by Brian Post
The concept of the atom has been an ongoing puzzle of mystery and research for scientists since it was first conceived 2400 years ago in the Golden Age of Greece. Democritus, a Greek philosopher, was the first to formulate the concept of the atom. He named these tiny, indivisible particles "atoms" after the Greek word atomos, meaning indivisible. He believed that rocks differed from trees simply because the size, shape, and weight of their atoms was different. He considered the atom the smallest denominator of the physical universe. Democritus's atom was a heated topic for debate, but not heavily studied until Isaac Newton at the end of the seventeenth century. Newton also determined the atom was the smallest particle, and scientists simply accepted his judgement. In the early 1800's, Michael Faraday indicated that the atom contained particles of electricity, or electrons. This led to a widespread research of the atom's structure, lasting throughout many famous scientists lifetimes. Henri Becquerel in France discovered nuclear energy in 1896. He found, largely by accident, that ores containing uranium emitted a form of radiation that could penetrate several layers of opaque paper and fog a photographic emulsion (York 13). In 1905 Einstein announced his theory of relativity, which is probably still the worlds most famous equation (Szasz 8). This theory would later lead the world to the most devastating weapon history had ever witnessed, the atomic bomb. This bomb would be tested, observed, and debated over until its use was evident and unstoppable. The controversial use of the atomic bomb in World War II was necessary to end the war.
The research efforts towards the bomb were a giant cooperative effort supposedly in competition with Germany. Sparked by refugee physicists in the United States, the atomic research program was slowly organized after German scientists Otto Hahn and Fritz Strassman discovered nuclear fission in 1938, and many United States scientists expressed the fear that Hitler would attempt to build a fission bomb ("Manhattan" 21). The Manhattan Project was the code name for this effort during World War II to produce the atomic bomb. It was named for the Manhattan Engineer District of the US Army Corps of Engineers, because much of the early research was done in New York City. Leo Szilard first conceived the idea of an atomic bomb. He was Jewish, and left Germany for England as soon as Hitler rose to power. It was there that he conceived the idea that it might be possible to achieve a nuclear chain reaction. At the Clarendon Laboratory in 1935, he was involved with the discovery of gamma ray induced emission of neutrons from beryllium. After he came to the United States in 1938, he learned of the discovery of fission, and this news helped him discover some new ideas and insights. He undertook experiments at Columbia University to demonstrate the release of neutrons in the fission process and to measure their number. But he knew that this would not be enough, the scientists needed more financial backing to make better experiments. Szilard instantly recognized that with the discovery of fission, a great new source of energy could be harnessed. One of the most important things that Szilard did to procure research money for the study of fission was to ask Albert Einstein to write a letter to President Roosevelt. In 1939, with Einstein's help, he and Enrico Fermi, along with several other scientists, organized the first controlled self-sustaining chain reaction at the University of Chicago on December 2, 1942 ("Manhattan" 26). This took place in an unused squash court at the University of Chicago. A nuclear fission chain reaction was critical to creating an atomic bomb, and Fermi and Szilard had successfully done it. Now that nuclear fission was a reality, plans needed to be made for a more secure and isolated testing environment. General Leslie Groves, the head of the project, and other scientists gathered to determine a site. Eventually they decided on New Mexico as the state, and Los Alamos as the site. At Los Alamos, they found the Los Alamos Ranch School, a residential boys' school that emphasized outdoor education for children of parents who could afford to give them the experience. Groves, who liked Los Alamos immediately, saw that access to the mesa could easily be controlled by shutting off the main entry road, and the road could be widened to accommodate trucks and heavy machinery. Canyons surrounding the site could be used for explosives tests. As Dudley warned, the water supply was marginal, but Groves thought it might do for the 450 scientists and technicians he believed would be needed. At dinner in Santa Fe that evening, he decided to acquire the site. The scientists and Groves returned to Berkeley to begin the job of planning the laboratory and recruiting a staff. Los Alamos, previously a school for boys, would now become an arsenal of democracy. It is probably safe to say that never before in the history of the human race had so many brilliant minds been gathered together at one place (Szasz 18).
