Nagasaki, nuclear bomb

This year there were completed the first three atomic (or nuclear) bombs. The first bomb was successfully exploded in the New Mexico desert on July 16, 1945, and a second over Hiroshima, Japan on Aug 6, 1945, and the third over Nagasaki on Aug 9, 1945. The bombs were of Fission Type and of tens of kilotons (thousands of tons of TNT equivalent) (Vol 1 of Encycl, p A499-L)... 

The nuclear bombs over Hiroshima and Nagasaki, and the later atmospherical detonations created a new type of soil problems. Radioactive elements in the air came with time into the soil, were later taken up by the plants and thus became dangerous in animal and human nutrition. 

The detonation of nuclear bombs over Hiroshima and Nagasaki in August 1945 during World War II led to the immediate deaths of approximately 200,000 people, primarily civilians, as well as lasting injury and later death of many others and massive devastation - and widespread radioactive contamination - of the environment in these two cities [5], In addition to the potential for the use of nuclear weapons by national armed forces, such as that described in the recent U.S. Nuclear Posture Review, which threatened use of nuclear weapons under a wider range of circumstances, there is an increasing threat of their use by individuals and groups [6]. 

Einstein s letter convinced Roosevelt, and in 1941 he assembled the resources to begin the costliest scientific project ever attempted. The top-secret endeavor was called the Manhattan Project and its main goal was to build an atomic bomb before the Germans did. The project was led by physicist J. R. Oppenheimer (1904-1967) at a high-security research facility in Los Alamos, New Mexico. Eour years later, on July 16,1945, the world s first nuclear weapon was successfully detonated at a test site in New Mexico. The first atomic bomb exploded with a force equivalent to 18,000 tons of dynamite. Ironically, the Germans—who had not made a successful nuclear bomb— had already been defeated by this time. Instead, the United States used the atomic bomb on Japan. One bomb was dropped on Hiroshima and a second bomb was dropped on Nagasaki. Together, the bombs killed approximately 200,000 people and led to Japan s surrender. 

In a nuclear weapon, the fissile material is initially subcritical. The challenge is to produce a supercritical mass so rapidly that the chain reaction takes place uniformly throughout the metal. Supercriticality can be achieved by shooting two subcritical blocks toward each other (as was done in the bomb that fell on Hiroshima) or by implosion of a single subcritical mass (the technique used in the bomb that destroyed Nagasaki). A strong neutron emitter, typically polonium, helps to initiate the chain reaction. 

Unlocking the secrets of the nucleus was a mixed blessing, for in addition to our understanding of the sun, we also acquired nuclear weapons of immense desfructive potential. The bombing of Hiroshima and Nagasaki with nuclear weapons was one of the last acts of the Second World War but the beginning of the nuclear dilemma More than 50 years later, controversies still rage over how society should use the fruits of nuclear science. 

The potential of nuclear fission was first realized in the atomic bomb. In 1945, the United States dropped two bombs of unprecedented power, one on Hiroshima and the other on Nagasaki, Japan. Both were fission weapons. 

II. On August 6, 1945, an atomic bomb (nicknamed as Little Boy ) was dropped by an American B-29 bomber (Enola Gay) over Hiroshima, Japan instantly killing more than 70000 people. On August 9, 1945, the USA dropped a second atomic bomb (nicknamed Fat Man ) killing some 40000 people in Nagasaki, Japan. Because of this large-scale devastation, such nuclear explosive devices have never again been used in a war. 

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