Manhattan Project - U.

Manhattan Project - U.S. History. I INTRODUCTION Manhattan Project, the name given to the United States effort--strongly aided by the United Kingdom--to build the atomic bombs that helped end World War II (19391945). The Manhattan Project ranks as the largest industrial and scientific effort in the history of the world, costing more than $2 billion in 1945 dollars and involving more than 175,000 workers. All research and experiments were conducted in almost total secrecy. Only a relatively small number of people knew the exact purpose of the project, which created the most powerful weapon ever used. The Manhattan Project ushered in a new era in human history known as the Atomic Age. It demonstrated the feasibility of atomic energy for both peaceful and military uses. It also led to an arms race that, according to many scientists, produced enough nuclear weapons to destroy human civilization and end most forms of life on Earth. See also Arms Control; Nuclear Energy; Nuclear Weapons Proliferation. The Manhattan Project began in 1942. It officially ended in 1946 when it became part of the Atomic Energy Commission (AEC). Originally based in Manhattan, a borough of New York City, the project eventually spread across the nation and was concentrated at three main sites located in Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. Its director was Brigadier General Leslie R. Groves. American physicist J. Robert Oppenheimer was the scientific director at Los Alamos, which attracted some of the most brilliant scientists and mathematicians of the 20th century. Among the scientists and mathematicians who participated in the Manhattan Project were Philip H. Abelson, Hans Bethe, Niels Bohr, Sir James Chadwick, Enrico Fermi, Richard Feynman, Otto Frisch, George Kistiakowsky, Ernest Lawrence, Philip Morrison, Seth Neddermeyer, John von Neumann, Rudolf Peierls, I. I. Rabi, Leo Szilard, Edward Teller, Stanislaw Ulam, Harold Urey, and Victor Weisskopf. Five of these scientists had already won Nobel Prizes when the project began, and three more would later go on to win Nobel Prizes. The Manhattan Project produced four atomic bombs. One was tested July 16, 1945, at a bombing range site known as Trinity near Alamogordo, New Mexico. Two others were dropped on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945. A fourth was ready for use in late August, but by then Japan had surrendered and World War II had ended. II ORIGINS OF THE MANHATTAN PROJECT The origins of the Manhattan Project can be traced to the scientific laboratories of Britain and Europe in the early 1900s. At that time, the basic unit of matter, the atom, was viewed as solid and impossible to divide. The startling discoveries of radium; the X ray; the electron, proton, and neutron; and alpha, beta, and gamma rays, however, alerted scientists to the existence of a "subatomic" world. As British physicist Ernest Rutherford and Danish physicist Niels Bohr suggested, instead of being solid, the atom resembled a "miniature solar system." Within the atom negatively charged electrons orbited positively charged protons and electrically neutral neutrons in the atom's nucleus. Scientists knew well that the atoms of each chemical element differed from one another. Hydrogen, which consists of one electron orbiting one proton, is the simplest. Scientists classify hydrogen with the atomic number one. Uranium, with 92 electrons orbiting a nucleus with 92 protons, is the most complex of the natural elements. It has the atomic number 92. In addition, these elements often contain variations--called isotopes--that occur because they have different numbers of neutrons bound to the protons in the nucleus. For example, the element uranium has three isotopes, known by their atomic numbers, U238, U235, and U234. The numbers are derived by adding the number of protons in the uranium nucleus, 92, with the number of neutrons in the nucleus. U238 is the most common form of uranium; the rare U235 isotope forms only about 0.7 percent of naturally occurring uranium. Because uranium appeared to be an unstable element, scientists began to bombard it with streams of neutrons, hoping to discover a new form of energy. The 1930s saw major breakthroughs in understanding the atom. In 1933 Hungarian-born physicist Leo Szilard, who had fled Nazi Germany for England, was standing on a London street corner waiting for the light to change. Suddenly he realized that if the right material were found, splitting the nucleus of an atom could release neutrons and cause a nuclear "chain reaction" in which the released neutrons would cause more atoms to split, or fission. The result would be a self-sustaining series of fissions, causing a continuous release of nuclear energy. Such a chain reaction could be used to produce either electricity or a bomb. The next year Szilard filed a British patent on this subject, but kept it secret out of fear that German scientists might learn it was possible to make an atomic bomb. Meanwhile, in 1933 in Paris, French scientists Irène Joliot-Curie and her husband Frédéric Joliot discovered artificially created radioactivity. Shortly afterwards in Rome, Italian physicist Enrico Fermi created the first artificially created elements (beyond uranium). Fermi also split the atom, but at the time he did not realize what had occurred. In Berlin, Germany, physical chemists Otto Hahn and Fritz Strassmann repeated Fermi's experiments, bombarding uranium with neutrons. In late 1938 they were baffled when they found traces of barium in their results. Hahn wrote to his longtime scientific partner, Lise Meitner, to ask her opinion. Meitner was probably the foremost woman scientist