ON THE Manhattan Project was a traumatic experience. It is not
often given to one to participate in the birth of a new era.
For some the effect has endured throughout their lives; I am
one of those.This
essay is not an autobiography; it describes only my involvement
in the genesis of the atomic bomb. All extraneous personal elements
are left out, but their exclusion does not mean that they are
unimportant. Our hopes and fears, our resolutions and actions,
are influenced by an infinite number of small events interacting
with each other all the time. Because of this, each of us may
react differently to the same set of conditions. The experience
of every Los Alamite is unique.
AT THE BEGINNING
of 1939; when the news reached me of the discovery of fission,
I was working in the Radiological Laboratory in Warsaw. Its
director was Ludwik Wertenstein, a pupil of Marie Curie and
a pioneer in the science of radioactivity in Poland. Our source
of radiation consisted of 30 milligrams of radium in solution;
every few days we pumped the accumulated radon into a tube filled
with beryllium powder. With this minute neutron source we managed
to carry out much research, even competing with Enrico Fermi's
prestigious team, then in Rome, in the discovery of radionuclides.
Our main achievement was the direct evidence of the inelastic
scattering of neutrons; my doctoral thesis was on that subject.
In the earlier
experiments on inelastic scattering we used gold as the scatterer.
By the end of 1938 I had begun to experiment with uranium, so
when I heard of the fission of uranium, it did not take me long
to set up an experiment to see whether neutrons are emitted
at fission. I soon found that they are-indeed, that more neutrons
are emitted than produce fission. From this discovery it was
a fairly simple intellectual exercise to envisage a divergent
chain reaction with a vast release of energy. The logical sequel
was that if this energy were released in a very short time it
would result in an explosion of unprecedented power. Many scientists
in other countries, doing this type of research, went through
a similar thought process, although not necessarily evoking
the same reaction.
In my case,
my first reflex was to put the whole thing out of my mind, like
a person trying to ignore the first symptom of a fatal disease
in the hope that it will go away. But the fear gnaws all the
same, and my fear was that someone would put the idea into practice.
The thought that I myself would do it did not cross my mind,
because it was completely alien to me. I was brought up on humanitarian
principles. At that time my life was centered on doing "pure"
research work, but I always believed that science should be
used in the service of mankind. The notion of utilizing my knowledge
to produce an awesome weapon of destruction was abhorrent to
my gnawing fear, the "someone" who might put it into
practice was precisely defined: German scientists. I had no
doubt that the Nazis would not hesitate to use any device, however
inhumane, if it gave their doctrine world domination. If so,
should one look into the problem to find out whether the fear
had a realistic basis? Wrestling with this question was agonizing,
and I was therefore glad that another pressing matter gave me
an excuse to put it aside.
matter was my move to England, where I was to spend a year with
Professor James Chadwick in Liverpool, on a grant to work on
the cyclotron which was then being completed there. This was
my first trip abroad, and the upheaval kept me busy both before
the journey in April 1939 and for some time afterward, because
I spoke very little English, and it took me a long time to settle
the spring and summer the gnawing went on relentlessly. It intensified
with the increasing signs that Germany was getting ready for
war. And it became acute when I read an article by S. Flügge
in Naturwissenschaften mentioning the possibility of
I worked out a rationale for doing research on the feasibility
of the bomb. I convinced myself that the only way to stop the
Germans from using it against us would be if we too had the
bomb and threatened to retaliate. My scenario never envisaged
that we should use it, not even against the Germans. We needed
the bomb for the sole purpose of making sure that it would not
be used by them: the same argument that is now being used by
proponents of the deterrence doctrine.
wisdom of hindsight, I can see the folly of the deterrent thesis,
quite apart from a few other flaws in my rationalization. For
one thing, it would not have worked with a psychopath like Hitler.
If he had had the bomb, it is very likely that his last order
from the bunker in Berlin would have been to destroy London,
even if this were to bring terrible retribution to Germany.
Indeed, he would have seen this as a heroic way of going down,
in a Götterdämmerung.
at the time required that the feasibility of the atom bomb be
established, one way or the other, with the utmost urgency.
Yet I could not overcome my scruples. I felt the need to talk
it over with someone, but my English was too halting to discuss
such a sensitive issue with my colleagues in Liverpool.
1939, having gone to Poland on a personal matter, I took the
opportunity to visit Wertenstein and put my dilemma before him.
The idea of a nuclear weapon had not occurred to him, but when
I showed him my rough calculations he could not find anything
scientifically wrong with them. On the moral issue, however,
he was unwilling to advise me. He himself would never engage
in this type of work, but he would not try to influence me.
