CUSHING STROUT
103
We have come full circle with the play's analogy between uncertainty in
physics and uncertainty in history.
The play's speculation is more appropriate to a historical drama than
it is to a history, because we know so little about it. There are no docu–
ments, only conflicting and incomplete recollections. It is possible, how–
ever, as Heisenberg's scrupulously judicious biographer, David
C.
Cassidy, has suggested, that Heisenberg was in
1941
trying to avert an
Allied crash program for a bomb that might be used on his country by
telling Bohr that the Germans were "a long way from constructing an
explosive." That hypothesis wou ld fit the point of a drawing that
Heisenberg gave to Bohr in their
1941
meeting, who passed it on to the
Los Alamos scientists when he joined their project. They judged it to be
the sketch of a reactor, not a design for a bomb. The drawing cannot
now be found. Neither the biographer nor the play mentions it, but
Frayn discusses it in his postscript, wondering why Heisenberg didn't
refer to it in order to bolster his interpretation of what he was trying to
tell Bohr.
Heisenberg had not convinced Bohr of his sincerity, as Richard
Rhodes points out in his authoritative history,
The Making of the
Atomic Bomb
(1986),
"nor in any way begun a dialogue to avert possi–
ble catastrophe ." Instead, he had only "managed potentially to alarm
Germany's most powerful enemy further with news of progress in
approaching the chain reaction. That news must necessarily accelerate
Allied efforts to build a bomb." Not surprisingly,
J.
Robert Oppen–
heimer concluded that Heisenberg wanted "to see if Bohr knew any–
thing that they did not; I believe it was a standoff."
As soon as Heisenberg heard of the Allied success in making the
bomb, he said to his scientific colleagues, in a discussion which was
secretly taped by their captors at Farm Hall in England, "At the bottom
of my heart I was really glad that it was an engine la reactorJ and not a
bomb." Yet a reactor using natural uranium can produce plutonium,
and it can be extracted by chemical means and used as an explosive. The
German scientists knew of this method and in
1942
Heisenberg told the
Nazi leaders about it, though he cautioned against expecting quick
results and emphasized the technical difficulties that remained to be
solved. Heisenberg also had another reason for visiting Copenhagen, as
Frayn's play suggests. He participated in a lecture series sponsored by
the German cultural propaganda institute.
It
would help to prove his
reliability to Gestapo officials, who had long been suspicious of him; it
would therefore give him more freedom to develop atomic physics in
