Have a deep view into what people are curious about.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry

Improvised firearms (sometimes called zip guns or pipe guns) are firearms manufactured other than by a firearms manufacturer or a gunsmith, and are typically constructed by adapting existing materials to the purpose. They range in quality from crude weapons that are as much a danger to the user as the target to high-quality arms produced by cottage industries using salvaged and repurposed materials.

Improvised firearms are commonly used as tools by criminals and insurgents and are often associated with such groups; other uses include self-defense in lawless areas and hunting game in poor rural areas.

🔗 France 🔗 Middle Ages 🔗 Middle Ages/History

The Bal des Ardents (Ball of the Burning Men) or Bal des Sauvages (Ball of the Wild Men) was a masquerade ball held on 28 January 1393 in Paris at which Charles VI of France performed in a dance with five members of the French nobility. Four of the dancers were killed in a fire caused by a torch brought in by a spectator, Charles's brother Louis I, Duke of Orléans. Charles and another of the dancers survived. The ball was one of a number of events intended to entertain the young king, who the previous summer had suffered an attack of insanity. The event undermined confidence in Charles's capacity to rule; Parisians considered it proof of courtly decadence and threatened to rebel against the more powerful members of the nobility. The public's outrage forced the king and his brother Orléans, whom a contemporary chronicler accused of attempted regicide and sorcery, to offer penance for the event.

Charles's wife, Isabeau of Bavaria, held the ball to honor the remarriage of a lady-in-waiting. Scholars believe the dance performed at the ball had elements of traditional charivari, with the dancers disguised as wild men, mythical beings often associated with demonology, that were commonly represented in medieval Europe and documented in revels of Tudor England. The event was chronicled by contemporary writers such as the Monk of St Denis and Jean Froissart, and illustrated in a number of 15th-century illuminated manuscripts by painters such as the Master of Anthony of Burgundy. The incident later provided inspiration for Edgar Allan Poe's short story Hop-Frog.

🔗 Linguistics 🔗 Linguistics/Applied Linguistics 🔗 Judaism 🔗 Israel

The revival of the Hebrew language took place in Europe and Palestine toward the end of the 19th century and into the 20th century, through which the language's usage changed from the sacred language of Judaism to a spoken and written language used for daily life in Israel. The process began as a diversity of Jews started arriving and establishing themselves alongside the pre-existing Jewish community in the region of Palestine in the first half of the nineteenth century, when veteran Jews in Palestine (largely Arabic-speaking by that time) and the linguistically diverse newly arrived Jews all switched to use Hebrew as a lingua franca, the historical linguistic common denominator of all the Jewish groups. At the same time, a parallel development in Europe changed Hebrew from primarily a sacred liturgical language into a literary language which played a key role in the development of nationalist educational programs. Modern Hebrew was one of three official languages of Mandatory Palestine, and after the Israeli Declaration of Independence in 1948, one of two official languages of Israel, along with Modern Arabic. In July 2018, a new law made Hebrew the sole official language of the state of Israel, with Arabic having "special status". More than purely a linguistic process, the revival of Hebrew was utilized by Jewish modernization and political movements, and became a tenet of the ideology associated with settlement of the land, Zionism and Israeli policy.

The process of Hebrew's return to regular usage is unique; there are no other examples of a natural language without any native speakers subsequently acquiring several million native speakers, and no other examples of a sacred language becoming a national language with millions of "first language" speakers.

The language's revival eventually brought linguistic additions with it. While the initial leaders of the process insisted they were only continuing "from the place where Hebrew's vitality was ended", what was created represented a broader basis of language acceptance; it includes characteristics derived from all periods of Hebrew language, as well as from the non-Hebrew languages used by the long-established European, North African, and Middle Eastern Jewish communities, with Yiddish (the European variant) being predominant.

🔗 Georgia (U.S. state) 🔗 Caves

Ellison's Cave is a pit cave located in Walker County, on Pigeon Mountain in the Appalachian Plateaus of Northwest Georgia. It is the 12th deepest cave in the United States and features the deepest, unobstructed pit in the continental US named Fantastic Pit. The cave is over 12 miles long and extends 1063 feet vertically.

