May 25, 2000
The Unanswered Question
THOMAS POWERS
Copenhagen
a play by Michael Frayn and directed by
Michael Blakemore at the Royale Theater, New York, opened April 11,
2000.
96 pages, $10.95 (paperback)
published by Play published by Methuen
Drama
Something happenedsome terrible offense was given which
could never be recalledduring the wartime visit of the
German physicist Werner Heisenberg to the man who probably meant
most to him in the world, the Danish physicist Niels Bohr. It
would be forgotten now, certainly Michael Frayn never would have
written a play about it, if the offense had not somehow involved
Heisenberg's role as a leader of the German effort to invent
atomic bombs. But the bomb was part of it and scientists and
historians have been arguing about what happened ever since.
Here is what is known: in September 1941 Heisenberg traveled to
Copenhagen, where he told Bohr that in Germany a research effort
was underway to develop bombs using the principle of atomic
fission. Some kind of misunderstanding ensued. In despair
Heisenberg told his wife and close friends that the conversation
had gone astray, Bohr became too angry to continue, the meeting
ended abruptly. Bohr's wife and friends later confirmed that
indeed he was angry, so angry that the old friendship and
intimate working relationship could never be restored. They did
not see each other for many years, until Heisenberg came again to
Denmark in 1947. There, in Tisvilde, where Bohr had a house in
the country, they tried to sort out the earlier conversation but
could agree on littlenot even where it took place: on an
evening walk, as Heisenberg remembered, or in Bohr's study in his
home? "After a while," Heisenberg wrote in a memoir, "we both
came to feel that it would be better to stop disturbing the
spirits of the past."
There is no evidence that the two men ever broached the subject
again during the remaining fifteen years of Bohr's life, but
plenty of other people did, then and later. The 1941 meeting was
minutely analyzed by American and British intelligence
authorities after Bohr's escape to Sweden in 1943, one jump ahead
of the Germans. Rumor of Heisenberg's visit spread through the
scientific grapevine even before the war was over, and its
meaning was hotly debated afterward. Why had Heisenberg come to
Copenhagen? What made Bohr so angry?
The interest in these questions wasn't idle. The German military
had placed Heisenberg in charge of theoretical work on the
feasibility of atomic bombs during the first weeks of the war and
he remained a principal director of uranium research until the
last shots were fired. When the war ended he was in southern
Germany working on a small experimental nuclear reactor which
never achieved a self-sustaining chain reaction. It was a tiny
program without scientific or military significance. Bohr,
meanwhile, had gone on from Sweden to Britain and the secret
American laboratory at Los Alamos in the high desert of New
Mexico. There he had alarmed officials with reports of
Heisenberg's progress toward a bomb, had established an intimate
friendship and excellent working relationship with J. Robert
Oppenheimer, director of the American laboratory, and had even
made a small theoretical contribution to the design of the
triggering device for the plutonium bomb that destroyed
Nagasaki.
That's roughly it. Heisenberg came, they talked, it went badly.
Frayn has solid reasons for his version of how the conversation
might have gone, but the fact of it is the only point universally
accepted. On almost every detail there is more than one opinion;
long books have been written trying to sort it all out. Frayn is
not trying to establish what really happened; it is what might,
could, or should have happened that interests him and gives the
play its power as a work of ideas. When Heisenberg in the first
year or two after the war tried to explain how he and his closest
colleagues approached the bomb-making project he was angrily
slapped down by scientists involved with the American effort.
Critics said Heisenberg had bungled the physics and then tried to
disguise his failure with a fable about moral reservations. But
interest in the visit never quite died. After all, Heisenberg
came to see Bohr in 1941 in German-occupied Denmark; he risked
prison or worse by telling his old friend that Germany had a bomb
program. Why did he come? What made Bohr so angry? In the absence
of accepted answers to these questions the British playwright
Michael Frayn has in effect invited three figures of
historyHeisenberg, Bohr, and Bohr's wife, Margretheto
do now in his play Copenhagen what they never managed to
do in life: to question each other about the famous visit, to
answer forthrightly, and to listen.
