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🔗 Mathematics 🔗 Game theory

The angel problem is a question in combinatorial game theory proposed by John Horton Conway. The game is commonly referred to as the Angels and Devils game. The game is played by two players called the angel and the devil. It is played on an infinite chessboard (or equivalently the points of a 2D lattice). The angel has a power k (a natural number 1 or higher), specified before the game starts. The board starts empty with the angel at the origin. On each turn, the angel jumps to a different empty square which could be reached by at most k moves of a chess king, i.e. the distance from the starting square is at most k in the infinity norm. The devil, on its turn, may add a block on any single square not containing the angel. The angel may leap over blocked squares, but cannot land on them. The devil wins if the angel is unable to move. The angel wins by surviving indefinitely.

The angel problem is: can an angel with high enough power win?

There must exist a winning strategy for one of the players. If the devil can force a win then it can do so in a finite number of moves. If the devil cannot force a win then there is always an action that the angel can take to avoid losing and a winning strategy for it is always to pick such a move. More abstractly, the "pay-off set" (i.e., the set of all plays in which the angel wins) is a closed set (in the natural topology on the set of all plays), and it is known that such games are determined. Of course, for any infinite game, if player 2 doesn't have a winning strategy, player 1 can always pick a move that leads to a position where player 2 doesn't have a winning strategy, but in some games, simply playing forever doesn't confer a win to player 1, and that's why undetermined games may exist.

Conway offered a reward for a general solution to this problem ($100 for a winning strategy for an angel of sufficiently high power, and $1000 for a proof that the devil can win irrespective of the angel's power). Progress was made first in higher dimensions. In late 2006, the original problem was solved when independent proofs appeared, showing that an angel can win. Bowditch proved that a 4-angel (that is, an angel with power k=4) can win and Máthé and Kloster gave proofs that a 2-angel can win. At this stage, it has not been confirmed by Conway who is to be the recipient of his prize offer, or whether each published and subsequent solution will also earn $100 US.

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Skepticism 🔗 Nevada 🔗 Paranormal 🔗 Aviation/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 (134 km) north-northwest of Las Vegas. The surrounding area is a popular tourist destination, including the small town of Rachel on the "Extraterrestrial Highway".

🔗 United States 🔗 Comedy 🔗 Politics 🔗 Politics/American politics 🔗 Journalism 🔗 Politics/Gun politics

"'No Way to Prevent This', Says Only Nation Where This Regularly Happens" is the title of a series of articles perennially published by the American news satire organization The Onion satirizing the frequency of mass shootings in the United States and the lack of action taken in the wake of such incidents.

Each article is about 200 words long, detailing the location of the shooting and the number of victims, but otherwise remaining essentially the same. A fictitious resident—usually of a state in which the shooting did not take place—is quoted as saying that the shooting was "a terrible tragedy", but "there's nothing anyone can do to stop them." The article ends by saying that the United States is the "only economically advanced nation in the world where roughly two mass shootings have occurred every month for the past eight years," and that Americans view themselves and the situation as "helpless".

🔗 Biography 🔗 Greater Manchester

Frederick Travis Dibnah, (29 April 1938 – 6 November 2004) was an English steeplejack and television personality, with a keen interest in mechanical engineering, who described himself as a "backstreet mechanic".

When Dibnah was born, Britain relied heavily upon coal to fuel its industry. As a child, he was fascinated by the steam engines which powered the many textile mills in Bolton, but he paid particular attention to chimneys and the men who worked on them. He began his working life as a joiner, before becoming a steeplejack. From age 22, he served for two years in the Army Catering Corps of the British Army, undertaking his National Service. Once demobilised, he returned to steeplejacking but met with limited success until he was asked to repair Bolton's parish church. The resulting publicity provided a boost to his business, ensuring he was almost never out of work.

In 1978, while making repairs to Bolton Town Hall, Dibnah was filmed by a regional BBC news crew. The BBC then commissioned a documentary, which followed the rough-hewn steeplejack as he worked on chimneys, interacted with his family and talked about his favourite hobby—steam. His Lanky manner and gentle, self-taught philosophical outlook proved popular with viewers and he featured in a number of television programmes. Toward the end of his life, the decline of Britain's industry was mirrored by a decline in his steeplejacking business and Dibnah increasingly came to rely on public appearances and after-dinner speaking to support his income. In 1998, he presented a programme on Britain's industrial history and went on to present a number of series, largely concerned with the Industrial Revolution and its mechanical and architectural legacy.

