Can history be rewritten? What are the consequences of rewriting?

1939 in the spring, nuclear physicists scrambled to discuss the possibility of an atomic bomb. Niels bohr, the founder of quantum physics, cited 15 reasons to show that nuclear fission cannot be of practical value. At that time, he could not foresee that it took Americans three years and 2 billion dollars to overcome every impossibility he proposed. Otto hahn, who won the Nobel Prize for discovering nuclear fission, blurted out in the debate with friends in the spring of 1939: "This is against God!"

Before World War II, science experienced an "ideal era". Cambridge, where Rutherford is located, Copenhagen, where niels bohr is located, and G? ttingen, Germany, are all three centers of physics. They are closely related, and there is an indistinguishable relationship between teachers and students. In this atmosphere, many physics students also study Latin poetry, and some imaginative ideas will break the rigorous cornerstone of physics at any time. When giving lectures to students, Enrico Fermi said, "You can get the results according to my method, but please don't ask me the basis of this method."

1933, gottingen was caught in the crisis of Nazi ethnic cleansing, and Bohr extended an olive branch to his suffering colleagues. Copenhagen is more lively than before. This year, Einstein moved his family from Berlin to Princeton, USA.

By the spring of 1939, many of them, especially Jews, came to the United States. Fermi can no longer keep his Roman school. His wife is Jewish. They went abroad on 1938 and 12, and took advantage of the Nobel Prize to settle in the United States. After the war, many people discussed why the United States, not Germany, made the atomic bomb first, which must be a crucial factor.

Bohr revealed the secret of the atomic bomb during 1939' s visit to the United States. He not only introduced Hahn's work to the audience in the new world, but also expounded the explanations of Mesner and Frith. Oppenheimer, a listener who was later called "the father of American atomic bomb", later recalled: "I had the concept of atomic bomb in my mind at that time." After returning home, Oppenheimer calculated the critical mass required for the explosion.

Another scientist, Leo Szilard, tried to draw the American government's attention to this issue. Through his past relations in Europe, he learned that there are signs that Germany may have begun to study atomic bombs. Szilard found Alexander Sachs, an informal adviser to President Roosevelt who supported him. In order to attract the president's attention, szilard found Einstein again, and Einstein signed the letter to Roosevelt.

On June1939101day, saxophone got the opportunity to present this letter to Roosevelt, but the tired president ignored it. The next day, they had a chance to meet again. Saxophone stayed up all night and finally came up with a convincing story: In the Napoleonic era, the American inventor Fulton suggested that the emperor build a fleet powered by a steam engine, so that he could land in England in any weather. Napoleon drove Fulton away because he had never heard of such a fleet. If those in power can learn more about science, history will develop along a completely different curve. Roosevelt was persuaded by him, and the American atomic bomb program began to start. Most of the scientists who were enthusiastic about this project in the early days came from Europe. They are convinced that Nazi Germany has begun to develop atomic bombs.

Bohr: the "double father" of the atomic bomb

In the spring of 2005, an 80-year-old gentleman was annoyed by a scientific drama staged by a university in Beijing to commemorate the "World Physics Year". Gog, a physics historian and translator, published two articles accusing China's Copenhagen of distorting Bohr's image and showing his ignorance of the history of physics. Gog has a special affection for Bohr. He thinks Bohr is no less important to modern physics than Einstein. Unfortunately, Bohr's name not only didn't spread in China, but with the passage of time, the glory of this name was not only forgotten by the public, but also by many physicists.

If we must find a godfather for the atomic bomb, Bohr is undoubtedly the most suitable candidate. 19 13, Bohr put forward the famous atomic theory, and his research on the atomic structure model won him the 1922 Nobel Prize in Physics. Bohr not only provided the most basic theory for the birth of the atomic bomb from a scientific point of view, but also took care of the baby of nuclear physics mentally: before the atomic bomb test, Bohr pointed out that if atomic energy is in the hands of peace-loving people in the world, this energy will ensure lasting peace in the world; If abused, it will lead to the destruction of civilization. After the war, he won the first American prize for the peaceful use of atomic energy.

Bohr is descended from Jews. He was trapped in Copenhagen after Denmark was occupied by Germany. Bohr's students, Heisenberg, the core figure of German atomic energy research, visited Bohr in the autumn of 194 1, and they talked cautiously about sensitive issues such as uranium fission and nuclear weapons. Heisenberg is recognized as the leader of nuclear research in Germany after the war. Fermi tried to persuade Heisenberg to go to America on 1939, but Heisenberg refused.

