Emilio Gino Segrè was an Italian-American physicist and Nobel laureate, who discovered the elements technetium and astatine, the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959. From 1943 to 1946 he worked at the Los Alamos National Laboratory as a group leader for the Manhattan Project, he found in April 1944 that Thin Man, the proposed plutonium gun-type nuclear weapon, would not work because of the presence of plutonium-240 impurities. Born in Tivoli, near Rome, Segrè studied engineering at the University of Rome La Sapienza before taking up physics in 1927. Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of the Via Panisperna boys. From 1936 to 1938 he was director of the Physics Laboratory at the University of Palermo. After a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, he was sent a molybdenum strip from the laboratory's cyclotron deflector in 1937, emitting anomalous forms of radioactivity.
After careful chemical and theoretical analysis, Segrè was able to prove that some of the radiation was being produced by a unknown element, named technetium, the first artificially synthesized chemical element that does not occur in nature. In 1938, Benito Mussolini's fascist government passed anti-Semitic laws barring Jews from university positions; as a Jew, Segrè was now rendered an indefinite émigré. At the Berkeley Radiation Lab, Lawrence offered him a job as a research assistant. While at Berkeley, Segrè helped discover the element astatine and the isotope plutonium-239, used to make the Fat Man nuclear bomb dropped on Nagasaki. In 1944, he became a naturalized citizen of the United States. On his return to Berkeley in 1946, he became a professor of physics and of history of science, serving until 1972. Segrè and Owen Chamberlain were co-heads of a research group at the Lawrence Radiation Laboratory that discovered the antiproton, for which the two shared the 1959 Nobel Prize in Physics.
Segrè was active as a photographer and took many photos documenting events and people in the history of modern science, which were donated to the American Institute of Physics after his death. The American Institute of Physics named its photographic archive of physics history in his honor. Emilio Gino Segrè was born into a Sephardic Jewish family in Tivoli, near Rome, on 1 February 1905, the son of Giuseppe Segrè, a businessman who owned a paper mill, Amelia Susanna Treves, he had two older brothers and Marco. His uncle, Gino Segrè, was a law professor, he was educated at the ginnasio in Tivoli and, after the family moved to Rome in 1917, the ginnasio and liceo in Rome. He graduated in July 1922 and enrolled in the University of Rome La Sapienza as an engineering student. In 1927, Segrè met Franco Rasetti; the two young physics professors were looking for talented students. They attended the Volta Conference at Como in September 1927, where Segrè heard lectures from notable physicists including Niels Bohr, Werner Heisenberg, Robert Millikan, Wolfgang Pauli, Max Planck and Ernest Rutherford.
Segrè joined Fermi and Rasetti at their laboratory in Rome. With the help of the director of the Institute of Physics, Orso Mario Corbino, Segrè was able to transfer to physics, studying under Fermi, earned his laurea degree in July 1928, with a thesis on "Anomalous Dispersion and Magnetic Rotation". After a stint in the Italian Army from 1928 to 1929, during which he was a commissioned as a second lieutenant in the antiaircraft artillery, Segrè returned to the laboratory on Via Panisperna, he published his first article, which summarised his thesis, "On anomalous dispersion in mercury and in lithium", jointly with Edoardo Amaldi in 1928, another article with him the following year on the Raman effect. In 1930, Segrè began studying the Zeeman effect in certain alkaline metals; when his progress stalled because the diffraction grating he required to continue was not available in Italy, he wrote to four laboratories elsewhere in Europe asking for assistance and received an invitation from Pieter Zeeman to finish his work at Zeeman's laboratory in Amsterdam.
Segrè was awarded a Rockefeller Foundation fellowship and, on Fermi's advice, elected to use it to study under Otto Stern in Hamburg. Working with Otto Frisch on space quantization produced results that did not agree with the current theory. Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of the Via Panisperna boys. In 1934, he met Elfriede Spiro, a Jewish woman whose family had come from Ostrowo in West Prussia, but had fled to Breslau when that part of Prussia became part of Poland after World War I. After the Nazi Party came to power in Germany in 1933, she had emigrated to Italy, where she worked as a secretary and an interpreter. At first she did not speak Italian well, Segrè and Spiro conversed in German, in which he was fluent; the two were married at the Great Synagogue of Rome on 2 February 1936. He agreed with the rabbi to spend the minimal amount on the wedding, giving the balance of what would be spent on a luxury wedding to Jewish refugees from Germany.
