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The atomic bomb


The atomic bomb
The world of the atom is so fantastic that it requires understanding of the root breaking habitual concepts of space and time. Atoms are so small that if a drop of water can be increased to the size of the Earth, each atom in the drop would be less orange. In fact, one drop of water is 6,000 billion billion (6000000000000000000000) hydrogen and oxygen atoms. And yet, despite its tiny dimensions, the atom has a structure somewhat similar to the structure of our solar system. It boggles the small center radius is less than one trillionth of a centimeter, is relatively huge "sun" - the nucleus of the atom. Around this atomic "sun" revolve tiny "planets" - electrons. The core consists of two main building blocks of the universe - protons and neutrons (they have a unifying name - nucleons). The electron and the proton - charged particles, and the amount of charge in each of them exactly the same, but the charges differ in sign: the proton is always positively charged, and the electron - negatively. Neutron bears no electrical charge and therefore has very high permeability.

At the atomic scale measurements of the mass of the proton and neutron are taken as unity. The atomic weight of any chemical element therefore depends on the number of protons and neutrons in its nucleus of prisoners. For example, a hydrogen atom, whose nucleus consists of only one proton and has an atomic weight of 1. The helium atom, with a core of two protons and two neutrons, has an atomic weight equal to 4.

The nuclei of atoms of the same element always have the same number of protons, but the number of neutrons can vary. Atoms have a nucleus with the same number of protons, but differing in the number of neutrons and related species of the same element are called isotopes. To distinguish them from each other, attributed to the symbol element number equal to the sum of all the particles in the nucleus of the isotope.

The question may arise: why atomic nucleus does not collapse? After its member protons - electrically charged particles with the same charge, which should repel each other with great force. This is explained by the fact that inside the nucleus there are also so-called intranuclear force attracting core particles to each other. These forces are compensated proton repulsion force and do not give the nucleus fly apart spontaneously.

Intranuclear forces are very high, but there are only a very short distance. Therefore, the core of heavy elements, consisting of hundreds of nucleons are unstable. Core particles are in constant motion here (within the scope of the nucleus), and if they add some additional amount of power, they can overcome the internal forces - the core is divided into parts. The magnitude of this excess energy is called excitation energy. Among the isotopes of heavy elements there are those who would like are at the brink of self-destruction. Suffice it to a small "push", for example, a simple contact with the core of the neutron (and he does not even have to accelerate to a high speed), went to the nuclear fission reaction. Some of these "fissile" isotopes later learned to produce artificially. In nature there is only one isotope such - is uranium-235.

Uranus was discovered in 1783 by Klaproth, who isolated it from pitchblende, and named in honor of the recently discovered planet Uranus. As it turned out later, this was, in fact, not the uranium and an oxide thereof. Pure uranium - metal silver-white color - was obtained only in 1842 Peligot. The new element possessed no remarkable properties and attracted attention until 1896, when Becquerel discovered the phenomenon of radioactivity of uranium salts. After that uranium has become the object of scientific research and experiments, but the practical application still had not.

When in the first third of the XX century physicists became more or less clear structure of the atomic nucleus, they first tried to realize the old dream of the alchemists - tried to convert one chemical element into another. In 1934, French researchers spouse Frederic and Irene Joliot-Curie reported to the French Academy of Sciences on the following experiences: by bombarding plates of aluminum with alpha particles (helium nuclei of the atom) of aluminum atoms are converted into phosphorus atoms, but not ordinary, and radioactive, which in turn moved into the stable isotope of silicon. Thus, the aluminum atom, adjoining one proton and two neutrons, turned into a heavier atom of silicon.

