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🔗 Environment

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/Canadian military history

The Royal Canadian Air Force Exercise Plans are two exercise plans developed for the Royal Canadian Air Force (RCAF) by Dr. Bill Orban in the late 1950s, first published in 1961. The 5BX plan (Five Basic Exercises) was developed for men; a corresponding program was developed for women under the name XBX (Ten Basic Exercises) and the two plans were subsequently published together as one book. The popularity of the programs in many countries around the world helped to launch modern fitness culture.

🔗 Companies 🔗 History 🔗 Architecture 🔗 Buddhism 🔗 Japan 🔗 Japan/History 🔗 Japan/Business and economy

Kongō Gumi Co., Ltd. (株式会社金剛組, Kabushiki Gaisha Kongō Gumi) is a Japanese construction company which was the world's oldest continuously ongoing independent company, operating for over 1,400 years. In January 2006, it became a subsidiary of Takamatsu.

🔗 Typography

"The quick brown fox jumps over the lazy dog" is an English-language pangram—a sentence that contains all of the letters of the alphabet. It is commonly used for touch-typing practice, testing typewriters and computer keyboards, displaying examples of fonts, and other applications involving text where the use of all letters in the alphabet is desired. Owing to its brevity and coherence, it has become widely known.

🔗 Games

Nim is a mathematical game of strategy in which two players take turns removing (or "nimming") objects from distinct heaps or piles. On each turn, a player must remove at least one object, and may remove any number of objects provided they all come from the same heap or pile. Depending on the version being played, the goal of the game is either to avoid taking the last object, or to take the last object.

Variants of Nim have been played since ancient times. The game is said to have originated in China—it closely resembles the Chinese game of 捡石子 jiǎn-shízi, or "picking stones"—but the origin is uncertain; the earliest European references to Nim are from the beginning of the 16th century. Its current name was coined by Charles L. Bouton of Harvard University, who also developed the complete theory of the game in 1901, but the origins of the name were never fully explained.

Nim is typically played as a misère game, in which the player to take the last object loses. Nim can also be played as a normal play game, where the player taking the last object wins. This is called normal play because the last move is a winning move in most games, even though it is not the normal way that Nim is played. In either normal play or a misère game, when the number of heaps with at least two objects is exactly equal to one, the next player who takes next can easily win. If this removes either all or all but one objects from the heap that has two or more, then no heaps will have more than one object, so the players are forced to alternate removing exactly one object until the game ends. If the player leaves an even number of non-zero heaps (as the player would do in normal play), the player takes last; if the player leaves an odd number of heaps (as the player would do in misère play), then the other player takes last.

Normal play Nim (or more precisely the system of nimbers) is fundamental to the Sprague–Grundy theorem, which essentially says that in normal play every impartial game is equivalent to a Nim heap that yields the same outcome when played in parallel with other normal play impartial games (see disjunctive sum).

While all normal play impartial games can be assigned a Nim value, that is not the case under the misère convention. Only tame games can be played using the same strategy as misère Nim.

Nim is a special case of a poset game where the poset consists of disjoint chains (the heaps).

The evolution graph of the game of Nim with three heaps is the same as three branches of the evolution graph of the Ulam-Warburton automaton.

At the 1940 New York World's Fair Westinghouse displayed a machine, the Nimatron, that played Nim. From May 11, 1940 to October 27, 1940 only a few people were able to beat the machine in that six week period; if they did they were presented with a coin that said Nim Champ. It was also one of the first ever electronic computerized games. Ferranti built a Nim playing computer which was displayed at the Festival of Britain in 1951. In 1952 Herbert Koppel, Eugene Grant and Howard Bailer, engineers from the W. L. Maxon Corporation, developed a machine weighing 23 kilograms (50 lb) which played Nim against a human opponent and regularly won. A Nim Playing Machine has been described made from TinkerToy.

The game of Nim was the subject of Martin Gardner's February 1958 Mathematical Games column in Scientific American. A version of Nim is played—and has symbolic importance—in the French New Wave film Last Year at Marienbad (1961).