After the war, Heisenberg and his supporters defended that he made peace with the authorities on the surface during the war, but actually actively resisted, that is, postponed Germany's atomic bomb plan indefinitely. But in Gog's view, this statement can be refuted by hundreds of facts. "194 1 year, Heisenberg visited all the countries occupied by Germany as a special envoy. At that time, he was already the director of Caesar William Institute of Physics. In such a climate, it is hard to imagine any frank dialogue between Bohr and him. " As a translator of Bohr's complete works, Gog believes that this conversation has deepened Bohr's impression that "Germany's research on atomic bombs has begun".

1943, Bohr finally ran away, knowing that the institute could never be saved. The Royal Air Force put him in a bomb box and shipped him to England like a valuable item, and then he went to the United States. At this time, the Manhattan project to develop an atomic bomb has been launched for more than a year, although President Roosevelt said in 1939 and 10: "This matter should be dealt with urgently." However, the real large appropriation resolution was not passed until194165438+February 6.

Feynman, an American theoretical physicist, is also in the Manhattan project area at this time. He quipped: "There used to be a lot of big names here. Bohr has become a villain since he came to Los Alamos. "

But Bohr did not bring any new impetus to the American atomic bomb program. After the war, Wheeler recalled: "Bohr came to the United States not to help us build the atomic bomb, but to make suggestions on the consequences of using the atomic bomb."

Oxytocin: Politics

In addition to Oppenheimer, another important person listened attentively to Bohr's speech on the atomic bomb in 1939. He is Enrique Fermi.

Fermi is a calculating genius. 1945 In July, when the shock wave of the first atomic bomb test reached his position, he threw the paper in his hand and calculated the power of the atomic bomb by the distance the paper was blown away. The results are very close to the instrument test results. But he misses occasionally. 1939 when his family moved to the United States, Mrs Fermi suggested installing a windshield because of the cold. Fermi found that the effect of windshield on improving indoor temperature was almost negligible after calculation, so no windshield was installed. A few months later, the window was installed, because Fermi found that his final calculation had moved the decimal point in the wrong position.

Fermi reactor

After going home from Bohr's lecture, Fermi explained the significance to his wife: "It takes a neutron to break a uranium atom, and then suppose that this uranium atom will release two neutrons when it splits, and these two neutrons will hit the other two uranium atoms and split them, and these two split atoms will emit four neutrons. If this continues, we only need a few artificial neutrons to bombard at first, but in the end this reaction will continue spontaneously. "

But this is still a theory. Neutrons are too light to be absorbed by anything around them. Air and water can easily capture them before they hit the nucleus. Colleagues and friends joined in, including Leo Szilard, who suggested using carbon to slow down neutrons. Together, they put forward a design in which pure graphite (natural carbon) and uranium are stacked layer by layer, and high-purity graphite can prevent neutrons from escaping. 1940, the US military gave them 6000 yuan to buy graphite, and Fermi and Anderson piled graphite in the laboratory.

When the graphite piled up to the ceiling, Fermi began to want to pump out the air in the room, because there were still many neutrons escaping from the air, so Fermi customized a huge tin can. His friend Herbert Anderson is more imaginative. He ordered a square balloon from a rubber company, so he had to explain to the rubber company that a square balloon can fly.

1942 In the winter, a larger balloon reactor stood on the tennis court of the University of Chicago. On February 2, 65438, under Fermi's command, the cadmium rod that absorbed neutrons was pulled out, and the radiation intensity of the reactor became higher and higher, releasing potential energy according to human will.

The first successful operation of the reactor greatly boosted the morale of officials. At this point, the Manhattan Project was officially launched, and leslie groves was appointed as the project director. He is an adventurous man. When Fermi's experiment was unsuccessful, groves handed over the plan to build a reactor to DuPont.

In the manufacturing process of the world's first atomic bomb, many projects were carried out in this unusual way.

Competition with Germany

1942 autumn, groves and Oppenheimer met for the first time on the train. At this time, groves has been promoted to brigadier general, and Oppenheimer has been recommended by Compton as the director of the largest laboratory in American history. After 1945, one was called "General of Atomic Bomb" and the other was called "Father of Atomic Bomb". At the suggestion of Oppenheimer, Los Alamos, New Mexico became the location of the new laboratory.

1943, Oppenheimer is 40 years old. Although he is famous, he is still far from Bohr or Compton, but Oppenheimer made up for this deficiency with his literary accomplishment and eloquence. Manhattan Project Luo Zhi recruited one of the best nuclear physicists in the United States at that time, and the staff of Los Alamos Laboratory soon exceeded 10000.

At the same time, in Germany, the atomic bomb plan was aborted because of Hitler's confidence. 1In June, 942, Heisenberg reported to the German Minister of Supply that theoretically, it was completely possible to obtain explosive substances from the inside of the reactor. But after Germany occupied more than half of Europe, Hitler thought that his blitzkrieg could conquer the world, so he was not interested in all the research that could not produce results within six months.