This experience led me to think that if the "shelling" neutrons nucleus of the heaviest naturally occurring element - uranium, it is possible to obtain an element which naturally not. In 1938, German chemists Otto Hahn and Fritz Strassmann repeated the experience in general Joliot-Curie, taking instead of aluminum uranium. The experimental results were not the ones they expected - instead of a new superheavy element with mass number greater than that of uranium, Hahn and Strassmann received minor elements from the middle of the periodic system: barium, krypton, bromine and several others. Experimenters themselves could not explain the observed phenomenon. Only in the following year, the physicist Lise Meitner, Hahn reported that their difficulties, found the correct explanation of the observed phenomenon, assuming that is split (fission) of its nucleus in the shelling of uranium by neutrons. This should have formed the nucleus of the lighter elements (that were taken from barium, krypton and other substances), as well as stand 2-3 free neutron. Further studies will clarify in detail the picture.

Natural uranium consists of a mixture of three isotopes with masses of 238, 234 and 235. The basic amount of uranium accounts for the isotope 238, which includes the nucleus of 92 protons and 146 neutrons. Uranium-235 is only 1/140 of natural uranium (0, 7%) (it has in its nucleus 92 protons and 143 neutrons) and uranium-234 (92 protons, 142 neutrons) only - 1/17500 of the total mass of uranium ( 0, 006%). The least stable of these isotopes is the uranium-235. From time to time it nucleus atoms spontaneously divided into parts, so that the light elements are formed over the periodic system. The process is accompanied by the release of two or three free neutrons, which are racing at high speed -. About 10 thousand km / s (they are called fast neutrons). These neutrons can hit other uranium nuclei, causing nuclear reactions. Each isotope behaves in this case differently. Cores of uranium-238 in most cases simply grasp these neutrons without any further transformations. But about one in five in the collision of a fast neutron with the nucleus of the isotope-238 occurs curious nuclear reaction: one of the neutrons of uranium-238 emits an electron, turning into a proton, ie uranium isotope becomes heavier elements - neptunium-239 (93 protons 146 + neutron). But neptunium unstable - a few minutes later one of his neutron emits an electron, turning into a proton, then the neptunium isotope refers to the next element in a row of the periodic system - plutonium-239 (94 protons + 145 neutrons). If the neutron falls into an unstable nucleus of uranium-235, the division takes place immediately - the atoms decay with the emission of two or three neutrons. It is clear that in natural uranium, most of which atoms are the isotope 238, no visible consequences of this reaction has not - all free neutrons will be eventually absorbed by this isotope.

Well, if you imagine quite a massive piece of uranium, consisting entirely of the isotope-235? Here, the process goes the other way: the neutrons released during the fission of several nuclei, in turn, getting to the neighboring nucleus, causing their division. As a result, it released a new piece of neutrons, which cleaves the following core. Under favorable conditions, this reaction occurs like an avalanche and is called a chain reaction. For its beginning can be quite count the number of the bombarding particles. Indeed, let bombarding uranium-235 only 100 neutrons. They will share the 100 uranium nuclei. This highlighted 250 new second generation of neutrons (an average of 2, 5 per division). Neutrons produce second generation has 250 divisions, in which stand out 625 neutrons. In the next generation it will be equal to 1562, then 3906, then 9670, etc. The number of divisions will increase infinitely, if the process does not stop.

However, in reality, only a small fraction of the neutrons in the nuclei of atoms falls. Others, having flown rapidly between them, carried away into the surrounding space. Self-sustaining chain reaction can occur only in a sufficiently large array of uranium-235, having, as they say, a critical mass. (This mass under normal conditions is 50 kg.) It is important to note that the division of each nucleus is accompanied by the release of huge amounts of energy, which is about 300 million times more energy is expended on splitting! (It is estimated that the complete division 1 kg of uranium-235 is allocated the same amount of heat as the burning of 3 thous. Tons of coal.) This huge splash of energy released in a matter of moments, it reveals itself as an explosion of monstrous force that underlies the action of nuclear weapons . But in order for this weapon has become a reality, it is necessary that the charge was not of natural uranium, and of the rare isotope - 235 (this is called enriched uranium). Later it was found that pure plutonium is also fissile material and can be used in a nuclear charge instead of uranium-235.

