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

The debate on the eve of its birth

In the spring of 1939, nuclear physicists were scrambling to discuss the possibility of the atomic bomb. Niels Bohr, the founder of quantum physics, cited 15 reasons why the fission of the atomic nucleus could not be of practical value. He could not foresee it at the time. The Americans spent 3 years and 2 billion US dollars to defeat his proposal. every impossibility. And Otto Hahn, the man who would win the Nobel Prize for the discovery of nuclear fission, blurted out in a debate with friends in the spring of 1939: "This is against the will of God!"

World War II Science has gone through an "ideal age" before. Cambridge, where Rutherford was, Copenhagen, where Niels Bohr was, and Göttingen, Germany, were the three major centers of physics. They are closely connected with each other, and there is a teacher-instructor relationship that is difficult to distinguish. In this atmosphere, many physics students also studied Latin poetry, and some imaginative ideas could break the rigorous foundation of physics at any time. When Enrico Fermi was lecturing to students, he said: "You can get results by following my method, but please don't ask me about the basis of this method."

In 1933, Göttingen fell into the Nazi In the crisis of ethnic cleansing, Bohr extended an olive branch to his suffering colleagues, and Copenhagen became more lively than before. This year, Einstein moved his home from Berlin to Princeton in the United States.

By the spring of 1939, many of them, especially Jews, had arrived in the United States. Fermi could no longer hold on to his Roman School. His wife was Jewish. They took advantage of the opportunity to receive the Nobel Prize to go abroad in December 1938 and settled in the United States. After the war, many people discussed why the United States and not Germany built the atomic bomb first. This was certainly a crucial factor.

During a visit to the United States in 1939, Bohr leaked the secrets of the atomic bomb. He not only introduced Hahn's work to a New World audience, but also elaborated on the explanations of Meitner and Frisch. One of the audience members, Oppenheimer, later known as the "Father of the American Atomic Bomb" later recalled: "I had the concept of the atomic bomb in my mind at that time." After returning home, Oppenheimer gave a lecture on the explosion. Calculation of critical mass required.

Another scientist, Leo Szilard, tried to get the U.S. government to pay attention to this issue. Through his past relationships in Europe, he learned that there were signs that Germany might have begun research on the atomic bomb. Szilard approached Alexander Sachs, President Roosevelt's informal adviser, who expressed his support. In order to attract the attention of the president, Szilard found Einstein, and Einstein signed the letter to Roosevelt.

On October 11, 1939, Sachs got the opportunity to present the letter to Roosevelt, but the tired president ignored it. They still had a chance to meet the next day. Sacks stayed up all night and finally came up with a persuasive allusion: In the Napoleonic era, the American inventor Fulton once suggested that the emperor build a steam engine-powered fleet so that he could Able to land in England in any weather, Napoleon kicked Fulton out as such a fleet was unheard of. If those in power had known more about science, history would have followed a completely different curve. Roosevelt was convinced, and the U.S. atomic bomb program began. Most of the scientists who were enthusiastic about the project in the early days were from Europe. They were convinced that Nazi Germany had already begun to develop an atomic bomb.

Bohr: The "Double Father" of the Atomic Bomb

In the spring of 2005, a scientific drama staged at a university in Beijing to commemorate the "World Year of Physics" angered some people. An old gentleman in his 80s. Physics historian and translator Gog published two articles criticizing the Chinese version of "Copenhagen" for distorting Bohr's image and demonstrating ignorance of the history of physics. Gog had a special affection for Bohr. He believed that Bohr was not as important to modern physics as Einstein. Unfortunately, Bohr's name has not spread in China, and as time goes by, the glory of this name has been forgotten not only 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. In 1913, Bohr proposed the famous atomic theory. 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 perspective, but also took care of this baby of nuclear physics spiritually: before the atomic bomb was tested, Bohr pointed out that if atomic energy is controlled by the peace-loving people of the world, In hands, this energy will ensure lasting peace in the world; if it is abused, it will lead to the destruction of civilization. After the war, he received the United States' first Peaceful Uses of Atomic Energy Award.

Bohr was of Jewish descent. After Denmark was occupied by Germany, he was trapped in Copenhagen. Bohr's student Heisenberg, the core figure in German atomic energy research, visited Bohr in the autumn of 1941. They cautiously talked about sensitive issues such as the splitting of uranium and nuclear weapons. Heisenberg was recognized as the leader of German nuclear research after the war. In 1939, Fermi tried to persuade Heisenberg to come to the United States, but Heisenberg refused.

