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Atomic Bomb: Inventors, WWII and Facts

Atomic Bomb: Inventors, WWII and Facts

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The atomic bomb, and nuclear bombs, are powerful weapons that use nuclear reactions as their source of explosive energy. Scientists first developed nuclear weapons technology during World War II. Atomic bombs have been used only twice in war—both times by the United States against Japan at the end of World War II, in Hiroshima and Nagasaki. A period of nuclear proliferation followed that war, and during the Cold War, the United States and the Soviet Union vied for supremacy in a global nuclear arms race.

Nuclear Bombs and Hydrogen Bombs

A discovery by nuclear physicists in a laboratory in Berlin, Germany, in 1938 made the first atomic bomb possible, after Otto Hahn, Lise Meitner and Fritz Strassman discovered nuclear fission.

When an atom of radioactive material splits into lighter atoms, there’s a sudden, powerful release of energy. The discovery of nuclear fission opened up the possibility of nuclear technologies, including weapons.

Atomic bombs are weapons that get their energy from fission reactions. Thermonuclear weapons, or hydrogen bombs, rely on a combination of nuclear fission and nuclear fusion. Nuclear fusion is another type of reaction in which two lighter atoms combine to release energy.

The Manhattan Project

The Manhattan Project was the code name for the American-led effort to develop a functional atomic bomb during World War II. The Manhattan Project was started in response to fears that German scientists had been working on a weapon using nuclear technology since the 1930s.

On December 28, 1942, President Franklin D. Roosevelt authorized the formation of the Manhattan Project to bring together various scientists and military officials working on nuclear research.

Who Invented The Atomic Bomb?

Much of the work in the Manhattan Project was performed in Los Alamos, New Mexico, under the direction of theoretical physicist J. Robert Oppenheimer, “father of the atomic bomb.” On July 16, 1945, in a remote desert location near Alamogordo, New Mexico, the first atomic bomb was successfully detonated—the Trinity Test. It created an enormous mushroom cloud some 40,000 feet high and ushered in the Atomic Age.

Hiroshima And Nagasaki Bombings

Scientists at Los Alamos had developed two distinct types of atomic bombs by 1945—a uranium-based design called “the Little Boy” and a plutonium-based weapon called “the Fat Man.”

While the war in Europe had ended in April, fighting in the Pacific continued between Japanese forces and U.S. troops. In late July, President Harry Truman called for Japan’s surrender with the Potsdam Declaration. The declaration promised “prompt and utter destruction” if Japan did not surrender.

On August 6, 1945, the United States dropped its first atomic bomb from a B-29 bomber plane called the Enola Gay over the city of Hiroshima, Japan. The “Little Boy” exploded with about 13 kilotons of force, leveling five square miles of the city and killing 80,000 people instantly. Tens of thousands more would later die from radiation exposure.

When the Japanese did not immediately surrender, the United States dropped a second atomic bomb three days later on the city of Nagasaki. The “Fat Man” killed an estimated 40,000 people on impact.

Nagasaki had not been the primary target for the second bomb. American bombers initially had targeted the city of Kokura, where Japan had one of its largest munitions plants, but smoke from firebombing raids obscured the sky over Kokura. American planes then turned toward their secondary target, Nagasaki.

Citing the devastating power of “a new and most cruel bomb,” Japanese Emperor Hirohito announced his country’s surrender on August 15—a day that became known as ‘V-J Day’—ending World War II.

The Cold War

The United States was the only country with nuclear weaponry in the years immediately following World War II. The Soviets initially lacked the knowledge and raw materials to build nuclear warheads.

Within just a few years, however, the U.S.S.R. had obtained—through a network of spies engaging in international espionage—blueprints of a fission-style bomb and discovered regional sources of uranium in Eastern Europe. On August 29, 1949, the Soviets tested their first nuclear bomb.

The United States responded by launching a program in 1950 to develop more advanced thermonuclear weapons. The Cold War arms race had begun, and nuclear testing and research became high-profile goals for several countries, especially the United States and the Soviet Union.

Read More: How The Hiroshima Bombing Kick-Started The Cold War

Cuban Missile Crisis

Over the next few decades, each world superpower would stockpile tens of thousands of nuclear warheads. Other countries, including Great Britain, France, and China developed nuclear weapons during this time, too.

To many observers, the world appeared on the brink of nuclear war in October of 1962. The Soviet Union had installed nuclear-armed missiles on Cuba, just 90 miles from U.S. shores. This resulted in a 13-day military and political standoff known as the Cuban Missile Crisis.

President John F. Kennedy enacted a naval blockade around Cuba and made it clear the United States was prepared to use military force if necessary to neutralize the perceived threat.

Disaster was avoided when the United States agreed to an offer made by Soviet leader Nikita Khrushchev to remove the Cuban missiles in exchange for the United States promising not to invade Cuba.

Three Mile Island

Many Americans became concerned about the health and environmental effects of nuclear fallout—the radiation left in the environment after a nuclear blast—in the wake of World War II and after extensive nuclear weapons testing in the Pacific during the 1940s and 1950s.

The antinuclear movement emerged as a social movement in 1961 at the height of the Cold War. During Women Strike for Peace demonstrations on November 1, 1961 co-organized by activist Bella Abzug, roughly 50,000 women marched in 60 cities in the United States to demonstrate against nuclear weapons.

