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Ladder Paradox
The ladder paradox (or barn-pole paradox) is a thought experiment in special relativity. It involves a ladder, parallel to the ground, travelling horizontally at relativistic speed (near the speed of light) and therefore undergoing a Lorentz length contraction. The ladder is imagined passing through the open front and rear doors of a garage or barn which is shorter than its rest length, so if the ladder was not moving it would not be able to fit inside. To a stationary observer, due to the contraction, the moving ladder is able to fit entirely inside the building as it passes through. On the other hand, from the point of view of an observer moving with the ladder, the ladder will not be contracted, and it is the building which will be Lorentz contracted to an even smaller length. Therefore, the ladder will not be able to fit inside the building as it passes through. This poses an apparent discrepancy between the realities of both observers. This apparent paradox results from the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thought Experiment
A thought experiment is a hypothetical situation in which a hypothesis, theory, or principle is laid out for the purpose of thinking through its consequences. History The ancient Greek ''deiknymi'' (), or thought experiment, "was the most ancient pattern of mathematical proof", and existed before Euclidean mathematics, where the emphasis was on the conceptual, rather than on the experimental part of a thought-experiment. Johann Witt-Hansen established that Hans Christian Ørsted was the first to use the German term ' (lit. thought experiment) circa 1812. Ørsted was also the first to use the equivalent term ' in 1820. By 1883 Ernst Mach used the term ' in a different way, to denote exclusively the conduct of a experiment that would be subsequently performed as a by his students. Physical and mental experimentation could then be contrasted: Mach asked his students to provide him with explanations whenever the results from their subsequent, real, physical experiment differed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supplee's Paradox
In relativistic physics, Supplee's paradox (also called the submarine paradox) is a physical paradox that arises when considering the buoyant force exerted on a relativistic bullet (or in a submarine) immersed in a fluid subject to an ambient gravitational field. If a bullet has neutral buoyancy when it is at rest in a perfect fluid and then it is launched with a relativistic speed, observers at rest within the fluid would conclude that the bullet should sink, since its density will increase due to the length contraction effect. On the other hand, in the bullet's proper frame it is the moving fluid that becomes denser and hence the bullet would float. But the bullet cannot sink in one frame and float in another, so there is a paradox situation. The paradox was first formulated by James M. Supplee (1989), where a non-rigorous explanation was presented. George Matsas has analysed this paradox in the scope of general relativity and also pointed out that these relativistic buoyancy effe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Paradox
A physical paradox is an apparent contradiction in physical descriptions of the universe. While many physical paradoxes have accepted resolutions, others defy resolution and may indicate flaws in theory. In physics as in all of science, contradictions and paradoxes are generally assumed to be artifacts of error and incompleteness because reality is assumed to be completely consistent, although this is itself a philosophical assumption. When, as in fields such as quantum physics and relativity theory, existing assumptions about reality have been shown to break down, this has usually been dealt with by changing our understanding of reality to a new one which remains self-consistent in the presence of the new evidence. Paradoxes relating to false assumptions Certain physical paradoxes defy common sense predictions about physical situations. In some cases, this is the result of modern physics correctly describing the natural world in circumstances which are far outside of every ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ehrenfest Paradox
The Ehrenfest paradox concerns the rotation of a "rigid" disc in the theory of relativity. In its original 1909 formulation as presented by Paul Ehrenfest in relation to the concept of Born rigidity within special relativity, it discusses an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius ''R'' as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R0 when stationary. However, the circumference (2''R'') should appear Lorentz-contracted to a smaller value than at rest, by the usual factor γ. This leads to the contradiction that ''R'' = ''R''0 ''and'' ''R'' < ''R''0. The has been deepened further by , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell's Spaceship Paradox
