|
Hammar Experiment
The Hammar experiment was an experiment designed and conducted by Gustaf Wilhelm Hammar (1935) to test the aether drag hypothesis. Its negative result refuted some specific aether drag models, and confirmed special relativity. Overview Experiments such as the Michelson–Morley experiment of 1887 (and later other experiments such as the Trouton–Noble experiment in 1903 or the Trouton–Rankine experiment in 1908), presented evidence against the theory of a medium for light propagation known as the luminiferous aether; a theory that had been an established part of science for nearly one hundred years at the time. These results cast doubts on what was then a very central assumption of modern science, and later led to the development of special relativity. In an attempt to explain the results of the Michelson–Morley experiment in the context of the assumed medium, aether, many new hypotheses were examined. One of the proposals was that instead of passing through a static and unmov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gustaf Wilhelm Hammar
Gustaf Wilhelm Hammar (Gustav Vilhelm Hammar) (June 22, 1893 – August 19, 1954) was a Swedish-born American experimental physicist. He was the eldest of six children of Anders Vilhelm Hammar and Elin Christina Hammar (née Olsson). He emigrated to the United States in 1913, attended Bethel University in St. Paul, Minnesota, and by 1920 was married and living with his wife, Louise (with whom he was ultimately to have four children), in King County, Washington. He obtained his M.S. degree at the University of Idaho in 1924 and a Ph.D. from the California Institute of Technology in 1927. His Ph.D. dissertation topic was titled "Magnetic Susceptibilities of Some Common Gases." He returned to the University of Idaho in 1926 to teach, and became the head of the physics department in 1930, a position that he held for sixteen years. He led a productive materials science laboratory and was mindful of practical applications of his research—for example, as an extension of his re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hammar Experiment
The Hammar experiment was an experiment designed and conducted by Gustaf Wilhelm Hammar (1935) to test the aether drag hypothesis. Its negative result refuted some specific aether drag models, and confirmed special relativity. Overview Experiments such as the Michelson–Morley experiment of 1887 (and later other experiments such as the Trouton–Noble experiment in 1903 or the Trouton–Rankine experiment in 1908), presented evidence against the theory of a medium for light propagation known as the luminiferous aether; a theory that had been an established part of science for nearly one hundred years at the time. These results cast doubts on what was then a very central assumption of modern science, and later led to the development of special relativity. In an attempt to explain the results of the Michelson–Morley experiment in the context of the assumed medium, aether, many new hypotheses were examined. One of the proposals was that instead of passing through a static and unmov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michelson–Gale–Pearson Experiment
The Michelson–Gale–Pearson experiment (1925) is a modified version of the Michelson–Morley experiment and the Sagnac-Interferometer. It measured the Sagnac effect due to Earth's rotation, and thus tests the theories of special relativity and luminiferous ether along the rotating frame of Earth. Experiment The aim, as it was first proposed by Albert A. Michelson in 1904 and then executed in 1925 by Michelson and Henry G. Gale, was to find out whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The Michelson-Gale experiment was a very large ring interferometer, (a perimeter of 1.9 kilometers), large enough to detect the angular velocity of the Earth. Like the original Michelson-Morley experiment, the Michelson-Gale-Pearson version compared the light from a single source (carbon arc) after travelling in two directions. The major change was to replace the two "arms" of the original MM version with two rectangles, one much ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagnac Effect
The Sagnac effect, also called Sagnac interference, named after French physicist Georges Sagnac, is a phenomenon encountered in interferometry that is elicited by rotation. The Sagnac effect manifests itself in a setup called a ring interferometer or Sagnac interferometer. A beam of light is split and the two beams are made to follow the same path but in opposite directions. On return to the point of entry the two light beams are allowed to exit the ring and undergo interference. The relative phases of the two exiting beams, and thus the position of the interference fringes, are shifted according to the angular velocity of the apparatus. In other words, when the interferometer is at rest with respect to a nonrotating frame, the light takes the same amount of time to traverse the ring in either direction. However, when the interferometer system is spun, one beam of light has a longer path to travel than the other in order to complete one circuit of the mechanical frame, and so takes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aberration Of Light
In astronomy, aberration (also referred to as astronomical aberration, stellar aberration, or velocity aberration) is a phenomenon which produces an apparent motion of celestial objects about their true positions, dependent on the velocity of the observer. It causes objects to appear to be displaced towards the direction of motion of the observer compared to when the observer is stationary. The change in angle is of the order of ''v/c'' where ''c'' is the speed of light and ''v'' the velocity of the observer. In the case of "stellar" or "annual" aberration, the apparent position of a star to an observer on Earth varies periodically over the course of a year as the Earth's velocity changes as it revolves around the Sun, by a maximum angle of approximately 20 arcseconds in right ascension or declination. The term ''aberration'' has historically been used to refer to a number of related phenomena concerning the propagation of light in moving bodies. Aberration is distinct f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
François Arago