of her generation. She had been forced to flee Germany due to the anti-Semitic laws enacted by the Nazi regime of Adolf Hitler (see National Socialism). Meitner and her nephew, physicist Otto Frisch, concluded in a December 1938 discussion that the two German scientists had split the uranium atom's nucleus virtually in half. As a result of splitting the uranium atom, barium with the atomic number 56 and krypton with the atomic number 36 were formed. Added together they represented the 92 protons in the uranium atom's nucleus. Frisch was the first to name this process "fission." (See the Sidebar with this article, "The Discovery of Fission.") Meitner and Frisch provided a theoretical explanation for Hahn and Strassmann's results and argued that the experiments confirmed Bohr's model of the atom. When the uranium atom split or fissioned, it released an enormous amount of energy. How much energy could be calculated by using the famous formula of Austrian-born physicist Albert Einstein, E =mc2. In this formula E is energy, m is mass, and c is the speed of light squared. Since the speed of light--300,000 km/sec (186,000 mi/sec)--is such a large number, very little mass is required to produce a great deal of energy. Moreover, if each fission released additional neutrons in the process, a nuclear chain reaction would be possible. Meitner and Frisch raced to Copenhagen, Denmark, to inform Bohr, who was preparing to leave for a physicists' conference in Washington, D.C., in January 1939. As soon as the scientists in Washington learned that uranium could be fissioned, several rushed to their laboratories to repeat the experiment. Within a year, more than 100 scientific papers had appeared on nuclear fission. When Szilard first heard the news of uranium fission, he predicted that the world was "headed for grief." By 1939 a small group of scientists was well aware that a weapon of terrible power was possible--at least in theory. III THE BUILDING OF THE ATOMIC BOMB A The British Effort In early 1939 most nuclear scientists believed that from 50 to 180 tons of natural uranium, containing only a tiny percentage of U235, would be required for a chain reaction to occur and an atomic bomb to be built. However, it was not practical to build a bomb weighing 50 tons. As a result most scientific research concentrated on other possible uses of nuclear energy, such as using uranium to operate large power plants or, perhaps, as power sources for ships or submarines. Then Nazi Germany invaded Poland on September 1, 1939, and Europe plunged into war. The scientists realized that any plans to build large-scale nuclear power plants would have to wait until the war was over. Two weeks after the invasion of Poland, Hitler made a radio speech in which he threatened Britain with "a weapon against which there is no defense." British intelligence officers monitored this speech and came up with four possible interpretations: (1) Hitler was bluffing, (2) the Nazis had developed a deadly poison gas, (3) Hitler was referring to the German Air Force, the Luftwaffe, or (4) the Germans had developed an atomic bomb. In the fall of 1939 British intelligence could neither confirm nor deny the existence of a German atomic weapon. Thus, Prime Minister Winston Churchill decided that Britain should take no chances, and he instructed British scientists to investigate this possibility. Because most of Britain's scientists were already occupied with other work, the job fell to two refugee German physicists who had fled Nazi Germany but were not yet British citizens: Otto Frisch and Rudolf Peierls. After intense study the two men produced the March 1940 Frisch-Peierls Memorandum. This brief scientific paper concluded that only the U235 isotope fissioned--rather than the more abundant U238. Consequently, if U235 could be separated from U238, then only a relatively small amount of U235 would be needed for a chain reaction to occur. Fifty tons of natural uranium would not be required to make a bomb. Instead, a bomb could be made by utilizing about a kilogram of U235 (later revised upward to about 10 kg [22 lb]). Although it would be difficult, scientists could separate U235 from U238 using industrial techniques. The two scientists warned, however, that Britain might not wish to use this bomb because of the radioactive fallout that would occur. Churchill's government immediately formed a top-level committee to further examine the report. In 1941 this committee concluded that although the bomb program might cost as much as a battleship, Britain should pursue it. "I wish I could tell you that the bomb is not going to work," British scientist Sir James Chadwick told two American scientists, "but I am 90 percent certain that it will." By 1940 British scientists viewed the possibility of creating an atomic weapon with utmost seriousness. But German bombers could easily reach British targets, and Churchill knew that Britain could never build the gigantic factories necessary to produce such bombs. Any new building of that size would be quickly spotted and destroyed by the Luftwaffe. So the British effort remained largely at the theoretical level. B The U.S. Program The U.S. atomic bomb program moved at a somewhat slower pace. Early in 1939 various émigré scientists living in the United States steadily campaigned for increased U.S. nuclear research. They met so many obstacles, however, that they felt they were "swimming in syrup," as the refugee Hungarian physicists Eugene Wigner and Leo Szilard put it. In July 1939 Szilard, Wigner, and another refugee Hungarian physicist, Edward Teller, conferred on the best way to gain the attention of the U.S. government. They decided on a plan to