The History of Nuclear Research
June - Rutherford creates oxygen
Rutherford speculates on the existence
of the neutron at the Royal Society.
November - Urey discovers deuterium.
James Chadwick proves the existence
of neutrons, using alpha particles striking a beryllium foil. He
determines their mass by measuring the recoil tracks of known atoms
of the rarified gas in his cloud chamber.
John Cockcroft and E. T. S. Walton of Great Britain
split the atom on a linear accelerator
Leo Szilard reads H.G. Wells' novel, The World
Set Free, in which Wells prophecies an atomic war in which the
major cities of the world are destroyed.
Adolph Hitler becomes Chancellor of Germany.
Leo Szilard, a Hungarian physicist
who took refuge in London from Nazi Germany, reads about a speech
in which Lord Rutherford ridiculed the idea of using the
transformation of atoms as a source of power. Szilard realizes that,
"if we could find an element which is split by neutrons, and
which would emit two neutrons when it absorbs one neutron, such
an element could sustain a nuclear chain reaction."
Frederic and Irene Joliot-Curie
of France discover artificial radioactivity, i.e. the radioactivity
of atoms produced in transmutation experiments.
Fermi of Italy irradiates
uranium with neutrons. He believes he has produced the first transuranic
element, but unknowingly achieves the world’s first nuclear fission.
Szilard files for patent
amendments for "the liberation of nuclear energy for power production
and other purposes through nuclear 'transmutation.' "He proposes
a "chain reaction" for the first time.
Szilard files patent amendment
identifying uranium and bromine as "examples for elements from which
neutrons can liberate multiple neutrons..."
When Szilard learns that the only way for his patents on liberating
nuclear energy can be kept secret is to assign them to an agency
of the British government he offers them to the British War Office.
The British War turns down Leo
Szilard's offer to give
them his patents on nuclear energy stating, "There appears to be
no reason to keep the specification secret so far as the War Department
Szilard's offer to turn
over patents on nuclear energy, in order to keep them secret, is
accepted by British Admiralty.
Otto Hahn and Fritz Strassmann
of Germany split the uranium atom by bombarding it with neutrons
and show that the elements barium and krypton are formed.
Lisa Meitner conducts experiments verifying that heavy elements
capture neutrons and form unstable products which undergo fission.
This process ejects more neutrons continuing the fission chain reaction.
Lise Meitner and Otto Frisch of Austria announce theory
of nuclear fission.
Frederic Joliot demonstrates the possibility of splitting the
atom of uranium isotope 235.
A. Bethe, a German-born
physicist, recognizes that the fusion of hydrogen nuclei to form
deuterium releases energy. He suggests that much of the energy output
of the Sun and other stars results from energy-releasing fusion
reactions in which four hydrogen nuclei unite and form one helium
Otto Frisch detects fission fragments in an ionization chamber.
He adopts the term "fission."
First experimental fission
in U.S. takes place at Columbia University.
Bohr announces discovery
of fission at a conference in theoretical physics at George Washington
University in US
Upon hearing of discovery of fission, Robert
grasps the possibility of atomic bombs.
Szilard writes to Enrico
Fermi describing the concept
(uranium lattice in carbon) for creating a chain reaction.
first letter to President Franklin Roosevelt
leads to the formation of the Committee on Uranium. The letter,
originally drafted by Leo
Szilard states "that the
element uranium may be turned into a new and important source of
energy in the immediate future. Certain aspects of the situation
which has arisen seem to call for watchfulness and, if necessary,
quick action on the part of the Administration." After the bombing
of Hiroshima, Einstein states, "I could burn my fingers that I wrote
that first letter to Roosevelt."
Einstein and Szilard warn Roosevelt
The fear of a German atomic bomb troubled
Leo Szilard. On August 2, 1939, he and Edward Teller drove to Long
Island, New York. They went to ask Albert Einstein to sign a letter
to President Roosevelt outlining the dangers of a German bomb project.
Germany invades Poland. World War II begins.
It was not until July 13, 1942, in the
midst of World War II, that the United States undertook the Manhattan
Project to develop an atomic bomb. By December 2, a Manhattan
Project team headed by
Enrico Fermi produced the first artificial fission reaction
at the University of Chicago. Three years after its inception, the
Manhattan Project achieved its goal of developing an atomic weapon.
Construction of CP-1, or Chicago Pile
Number One, was done under the football stadium in an abandoned
squash court. On December 2, 1942, mankind first harnessed the energy
of the atom. Fermi's pile produced only 1/2 watts of power. But
that was all the power the United States needed to start the next
phase of the bomb's development.