Frayn has been a hard-working author and playwright for decades,
but his previous eight novels and fifteen plays offer nothing
quite like the intellectual dazzle and moral seriousness of
Copenhagen. Despite the successful eighteen-month run of
the play in Britain, first at the Royal National Theatre and
later in the West End, American producers were long skittish
about bringing the play to Broadway. Copenhagen is not
only short on laugh lines (there are a few, all rueful) but it
focuses on two subjects which are difficult under any
circumstancesknowing who we are and what we mean, and
knowing when we have reached the frontier separating right from
wrong. No play has considered moral issues of such depth and
complexity since Rolf Hochhuth's 1963 play The Deputy, but
where Hochhuth launched an accusation against Pope Pius XII for
his silence during the Holocaust, Frayn simply asks a
questionindeed he asks it twice, as we shall see. I expect
no rush from historians and the community of scientists to answer
it.
But Frayn begins with characters, not ideas. Perhaps no
collaboration in the history of science was closer than
Heisenberg's with Bohr and certainly none was more fruitful. For
three years in the 1920s, while Heisenberg was an assistant in
Bohr's institute, they more or less invented modern quantum
physics. But to call what they did "working together" is a bit of
a stretch. They tackled problems very differently. Bohr was slow,
careful, even ponderous as he took physical ideas and reduced
them to plain language anyone could understandeven his
nonmathematical wife, Margrethe, a practical, skeptical woman who
did not grant her trust to all of the brilliant students who
passed through Bohr's world. For Heisenberg in particular she
seemed to feel some reservation; why, exactly, she never said.
Perhaps it was nothing more complicated than a feeling of being
excluded from the extraordinary intimacy that Bohr and Heisenberg
established on their long walks together. For a time it must have
seemed that no one could drive a wedge between those two.
Margrethe wasn't the only one to find something a little chilly
and dismissive about Heisenberg's genius. He raced ahead
intellectually in the same way he plunged downhill skiing. He did
not like to wait, even for Bohr, and the idea for which
Heisenberg is best rememberedthe uncertainty principle,
which Frayn exploits with great imagination and subtletywas
conceived and defended almost in the teeth of Bohr. The arguments
were so fierce that the two men sometimes burst asunder,
disappearing for days or weeks to think and work alone. "You're a
lot better off apart, you two," says Frayn's fictional Margrethe.
The real Margrethe probably thought much the same. In the end
Heisenberg and Bohr agreed to look at physical phenomena in two
ways simultaneously, as both wave and particle, an insight (both
men insisted it was not a compromise) thereafter called "the
Copenhagen interpretation."
The play opens at an unspecified time. The characters have all
died but are restless and questing in afterlife. The conversation
takes place in the Bohrs' house in Carlsbergthe "House of
Honor" given to Bohr as Denmark's greatest scientistbut the
stage is almost bare. Three chairs are the only furnishings. One
has arms and it is Bohr who mostly sits there. A hallway leads
away to a door at the left rear. Through that door Heisenberg
will arrive for his visitnot just once, but three times, as
they parse and re-parse all the possible ways of answering
Margrethe's opening question: "But why?... Why did he come to
Copenhagen?"
There is no action to speak of, just Heisenberg's repeated
arrival and departure, Bohr and Heisenberg setting off on their
walksthe long walk after they first met (when Bohr's newest
son, as Margrethe reminds him, was one week old), the too-short
walk that ended so badly the night Heisenberg tried to talk about
bombs. The triangle created by the three characters is repeatedly
broken and redrawn. Sometimes the governing alliance is Bohr and
his wife, sometimes Bohr and Heisenberg, then back again. As
played by Philip Bosco at New York City's Royale Theater, Bohr is
a little uncertain with age but very much the man of science,
dropping everything for the pursuit of an idea, quite unaware
that his pride is sometimes involved, and his pride can be like
iron. Mercifully Bosco makes no attempt to reproduce the speech
of the Bohr of history, who famously mumbled and garbled his
words in a volume ever dwindling till his listeners were crowded
around in a breathless knot, straining to hear. Blair Brown is
Margrethe: sensible shoes, a plain suit, hair gray at the
temples, nothing that could possibly be mistaken for a genuine
smile crossing her face. She didn't like Heisenberg's sudden
intrusion at the time and she doesn't like it now, that is
clear.