have the world's most famous scientist, fellow refugee Albert Einstein, write a letter to President Franklin D. Roosevelt. The three men met with Einstein at his summer home on Long Island. Einstein later signed his name to a letter, dated August 2, 1939, that officially warned Roosevelt of a new type of bomb. Hidden in the hold of a ship, such a bomb could easily destroy a harbor city. At the time no one dreamed that an atomic bomb could ever be dropped from an airplane. (See the Sidebar, "Einstein's Letter to Franklin D. Roosevelt.") Alexander Sachs, an acquaintance of the scientists who was on familiar terms with Roosevelt, delivered the letter on October 11, 1939, a month after the Nazi invasion of Poland. Although Roosevelt knew little about science, he immediately established an Advisory Committee on Uranium to look into the matter. In June 1940 an even more important National Defense Research Committee came into being, followed by the Office of Scientific Research and Development on June 28, 1941. Still, the Americans never displayed the same fear or sense of urgency as the British until Japan attacked Pearl Harbor on December 7, 1941. Suddenly the United States was at war with Japan and Germany. With this, all discussion regarding an atomic bomb shifted from abstract theory to practical application: The nation that built the atomic bomb first would surely win the war. In the months following Pearl Harbor, the U.S. government completely reorganized its atomic bomb effort by enlisting the aid of the United States Army Corps of Engineers. The project shifted from a program dominated by scientists in university laboratories to a gigantic, nationwide construction project under the Corps of Engineers' Manhattan Engineer District (hence the name "Manhattan Project"). Brigadier General Leslie R. Groves, an able engineer who had helped build the Pentagon, assumed overall charge of the project. Groves insisted on a complete refocus for all nuclear research. All discussion of postwar power plants or individual power sources for airplanes, ships, or submarines had to cease. From then on, the project had only one goal: to create an atomic weapon to end the war in the shortest possible time. Groves began by enlisting the aid of several large American corporations, including Chrysler, General Electric, Eastman Kodak, Westinghouse, and DuPont. He also called on numerous universities, such as the California Institute of Technology in Pasadena, Columbia University in New York City, the University of Chicago, the Massachusetts Institute of Technology (MIT) in Cambridge, and the University of Rochester in New York, to conduct further nuclear research. Finally, he oversaw the creation of three gigantic federal installations at Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. The race to beat the Nazis to the secret of the atomic bomb had begun in earnest. Groves did not assume control of the project until the fall of 1942, by which time the United States had been at war with the Axis powers for almost nine months. Bold newspaper headlines followed the fortunes of the U.S. Army, Navy, and Marines on a daily basis. Americans read in detail about the fierce battles in Europe and the Pacific. But the Manhattan Project moved along a completely different track. Groves forbade any publicity about its research and insisted on the "compartmentalization" of knowledge for all project workers. This meant that a person knew only enough to do his or her task, but no more. This proved frustrating, for ordinary workers as well as for the top-level scientists. Still, a strict "culture of secrecy" blanketed the entire project. Meanwhile, the scientists continued their research at a furious pace. Enrico Fermi moved his experiments from Columbia University to the Metallurgical Laboratory (Met Lab) at the University of Chicago, which loaned him a squash court under the unused Stagg football stadium. There Fermi and his crew assembled a gigantic pile of uranium and graphite blocks that reached almost to the ceiling. Fermi had discovered that graphite could be used to moderate, or control, a chain reaction. On the afternoon of December 2, 1942--almost four years after Bohr had brought the news of uranium fission to the United States--Fermi oversaw the world's first controlled release of nuclear energy. The pile produced only enough energy to light a small flashlight, but all the scientists' theories had proven correct: Humankind had created, and, for the moment controlled, the release of atomic energy. All atomic weapons and all nuclear power plants trace their ancestry to this moment. Fermi's successful experiment reassured the scientists that they were on the right path, but the technical problems that lay ahead were enormous. General Groves later likened the process to a "manufacturer who tried to build an automobile full of watch machinery, with the precision that was required of watchmaking, and the knowledge that the failure of a single part would mean complete failure of the whole project." Perhaps the central hurdle lay with the fact that the most common form of uranium--U238--does not fission. The U235 isotope does fission, but only 1 in every 140 uranium atoms is the isotope U235. Thus, the scientists had to devise a means to separate several pounds of U235 from U238 on an atom-by-atom basis. The separation could not be done by chemical methods because the two isotopes are chemically the same. Instead, they had to be separated physically. B1 Oak Ridge American scientists had devised several possible methods to separate the isotopes, but it was not clear which one, if any, would succeed. Groves therefore decided to try all of them at once. Each