The pile contained 771,000 pounds of
graphite, 80,590 pounds of uranium oxide and 12,400 pounds of uranium
metal when it went "critical." It cost about $1 million to produce
and build. The pile took the form of a flattened ellipsoid which
measured 25 feet wide and 20 feet high.
June 3 - German scientists fail
to observe neutron multiplication in the reactor in Hamburg.
January - Based on experiments
with a natural uranium reactor, the Germans reject graphite
as a moderator.
July - British 'Maud' Committee reports that a weapon could
be made with 10 kg of U-235; US Academy of Sciences endorses
May - Heisenberg and Dopel observe
the first multiplication of neutrons.
December 2 - First nuclear chain reaction at Chicago's Stagg
Field by Fermi.
March 15 - Oppenheimer moves the
bomb development to Los Alamos.
August 26 - Bohr presents his memorandum
on intentional control of nuclear weapons to Roosevelt.
November - First batch of spent fuel obtained from Hanford reactors.
November - Goudsmit's ALSOS mission obtains documents which
imply that the German's rate of progress toward a bomb had diminished.
January - First Pu reprocessing
production run at Hanford
January 20 - First U-235 separated at Oak Ridge.
June 11- The Franck Report was sent to the Secretary of War.
July 16 - US explodes first atomic bomb, the Trinity test, at
On July 16, 1945, at 5:29:45 AM, a
light "brighter than a thousand suns," filled the valley. As the
now familiar mushroom cloud rose in to the sky, Oppenheimer quoted
from Hindu scripture, the Bhagavad-gita, "Now I am become death,
the destroyer of worlds." The world had entered the nuclear age.
The "Gadget" had a yield equivalent
to 19 kilotons of TNT. "Fat Man," the bomb dropped on Nagasaki was
identical in design to the "Gadget."
August 6,9 - Atomic bombs dropped on
Hiroshima and Nagasaki.
Little Boy Bomb
QuickTimeVR model of the Little Boy Bomb
In essence, the Little Boy design consisted
of a gun that fired one mass of uranium 235 at another mass of uranium
235, thus creating a supercritical mass. A crucial requirement was
that the pieces be brought together in a time shorter than the time
between spontaneous fissions. Once the two pieces of uranium are
brought together, the initiator introduces a burst of neutrons and
the chain reaction begins, continuing until the energy released
becomes so great that the bomb simply blows itself apart.
This is a replica of the bomb that
was dropped over Hiroshima, Japan on August 6, 1945.
QuickTimeVR model of the Fat Man Bomb
The rapid spontaneous fission rate
of plutonium 239 necessitated that a different type of bomb be designed.
A gun-type bomb would not be fast enough to work. Before the bomb
could be assembled, a few stray neutrons would have been emitted,
and these would start a premature chain reaction leading to a great
reduction in the energy released.
Seth Neddermeyer, a scientist at Los
Alamos, developed the idea of using explosive charges to compress
a sphere of plutonium very rapidly to a density sufficient to make
it go critical and produce a nuclear explosion. This is a replica
of the bomb that was dropped over Nagasaki, Japan on August 9, 1945.
Fat Man Specifications
10 feet 8 inches
The Atomic Bomb Cloud over Nagasaki
On August 9, 1945, the American B-29
bomber, Bock's Car left Tinian carrying Fat Man, a plutonium implosion-type
bomb. The primary target was the Kokura Arsenal, but upon reaching
the target, they found that it was covered by a heavy ground haze
and smoke, pilot Charles Sweeney turned to the secondary target
of the Mitsubishi Torpedo Plant at Nagasaki.
Of the 286,00 people living in Nagasaki
at the time of the blast, 74,000 were killed and another 75,000
sustained severe injuries.
World War II ended in Europe on May
8, 1945, less than a month after the death of President Franklin
Roosevelt, but plans for the development and use of atomic weapons
At at 5:29 a.m. on July 16, 1945, the
United States conducted the world's first nuclear test explosion
at Alamogordo, New Mexico. The Nuclear Age was born, a product of
the fear, violence, and suffering of World War II. J.
Robert Oppenheimer, director
of the Los Alamos Laboratory, recalled the following passage
from the Bhagavad Gita upon witnessing the explosion: "I
am become death, the destroyer of worlds"
Within a month, nuclear weapons were
used to destroy the Japanese cities of Hiroshima and Nagasaki.
When he received word of the bombing of Hiroshima, President Truman
exclaimed, "This is the greatest day in history!"