The rabbi managed to give them many of the trappings of a luxury wedding anyway. The couple had three children: Claudio, born in 1937, Amelia Gertrude Allegra, born in 1937, Fausta Irene, born in 1945. After marrying, Segrè sought a stable job and became professor of physics and director of the Physics Institute at the University of Palermo, he found the equipment there primitive and the library bereft o
A thesis or dissertation is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings. In some contexts, the word "thesis" or a cognate is used for part of a bachelor's or master's course, while "dissertation" is applied to a doctorate, while in other contexts, the reverse is true; the term graduate thesis is sometimes used to refer to both master's theses and doctoral dissertations. The required complexity or quality of research of a thesis or dissertation can vary by country, university, or program, the required minimum study period may thus vary in duration; the word "dissertation" can at times be used to describe a treatise without relation to obtaining an academic degree. The term "thesis" is used to refer to the general claim of an essay or similar work; the term "thesis" comes from the Greek θέσις, meaning "something put forth", refers to an intellectual proposition. "Dissertation" comes from the Latin dissertātiō, meaning "discussion".
Aristotle was the first philosopher to define the term thesis. "A'thesis' is a supposition of some eminent philosopher that conflicts with the general opinion...for to take notice when any ordinary person expresses views contrary to men's usual opinions would be silly". For Aristotle, a thesis would therefore be a supposition, stated in contradiction with general opinion or express disagreement with other philosophers. A supposition is a statement or opinion that may or may not be true depending on the evidence and/or proof, offered; the purpose of the dissertation is thus to outline the proofs of why the author disagrees with other philosophers or the general opinion. A thesis may be arranged as a thesis by publication or a monograph, with or without appended papers though many graduate programs allow candidates to submit a curated collection of published papers. An ordinary monograph has a title page, an abstract, a table of contents, comprising the various chapters, a bibliography or a references section.
They differ in their structure in accordance with the many different areas of study and the differences between them. In a thesis by publication, the chapters constitute an introductory and comprehensive review of the appended published and unpublished article documents. Dissertations report on a research project or study, or an extended analysis of a topic; the structure of a thesis or dissertation explains the purpose, the previous research literature impinging on the topic of the study, the methods used, the findings of the project. Most world universities use a multiple chapter format: a) an introduction, which introduces the research topic, the methodology, as well as its scope and significance. Degree-awarding institutions define their own house style that candidates have to follow when preparing a thesis document. In addition to institution-specific house styles, there exist a number of field-specific and international standards and recommendations for the presentation of theses, for instance ISO 7144.
Other applicable international standards include ISO 2145 on section numbers, ISO 690 on bibliographic references, ISO 31 on quantities or units. Some older house styles specify that front matter must use a separate page number sequence from the main text, using Roman numerals; the relevant international standard and many newer style guides recognize that this book design practice can cause confusion where electronic document viewers number all pages of a document continuously from the first page, independent of any printed page numbers. They, avoid the traditional separate number sequence for front matter and require a single sequence of Arabic numerals starting with 1 for the first printed page. Presentation requirements, including pagination, layout and color of paper, use of acid-free paper, paper size, order of components, citation style, will be checked page by page by the accepting officer before the thesis is accepted and a receipt is issued. However, strict standards are not always required.