method demanded gigantic buildings surrounded by a great deal of space due to safety concerns. One of the Army's first actions was to confiscate 24,000 hectares (59,000 acres) of land in rural eastern Tennessee near the Clinch River. During the war this was called Site X, but later it became known as the Oak Ridge National Laboratory. Site X held everything Groves needed: a large nearby workforce, sufficient water, and a mild climate that would allow work to continue uninterrupted. Oak Ridge contractors immediately began to build the K-25 plant, the largest building ever constructed up to that time. Drawing as much electrical power as New York City, K-25 used the gaseous diffusion method to separate the uranium isotopes. This process proved both complex and dangerous. Uranium is usually a metal, but here it was turned into a gas and forced by pumps through porous barriers with millions of submicroscopic holes. The barriers acted, in effect, as specially designed filters. Because U235 is slightly lighter than U238, it moved through the filters at a somewhat faster pace, causing the uranium gas on one side of the filter to be "enriched" by a higher rate of U235. But a single filter was not enough. Thousands of pumps pushed the gas through thousands of filters, traveling through hundreds of kilometers of interlocking pipes. Although difficult to maintain, the end result produced a gas much enriched with fissionable isotopes that could be converted back into a metal. About 12,000 workers, many of them women because so many men were serving in the military, oversaw this process. None of the workers were told the purpose of the K-25 plant for reasons of secrecy. They only knew it was something that would help win the war. On the southern edge of Site X, construction workers erected another gigantic building called Y-12. It utilized an electromagnetic separation method, drawing on what was then the world's largest magnet, weighing 4,900 tons. If scientists gave an electrical charge to a gaseous uranium compound, a process called ionization, the lighter U235 atoms would follow a different arc through a magnetic field than the heavier U238 atoms. The U235 atoms could be "bent" by the magnet into a separate path and collected. This equally gigantic operation employed 23,000 workers, but none of them knew the purpose of their work either. Oak Ridge turned into a Tennessee boomtown, becoming the fifth largest city in Tennessee. Wartime life at Oak Ridge seemed unreal. Gigantic factories, each costing from $400 million to $500 million to build, ran 24 hours a day to produce nothing (it seemed) that could be heard, seen, smelled, or touched. Only after the war did the Oak Ridge workers learn that the K25 and Y-12 plants had produced the fissionable uranium for the atomic bomb dropped on Hiroshima, Japan. Oak Ridge also housed a third plant called X-10, which drew on yet-another method to create fissionable materials. In 1941 scientists had discovered that when U238 absorbs a neutron, it eventually decays into plutonium, which, like U235, can also fission. The slightly smaller building at X-10 served as a pilot plant to produce plutonium, but this process was exceptionally dangerous. Groves feared that the city of Knoxville lay far too close to Oak Ridge, so he decided to move the full-scale plutonium production plant to a remote location in Washington State. B2 Hanford In early 1943 the full-scale plutonium production facility began in isolated southeastern Washington, near the Columbia River. During the war, it was called Site W, but later it became known as the Hanford Engineer Works. Within a few months, the Army confiscated thousands of hectares of land, much of it consisting of small fruit ranches. Within two years, Hanford grew from a community of several small villages to become the fourth largest city in Washington with a population of more than 50,000. Unlike Oak Ridge, the Hanford region was so sparsely populated that it could not draw on the local area for workers. The Army had to advertise throughout the West. With the offer of high wages, thousands of male workers--and relatively few women--accepted jobs there. Soon Hanford boasted the biggest trailer park in the world, larger crowds at local baseball games than attended some major league contests, and kitchens that served around 60 tons of food per meal in seemingly endless dining rooms. Most of the men arrived without their families, and a number engaged in barroom brawls on Saturday nights in an atmosphere that resembled a 19th-century gold mining camp. When one frustrated worker asked his Army boss what the project was for, the official said, "If I told you, I would be court-martialed immediately." Hanford existed for one reason: to build and operate the gigantic piles (later called reactors) to produce plutonium for a second atomic bomb. Workers constructed three huge water-cooled piles--named B, D, and F--about 10 km (6 mi) apart. In these buildings, streams of neutrons bombarded concentrations of U238 known as slugs to produce plutonium. The irradiated slugs were then taken by remote-controlled railway cars to one of two gigantic chemical separation buildings--called Queen Marys--where operators sat behind thick concrete walls to separate the plutonium from the U238 via remote-controlled equipment, television monitors, and even periscopes. It was a dull and boring task. B3 Los Alamos The uranium from Oak Ridge and the plutonium from Hanford both ended up at the third secret Manhattan Project location--Los Alamos, New Mexico, or, as it was known during the war, Site Y. Nestled on 2,100-m-high (7,000-ft-high) mesas in north-central New Mexico, the region served as summer