- father and son, still-- just for a moment.

Bohr: For a moment, yes, it's the '20s again...

Heidelberg: ...And we shall speak to each other and understand each other

- In the way we did before. - Bohr: My dear Heisenberg!

- My dear Bohr. - Come in, come in.

Heisenberg: It was the very beginning of spring--

The first time I came to Copenhagen, in 1924, March,

Raw, blustery northern weather--

But every now and then, the sun would come out

And leave that first marvelous warmth of the year on your skin,

That first breath of returning life.

What did we do?

Put on our boots and rucksacks--

Took the tram to the end of the line.

- Start walking-- - northwards to elsinore.

- If you walk, you talk. - Walking, talking...

For a hundred miles.

Bohr: After which, we talked more or less nonstop

For the next three years.

Those years? Those amazing years.

- Those three short years. - Bohr: From 1924 to 1927.

From when I arrived in Copenhagen to work with you--

To when you departed to take up your chair in leipzig.

Three years of raw, bracing northern springtime.

At the end of which, we had quantum mechanics,

- We had uncertainty-- - we had complementarity--

--We had the whole Copenhagen interpretation.

Europe in all its glory again. A new enlightenment,

With Germany back in its rightful place at the heart of it.

And who led the way for everyone else?

You and Niels.

- Well, we did. - We did.

And that's what you're trying to get back?

To something we did in those three years-- something we thought.

I keep almost seeing it out of the corner of my eye

While we're talking. Something in the way we worked,

Something in the way we did all those things.

- Together. - Together, yes. Together.

Margrethe: No.

No? What do you mean, no?

Not together.

You didn't do any of those things together.

Yes, we did. Of course we did.

No, no you didn't.

Every single one of them you did when you were apart.

You first worked out quantum mechanics on heligoland.

I remember the evening

When the mathematics first began to chime with the principle--

- On heligoland. - --On heligoland.

On your own.

On my own. And I was happy?

Happier than when you came back to us all in Copenhagen

The following winter.

With all that schrodinger nonsense?

Nonsense? Come, come-- schrodinger's wave formulation?

Yes, and suddenly everyone all turned their backs

On your wonderful new matrix mechanics.

Heisenberg: They couldn't understand it.

They could understand schrodinger's wave mechanics.

Because they'd learned it in school.

Well, you described it as "repulsive."

Schrodinger said my mathematics were "repulsive."

They simply thought you were jealous.

You'd gone mad by this time. You'd become fanatical.

You were refusing to allow wave theory

Any place in quantum mechanics at all.

- You'd completely turned your coat. - I said that wave mechanics

And matrix mechanics were simply alternative tools.

Something you were always accusing me of.

"if it works, it works. Never mind what it means."

- Of course I mind what it means. - What it means in language.

- In plain language, yes. - What something means

Is what it means in mathematics.

You think that so long as the mathematics works out,

- The sense doesn't matter. - Sense is mathematics!

That's what sense is!

Yes, you are far better apart, you two.

You actually love the paradoxes, I mean, that's your problem.

You revel in the contradictions.

Yes and you've never been able to understand the suggestiveness

Of paradox and contradiction. That's your problem.

Having him out of town was as liberating

As getting away from my hay fever in heligoland.

I actually started to think at last.

I wouldn't let you even sit anywhere near each other,

- If I were the teacher. - And that's when I did it.

That's when I did uncertainty.

Walking round faelled park at night on my own.

Oh--!

It's very late, and as soon as I've turned off into the park

I'm completely alone in the darkness.

I start to think about what you'd see

If you could train a telescope on me from the mountains of Norway.

You'd see me by the street lamps on the blegdamsvej...

Then nothing as I vanished into the darkness...

Then another glimpse of me as I passed the lamppost

In front of the bandstand, then nothing again.

And that's what we see in the cloud chamber.

Not a continuous track, but a series of glimpses--

A series of collisions between the passing electron

And various molecules of water vapor.

I don't know why we hadn't thought of it before,

Except that we were too busy arguing to think at all.

You seemed to have given up on all forms of discussion.

