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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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thought Experiment
A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is meant to test our intuitions about morality or other fundamental philosophical questions. History The ancient Greek , "was the most ancient pattern of mathematical proof", and existed before Euclidean geometry, 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 equivalent German term . Ørsted was also the first to use the equivalent term in 1820. By 1883, Ernst Mach used in a different sense, 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 hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minkowski Diagram
A spacetime diagram is a graphical illustration of locations in space at various times, especially in the special theory of relativity. Spacetime diagrams can show the geometry underlying phenomena like time dilation and length contraction without mathematical equations. The history of an object's location through time traces out a line or curve on a spacetime diagram, referred to as the object's world line. Each point in a spacetime diagram represents a unique position in space and time and is referred to as an event. The most well-known class of spacetime diagrams are known as Minkowski diagrams, developed by Hermann Minkowski in 1908. Minkowski diagrams are two-dimensional graphs that depict events as happening in a universe consisting of one space dimension and one time dimension. Unlike a regular distance-time graph, the distance is displayed on the horizontal axis and time on the vertical axis. Additionally, the time and space units of measurement are chosen in such a w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Paradox
A physical paradox is an apparent contradiction in physical descriptions of the universe. While multiple 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 e ... [...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 |
Bell's Spaceship Paradox
Bell's spaceship paradox is a thought experiment in special relativity. It was first described by E. Dewan and M. Beran in 1959 but became more widely known after John Stewart Bell elaborated the idea further in 1976.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 initially at rest in the inertial frame S. They start accelerating in the same direction simultaneously and equally, as measured in 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 incorre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolfgang Rindler
Wolfgang Rindler (18 May 1924 – 8 February 2019) was an Austrian 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 betw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Paradox
A physical paradox is an apparent contradiction in physical descriptions of the universe. While multiple 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 e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ladder Paradox Grate Variation
A ladder is a vertical or inclined set of rungs or steps commonly 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 ... [...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 * '' Junk: Record of the Last Hero'', a shōnen manga series by Kia Asamiya * '' Junk: The Golden Age of Debt'', a play by Ayad Akhtar Music * Junk (band), a British pop band * Junk (nightclub), in Southend-on-Sea, Essex, England Albums * ''Junk'', by Ferry Corsten, 2006 * ''Junk'', by Jejune, 1997 * ''Junk'', by Junk (band), 1995 * ''Junk'' (M83 album), 2016 Songs * "Junk" (song), released by Paul McCartney in 1970 * "Junk", song from Bronski Beat's album ''The Age of Consent'' (album) * "Junk", song from Zico Chain's album ''Food'' (Zico Chain album) 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 * Se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twin Paradox
In physics, the twin paradox is a thought experiment in special relativity involving twins, one of whom takes a space voyage at relativistic speeds and returns home to find that the twin who remained on Earth has aged more. This result appears puzzling because each twin sees the other twin as moving, and so, as a consequence of an incorrect and naive application of time dilation and the principle of relativity, each should paradoxically find the other to have aged less. However, this scenario can be resolved within the standard framework of special relativity: the travelling twin's trajectory involves two different inertial frames, one for the outbound journey and one for the inbound journey. Another way to understand the paradox is to realize the travelling twin is undergoing acceleration, which makes him a non-inertial observer. In both views there is no symmetry between the spacetime paths of the twins. Therefore, the twin paradox is not actually a paradox in the sense of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