All of these important discoveries were made on the eve of the Second World War. Soon in Germany and other countries have begun secret work on atomic bomb. In the US, this issue took up in 1941. The whole complex of works was given the name "Manhattan Project." Administrative management of the project carried out General Groves and scientific - Professor, University of California, Robert Oppenheimer. Both were well aware of the immense complexity of the task before them. Therefore, the first concern was Oppenheimer acquisition highbrow scientific team. In the United States there were many physicists who emigrated from Nazi Germany. It was not easy to bring them to the creation of weapons directed against their former homeland. Oppenheimer personally spoke to each, floating full force of his charm. Soon he was able to gather a small group of theorists, whom he jokingly called the "luminaries". In fact, it included top experts of the time in the field of physics and chemistry. (Among them 13 Nobel Prize winners, including Bohr, Fermi, Frank Chadwick Lawrence.) Apart from these, there were many other professionals of various profiles. The US government did not stint on the costs and the work from the outset took a grand scale. In 1942 a research laboratory in the world's largest has been based in Los Alamos. The population of this scientific city soon reached 9000 people. In composition, scientists scale scientific experiments, the number involved in the work of specialists and workers of Los Alamos had no equal in the history of the world. "Manhattan Project" had its own police, counter-intelligence, communications systems, warehouses, villages, factories, laboratories, its enormous budget.

The main objective of the project was to obtain sufficient quantities of fissile material from which it would be possible to create several atomic bombs. In addition to uranium-235 charge for a bomb, as already mentioned, could serve as an artificial element plutonium-239, that is, the bomb could be both uranium and plutonium. Groves and Oppenheimer agreed that work should be carried out simultaneously in two directions, since it is impossible in advance to decide which of them will be more promising. Both methods are fundamentally different from each other: the accumulation of uranium-235 was carried out by its separation from the main mass of natural uranium and plutonium could be produced only by a controlled nuclear reaction, neutron irradiation of uranium-238. And he and the other path is extremely difficult and not promise easy solutions. In fact, as can be separated from each other by two isotopes, which differ only slightly with their weight and chemically behave in exactly the same way? Neither science nor technique has never faced such a problem. plutonium production also initially seemed very problematic. Prior to that, the whole experience of nuclear transformations was reduced to a few laboratory experiments. Now, however, he had to learn on the industrial scale production of kilograms of plutonium, to develop and create for this special setting - a nuclear reactor, and learn how to manage the course of a nuclear reaction. And here and there it had to solve a whole range of challenges. Therefore, the "Manhattan Project" consisted of several sub-projects, which were headed by prominent scientists. Oppenheimer himself was the head of the Los Alamos Scientific Laboratory. Lawrence headed the Radiation Laboratory, University of California. Fermi led the University of Chicago study for a nuclear reactor.

Initially, the most important problem was to obtain uranium. Before the war, this metal had virtually no use. Now, when he needed at once in large quantities, it appears that there is no industrial process for its production. "Westinghouse" Company undertook its development and quickly achieved success. After purification resin uranium (enriched uranium in a form found in nature) and producing uranium oxide is converted to its tetrafluoride (UF4), from which stand out by electrolysis of metal uranium. If at the end of 1941 in the possession of American scientists were only a few grams of uranium metal, it has its industrial production on the "Westinghouse" company's plants reached 6,000 pounds in November 1942 in a month.