By the time I get back from Norway, I find

You've done a draft of your "uncertainty" paper

And you've already sent it for publication.

And an even worse battle begins.

My dear good Heisenberg, it was not open behavior

To rush a first draft into print before we've discussed it together.

It was not the way we worked.

No, "the way we worked" was that you hounded me

From first thing in the morning till last thing at night.

The "way we worked" is you drove me mad.

Yes, because the paper contained a fundamental error!

Here we go again.

I show him one of the strangest truths about the universe

That any of us has stumbled across since relativity--

That you can never know everything about the whereabouts of a partic,

Or anything else-- even Bohr now, as he prowls up and down the room

In that maddening way of his--

Because we can't observe it without introducing

Some new element into the situation--

A molecule of water vapor for it to hit,

A piece of light-- things which have an energy of their own,

Which therefore have an effect on that they hit.

I shatter the objective universe around you, and all you can say is,

"there's an error in the formulation!"

There was!

Listen-- in my paper,

What we were trying to locate is not a free electron

Off on its travels through a cloud chamber,

But an electron when it's at home,

Moving around inside an atom.

And the uncertainty arises, not, as you claim, through

Its indeterminate recoil when it's hit by an incoming photon--

- Plain language, plain language. - This is plain language.

- Listen-- - the language of classical mechanics.

Listen-- Copenhagen is an atom... Margrethe is its nucleus.

It's about the right scale, 10,000 to 1?

- Yes, yes... - Now, Bohr is an electron.

He is wandering about the city...

Somewhere in the darkness.

No one knows where.

He's here, he's there, he's everywhere and nowhere.

Up at faelled park,

Down at new carlsberg, passing city hall,

Out by the harbor.

I am a photon-- a quantum of light.

I have been dispatched...

Into the darkness...

To find Bohr.

And I succeed. Why?

Because I've managed to collide with him.

But look-- what's happened?

He's slowed down-- he's been deflected.

He's no longer doing exactly what he was so maddeningly doing

When I walked into him.

But, Heisenberg, Heisenberg-- you also have been deflected.

If people can see what's happened to you-- to their "piece of light"--

Then they can work out what must have happened to me.

The trouble is knowing what's happened to you.

You see what we did in those three years, Heisenberg?

Not to exaggerate, but we turned the world inside out.

Yes, listen. Now it comes, now it comes.

We put man back at the center of the universe.

Throughout history, we keep finding ourselves displaced.

We keep exiling ourselves to the periphery of things.

First, we turn ourselves

Into a mere adjunct of god's unknowable purposes--

Tiny figures kneeling in the great cathedral of creation.

And no sooner have we recovered ourselves in the renaissance,

No sooner has man become, as protagoras proclaimed him,

"the measure of all things,"

Than we're pushed aside again,

By the products of our own reasoning.

We're dwarfed again

As physicists build the great new cathedrals for us to wonder at--

The laws of classical mechanics

That exist whether we exist or not.

And then we come to the beginning of the 20th century...

And we're suddenly forced to rise from our knees again.

It starts with Einstein.

It starts with Einstein.

He shows that measurement--

Measurement on which the whole possibility of science depends--

Measurement is not an impersonal event

That occurs with impartial universality.

It's a human act...

Carried out from a specific point of view in time and space,

From the one particular viewpoint of a possible observer.

And then...

Here in Copenhagen in the mid '20s,

We discover that there is no precisely determinable objective universe.

That the universe exists

Only as a series of approximations,

Only within the limits determined

By our relationship with it...

Only through the understanding lodged inside the human head.

Margrethe: If it's Heisenberg at the center of the universe,

Then the one bit of the universe he can't see is Heisenberg.

Forgive me, but you don't even know

Why you did uncertainty in the first place.

And I'm sorry, but you want to make everything

Seem so heroically abstract and logical.

I look around me and what I see isn't a story.

I see confusion and rage and tears and jealousy

And no one knowing what things mean or which way they're going to go.

All the same, it works, it works.

Oh yes, it works. It works wonderfully.

Within three months of publishing your "uncertainty" paper

You're offered the chair at leipzig.

I didn't mean that.

