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Plan 9 from Bell Labs is a distributed operating system, originating in the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s, and building on UNIX concepts first developed there in the late 1960s. The final official release was in early 2015.

Under Plan 9, UNIX's everything is a file metaphor is extended via a pervasive network-centric filesystem, and graphical user interface is assumed as a basis for almost all functionality, though it retains a heavily text-centric ideology.

The name Plan 9 from Bell Labs is a reference to the Ed Wood 1959 cult science fiction Z-movie Plan 9 from Outer Space. The name of the project's mascot is "Glenda, the Plan 9 Bunny". The system continues to be used and developed by operating system researchers and hobbyists.

In cryptography, nothing-up-my-sleeve numbers are any numbers which, by their construction, are above suspicion of hidden properties. They are used in creating cryptographic functions such as hashes and ciphers. These algorithms often need randomized constants for mixing or initialization purposes. The cryptographer may wish to pick these values in a way that demonstrates the constants were not selected for a nefarious purpose, for example, to create a backdoor to the algorithm. These fears can be allayed by using numbers created in a way that leaves little room for adjustment. An example would be the use of initial digits from the number π as the constants. Using digits of π millions of places after the decimal point would not be considered trustworthy because the algorithm designer might have selected that starting point because it created a secret weakness the designer could later exploit—though even with natural-seeming selections, enough entropy exists in the possible choices that the utility of these numbers has been questioned.

Digits in the positional representations of real numbers such as π, e, and irrational roots are believed to appear with equal frequency (see normal number). Such numbers can be viewed as the opposite extreme of Chaitin–Kolmogorov random numbers in that they appear random but have very low information entropy. Their use is motivated by early controversy over the U.S. Government's 1975 Data Encryption Standard, which came under criticism because no explanation was supplied for the constants used in its S-box (though they were later found to have been carefully selected to protect against the then-classified technique of differential cryptanalysis). Thus a need was felt for a more transparent way to generate constants used in cryptography.

"Nothing up my sleeve" is a phrase associated with magicians, who sometimes preface a magic trick by holding open their sleeves to show they have no objects hidden inside.

Taqi al-Din Muhammad ibn Ma'ruf ash-Shami al-Asadi (Arabic: تقي الدين محمد بن معروف الشامي‎, Ottoman Turkish: تقي الدين محمد بن معروف الشامي السعدي‎, Turkish: Takiyüddin) (1526-1585) was an Ottoman polymath active in Cairo and Istanbul. He was the author of more than ninety books on a wide variety of subjects, including astronomy, clocks, engineering, mathematics, mechanics, optics and natural philosophy.

In 1574 the Ottoman Sultan Murad III invited Taqī ad-Dīn to build the Constantinople observatory. Using his exceptional knowledge in the mechanical arts, Taqī ad-Dīn constructed instruments like huge armillary and mechanical clocks that he used in his observations of the Great Comet of 1577. He also used European celestial and terrestrial globes that were delivered to Istanbul in gift-exchange.

The major work that resulted from his work in the observatory is titled "The tree of ultimate knowledge [in the end of time or the world] in the Kingdom of the Revolving Spheres: The astronomical tables of the King of Kings [Murād III]" (Sidrat al-muntah al-afkar fi malkūt al-falak al-dawār– al-zij al-Shāhinshāhi). The work was prepared according to the results of the observations carried out in Egypt and Istanbul in order to correct and complete Ulugh Beg's Zij as-Sultani. The first 40 pages of the work deal with calculations, followed by discussions of astronomical clocks, heavenly circles, and information about three eclipses which he observed at Cairo and Istanbul. For corroborating data of other observations of eclipses in other locales like Daud ar-Riyyadi (David the Mathematician), David Ben-Shushan of Salonika.

As a polymath, Taqī al-Dīn wrote numerous books on astronomy, mathematics, mechanics, and theology. His method of finding coordinates of stars were reportedly so precise that he got better measurements than his contemporaries, Tycho Brahe and Nicolas Copernicus. Brahe is also thought to have been aware of al-Dīn's work.

Taqī Ad-Dīn also described a steam turbine with the practical application of rotating a spit in 1551. He worked on and created astronomical clocks for his observatory. Taqī Ad-Dīn also wrote a book on optics, in which he determined the light emitted from objects, proved the Law of Reflection observationally, and worked on refraction.

Malbolge () is a public domain esoteric programming language invented by Ben Olmstead in 1998, named after the eighth circle of hell in Dante's Inferno, the Malebolge.

Malbolge was specifically designed to be almost impossible to use, via a counter-intuitive 'crazy operation', base-three arithmetic, and self-altering code. It builds on the difficulty of earlier, challenging esoteric languages (such as Brainfuck and Befunge), but takes this aspect to the extreme, playing on the entangled histories of computer science and encryption. Despite this design, it is possible (though very difficult) to write useful Malbolge programs.

In utility-scale electricity generation, the duck curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and renewable energy production. The term was coined in 2012 by the California Independent System Operator.

"The Complexity of Songs" is a journal article published by computer scientist Donald Knuth in 1977, as an in-joke about computational complexity theory. The article capitalizes on the tendency of popular songs to devolve from long and content-rich ballads to highly repetitive texts with little or no meaningful content. The article notes that a song of length N words may be produced remembering, e.g., only O(log N) words ("space complexity" of the song).

