How was the atomic bomb invented?

On the eve of the outbreak of World War II, Hungarian physicist szilard, who was exiled to the United States, learned that Germany was stepping up its research on the chain reaction of nuclear fission and banned the export of uranium ore from the occupied Czech Republic, and immediately realized that Germany might be developing an atomic bomb. If a war maniac like Hitler had an atomic bomb, the future of mankind would be unimaginable.

szilard and two other physicists immediately found Albert Einstein, hoping that he would write to the President of the United States with his prestige and persuade the American government to start the development of the atomic bomb as soon as possible. Einstein agreed with them and signed the letter drafted by szilard, and entrusted Alexander Sachs, a friend and adviser of President Roosevelt, to hand over the letter of request signed by three scientists to President Roosevelt. In the letter, in view of the study of chain reaction in Germany, three scientists unanimously proposed that "the US government should keep in constant contact with American physicists who study chain reaction".

It is said that President Roosevelt didn't care about this matter at first, only said, "This is an interesting idea, but now the government has no energy to consider it.". Seeing that the president had no intention of supporting this matter, Sachs was very anxious and spent the whole night thinking about how to persuade Roosevelt. The next day, at breakfast with Roosevelt, Sachs said this: "During Napoleon's reign, a young American inventor Fulton came to the French emperor and suggested building a fleet of steam engine ships. He said that such a fleet can land in Britain in any weather. Can a warship go without sails? This was incredible to the great Corsican (Napoleon), so he turned Fulton out. According to the comments of Sir acton, a British historian, this can be said to be a famous example that Britain was spared because of the enemy's lack of knowledge. If Napoleon had used his brain a little and considered it carefully, the historical process of the 19th century might have been completely different. " The story really touched President Roosevelt. He immediately called his entourage and ordered the relevant government agencies to form a uranium advisory Committee.

on December 6, 1941, the day before the Japanese attack on pearl harbor, the U.S. government formally decided to implement the plan to manufacture atomic weapons. The project was named "Manhattan Project" because of the location of its first headquarters. Robert Oppenheimer, a famous American theoretical physicist, and Brigadier General leslie groves became the partners to lead this great project that opened up the atomic age of mankind. Brigadier General groves was in charge of building the Pentagon in a very short time. Although he was not very clear about the nature and significance of this "Manhattan Project", he was told: "If you do your job right, you will win the war." Now he is required to use his excellent engineering coordination ability to coordinate the work of 1 thousand staff, 37 facilities in 13 States and laboratories in 12 universities; Dr Oppenheimer was in charge of scientific leadership and led thousands of senior researchers to a secret base surrounded by walls near Los Alamos, New Mexico.

Enrico Fermi, an outstanding Italian nuclear physicist who fled to the United States and settled down because of the persecution of fascism, also joined the Manhattan Project. He led the construction of the first atomic reactor in the United States at the University of Chicago, which provided a lot of useful data for the development of atomic bombs. However, there are still many technical difficulties in making nuclear bombs. The most important problem is the purification of uranium. At that time, researchers generally believed that the best nuclear fission material was uranium 235. However, the natural content of this uranium is very low, accounting for only .7%, so chemical separation must be carried out in some way to obtain high-content uranium 235. The U.S. government decided to spare no expense and adopt various methods to conduct experiments at the same time in order to separate enough high-purity uranium-235 as soon as possible. However, due to the high cost of uranium separation and the discovery of a new element, plutonium-239, which evolved from uranium-238, it is also a good nuclear transformation material. Therefore, a large amount of uranium-238 left in the separation test can be used to make plutonium.

In p>1943, "Manhattan Project" entered the specific design stage. In the spring of 1945, three atomic bombs were built by scientists.

At 5: 3 on July 16th, 1945, deep in the desert of Los Alamos, New Mexico, the work of "Manhattan Project" reached its climax in a violent explosion with dazzling light. In an underground observation room about 1 kilometers above the ground, Dr. Oppenheimer saw the mushroom cloud rising after the successful test explosion of the world's first uranium atomic bomb, and could not help sighing silently: "I became a god of death, the destroyer of the world." According to experts' calculations, the explosive power of this atomic bomb is equivalent to 2, tons of TNT.

The successful trial-production of the atomic bomb in the United States in less than four years depends entirely on two factors: First, Hitler sent a large number of extremely talented European nuclear physicists to the United States, gathering the most powerful team of scientists in the world for the United States; Second, in order to complete the "Manhattan Project", the US government invested huge manpower and material resources: more than 5, people were mobilized to participate in the experiment, which cost 2.2 billion US dollars and occupied nearly one third of the country's electricity. The successful development of the atomic bomb is a typical example of scientific cooperation in the 2th century.

in may p>1945, after Germany announced its unconditional surrender, people realized that although Germany has been engaged in the development of atomic bombs, it is still far from being able to really make them. Their facilities for developing nuclear reactors have been repeatedly destroyed by allied forces and resistance organizations, and it is impossible to concentrate on making atomic bombs. At this time, scientists who had suggested building atomic bombs began to call for the prohibition of the use of nuclear weapons. But once the scientific theory becomes a reality, scientists can't change its fate at all. In June, seven scientists, including szilard, who initiated the development of the atomic bomb, jointly wrote to the US Secretary of Defense, pointing out that the existence of the atomic bomb would lead to a nuclear arms race among the world's military powers; In July, szilard drafted an urgent petition letter to the White House (the official residence of the President of the United States, which later became the representative of the American government) ... < P > But all this didn't help-on August 6 and 9, 1945, the American government dropped two atomic bombs on Hiroshima and Nagasaki, respectively. Since then, the nuclear arms race between several military powers in the world has begun for nearly half a century!