And if you want to know why you've come here to Copenhagen,

I'll tell you that as well.

You're right, there's no great mystery about it.

You've come to show yourself off to us.

Bohr: Margrethe...

When he first came in 1924, he was a humble assistant lecturer

From a humiliated nation, grateful to have a job.

Now he's here, back in triumph--

The leading scientist in a nation that's conquered most of Europe.

He's come to show us how well he's done in life.

This is so unlike you.

I'm sorry, I'm sorry, but isn't that really why he's here?

Because he's burning to let us know that he's in charge

Of some vital piece of secret research?

And that even so...

He's preserved a lofty moral independence.

Preserved it so famously

That he's being watched by the gestapo.

Preserved it so successfully

That he's now also got a wonderfully important moral dilemma to face.

Yes, well, now you're simply working yourself up.

A chain reaction?

You tell one painful truth and it leads to two more.

And as you frankly admit, you're going back to continue

Doing precisely what you were doing before, whatever Niels tells you.

Yes.

Because you wouldn't dream of giving up

Such a wonderful opportunity for research.

Not if I can possibly help it.

Also you want to demonstrate to the nazis

How useful theoretical physics can be.

You want to save the honor of german science.

You want to be there to reestablish it in all its glory

As soon as the war is over.

All the same, I won't tell speer that the reactor--

Will produce plutonium? No.

Because you're afraid of what will happen

If the nazis commit huge resources,

And you fail to deliver the bombs.

Please, don't try and tell us that you're a hero of the resistance.

I never said I was a hero.

Your talent is for skiing too fast

For anyone to see where you are;

For always being in more than one position at a time...

Like one of your particles.

I can only say that it worked.

Unlike most of the gestures

Made by the heroes of the resistance, it worked.

Oh, I know what you're thinking.

I should have joined the plot against Hitler

And got myself hanged like the others.

- Bohr: Of course not. - You don't say it,

Because there are things that can't be said, but you think it.

- No. - Heisenberg: What would it have achieved?

Really, it is ridiculous.

You reasoned your way, both of you,

With astonishing delicacy and precision

Into the tiny world of the atom.

And now it turns out that everything depends

On these really rather large objects on your shoulders.

And what's going on there is--

Elsinore.

Elsinore...

Yes.

And maybe you're right--

I was afraid of what might happen.

I was conscious of being on the winning side.

Why didn't you kill me?

- Why didn't I--? - Kill me... That night in 1941.

My dear Heisenberg, the suggestion is of course--

"most interesting."

So interesting in fact, it didn't even occur to you.

Complementarity, once again.

I'm your enemy. I'm also your friend.

I'm a danger to mankind, I'm also your guest.

I'm a particle, I'm also a wave.

We have one set of obligations to the world in general,

And other sets, never to be reconciled

To our fellow countrymen, to our neighbors, to our family,

To our friends, to our children.

All we can do is to look afterwards, and see what happened.

I'll tell you another reason why you did uncertainty--

You have a natural affinity for it.

Well, I must have cut a gratifyingly chastened figure

When I returned in 1947,

Crawling on my hands and knees, my nation back in ruin.

Not really.

Once more you demonstrated how you personally came out on top.

Enough, my love, enough.

No.

I've kept my thoughts to myself for all these years,

But it's so maddening having this "clever son"

Forever dancing about in front of one's eyes,

Forever demanding our approval,

Forever struggling to shock us,

Forever begging to be told what the limits to his freedom are,

If only so he can go out to transgress them.

I'm sorry, but really--

On your "hands and knees"?

It was my good, dear, kind husband

Who was on his hands and knees-- literally.

Crawling down to the beach in the darkness in 1943...

Fleeing like a thief in the night

From his homeland to escape being murdered.

I warned you in 1941, but you wouldn't listen.

At least Bohr got across to sweden.

And where were you?

I can only say I didn't do it. I didn't build the bomb.

No, and why didn't you?

I'll tell you that as well. Because you couldn't.

You didn't understand the physics.

I understood very clearly. I simply didn't tell the others.

- Ah... - I understood, though.

But-- secretly.