After the war, Heisenberg and his supporters argued that while he appeared to be conciliating with those in power during the war, he actually engaged in active resistance, allowing Germany's atomic bomb program to be delayed indefinitely. But according to Gog, such a statement can be refuted by hundreds of facts. "In 1941, Heisenberg visited all the countries occupied by Germany as a special envoy. He was already the director of the Kaiser Wilhelm Institute of Physics. In such a climate, it is difficult to imagine the relationship between Bohr and him. What kind of frank conversation is there?" As the translator of "The Complete Works of Bohr", Goger believed that this conversation deepened Bohr's impression that "Germany's atomic bomb research has begun."

In 1943, knowing that the institute could no longer be saved, Bohr finally ran away. The Royal Air Force placed him in a bomb silo and transported him to the UK like a valuable item. Then he went to the United States. . At this time, the Manhattan Project to develop the atomic bomb had begun for more than a year. Although President Roosevelt said in October 1939: "This matter must be handled urgently." However, the real large-scale funding resolution was not made until December 6, 1941. pass.

The American theoretical physicist Feynman was also in the Manhattan Engineering District at this time. He said wittily: "There were many big names here. After Bohr came to Los Alamos, all of them He has become a nobody.”

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

Oxytocide: Politics

< p> In addition to Oppenheimer, there was another important figure who listened intently to Bohr's lecture on the atomic bomb in 1939, and he was Enrico Fermi.

Fermi was a computing genius. In July 1945, when the shock wave of mankind’s first atomic bomb test explosion reached his location, he threw out the piece of paper in his hand and was blown through it. The power of the atomic bomb was calculated based on the flying distance, and the result was very close to the instrument detection result. But he occasionally failed. When his family moved to the United States in 1939, Mrs. Fermi proposed to install windshields because of the cold. Fermi calculated and found that the role of windshields in raising the indoor temperature was almost negligible, so no windshields were installed. Many months later, the windows were installed because Fermi discovered that he had moved the decimal point to the wrong place in his last calculation.

Fermi's Reactor

After returning home from Bohr's lecture, Fermi explained the meaning to his wife: "To break a uranium atom, a neutron is used. , and then assume that when this uranium atom fission, it releases two neutrons, these two neutrons will hit two other uranium atoms, split them, these two split atoms will emit 4 neutrons, and so on Going forward, we only need a few artificial neutrons for bombardment at first, but eventually the reaction will continue spontaneously until all the uranium atoms are split."

But this is not the case. Still a theory, neutrons are too light and are easily absorbed by any surrounding material, including air and water, which 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, and together they came up with a design that stacked pure graphite (natural carbon) and uranium in layers to create a high The purity of graphite prevents neutrons from escaping. In 1940, the U.S. military gave them 6,000 yuan to purchase graphite, and Fermi and Anderson built piles of graphite in the laboratory.

When the graphite was piled to the ceiling, Fermi began to take the air out of the room, because there were still many neutrons escaping from the air, so Fermi customized a huge iron can. . His friend Herbert Anderson was even more imaginative. He ordered a custom-made square balloon from a rubber company, and had to explain to the rubber company that a square balloon could also fly.

In the winter of 1942, a larger reactor shrouded in balloons stood on the tennis courts of the University of Chicago. On December 2, under the command of Fermi, the cadmium rods that absorbed neutrons were pulled out one after another. The radiation intensity of the reactor was getting higher and higher, and it was releasing potential energy according to human will.

The successful first operation of this reactor greatly boosted official morale. At this time, the Manhattan Project had been officially launched, and Leslie Groves was appointed as the project director. He was an adventurous person. Before Fermi's experiment was successful, Groves started building the reactor. The plan was handed over to DuPont.

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

Competition with Germany

In the fall of 1942, Groves and Oppenheimer met for the first time on a train. Groves had been promoted to brigadier general at this time. Oppenheimer was recommended by Compton and became the director of the largest laboratory in American history. After 1945, one of them was called the "Atomic Bomb General" and the other was called the "Father of the Atomic Bomb." At Oppenheimer's suggestion, Los Alamos, New Mexico, became the site for a new laboratory.

In 1943, Oppenheimer was 40 years old. Although he was already quite famous, he was still far behind his predecessors like Bohr or Compton. But Oppenheimer He made up for this shortcoming with his literary quality and eloquence. The Manhattan Project recruited some of the best nuclear physicists in the United States at the time, and the number of employees at Los Alamos Laboratory soon exceeded 10,000.

In Germany at the same time, the atomic bomb plan was still aborted due to Hitler's self-confidence. In June 1942, Heisenberg reported to the German Minister of Supply that it was theoretically possible to obtain explosive materials from inside the reactor. But after Germany occupied most of Europe, Hitler believed that his blitzkrieg could conquer the world, so he was not interested in any research that could not yield results within 6 months.