It had to be left to my own conscience.
broke out two days after I returned to Liverpool. Within a few
weeks Poland was overrun. The stories that Hitler's military
strength was all bluff, that his tanks were painted cardboard,
turned out to be wishful thinking. The might of Germany stood
revealed, and the whole of our civilization was in mortal peril.
My scruples were finally overcome.
1939 my English was good enough for me to give a course of lectures
on nuclear physics to the Honors School at Liverpool University,
but by then the department's senior research staff had disappeared:
they had gone to work on radar and other war projects. I had,
therefore, to approach Chadwick directly with an outline of
my plan for research on the feasibility of the atom bomb. His
response was typically Chadwickian: he just grunted, without
letting on whether he had already thought of such a plan. Later
I learned that other scientists in the United Kingdom did have
the same idea, some of them with similar motivation.
A few days
later Chadwick told me to go ahead and gave me two young assistants.
One of them presented a problem. He was a Quaker and as such
had refused to do war work. He was therefore sent to Liverpool
University for academic duties -but was diverted to work with
me on the atom bomb! I was not allowed to reveal to him the
nature of our research, and I had qualms of conscience about
using him in such an unethical way.
idea which I put to Chadwick was that for the atom bomb the
chain reaction would have to be propagated by fast neutrons;
otherwise it would not differ much from a chemical explosive.
It was therefore important to measure the fission cross-section
for fast neutrons, the energy distribution of fission neutrons,
their inelastic scattering, and the proportion of those captured
without producing fission. It was also relevant to find out
whether stray neutrons might cause a premature start of the
reaction, which meant determining the probability of spontaneous
fission of uranium.
up a small team of young but devoted physicists and used the
cyclotron to tackle some of these problems. Later we were joined
by Otto Frisch who measured the fast neutron fission cross-section
for uranium-235. I had the idea of using plutonium, but we had
no means of making it.
As a result
of these investigations, we were able to establish that the
atom bomb was feasible from the scientific point of view. However,
it also became clear that in order to make the bomb a vast technological
effort would be required, far exceeding the manpower and industrial
potential of wartime Britain. A top-level decision was reached
to collaborate with the Americans. And so I found myself eventually
in that "wondrous strange" place, Los Alamos.
MARCH 1944 I experienced a disagreeable shock. At that time
I was living with the Chadwicks in their house on the Mesa,
before moving later to the "Big House;' the quarters for
single scientists. General Leslie Groves, when visiting Los
Alamos, frequently came to the Chadwicks for dinner and relaxed
palaver. During one such conversation Groves said that, of course,
the real purpose in making the bomb was to subdue the Soviets.
(Whatever his exact words, his real meaning was clear.) Although
I had no illusions about the Stalin regime—after all,
it was his pact with Hitler that enabled the latter to invade
Poland-I felt deeply the sense of betrayal of an ally. Remember,
this was said at a time when thousands of Russians were dying
every day on the Eastern Front, tying down the Germans and giving
the Allies time to prepare for the landing on the continent
of Europe. Until then I had thought that our work was to prevent
a Nazi victory, and now I was told that the weapon we were preparing
was intended for use against the people who were making extreme
sacrifices for that very aim.
about the purpose of our work gained substance from conversations
with Niels Bohr. He used to come to my room at eight in the
morning to listen to the BBC news bulletin. Like myself, he
could not stand the U.S. bulletins which urged us every few
seconds to purchase a certain laxative! I owned a special radio
on which I could receive the BBC World Service. Sometimes Bohr
stayed on and talked to me about the social and political implications
of the discovery of nuclear energy and of his worry about the
dire consequences of a nuclear arms race between East and West
which he foresaw.
and the growing evidence that the war in Europe would be over
before the bomb project was completed, made my participation
in it pointless. If it took the Americans such a long time,
then my fear of the Germans being first was groundless.
became evident, toward the end of 1944, that the Germans had
abandoned their bomb project, the whole purpose of my being
in Los Alamos ceased to be, and I asked for permission to leave
and return to Britain.
OTHER scientists not make the same decision? Obviously, one
would not expect General Groves to wind up the project as soon
as Germany was defeated, but there were many scientists for
whom the German factor was the main motivation. Why did they
not quit when this factor ceased to be?
I was not
allowed to discuss this issue with anybody after I declared
my intention to leave Los Alamos, but earlier conversations,
as well as much later ones, elicited several reasons.
frequent reason given was pure and simple scientific curiosity-
the strong urge to find out whether the theoretical calculations
and predictions would come true. These scientists felt that
only after the test at Alamogordo should they enter into the
debate about the use of the bomb.
prepared to put the matter off even longer, persuaded by the
argument that many American lives would be saved if the bomb
brought a rapid end to the war with Japan. Only when peace was
restored would they take a hand in efforts to ensure that the
bomb would not be used again.
while agreeing that the project should have been stopped when
the German factor ceased to operate, were not willing to take
an individual stand because they feared it would adversely affect
their future career.