The antinuclear movement captured national attention again in the 1970s and 1980s with high profile protests against nuclear reactors after the Three Mile Island accident—a nuclear meltdown at a Pennsylvania power plant in 1979.

In 1982, a million people marched in New York City protesting nuclear weapons and urging an end to the Cold War nuclear arms race. It was one of the largest political protests in United States history.

Nuclear Non-Proliferation Treaty (NPT)

The United States and Soviet Union took the lead in negotiating an international agreement to halt the further spread of nuclear weapons in 1968.

The Treaty on the Non-Proliferation of Nuclear Weapons (also called the Non-Proliferation Treaty or NPT) went into effect in 1970. It separated the world’s countries into two groups—nuclear weapons states and non-nuclear weapons states.

Nuclear weapons states included the five countries that were known to possess nuclear weapons at the time—the United States, the U.S.S.R., Great Britain, France and China.

According to the treaty, nuclear weapons states agreed not to use nuclear weapons or help non-nuclear states acquire nuclear weapons. They also agreed to gradually reduce their stockpiles of nuclear weapons with the eventual goal of total disarmament. Non-nuclear weapons states agreed not to acquire or develop nuclear weapons.

When the Soviet Union collapsed in the early 1990s, there were still thousands of nuclear weapons scattered across Eastern Europe and Central Asia. Many of the weapons were located in Belarus, Kazakhstan and Ukraine. These weapons were deactivated and returned to Russia.

Illegal Nuclear Weapon States

Some countries wanted the option of developing their own nuclear weapons arsenal and never signed the NPT. India was the first country outside of the NPT to test a nuclear weapon in 1974.

Other non-signatories to the NTP include: Pakistan, Israel and South Sudan. Pakistan has a known nuclear weapons program. Israel is widely believed to possess nuclear weapons, though has never officially confirmed or denied the existence of a nuclear weapons program. South Sudan is not known or believed to possess nuclear weapons.

North Korea

North Korea initially signed the NPT treaty, but announced its withdrawal from the agreement in 2003. Since 2006, North Korea has openly tested nuclear weapons, drawing sanctions from various nations and international bodies.

North Korea tested two long-range intercontinental ballistic missiles in 2017—one reportedly capable of reaching the United States mainland. In September 2017, North Korea claimed it had tested a hydrogen bomb that could fit on top an intercontinental ballistic missile.

Iran, while a signatory of the NPT, has said it has the capability to initiate production of nuclear weapons at short notice.


Pioneering Nuclear Science: The Discovery of Nuclear Fission. International Atomic Energy Agency.
The Development and Proliferation of Nuclear Weapons. nobelprize.org.
Here are the facts about North Korea’s nuclear test. NPR.

Who Built the Atomic Bomb?

In just 27 months, America accomplished what other nations thought impossible. How did the United States achieve the remarkable feat of building an atomic bomb when Germany, Italy and Japan failed? Hundreds of physicists, mathematicians, and engineers were needed to design, build, and test the world's first atomic weapon and the Unites States government did everything in its power to lure these individuals to the Manhattan Project. To Bulgarian-born journalist Stephane Groueff, the Manhattan Project was an outstanding example of the "American way": a combination of creativity, courage to try unorthodox approaches, and a relentless determination to succeed.

A “Race” for the Bomb

The United States government became aware of the German nuclear program in August 1939, when Albert Einstein wrote to President Roosevelt, warning "that it may become possible to set up a nuclear chain reaction in a large mass of uranium by which vast amounts of power and large quantities of new radium-like elements would be generated." The United States was in a race to develop an atomic bomb believing whoever had the bomb first would win the war.

Robert Furman, assistant to General Leslie Groves and the Chief of Foreign Intelligence for the Manhattan Project, described how “the Manhattan Project was built on fear: fear that the enemy had the bomb, or would have it before we could develop it. The scientists knew this to be the case because they were refugees from Germany, a large number of them, and they had studied under the Germans before the war broke out.” Manhattan Project physicist Leona Marshall Libby also recalled, “I think everyone was terrified that we were wrong, and the Germans were ahead of us.… Germany led the civilized world of physics in every aspect, at the time war set in, when Hitler lowered the boom. It was a very frightening time.”

The United States government remained equally afraid. General Groves remembered, “Unless and until we had positive knowledge to the contrary, we had to assume that the most competent German scientists and engineers were working on an atomic program with the full support of their government and with the full capacity of German industry at their disposal. Any other assumption would have been unsound and dangerous” (Norris 295). There was even consideration of kidnapping Werner Heisenberg in Switzerland in 1942, although this plan never came to fruition. In 1943, the United States launched the Alsos Mission, a foreign intelligence project focused on learning the extent of Germany’s nuclear program.

By 1944, however, the evidence was clear: the Germans had not come close to developing a bomb and had only advanced to preliminary research. Following the German defeat, the Allies detained ten German scientists, at Farm Hall, a bugged house in Godmanchester, England, from July 3, 1945 to January 3, 1946. Some of them, such as Heisenberg, Kurt Diebner, and Carl von Weiszacker were directly involved in the project, while others, such as Otto Hahn and Max von Laue, were only suspected and later proven to have not been involved. Heisenberg's disbelief after hearing that the United States had dropped an atomic bomb on Hiroshima confirmed in the minds of the Allies that the German effort was never close. As one German scientist exclaimed, it must have taken "factories large as the United States to make that much uranium-235!"