But Americans believe that the Germans have started the atomic bomb program, which makes the United States feel that it is necessary to speed up. Manhattan Project has rapidly expanded into a national people's congress project with an investment of US$ 2 billion and more than 65.438+0.5 million employees. Many projects are hastily launched only when they are proved feasible in theory. Groves recalled that at that time, he joked that he should buy a house next to Capitol Hill in case the project failed, so that he could be ready for the question from Congress.

1944 In August, physicist Goldsmith and a secret team came to Paris to look for evidence that Germany had developed an atomic bomb. By June 1944 1 1, they had found enough evidence to show that Germany was at least two years behind its allies in atomic energy, and Germany could not make atomic bombs or even the raw materials needed for atomic bombs. Goldsmith told an officer that because there were no atomic bombs in Germany, the allies could finally stop producing atomic bombs. The officer's answer surprised him: "since you have this thing, of course you have to use it."

1945 In the spring, szilard, once a supporter of the American atomic bomb program, visited Einstein again, hoping that he would sign a new letter, which tried to persuade the President of the United States to give up using the atomic bomb. Previously,1June, 944, Bohr met with Roosevelt and Churchill, hoping that they could negotiate with the Soviet Union on the issue of atomic energy and reach a world peace pattern. Churchill therefore suspected Bohr was a sympathizer of * * *.

While this letter was still lying in the Oval Office, Roosevelt died unexpectedly and Truman became president. Has he read the letter signed by Einstein? It's not even in his memoirs.

The wave of opposition to the use of the atomic bomb also swept to Los Alamos, and many scientists involved in the project began to initiate discussions and signatures, but the general manager of the project, General groves, stood firm on the issue of using the atomic bomb: "I have always regarded it as my duty to suggest the use of the atomic bomb."

Nothing can stop it. After Germany surrendered, the pace of work in Los Alamos accelerated. 1in the spring of 945, General Marshall instructed groves to determine the dropping target of the atomic bomb. The target is no longer Germany, but Japan.

Earth-shattering birth

1945 at 5: 30 am on July 6, the world's first atomic bomb exploded successfully in the desert area of New Mexico, USA. The explosion burned the sand within 800 meters of Fiona Fang into green glass. Countless works have recorded this moment in epic language.

Every witness has a different mood. Oppenheimer, a poet, suddenly remembered an ancient Indian poem: I am a god of death, the destroyer of the world. Carlson Mark remembered an argument a few months ago, that is, whether the atomic bomb would ignite the atmosphere. Now it seems that those fireballs will devour everything. Fermi estimated that the impact of the explosion was equivalent to 20,000 tons of TNT according to the note he spilled. No scientist has estimated its power before.

At first, scientists ordered a large steel tank to explode, so as to recover most precious metals and prevent the spread of explosives from causing pollution. But when it comes to testing, the tank with a thickness of 6 to 14 inch is abandoned, because even if the power of nuclear explosion is lower than the power of 250 tons of explosives estimated by some people, it is unbearable for steel tanks. After the test explosion, it was found that the temperature in the explosion center reached 1 100 million degrees Fahrenheit, which was equivalent to 1 10,000 times of the surface of the sun. If the steel can is still there, it will vaporize instantly.

As early as a year ago, groves and Oppenheimer decided that the first atomic bomb to be tested should be an implosion atomic bomb (they called it "Fat Man") to test its complex implosion system. Inside the implosion atomic bomb are two semi-circular spheres. When the spheres are together and the uranium in the two hemispheres overlaps, the critical mass of the chain reaction is reached. Outside the sphere is high explosive. When an atomic bomb is detonated, the explosive outside is detonated first, and then the explosive generates high temperature and high pressure to stimulate the spherical plutonium inside. This method was adopted because of the shortage of raw materials, but it later became a widely used method: when testing hydrogen bombs, an atomic bomb was first ignited with explosives, and then the hydrogen bomb was ignited with the atomic bomb.

Frith, who came up with the way of atomic bomb self-splitting, calculated this critical point. This process is not realized by automatic machinery, but by hand. So the experiment was full of danger, and Fries almost died in Los Alamos.

The result of the explosion was quickly sent to the president. At the Potsdam meeting, Churchill realized that Truman had suddenly become tougher and told the Russians in a firmer tone that some demands were impossible. He didn't know the answer until July 22, and then he negotiated with Truman and decided to tell Stalin.