The need to develop the bomb led scientists to incredible manufacturing feats. In theory, an explosion weapon would definitely work, even without testing. An implosion weapon, on the other hand, would need to be tested and could have much more devastating results. Although the assembly of the nuclear materials, whether uranium-235 or plutonium, into a critical mass seemed most feasible by firing one fraction of it into another, Seth Neddermeyer, who had transferred to Los Alamos from the National Bureau of Standards, heard of implosion in indoctrination lectures, and suggested that it might produce higher velocities than were available in the gun method. Without any particular official recognition from the laboratory he set up to do the early work on his own. He went to Bruceton, Pa., where the Bureau of Mines had an explosives research station, to learn something about explosions. The first cylindrical implosions were done at Bruceton. That was the birth of the experimental work on implosion, long before experimental work on the gun method. British scientists, who began arriving at Los Alamos in December, 1943, made substantial contributions to the implosion work ("Manhattan" 29). Sufficiently pure quantities of uranium and plutonium were needed for experimentation. General Leslie Groves immediately purchased a site at Oak Ridge, Tenn., for facilities to separate the necessary uranium-235 from the much more common uranium-238. He also appointed theoretical physicist J. Robert Oppenheimer as director of the weapons laboratory, built on an isolated mesa (flat land area) at Los Alamos, New Mexico. After much difficulty an absorbent barrier suitable for separating isotopes of uranium was developed and installed in the Oak Ridge gaseous diffusion plant. Finally, in 1945, uranium-235 of bomb purity was shipped to Los Alamos, where it was fashioned into a gun-type weapon. In a barrel, one piece of uranium was fired at another, together forming a supercritical, explosive mass. This made it necessary to assemble the material very rapidly by firing it together with a gun that produced muzzle velocities exceeding 3,000 feet a second, and to provide a source of neutrons to initiate the chain reaction at the precise moment when the material was assembled. Another type of atomic bomb was also constructed using the synthetic element plutonium. At Los Alamos the plutonium was surrounded with high explosives to compress it into a super dense, super critical mass far faster than could be done in a gun barrel. After the discovery of plutonium, the use of guns became more problematic. Light element impurities could cause predetonation if sufficient assembly velocity was not achieved. Despite this concern, the elegant simplicity of gun technology gave Oppenheimer cause for optimism as Los Alamos came into existence. And despite the simplicity of gun assembly, a great deal of uncertainty remained about the nuclear materials and what the final product would look like. Because of such uncertainty, Oppenheimer took personal control of gun development. With two types of fissile material to use, Oppenheimer faced a crucial first decision. Should the Laboratory develop a gun capable of using plutonium, the more difficult material to use, and adjust the gun to use uranium? Or, should two different guns be developed simultaneously? Oppenheimer chose to develop the plutonium gun, code named "Thin Man" and then make the necessary changes to accommodate uranium. He believed that uranium presented few metallurgical problems and any changes in the gun would be minor. Work on Thin Man continued until July 1944 when Emilo Segro's experiments on the spontaneous fissioning of plutonium proved that a gun could not be used to assemble this material. Oppenheimer made the decision to abandon Thin Man and redirect much of the Laboratory's resources to develop the implosion method. After the reorganization, gun work focused on uranium assembly, code named "Little Boy." Oppenheimer's earlier decision in 1943 to concentrate on Thin Man on the belief that a uranium gun did not present major technical problems proved prophetic. Little Boy was developed with few major complications. As the staff at Los Alamos began research in the spring of 1943, the most formidable problems it confronted were related to the new materials that would be used in atomic bombs. These materials, uranium-235 and plutonium, were largely unknown. Uranium-235 formed only a tiny fraction of natural uranium (less than 1 percent) and plutonium had been discovered only two years earlier at the University of California, Berkeley, Radiation Laboratory by chemistry professor Glenn Seaborg and his associates. As June 1943 ended, the future of Los Alamos' program for a plutonium bomb seemed in doubt. Only time would tell if plutonium could be used in nuclear weapons, and if it could be used, how. The resolution of those questions was to have a pervasive effect on the new Laboratory and the world. In the late summer of 1943, experimental work at Los Alamos was focused on the designs for two gun-type atomic weapons. One would fire a uranium "bullet" into a uranium "target," while the other would use plutonium bullets and targets and, to overcome problems that might be caused by impurities in plutonium, would fire the bullet at a higher velocity. Even if the appropriate explosive lenses could be produced, they would have to be set off simultaneously to create a symmetrical implosion. It was not clear, however, that the much more complicated implosion device would work. Before it could be used in combat, a test would be required. The first implosion calculation showed that the fissile material would be strongly compressed and that a high yield would result from assembling a relatively small amount of fissile material if a spherically symmetrical implosion was produced.