But Heisenberg is the great question in this play, as he was in
life. He is played by Michael Cumpsty as a figure of astonishing
power, confidence, clarity of desire, self-knowledgeuntil
it all slips suddenly away and he becomes as baffled by the
difficulty of understanding what he was up to as the bewildered
Bohr. The Heisenberg who opened in London in May 1998 was crisper
in speech, cooler, subtler, sometimes hurt by what was said to
him, but the play's British director, Michael Blakemore, has
evidently encouraged, certainly allowed, Cumpsty to play a
stronger, more positive, altogether more passionate figure in the
American productionnot at all the Heisenberg of history any
more than Bosco plays the real Bohr. This Heisenberg, apart from
initial moments of diffidence, is a man with ready access to a
fund of strong emotion. He laughs, he grows excited, he becomes
angry and expresses his anger. He even shouts and what's more, he
shouts at Bohr. He all but roars.
Frayn never strays far from the known; the histories of these
people have been minutely recorded on just about every subject
imaginable except, of course, the blank pages of Heisenberg's
visit. Frayn draws on the rest of their lives to coax out a
portrait of their relations that might explain what went wrong.
They have plenty to talk abouttheir initial walks together
through the Danish countryside, the intellectual struggle that
culminated in the Copenhagen interpretation, Heisenberg's
difficulties with the Gestapo after Hitler's rise to power, the
terrible day when the Bohrs' oldest son, Christian, was swept
overboard in a heavy sea and drowned. There are three sound
effects in this play: the ring of the bell pull when Heisenberg
arrives (the Bohrs turn expectantly, almost fearfullythey
are not at all eager, in this play, to find out at last why
Heisenberg came); the sound of sea gulls as they remember once
again the awful moment when Bohr, standing in the doorway, turns
his head away and cannot say what Margrethe understands
immediately; and one other sound, shocking and unexpected, to
which I will return.
Copenhagen is an imaginative reworking of the true and
the known, but the character of the characters, the kind of
people they are, has been changedin the case of Heisenberg,
changed a lot. They are now people who might actually thrash out
a complex personal misunderstandingnot the tongue-tied,
easily hurt, too considerate, and sometimes guilt-bedeviled
figures of history who decided to quit talking about the biggest
thing ever to come between them.
The history of this event can be stunningly complex but Frayn
manages to sketch in the basics. You don't have to do any
homework to understand what they are arguing about and why it
matters. Bohr wonders if Heisenberg has come to borrow the Danish
cyclotron. (Germany has none.) Has he lost his chair at Leipzig?
(His reward, Margrethe points out, for the uncertainty paper.) Is
it conceivable (now Bosco's Bohr expresses rising anger of Old
Testament intensity) that Heisenberg has come thinking that
Bohrwho is half-Jewishwould accept sanctuary in the
German embassy when the inevitable happens and the Jews are
deported?
But none of those is the answer. Nor are the guesses Bohr made
after the war. "You told Rozental that I'd tried to pick your
brains about fission," says Frayn's frustrated Heisenberg.
You told Weisskopf that I'd asked you what you knew about the
Allied nuclear program. Chadwick thought I was hoping to
persuade you that there was no German program. But then you
seem to have told some people that I'd tried to recruit you to
work on it.
In Copenhagen Heisenberg does want to know if there's an
Allied bomb program ("my dear Heisenberg...I've no idea...") but
it's not the reason he's come. What he intends is immeasurably
bolderto tell Bohr that now, in the very early stages of
fission research, scientists can still tell officials that bombs
are too difficult and expensive, and he wants Bohr to press this
point upon the Americans"to tell them we can stop it
together." The plan is of course preposterous and seems to
collapse as soon as it's put into words.