However, Americans believed that the Germans had already begun the atomic bomb program, which made the United States feel that they had to move faster. The Manhattan Project quickly expanded to a National People's Congress project with an investment of US$2 billion and more than 150,000 employees. Many projects were hurriedly launched only after they were theoretically proven to be feasible. Groves recalled that he once joked with people that he should buy a house next to Capitol Hill so that he could be ready to face congressional inquiries if the project failed.

In August 1944, physicist Gaudemith and a secret team came to Paris to look for evidence of Germany's development of the atomic bomb. By November 1944, they found enough evidence to show that Germany was at least two years behind the Allies in atomic energy and that Germany did not have the ability to produce an atomic bomb or even the raw materials needed for an atomic bomb. Goldmis told an officer that since Germany did not have an atomic bomb, the Allies could finally stop producing it. The officer's answer surprised him: "Since we have this thing, of course we should use it." In the spring of 1945, Szilard, who was once the proposer of the U.S. atomic bomb program, visited Einstein again, hoping that He signed a new letter seeking to persuade the president of the United States to abandon the use of atomic bombs. Previously, in June 1944, Bohr had met with Roosevelt and Churchill, hoping that they could negotiate with the Soviet Union on atomic energy issues and reach a world peace pattern. Churchill therefore suspected that Bohr was a sympathizer of communism.

While this letter was still lying in the presidential office, Roosevelt died unexpectedly and Truman became president. Did he read the letter signed by Einstein? Nothing is reflected in his memoirs.

The wave of opposition to the use of atomic bombs also spread to Los Alamos. Many scientists involved in the project began to initiate discussions and signatures, but the overall leader of the project, General Groves, was He stood firm on the issue of the use of atomic bombs: "I have always regarded it as my duty to recommend the use of atomic bombs."

No force can stop it. After Germany surrendered, the work rhythm of Los Alamos Instead, it sped up. In the spring of 1945, General Marshall instructed Groves to identify targets for the atomic bomb. The target is no longer Germany, but Japan.

An earth-shattering birth

At 5:30 a.m. on July 16, 1945, the world's first atomic bomb successfully exploded in the desert area of ​​New Mexico, USA. The grains of sand are burned into emerald green glass. Countless works have recorded this moment in epic language.

Every witness has a different mood. Oppenheimer, who had a poetic temperament, suddenly came to mind with an ancient Indian poem: I am the god of death, the destroyer of the world. Carlson Mark was reminded of a debate a few months ago about whether atomic bomb blasts would ignite the atmosphere, and now it looked as if those fireballs would devour everything. Based on the note he dropped, Fermi roughly estimated that the impact of the explosion was equivalent to 20,000 tons of TNT. No scientist had previously estimated its power.

Initially, the scientists ordered a large steel tank and prepared to explode inside the tank to recover most of the precious metals while preventing contamination caused by the spread of the explosive. But when it came to testing, the can, which was between 6 and 14 inches thick, was abandoned because the power of the nuclear explosion, even lower than the 250 tons of explosives estimated by some, was beyond the capabilities of the steel can. After the test explosion, people found that the temperature at the center of the explosion reached 100 million degrees Fahrenheit, which is equivalent to 10,000 times the surface of the sun. If the steel tank was still there, it would be vaporized instantly.

As early as a year ago, Groves, Oppenheimer and others discussed and decided that the first atomic bomb to be tested should be an implosion atomic bomb (they called it "Fat Man") , to detect its complex implosion system. Inside the implosion atomic bomb are two semicircular spheres. When the spheres are brought together and the uranium in the two hemispheres overlap, the critical mass for a chain reaction is reached. There is high explosive on the outside of the sphere. When detonating the atomic bomb, the explosive on the outside is detonated first, and then the explosive generates high temperature and high pressure, which stimulates the spherical plutonium inside. The reason for this method was insufficient raw materials, but it later became a commonly used method: when testing hydrogen bombs, explosives were used to ignite an atomic bomb first, and then the atomic bomb was used to ignite the hydrogen bomb.

Frisch, who figured out how to self-split the atomic bomb, calculated this critical point. This process was not realized by automatic machinery, but by hand. The experiment was therefore full of danger. Frisch was wrong. One died at Los Alamos.

The results of the explosion were quickly sent to the President. At the Potsdam Conference, Churchill realized that Truman had suddenly become tougher. At the meeting, he told the Russians in a more firm tone that certain demands were impossible. Got. He didn't know the answer until July 22, and then he negotiated with Truman and decided to tell Stalin.