Atomic Bomb: Inventors, WWII and Facts - HISTORY

On August 2, 1939, just before the beginning of World War II, Albert Einstein wrote to then President Franklin D. Roosevelt. Einstein and several other scientists told Roosevelt of efforts in Nazi Germany to purify uranium-235, which could be used to build an atomic bomb. It was shortly thereafter that the United States Government began the serious undertaking known then only as "The Manhattan Project." Simply put, the Manhattan Project was committed to expediting research that would produce a viable atomic bomb.

The most complicated issue to be addressed in making of an atomic bomb was the production of ample amounts of "enriched" uranium to sustain a chain reaction. At the time, uranium-235 was very hard to extract. In fact, the ratio of conversion from uranium ore to uranium metal is 500:1. Compounding this, the one part of uranium that is finally refined from the ore is over 99% uranium-238, which is practically useless for an atomic bomb. To make the task even more difficult, the useful U-235 and nearly useless U-238 are isotopes, nearly identical in their chemical makeup. No ordinary chemical extraction method could separate them only mechanical methods could work.

A massive enrichment laboratory/plant was constructed at Oak Ridge, Tennessee. Harold C. Urey and his colleagues at Columbia University devised an extraction system that worked on the principle of gaseous diffusion, and Ernest O. Lawrence (inventor of the Cyclotron) at the University of California in Berkeley implemented a process involving magnetic separation of the two isotopes.

Next, a gas centrifuge was used to further separate the lighter U-235 from the heavier, non-fissionable U-238. Once all of these procedures had been completed, all that needed to be done was to put to the test the entire concept behind atomic fission ("splitting the atom," in layman's terms).

Over the course of six years, from 1939 to 1945, more than $2 billion was spent during the history of the Manhattan Project. The formulas for refining uranium and putting together a working atomic bomb were created and seen to their logical ends by some of the greatest minds of our time. Chief among the people who unleashed the power of the atom was J. Robert Oppenheimer, who oversaw the project from conception to completion.

Finally, the day came when all at Los Alamos would find out if "The Gadget" (code-named as such during its development) was going to be the colossal dud of the century or perhaps an end to the war. It all came down to a fateful morning in midsummer, 1945.

At 5:29:45 (Mountain War Time) on July 16, 1945, in a white blaze that stretched from the basin of the Jemez Mountains in northern New Mexico to the still-dark skies, "The Gadget" ushered in the Atomic Age. The light of the explosion then turned orange as the atomic fireball began shooting upwards at 360 feet per second, reddening and pulsing as it cooled. The characteristic mushroom cloud of radioactive vapor materialized at 30,000 feet. Beneath the cloud, all that remained of the soil at the blast site were fragments of jade green radioactive glass created by the heat of the reaction.

The brilliant light from the detonation pierced the early morning skies with such intensity that residents from a faraway neighboring community would swear that the sun came up twice that day. Even more astonishing is that a blind girl saw the flash 120 miles away.

Upon witnessing the explosion, its creators had mixed reactions. Isidor Rabi felt that the equilibrium in nature had been upset -- as if humankind had become a threat to the world it inhabited. J. Robert Oppenheimer, though ecstatic about the success of the project, quoted a remembered fragment from the Bhagavad Gita. "I am become Death," he said, "the destroyer of worlds." Ken Bainbridge, the test director, told Oppenheimer, "Now we're all sons of bitches."

After viewing the results several participants signed petitions against loosing the monster they had created, but their protests fell on deaf ears. The Jornada del Muerto of New Mexico would not be the last site on planet Earth to experience an atomic explosion.

Scientists Who Invented the Atomic Bomb under the Manhattan Project: Robert Oppenheimer, David Bohm, Leo Szilard, Eugene Wigner, Otto Frisch, Rudolf Peierls, Felix Bloch, Niels Bohr, Emilio Segre, James Franck, Enrico Fermi, Klaus Fuchs and Edward Teller. View a copy of the letter Einstein wrote Roosevelt that prompted the Manhattan Project.

Atomic Bomb Detonation at Hiroshima

As many know, the atomic bomb has been used only twice in warfare. The first was at Hiroshima. A uranium bomb nicknamed "Little Boy" (despite weighing in at over four and a half tons) was dropped on Hiroshima August 6, 1945. The Aioi Bridge, one of 81 bridges connecting the seven-branched delta of the Ota River, was the target ground zero was set at 1,980 feet. At 0815 hours, the bomb was dropped from the Enola Gay. It missed by only 800 feet. At 0816 hours, in an instant, 66,000 people were killed and 69,000 injured by a 10-kiloton atomic explosion.

The area of total vaporization from the atomic bomb blast measured one half mile in diameter total destruction one mile in diameter severe blast damage as much as two miles in diameter. Within a diameter of two and a half miles, everything flammable burned. The remaining area of the blast zone was riddled with serious blazes that stretched out to the final edge at a little over three miles in diameter.

On August 9, 1945, Nagasaki fell to the same treatment. This time a Plutonium bomb nicknamed "Fat Man" was dropped on the city. Though "Fat Man" missed its target by over a mile and a half, it still leveled nearly half the city. In a split second, Nagasaki's population dropped from 422,000 to 383,000. Over 25,000 people were injured.

Japan offered to surrender on August 10, 1945.

NOTE: Physicists who have studied these two atomic explosions estimate that the bombs utilized only 1/10th of 1 percent of their respective explosive capabilities.