But crazy as it is, Frayn suggests, this really was the reason
Heisenberg came to Copenhagen. The response is predictable. Bohr
is angry, Margrethe, says,
because he is beginning to understand! The Germans drive
out most of their best physicists because they're Jews. America
and Britain give them sanctuary. Now it turns out that this
might offer the Allies a hope of salvation. And at once you
come howling to Niels begging him to persuade them to give it
up... The gall of it! The sheer, breathtaking gall of it!
All this is argued with great spirit and feeling, but after
Heisenberg's scheme collapses, as it was bound to do in wartime,
the play turns inward and backward, ranging through the lives of
these three for the seeds of their angry
encounterMargrethe's resentment of Heisenberg as an
unwanted son, Bohr's conviction that in science as in life
Heisenberg always needed slowing down, the death of Christian too
painful to discuss, the awful complicity in crime which attached
like a port wine stain to every German who remained in Germany
during the war. "Everyone understands uncertainty. Or thinks he
does," says Frayn's Heisenbergthe principle that in the
subatomic world you can never know both the position and the
velocity of a particle. One or the other, not both. As this
notion is explored Frayn deepens human mysteries as wellwhy
people do what they do ("Because I never thought of it," says
Heisenberg of his failure to perform an important calculation;
"Because it didn't occur to me!"), the tricks played by memory,
the difficulty of seeing into other minds. We know other people
as we know particles passing through a cloud chamber, not of
themselves, but by the droplets of water vapor left by their
passage. With people it is the same: we catch glimpses, as of
walkers at night, passing from time to time beneath the light of
a street lamp. If Bohr is right, and the Copenhagen
interpretation restores humankind to the center of the universe,
then the observer determines what can be observed; and, Margrethe
continues, "If it's Heisenberg at the center of the universe,
then the one bit of the universe that he can't see is
Heisenberg."
Heisenberg: So...
Margrethe: So it's no good asking him why he came to
Copenhagen in 1941. He doesn't know!
This back and forth plays well and reads well, but it's not what
gives the play its genuine tension, and it's not why scientists
and historians have been arguing for sixty years about why
Heisenberg came, and what his visit had to do, if anything, with
the Allied discovery at war's end of the startling and, at first,
inexplicable absence of a big German effort to build atomic
bombs. Things need not and might not have turned out that way.
"Let's suppose for a moment," says Bohr, "that...I stop, and
control my anger, and turn to him, and ask him why.... Why are
you so confident that it's going to be reassuringly difficult to
build a bomb with 235? Is it because you've done the
calculation?... No. It's because you haven't calculated
it...."
Heisenberg: And of course now I have realised. In fact
it wouldn't be all that difficult. Let's see...
He begins to talk numbers.
It's not in the script but it's very much in the
theaterthe evening's third sound effect, a roar and
rumbling that shakes the gut of every playgoer with stunning
intensity and lasts long enough for the thought to sink in: if
Bohr had responded purely as a scientist, nosing out the absent
calculation, pushing the problem forward, helping Heisenberg to
see he couldn't slip out the back door after all... Tons of
uranium 235 were not required for a bomb, only kilograms. Germany
could have done it.
Heisenberg: Almost certainly not.
Bohr: Just possibly, though.
Heisenberg: Just possibly.
It's wonderful theater, and it tells us what a vast chasm
separates Hitler with no bomb from Hitler with a bomb in time to
use it. But in fact the passage amounts to a remark by the
playwright: damn good thing Bohr was thinking like an aggrieved
Dane, Frayn says in effect, and treated Heisenberg like a man
with a hidden agenda... But this is not where the play has been
leading.
Whatever it was that Heisenberg said or did in Copenhagen in
1941, Margrethe never forgave him for it. At a service for Bohr
in 1963, standing with the physicist Sam Goudsmit, who was
scientific director of a wartime inquiry into German atomic
research, she pointed to Heisenberg nearby and said, "Goudsmit,
that wartime visit... was a hostile visit, no matter what people
say or write about it." In Copenhagen Frayn gives her
anger free rein.
Margrethe: You've come to show us how well you've done
in life... 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
successfully that he's now also got a wonderfully important
moral dilemma to face...
Heisenberg: All the same, I don't tell Speer that the
reactor...
