Just before the beginning of World War II, Albert Einstein
wrote a letter to President Franklin D. Roosevelt. Urged by

Hungarian-born physicists Leo Szilard, Eugene Wingner, and Edward

Teller, Einstein told Roosevelt about Nazi German efforts to purify

Uranium-235 which might be used to build an atomic bomb. Shortly after
that the United States Government began work on the Manhattan Project.

The Manhattan Project was the code name for the United States effort
to develop the atomic bomb before the Germans did. "The first
successful experiments in splitting a uranium atom had been carried
out in the autumn of 1938 at the Kaiser Wilhelm Institute in

Berlin"(Groueff 9) just after Einstein wrote his letter. So the race
was on. Major General Wilhelm D. Styer called the Manhattan Project"the most important job in the war . . . an all-out effort to build an
atomic bomb."(Groueff 5) It turned out to be the biggest development
in warfare and science\'s biggest development this century. The most
complicated issue to be addressed by the scientists working on the

Manhattan Project was "the production of ample amounts of \'enriched\'
uranium to sustain a chain reaction."(Outlaw 2) At the time,

Uranium-235 was hard to extract. Of the Uranium ore mined, only about

1/500 th of it ended up as Uranium metal. Of the Uranium metal, "the
fissionable isotope of Uranium (Uranium- 235) is relatively rare,
occurring in Uranium at a ratio of 1 to 139."(Szasz 15) Separating the
one part Uranium-235 from the 139 parts Uranium-238 proved to be a
challenge. "No ordinary chemical extraction could separate the two
isotopes. Only mechanical methods could effectively separate U-235
from U-238."(2) Scientists at Columbia University solved this
difficult problem. A "massive enrichment laboratory/plant"(Outlaw 2)
was built at Oak Ridge, Tennessee. H. C. Urey, his associates, and
colleagues at Columbia University designed a system that "worked on
the principle of gaseous diffusion."(2) After this process was
completed, "Ernest O. Lawrence (inventor of the Cyclotron) at the

University of California in Berkeley implemented a process involving
magnetic separation of the two isotopes."(2) Finally, a gas centrifuge
was used to further separate the Uranium-235 from the Uranium-238. The

Uranium-238 is forced to the bottom because it had more mass than the

Uranium-235. "In this manner uranium-235 was enriched from its normal

0.7% to weapons grade of more than 90%."(Grolier 5) This Uranium was
then transported to "the Los Alamos, N. Mex., laboratory headed by J.

Robert Oppenheimer."(Grolier 5) "Oppenheimer was the major force
behind the Manhattan Project. He literally ran the show and saw to it
that all of the great minds working on this project made their
brainstorms work. He oversaw the entire project from its conception to
its completion."(Outlaw 3) Once the purified Uranium reached New

Mexico, it was made into the components of a gun-type atomic weapon.

"Two pieces of U-235, individually not large enough to sustain a chain
reaction, were brought together rapidly in a gun barrel to form a
supercritical mass that exploded instantaneously."(Grolier 5) "It was
originally nicknamed \'Thin Man\'(after Roosevelt, but later renamed

\'Little Boy\' (for nobody) when technical changes shortened the
proposed gun barrel."(Szasz 25) The scientists were so confident that
the gun-type atomic bomb would work "no test was conducted, and it was
first employed in military action over Hiroshima, Japan, on Aug. 6,

1945."(Grolier 5) Before the Uranium-235 "Little Boy" bomb had been
developed to the "point of seeming assured of success,"(Grolier 5)
another bomb was proposed. The Uranium-238 that had been earlier ruled
out as an option was being looked at. It could capture a free neutron
without fissioning and become Uranium-239. "But the Uranium-239 thus
produced is unstable (radioactive) and decays first to neptunium-239
and then to plutonium-239."(Grolier 5) This proved to be useful
because the newly created plutonium-239 is fissionable and it can "be
separated from uranium by chemical techniques,"(6) which would be far
simpler than the physical processes to separate the Uranium-235 from
the Uranium-238. Once again the University of Chicago, under Enrico

Fermi\'s direction built the first reactor. "This led to the
construction of five large reactors at Hanford, Wash., where U-238 was
irradiated with neutrons and transmuted into plutonium."(6) The
plutonium was sent to Los Alamos. The problem to overcome in the
development of the plutonium bomb was an isotope of plutonium. The
scientists feared this isotope would cause premature detonation and
most of the plutonium would blow apart before it could all fission.

"To overcome this so-called \'defect of nature, \' the plutonium had to
be brought into a supercritical mass far faster than conventional
ballistics could achieve."(Grolier 6) Physicist Seth Neddermeyer and
mathematician John von Neumann devised the theory of "implosion." A
subcritical sphere of plutonium was surrounded