At the same time was working on the creation of a nuclear reactor. Plutonium production process actually reduces exposure to the uranium rods neutrons, causing part of the U-238 was to apply to the plutonium. neutron sources at the same time could be dividing the uranium-235 atoms are dispersed in sufficient quantity among the uranium-238 atoms. But in order to maintain a constant reproduction of neutrons, was supposed to start a chain reaction of fission of uranium-235 atoms. Meanwhile, as already mentioned, each atom of uranium-235, uranium-140 had 238 atoms. It is clear that all the neutrons flying side was much more likely to meet on the way it is them. That is a huge number of neutrons released are proved without any benefit Absorption isotope. It is obvious that the chain reaction can not proceed under these conditions. How to be? At first it seemed that no separation of the two isotopes reactor work at all impossible, but soon one important fact was established: it turned out that uranium-235 and uranium-238 are susceptible to neutrons of different energies. Split core may be relatively small neutron energy of uranium-235 atom, having a speed of about 22 m / s. Such slow neutrons are not captured by the nuclei of uranium-238 - for this they need to have a speed of the order of hundreds of thousands of meters per second. In other words, 238 is powerless to prevent the top and move the chain reaction in uranium-235 induced by neutrons, slowed down to very low speeds - no more than 22 m / s. This phenomenon was discovered by the Italian physicist Fermi, who in 1938 lived in the United States and led here work on the creation of the first reactor. As a moderator of neutrons Fermi decided to use graphite. According to calculations, the fly out of 235 neutrons passing through the graphite layer 40 cm, should reduce its speed to 22 m / s and to start a self-sustaining chain reaction in uranium-235. Another moderator can serve as so-called "hard" water. Because hydrogen atoms being part of it, the size and weight are very close to the neutrons, they can slow down their best. (With fast neutrons occurs about the same as with balls: if a small ball hits the big, it is rolled back, almost without losing speed, while meeting the same with a small ball, he passes a large part of its energy - just a neutron in an elastic collision It bounces off a heavy nucleus is only slightly slowed down, and in a collision with the nuclei of hydrogen atoms very quickly lose all your energy.) However, plain water is not suitable for deceleration, as its hydrogen has a tendency to absorb neutrons. That is why this goal should be to use deuterium, which is part of the "heavy" water.

In early 1942, under the leadership of Fermi indoor tennis court under the West Stand of Chicago stadium began construction of the first nuclear reactor history. All of the researchers themselves conducted. the reaction can be controlled only one way - by adjusting the number of neutrons involved in the chain reaction. Fermi assumed achieve this using rods made from such materials as boron and cadmium that strongly absorb neutrons. Graphite bricks were retarder of which columns erected Physics height of 3 m and a width of 1 to 2 m. Between them were installed rectangular blocks with uranium oxide. On the whole structure went about 46 tonnes of uranium oxide and 385 tons of graphite. To slow down the reaction rods were introduced in the reactor of cadmium and boron. If that was not enough, then the insurance on the platform located above the reactor, there were two scientists with buckets filled with a solution of cadmium salts - they had to pour them into the reactor if the reaction is out of control. Fortunately, this is not required. December 2, 1942 Fermi ordered to push all the control rods and the experiment began. Four minutes later the neutron counters began to click louder and louder. With every minute the intensity of the neutron flux becomes large. This indicated that the reactor is a chain reaction. It lasted for 28 minutes. Fermi then gave the sign, and lowered the rods stop the process. So the first person to release the energy of the atomic nucleus, and proved that he can control it at will. Now there was no doubt that nuclear weapons - a reality.

In 1943, Fermi reactor was dismantled and transported to the Argonne National Laboratory (50 km from Chicago). There was soon built another nuclear reactor, which is used as a moderator heavy water. It consisted of an aluminum cylindrical tank containing 6, 5 tons of heavy water, in which the rods 120 of uranium metal has been vertically loaded enclosed in an aluminum bag. Seven control rods were made of cadmium. Around the tank was placed a graphite reflector, then the screen of lead and cadmium alloys. The whole structure was a concrete shell with a wall thickness of about 2, 5 m. Experiments with these advanced reactors confirmed the possibility of industrial production of plutonium.

