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π 1 + 2 + 3 + .. = -1/12
Ramanujan summation is a technique invented by the mathematician Srinivasa Ramanujan for assigning a value to divergent infinite series. Although the Ramanujan summation of a divergent series is not a sum in the traditional sense, it has properties which make it mathematically useful in the study of divergent infinite series, for which conventional summation is undefined.
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- "1 + 2 + 3 + .. = -1/12" | 2014-01-14 | 13 Upvotes 19 Comments
π Ali Qushji
Ala al-DΔ«n Ali ibn Muhammed (1403 β 16 December 1474), known as Ali Qushji (Ottoman Turkish/Persian language: ΨΉΩΫ ΩΩΨ΄ΪΫ, kuΕΓ§u β falconer in Turkish; Latin: Ali Kushgii) was an astronomer, mathematician and physicist originally from Samarkand, who settled in the Ottoman Empire some time before 1472. As a disciple of Ulugh Beg, he is best known for the development of astronomical physics independent from natural philosophy, and for providing empirical evidence for the Earth's rotation in his treatise, Concerning the Supposed Dependence of Astronomy upon Philosophy. In addition to his contributions to Ulugh Beg's famous work Zij-i-Sultani and to the founding of Sahn-Δ± Seman Medrese, one of the first centers for the study of various traditional Islamic sciences in the Ottoman caliphate, Ali KuΕΓ§u was also the author of several scientific works and textbooks on astronomy.
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- "Ali Qushji" | 2017-03-26 | 19 Upvotes 8 Comments
π Turnspit Dog
The turnspit dog was a short-legged, long-bodied dog bred to run on a wheel, called a turnspit or dog wheel, to turn meat. It is mentioned in Of English Dogs in 1576 under the name "Turnespete". William Bingley's Memoirs of British Quadrupeds (1809) also talks of a dog employed to help chefs and cooks. It was also known as the Kitchen Dog, the Cooking Dog, or the Wheeling Dog. In Linnaeus's 18th-century classification of dogs it is listed as Canis vertigus (also used as Latin name for the Dachshund). The breed was lost, since it was considered to be such a lowly and common dog that no record was effectively kept of it. Some sources consider the turnspit dog a kind of Glen of Imaal Terrier, while others make it a relative of the Welsh Corgi.
With advancements in kitchen technology, the need for turnspit dogs declined. Over time, they were no longer bred for their specific function, and their numbers dwindled, eventually leading to their extinction.
A preserved example of a turnspit dog is displayed at Abergavenny Museum in Abergavenny, Wales.
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- "Turnspit Dog" | 2026-05-17 | 22 Upvotes 4 Comments
π Tweel β Airless Wheel
The Tweel (a portmanteau of tire and wheel) is an airless tire design developed by the French tire company Michelin. Its significant advantage over pneumatic tires is that the Tweel does not use a bladder full of compressed air, and therefore cannot burst, leak pressure, or become flat. Instead, the Tweel's hub is connected to the rim via flexible polyurethane spokes which fulfil the shock-absorbing role provided by the compressed air in a traditional tire.
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- "Tweel β Airless Wheel" | 2015-02-24 | 40 Upvotes 16 Comments
π Presidential Immunity in the United States
Presidential immunity is the concept that sitting presidents of the United States have civil or criminal immunity for their official acts. Neither civil nor criminal immunity is explicitly granted in the Constitution or any federal statute. However, the Supreme Court of the United States ruled in Trump v. United States (2024) that all presidents have absolute criminal immunity for official acts under core constitutional powers, presumptive immunity for other official acts. The court held that there is no immunity for unofficial acts. The court made this decision after former President Trump claimed immunity from prosecution for actions performed within the perimeter of his responsibilities as president.
Previously, the Supreme Court had found in Nixon v. Fitzgerald (1982) that the president has absolute immunity from civil damages actions regarding conduct within the "outer perimeter" of their duties. However, in Clinton v. Jones (1997), the court ruled against temporary immunity for sitting presidents from suits arising from pre-presidency conduct. Some scholars suggested an immunity from arrest and criminal prosecution as well, a view which became the practice of the Department of Justice under a pair of memoranda (1973 and 2000) from the Office of Legal Counsel. Presidents Richard Nixon, Bill Clinton, and Donald Trump were criminally investigated while in office, but none were prosecuted while still in office.
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- "Presidential Immunity in the United States" | 2026-01-12 | 79 Upvotes 66 Comments
π List of mass shootings in the United States in 2022
This is a list of shootings in the United States that have occurred in 2022. Mass shootings are incidents involving several victims of firearm-related violence. The precise inclusion criteria are disputed, and there is no broadly accepted definition.