Margrethe: ...will produce plutonium, no, because you're
afraid of what will happen if...you fail... Please don't tell
us you're a hero of the resistance.
Heisenberg: I've never claimed to be a hero.
Bohr takes it all in good stride, but death has done nothing to
soothe Margrethe's fury. It seems odd at first. What has
Heisenberg done really? His visit to Copenhagen in 1941, the play
Frayn has written about it, and Margrethe's anger at its core,
all make sense only after we know how the story turned out.
Heisenberg returned to Berlin where German officials were
persuaded early in 1942 by Heisenberg and others that building a
bomb was too expensive and uncertain for Germany in wartime. In
June the German czar in charge of economic mobilization for the
war, Albert Speer, met with Heisenberg and other leading
scientists to argue one final time the wisdom of an all-out bomb
program. German generals had pressed Speer to take the
possibility seriously but Heisenberg stressed the difficulties
and unknowns, requested only modest sums of money for reactor
research, and convinced Speer that the bomb project offered no
hope of success before the end of the war. The record of the
German effort reveals nothing we might describe as a
counter-historyno glimpses in documents or memoirs, or even
anecdotes of Heisenberg beneath a succession of street lamps,
caught urging a bomb program on officials. Indeed, the few
glimpses we do get are of just the oppositethe meeting with
Speer and the visit to Bohr are only two examples.
What is startling and even subversive about Frayn's play is the
question that slips in through the door with Heisenberg's
arrival, a question that eventually stirs Margrethe to lash out
in protective fury. But at first you hardly notice. How did the
famous conversation begin? "I simply asked you," says Heisenberg,
"if as a physicist one had the moral right to work on the
practical exploitation of atomic energy. Yes?"
Bohr does not recall, the discussion veers elsewhere, the
question goes unanswered. Frayn did not invent this question; it
is a close paraphrase of what Heisenberg in a memoir says he
asked, and Heisenberg used roughly similar words on half a dozen
other occasions. Whether Bohr would have remembered it that way,
I don't know; he never described the evening in print, or in
detail to anyone who has left a clear record of what he said. But
in the play Margrethe understands all too well where this
question will lead. In point of fact Heisenberg did not build a
bomb, whereas Bohr, in some small but not quite inconsequential
way, helped to do so. "You're not suggesting that Niels did
anything wrong in working at Los Alamos?" demands Margrethe.
Heisenberg: Of course not. Bohr has never done anything
wrong...
Margrethe: You're not implying that there's anything
that Niels needs to explain or defend?
Heisenberg: No one has ever expected him to explain or
defend anything. He's a profoundly good man.
A branding iron could not make the point more painfully. But
Frayn is not venting some crazy animus against Bohr;
Copenhagen isn't an attempt to turn the tables, invite
Heisenberg back into the family of science, and drive Bohr out.
Frayn is restoring to the scientists of all sides something
denied to them by the historians: moral autonomythe
capacity to question what they have been asked to do. Heisenberg
is not a hero of the resistance, but something more
disturbinga scientist asked to build a bomb who raised the
question whether it was right. Margrethe recognizes the challenge
in this fact. If Heisenberg didn't come to borrow the cyclotron,
show himself off, announce some personal setback like the loss of
his professorial chair, spy on the Allies, probe Bohr for
thoughts on how to make a bomb, or invite him to throw in his lot
with the Germans, then possiblyjust possiblyhis goal
was "very simple, when you come right down to it," as Bohr tells
his wife in the opening scene: "He wanted to have a talk." And
possiblyjust possiblywhat he wanted to talk about was
the one question posed twice, at the beginning and the end of
Frayn's remarkable play: "Does one as a physicist have the moral
right to work on the practical exploitation of atomic
energy?"
For the scientists who succeeded where Heisenberg failed, and
for the historians who have recounted their efforts, answering
Heisenberg's question is no simple matter. But once the question
is posed there are only two possible responsesto ignore the
question and to dismiss his visit to Copenhagen as somehow safe
and self-serving, or to grant him the courtesy of an attempt to
reply.