You can look it up if you don't believe me.

There's evidence for once?

It was all most carefully recorded.

- Witnesses, even? - Unimpeachable witnesses.

Who wrote it down?

Who recorded it and transcribed it.

Even though you "didn't tell anyone"?

I told one person.

I told Otto Hahn that terrible night

After we heard the news of Hiroshima.

Somewhere in the small hours, I gave him

A reasonably good account of how the bomb had worked.

After the event?

After the event. Yes. When it didn't matter anymore.

The critical mass. That was the most important thing.

The amount of material you needed to establish the chain reaction.

Did you tell him the critical mass?

I gave him a figure, yes.

You can look it up.

We were all rounded up by the british,

The whole team, everyone who worked on atomic science,

And we were spirited away to farm hall in huntingdonshire.

Hahn asked me when we first arrived

Whether I thought there were any hidden microphones.

I laughed. I said the british were far too old-fashioned

To know any gestapo methods.

I underestimated them. They had microphones everywhere.

They recorded everything. So look it up.

But the critical mass. You gave him a figure.

What was the figure you gave him?

- I forget. - Heisenberg--

It's on the record. You can see for yourself.

The figure for the Hiroshima bomb was--

50 kilograms.

So that was the figure you gave Hahn? 50 kilograms?

I said about a ton.

"about a ton"?

A thousand kilograms?

Heisenberg, I believe I am at last, beginning to understand something.

One thing I was wrong about.

You were 20 times over.

The one thing.

But Heisenberg, your mathematics,

Your mathematics-- how could they have been so far out?

They weren't.

As soon as I calculated the diffusion

- I got it just about right. - As soon as you calculated it?

I gave everybody a seminar on it a week later.

It's in the record. Look it up.

You mean you hadn't calculated it before?

There was no need. It already been done.

For natural uranium.

You needed to calculate the figure for pure 235.

- Obviously. - And you didn't?

I didn't.

Oh, all your agonizing in Copenhagen

About plutonium was beside the point.

You could have done it without ever building the reactor.

You could have done it with 235 all the time.

Almost certainly not.

- Just possibly, though. - Just possibly.

And that question was settled

Long before you arrived in Copenhagen...

Simply by failing to try the diffusion equation.

Such a tiny failure.

But the consequences kept branching out over the years,

Doubling and redoubling--

Until they were large enough to save a city.

Which city?

Any of the cities that we never dropped our bomb on.

London, presumably, if you'd had it in time.

If the americans had already entered the war,

And the allies had begun to liberate Europe, then--

Who knows? Paris as well.

Amsterdam. Perhaps Copenhagen.

So, Heisenberg, tell us this one simple thing--

Why didn't you do the calculation?

I don't know.

I don't know why I didn't do it.

Because I never thought of it.

Because it didn't occur to me.

Because I assumed it wasn't worth doing.

"assumed"?

Assumed?

You never assumed anything.

That's how you got uncertainty--

Because you rejected our assumptions.

You calculated, Heisenberg. You calculated everything.

The first thing you did with a problem was the mathematics.

You should have been there to slow me down.

Yes...

You wouldn't have got away with it if I'd been standing over you.

Though in fact, you made exactly the same assumption.

You thought there was no danger for exactly the same reasons as I did.

Why didn't you calculate it?

Why didn't I calculate it?

Tell us why you didn't calculate it and we'll know why I didn't.

It's obvious why I didn't.

Well, go on.

Because he wasn't trying to build a bomb.

Yes. Thank you.

Because he wasn't trying to build a bomb.

I imagine it was the same for me,

Because I wasn't trying to build a bomb. Thank you.

Bohr: So you bluffed yourself,

Like I did at poker with the straight I never had.

But in that case...

Why did I come to Copenhagen? Yes.

Why did I come?

One more draft, yes? One final draft.

And once again I crunch over the familiar gravel

To the bohrs' front door, and tug at the familiar bell pull.

( bell rings )

Why have I come?

I know perfectly well.

Know so well that I've no need to ask myself.

Till once again, the heavy front door opens.

Bohr: He stands on the doorstep.