Most Italian universities, for example, have only general requirements on the character size and the page formatting, leave much freedom for the actual typographic details. A thesis or dissertation committee is a committee. In the US, these committees consist of a primary supervisor or advisor and two or more committee members, who supervise the progress of the dissertation and may act as the examining committee, or jury, at the oral examination of the thesis. At most universities, the committee is chosen by the student in conjunction with his or her primary adviser after completion of the comprehensive examinations or prospectus meeting, may consist of members of the comps committee; the committee members are doctors in their field (whether a PhD or other des
Princeton, New Jersey
Princeton is a municipality with a borough form of government in Mercer County, New Jersey, United States, established in its current form on January 1, 2013, through the consolidation of the Borough of Princeton and Princeton Township. As of the 2010 United States Census, the municipality's population was 28,572, reflecting the former township's population of 16,265, along with the 12,307 in the former borough. Princeton was founded before the American Revolution, it is the home of Princeton University, which bears its name and moved to the community in 1756 from its previous location in Newark. Although its association with the university is what makes Princeton a college town, other important institutions in the area include the Institute for Advanced Study, Westminster Choir College, Princeton Plasma Physics Laboratory, Princeton Theological Seminary, Opinion Research Corporation, Bristol-Myers Squibb, Siemens Corporate Research, SRI International, FMC Corporation, The Robert Wood Johnson Foundation, Amrep and Dwight, Berlitz International, Dow Jones & Company.
Princeton is equidistant from New York City and Philadelphia. It is close to many major highways that serve both cities, receives major television and radio broadcasts from each, it is close to Trenton, New Jersey's capital city, Edison. The New Jersey governor's official residence has been in Princeton since 1945, when Morven in what was Princeton Borough became the first Governor's mansion, it was replaced by the larger Drumthwacket, a colonial mansion located in the former Township. Morven became a museum property of the New Jersey Historical Society. Princeton was ranked 15th of the top 100 towns in the United States to Live and Work In by Money Magazine in 2005. Throughout much of its history, the community was composed of two separate municipalities: a township and a borough; the central borough was surrounded by the township. The borough seceded from the township in 1894 in a dispute over school taxes. Princeton Borough contained Nassau Street, the main commercial street, most of the University campus, incorporated most of the urban area until the postwar suburbanization.
The borough and township had equal populations. The Lenni Lenape Native Americans were the earliest identifiable inhabitants of the Princeton area. Europeans founded their settlement in the late part of the 17th century; the first European to find his home in the boundaries of the future town was Henry Greenland. He built his house in 1683 along with a tavern. In this drinking hole representatives of West Jersey and East Jersey met to set boundaries for the location of the township. Princeton was known only as part of nearby Stony Brook. Nathaniel Fitz Randolph, a native of the town, attested in his private journal on December 28, 1758, that Princeton was named in 1724 upon the making/construction of the first house in the area by James Leonard, who first referred to the town as Princetown when describing the location of his large estate in his diary; the town bore a variety of names subsequently, including: Princetown, Prince's Town and Princeton. Although there is no official documentary backing, the town is considered to be named after King William III, Prince William of Orange of the House of Nassau.
Another theory suggests that the name came from a large land-owner named Henry Prince, but no evidence backs this contention. A royal prince seems a more eponym for the settlement, as three nearby towns had similar names: Kingston and Princessville; when Richard Stockton, one of the founders of the township, died in 1709 he left his estate to his sons, who helped to expand property and the population. Based on the 1880 United States Census, the population of the town comprised 3,209 persons. Local population has expanded from the nineteenth century. According to the 2010 Census, Princeton Borough had 12,307 inhabitants, while Princeton Township had 16,265; the numbers have become stagnant. Aside from housing the university of the same name, the settlement suffered the revolutionary Battle of Princeton in 1777, when George Washington forced the British to evacuate southern New Jersey. After the victory, the town hosted the first Legislature under the State Constitution to decide the State's seal and organization of its government.
