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🔗 Physics 🔗 Meteorology 🔗 Radio

A whistler is a very low frequency or VLF electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with a maximum amplitude usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes (mostly intracloud and return-path) where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. The study of whistlers categorizes them into Pure Note, Diffuse, 2-Hop, and Echo Train types.

Voyager 1 and 2 spacecraft detected whistler-like activity in the vicinity of Jupiter known as "Jovian Whistlers", implying the presence of lightning there.

🔗 United States 🔗 International relations 🔗 Politics 🔗 Cold War

The Doomsday Clock is a symbol that represents the likelihood of a man-made global catastrophe. Maintained since 1947 by the members of the Bulletin of the Atomic Scientists, the Clock is a metaphor for threats to humanity from unchecked scientific and technical advances. The Clock represents the hypothetical global catastrophe as "midnight" and the Bulletin's opinion on how close the world is to a global catastrophe as a number of "minutes" to midnight, assessed in January of each year. The main factors influencing the Clock are nuclear risk and global warming (climate change). The Bulletin's Science and Security Board also monitors new developments in the life sciences and technology that could inflict irrevocable harm to humanity.

The Clock's original setting in 1947 was seven minutes to midnight. It has been set backward and forward 24 times since then, the largest-ever number of minutes to midnight being 17 (in 1991), and the smallest 100 seconds (1 minute and 40 seconds) in January 2020.

The clock was set at two minutes to midnight in January 2018, and left unchanged in 2019 due to the twin threats of nuclear weapons and the increasing effects of global warming. On 23 January 2020, it was moved forward to 100 seconds (1 minute 40 seconds) before midnight, based on the increased threats to global stability posed by "a nuclear blunder", exacerbated by the rate of climate change.

🔗 New Zealand 🔗 India 🔗 India/Tamil Nadu 🔗 Dravidian civilizations 🔗 New Zealand/Māori 🔗 Tamil civilization

The Tamil Bell is a broken bronze bell discovered in approximately 1836 by missionary William Colenso. It was being used as a pot to boil potatoes by Māori women near Whangarei in the Northland Region of New Zealand.

The bell is 13 cm long and 9 cm deep, and has an inscription. The inscription running around the rim of the bell has been identified as old Tamil. Translated, it says "Mohoyiden Buks ship’s bell". Some of the characters in the inscription are of an archaic form no longer seen in modern Tamil script, thus suggesting that the bell could be about 500 years old, possibly from the Later Pandya period. It is thus what is sometimes called an out-of-place artefact.

Indologist V. R. Ramachandra Dikshitar states in his The Origin and Spread of the Tamils that ancient Tamil sea-farers might have had a knowledge of Australia and Polynesia. The discovery of the bell has led to speculation about a possible Tamil presence in New Zealand, but the bell is not in itself proof of early Tamil contact with New Zealand'. Seafarers from Trincomalee may have reached New Zealand during the period of increased trade between the Vanni country and South East Asia. The bell might have been dropped off the shore by a Portuguese ship, whose sailors had been in touch with the Indians. Also, a number of Indian vessels had been captured by the Europeans during the period; thus, another possibility is that the bell might have belonged to such a wrecked vessel, cast away on the New Zealand shores.

The bell was bequeathed by William Colenso to the Dominion Museum – now the Museum of New Zealand Te Papa Tongarewa.

🔗 Mathematics 🔗 Statistics

In probability theory and intertemporal portfolio choice, the Kelly criterion (or Kelly strategy or Kelly bet), also known as the scientific gambling method, is a formula for bet sizing that leads almost surely to higher wealth compared to any other strategy in the long run (i.e. approaching the limit as the number of bets goes to infinity). The Kelly bet size is found by maximizing the expected value of the logarithm of wealth, which is equivalent to maximizing the expected geometric growth rate. The Kelly Criterion is to bet a predetermined fraction of assets, and it can seem counterintuitive. It was described by J. L. Kelly Jr, a researcher at Bell Labs, in 1956.

For an even money bet, the Kelly criterion computes the wager size percentage by multiplying the percent chance to win by two, then subtracting one-hundred percent. So, for a bet with a 70% chance to win the optimal wager size is 40% of available funds.

The practical use of the formula has been demonstrated for gambling and the same idea was used to explain diversification in investment management. In the 2000s, Kelly-style analysis became a part of mainstream investment theory and the claim has been made that well-known successful investors including Warren Buffett and Bill Gross use Kelly methods. William Poundstone wrote an extensive popular account of the history of Kelly betting.