The main center of the "Manhattan Project" soon became the town of Oak Ridge in the valley of the Tennessee River, which has a population of a few months has grown to 79 thousand people. Here, in a short time in the history of the first plant for the production of enriched uranium it was built. Immediately in 1943 was put into commercial reactor produces plutonium. In February 1944, out of him every day removed about 300 kg of uranium to the surface of which was obtained by chemical separation of plutonium. (This plutonium is first dissolved and then precipitated.) The purified uranium then again returned to the reactor. In the same year in the barren bleak desert on the southern shore of the Columbia River began construction of a huge Hanford plant. It housed three powerful nuclear reactor, given each day to a few hundred grams of plutonium.

Parallel studies were in full swing for the development of industrial uranium enrichment process. Having considered the various options, Groves and Oppenheimer decided to focus on two methods: gaseous diffusion and electromagnetic. The gas diffusion method was based on a principle known as the law of Graham (he was first formulated in 1829 by the Scottish chemist Thomas Graham and developed in 1896 by the English physicist Reilly). In accordance with this law, if the two gases, one of which is easier to another, to pass through the filter with a negligibly small holes, then some more light gas will pass through it than heavy. In November 1942, Dunning and Urey at Columbia University created by the method of Reilly gaseous diffusion method of uranium isotope separation. Since natural uranium - a solid, it is first converted to uranium fluoride (UF6). Then, the gas is passed through the microscopic - the order of thousandths of a millimeter - the hole in the septum of the filter. Since differences in molar balance gas was very low, the wall of the uranium-235 content was increased only one, 0002-fold. In order to increase the amount of uranium-235 is even more, and the mixture is again passed through the septum, and again increases the amount of uranium in 1, 0002 times. Thus, to increase the uranium-235 content of 99%, it was necessary to pass the gas through the filter 4000. This happened on a huge gaseous diffusion plant at Oak Ridge.

In 1940, under the direction of Ernest Lawrence at the University of California have begun a study on the separation of uranium isotopes by electromagnetic method. It was necessary to find such physical processes that would separate the isotopes by using the difference of their mass. Lawrence attempted to divide isotopes, using the principle of mass spectrograph - instrument by which determine the mass of the atoms. The principle of its operation was as follows: pre-ionized atoms are accelerated by the electric field, and then passed through a magnetic field in which they describe a circle located in a plane perpendicular to the field direction. Since the radii of these trajectories are proportional to weight, light ions have on circles of smaller radius than the heavy. If on the way atoms placed traps, it could thus collect various isotopes separately.

This was the method. Under laboratory conditions, it gave good results. But the construction of the installation, in which the separation of isotopes could be produced on an industrial scale, has proved extremely difficult. However, Lawrence finally managed to overcome all the difficulties. The result of his efforts was the emergence kalutrona, which was set on a giant plant at Oak Ridge.

This electromagnetic plant was built in 1943 and proved to be perhaps the most expensive brainchild "Manhattan Project." Lawrence method required a large number of complex, has not yet developed devices associated with high voltage, high vacuum and high magnetic fields. The scale of the costs were enormous. Kalutron had a giant magnet, whose length reaches 75 meters and weighs about 4000 tons. On this winding electromagnet went several thousand tons of silver wire.

All the works (not counting the value of silver in the amount of $ 300 million that the Treasury Department had provided only for a while) cost $ 400 million. Only electricity expended kalutronom, the Ministry of Defence has paid 10 million. Most of the equipment Oak Ridge plant exceeded in scale and precision manufacturing everything that has ever been developed in the art.