In finance, the rule of 72, the rule of 70 and the rule of 69.3 are methods for estimating an investment's doubling time. The rule number (e.g., 72) is divided by the interest percentage per period (usually years) to obtain the approximate number of periods required for doubling. Although scientific calculators and spreadsheet programs have functions to find the accurate doubling time, the rules are useful for mental calculations and when only a basic calculator is available.

These rules apply to exponential growth and are therefore used for compound interest as opposed to simple interest calculations. They can also be used for decay to obtain a halving time. The choice of number is mostly a matter of preference: 69 is more accurate for continuous compounding, while 72 works well in common interest situations and is more easily divisible. There is a number of variations to the rules that improve accuracy. For periodic compounding, the exact doubling time for an interest rate of r percent per period is

${\displaystyle t={\frac {\ln(2)}{\ln(1+r/100)}}\approx {\frac {72}{r}}}$,

where t is the number of periods required. The formula above can be used for more than calculating the doubling time. If one wants to know the tripling time, for example, replace the constant 2 in the numerator with 3. As another example, if one wants to know the number of periods it takes for the initial value to rise by 50%, replace the constant 2 with 1.5.

Soundies are three-minute American musical films, produced between 1940 and 1947, each displaying a song, dance, and/or band or orchestral number. Produced professionally on 35 mm black-and-white film, like theatrical motion pictures, they were printed on the more portable and economical 16 mm film.

The films were shown in a coin-operated "movie jukebox" named the Panoram, manufactured by the Mills Novelty Company of Chicago. Each Panoram housed a 16 mm RCA film projector, with eight Soundies films threaded in an endless-loop arrangement. A system of mirrors flashed the image from the lower half of the cabinet onto a front-facing screen in the top half. Each film cost 10 cents to play, with no choice of song; the patron saw whatever film was next in the queue. Panorams could be found in public amusement centers, nightclubs, taverns, restaurants, and factory lounges, and the films were changed weekly. The completed Soundies were generally made available within a few weeks of their filming, by the Soundies Distributing Corporation of America.

Several production companies filmed the Soundies shorts in New York City, Hollywood, and Chicago: James Roosevelt's Globe Productions (1940–41), Cinemasters (1940–41), Minoco Productions (owned by Mills Novelty, 1941–43), RCM Productions (1941–46), LOL Productions (1943), Glamourettes (1943), Filmcraft Productions (1943–46), and Alexander Productions (1946) led by William D. Alexander). The performers recorded the music in advance, and mimed to the soundtrack during filming.

The movie-jukebox idea developed several imitations and variations of the technical design; the most successful of these imitators were the Techniprocess company (managed by Rudy Vallee) and the Featurettes company, which used original novelty songs and usually unknown talent (17-year-old Gwen Verdon appears in a couple of the Featurettes as "Gwen Verdun"). As Soundies quickly gained most of the market for jukebox films, the other companies disbanded, and some sold their films to the Soundies concern.

Museum fatigue is a state of physical or mental fatigue caused by the experience of exhibits in museums and similar cultural institutions. The collection of phenomena that characterize museum fatigue was first described in 1916, and has since received widespread attention in popular and scientific contexts.

The first known description of museum fatigue was made by Benjamin Ives Gilman in the January 1916 edition of The Scientific Monthly. Gilman mainly focused on the efforts of museum fatigue on how the viewing displays are placed. Gilman went on to say that the way the displays were presented caused museum fatigue. In other later studies, Edward Robinson in 1928 spoke more about museum fatigue, specifically of four museums that showed a lot of characteristics of museum fatigue because of how the displays were placed. Arthur Melton provided more proof for Robinson by observing visitors' interest in the displays decreased as the number of displays increased.

In a more recent study of the phenomenon, Falk, Koran, Direking, and Dreblow studied museum fatigue at the Florida Museum of Natural History in 1985. While observing visitors they noticed a pattern of high interest in anything in the museum for about 30 minutes and then a decrease in interest. In 1997–1998, Beverly Serrell in her research determined that in less than 20 minutes people became apathetic towards the museum. Museum fatigue has also been applied in zoos to see if they had the same effect. In one study in 1986, Bitgood, Patterson, and Benefeld observed the reptile house of the Birmingham Zoo. While observing they noticed that the pattern was different from museum fatigue.

"The Gods of the Copybook Headings" is a poem by Rudyard Kipling, characterized by biographer Sir David Gilmour as one of several "ferocious post-war eruptions" of Kipling's souring sentiment concerning the state of Anglo-European society. It was first published in the Sunday Pictorial of London on 26 October 1919; in America, it was published as "The Gods of the Copybook Maxims" in Harper's Magazine in January 1920.

In the poem, Kipling's narrator counterposes the "Gods" of the title, who embody eternal truths, against "the Gods of the Market-Place", who represent an optimistic self-deception into which it supposes society has fallen in the early 20th century.

The "copybook headings" to which the title refers were proverbs or maxims, often drawn from sermons and scripture extolling virtue and wisdom, that were printed at the top of the pages of copybooks, special notebooks used by 19th-century British schoolchildren. The students had to copy the maxims repeatedly, by hand, down the page. The exercise was thought to serve simultaneously as a form of moral education and penmanship practice.