🔗 Writing systems 🔗 Typography

The long s (ſ) is an archaic form of the lower case letter s. It replaced the single s, or the first s in a double s (e.g. "ſinfulneſs" for "sinfulness" and "ſucceſs" for "success"). The long s is the basis of the first half of the grapheme or the German alphabet ligature letter ß, which is known as the Eszett. The modern letterform is known as the short, terminal, or round s.

🔗 Computing

In computer science, dancing links is a technique for reverting the operation of deleting a node from a circular doubly linked list. It is particularly useful for efficiently implementing backtracking algorithms, such as Donald Knuth's Algorithm X for the exact cover problem. Algorithm X is a recursive, nondeterministic, depth-first, backtracking algorithm that finds all solutions to the exact cover problem. Some of the better-known exact cover problems include tiling, the n queens problem, and Sudoku.

The name dancing links, which was suggested by Donald Knuth, stems from the way the algorithm works, as iterations of the algorithm cause the links to "dance" with partner links so as to resemble an "exquisitely choreographed dance." Knuth credits Hiroshi Hitotsumatsu and Kōhei Noshita with having invented the idea in 1979, but it is his paper which has popularized it.

🔗 Physics 🔗 Weather 🔗 Weather/Weather 🔗 Weather/General meteorology

A Fata Morgana (Italian: [ˈfaːta morˈɡaːna]) is a complex form of superior mirage visible in a narrow band right above the horizon. The term Fata Morgana is the Italian translation of "Morgan the Fairy" (Morgan le Fay of Arthurian legend). These mirages are often seen in the Italian Strait of Messina, and were described as fairy castles in the air or false land conjured by her magic.

Fata Morgana mirages significantly distort the object or objects on which they are based, often such that the object is completely unrecognizable. A Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant object, including boats, islands, and the coastline. Often, a Fata Morgana changes rapidly. The mirage comprises several inverted (upside down) and upright images stacked on top of one another. Fata Morgana mirages also show alternating compressed and stretched zones.

The optical phenomenon occurs because rays of light bend when they pass through air layers of different temperatures in a steep thermal inversion where an atmospheric duct has formed. In calm weather, a layer of significantly warmer air may rest over colder dense air, forming an atmospheric duct that acts like a refracting lens, producing a series of both inverted and erect images. A Fata Morgana requires a duct to be present; thermal inversion alone is not enough to produce this kind of mirage. While a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion.

🔗 Video games 🔗 Horror

Doom is a first-person shooter game developed and published by id Software. Released on December 10, 1993, for DOS, it is the first installment in the Doom franchise. The player assumes the role of a space marine, later unofficially referred to as Doomguy, fighting through hordes of undead humans and invading demons. The game begins on the moons of Mars and finishes in hell, with the player traversing each level to find its exit or defeat its final boss. It is an early example of 3D graphics in video games, and has enemies and objects as 2D images, a technique sometimes referred to as 2.5D graphics.

Doom was the third major independent release by id Software, after Commander Keen (1990–1991) and Wolfenstein 3D (1992). In May 1992, id started developing a darker game focused on fighting demons with technology, using a new 3D game engine from the lead programmer, John Carmack. The designer Tom Hall initially wrote a science fiction plot, but he and most of the story were removed from the project, with the final game featuring an action-heavy design by John Romero and Sandy Petersen. Id published Doom as a set of three episodes under the shareware model, marketing the full game by releasing the first episode free. A retail version with an additional episode was published in 1995 by GT Interactive as The Ultimate Doom.

Doom was a critical and commercial success, earning a reputation as one of the best and most influential video games of all time. It sold an estimated 3.5 million copies by 1999, and up to 20 million people are estimated to have played it within two years of launch. It has been termed the "father" of first-person shooters and is regarded as one of the most important games in the genre. It has been cited by video game historians as shifting the direction and public perception of the medium as a whole, as well as sparking the rise of online games and communities. It led to an array of imitators and clones, as well as a robust modding scene and the birth of speedrunning as a community. Its high level of graphic violence led to controversy from a range of groups. Doom has been ported to a variety of platforms both officially and unofficially and has been followed by several games in the series, including Doom II (1994), Doom 3 (2004), Doom (2016), and Doom Eternal (2020), as well as the films Doom (2005) and Doom: Annihilation (2019).

🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Software

Compute Express Link (CXL) is an open standard for high-speed central processing unit (CPU)-to-device and CPU-to-memory connections, designed for high performance data center computers. CXL is built on the PCI Express (PCIe) physical and electrical interface and includes PCIe-based block input/output protocol (CXL.io) and new cache-coherent protocols for accessing system memory (CXL.cache) and device memory (CXL.mem).