The bomb, throughout time, was created and successfully tested, leading the United States to the end of the war by bombing Japan. The Los Alamos Laboratory was organized in 1943 to design a nuclear weapon that the Army hoped would win World War II. The laboratory, which was the largest and most remarkable of all the atomic research centers, in only two years succeeded in developing, designing, and building two different kinds of fission weapons, an explosion and an implosion bomb (York 16). Because of the uncertainties attending almost every phase of the implosion weapon, it was decided almost at the beginning of the effort that the implosion bomb would have to be tested. After various test sites were considered, a location in the Jornado del Muerto desert in central New Mexico was selected. Harvard physicist Kenneth Bainbridge planned and University of Minnesota physicist John Williams supervised the construction of the facilities to support a test there. Los Alamos Director J. Robert Oppenheimer named the site "Trinity" after a poem by John Donne that he had been reading. The construction of the Trinity site was rapidly accomplished in the winter and spring of 1945, and by June, Bainbridge was ready to calibrate the instruments that would be used to measure the blast, heat and radiation of the "gadget" using a 100-ton stack of high explosives tagged with fission products from the Hanford pile. The 100-ton test was the largest man-made explosion up to that time and made it possible for the Los Alamos scientists to refine their instruments before the much larger blast anticipated from the gadget. The design of the gadget had been fixed in February 1945 when Groves ordered a design freeze so that the device could be ready by July. A conservative solid-core design by Robert Christy, a member of the Theoretical Physics (T) Division, the gadget required the development of detonators, fuses and high-explosive lenses that were not yet perfected. Given a clear goal, however, Los Alamos scientists and technicians succeeded in producing all of the components of the device successfully by July 13. On that day, assembly of the gadget began at Trinity. A crew led by Norris Bradbury, a professor of physics at Stanford University who had come to Los Alamos by way of the Naval Reserve and Dahlgren Proving Grounds, assembled the high-explosive lenses that had been brought from V-site at Los Alamos the day before escorted by Harvard professor George Kistiakowsky, who had led the high-explosives effort at the Laboratory since November 1943. Bradbury, Kistiakowsky and five engineers began their work at 1 p.m. After the tamper and the active material were inserted into the spherical case, the final high-explosives were inserted. Saturday, July 14, 1945, the assembled gadget was hoisted to the top of the 100-foot tower on which it would be detonated. The firing unit was wired by late afternoon. Bradbury's schedule for Sunday, July 15, called for the staff to "look for rabbit's feet and four-leaved clovers." The detonation was scheduled for 4 a.m., Monday, July 16. As the test approached, the weather worsened, as the meteorologist assigned to predict it had warned. A thunderstorm broke over the site late on July 15, and the test was postponed from 4 a.m. to 5:30 a.m. to avoid the possibility of a rain-out of fission products from the bomb cloud. In nearby settlements, members of the health physics team were ready to evacuate the population should the test greatly exceed expected yields. Although most scientists believed that the yields would be low, Edward Teller, group leader of the Super and General Theory Group Division, bet that it might exceed 40 kilotons, and Enrico Fermi, head of F Division, was heard taking side-bets that the bomb would incinerate New Mexico. Groves called the governor of New Mexico to alert him that an evacuation of the state might be required. Oppenheimer was in a state of high tension during the early morning hours, but, as predicted, the