Byproducts of Atomic Bomb Detonations

While the explosion from an atomic bomb is deadly enough, its destructive ability doesn't stop there. Atomic bomb fallout creates another hazard as well. The rain that follows any atomic detonation is laden with radioactive particles, and many survivors of the Hiroshima and Nagasaki blasts succumbed to radiation poisoning.

The atomic bomb detonation also has the hidden lethal surprise of affecting the future generations of those who live through it. Leukemia is among the greatest of afflictions that are passed on to the offspring of survivors.

While the main purpose behind the atomic bomb is obvious, there are other by-products of the use of atomic weapons. While high-altitude atomic detonations are hardly lethal, one small, high-altitude detonation can deliver a serious enough EMP (Electro-Magnetic Pulse) to scramble all things electronic, from copper wires to a computer's CPU, within a 50-mile radius.

During the early history of The Atomic Age, it was a popular notion that one day atomic bombs would be used in mining operations and perhaps aid in the construction of another Panama Canal. Needless to say, it never came about. Instead, the military applications of atomic destruction increased. Atomic bomb tests off of the Bikini Atoll and several other sites were common until the Nuclear Test Ban Treaty was introduced.

The Story of the Atomic Bomb

The story of the atomic bomb started around the turn of the century when a small number of physicists began to think about, discuss, and publish papers about the phenomenon of radioactivity, the behavior of alpha particles, and the properties of various materials when irradiated. Initially, these persons included well-known scientists such as Ernest Rutherford of New Zealand and Great Britain, Neils Bohr of Denmark, Pierre and Marie Curie of France, and Albert Einstein of Germany. Later, the "nuclear group" was joined by Leo Szilard of Hungary, Otto Hahn of Germany, Michael Polenyi of Hungary, Walter Bothe of Germany, Lise Meitner of Austria, Hantaro Nagaoka of Japan, and others of similarly diverse backgrounds.

By the early 1900s these scientists were studying the structure of the atom and the deflection and scattering of alpha particles. In 1908 Rutherford showed that the alpha particle was in fact an atom of helium in 1911 he announced that he had found the nucleus of an atom to be a minute but concentrated mass surrounded by electrons in orbits. By the 1930s the nuclear scientists were exploring the revolutionary concept of splitting an atom of uranium with a neutron.

The early 1930s saw the rise of anti-Semitism in Germany and Russia. Hitler became Chancellor of Germany in 1933, and the Nazis began to abolish the civil rights of German Jews and to start their campaign of persecution. German scientists who were Jews realized that the Nazis posed a deadly threat, and they began to emigrate, mostly to the United States. The emigres over the 1930s included Einstein, Theodore von Karman, John von Neumann, Eugene Wigner, Leo Szilard, Hans Bethe, Edward Teller, Lise Meitner, Enrico Fermi, and many others. Although not Jewish, Enrico Fermi had married a Jewish woman, and he feared and despised Mussolini's anti-Semitism. These emigres continued their research and discussions in the United States and in Britain.

By 1939 the thinking of nuclear scientists had progressed to such subjects as fission of uranium atoms and causing a chain reaction, particularly in the U235 isotope, when the material is bombarded by neutrons the comparative effectiveness of slow neutrons versus fast neutrons in achieving a chain reaction and the possible methods of separating U235 from U238 in natural uranium. The possibility of producing a massive atomic explosion was generally known and discussed, and calculations of a "critical mass" were being made.

German intelligence had discovered the direction of nuclear research in the United States and Great Britain. The German War Office consolidated research under their leading physicists Erich Bagge, Werner Heisenberg, and Paul Harteck. One of the issues being studied was the use of heavy-water as a moderator, used to slow the travel of secondary neutrons.

In the United States, in the summer of 1939, a small number of physicists, alarmed over the possibility of Germany successfully developing an atomic bomb, decided to warn President Roosevelt. A letter was written by Einstein and Szilard, and was delivered to the President's aide, General Edwin Watson, by Alexander Sachs, an economist and writer who had a friendly relationship with Roosevelt. Sachs was given an appointment with the President to whom he read Einstein's letter. The letter described the new powerful bombs that could be produced and recommended that the U.S. Government speed up experimental work currently taking place. Einstein closed his letter by stating his understanding that Germany had stopped the sale of uranium from Czechoslovakian mines and that Carl von Weizacker, a highly respected German scientist, was attached to the Kaiser Wilhelm Institute in Berlin where American work on uranium was being repeated. These last remarks reflected the concern of U.S. nuclear scientists over German capabilities.

The meeting with Roosevelt took place on October 11, 1939. The ensuing months saw the establishment of nuclear-devoted committees in the various departments of the U. S. Government and the continued research and inter-agency coordination of results. In 1941 James Bryant Conant opened a liaison office between the British government and the National Defense Research Council of the United States. The Japanese bombing of Pearl Harbor on December 7, 1941, accelerated the development of an atomic bomb in the United States.

In the spring of 1942 the decision was made to consolidate development activities in Chicago. The objective was to produce a nuclear chain reaction by the end of the year. Fermi and colleagues moved from New York, where they had been using the resources of Columbia University, and commenced operation on the premises of the University of Chicago. To build an experimental "pile" to demonstrate the feasibility of a controllable chain reaction, Fermi assembled the components (6 tons of uranium and 250 tons of graphite for use as a moderator) in a squash court in the abandoned University of Chicago stadium. Manually-operated cadmium rods were used as a control method. On the afternoon of December 2, 1942, with 42 observers watching the instruments and listening to the clicking of the neutron counters, the pile achieved criticality, i.e., a self-sustaining nuclear reaction, operating 4 1/2 minutes until the rods were reinserted.