But all these costs were not in vain. Had spent a total of about 2 billion dollars, US scientists in 1944 developed a unique technology of uranium enrichment and plutonium production. Meanwhile, the Los Alamos National Laboratory worked on the project itself bomb. Its principle of operation was broadly clear for a long time: the fissile material (plutonium or uranium-235) followed at the time of the explosion to transfer in critical condition (for a chain reaction to be even much larger critical mass of the charge) and exposed to a beam of neutrons, which entailed the beginning of a chain reaction. According to calculations, the critical mass of the charge exceed 50 kilograms, but it could significantly reduce. In general, the value of a critical mass of highly influenced by several factors. The greater the surface area of ​​the charge - the more useless neutrons emitted into the surrounding space. The smallest surface area has a sphere. Consequently, spherical charges ceteris paribus have the lowest critical mass. In addition, a critical mass value depends on the purity and type of fissile material. It is inversely proportional to the square of the density of the material allowing, for example, twice with increasing density, reduce critical mass quadrupled. Subcriticality desired degree can be obtained, for example, sealing material fissionable by conventional blast charge explosive is constructed as a spherical shell surrounding the core charge. The critical mass, in addition, can be reduced by surrounding the charge-screen TV, well reflecting neutrons. As such a screen may be used lead, beryllium, tungsten, natural uranium, iron and many others.

One possible design of the atomic bomb uranium consists of two pieces which, when combined, form a critical mass greater. In order to trigger a bomb blast, it is necessary as soon as possible to bring them closer together. The second method uses a convergent implosion. In this case, the gas flow from conventional explosive was directed to fissile material located inside and squeezed it until then, until it reached a critical mass. The connection charge and intensive irradiation by neutrons, as already mentioned, causes a chain reaction, which resulted in the first second temperature increases of up to 1 million degrees. During this time, it kept pace divide only about 5% of the critical mass. The rest of the charge in the early design bombs evaporates uselessly.

The first in the history of the atomic bomb (she was given the name "Trinity") was assembled in the summer of 1945. And on 16 June 1945 at the nuclear test site in the desert of Alamogordo (New Mexico) on the first atomic explosion the world has been made. The bomb was placed in the center of the polygon at the top of a steel 30-meter tower. Around her was placed at a distance recording equipment. At 9 km there is an observation post, and in the 16 km - command. All the witnesses of this event a nuclear explosion made a tremendous impression. According to the description of eyewitnesses, it was a feeling that a lot of suns united into one, and once lit up the landfill. Then, over the plain there was a huge ball of fire, and him and slowly began to rise ominously round cloud of dust and light. Looking up from the ground, the ball of fire for a few seconds, soared to a height of more than three kilometers. With every moment he grew in size, soon its diameter reached 1, 5 km away, and it slowly rose into the stratosphere. Then the fireball gave way to swirling pillar of smoke that stretched to a height of 12 km, taking the form of a giant mushroom. All this was accompanied by a terrible crash, which shook the earth. Power bomb exploded surpassed all expectations.

Once enabled the radiation situation, several tanks "Sherman", lined with lead plates inside, rushed to the explosion area. One of them is the farm, which was eager to see the results of their labor. His eyes appeared dead scorched earth, which within a radius of 1, 5 km have been destroyed every living thing. Sand has had it in the vitreous greenish crust that covered the ground. The huge crater lay mangled remains of the steel support towers. The power of the explosion was estimated at 20,000 tons of TNT.

The next step was to combat use the bomb against Japan, which after the capitulation of Nazi Germany, one continued to war with the US and its allies. Boosters did not yet exist, so the bombardment had done with the aircraft. The components of the two bombs were delivered with great care cruiser "Indianapolis" on the island of Tinian, where I was based 509-consolidated group of US Air Force. According to the type of charge and designs the bombs were somewhat different from each other. The first bomb - "Little Boy" - was a large-sized aircraft bomb with an atomic charge of highly enriched uranium-235. Its length was about 3 m, diameter - 62 cm, weight - 4, 1 ton of the second bomb -. "Fat Man" - with a charge of plutonium-239 was egg-shaped with a large-sized stabilizer. Its length was 3, 2 m, a diameter of 1 5 m, weight - 4, t 5.