Until this instant, his thoughts have been everywhere and nowhere

Like unobserved particles through all the slits and the diffraction

Grating simultaneously.

Now, they have to be observed and specified.

- My dear Heisenberg! - My dear Bohr!

Heisenberg: And at once the clear purposes inside my head

Lose all definite shape.

The light falls on them and they scatter.

How difficult it is to see even what's in front of one's eyes.

All we possess is the present,

And the present endlessly dissolves into the past.

Bohr has gone, even as I turn to see Margrethe.

Niels is right. You look older.

Bohr: I believe you had some personal trouble.

Margrethe slips into history even as I turn back to Bohr.

To catch the slightest glimpse of what's behind one's eyes.

Here I am at the center of the universe,

And yet all I can see are two smiles that don't belong to me.

- Elisabeth? The children? - Oh, very well.

They-- they send their love, of course.

I can feel a third smile in the room, very close to me.

Could it be the one I suddenly see for a moment in the mirror there?

And is the awkward stranger wearing it in any way connected

With this presence that I can feel in the room?

This all-enveloping, unobserved presence?

Margrethe: I watch the two smiles in the room--

One awkward and ingratiating,

The other rapidly fading from incautious warmth to bare politeness.

There's also a third smile in the room I know,

Unchangingly courteous, I hope,

And unchangingly guarded.

You've managed to get some skiing?

Bohr: I glance at Margrethe,

And for a moment I see what she can see and I can't--

Myself-- and the smile vanishing from my face as poor Heisenberg blunders on.

Heisenberg: I look at the two of them looking at me,

And for a moment I see the third person in the room

As clearly as I see them.

Their importunate guest, stumbling

From one crass and unwelcome thoughtlessness to the next.

Bohr: I look at him looking at me,

Anxiously, pleadingly urging me back to the old days,

And I see what he sees.

And yes, now it comes, now it comes.

There's someone missing from the room.

He sees me. He sees Margrethe.

He doesn't see himself.

( plays softly )

You suggested a stroll. We shan't be long.

- Heisenberg: A week at most. - Bohr: What?

Our great hike through zealand?

You remember elsinore? "the darkness inside the human soul"?

Bohr: And out we go. Out under the autumn trees.

Heisenberg: Now there's no one in the world

Except Bohr and the invisible other.

Who is he, this all-enveloping presence in the darkness?

Margrethe: The flying particle wanders the darkness...

No one knows where.

It's here, it's there,

It's everywhere and nowhere.

Bohr: With careful casualness

He begins to ask the question he's prepared.

Does one, as a physicist, have the moral right

To work on the practical exploitation of atomic energy?

Margrethe: The great collision.

Bohr: I stop, he stops.

Margrethe: This is how they work.

Heisenberg: He gazes at me, horrified.

Margrethe: Now at last, he knows where he is

And what he's doing.

And even as the moment of collision begins, it's over.

Heisenberg: He turns away.

Bohr: Already I'm hurrying back towards the house.

Margrethe: Already they're both flying away from each other

Into the darkness again.

Heisenberg: Our conversation's over.

Bohr: Our great partnership.

Heisenberg: All our friendship.

Margrethe: And everything about him

Becomes as uncertain as it was before.

Bohr: Unless...

Yes, a thought experiment.

Let's suppose for a moment

I don't go flying off into the night.

Let's see what happens if instead...

I remember the paternal role I'm supposed to play.

If I stop and control my anger...

( brief sigh )

...And turn back to you, and ask you...

- Why? - Why?

Why are you confident that it's going to be so reassuringly difficult

To build a bomb with 235?

Is it because you've done the calculation?

- The calculation--? - Of the diffusion in 235.

No, it's because you haven't calculated it.

You haven't considered calculating it.

You haven't consciously realized

There was a calculation to be made.

Heisenberg: And of course, now I have realized--

In fact it wouldn't be all that difficult.

Let's see... The scattering cross-section's about 6 x 10-24,

So the mean free path would be-- hold on.

Bohr: And suddenly a very different

And very terrible new world begins to take shape.