Bell's spaceship paradox is a thought experiment in special relativity. It was designed by E. Dewan and M. Beran in 1959 and became more widely known when J. S. Bell included a modified version.J. S. Bell: ''How to teach special relativity'', Progress in Scientific culture 1(2) (1976), pp. 1–13. Reprinted in J. S. Bell: ''Speakable and unspeakable in quantum mechanics'' (Cambridge University Press, 1987), chapter 9, pp. 67–80. A delicate thread hangs between two spaceships. They start accelerating simultaneously and equally as measured in the inertial frame S, thus having the same velocity at all times as viewed from S. Therefore, they are all subject to the same Lorentz contraction, so the entire assembly seems to be equally contracted in the S frame with respect to the length at the start. At first sight, it might appear that the thread will not break during acceleration. This argument, however, is incorrect as shown by Dewan and Beran and Bell. The distance between the spac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolfgang Rindler
Wolfgang Rindler (18 May 1924 – 8 February 2019) was a physicist working in the field of general relativity where he is known for introducing the term "event horizon", Rindler coordinates, and (in collaboration with Roger Penrose) for the use of spinors in general relativity. An honorary member of the Austrian Academy of Sciences and foreign member of the , he was also a prolific textbook author. Life and career Born in Vienna on 18 May 1924, Wolfgang Rindler was the son of a lawyer. In 1938, his mother sent him to England through the auspices of the Kindertransport rescue of Jewish children from Germany and Austria. He gained his B.Sc. and M.Sc. from the University of Liverpool and his PhD from Imperial College London. From 1956 to 1963 he taught at Cornell University. In 1960 Oliver & Boyd and InterScience published his first book on special relativity. Reviewer Alfred Schild said it was an "excellent, clear and concise account" and "provided a sound balance between physical i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Paradox
A physical paradox is an apparent contradiction in physical descriptions of the universe. While many physical paradoxes have accepted resolutions, others defy resolution and may indicate flaws in theory. In physics as in all of science, contradictions and paradoxes are generally assumed to be artifacts of error and incompleteness because reality is assumed to be completely consistent, although this is itself a philosophical assumption. When, as in fields such as quantum physics and relativity theory, existing assumptions about reality have been shown to break down, this has usually been dealt with by changing our understanding of reality to a new one which remains self-consistent in the presence of the new evidence. Paradoxes relating to false assumptions Certain physical paradoxes defy common sense predictions about physical situations. In some cases, this is the result of modern physics correctly describing the natural world in circumstances which are far outside of every ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ladder Paradox Grate Variation
A ladder is a vertical or inclined set of rungs or steps used for climbing or descending. There are two types: rigid ladders that are self-supporting or that may be leaned against a vertical surface such as a wall, and rollable ladders, such as those made of rope or aluminium, that may be hung from the top. The vertical members of a rigid ladder are called stringers or rails (US) or stiles (UK). Rigid ladders are usually portable, but some types are permanently fixed to a structure, building, or equipment. They are commonly made of metal, wood, or fiberglass, but they have been known to be made of tough plastic. Historical usages Ladders are ancient tools and technology. A ladder is featured in a Mesolithic rock painting that is at least 10,000 years old, depicted in the Spider Caves in Valencia, Spain. The painting depicts two humans using a ladder to reach a wild honeybee nest to harvest honey. The ladder is depicted as long and flexible, possibly made out of some sort of gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Junk2
Junk may refer to: Arts and entertainment * ''Junk'' (film), a 2000 Japanese horror film * '' J-U-N-K'', a 1920 American film * ''Junk'' (novel), by Melvin Burgess, 1996 * ''Junk'', a novel by Christopher Largen Music Groups * Junk (band), a British pop band Albums * ''Junk'', by Ferry Corsten, 2006 * ''Junk'', by Jejune, 1997 * ''Junk'', by Junk (band), 1995 * ''Junk'' (M83 album), 2016 Songs * "Junk" (song), written by Paul McCartney in 1970 * "Junk", song from Zico Chain's ''Food'' album Other uses in arts and entertainment * '' Junk: Record of the Last Hero'', a shōnen manga series by Kia Asamiya * '' Junk: The Golden Age of Debt'', a play by Ayad Akhtar Finance * Junk bond * Junk status, a debt credit rating People * Bruno Junk (1929–1995), Estonian race walker, two-time Olympic bronze medal winner * Janson Junk (born 1996), American baseball pitcher * Sebastian Junk (born 1983), German Paralympic judoka * Wilhelm Junk (1866–1942), Czech-born antiquarian books ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
