Absence of A-bomb
Were the Nazis dupedor simply dumb?
BY WARREN P. STROBEL
'But why?... Why did he come to Copenhagen?" With that pregnant
question, Michael Frayn's Tony Award-winning play opens. Copenhagen
has revived a mystery so raw it still moves historians and physicists to flights of rage.
Why did Hitler's Germany fail, utterly, to develop nuclear weapons? And why did
brilliant physicist Werner Heisenberg, a central figure in Germany's nuclear research, visit Nobel laureate Niels Bohr in
occupied Denmark in September 1941? Did he go as a loyal German, to learn how
much Bohr (and the Allies) knew about atom bombs? Or as a scientist-hero, trying
to stall Nazi research and naively hoping to persuade Bohr to restrain the Allies?
After a German and an Austrian discovered fission in 1938, almost everyone
thought Germany would be the first to build nuclear weapons. In August 1939,
Albert Einstein warned President Roosevelt of the threat. Dread of a Nazi A-bomb drove the Manhattan Project.
Yet an Allied mission code-named Alsos, following on the heels of troops liberating
Europe, found only a primitive program. No working nuclear reactor. No large
quantities of separated Uranium-235, a basic bomb ingredient. No credible bomb
design. "Sometimes we wondered if our government had not spent more money on
our intelligence mission than the Germans spent on their whole project," wrote Alsos
scientific director Samuel Goudsmit.
Uncertain man. To understand Germany's failure, historians (and playwright
Frayn) focus on the enigma that is Heisenberg. The brash German patriot was just
32 when he won the Nobel Prize for the uncertainty principle, which states that it
is possible to know a subatomic particle's position or momentum, but not both. In
simplified form, the principle means that the very act of observing something
changes its behavior.
"Uncertainty" is the leitmotif of Heisenberg's life. Touring the United States in the summer of 1939, he had
offers of refuge but returned home. He regarded Hitler as a thug and transitional figure, and said he stayed to salvage German science for
later. After the war, most physicists in America reviled his attempts to justify himselfand the mysterious
wartime trip to Copenhagen to talk about fission with Bohr. He died in
1976. "Time and time again I've explained it," Frayn's Heisenberg laments from beyond the grave. "To interrogators and intelligence officers, to journalists and historians. The more I've explained, the
deeper the uncertainty has become."
Frayn's play reignites the animosities.
"It has to do with Nazis and atomic bombs,
so emotions are dredged up," says Heisenberg biographer David Cassidy. After all,
if Heisenberg and the Germans never got close to the bomb, what does that say about
those who did buildand useit?
There are many possible explanations of the German failure, and Heisenberg's
actions. But then the questions cascade like neutrons in a chain reaction.
If Heisenberg wanted to build a bomb, say his sympathizers, he would have sold the
powerful Nazi armaments minister Albert Speer on the idea at a key June 1942 briefing. By then, German physicists realized that if they constructed a nuclear reactor, it
would make plutonium, a substitute bomb fuel for U-235, which was hellishly hard
to separate from natural uranium. Yet Heisenberg downplayed hopes of making a
bomb and asked Speer for a paltry few million marks for research. His bomb program
coasted. Overseeing nuclear research was merely a means
for Heisenberg to rehabilitate himself, Cassidy says. Nazi fanatics had
called him a "white Jew" because of his links with Einstein's physics.
Mind reader. Copenhagen is based on the 1993 book Heisenberg's War. Author
Thomas Powers argues that the physicist heroically hid key calculations proving
a bomb was possible. Frayn, whose play is largely sympathetic to Heisenberg,
won't go as far: "It's a question of what was going on in Heisenberg's mind."
Or perhaps the German didn't want to promise a bomb he couldn't deliver. A
brilliant theorist, Heisenberg was a lousy engineer who often had trouble with basic
calculations. After Germany's defeat, Heisenberg and nine colleagues were interned at Farm Hall, a British country
house. Hidden microphones recorded their stunned reaction to the U.S. atomic
bombing of Hiroshima. The tapes, released in 1992, reveal a Heisenberg who
did not understand bomb physics and vastly overestimated how much U-235
was needed for "critical mass." "You're just second-raters and you might as well
pack up," a colleague gibed on the tapes.
So why did Heisenberg come to Copenhagen? By September 1941, he knew nuclear weapons were a theoretical possibility for Germanyand its enemies. He
raised the subject with Bohr, who was horrified at Heisenberg's hint. Their pre-war friendship was shattered. In a postwar
letter to journalist Robert Jungk, Heisenberg wrote that he merely wanted to discuss physicists' ethical responsibilities. Jungk later concluded he had been
duped by Heisenberg and other German scientists trying to justify their actions.
The visit was "an intelligence mission, nothing more or less," agrees Manhattan
Project physicist Arnold Kramish. Two weeks before, a Swedish newspaper had
published news of U.S. bomb research. Heisenberg wanted to learn more from
his former teacher. Bohr himself disputed Heisenberg's account of the meeting
in a letter so angry he never mailed it. Gerald Holton, a Harvard University historian of science who has seen the letter, says
it takes "serious issue" with Heisenberg's claims. It will be made public in 2012, the
50th anniversary of Bohr's death.