🔗 Physics 🔗 Philosophy 🔗 Skepticism 🔗 History of Science 🔗 Science

Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

There are still some deficiencies in the Standard Model of physics, such as the origin of mass, the strong CP problem, neutrino mass, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself—the Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions (for example within known spacetime singularities like the Big Bang and the centers of black holes beyond the event horizon).

🔗 Spaceflight 🔗 Astronomy 🔗 Engineering 🔗 Astronomy/Astronomical objects

A Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output. The concept is a thought experiment that attempts to explain how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Only a tiny fraction of a star's energy emissions reach the surface of any orbiting planet. Building structures encircling a star would enable a civilization to harvest far more energy.

The first contemporary description of the structure was by Olaf Stapledon in his science fiction novel Star Maker (1937), in which he described "every solar system... surrounded by a gauze of light traps, which focused the escaping solar energy for intelligent use." The concept was later popularized by Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation." Dyson speculated that such structures would be the logical consequence of the escalating energy needs of a technological civilization and would be a necessity for its long-term survival. He proposed that searching for such structures could lead to the detection of advanced, intelligent extraterrestrial life. Different types of Dyson spheres and their energy-harvesting ability would correspond to levels of technological advancement on the Kardashev scale.

Since then, other variant designs involving building an artificial structure or series of structures to encompass a star have been proposed in exploratory engineering or described in science fiction under the name "Dyson sphere". These later proposals have not been limited to solar-power stations, with many involving habitation or industrial elements. Most fictional depictions describe a solid shell of matter enclosing a star, which was considered by Dyson himself the least plausible variant of the idea. In May 2013, at the Starship Century Symposium in San Diego, Dyson repeated his comments that he wished the concept had not been named after him.

🔗 United States 🔗 Mathematics 🔗 Education 🔗 United States/Massachusetts 🔗 Higher Education

Math 55 is a two-semester long first-year undergraduate mathematics course at Harvard University, founded by Lynn Loomis and Shlomo Sternberg. The official titles of the course are Honors Abstract Algebra (Math 55a) and Honors Real and Complex Analysis (Math 55b). Previously, the official title was Honors Advanced Calculus and Linear Algebra.

🔗 Soviet Union 🔗 Russia 🔗 Law 🔗 Politics 🔗 Cities 🔗 Russia/Russian, Soviet, and CIS military history 🔗 Russia/politics and law of Russia 🔗 Russia/human geography of Russia

A closed city or closed town is a settlement where travel or residency restrictions are applied so that specific authorization is required to visit or remain overnight. They may be sensitive military establishments or secret research installations that require much more space or freedom than is available in a conventional military base. There may also be a wider variety of permanent residents including close family members of workers or trusted traders who are not directly connected with its clandestine purposes.

Many closed cities existed in the Soviet Union until its collapse in 1991. After 1991, a number of them still existed in the CIS countries, especially Russia. In modern Russia, such places are officially known as "closed administrative-territorial formations" (закрытые административно-территориальные образования, zakrytye administrativno-territorial'nye obrazovaniya, or ЗАТО ZATO for short).

🔗 Aviation

Bitching Betty is a slang term used by some pilots and aircrew (mainly North American), when referring to the voices used by some aircraft warning systems.

The enunciating voice, in at least some aircraft systems, may be either male or female and in some cases this may be selected according to pilot preference. If the voice is female, it may be referred to as Bitching Betty; if the voice is male, it may be referred to as Barking Bob. A female voice is heard on military aircraft such as the F-16 Fighting Falcon, the Eurofighter Typhoon and the Mikoyan MiG-29. A male voice is heard on Boeing commercial airliners and is also used in the BAE Hawk.

In the United Kingdom the term Nagging Nora is sometimes used, and in New Zealand the term used for Boeing aircraft is Hank the Yank. The voice warning system used on London Underground trains, which also uses a female voice, is known to some staff as Sonya, as it "gets on ya nerves".