Gun Violence Archive, a nonprofit research group, run by Tracy Holtan, that tracks shootings and their characteristics in the United States, defines a mass shooting as an incident in which four or more people, excluding the perpetrator(s), are shot in one location at roughly the same time. The Congressional Research Service narrows that definition, limiting it to "public mass shootings", defined by four or more victims killed, excluding any victims who survive. The Washington Post and Mother Jones use similar definitions, with the latter acknowledging that their definition "is a conservative measure of the problem", as many shootings with fewer fatalities occur. The crowdsourced Mass Shooting Tracker project has the most expansive definition of four or more shot in any incident, including the perpetrator in the victim inclusion criteria.
A 2019 study of mass shootings published in the journal Injury Epidemiology recommended developing "a standard definition that considers both fatalities and nonfatalities to most appropriately convey the burden of mass shootings on gun violence." The authors of the study further suggested that "the definition of mass shooting should be four or more people, excluding the shooter, who are shot in a single event regardless of the motive, setting or number of deaths."
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- "List of mass shootings in the United States in 2022" | 2022-05-25 | 11 Upvotes 1 Comments
π Pessimism Porn
Pessimism porn is a neologism coined in 2009 during the 2007β2012 global financial crisis to describe the alleged eschatological and survivalist thrill some people derive from predicting, reading and fantasizing about the collapse of civil society through the destruction of the world's economic system.
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- "Pessimism Porn" | 2016-09-05 | 13 Upvotes 1 Comments
π Xenu, Leader of the Galactic Federation
Xenu (), also called Xemu, was, according to Scientology founder L. Ron Hubbard, the dictator of the "Galactic Confederacy" who brought billions of his people to Earth (then known as "Teegeeack") in DC-8-like spacecraft 75 million years ago, stacked them around volcanoes, and killed them with hydrogen bombs. Official Scientology scriptures hold that the thetans (immortal spirits) of these aliens adhere to humans, causing spiritual harm.
These events are known within Scientology as "Incident II", and the traumatic memories associated with them as "The Wall of Fire" or "R6 implant". The narrative of Xenu is part of Scientologist teachings about extraterrestrial civilizations and alien interventions in earthly events, collectively described as "space opera" by Hubbard. Hubbard detailed the story in Operating Thetan level III (OT III) in 1967, warning that the "R6 implant" (past trauma) was "calculated to kill (by pneumonia, etc.) anyone who attempts to solve it".
Within the Church of Scientology, the Xenu story is part of the church's secret "Advanced Technology", considered a sacred and esoteric teaching, which is normally only revealed to members who have completed a lengthy sequence of courses costing large amounts of money. The church avoids mention of Xenu in public statements and has gone to considerable effort to maintain the story's confidentiality, including legal action on the grounds of copyright and trade secrecy. Officials of the Church of Scientology widely deny or try to hide the Xenu story. Despite this, much material on Xenu has leaked to the public via court documents and copies of Hubbard's notes that have been distributed through the Internet. In commentary on the impact of the Xenu text, academic scholars have discussed and analyzed the writings by Hubbard and their place within Scientology within the contexts of science fiction, UFO religions, Gnosticism and creation myths.
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- "Xenu, Leader of the Galactic Federation" | 2020-12-08 | 11 Upvotes 4 Comments
π The Calutron Girls
The Calutron Girls were a group of young women, mostly high school graduates who joined the World War II efforts in Oak Ridge, Tennessee in 1945.
Although they were not allowed to know at the time, they were monitoring dials and watching meters for a calutron, a mass spectrometer that separates uranium isotopes. The enriched uranium was used to make the first atomic bomb.
Calutron Girls were trained and employed at the Y-12 National Security Complex. Wartime labor shortages forced the Tennessee Eastman Corporation to hire women to work at the Y-12 plant.
According to Gladys Owens, one of the few Calutron Girls, a manager at the facility once told them: "We can train you how to do what is needed, but cannot tell you what you are doing. I can only tell you that if our enemies beat us to it, God have mercy on us!"
π Tarski's high school algebra problem
In mathematical logic, Tarski's high school algebra problem was a question posed by Alfred Tarski. It asks whether there are identities involving addition, multiplication, and exponentiation over the positive integers that cannot be proved using eleven axioms about these operations that are taught in high-school-level mathematics. The question was solved in 1980 by Alex Wilkie, who showed that such unprovable identities do exist.
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- "Tarski's high school algebra problem" | 2013-03-07 | 76 Upvotes 18 Comments