Earlier, in the spring and summer of 1942, nuclear scientists and their leaders in the United States became aware of a new material created by neutron bombardment of U238. This material was named plutonium by its discoverer, Glenn Seaborg. The use of plutonium for bombs would have several advantages over U235: greater explosive power, smaller size and weight, and easier manufacturing. Its atomic designation became Pu239.

In Germany, theoretical knowledge of atomic physics and the potential application of that science to weapons was abreast of that in Britain and the United States. German scientists, however, were handicapped by shortages in materials and funds. Developments with long range application inevitably received priority behind those of immediate benefit to the war effort. Albert Speer in June 1942 discussed with Hitler the possibility of developing an atomic bomb but with no clear conclusions. German research would continue but without focus on weaponry. Allies' intelligence was not aware of this situation.

The British were concerned about German acquisition of heavy- water produced at Vemork in southern Norway. A glider-borne British attempt to sabotage the installation in November 1942 was a failure, due to a combination of poor planning and bad weather. In February 1943 a Norwegian commando team made another attempt and succeeded in demolishing most of the plant, interrupting production for many months. In the autumn of 1943, the British received news that the plant had resumed production of heavy-water. Increased security there by the Nazis ruled out another sabotage effort, and a precision bombing attack was approved by British-American representatives in Washington. On November 16, 1943 the attack was made by 140 B-17s from the Eighth Air Force. The power plant was destroyed and the electrolysis unit damaged, effectively shutting the plant down. The Nazis elected to rebuild in Germany and planned to transport by rail and ferry the equipment and existing heavy-water that remained. The British decided to sabotage the ferry that would be involved. The sabotage attempt was successfully made by a three-man Norwegian team on February 20, 1944, sending the ferry and its cargo to the bottom of a Norwegian lake. After the war a member of German Army Ordnance claimed that the loss of heavy-water production in Norway was the main factor in German failure to achieve a self-sustaining atomic reactor.

In Japan, studies toward an atomic bomb began within the military. General Takeo Yasuda, director of the Aviation Technology Research Institute of the Imperial Japanese Army, followed the international scientific literature and in 1938 and 1939 noticed the discovery of nuclear fission. He directed his aide, Lt. Col. Tatsusaburo Suzuki, to prepare a report. Suzuki reported back in October 1940 and concluded that Japan had access to sufficient uranium in Korea and Burma to make an atomic bomb.

Yasudo turned to Japanese physicists, who had worked with Neils Bohr and Ernest Lawrence, and who had built a cyclotron at a laboratory in Tokyo. In April 1941 the Imperial Army Air Force authorized research toward the development of an atomic bomb.

During the war, Japanese nuclear efforts were severely handicapped by the effects of the war on their industrial economy. By late 1944, many Japanese scientists, probably including their leading physicist, Yoshio Nishina, realized that they would not be able to build a bomb in time to effect the outcome of the war.

In the Soviet Union work toward an atomic bomb had begun by 1939. A leading Soviet physicist, Igor Kurchatov, had alerted his government to the military significance of nuclear fission. The German invasion in June 1941 temporarily halted the nuclear program and caused the rearrangement of research priorities to the disadvantage of atomic bombs, at least for the time being. After reassessment by the Soviet atomic community, work on a weapon program resumed by early 1943.

In the United States, the Manhattan Project (a name adopted for security reasons and derived from its birthplace) moved into high gear, even before Fermi had completed his demonstration of the feasibility of a controlled chain reaction. In September 1942 responsibility for managing the Manhattan Project was given to Leslie R. Groves, a colonel (soon to be promoted) in the Corps of Engineers. One of Groves' first major decisions was to select Oak Ridge, Tennessee, to be the site for plants for isotope separation, to produce U235 from U238 in quantities sufficient for atomic bombs.

Groves planned to use two competing technologies for the separation process: electromagnetic and gaseous-diffusion. The electromagnetic process required the use of massive magnets to separate the lighter U235 from the heavier U238. The gaseous diffusion process employed a porous barrier through which uranium hexaflouride gas would be pumped the lighter molecules of U235 would pass through more readily than the heavier ones of U238 and could be collected via a chemical process.

Construction by the contractor experienced no unusual difficulties, but a nationwide shortage of copper for the massive magnets for the electromagnetic system had to be solved by using silver, which came from the U.S. Treasury Depository in huge quantities. By October 1943 the system was ready for testing. However, it soon became apparent that the magnets were plagued by numerous electrical shorts, caused by faulty design and manufacture. All of the 48 magnets had to be rebuilt. Finally the system was ready for operation in January 1944.

Thousands of diffusion tanks for the gaseous-diffusion process would be required. Selection of a suitable barrier material was a difficult problem, causing a dispute among adherents of competing approaches. Groves finally decided to submit the matter to a British-American committee, who ratified a decision that he had already made to use a new but superior design that would further delay production. The date of Groves' decision was in early January 1944. In early 1945 Oak Ridge began shipping weapon-grade U235 to Los Alamos, where weapon development was taking place.

In early 1943 Groves had selected Hanford, Washington, as the site for plutonium production. The selection of Hanford over Oak Ridge was based on the former's remote location, which militated against disastrous results if a nuclear accident occurred. Major design, recruiting, and construction problems existed, but the principal buildings were ready for installation of the first nuclear pile by February 1944. Plutonium production in quantity began in December 1944.

