Physicist szilard is an old friend of Einstein. After escaping from Nazi clutches, he went to Columbia University in new york to study how to produce a chain reaction. 1939, when szilard heard the news of uranium fission, he realized that uranium could be used to realize a potentially explosive chain reaction. He found Einstein and discussed the possibility with him. Einstein said, "I never thought about it!" " They were also worried that the Germans might buy out Congo's uranium, so they decided to ask Einstein to write a letter to the State Council. A few days later, under the arrangement of a friend, szilard met with saxophone, an economist and a friend of Roosevelt Jr., and saxophone insisted on giving this letter directly to the President, who wanted to hand it in himself. However, after Sachs got Einstein's signature letter and officially handed it to Roosevelt, he couldn't find the opportunity to submit it for almost two months. 1939 At the end of August, the Nazis signed a war alliance treaty with the Soviet Union, further dividing Poland and shocking the world. 193910 June1kloc-0/,saxophone was finally led into the oval office, with Einstein's letter in his hand. He stood at Roosevelt's desk and read some letters from Einstein aloud. The following is part of this letter: Sir, I learned about the recent work of Fermi and szilard from their manuscripts, which makes me feel that uranium may become an important new energy source in the near future. Some aspects of this situation seem to need close attention, and if necessary, they should act quickly. Therefore, I think it is my duty to draw your attention to the following information and suggestions: … It will be possible to establish a chain reaction of nuclei in a large amount of uranium, which will produce a lot of energy and a lot of new elements like radium. Now it seems almost certain that it will be completed in the near future. This new phenomenon can also be used to make bombs, and it is conceivable-although it is still uncertain-that a very powerful new type of bomb can be made with it. As long as this type of bomb is transported out and explodes in the port, it will probably destroy the whole port and some areas around it ... In view of this situation, you may think it is desirable to keep in touch with physicists who have a chain reaction in the United States. The letter ended with a warning that German scientists might be developing such a bomb. After listening to the letter, Roosevelt Jr. announced, "We need to act." That night, Roosevelt set up a committee and made a plan. 1On October 26th, the Committee held its first informal meeting in Washington, but Einstein didn't attend. The second letter in the following months, the atomic bomb project progressed slowly, and only $6,000 was approved for graphite and uranium experiments. Szilard was very anxious, because he believed that the chain reaction was feasible, so he found Einstein again in March 1940, and they wrote a second letter to President Roosevelt. In the letter, they warned that various kinds of uranium research are being carried out in Berlin, and breakthroughs are being made in the research of producing huge explosions through chain reactions, so they asked the President to investigate whether the work in the United States is progressing fast enough. After reading the letter, Roosevelt called a meeting and invited Einstein to attend, but Einstein didn't want to get involved too much. He said he had a cold and didn't attend in the end. But he said: "This work can only be carried out at a faster speed and on a larger scale under certain conditions. I believe it is wise and urgent to create these conditions. 194 1 February 6, 2008, more than two years after Einstein wrote his first letter to the president, the United States launched the top secret project "Manhattan Project". With many physicists disappearing into remote towns, Einstein guessed that the work he suggested to study the atomic bomb was under intense pressure. He was not invited to join the project, nor was he officially told. 1944 The third letter at the end, Einstein, a friend who secretly participated in the Manhattan project, was convinced that the plan would be successful and visited Einstein. They all believe that whether the atomic bomb is used in war or not, the nature of war and peace will change forever. 1945 In March, szilard expressed the same concern when he visited Einstein. Since Germany obviously failed to develop an atomic bomb, why did the United States wait until later to build it? Therefore, Einstein wrote a third letter to President Roosevelt. Unfortunately, President Roosevelt didn't read the letter. After his death on April 12, this letter was found in his office and handed over to his successor, President Truman. Truman gave it to Secretary of State Burns. Although szilard finally met Burns, he was unmoved. 1On August 6th, 945, an atomic bomb named Little Boy was dropped on Hiroshima. Einstein, who was drinking tea that afternoon, heard the news. " "My God!" This is the only thing he said after he learned the news. Three days later, another atomic bomb "Fatty" was dropped on Nagasaki.