An atomic bomb is a bomb in which the splitting of atomic nuclei results in an explosion of tremendous force and heat, accompanied by a blinding light. The destructive force of an atomic bomb is due to nearly instantaneous and uncontrolled successive fissions of uranium or plutonium atoms in a chain reaction, each fission releasing tremendous energy and also neutrons which produce the succeeding fission (The World Book Dictionary 129). In other words, these bombs are very powerful. This was demonstrated in 1940, when we dropped an Atomic Bomb on Hiroshima during World War II. This bomb left a crater, in the ground, that was over a half of a mile long. One of the first instances that these bombs