In addition, two of the original signers of the Declaration of Independence—Richard Stockton and John Witherspoon lived in Princeton. Princetonians honored their citizens' legacy by naming two streets in the downtown area after them. On January 10, 1938 Henry Ewing Hale called for a group of citizens to discuss opening a "Historical Society of Princeton." The Bainbridge House would be dedicated for this purpose. The house was used once for a meeting of Continental Congress in 1783, a general office, as the Princeton Public Library; the House is owned by Princeton University and is leased to the Princeton Historical Society for one dollar per year. The house has kept its original staircase and paneled walls. Around 70% of the house has been unaltered. Aside from safety features such as wheelchair access and electrical work, the house was has been restored to its original look. During the most stirring events in its history, Princeton was a wide spot in the ro
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or from a combination of fission and fusion reactions. Both bomb types release large quantities of energy from small amounts of matter; the first test of a fission bomb released an amount of energy equal to 20,000 tons of TNT. The first thermonuclear bomb test released energy equal to 10 million tons of TNT. A thermonuclear weapon weighing little more than 2,400 pounds can release energy equal to more than 1.2 million tons of TNT. A nuclear device no larger than traditional bombs can devastate an entire city by blast and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been used twice in war, both times by the United States against Japan near the end of World War II. On August 6, 1945, the U. S. Army Air Forces detonated a uranium gun-type fission bomb nicknamed "Little Boy" over the Japanese city of Hiroshima.
S. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed "Fat Man" over the Japanese city of Nagasaki; these bombings caused injuries that resulted in the deaths of 200,000 civilians and military personnel. The ethics of these bombings and their role in Japan's surrender are subjects of debate. Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations are suspected of seeking them; the only countries known to have detonated nuclear weapons—and acknowledge possessing them—are the United States, the Soviet Union, the United Kingdom, China, India and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Turkey and the Netherlands are nuclear weapons sharing states. South Africa is the only country to have independently developed and renounced and dismantled its nuclear weapons.
The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned, political tensions remained high in the 1970s and 1980s. Modernisation of weapons continues to this day. There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is from fission reactions are referred to as atomic bombs or atom bombs; this has long been noted as something of a misnomer, as their energy comes from the nucleus of the atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material is forced into supercriticality—allowing an exponential growth of nuclear chain reactions—either by shooting one piece of sub-critical material into another or by compression of a sub-critical sphere or cylinder of fissile material using chemically-fueled explosive lenses.
The latter approach, the "implosion" method, is more sophisticated than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself; the amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons of TNT. All fission reactions generate the remains of the split atomic nuclei. Many fission products are either radioactive or moderately radioactive, as such, they are a serious form of radioactive contamination. Fission products are the principal radioactive component of nuclear fallout. Another source of radioactivity is the burst of free neutrons produced by the weapon; when they collide with other nuclei in surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239.
Less used has been uranium-233. Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it is not clear that this has been implemented, their plausible use in nuclear weapons is a matter of dispute; the other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are referred to as thermonuclear weapons or more colloquially as hydrogen bombs, as they rely on fusion reactions between isotopes of hydrogen. All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, fusion reactions can themselves trigger additional fission reactions. Only six countries—United States, United Kingdom, China and India—have conducted thermonuclear weapon tests. North Korea claims to have tested a fusion weapon as of January 2016. Thermonuclear weapons a
Wendover Air Force Base
Wendover Air Force Base is a former United States Air Force base in Utah now known as Wendover Airport. During World War II, it was a training base for B-24 bomber crews, it was the training site of the 509th Composite Group, the B-29 unit that carried out the atomic bombings of Hiroshima and Nagasaki. After the war, Wendover was used for gunnery range and as a research facility, it was closed by the Air Force in 1969, the base was given to Wendover City in 1977. Tooele County, assumed ownership of the airport and base buildings in 1998, the County continues to operate the airfield as a public airport. A portion of the original bombing range is now the Utah Test and Training Range, used extensively by the Air Force with live fire targets on the range. Wendover Air Force Base's history began in 1940, when the United States Army began looking for additional bombing ranges; the area near the town of Wendover was well-suited to these needs. Though isolated, the area was served by the Western Pacific Railroad, many of its citizens were employed by the railroad.
Construction of the base began on 20 September 1940 and on the range on 4 November 1940. Wendover Air Base became a subpost of Fort Douglas in Salt Lake City on 29 July 1941. By that time a total of 1,822,000 acres had been acquired for the base and associated gunnery/bombing range 86 miles long and 18 to 36 miles wide. Ranchers protested the loss of their grazing land, which they claimed would wipe them out and cost the state of Utah $1.5 million annually. They took their complaints to Governor Henry Hooper Blood, but the War Department pressed on with the development of the bombing range; the first military contingent arrived on 12 August 1941. To provide water, a pipeline was run from a spring on Pilot Peak to the base. With the entrance of the United States into World War II, Wendover Field took on greater importance, it was gunnery range. On March 1942 the Army Air Force activated Wendover Army Air Field and assigned the research and development of guided missiles, pilotless aircraft, remotely controlled bombs to the site.
