Random Articles (Page 4)
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π Twike
The Twike (a portmanteau of the words twin and bike) is a human-electric hybrid vehicle (HEHV) designed to carry two passengers and cargo. Essentially a velomobile with an electrical hybrid engine, it can be driven in electric-only mode or electric + pedal power mode. Pedaling warms the user, making electric heating in winter unnecessary, extends the range of the vehicle but does not substantially add to the vehicle's top speed.
Constructed of lightweight materials such as aluminium (frame) and plastic (shell), the 246Β kg (542Β lb) (unladen, varying with battery weight) tricycle vehicle first used NiCd batteries, later Li-Mn, LiFePO4 and LiIon. Typically ranges reach from 50 to over 500Β km depending on battery size, type, status on one side and speed and altitude profile and load on the other. Energy is reclaimed while driving through regenerative braking, and load is removed from the electric system by use of the pedalling system which transfers its input directly to the drivetrain (i.e., both systems operate in parallel, not in series).
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- "Twike" | 2021-07-21 | 275 Upvotes 195 Comments
π Tobler's First Law of Geography
The First Law of Geography, according to Waldo Tobler, is "everything is related to everything else, but near things are more related than distant things." This first law is the foundation of the fundamental concepts of spatial dependence and spatial autocorrelation and is utilized specifically for the inverse distance weighting method for spatial interpolation and to support the regionalized variable theory for kriging. It is a modern formulation of David Hume's principle of contiguity.
Tobler first presented his seminal idea during a meeting of the International Geographical Union's Commission on Qualitative Methods held in 1969 and later published by him in 1970. Though simple in its presentation, this idea is profound. Without it, "the full range of conditions anywhere on the Earth's surface could in principle be found packed within any small area. There would be no regions of approximately homogeneous conditions to be described by giving attributes to area objects. Topographic surfaces would vary chaotically, with slopes that were everywhere infinite, and the contours of such surfaces would be infinitely dense and contorted. Spatial analysis, and indeed life itself, would be impossible."
Less well known is his second law, which complements the first: "The phenomenon external to an area of interest affects what goes on inside".
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- "Tobler's First Law of Geography" | 2020-10-30 | 63 Upvotes 17 Comments
π Dihydrogen monoxide hoax
The dihydrogen monoxide parody involves calling water by an unfamiliar chemical name, most often "dihydrogen monoxide" (DHMO), and listing some of water's well-known effects in a particularly alarming manner, such as accelerating corrosion and causing suffocation. The parody often calls for dihydrogen monoxide to be banned, regulated, or labeled as dangerous. It demonstrates how a lack of scientific literacy and an exaggerated analysis can lead to misplaced fears.
The parody has been used with other chemical names, including "dihydrogen oxide", "hydroxyl acid", and "hydroxylic acid".
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- "Dihydrogen Monoxide Parody" | 2023-09-03 | 14 Upvotes 3 Comments
- "Dihydrogen Monoxide" | 2021-09-25 | 20 Upvotes 8 Comments
- "Dihydrogen monoxide hoax" | 2016-09-29 | 13 Upvotes 2 Comments
π Unreal Mode
In x86 computing, unreal mode, also big real mode, huge real mode, flat real mode, or voodoo mode is a variant of real mode, in which one or more segment descriptors has been loaded with non-standard values, like 32-bit limits allowing access to the entire memory. Contrary to its name, it is not a separate addressing mode that the x86 processors can operate in. It is used in the 80286 and later x86 processors.
Discussed on
- "Unreal Mode" | 2019-03-18 | 27 Upvotes 1 Comments
π Rabbit-proof fence
The State Barrier Fence of Western Australia, formerly known as the Rabbit Proof Fence, the State Vermin Fence, and the Emu Fence, is a pest-exclusion fence constructed between 1901 and 1907 to keep rabbits and other agricultural pests, from the east, out of Western Australian pastoral areas.
There are three fences in Western Australia: the original No. 1 Fence crosses the state from north to south, No. 2 Fence is smaller and further west, and No. 3 Fence is smaller still and runs eastβwest. The fences took six years to build. When completed in 1907, the rabbit-proof fence (including all three fences) stretched 2,023 miles (3,256Β km). The cost to build the fences at the time was about Β£168 per mile ($250/km).
When it was completed in 1907, the 1,139-mile (1,833Β km) No. 1 Fence was the longest unbroken fence in the world.
Discussed on
- "Rabbit-proof fence" | 2014-06-06 | 49 Upvotes 36 Comments
π List of National Emergencies in the United States
A national emergency is a situation in which a government is empowered to perform actions not normally permitted. The 1976 National Emergencies Act implemented various legal requirements regarding emergencies declared by the President of the United States.