forage for local cattle and sheep ranchers and as home to an exclusive prep school for wealthy boys. Again the Army confiscated thousands of hectares and began construction in early 1943 of what later became the most high-profile of all the Manhattan Project locations. The isolation of Los Alamos served many purposes. In the beginning, the top-level scientists--all of whom knew the goals of the Manhattan Project--were often as frustrated by the Manhattan Project's compartmentalization as the lower-level workers who were unaware of the ultimate goal. The scientists urged Groves to provide a secure location where they could discuss everything, and Groves eventually agreed. The newly appointed scientific director, California physicist J. Robert Oppenheimer, spent much of early 1943 trying to convince the nation's top scientists and engineers to move to Los Alamos for the duration of the war. Los Alamos also provided the location for British and U.S. scientists to confer. At a conference in Québec, Canada, in August 1943 between Britain and the United States, Churchill had persuaded Roosevelt to collaborate on building the bomb. Following the Québec Agreement, a team of about 20 top-level British scientists--including Chadwick, Peierls, Frisch, Bohr (who had become a consultant to the British effort), and Klaus Fuchs, along with Canadian scientist J. Carson Mark--moved to Los Alamos. The task at Los Alamos was to create a combat-ready atomic bomb using the fissionable material supplied by Oak Ridge and Hanford. Los Alamos became the most mysterious of all the Manhattan Project installations. A wire fence surrounded the town, patrolled by armed guards on horseback. A pass was necessary to enter or leave, and Army security examined all packages and mail. The town lacked even an address. All deliveries went to "Box 1663, Sandoval County, Rural." Many hotel staff workers and waitresses in nearby Santa Fe and Albuquerque were really U.S. Army Intelligence people in disguise. Several of the more important scientists went by false names (Fermi was "Mr. Farmer"), and a number of them had full-time bodyguards. All scientists wearing white badges met every Tuesday for a no-holds-barred discussion of the project, but others in Los Alamos knew very little. Laura Fermi, Enrico's wife, admitted that until the bomb was dropped at Hiroshima, she did not know the purpose of Site Y. Life moved at a feverish pitch in wartime Los Alamos. The scientists worked 10 to 12 hours a day, six days a week, in a desperate effort to outthink the enemy. Because the scientists at Los Alamos had made such rapid strides toward creating a bomb, they were certain the Germans were moving with equal speed to create theirs. Eventually, the Los Alamos scientists devised a relatively simple bomb design for the U235 weapon, nicknamed Little Boy. The design resembled a gun and was known as a gun assembly system. This bomb fired one subcritical piece of U235, in which there was not enough matter to cause a chain reaction, into another subcritical piece of U235. When the two subcritical pieces met, there was enough mass--known as critical mass--for a chain reaction to occur. This became the bomb dropped on Hiroshima. Research discovered, however, that the "gun method" would not work with plutonium. The two subcritical pieces detonated too quickly. Physicist Seth Neddermeyer and mathematician John von Neumann devised an alternative method that they called implosion. In this extremely complex arrangement, the scientists surrounded a grapefruit-sized sphere of plutonium with ordinary explosives, shaped into "lenses." When the lenses detonated, the blast "squeezed," or imploded, the plutonium to the size of a walnut, which then obtained the critical mass necessary to explode with atomic force. Scientists termed this weapon Fat Man--a reference to Winston Churchill. The implosion bomb proved so complex that the Los Alamos scientists insisted on a test before dropping it in a combat situation. After careful consideration, the scientists chose a section of the Alamogordo Bombing Range, in the central part of New Mexico, as the test site. In a frenzy of activity, workers created the world's largest outdoor laboratory at a spot Oppenheimer named Trinity Site. In addition to numerous buildings, they erected a 30-m (100-ft) steel tower at "ground zero" (the place where the bomb would explode), hoisted the bomb (called "the gadget") to a platform on the top, and scheduled the test for the early morning of July 16, 1945. At first the weather refused to cooperate. A fierce summer storm blew in from the south to drench Trinity Site with torrential rain during the night. The scientists hoped to avoid rain at all costs, fearing a downpour might wash the radioactivity out of the bomb's exploding cloud in deadly doses. The wisdom of the day suggested that without rain, a prevailing wind would spread a small dose of radiation over a large area, causing little permanent harm to anyone. Groves consulted with the head meteorologist who predicted the storm would end by dawn, and so the test, originally scheduled for 4 C AM, was rescheduled for 5:30 AM. The First Atomic Explosion It is hard to imagine a more dramatic scene than the predawn hours at Trinity Site on July 16. If the gadget exploded in the relatively low range of 3,000 tons of TNT, it would be only slightly more powerful than a standard "blockbuster" weapon, hardly worth the enormous expense and effort. If the bomb were a "dud," the Manhattan Project would rank as the most costly industrial failure of all time. On the other hand, some scientists speculated that if the blast exceeded expectations, it could conceivably ignite Earth's