August 6 bomber B-29 "Enola Gay" Colonel Tibbets dropped the "Little Boy" on the Japanese city of Hiroshima large. A bomb dropped by parachute and exploded as it was envisaged, at an altitude of 600 m above the ground. The consequences of the explosion were terrible. Even in view of the pilots themselves destroyed them in an instant, a peaceful town made a dismal impression. Later, one of them admitted that they had seen in the second worst thing that can only see the people. For those who were on the ground, an event reminiscent of an authentic hell. First of all, the heat wave has passed over Hiroshima. Its effect lasted only a few moments, but it was so powerful that it melted even tile and quartz crystals in granite slabs, turned into coal telephone poles at a distance of 4 km and finally, so incinerated human bodies, that from them there were only shadows on the asphalt pavements or on the walls of houses. Then, out of the fireball burst and a monstrous gust of wind rushed over the city at a speed of 800 km / h, sweeping away everything in its path. Unable to withstand the onslaught of his violent home collapsed as knocked down. The giant circle diameter of 4 km there is not a single building. A few minutes after the explosion, the city was black radioactive rain - it is converted into steam condenses moisture in the upper layers of the atmosphere and fell to the ground in the form of large drops, mixed with radioactive dust. After the rain the city hit a new gust of wind blowing, this time in the direction of the epicenter. He was weaker than the first, but still strong enough to pull a tree root. The wind blew a gigantic fire that burned everything that could burn. Of the 76 000 buildings completely destroyed and burned 55 thousand. The witnesses of this terrible disaster remembered Torch people, from which burned to the ground subsided clothes with skin rags, and crowds of frantic people, covered with terrible burns who were running screaming through the streets. The air was suffocating stench of burning human flesh. Everywhere lay people, dead and dying. There were many who became blind and deaf and tychas on all sides, could not make out anything in tsarivshem around chaos. Accidents that were from the epicenter at a distance of up to 800 m, for a split second burn literally - their insides evaporated, and the body turned into lumps of smoldering coals. Now when from the epicenter at a distance of 1 km, were struck with radiation sickness in a very severe form. Within hours, they began vomiting, the temperature soared up to 39-40 degrees, appeared shortness of breath and bleeding. Then poured on the skin non-healing ulcers, blood composition has changed dramatically, her hair fell out. After the terrible suffering, usually in the second or third day, there came death. Total from the blast and radiation sickness killed about 240 thousand people. Around 160 thousand received radiation sickness in a lighter form - their painful death was delayed for several months or years. When the news of the accident spread throughout the country, all of Japan was paralyzed with fear. He even grew after August 9 aircraft "Box Car" Major Sweeney dropped a second bomb on Nagasaki. It also killed and injured several hundred thousand inhabitants. Unable to resist the new weapons, the Japanese government capitulated - the atomic bomb put an end to the Second World War.

War is over. It lasted only six years, but managed to change the world and people almost beyond recognition. Human civilization until 1939, and human civilization after 1945 is not strikingly similar to each other. There are many reasons, but one of the most important - the emergence of nuclear weapons. It is no exaggeration to say that the shadow of Hiroshima is on the entire second half of XX century. It has become a profound moral burn for many millions of people like former contemporaries of the disaster, and were born decades after her. Modern man can not think of the world as thought about it before August 6, 1945 - he understands all too clearly that the world can a few moments turn into nothing. Modern man can not look at war since watched his ancestors - he reliably knows that this war will last and will not appear there are no winners or losers. Nuclear weapons has left its imprint on all spheres of public life, and modern civilization can not live under the same laws, that the sixty or eighty years ago. No one understood this better than the creators of the atomic bomb. "People of the world - wrote Robert Oppenheimer - must unite. The horror and destruction sown by the last war, dictate to us the idea. The atomic bomb have shown her with all the brutality. Other people in other times already said these words - only the other weapons and other wars. They did not succeed. But those who today say that these words are useless, deluded by the vagaries of history. We can not convince. The results of our work do not leave humanity other choice but to create a unified world. A world based on the rule of law and humanism. "

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