Dominique François Jean Arago ( ca, Domènec Francesc Joan Aragó), known simply as François Arago (; Catalan: ''Francesc Aragó'', ; 26 February 17862 October 1853), was a French mathematician, physicist, astronomer, freemason, supporter of the Carbonari revolutionaries and politician. Early life and work Arago was born at Estagel, a small village of 3,000 near Perpignan, in the ' of Pyrénées-Orientales, France, where his father held the position of Treasurer of the Mint. His parents were François Bonaventure Arago (1754–1814) and Marie Arago (1755–1845). Arago was the eldest of four brothers. Jean (1788–1836) emigrated to North America and became a general in the Mexican army. Jacques Étienne Victor (1799–1855) took part in Louis de Freycinet's exploring voyage in the ''Uranie'' from 1817 to 1821, and on his return to France devoted himself to his journalism and the drama. The fourth brother, Étienne Vincent (1802–1892), is said to have collaborated with Ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Augustin-Jean Fresnel
Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Isaac Newton, Newton's corpuscular theory of light, corpuscular theory, from the late 1830s until the end of the 19th century. He is perhaps better known for inventing the Catadioptric system, catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving countless lives at sea. The simpler Dioptrics, dioptric (purely refractive) stepped lens, first proposed by Georges-Louis Leclerc, Comte de Buffon, Count Buffon and independently reinvented by Fresnel, is used in screen magnifying glass, magnifiers and in condenser lenses for overhead projectors. By expressing Christiaan Huygens, Huygens's principle of secondary waves and Thomas Young (scientist), Young's principle of interference ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moscow, Idaho
Moscow ( ) is a city in North Central Idaho, United States. Located along the state border with Washington, it had a population of 25,435 at the 2020 census. The county seat and largest city of Latah County, Moscow is the home of the University of Idaho, the state's land-grant institution and primary research university. It is the principal city in the Moscow, Idaho Micropolitan Statistical Area, which includes all of Latah County. The city contains over 60% of the county's population, and while the university is Moscow's dominant employer, the city also serves as an agricultural and commercial hub for the Palouse region. Along with the rest of the Idaho Panhandle, Moscow is in the Pacific Time Zone. The elevation of its city center is above sea level. Two major highways serve the city, passing through the city center: US-95 (north-south) and ID-8 (east-west). The Pullman–Moscow Regional Airport, west, provides limited commercial air service. The local newspaper is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Howard Percy Robertson
Howard Percy "Bob" Robertson (January 27, 1903 – August 26, 1961) was an American mathematician and physicist known for contributions related to physical cosmology and the uncertainty principle. He was Professor of Mathematical Physics at the California Institute of Technology and Princeton University. Robertson made important contributions to the mathematics of quantum mechanics, general relativity and differential geometry. Applying relativity to cosmology, he independently developed the concept of an expanding universe. His name is most often associated with the Poynting–Robertson effect, the process by which solar radiation causes a dust mote orbiting a star to lose angular momentum, which he also described in terms of general relativity. During World War II, Robertson served with the National Defense Research Committee (NDRC) and the Office of Scientific Research and Development (OSRD). He served as Technical Consultant to the Secretary of War, the OSRD Liaison Officer i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entrainment (hydrodynamics)
Entrainment is the transport of fluid across an interface between two bodies of fluid by a shear-induced turbulent flux. Entrainment is important in turbulent jets, plumes, and gravity currents and is a topic of current research. History The entrainment hypothesis was first used as a model for flow in plumes by G. I. Taylor. He was studying the use of oil drum fires to clear fog from airplane runways during World War II. It became a common model of turbulence closure used in environmental and geophysical fluid mechanics. Applications Eductors or eductor-jet pumps make use of entrainment. They are used onboard ships to pump out flooded compartments: seawater is pumped to the eductor and forced through a jet, and any fluid at the inlet of the eductor is carried along to the outlet and up and out of the compartment. Eductors can pump out whatever can flow through them, including water, oil, and small pieces of wood. Another example is the pump-jet, which is used for marine p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagnac Interferometer
The Sagnac effect, also called Sagnac interference, named after French physicist Georges Sagnac, is a phenomenon encountered in interferometry that is elicited by rotation. The Sagnac effect manifests itself in a setup called a ring interferometer or Sagnac interferometer. A beam of light is split and the two beams are made to follow the same path but in opposite directions. On return to the point of entry the two light beams are allowed to exit the ring and undergo interference. The relative phases of the two exiting beams, and thus the position of the interference fringes, are shifted according to the angular velocity of the apparatus. In other words, when the interferometer is at rest with respect to a nonrotating frame, the light takes the same amount of time to traverse the ring in either direction. However, when the interferometer system is spun, one beam of light has a longer path to travel than the other in order to complete one circuit of the mechanical frame, and so takes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Review
''Physical Review'' is a peer-reviewed scientific journal established in 1893 by Edward Nichols. It publishes original research as well as scientific and literature reviews on all aspects of physics. It is published by the American Physical Society (APS). The journal is in its third series, and is split in several sub-journals each covering a particular field of physics. It has a sister journal, ''Physical Review Letters'', which publishes shorter articles of broader interest. History ''Physical Review'' commenced publication in July 1893, organized by Cornell University professor Edward Nichols and helped by the new president of Cornell, J. Gould Schurman. The journal was managed and edited at Cornell in upstate New York from 1893 to 1913 by Nichols, Ernest Merritt, and Frederick Bedell. The 33 volumes published during this time constitute ''Physical Review Series I''. The American Physical Society (APS), founded in 1899, took over its publication in 1913 and star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