atmosphere and end all life as we know it. At the local time of 5:29:45 AM, July 16, 1945, the atomic age began at Trinity Site. The blast vaporized the steel tower, tore huge chunks out of the earth, and shattered windows 200 km (125 mi) away. A gigantic multicolored mushroom cloud rose to an altitude of 12,000 m (40,000 ft) within minutes and began to drift slowly to the northeast. Where the ball of fire touched the earth, it fused the sand into a radioactive greenish-gray glass--later named Trinitite--that resembled "a sea of green." All living things within the radius of a kilometer--birds, plants, snakes, lizards, rodents--were instantly incinerated. Wild antelope ran terrified in all directions. The yield was estimated at around 20,000 tons of TNT. Since the blast was visible in three states--indeed, it could have been seen from the Moon--one might expect that news about it would dominate the headlines. But U.S. Army security had instructed all regional newspapers to print only the "official" version of the events, which was that an ammunition dump had exploded accidentally. At first the scientists who observed the blast were overjoyed. They had cracked the secret of atomic weapons. Germany had surrendered on May 7, 1945, and the war against Japan would soon be over. No nation could withstand the power of such a weapon. But within moments, several scientists began to have second thoughts. Fermi became temporarily ill from the stress and worry. Oppenheimer at first remarked that his confidence in the human mind had been restored, but later, quoting from the epic Hindu poem, the Bhagavad-Gita, he solemnly observed, "Now I am become Death, the destroyer of worlds." James Tuck of the British Mission summed up the thoughts of many who watched the cloud roil the summer sky: "What have we done?" The news of the success at Trinity was immediately cabled to officials in Washington, D.C., who sent it on to President Harry S. Truman. Truman was in Germany meeting with Soviet and British leaders at the Potsdam Conference to discuss the best way to end the war with Japan. Truman read the report with delight, but he did not immediately inform the Soviets, who had been excluded from the Manhattan Project. Instead, he later casually mentioned to Soviet premier Joseph Stalin that the United States had developed a powerful new weapon. Stalin, just as casually, according to Truman's memoirs, said he hoped it would be put to good use against the Japanese. Although Soviet spies had gathered some information on the Manhattan Project, scholars are still debating how much Stalin actually knew when Truman first told him about the Trinity Site explosion. IV THE USE OF ATOMIC BOMBS In early June 1945, a blue-ribbon committee had gathered in Washington, D.C., to decide how the bomb should be used. The committee debated dropping it on an unoccupied island in Tokyo Bay as a way of demonstrating to Japan how powerful the weapon was, but that view was rejected. Officials feared that Japan might put American prisoners of war on the island. In a worst-case scenario, some officials suggested that the bomb might not explode at all and somehow the enemy would redrop it on America. Placing an emphasis on the "shock value" of the bomb, the committee decided on an unannounced drop on one or more of four Japanese targets: Kokura, Hiroshima, Niigata, and Ky?to. Secretary of War Henry Stimson vetoed Ky?to because of its role as a revered Japanese cultural center, and Nagasaki replaced it on the list. In the meantime, another committee headed by Met Lab physicist James Franck strongly urged an announced drop on an uninhabited Japanese island. This committee argued that a surprise atomic bomb would almost certainly create a postwar nuclear arms race with the Soviet Union. But this view received little hearing. From Germany, the Allies issued the Potsdam Declaration, which did not mention the atomic bomb but threatened Japan with "complete and utter destruction" if it did not immediately surrender without any conditions. The Allies delivered the Potsdam Declaration through official channels and also dropped millions of leaflets over Japan's four main islands. The official Japanese response was interpreted as "ambiguous." On August 6, 1945, a specially prepared B-29 bomber, the Enola Gay, piloted by Colonel Paul Tibbets, left the island of Tinian for the primary target of Hiroshima. At 8:15 AM the plane dropped the 4,400 kg (9,700 lb) Little Boy uranium bomb that detonated 580 m (1,900 ft) above the city. The blast, which equaled approximately 15,000 tons of TNT, destroyed virtually everything within a 13-sq-km (5-sq-mi) area. It killed about 70,000 people instantly, severely injuring another 70,000 more. By 1950 the death toll had climbed to around 200,000 because of widespread radiation illness. A new era in world history had begun. Shortly afterwards, President Truman announced to the world that a new atomic weapon had been dropped on Hiroshima. He warned that unless Japan surrendered, more would follow. The Japanese cabinet fiercely debated the issue but could come to no agreement. On August 7 and 8, U.S. aircraft continued to drop thousands of conventional bombs on Japan. On August 9, a second specially prepared B-29 named Bock's Car left the island of Tinian carrying the Fat Man plutonium bomb. The primary target was a weapons arsenal at Kokura, but pilot Charles Sweeney found the city covered with clouds. (Groves had insisted that the skies be clear before any drop.) After making three passes over Kokura, Sweeney headed to Nagasaki, where the cloud cover suddenly broke, and he released the bomb, which detonated about 520 m (about 1,700 ft) over the