The new base was serviced by the Ogden Air Depot at Hill Field. In April 1942, the Wendover Sub-Depot was activated and assumed technical and administrative control of the field, under the Ogden Air Depot; the Wendover Sub-Depot was tasked to requisition and issue all Army Air Forces property for organizations stationed at Wendover Field for training. By late 1943 there were 17,500 military personnel at Wendover. Construction at the base continued for most of the war, including three 8,100-foot paved runways, taxiways, a 300,000-square-foot ramp, seven hangars. By May 1945 the base consisted of 668 buildings, including a 300-bed hospital, swimming pool, chapel, bowling alley, two movie theatres, 361 housing units for married officers and civilians. Wendover's mission was to train heavy bomb groups; the training of Boeing B-17 Flying Fortress and Consolidated B-24 Liberator groups began in April 1942, with the arrival of the 306th Bomb Group flying B-17s. From March 1942 through April 1944, Wendover AAF hosted twenty newly formed B-17 and B-24 groups during one phase of their group training.
The Second Air Force organized bombardment training into three phases. In the first, training focused on the individual crew members. In the second, training involved the whole crew; the third and final phase saw the group's crews training together, with formation flying and practice combat missions. Until the end of 1943, each phase of training was conducted at a different base. Heavy Bomb Groups Trained at Wendover Army Air Base In April 1944, the role of Wendover Army Air Base changed with the arrival from Louisiana of P-47 fighters of the 72nd Fighter Wing; the program ended in September. In June 1943, preparations began for the operational use of atomic bombs. Although not as suitable for the atomic mission as the British Avro Lancaster with its cavernous 33-foot bomb bay, Major General Leslie R. Groves, Jr. the director of the Manhattan Project, General Henry H. Arnold, the Chief of United States Army Air Forces, wanted to use an American plane, if this was at all possible, so the Boeing B-29 Superfortress was chosen though it required substantial modification.
The modification project was codenamed Silverplate, but this codename came to identify the training and operational aspects of the program as well. Arnold selected Lieutenant Colonel Paul Tibbets, an officer with a distinguished combat record in Europe and North Africa, who had expert knowledge of the B-29 as one of its test pilots, to form and train a group to deliver atomic bombs. Tibbets chose the Wendover over Great Bend and Mountain Home, Idaho, as the location for his training program, it was remote, good for secrecy and security, but within reasonable distance by air from the Manhattan Project's Site Y, at Los Alamos, New Mexico, the Salton Sea Naval Auxiliary Air Station, where bombing tables for the mission would be prepared. The base was given the code name "Kingman", became the Manhattan Project's Site K; the activity to assemble and flight test prototype bombs was named "Project W-47". On 14 September 1944, the 393d Bomb Squadron arrived at Wendover from its former base at Fairmont Army Air Base
John Archibald Wheeler
John Archibald Wheeler was an American theoretical physicist. He was responsible for reviving interest in general relativity in the United States after World War II. Wheeler worked with Niels Bohr in explaining the basic principles behind nuclear fission. Together with Gregory Breit, Wheeler developed the concept of the Breit–Wheeler process, he is best known for linking the term "black hole" to objects with gravitational collapse predicted early in the 20th century, for coining the terms "quantum foam", "neutron moderator", "wormhole" and "it from bit", for hypothesizing the "one-electron universe". Wheeler earned his doctorate at Johns Hopkins University under the supervision of Karl Herzfeld, studied under Breit and Bohr on a National Research Council fellowship. In 1939 he teamed up with Bohr to write a series of papers using the liquid drop model to explain the mechanism of fission. During World War II, he worked with the Manhattan Project's Metallurgical Laboratory in Chicago, where he helped design nuclear reactors, at the Hanford Site in Richland, where he helped DuPont build them.