weather cleared and the countdown for the test was begun at 5:10 a.m. At the control point, Joe McKibben, who had been with the project since the beginning, threw the switch that started the precise automatic timer at minus 45 seconds. Only Donald Hornig, a physical chemist from Harvard University, on the arming party, could stop the explosion. At 5:29:45 a.m., the gadget exploded with a force of 21,000 tons of TNT, evaporating the tower on which it stood. Los Alamos had succeeded in producing a nuclear weapon only two years, three months and 16 days after it was formally opened. Now came the decision of where to drop the bomb. A special air force team, already completing it's training on Tinian in the Mariana Islands, was alerted to prepare for action in early august ("Manhattan" 29). By May 1945, five cities had emerged as leading candidates. Nigata recieved a "b" ranking. Yokohama, a seaport and industrial center, and the Kokura Arsenal recieved "a" rankings. The top "aa" rankings went to Hiroshima, with its army depot and port, and to the ancient religious capitol of Kyoto ("Planning" 91). Kyoto, however, was far too historically valuable to be bombed. Hiroshima and Nagasaki were chosen due to their importance to the Japanese military effort. Hiroshima was to be the first target, and Nagasaki would be bombed two days later. If the United States dropped a single atomic bomb on Japan, the japanese might think it a trial weapon, and the only one, and not expect a rain of similar bombs to follow (Lamont 68). The first bomb was a Uranium bomb that weighed in at over 4 & 1/2 tons nicknamed "Little Boy." This bomb was dropped on Hiroshima August 6th, 1945. The Aioi Bridge, one of 81 bridges connecting the seven-branched delta of the Ota River, was the aiming point of the bomb. 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 the flash of an instant, 66,000 people were killed and 69,000 people were injured by a 10 kiloton atomic explosion. The point of total vaporization from the blast measured one half of a mile in diameter. Total destruction ranged at one mile in diameter. Severe blast damage carried as far as two miles in diameter. At two and a half miles, everything flammable in the area 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 9th 1945, Nagasaki fell to the same treatment as Hiroshima. This time, a Plutonium bomb nicknamed "Fat Man" was dropped on the city. Even though the "Fat Man" missed by over a mile and a half, it still leveled nearly half the city. Nagasaki's population dropped in one split-second from 422,000 to 383,000. 39,000 were killed, over 25,000 were injured. That blast was less than 10 kilotons as well. Estimates from physicists who have studied each atomic explosion state that the bombs that were used had utilized only 1/10th of 1 percent of their respective explosive capabilities. While the mere explosion from an atomic bomb is deadly enough, its destructive ability doesn't stop there. Atomic fallout creates another hazard as well. The rain that follows any atomic detonation is laden with radioactive particles. Many survivors of the Hiroshima and Nagasaki blasts succumbed to radiation poisoning due to this occurrence. The atomic 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.
The atomic bombs, although devastatingly gruesome in their efficiency, were necessary to end the war and prevent fewer casualties on any side. The sheer power and destruction of the bombs shocked all other countries and terminated any continuance of the war. Japan suffered greatly, but their suffering was small compared to the lives that would have been lost if the war continued. Throughout the entire Manhattan Project scientists strived to complete the bomb as quickly as possible, knowing that it was the only way to end the war. The power of the atom, harnessed by the United States military and the scientists at Los Alamos, brought a quick and necessary end to one of the most horrible wars history had ever witnessed.
Works Cited