city. About 40,000 Japanese were killed instantly and another 40,000 severely injured. Eventually, the death toll climbed to about 140,000. (See the Sidebar, "Effects of the Atomic Bombs.") This proved to be the last atomic bomb used in combat. President Truman halted the shipping of a third atomic weapon, a plutonium bomb that was the only remaining atomic bomb in the U.S. arsenal. After negotiating a compromise that allowed Japan to retain its emperor, Japan surrendered on August 14, 1945. The final documents were signed aboard the battleship USS Missouri on September 2. Although the atomic bombs did not exactly win the war with Japan, they clearly brought it to an abrupt end. Almost immediately, people began to debate the necessity and morality of dropping the atomic weapons. The anniversaries of the bombings raise the question anew every year. There is no agreement. Some, such as Truman, have argued that, horrible as they were, the atomic bombs actually saved lives--both Japanese and Allied--because they allowed Japan to surrender with honor. Allied troops did not have to invade the home islands of Japan, with a projected loss of life estimated in the millions. Others, such as Otto Frisch, reluctantly agreed with the decision to bomb Hiroshima but termed the Nagasaki bombing as "unnecessary." Still others have said that the atomic bombs were not needed at all. Japan was ready to surrender, and a test drop on an uninhabited island would have given them the ideal opportunity to do so. Argument over these issues is not likely to end. (See the Sidebar "Was It Necessary to Bomb Hiroshima?") V THE LEGACY OF THE MANHATTAN PROJECT The Manhattan Project shaped the future of the world in ways that no one could have imagined. It led to an arms race between the United States and the Soviet Union, helped create a culture of secrecy and fear--especially in the United States and the Soviet Union--and resulted in the spread of nuclear weapons, the development of nuclear energy for peaceful purposes, and the ongoing problem of how to store radioactive nuclear waste. The world will undoubtedly be dealing with these legacies for a long time to come. A Nuclear Arms Race In 1946 an American committee proposed the creation of an international authority to control "all phases of the development and use of atomic energy." Many scientists who worked on the Manhattan Project helped formulate this plan, which was presented to the newly created United Nations (UN) by American financier and economist Bernard Baruch. Baruch warned of the dangers of nations competing to produce weapons of mass destruction. But the Soviet Union--deeply involved in building its own atomic bomb--refused to cooperate. In 1949 the Soviets detonated their first atomic weapon--virtually identical to the Trinity Site bomb--and the arms race was on. (See the Sidebar "The Baruch Plan.") In the early 1950s as relations between the West and the Soviet Union deteriorated into what was called the Cold War, Britain, the Soviet Union, and the United States also developed thermonuclear or hydrogen bombs, whose explosive power was more than 50 times greater than a standard atomic bomb. Neither the Soviet Union nor the United States dared attack one another for fear of instant retaliation, a situation that was known as mutually assured destruction (MAD). This tense atmosphere evaporated with the dissolution of the Soviet Union in 1991. United States-Russian relations became much more friendly, and the Cold War was declared officially at an end. Nevertheless, the arms race produced so many nuclear weapons that many scientists still fear that any use of the stockpiles could end human civilization as we know it. See also Nuclear Weapons. B A Culture of Secrecy and Fear The secrecy that surrounded the Manhattan Project continued with the start of the Cold War. In 1945 the Allies discovered that the Soviet Union had extensively spied on the project. In late 1949 the British arrested physicist Klaus Fuchs, who had spent time in Los Alamos as part of the British mission. Fuchs eventually confessed to handing over secret data to the Soviets on several occasions, including an exact description of the Trinity Site bomb, as well as early research on the hydrogen bomb. Since Fuchs was then a naturalized British citizen, he was tried in Britain for espionage and in 1950 sentenced to 14 years in prison. Fear that he had assisted a Soviet H-bomb program helped push America to make the political decision to develop hydrogen weapons. The 1950s also produced two other nuclear-related trials. The first involved Julius and Ethel Rosenberg. Ethel's brother, David Greenglass, had worked as a machinist at Los Alamos and had passed crude drawings of atomic bombs to Julius, who gave them to a Soviet courier. When the Federal Bureau of Investigation (FBI) helped crack the Fuchs case, they discovered the Rosenberg/Greenglass espionage, and after a controversial trial, the Rosenbergs were executed in 1953. Later disclosures, following the demise of the Soviet Union, revealed that only Julius Rosenberg had met with the Soviet courier. Opinion remains divided today over whether the Rosenbergs received a fair trial in the anti-Communist witch-hunt hysteria of the time and whether the death penalty was merited, considering that it is rarely invoked in espionage cases in Western countries and considering the questionable usefulness of the information passed to the Soviets. Also debated is the question of whether the prosecution had charged Ethel, despite scant evidence against her, merely in an attempt to gain a confession from Julius. Shortly after the execution of the Rosenbergs, Oppenheimer faced a trial of his own