He returned to Princeton after the war ended, but returned to government service to help design and build the hydrogen bomb in the early 1950s. For most of his career, Wheeler was a professor at Princeton University, which he joined in 1938, remaining until his retirement in 1976. At Princeton he supervised 46 PhDs, more than any other professor in the Princeton physics department. Wheeler was born in Jacksonville, Florida on July 9, 1911 to librarians Joseph Lewis Wheeler and Mabel Archibald Wheeler, he was the oldest of four children, having two younger brothers and Robert, a younger sister, Mary. Joseph earned a Ph. D. from Brown University and a Master of Library Science from Columbia University. Robert earned a Ph. D. in geology from Harvard University and worked as a geologist for oil companies and at colleges. Mary became a librarian, they grew up in Youngstown, but spent a year in 1921 to 1922 on a farm in Benson, where Wheeler attended a one-room school. After they returned to Youngstown he attended Rayen High School.
After graduating from the Baltimore City College high school in 1926, Wheeler entered Johns Hopkins University with a scholarship from the state of Maryland. He published his first scientific paper in 1930, as part of a summer job at the National Bureau of Standards, he earned his doctorate in 1933. His dissertation research work, carried out under the supervision of Karl Herzfeld, was on the "Theory of the Dispersion and Absorption of Helium", he received a National Research Council fellowship, which he used to study under Gregory Breit at New York University in 1933 and 1934, in Copenhagen under Niels Bohr in 1934 and 1935. In a 1934 paper and Wheeler introduced the Breit–Wheeler process, a mechanism by which photons can be transformed into matter in the form of electron-positron pairs; the University of North Carolina at Chapel Hill made Wheeler an associate professor in 1937, but he wanted to be able work more with the experts in particle physics. He turned down an offer in 1938 of an associate professorship at Johns Hopkins University in favor of an assistant professorship at Princeton University.
Although it was a lesser position, he felt that Princeton, building up its physics department, was a better career choice. He remained a member of the faculty there until 1976. In a 1937 paper "On the Mathematical Description of Light Nuclei by the Method of Resonating Group Structure", Wheeler introduced the S-matrix – short for scattering matrix – "a unitary matrix of coefficients connecting the asymptotic behavior of an arbitrary particular solution with that of solutions of a standard form." Werner Heisenberg subsequently developed the idea of the S-matrix in the 1940s. Due to the problematic divergences present in quantum field theory at that time, Heisenberg was motivated to isolate the essential features of the theory that would not be affected by future changes as the theory developed. In doing so he was led to introduce a unitary "characteristic" S-matrix, which became an important tool in particle physics. Wheeler did not develop the S-matrix, but joined Edward Teller in examining Bohr's liquid drop model of the atomic nucleus.
They presented their results at a meeting of the American Physical Society in New York in 1938. Wheeler's Chapel Hill graduate student Katharine Way presented a paper, which she followed up in a subsequent article, detailing how the liquid drop model was unstable under certain conditions. Due to a limitation of the liquid drop model, they all missed the opportunity to predict nuclear fission; the news of Lise Meitner and Otto Frisch's discovery of fission was brought to America by Bohr in 1939. Bohr told Leon Rosenfeld. Bohr and Wheeler set to work applying the liquid drop model to explain the mechanism of nuclear fission; as the experimental physicists studied fission, they uncovered puzzling results. George Placzek asked Bohr why uranium seemed to fission with both fast and slow neutrons. Walking to a meeting with Wheeler, Bohr had an insight that the fission at low energies was due to the uranium-235 isotope, while at high energies it was due to the far more abundant uranium-238 isotope, they co-wrote two more papers on fission.
