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π Visual calculus
Visual calculus, invented by Mamikon Mnatsakanian (known as Mamikon), is an approach to solving a variety of integral calculus problems. Many problems that would otherwise seem quite difficult yield to the method with hardly a line of calculation, often reminiscent of what Martin Gardner called "aha! solutions" or Roger Nelsen a proof without words.
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- "Visual calculus" | 2024-02-13 | 231 Upvotes 41 Comments
π Judas goat
A Judas goat is a trained goat used in general animal herding. The Judas goat is trained to associate with sheep or cattle, leading them to a specific destination. In stockyards, a Judas goat will lead sheep to slaughter, while its own life is spared. Judas goats are also used to lead other animals to specific pens and onto trucks. They have fallen out of use in recent times, but can still be found in various smaller slaughterhouses in some parts of the world, as well as conservation projects.
Cattle herders may use a Judas steer to serve the same purpose as a Judas goat. The technique, and the term, originated from cattle drives in the United States in the 1800s.
The term is a reference to Judas Iscariot, an apostle of Jesus Christ who betrayed Jesus in the Bible.
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- "Judas goat" | 2023-10-25 | 211 Upvotes 141 Comments
π Business Plot
The Business Plot was a political conspiracy in 1933 in the United States. Retired Marine Corps Major General Smedley Butler revealed that wealthy businessmen were plotting to create a fascist veterans' organization with Butler as its leader and use it in a coup d'Γ©tat to overthrow President Franklin D. Roosevelt. In 1934, Butler testified before the United States House of Representatives Special Committee on Un-American Activities (the "McCormackβDickstein Committee") on these revelations. No one was prosecuted.
At the time of the incidents, news media dismissed the plot, with a New York Times editorial characterizing it as a "gigantic hoax". While historians have not accepted the notion of a plot, they agree that Butler described one.
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- "The Business Plot of 1933" | 2026-04-18 | 16 Upvotes 4 Comments
- "Business Plot" | 2020-01-10 | 24 Upvotes 2 Comments
π Toba catastrophe theory
The Toba supereruption was a supervolcanic eruption that occurred about 75,000 years ago at the site of present-day Lake Toba in Sumatra, Indonesia. It is one of the Earth's largest known eruptions. The Toba catastrophe theory holds that this event caused a global volcanic winter of six to ten years and possibly a 1,000-year-long cooling episode.
In 1993, science journalist Ann Gibbons posited that a population bottleneck occurred in human evolution about 70,000 years ago, and she suggested that this was caused by the eruption. Geologist Michael R. Rampino of New York University and volcanologist Stephen Self of the University of Hawaii at Manoa support her suggestion. In 1998, the bottleneck theory was further developed by anthropologist Stanley H. Ambrose of the University of Illinois at UrbanaβChampaign. Both the link and global winter theories are controversial. The Toba event is the most closely studied supereruption.
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- "Toba Catastrophe Theory" | 2021-12-18 | 49 Upvotes 17 Comments
- "Toba catastrophe theory" | 2015-12-24 | 46 Upvotes 1 Comments
- "Toba catastrophe theory" | 2012-10-19 | 66 Upvotes 17 Comments
π Homey Airport
Area 51 is the common name of a highly classified United States Air Force (USAF) facility within the Nevada Test and Training Range. A remote detachment administered by Edwards Air Force Base, the facility is officially called Homey Airport (ICAO: KXTA, FAA LID: XTA) or Groom Lake (after the salt flat next to its airfield). Details of its operations are not made public, but the USAF says that it is an open training range, and it is commonly thought to support the development and testing of experimental aircraft and weapons systems. The USAF and CIA acquired the site in 1955, primarily for flight testing the Lockheed U-2 aircraft.
The intense secrecy surrounding the base has made it the frequent subject of conspiracy theories and a central component of unidentified flying object (UFO) folklore. It has never been declared a secret base, but all research and occurrences in Area 51 are Top Secret/Sensitive Compartmented Information (TS/SCI). The CIA publicly acknowledged the base's existence on 25 June 2013, following a Freedom of Information Act (FOIA) request filed in 2005 and declassified documents detailing its history and purpose.
Area 51 is located in the southern portion of Nevada, 83 miles (134Β km) north-northwest of Las Vegas. The surrounding area is a popular tourist destination, including the small town of Rachel on the "Extraterrestrial Highway".
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- "Homey Airport" | 2023-07-27 | 10 Upvotes 2 Comments
π Credit Unions
A credit union, a type of financial institution similar to a commercial bank, is a member-owned nonprofit financial cooperative. Credit unions generally provide services to members similar to retail banks, including deposit accounts, provision of credit, and other financial services. In several African countries, credit unions are commonly referred to as SACCOs (Savings and Credit Co-Operatives).
Worldwide, credit union systems vary significantly in their total assets and average institution asset size, ranging from volunteer operations with a handful of members to institutions with hundreds of thousands of members and assets worth billions of US dollars. In 2018, the number of members in credit unions worldwide was 274 million, with nearly 40Β million members having been added since 2016.
Leading up to the financial crisis of 2007β2008, commercial banks engaged in approximately five times more subprime lending relative to credit unions and were two and a half times more likely to fail during the crisis. American credit unions more than doubled lending to small businesses between 2008 and 2016, from $30Β billion to $60Β billion, while lending to small businesses overall during the same period declined by around $100Β billion. In the US, public trust in credit unions stands at 60%, compared to 30% for big banks. Furthermore, small businesses are 80% less likely to be dissatisfied with a credit union than with a big bank.
"Natural-person credit unions" (also called "retail credit unions" or "consumer credit unions") serve individuals, as distinguished from "corporate credit unions", which serve other credit unions.
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- "Credit Unions" | 2023-03-12 | 102 Upvotes 61 Comments
π Crookes Radiometer
The Crookes radiometer (also known as a light mill) consists of an airtight glass bulb containing a partial vacuum, with a set of vanes which are mounted on a spindle inside. The vanes rotate when exposed to light, with faster rotation for more intense light, providing a quantitative measurement of electromagnetic radiation intensity.
The reason for the rotation was a cause of much scientific debate in the ten years following the invention of the device, but in 1879 the currently accepted explanation for the rotation was published. Today the device is mainly used in physics education as a demonstration of a heat engine run by light energy.
It was invented in 1873 by the chemist Sir William Crookes as the by-product of some chemical research. In the course of very accurate quantitative chemical work, he was weighing samples in a partially evacuated chamber to reduce the effect of air currents, and noticed the weighings were disturbed when sunlight shone on the balance. Investigating this effect, he created the device named after him.
It is still manufactured and sold as an educational aid or for curiosity.
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- "Crookes Radiometer" | 2024-03-20 | 75 Upvotes 21 Comments
π List of probability distributions
Many probability distributions that are important in theory or applications have been given specific names.
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- "List of probability distributions" | 2013-05-25 | 47 Upvotes 36 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.
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- "John von Neumann" | 2015-06-26 | 20 Upvotes 3 Comments
π Chess Boxing
Chess boxing, or chessboxing, is a hybrid that combines two traditional pastimes: chess, a cerebral board game, and boxing, a physical sport. The competitors fight in alternating rounds of chess and boxing. Chessboxing was invented by French comic book artist Enki Bilal and adapted by Dutch performance artist Iepe Rubingh as an art performance and has subsequently grown into a competitive sport. Chessboxing is particularly popular in Germany, the United Kingdom, India, and Russia.
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- "Chess boxing" | 2018-05-15 | 219 Upvotes 110 Comments
- "Chess boxing" | 2010-10-13 | 44 Upvotes 37 Comments