🔗 Korea 🔗 Architecture

Ondol (ON-dol; , Korean: 온돌; Hanja: 溫突/溫堗; Korean pronunciation: [on.dol]) or gudeul (구들; [ku.dɯl]) in Korean traditional architecture is underfloor heating that uses direct heat transfer from wood smoke to heat the underside of a thick masonry floor. In modern usage, it refers to any type of underfloor heating, or to a hotel or a sleeping room in Korean (as opposed to Western) style.

The main components of the traditional ondol are an agungi (아궁이; [a.guŋ.i]), a firebox or stove, accessible from an adjoining room (typically kitchen or master bedroom), a raised masonry floor underlain by horizontal smoke passages, and a vertical, freestanding chimney on the opposite exterior wall providing a draft. The heated floor, supported by stone piers or baffles to distribute the smoke, is covered by stone slabs, clay and an impervious layer such as oiled paper.

🔗 Olympics 🔗 Classical Greece and Rome 🔗 Greece 🔗 Martial arts 🔗 Mixed martial arts

Pankration (; Greek: παγκράτιον) was a sporting event introduced into the Greek Olympic Games in 648 BC and was an empty-hand submission sport with scarcely any rules. The athletes used boxing and wrestling techniques, but also others, such as kicking and holds, locks and chokes on the ground. The term comes from the Greek παγκράτιον [paŋkrátion], literally meaning "all of power" from πᾶν (pan) "all" and κράτος (kratos) "strength, might, power".

It was known in ancient times for its ferocity and allowance of such tactics as knees to the head and eye gouging. One ancient account tells of a situation in which the judges were trying to determine the winner of a match. The difficulty lay in that fact that both men had died in the arena from their injuries, making it hard to determine a victor. Eventually, the judges decided the winner was the one who didn't have his eyes gouged out. Over time, however, maneuvers like eye gouging were discouraged to prevent such unpleasant incidents.

🔗 Mathematics

In mathematical logic, Goodstein's theorem is a statement about the natural numbers, proved by Reuben Goodstein in 1944, which states that every Goodstein sequence eventually terminates at 0. Laurence Kirby and Jeff Paris showed that it is unprovable in Peano arithmetic (but it can be proven in stronger systems, such as second-order arithmetic). This was the third example of a true statement about natural numbers that is unprovable in Peano arithmetic, after the examples provided by Gödel's incompleteness theorem and Gerhard Gentzen's 1943 direct proof of the unprovability of ε₀-induction in Peano arithmetic. The Paris–Harrington theorem gave another example.

Kirby and Paris introduced a graph-theoretic hydra game with behavior similar to that of Goodstein sequences: the "Hydra" (named for the mythological multi-headed Hydra of Lerna) is a rooted tree, and a move consists of cutting off one of its "heads" (a branch of the tree), to which the hydra responds by growing a finite number of new heads according to certain rules. Kirby and Paris proved that the Hydra will eventually be killed, regardless of the strategy that Hercules uses to chop off its heads, though this may take a very long time. Just like for Goodstein sequences, Kirby and Paris showed that it cannot be proven in Peano arithmetic alone.

🔗 Computing

Plankalkül (German pronunciation: [ˈplaːnkalkyːl]) is a programming language designed for engineering purposes by Konrad Zuse between 1942 and 1945. It was the first high-level programming language to be designed for a computer.

Kalkül is the German term for a formal system—as in Hilbert-Kalkül, the original name for the Hilbert-style deduction system—so Plankalkül refers to a formal system for planning.

🔗 Economics 🔗 Statistics 🔗 Business 🔗 Politics

Goodhart's law is an adage named after economist Charles Goodhart, which has been phrased by Marilyn Strathern as "When a measure becomes a target, it ceases to be a good measure." One way in which this can occur is individuals trying to anticipate the effect of a policy and then taking actions that alter its outcome.