Between the enactment of the National Emergencies Act in 1976 through March 13, 2020, 61 emergencies have been declared; 27 have expired while 34 are currently in effect, each having been renewed annually by the president.
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- "List of National Emergencies in the United States" | 2019-02-15 | 19 Upvotes 2 Comments
π Motte-and-Bailey Fallacy
The motte-and-bailey fallacy (named after the motte-and-bailey castle) is a form of argument and an informal fallacy where an arguer conflates two positions which share similarities, one modest and easy to defend (the "motte") and one much more controversial (the "bailey"). The arguer advances the controversial position, but when challenged, they insist that they are only advancing the more modest position. Upon retreating to the motte, the arguer can claim that the bailey has not been refuted (because the critic refused to attack the motte) or that the critic is unreasonable (by equating an attack on the bailey with an attack on the motte).
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- "Motte-and-Bailey Fallacy" | 2022-02-08 | 29 Upvotes 1 Comments
- "Motte-and-Bailey Fallacy" | 2021-04-04 | 15 Upvotes 6 Comments
π John von Neumann
John von Neumann (; Hungarian: Neumann JΓ‘nos Lajos, pronouncedΒ [ΛnΙjmΙn ΛjaΛnoΚ ΛlΙjoΚ]; December 28, 1903Β β FebruaryΒ 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. Von Neumann was generally regarded as the foremost mathematician of his time and said to be "the last representative of the great mathematicians"; who integrated both pure and applied sciences.
He made major contributions to a number of fields, including mathematics (foundations of mathematics, functional analysis, ergodic theory, representation theory, operator algebras, geometry, topology, and numerical analysis), physics (quantum mechanics, hydrodynamics, and quantum statistical mechanics), economics (game theory), computing (Von Neumann architecture, linear programming, self-replicating machines, stochastic computing), and statistics.
He was a pioneer of the application of operator theory to quantum mechanics in the development of functional analysis, and a key figure in the development of game theory and the concepts of cellular automata, the universal constructor and the digital computer.
He published over 150 papers in his life: about 60 in pure mathematics, 60 in applied mathematics, 20 in physics, and the remainder on special mathematical subjects or non-mathematical ones. His last work, an unfinished manuscript written while he was in hospital, was later published in book form as The Computer and the Brain.
His analysis of the structure of self-replication preceded the discovery of the structure of DNA. In a short list of facts about his life he submitted to the National Academy of Sciences, he stated, "The part of my work I consider most essential is that on quantum mechanics, which developed in GΓΆttingen in 1926, and subsequently in Berlin in 1927β1929. Also, my work on various forms of operator theory, Berlin 1930 and Princeton 1935β1939; on the ergodic theorem, Princeton, 1931β1932."
During World War II, von Neumann worked on the Manhattan Project with theoretical physicist Edward Teller, mathematician StanisΕaw Ulam and others, problem solving key steps in the nuclear physics involved in thermonuclear reactions and the hydrogen bomb. He developed the mathematical models behind the explosive lenses used in the implosion-type nuclear weapon, and coined the term "kiloton" (of TNT), as a measure of the explosive force generated.
After the war, he served on the General Advisory Committee of the United States Atomic Energy Commission, and consulted for a number of organizations, including the United States Air Force, the Army's Ballistic Research Laboratory, the Armed Forces Special Weapons Project, and the Lawrence Livermore National Laboratory. As a Hungarian Γ©migrΓ©, concerned that the Soviets would achieve nuclear superiority, he designed and promoted the policy of mutually assured destruction to limit the arms race.
Discussed on
- "John von Neumann" | 2015-06-26 | 20 Upvotes 3 Comments
π Berry Paradox
The Berry paradox is a self-referential paradox arising from an expression like "The smallest positive integer not definable in under sixty letters" (a phrase with fifty-seven letters).
Bertrand Russell, the first to discuss the paradox in print, attributed it to G. G. Berry (1867β1928), a junior librarian at Oxford's Bodleian Library. Russell called Berry "the only person in Oxford who understood mathematical logic". The paradox was called "Richard's paradox" by Jean-Yves Gerard".
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- "Berry Paradox" | 2022-08-19 | 27 Upvotes 4 Comments
π Nothing about us without us
"Nothing about us without us" (Latin: Nihil de nobis, sine nobis) is a slogan used to communicate the idea that no policy should be decided by any representative without the full and direct participation of members of the group(s) affected by that policy. In its modern form, this often involves national, ethnic, disability-based, or other groups that are often marginalized from political, social, and economic opportunities.
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- "Nothing about us without us" | 2025-02-16 | 38 Upvotes 7 Comments