Once discovered, the basic physics underlying the bomb
seemed almost simple: bombard a uranium nucleus, and the resulting
split atom would release a huge amount of energy. But if the basic
principle was simple, the physics entailed in the construction
of the bomb itself was anything but. The physicists needed to figure
out how to produce enough radioactive material, as there was not nearly
enough to be found in nature. They needed to find a way to create
a nuclear chain reaction they could control, and then they needed
to figure out how to control the speed of a fast nuclear reaction,
so that it would release energy quickly enough to create a super-powerful
bomb but not so quickly that the bomb would explode too soon. And,
of course, they needed to figure out what would happen after a
nuclear explosion; there was a question at the outset, for example,
whether such an explosion would vaporize the atmosphere and destroy
all life on earth.
Perhaps the most difficult and most crucial problem that
Oppenheimer and his team faced was the design of the bomb mechanism itself.
How could they create a mechanism that would release the immense
power of nuclear fission on command? In a triumph of theoretical
and applied physics, the Los Alamos group eventually came up with
two workable bomb designs, code-named "Little Boy" and "Fat Man."
Little Boy, the U-235 bomb, had the simpler design of
the two, and the physicists were certain that it would work. The
mechanism used a gun-assembly method, in which one subcritical
mass of U-235 is fired at another subcritical mass of U-235. When
the two join, they form a critical mass and ignite in a nuclear
reaction. This is the type of bomb which was dropped over the Japanese
city of Hiroshima.
Fat Man, the plutonium bomb, used a different method:
the implosion method. In the Fat Man bomb, a subcritical sphere
of plutonium is surrounded by explosives, and when the explosives fire,
a shock wave compresses the plutonium into a critical mass, setting
off a nuclear reaction. It was the Fat Man bomb that was dropped
over Nagasaki, Japan. As this method was somewhat more complicated
than the gun-assembly method, scientists were less sure it would
work, and decided to test it out.
As the scientists were celebrating their breakthrough,
foremost in their mind was the thought that they had done it, they
had beaten Germany to the creation of the bomb. After all, the
race against Germany had been the driving purpose of the Manhattan
Project and the reason given by many of the physicists involved
for why they were so passionately committed to the bomb effort.
But how real was the German threat? In 1944, as the Los
Alamos physicists were readying themselves for a test of the nuclear
bomb, the American government finally learned the status of the
German nuclear program.
In June of 1944, the Allies invaded France. A special
team sent in by General Groves was charged with discovering how
far German nuclear development had progressed. As the Allies pushed
further and further into the continent, Groves's special team was
able to report back: the German nuclear program had barely existed.
In 1940, the Germans had started investigations into the
possibilities of nuclear power, but in 1942, they stopped. This
was probably due in part to Hitler's lack of vision; he was unable
to see the potential of nuclear weapons. Also, pro-German, anti-Nazi
physicists who were unwilling to hand over such a dangerous weapon
to Hitler may have sabotaged the bomb project from the inside.
Whatever the reason, the nuclear program had been cast aside, and
by December of 1944, the United States was aware of this.
The Manhattan Project had been intended to get the bomb before
Germany; the United States now knew that Germany would never have
the bomb. And yet the project continued unabated. The swift progress
continued even after the German surrender. In fact, Oppenheimer
later remembered this as the period in which the Los Alamos physicists
worked the hardest.
The United States government had its own reasons for continuing
with the Manhattan Project. For one thing, there was still Japan with
which to contend–the country showed no sign of backing down, and
the war in the Pacific was still going strong. For another, the
Soviet Union was waiting in the wings as a potential American enemy,
and some historians have speculated that farsighted American leaders
anticipated the post-war Cold War and had always wanted the bomb
for use against the Soviet Union, rather than the Axis forces.
But whatever the government's reasons, the question remains: why
did the scientists at Los Alamos continue their work without pause,
even after the German surrender? Were they blinded by their excitement
over the technical and scientific breakthroughs? Whether or not
this was the case among some of the residents at Los Alamos, it
cannot be said that Oppenheimer and the majority of his colleagues
were blind to the political and moral implications. Oppenheimer
and Bohr had even started holding discussions among the scientists
at Los Alamos, providing a forum for scientists to discuss the
dangers and possibilities of nuclear power. As they later explained
in numerous speeches and memoirs, these scientists were well aware
of the dangers that accompanied their discoveries, but they felt
strongly the duty to protect their country and believed that succeeding
in the creation of the atomic bomb was the best and only way they
could effectively do so.
If any of the scientists at Los Alamos did blind themselves
to the larger ramifications of the atomic bomb, choosing instead
to focus on solving the technical problems of the "gadget," as
the bomb was commonly called, they were about to get a wake up
call that no one could have ignored. In 1945, the scientists at
Los Alamos would finally see their work come to fruition and would
fully realize the devastating power of their creation.