The next major problem, which surfaced in late 1942, was the establishment of a laboratory for work on bomb design. General Groves favored Robert Oppenheimer as the director, although Army counterintelligence objected because of Oppenheimer's former friends who had been Communist Party members. Groves was able to convince Vannevar Bush, the head of the Office of Scientific Research and Development, that no one else could be a better choice. Both Groves and Oppenheimer agreed on Los Alamos, New Mexico, to be the site. The site was on the grounds of a boys' school located on a rugged mesa thirty-five miles northwest of Santa Fe. Manning and construction started in early 1943. The remoteness of the site made recruiting of qualified personnel difficult, but Oppenheimer was able to appeal to most candidates' patriotism.

There were two possible approaches to bomb design. The first was to achieve a critical mass and the resulting nuclear explosion by very rapidly joining two sub-critical halves and initiating a neutron source. This approach was called the "gun type" since the system used a tube in which the two halves were fired toward each other. The other, newer approach used a ball (called core) of fissionable material surrounded by a number of lenses of explosive which when detonated squeezed the ball into a critical mass. The neutron initiator was located in the center of the core. This approach was called the implosion method. The gun-type was considered the more reliable the implosion method required simultaneous detonation of the lenses and was relatively risky.

In early 1944 the Army Air Forces started its program to develop a delivery capability using the B-29 aircraft. The B-29 was the logical choice in view of its long range, superior high-altitude performance, and ability to carry an atomic bomb that was expected to weigh 9000 to 10,000 pounds. In March and again in June dummy atomic bombs were dropped by B-29s at Muroc Army Air Force Base in California to test the release mechanism. In August seventeen B-29s entered a modification program at the Glenn L. Martin plant in Omaha, Nebraska, to apply the lessons learned at Muroc. That month the decision was made to train a special group to deliver the first atomic bombs and a squadron then based at Fairmont, Nebraska, in training for assignment to Europe, was selected to form the nucleus of the new organization, which was designated the 509th Composite Group. In late August General "Hap"Arnold, the commanding general of the Army Air Forces, approved the assignment of Lieutenant Colonel (later Colonel) Paul W. Tibbetts to command the 509th. Tibbets was highly qualified for the position. He was a veteran of B-17 missions over Europe and B-29 testing in the United States. In September the 509th moved to Wendover Field, Utah, and began receiving its new B-29s in October. An intensive training program for the 509th took place, designed specifically to prepare the crews for a high altitude release of the bomb, including an escape maneuver that would avoid the shock wave that could damage or destroy the aircraft. In May 1945 the 509th deployed to its intended operational base, Tinian.

President Roosevelt died on April 12, 1945 and Harry Truman assumed the Presidency and inherited the responsibility for final nuclear weapon decisions. The first was regarding plans to drop an atomic bomb on Japan. The Target Committee, composed of Groves' deputy, two Army Air Forces officers, and five scientists including one from Great Britain, met in Washington in mid-April 1945. Their initial intention was to select cities that had not previously been heavily damaged by the Twentieth Air Force's conventional-weapon bombing campaign, but such pristine targets had become scarce. Finally they tentatively chose 17 cities, in a list that included Hiroshima and Nagasaki.

For several years there had been dissent among scientists and political leaders over the morality and necessity of using atomic bombs against Japan. There was no ignoring, however, the fanaticism of Japanese soldiers, demonstrated at Tinian, Iwo Jima, Okinawa, and other Pacific islands. An invasion of Japan would be extremely difficult and would inevitably result in the loss of thousands of lives, Americans as well as Japanese, civilian and military.

The next step in development of a weapon was to conduct a live test of a nuclear detonation. The site was to be on a scrub-growth area on the Alamogordo Bombing Range two hundred miles south of Los Alamos. The test was named "Trinity". After agonizing hours of transport, installation and assembly, including many anticipatory concerns, an implosion bomb using plutonium was installed in a tower and detonated on 16 July 1945. The yield was calculated to have been 18.6 KT.

Shortly before the Trinity test the cruiser U.S.S. Indianapolis departed from San Francisco carrying most of the components of what was to be the first atomic bomb dropped on Japan. The bomb was a gun-type weapon called Little Boy. Its destination was Tinian, where the 509th Composite Group was based. Other components of Little Boy were carried from an Army Air Forces base in Albuquerque to Tinian by C-54 aircraft. Components of another bomb, an implosion weapon called Fat Man, intended to be dropped on a second Japanese city, were also carried to Tinian by C-54 and B-29 aircraft.

The directive releasing the atomic bomb for use was sent to General Carl Spaatz, commander of the Strategic Air Force in the Pacific. The directive had been approved by Secretary of War Henry Stimson and Army Chief of Staff George Marshall, and presumably by President Truman. It listed the targets to be attacked and included Hiroshima and Nagasaki, among others and it referred to the possible use of more than one bomb. Hiroshima was an industrial area with a number of military installations. Nagasaki was a major port with shipbuilding and marine repair facilities. In general, the participants in the decision to use multiple bombs considered that such employment would enhance the psychological effect on the Japanese government and would be conducive to ending the war without the need for an invasion, a paramount objective.