That was the last and greatest demand

That Heisenberg made on his friendship with you--

To be understood... When he couldn't understand himself.

And that was the last and greatest act of friendship for Heisenberg

That you performed in return--

To leave him misunderstood.

Yes.

Perhaps I should thank you.

Perhaps you should.

Anyway, it was the end of the story.

Though perhaps there was also something I should thank you for--

That summer night in 1943,

When I escaped across the sound in the fishing boat,

And the german freighters arrived--

What's that to do with Heisenberg?

When the ships arrived on the Wednesday,

There were 8,000 jews in Denmark to be arrested and crammed into their holds.

The following day, on the eve of the jewish new year,

When the ss began their roundup,

There was scarcely a jew to be found.

For a handful of us in one fishing smack

To get past the german patrol boats was remarkable enough.

For a whole armada to get past,

With the best part of 8,000 people on board,

Was... Like the red sea parting.

So perhaps I should thank you.

For what?

My life.

All our lives.

Nothing to do with me by that time,

I regret to say.

But after I'd gone, you came back to Copenhagen.

To make sure our people didn't take over the institute in your absence.

I never thanked you for that, either.

You know they offered me your cyclotron?

You could have separated a little 235 with it.

Meanwhile, you were going on from sweden to los alamos.

Bohr: To play my small but helpful part

In the deaths of a hundred thousand people.

Margrethe: Niels, you did nothing wrong.

- Didn't I? - Heisenberg: Of course not.

You were a good man from first to last,

And no one could ever say otherwise.

Whereas I--

Whereas you, my dear Heisenberg,

Never managed to contribute to the death

Of one single solitary person in all your life.

Bohr: Before we can lay our hands on anything, our life's over.

Heisenberg: Before we can glimpse who or what we are,

We're gone and laid to dust.

Bohr: Settled among all the dust we raised.

Margrethe: And sooner or later there will come a time

When all our children are laid to dust,

And all our children's children.

Bohr: When no more decisions, great or small, are ever made again.

When there's no more uncertainty,

Because there's no more knowledge.

Margrethe: And when all our eyes are closed,

When even the ghosts have gone,

What will be left of our beloved world?

Our ruined and dishonored and beloved world?

Heisenberg: But in the meanwhile,

In this most precious meanwhile,

There it is. The trees in faelled park.

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.

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Announcer: This is pbs.

This play isn't an attempt

To come to any final judgment of Heisenberg.

He was in a very, very difficult situation

As a physicist in a totalitarian country.

Heisenberg didn't present himself as a hero.

He undoubtedly did make compromises with the nazi regime,

And I'm sure he made them for mixed motives--

Some of them which I think were undoubtedly honorable.

And I'm very taken aback by people living now

Who had no experience of living in nazi Germany

Who rush to judgment on Heisenberg.

( classical piano solo plays )

( barbara blum speaking )

( music continues )

( barbara blum speaking )

I think he felt very much that he had lost a friend.

Erik rudinger: It was an occupied country

And here comes a person from the occupier.

And I think that was very naive of Heisenberg--

To think that they could just talk like old friends

Under those circumstances.

I think he was-- there was some psychological deficiency

That he wasn't aware of how Bohr would feel

When he came as-- formally

As a representative of the occupier.

Frayn: Various people have speculated

That Heisenberg was trying to find out

About the allied atomic program--

Indeed, that he was sent by the german government--

And I think that's quite possible.

What I cannot believe

Is that anyone in the german government

Ever authorized Heisenberg

To go to Copenhagen and say to Niels Bohr--

Who was known to be in touch with western scientists--

To say to him that there was this highly secret program

Running in Germany to produce atomic weapons.

That, Heisenberg must have done off his own bat.

And to me it suggests that at the very least

That he hoped that Bohr would pass on the news to the allies

That there was an atomic bomb program in Germany.

And I think it just possibly gives some color

To Heisenberg's own account of the meeting,

His own explanation of the meeting--

That he hoped that Bohr would persuade allied scientists

To be as discouraging to their governments

About nuclear weapons

As the german physicists were being to the german government.