Their first paper appeared in Physical Review on September 1, 1939, the day Germany invaded Poland, starting World War II in Europe. Considering the notion that positrons were electrons that were traveling backwards in time, he came up in 1940 with his one-electron universe postulate: that there was in fact only one electron, bouncing back a
New Mexico is a state in the Southwestern region of the United States of America. It is one of the Mountain States and shares the Four Corners region with Utah and Arizona. With a population around two million, New Mexico is the 36th state by population. With a total area of 121,592 sq mi, it is the fifth-largest and sixth-least densely populated of the 50 states. Due to their geographic locations and eastern New Mexico exhibit a colder, alpine climate, while western and southern New Mexico exhibit a warmer, arid climate; the economy of New Mexico is dependent on oil drilling, mineral extraction, dryland farming, cattle ranching, lumber milling, retail trade. As of 2016–2017, its total gross domestic product was $95 billion with a GDP per capita of $45,465. New Mexico's status as a tax haven yields low to moderate personal income taxes on residents and military personnel, gives tax credits and exemptions to favorable industries; because of this, its film industry contributed $1.23 billion to its overall economy.
Due to its large area and economic climate, New Mexico has a large U. S. military presence marked notably with the White Sands Missile Range. Various U. S. national security agencies base their research and testing arms in New Mexico such as the Sandia and Los Alamos National Laboratories. During the 1940s, Project Y of the Manhattan Project developed and built the country's first atomic bomb and nuclear test, Trinity. Inhabited by Native Americans for many thousands of years before European exploration, it was colonized by the Spanish in 1598 as part of the Imperial Spanish viceroyalty of New Spain. In 1563, it was named Nuevo México after the Aztec Valley of Mexico by Spanish settlers, more than 250 years before the establishment and naming of the present-day country of Mexico. After Mexican independence in 1824, New Mexico became a Mexican territory with considerable autonomy; this autonomy was threatened, however, by the centralizing tendencies of the Mexican government from the 1830s onward, with rising tensions leading to the Revolt of 1837.
At the same time, the region became more economically dependent on the United States. At the conclusion of the Mexican–American War in 1848, the United States annexed New Mexico as the U. S. New Mexico Territory, it was admitted to the Union as the 47th state on January 6, 1912. Its history has given New Mexico the highest percentage of Hispanic and Latino Americans, the second-highest percentage of Native Americans as a population proportion. New Mexico is home to part of the Navajo Nation, 19 federally recognized Pueblo communities of Puebloan peoples, three different federally recognized Apache tribes. In prehistoric times, the area was home to Ancestral Puebloans and the modern extant Comanche and Utes inhabited the state; the largest Hispanic and Latino groups represented include the Hispanos of New Mexico and Mexican Americans. The flag of New Mexico features the state's Spanish origins with the same scarlet and gold coloration as Spain's Cross of Burgundy, along with the ancient sun symbol of the Zia, a Puebloan tribe.
These indigenous, Mexican and American frontier roots are reflected in the eponymous New Mexican cuisine and the New Mexico music genre. New Mexico received its name long before the present-day nation of Mexico won independence from Spain and adopted that name in 1821. Though the name “Mexico” itself derives from Nahuatl, in that language it referred to the heartland of the Empire of the Mexicas in the Valley of Mexico far from the area of New Mexico, Spanish explorers used the term “Mexico” to name the region of New Mexico in 1563. In 1581, the Chamuscado and Rodríguez Expedition named the region north of the Rio Grande "San Felipe del Nuevo México"; the Spaniards had hoped to find wealthy indigenous Mexica cultures there similar to those of the Aztec Empire of the Valley of Mexico. The indigenous cultures of New Mexico, proved to be unrelated to the Mexicas, they were not wealthy, but the name persisted. Before statehood, the name "New Mexico" was applied to various configurations of the U.
S. territory, to a Mexican state, to a province of New Spain, all in the same general area, but of varying extensions. With a total area of 121,699 square miles, the state is the fifth-largest state of the US, larger than British Isles. New Mexico's eastern border lies along 103°W longitude with the state of Oklahoma, 2.2 miles west of 103°W longitude with Texas. On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, with Chihuahua making up about 90% of that; the western border with Arizona runs along the 109° 03'W longitude. The southwestern corner of the state is known as the Bootheel; the 37°N parallel forms the northern boundary with Colorado. The states of New Mexico, Colorado and Utah come together at the Four Corners in New Mexico's northwestern corner. New Mexico has no natural water sources