On August 6, 1945, the B-29 Enola Gay carrying Little Boy and piloted by the commander of the 509th Composite Group, Colonel Paul Tibbets, dropped its bomb on Hiroshima, destroying most of the city and causing possibly 140,000 deaths. The weather over the target was satisfactory, and the bombardier, Major Thomas Ferrebee, was able to use a visual approach. The bomb's detonation point was only approximately 550 feet from the aiming point, the Aioi Bridge, an easily identifiable location near the center of the city. The yield of the bomb was 12.5 KT.

On August 9, another B-29, Bock's Car , piloted by Major Charles Sweeney, dropped Fat Man on Nagasaki. The primary target for Bock's Car had been the arsenal city of Kokura, but cloud conditions necessitated selection of the secondary target, Nagasaki. Bomb delivery was successful although broken cloud cover necessitated a partial radar and partial visual approach. The number of deaths at Nagasaki was approximately 70,000, less than at Hiroshima because of steep hills surrounding the city. The yield was 22 KT.

On August 15 the Emperor of Japan broadcast his acceptance of the Potsdam Proclamation, which on July 26, 1945, had set forth the Allies' terms for ending the war. In his address to the nation the Emperor cited that the Americans had "begun to employ a new and most cruel bomb, the power of which to do damage is indeed incalculable" and that this, along with the "war situation," was the reason for his accepting the surrender terms.

Rhodes, Richard. 1987. The Making of the Atomic Bomb . Simon and Schuster.
Tibbetts, Paul W. 1978. The Tibbetts Story . Stein and Day.

Producing Results

The famous photo of the Trinity test, taken by Jack Aeby.

On July 16, the atomic age officially began when the world’s first atomic bomb was tested at the Trinity site in the New Mexico desert. The “Gadget” plutonium bomb exploded with approximately 20 kilotons of force and produced a mushroom cloud that rose eight miles high and left a crater that was ten feet deep and over 1,000 feet wide.

On August 6, the United States dropped its first atomic bomb on Hiroshima. Known as “Little Boy,” the uranium gun-type bomb exploded with about thirteen kilotons of force. The B-29 plane that carried Little Boy from Tinian Island in the western Pacific to Hiroshima was known as the Enola Gay, after pilot Paul Tibbets' mother. Between 90,000 and 166,000 people are believed to have died from the bomb in the four-month period following the explosion. The U.S. Department of Energy has estimated that after five years there were perhaps 200,000 or more fatalities as a result of the bombing, while the city of Hiroshima has estimated that 237,000 people were killed directly or indirectly by the bomb's effects, including burns, radiation sickness, and cancer.

Three days later, a second atomic bomb was dropped on Nagasaki – a 21-kiloton plutonium device known as "Fat Man.” It is estimated that between 40,000 and 75,000 people died immediately following the atomic explosion, while another 60,000 people suffered severe injuries. Total deaths by the end of 1945 may have reached 80,000. Japan surrendered on August 14.

The debate over the bomb – whether there should have been a test demonstration, whether the Nagasaki bomb was necessary, and more – continues to this day.

Facts about Atomic Bombs 7: Germany

Germany did not experience the massive destruction because they already surrendered in the World War II. However, Japan was very persistent. They did not want to lose. Therefore, US invaded Japan and Truman who was the president of US decided to drop the atomic bomb in Hiroshima and Nagasaki. It was one of the deadliest wars in the history.

Facts about Atomic Bombs 8: the bomb in Hiroshima

Little Boy was the name of the atomic bomb dropped in Hiroshima Japan on 6 august 1945. There were 10,000 people killed during the explosion.

Atomic Bomb in Hiroshima and Nagasaki

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10 Inventors Who Came to Regret Their Creations

Just because someone's invented something, it doesn't mean that they're happy with the end result.

1. J. Robert Oppenheimer — The atomic bomb.

It's J. Robert Oppenheimer who, as director of the Los Alamos Laboratory during World War II, is credited with the creation of the atomic bomb.

Despite past associations with left wing organizations, Oppenheimer welcomed the opportunity to play a part in the war effort. Later, however, he had mixed feelings about the bomb. "I have no remorse about the making of the bomb … As for how we used it, I understand why it happened and appreciate with what nobility those men with whom I'd worked made their decision. But I do not have the feeling that it was done right. The ultimatum to Japan [the Potsdam Proclamation demanding Japan's surrender] was full of pious platitudes. . our government should have acted with more foresight and clarity in telling the world and Japan what the bomb meant," he said.

Albert Einstein, whose work made the bomb possible but who had no role in developing actual weapons, was less equivocal. He believed Germany was attempting to create an atomic bomb to use against the Allies in World War II, and he signed a letter to President Franklin Roosevelt encouraging him to support U.S. research into producing one as well. Years later, he regretted it. "Had I known that the Germans would not succeed in producing an atomic bomb," he said, "I would have never lifted a finger."

2. Mikhail Kalashnikov — AK-47.

Kalashnikov designed the rifle that bore his name for the Russian army at the end of the Second World War after witnessing terrible casualties in battle and being injured himself. Designed to be a simple automatic rifle that could be made cheaply using the mass production methods available at the time, Kalashnikov, who died in 2014, lived long enough to see his creation be responsible for more deaths than any other assault rifle.

"I keep coming back to the same questions. If my rifle claimed people’s lives, can it be that I…, an Orthodox believer, am to blame for their deaths, even if they are my enemies?" he wrote in a letter to the head of the Russian Orthodox church in 2010.