However, Stalin's response was relatively dull, which led Churchill to believe that Stalin did not understand the content of their conversation at all. However, a Russian historian named Smirnov recorded the situation like this: “After Stalin came back from the meeting, he told Molotov what Truman told him in front of me. Molotov immediately said: He is raising the price for himself. Stalin smiled and said: Let him raise it, we must talk to Kurchatov about speeding up our work."

Kurchatov was the head of the Soviet nuclear program. With the help of the spy agency, Stalin learned of the news on July 20 or 21. After returning to Moscow, Stalin held a nuclear emergency meeting, and the nuclear competition that had been predicted by many scientists began.

Ending a war, starting a kind of terror

In the 1939 letter to Roosevelt signed by Einstein, there was a technical detail. Experts estimated that the atomic bomb was too powerful. Severely unsuitable for use by aircraft. 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 set many bomber records: it had a bomb load of 9 tons, a range of 6,000 kilometers, the ability to cruise at an altitude of 10,000 meters, and top speed. 600 km/h. Before the emergence of the B-29 bomber, Japan and the United States were separated by the Pacific Ocean and could only engage in a war of attrition at sea. After the B-29 appeared, the war situation changed drastically, and the United States gained air superiority.

In September 1943, the B-29 was selected as the atomic bomb carrier aircraft. At this time, scientists were still unable to determine the shape of the atomic bomb, so the B-29 bomb bay was equipped with an adjustable H-shaped truss and an atomic bomb loading and release system. On February 28, 1944, a B-29 conducted a simulated atomic bomb release test at Muroc Field (later Edwards Air Force Base) in California. By August, 46 B-29s were capable of delivering atomic bombs.

At the same time, crew training is also in progress. This special program was commanded by Colonel Paul Tibbetts, who had extensive experience flying B-17s in Europe and North Africa and was directly involved in the test flights of the B-29.

The little boy shows off his power

Everything is ready. On July 25, 1945, Truman made an important decision to use atomic bombs against Japan if Japan refused to accept the Potsdam Declaration.

The US military initially targeted 17 cities. Groves was personally responsible for selecting bomb targets, and Hiroshima was ultimately selected as the first choice. Hiroshima was an important military fortress and the largest city in Japan, excluding Kyoto, that was not subject to U.S. air raids at that time.

On the morning of August 5, 1945, there were signs that the weather would be good the next day. In the afternoon, on Tinian Island, the atomic bomb "Little Boy" was lifted and installed in place by a hydraulic ladder. The bomb's casing is made of black steel and weighs 4,400 kilograms, resembling "an extended fin-shaped trash can." "Little Boy" was equipped with radar, timer and barometer, then mounted on the bomber and secured with chains.

At 0:00 on the 6th, the final instructions were issued.

The "Enola Gay" *** carrying out the mission has 20 crew members, including ground crew. The pilot was Captain Tibbets, the bombardier was Major Ferebee, the ordnance engineer was Captain Parsons, and the electronics officer was Captain Jeppesen. The huge bomber was silver in color, with a 43-meter-long wing and a dazzling name on the fuselage - Enola Gay, named after Colonel Tibbets' mother.

Tibbets reminded crew members to use goggles. According to the weather forecast, Hiroshima will dawn windy and sunny. Since they had to set off at 2:45 in the morning, they didn't sleep well. At 2:27, the engine started. The aircraft was carrying 6,800 kilograms, which was a bit overweight, but it successfully passed the two-mile runway. Over Saipan, Parsons and Jepson climbed into the cabin to complete the assembly of the bomb. At 8:50 a.m., they entered Japanese airspace at an altitude of 9,500 meters, very close to Hiroshima.

Residents of Hiroshima saw the two planes but did not take them seriously. Some people were walking on the street as usual. At 8:15 a.m. Hiroshima time, the timer and barometer pulled the trigger, and the atomic bomb exploded.

Before taking off, the pilot asked a scientist how to leave the bombing point as quickly as possible. The answer was to make the sharpest possible turn and fly away from the target along a tangent line. So when the atomic bomb exploded 1,000 meters above Hiroshima, the bomber was already 11 miles away, but it was shaking and creaking as if it had been hit by anti-aircraft fire.

Tibbets recalled, "The Hiroshima bomb did not form a mushroom cloud. What it formed was what we call a string. It shot up, pitch black, with light and color, and white light in it. and gray, with the top like a folded-up Christmas tree.” Another pilot compared the scene to “a pot of burning black oil.”

After the explosion there was deathly silence. What followed was a hellish scene: the temperature reached 2980 degrees Celsius, the victims near the explosion evaporated instantly, the comatose survivors walked as if they were sleepwalking, and their torn skin hung like rags on the flesh. Wooden houses, parks, and trees burned in violent explosions. Burnt bodies floated in the river. In an instant, the city of Hiroshima ceased to exist.