when he was brought before a board of inquiry of the Atomic Energy Commission to explain his early radical political past and to justify his opposition to America's development of the hydrogen bomb. Oppenheimer's left-wing political links had been no secret. Groves knew of them in 1943 but appointed Oppenheimer director of Los Alamos anyway. Yet by the 1950s the fear engendered by the anti-Communist hysteria of the time had made it seem that anyone with left-wing views was a security risk. The board of inquiry voted to remove Oppenheimer's security clearance, in effect barring him from any further work on atomic-related programs. Given his contribution to the Manhattan Project, Oppenheimer felt hurt and betrayed. The nation's scientific community split down the middle on the justice of this decision, and the hard feelings did not fade for a generation. In subsequent years more revelations were unearthed about Soviet spying on the Manhattan Project. Theodore Hall, a brilliant 19-year-old American physicist who arrived at Los Alamos in January 1944, began passing information to the Soviets in late 1944. A socialist and an admirer of the Soviet Union, Hall later wrote that he had decided "an American monopoly" on nuclear weapons "was dangerous and should be prevented." Hall was never prosecuted, although he apparently came under suspicion after World War II ended. In the 1960s he took up residence in the United Kingdom. His role in espionage was first disclosed in 1996. But perhaps the most dramatic disclosure of Soviet spying came in November 2007 when Russian president Vladimir Putin gave Russia's highest award to Americanborn George Koval, a top Soviet spy and member of the Soviet Union's military intelligence. The award was made posthumously following Koval's death in 2006 in Moscow. Koval thus became the only known professional spy to have infiltrated the Manhattan Project. Unlike other Soviet spies, Koval had access not only to Los Alamos but also to the Oak Ridge facility and another top-secret plant near Dayton, Ohio. Putin credited Koval, who had been trained in both electrical and chemical engineering, with having "helped speed up considerably the time it took for the Soviet Union to develop an atomic bomb of its own." C Nuclear Proliferation Once the Manhattan Project demonstrated that an atomic bomb could be built, it was only a matter of time before other nations acquired nuclear weapons. The secrets of the physical world lie open to all trained observers, and any country with the scientific knowledge and a sufficient industrial base can manufacture its own nuclear bombs. The United States and the Soviet Union were the first to develop nuclear weapons, followed by Britain, France, and China. In 1968 the five nuclear powers signed the Nuclear Nonproliferation Treaty, under which they agreed to pursue disarmament and to deny nuclear weapons technology or assistance to any nonnuclear state. By 1995, 165 nonnuclear states had ratified the treaty. India, Israel, and Pakistan did not adopt the treaty, and today those three countries have nuclear weapons. South Africa began to develop nuclear weapons, but scrapped its program and agreed to the treaty in 1991. Following the Persian Gulf War, UN weapons inspectors discovered that Iraq had a nuclear weapons program but had not yet developed a bomb. In 2003 North Korea withdrew from the treaty and announced that it had secretly developed atomic bombs. As a result, by 2003 nine countries--Britain, China, France, India, Israel, North Korea, Pakistan, Russia, and the United States--were known or were believed to possess nuclear weapons. Today the governments of many nations are also concerned about the possibility that nuclear bombs or the fissile material needed to make a Hiroshima-type nuclear bomb could fall into the hands of terrorists. See also Arms Control; Terrorism. D Nuclear Energy for Peaceful Purposes A fourth legacy of the Manhattan Project may be seen in the emergence of peaceful uses of nuclear energy. In 1953 U.S. president Dwight D. Eisenhower told the UN that America would share its atomic expertise with poorer countries in the Plowshare, or Atoms for Peace, program. This short-lived endeavor helped spread peaceful nuclear technology around the world, but it never achieved the hoped-for goal of providing "electricity too cheap to measure." Nevertheless, by 2003 the United States had more than 100 nuclear power plants in operation, and there were 438 commercial nuclear generating units worldwide. Widely publicized nuclear power plant accidents, such as the one at Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, in 1979 and Chernobyl' in Ukraine in 1986, have somewhat dampened the hopes of nuclear energy advocates. The realm of nuclear medicine remains the chief area where scientists' dreams for the peaceful uses of the atom are still alive and well. See also Nuclear Energy. E Storing Nuclear Waste The fifth and last Manhattan Project legacy revolves around the dilemmas of storing nuclear waste and cleaning up polluted nuclear facilities. Plutonium remains radioactive for a long time. It has a half-life of 24,000 years, which means that only half of its radiation will disappear after 24,000 years. Once plutonium is created, it will exist virtually forever. Finding a way to safely store spent fuel rods and other nuclear waste that remains radioactive and therefore biologically harmful continues to tax the nation's best scientific minds. Thus, the echoes of the Manhattan Project are likely to be heard as long as there are people around to hear them. It is quite a legacy. Contributed By: Ferenc Morton Szasz Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.