3. Tim Berners Lee — the double slash.

Given what Sir Tim did for all of us when he developed HTML and created the World Wide Web, he's got a fair amount of credit in the bank. If he did have any major regrets about the web, we wouldn't find it too difficult to forgive him, but his mea culpa relates to only two characters, the '//' at the beginning of every web address. "Really, if you think about it, it doesn't need the //. I could have designed it not to have the //," he said, according to Business Insider.

4. Ethan Zuckerman — the pop-up advert.

If you've ever found yourself yelling at your computer screen in frustration as yet another pop-up ad leaps into view, obscuring the content behind it, Zuckerman is the person to blame.

Now head of the Center for Civic Media at the Massachusetts Institute of Technology, Zuckerman wrote an essay for The Atlantic last year entitled "The Internet’s Original Sin," in which he took full responsibility for the pesky blighters. Working as an employee of web host Tripod at the time, Zuckerman explained that the company, which provided free web pages for consumers, had spent five years looking for a way to generate revenue.

"At the end of the day, the business model that got us funded was advertising. The model that got us acquired was analyzing users’ personal homepages so we could better target ads to them. Along the way, we ended up creating one of the most hated tools in the advertiser’s toolkit: the pop-up ad."

Explaining that the intention had been to allow adverts to appear when users visited a page without necessarily associating the advert with the content of the page, Zuckerman explained, "We came up with it when a major car company freaked out that they’d bought a banner ad on a page that celebrated anal sex. I wrote the code to launch the window and run an ad in it. I’m sorry. Our intentions were good."

5. Dong Nguyen — Flappy Bird.

Flappy Bird was a sensation a year ago. What looked like a crude and simple game proved to be hugely addictive thanks to it hitting that sweetspot between infuriatingly difficulty and being just playable enough to make you think that next time you'll do better. Downloads soared and controversy raged until, after 50 million downloads and advertising revenue that was hitting around $45,000 a day, Nguyen had had enough and announced that he was going to withdraw it from app stores. "I cannot take this anymore," he tweeted. Apparently, the publicity generated by the game had attracted the attention of the world's press and Nguyen was bombarded with calls, tweets, and emails.

The removal of the game from app stores did little to quell the publicity. Nguyen received death threats, while phones with the game already installed sold on eBay for small fortunes, and app stores were flooded with copycat titles.

6. Bob Propst — the office cubicle.

While working as a consultant for Herman Miller in the 1960s, Bob Propst introduced America to the open plan office and with it, the office cubicle. It was, he told the New York Times in 1997, designed to "give knowledge workers a more flexible, fluid environment than the rat-maze boxes of offices."

Companies saw his invention as a way to save money, doing away with individual offices and replacing them with open plans and cubicles. Propst came to lament his invention. "The cubiclizing of people in modern corporations is monolithic insanity," he said.

7. Vincent Connare — Comic Sans.

"If you love it, you don't know much about typography." An anonymous critic of the font Comic Sans didn't say that, for those are the words of its designer, Vincent Connare, talking to the Wall Street Journal. Connare followed up that comment, however, with this: "If you hate it, you really don't know much about typography, either, and you should get another hobby."

Connare's view, and one shared by lots of others, is that the problem with Comic Sans is not with the font itself, but its overuse and misuse. Designed for a Microsoft application aimed at children to be used as a replacement in speech bubbles for Times New Roman, Connare never imagined it would become so widely used and derided.

8. Tom Karen — Raleigh Chopper.

Before the BMX arrived on the scene in the late 1970s, if you wanted a bike that wasn't of the drop-handlebarred racing variety, Raleigh's Chopper (pictured up top) was one of the few options. Loved by millions for its comfortable saddle, laid-back seating position, and those huge Harley Davidson-esque handlebars, it was one of Raleigh's best-selling bikes in the 1970s.

However, its designer, Tom Karen, wasn't enthusiastic when a comeback for the Chopper was mooted last year. He told The Telegraph: "The Chopper wasn’t a very good bike. It was terribly heavy so you wouldn’t want to ride it very far. There was some guy who rode it from Land's End to John O’Groats for a good cause and by the end he was cursing it."

9. Kamran Loghman — Pepper spray.

Kamran Loghman worked for the FBI in the 1980s and helped turn pepper spray into weapons grade material. He also wrote the guide for police departments on how it should be used. The spray has been used numerous times by police in the US, but following an incident at the University of California in 2011 when police sprayed the bright orange chemical on what the New York Times described as "docile protestors," Loghman spoke out. "I have never seen such an inappropriate and improper use of chemical agents," he told the Times.

10. John Sylvan — Coffee capsules.

When John Sylvan invented coffee pouches and machines which could turn them into steaming cups of joe, he had no idea of the monster he had created. Sylvan's invention gave rise to systems like Nespresso and Tassimo and made it easier than ever for millions of us grab a regular caffeine fix. "I feel bad sometimes that I ever did it," he said a few years ago. "It's like a cigarette for coffee, a singleserve delivery mechanism for an addictive substance."

Albert Einstein’s Involvement

Many people refer to Albert Einstein as the inventor of the bomb, but this is actually very far from true. Apart from coming up with the Relativity Theory E=mc2, stating that a small amount of matter could release a lot of energy, Albert Einstein’s only involvement in the development of this weapon of mass destruction was to sign a letter, urging the U.S. to develop the bomb. This was a decision Einstein, as a pacifist, had great regrets about. Physicists Eugene Wigner and Leo Szilard convinced Einstein to sign the letter because they knew that Germany had managed to split the uranium atom and they were fearing that Germany was already working on an atomic bomb.

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