Now of course, I knew that Bohr was a dane

And Denmark was occupied by german troops,

So it was obvious that Bohr would have very strong feelings in this matter.

At the same time, I felt that Bohr and I were good friends

And he knew my attitude to problems of this kind from earlier years,

So I felt that still this would be

A good basis for confidence and for conversation on this problem.

Frayn: Everyone since the war

Has had suspicions about Werner Heisenberg.

I have to say as a young man,

He was thought to be very straightforward

And very open and very charming man and everyone liked him.

But he certainly seems to have changed during the nazi period.

He does seem to have become much more closed up as life went on.

And he certainly felt he had been misunderstood,

And not surprisingly, he was much attacked after the second world war

And people still have

Passionately vituperative feelings about him.

In fact, Margrethe, Niels Bohr's wife, was particularly angry

About all his attempts to exculpate himself.

Margrethe was offended

By his coming in 1941, and afterwards said,

"whatever anyone says about that meeting, it was a hostile one."

When I wrote the play,

Heisenberg had commented publicly on the meeting

And said what he thought had happened. But Niels Bohr hadn't.

What I didn't know

Was that Bohr had written an account of the meeting

In a very angry letter to Heisenberg long after the war

In which he put his version of the meeting.

However, absolutely characteristically, he didn't send the letter.

He started to redraft it.

He was trying to dissent very strongly from Heisenberg

Without hurting Heisenberg's feelings because he was a very kindly man.

And he never sent the letter. He went on redrafting it until he died.

His family found all these drafts of the letter among his papers

And decided not to publish them

But to put them in the Niels Bohr archive in Copenhagen

And to embargo them until 50 years after his death.

One of the ideas that Heisenberg and Bohr introduced into physics

Is that the act of observation affects what you're observing.

And curiously, the production of the play

Has had a somewhat similar effect on the subject.

It has persuaded the Bohr family

To release the letter

And indeed, all the various drafts of the letter early.

"I think that I owe it to you to tell you

That I am greatly amazed

To see how much your memory has deceived you.

You spoke in a manner

That could only give me the firm impression that under your leadership

Everything was being done in Germany to develop atomic weapons.

A great matter for mankind was at issue--

In which, despite our personal friendship,

We had to be regarded as representatives of two sides

Engaged in mortal combat."

Bohr certainly seemed angrier

Than I have made him seem in the play

And he certainly claims to remember the meeting

Better than I've made him.

And I very much wish I'd had the letter when I wrote the play.

Jochen Heisenberg: I think the fact

That Bohr did not send the letter to my father

Was a much more difficult situation to deal with

Than if he had sent it.

In some way, I think my father would have welcomed the response.

And in any relationship

I think it is extremely important

To talk about situations-- even unpleasant ones.

The fact that that did not take place

I think made him in some way hurt

And indicated

That there was a loss in trust in the relationship.

It is imaginable

That there is some evidence somewhere

That would put beyond doubt

What occurred at the meeting.

But that still wouldn't put beyond doubt

What Niels Bohr thought Heisenberg's intentions were

And what Heisenberg thought Niels Bohr had understood at the meeting.

That would be just as elusive as ever.

Hans-peter du%%rr: Heisenberg died in a very biblical way.

He was at home.

He asked some of his closest friends to his deathbed.

He said, "look, I'm dying,

And I'm very sad that I did not have this last talk with Bohr."

So I knew when he said that on his deathbed

That this cast

A very dark shadow on his life.

And I felt that, whenever this comes up,

It was a friendship which was very important for him, you know?

It was destroyed by this.

Frayn: There's something very sad about these two men

As they got over in life.

Each of them separately going through that meeting

Over and over again, trying to see what had fractured their friendship,

Trying to actually get precisely right

What had occurred at that fatal meeting.

At least in my play

Their ghosts get together to talk about it.

This play is about the difficulty of knowing

Why people do what they do.

It's also about the difficulty of knowing

Why one does what one does oneself.

And in the end it comes to the conclusion

That in order to understand ourselves,

We have to talk to other people.

We have to see our ideas reflected in other people.

And that is what "Copenhagen" is about.

( piano music continues )