He died from bladder cancer in November 2004, aged 66.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Books 🔗 Business

War Is a Racket is a speech and a 1935 short book by Smedley D. Butler, a retired United States Marine Corps Major General and two-time Medal of Honor recipient. Based on his career military experience, Butler discusses how business interests commercially benefit from warfare. He had been appointed commanding officer of the Gendarmerie during the 1915–1934 United States occupation of Haiti.

After Butler retired from the US Marine Corps in October 1931, he made a nationwide tour in the early 1930s giving his speech "War Is a Racket". The speech was so well received that he wrote a longer version as a short book published in 1935. His work was condensed in Reader's Digest as a book supplement, which helped popularize his message. In an introduction to the Reader's Digest version, Lowell Thomas, who wrote Butler’s oral autobiography, praised Butler's "moral as well as physical courage".

🔗 Psychology

Learned helplessness is behavior exhibited by a subject after enduring repeated aversive stimuli beyond their control. It was initially thought to be caused from the subject's acceptance of their powerlessness: discontinuing attempts to escape or avoid the aversive stimulus, even when such alternatives are unambiguously presented. Upon exhibiting such behavior, the subject was said to have acquired learned helplessness. Over the past few decades, neuroscience has provided insight into learned helplessness and shown that the original theory actually had it backwards: the brain's default state is to assume that control is not present, and the presence of "helpfulness" is what is actually learned.

In humans, learned helplessness is related to the concept of self-efficacy; the individual's belief in their innate ability to achieve goals. Learned helplessness theory is the view that clinical depression and related mental illnesses may result from such real or perceived absence of control over the outcome of a situation.

🔗 Technology 🔗 Linguistics 🔗 Japan 🔗 Japan/Science and technology 🔗 Japan/CJKV

Mojibake (Japanese: 文字化け; IPA: [mod͡ʑibake]) is the garbled text that is the result of text being decoded using an unintended character encoding. The result is a systematic replacement of symbols with completely unrelated ones, often from a different writing system.

This display may include the generic replacement character ("�") in places where the binary representation is considered invalid. A replacement can also involve multiple consecutive symbols, as viewed in one encoding, when the same binary code constitutes one symbol in the other encoding. This is either because of differing constant length encoding (as in Asian 16-bit encodings vs European 8-bit encodings), or the use of variable length encodings (notably UTF-8 and UTF-16).

Failed rendering of glyphs due to either missing fonts or missing glyphs in a font is a different issue that is not to be confused with mojibake. Symptoms of this failed rendering include blocks with the code point displayed in hexadecimal or using the generic replacement character. Importantly, these replacements are valid and are the result of correct error handling by the software.

🔗 Computer science

The Q notation is a succinct way to specify the parameters of a binary fixed point number format. A number of other notations have been used for the same purpose.

🔗 Computing 🔗 Computing/Software

The Pick operating system (often called just "the Pick system" or simply "Pick") is a demand-paged, multiuser, virtual memory, time-sharing computer operating system based around a unique MultiValue database. Pick is used primarily for business data processing. It is named after one of its developers, Dick Pick.

The term "Pick system" has also come to be used as the general name of all operating environments which employ this multivalued database and have some implementation of Pick/BASIC and ENGLISH/Access queries. Although Pick started on a variety of minicomputers, the system and its various implementations eventually spread to a large assortment of microcomputers, personal computers and mainframe computers.

🔗 Iran 🔗 Alternative Views 🔗 Iraq

The Baghdad Battery or Parthian Battery is a set of three artifacts which were found together: a ceramic pot, a tube of copper, and a rod of iron. It was discovered in modern Khujut Rabu, Iraq, close to the metropolis of Ctesiphon, the capital of the Parthian (150 BC – 223 AD) and Sasanian (224–650 AD) empires of Persia, and it is considered to date from either of these periods.

Its origin and purpose remain unclear. It was hypothesized by some researchers that the object functioned as a galvanic cell, possibly used for electroplating, or some kind of electrotherapy, but there is no electroplated object known from this period. An alternative explanation is that it functioned as a storage vessel for sacred scrolls.