The atomic Bomb code named The Manhattan Project was
             the first atomic Bomb created by the United States. The United
             States supervised the development of the atomic bomb, under
             the code name Manhattan Project, during World War II. The
             first sustained nuclear chain reaction was achieved in
             December 1942 at the University of Chicago under the direction
             of Arthur Holly Compton. Key members of the research team
             were Enrico Fermi and J. Robert Oppenheimer. Shortly after
             the first bomb test was completed, atomic bombs were dropped
             on the Japanese cities of Hiroshima (Aug. 6, 1945) and Nagasaki
             The atomic bomb, which was developed secretly in the
             United States during World War II, differed from all earlier
             types of bombs. It contained radioactive substances that
             underwent very rapid changes under certain conditions,
             releasing immense quantities of light and heat.
             For an atom bomb to explode, its radioactive ingredients,
             an isotope of uranium called U-235 must be present in a large
             quantity. The name of this quantity is called a critical mass.
             The exact details of the bomb's construction remain secret, but
             it probably contains two different quantities of radioactive
             material that are brought together mechanically to form a
             critical mass and then they will explode it.
             An atomic bomb works by means of fission, a process in
             which unstable atoms split and eventually form stable, smaller
             atoms. The other main type of nuclear bomb is the hydrogen
             bomb, works by fusion, with small atoms combining into larger
             ones. A hydrogen bomb, which is far more powerful than an
             atom bomb, uses isotopes of hydrogen. The final reactions do
             not involve a critical mass, and so the bomb size and energy
             When Hiroshima was hit by the atomic bomb it all that
             could be seen was a noisless Flash. Hiroshima was a port city at
             southwest end of Honshu Island founded in the 16th
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