I have just described-scientists with a social conscience-were
a minority in the scientific community. The majority were not
bothered by moral scruples; they were quite content to leave
it to others to decide how their work would be used. Much the
same situation exists now in many countries in relation to work
on military projects. But it is the morality issue at a time
of war that perplexes and worries me most.
I came across a document released under the Freedom of Information
Act. It is a letter, dated May 25, 1943, from Robert Oppenheimer
to Enrico Fermi, on the military use of radioactive materials,
specifically, the poisoning of food with radioactive strontium.
The Smyth Report mentions such use as a possible German threat,
but Oppenheimer apparently thought the idea worthy of consideration,
and asked Fermi whether he could produce the strontium without
letting too many people into the secret. He went on: "I
think we should not attempt a plan unless we can poison food
sufficient to kill a half a million men." I am sure that
in peacetime these same scientists would have viewed such a
plan as barbaric; they would not have contemplated it even for
a moment. Yet during the war it was considered quite seriously
and, I presume, abandoned only because it was technically infeasible.
TOLD Chadwick that I wished to leave the project, he came back
to me with very disturbing news. When he conveyed my wish to
the intelligence chief at Los Alamos, he was shown a thick dossier
on me with highly incriminating evidence. It boiled down to
my being a spy: I had arranged with a contact in Santa Fe to
return to England, and then to be flown to and parachuted onto
the part of Poland held by the Soviets, in order to give them
the secrets of the atom bomb. The trouble was that within this
load of rubbish was a grain of truth. I did indeed meet and
converse with a person during my trips to Santa Fe. It was for
a purely altruistic purpose, nothing to do with the project,
and I had Chadwick's permission for the visits. Nevertheless,
it contravened a security regulation, and it made me vulnerable.
Fortunately for me, in their zeal the vigilant agents had included
in their reports details of conversations with dates, which
were quite easy to refute and to expose as complete fabrications.
The chief of intelligence was rather embarrassed by all this
and conceded that the dossier was worthless. Nevertheless, he
insisted that I not talk to anybody about my reason for leaving
the project. We agreed with Chadwick that the ostensible reason
would be a purely personal one: that I was worried about my
wife whom I had left in Poland.
on Christmas Eve 1944, I sailed for the United Kingdom, but
not without another incident. Before leaving Los Alamos I packed
all my documents-research notes as well as correspondence and
other records-in a box made for me by my assistant. En route
I stayed for a few days with the Chadwicks in Washington. Chadwick
personally helped me to put the box on the train to New York.
But when I arrived there a few hours later, the box was missing.
Nor, despite valiant efforts, was it ever recovered.
ON THE Manhattan Project, as I said at the outset, has had an
enduring effect on my life. Indeed, it radically changed my
scientific career and the carrying out of my obligations to
the atom bomb convinced me that even pure research soon finds
applications of one kind or another. If so, I wanted to decide
myself how my work should be applied. I chose an aspect of nuclear
physics which would definitely be beneficial to humanity: the
applications to medicine. Thus I completely changed the direction
of my research and spent the rest of my academic career working
in a medical college and hospital. While
this gave me personal satisfaction, I was increasingly concerned
about the political aspects of the development of nuclear weapons,
particularly the hydrogen bomb, about which I knew from Los
Alamos. Therefore, I devoted myself both to arousing the scientific
community to the danger, and to educating the general public
on these issues. I was instrumental in setting up the Atomic
Scientists Association in the United Kingdom, and within its
framework organized the Atom Train, a travelling exhibition
which explained to the public the good and evil aspects of nuclear
energy. Through these activities I came to collaborate with
Bertrand Russell. This association led to the foundation of
the Pugwash Conferences, where I met again with colleagues from
the Manhattan Project, who were also concerned about the threat
to mankind that has arisen partly from their work.
years one question keeps nagging me: have we learned enough
not to repeat the mistakes we made then? I am not sure even
about myself. Not being an absolute pacifist, I cannot guarantee
that I would not behave in the same way, should a similar situation
arise. Our concepts of morality seem to get thrown overboard
once military action starts. It is, therefore, most important
not to allow such a situation to develop. Our prime effort must
concentrate on the prevention of nuclear war, because in such
a war not only morality but the whole fabric of civilization
would disappear. Eventually, however, we must aim at eliminating
all kinds of war."