But Stalin's reaction was relatively dull, which made Churchill think that Stalin didn't understand their conversation at all. However, a Russian historian named smirnoff wrote down the situation at that time: "After Stalin came back from the meeting, he told Molotov what Truman said to him in front of me. Molotov immediately said: He is raising the price for himself. Stalin said with a smile: Let him carry it, we must talk to kurchatov about speeding up the work.

Kurchatov is the head of the Soviet nuclear program. With the help of the spy agency, Stalin learned the news on July 20 or 2 1. After returning to Moscow, Stalin called an emergency nuclear conference, and the nuclear race predicted by many scientists began.

End a war and start a terror.

There is a technical detail in the letter signed by Einstein to Roosevelt in 1939. Experts estimate that the atomic bomb is too heavy to be dropped by plane. But by 1940, this problem was solved, because the Boeing B-29 heavy bomber was born.

The B-29 super bomber was the largest and most successful bomber in World War II. It has set the highest number of bombers: the bomb load is 9 tons, the range is 6,000 kilometers, and it can cruise at an altitude of 10,000 meters and the speed is 600 kilometers per hour. Before the B-29 bomber appeared, Japan and the United States could only engage in a war of attrition across the Pacific Ocean. After the appearance of B-29, the war situation changed greatly, and the United States mastered the air superiority.

1943 In September, B-29 was selected as the atomic bomb carrier. At this time, scientists are still unable to determine the shape of the atomic bomb, so the B-29 bomb bay is equipped with an adjustable H-truss and an atomic bomb loading and releasing system. 1On February 28th, 944, B-29 conducted a simulated dropping test of an atomic bomb at Mullock Airport (later Edwards Air Force Base) in California. By August, 46 B-29s had the ability to drop atomic bombs.

At the same time, the training of the crew is also intense. This special project was commanded by Colonel paul tibbets, who had experience in piloting the B- 17 in Europe and North Africa and directly participated in the test flight of the B-29.

The little boy exploded.

Everything is ready. 1On July 25th, 945, Truman made an important decision that if Japan refused to accept the Potsdam Proclamation, it would use an atomic bomb against Japan.

The initial airdrop targets of the US military were as many as 17 cities. Groves was personally responsible for choosing the target, and Hiroshima was finally chosen as the first choice. Hiroshima is an important military fortress and the largest city in Japan that was not attacked by the United States except Kyoto at that time.

On the morning of August 5th 1945, there were signs that the next day would be fine. In the afternoon, in Tianning Island, the atomic bomb "Little Boy" was hoisted and installed by a hydraulic ladder. The shell of this bomb is made of black steel plate and weighs 4400 kilograms, just like "an extended fin trash can". The "little boy" is equipped with radar, timer and barometer, and then installed on the bomber and fixed by chain.

At 0: 00 on the 6 th, the final order was issued.

The "Ennola guy" on the mission has 20 crew members, including the ground crew. The pilot is Colonel Tibbets, the bomber is Major Ferreby, the ordnance engineer is Colonel Pasan, and the electronic technical officer is Captain jepson. The huge bomber is silver, its wings are 43 meters long, and its name on the fuselage is dazzling-Enolagay, named after Colonel Tibbets's mother.

Tibbets reminded the crew to use goggles. According to the weather forecast, it is windy and sunny at dawn in Hiroshima. They didn't sleep well because they had to leave at 2: 45 in the morning. At 2: 27, the engine started, and the plane weighed 6800 kilograms, which was a little overweight, but it successfully passed the two-mile runway. In Saipan, Parsons and jepson climbed into the cabin to complete the bomb assembly. At 8: 50 in the morning, they entered Japanese airspace at an altitude of 9500 meters, which is very close to Hiroshima.

Residents of Hiroshima saw two planes, but they didn't care. Someone is walking in the street as usual. At 8 am Hiroshima time, the timer and barometer pulled the trigger and the atomic bomb exploded.

Before take-off, the pilot asked a scientist how to leave the launch site as quickly as possible, and the answer was to turn as sharply as possible and fly off the target along the tangent. So when the atomic bomb exploded over Hiroshima 1000 meters, the bomber had already flown to 1 1 miles away, but it seemed to be hit by an anti-aircraft gun, wobbling and creaking.

Tibbets recalled, "The Hiroshima atomic bomb did not form a mushroom cloud. What it forms is what we call a string. It rushed up, black, bright and colorful, with white light and gray inside and a folded Christmas tree at the top. " Another pilot compared this scene to "a pot burning with black oil".

There was a dead silence after the explosion. Next, the hellish scene is terrible: the temperature is as high as 2980℃, the victims near the explosion evaporate instantly, the survivors in coma walk like sleepwalkers, and the torn skin hangs like rags on the meat. In the violent explosion, wooden houses, parks and trees are burning. There are charred bodies floating in the river. In an instant, Hiroshima ceased to exist.