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Gray goo (also spelled grey goo) is a hypothetical global catastrophic scenario involving molecular nanotechnology in which out-of-control self-replicating machines consume all biomass on Earth while building more of themselves, a scenario that has been called ecophagy ("eating the environment", more literally "eating the habitation"). The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.

Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines or clanking replicators. The term gray goo was coined by nanotechnology pioneer K. Eric Drexler in his 1986 book Engines of Creation. In 2004 he stated, "I wish I had never used the term 'gray goo'." Engines of Creation mentions "gray goo" in two paragraphs and a note, while the popularized idea of gray goo was first publicized in a mass-circulation magazine, Omni, in November 1986.

Norton's dome is a thought experiment that exhibits a non-deterministic system within the bounds of Newtonian mechanics. It was devised by John D. Norton in 2003. It is a special limiting case of a more general class of examples from 1997 due to Sanjay Bhat and Dennis Bernstein. The Norton's dome problem can be regarded as a problem in physics, mathematics, or philosophy.

Lemon laws are United States state laws that provide a remedy for purchasers of cars and other consumer goods in order to compensate for products that repeatedly fail to meet standards of quality and performance. Although many types of products can be defective, the term "lemon" is mostly used to describe defective motor vehicles, such as cars, trucks, and motorcycles.

The Knights of the Lambda Calculus is a semi-fictional organization of expert Lisp and Scheme hackers. The name refers to the lambda calculus, a mathematical formalism invented by Alonzo Church, with which Lisp is intimately connected, and references the Knights Templar.

There is no actual organization that goes by the name Knights of the Lambda Calculus; it mostly only exists as a hacker culture in-joke. The concept most likely originated at MIT. For example, in the Structure and Interpretation of Computer Programs video lectures, Gerald Jay Sussman presents the audience with the button, saying they are now members of this special group. However, according to the Jargon File, a "well-known LISPer" has been known to give out buttons with Knights insignia on them, and some people have claimed to have membership in the Knights.

The man on the Clapham omnibus is a hypothetical ordinary and reasonable person, used by the courts in English law where it is necessary to decide whether a party has acted as a reasonable person would – for example, in a civil action for negligence. The character is a reasonably educated, intelligent but nondescript person, against whom the defendant's conduct can be measured.

The term was introduced into English law during the Victorian era, and is still an important concept in British law. It is also used in other Commonwealth common law jurisdictions, sometimes with suitable modifications to the phrase as an aid to local comprehension. The route of the original "Clapham omnibus" is unknown but London Buses route 88 was briefly branded as "the Clapham Omnibus" in the 1990s and is sometimes associated with the term.

The pneumatic tube mail was a postal system operating in New York City from 1897 to 1953 using pneumatic tubes. Similar systems had arisen in the mid-19th century in London, via the London Pneumatic Despatch Company; in Manchester and other British cities; and in Paris via the Paris pneumatic post. Following the creation of the first American pneumatic mail system in Philadelphia in 1893, New York City's system was begun, initially only between the old General Post Office on Park Row and the Produce Exchange on Bowling Green, a distance of 3,750 feet (1,140 m).

Eventually the network stretched up both sides of Manhattan Island all the way to Manhattanville on the West Side and "Triborough" in East Harlem, forming a loop running a few feet below street level. Travel time from the General Post Office to Harlem was 20 minutes. A crosstown line connected the two parallel lines between the new General Post Office on the West Side and Grand Central Terminal on the east, and took four minutes for mail to traverse. Using the Brooklyn Bridge, a spur line also ran from Church Street in lower Manhattan to the General Post Office in Brooklyn, taking four minutes. Operators of the system were called "Rocketeers".

Though 10 cities were funded for pneumatic mail, the New York operation was the most developed. By 1907 contracts were issued in five other cities (Boston, Brooklyn, Chicago, Philadelphia, St. Louis), but not in four cities (Baltimore, Cincinnati, Kansas City, San Francisco). The system was discontinued in 1953.

Taikyoku shōgi (Japanese: 大局将棋) lit. "ultimate chess" is the largest known variant of shogi (Japanese chess). The game was created around the mid-16th century (presumably by priests) and is based on earlier large board shogi games. Before the rediscovery of taikyoku shogi in 1997, tai shogi was believed to be the largest playable chess variant ever. It has not been shown that taikyoku shogi was ever widely played. There are only two sets of restored taikyoku shogi pieces and one of them is held at Osaka University of Commerce. One game may be played over several long sessions and require each player to make over a thousand moves.

Because the game was found only recently after centuries of obscurity, it is difficult to say exactly what all the rules were. Several documents describing the game have been found; however, there are differences between them. Many of the pieces appear in other shogi variants but their moves may be different. The board, and likewise the pieces, were made much smaller, making archeological finds difficult to decipher. Research into this game continues for historical and cultural reasons, but also to satisfy the curious and those who wish to play what could be the most challenging chess-like game ever made. More research must be done however. This article focuses on one likely set of rules that can make the game playable in modern times but is by no means canon. These rules may change as more discoveries are made and secrets of the game unlocked.

Further, because of the terse and often incomplete wording of the historical sources for the large shogi variants, except for chu shogi and to a lesser extent dai shogi (which were at some points of time the most prestigious forms of shogi being played), the historical rules of taikyoku shogi are not clear. Different sources often differ significantly in the moves attributed to the pieces, and the degree of contradiction (summarised below with the listing of most known alternative moves) is such that it is likely impossible to reconstruct the "true historical rules" with any degree of certainty, if there ever was such a thing. It is not clear if the game was ever played much historically, as there is no record of any sets having been made.

In computer science, the Knuth–Morris–Pratt string-searching algorithm (or KMP algorithm) searches for occurrences of a "word" W within a main "text string" S by employing the observation that when a mismatch occurs, the word itself embodies sufficient information to determine where the next match could begin, thus bypassing re-examination of previously matched characters.

The algorithm was conceived by James H. Morris and independently discovered by Donald Knuth "a few weeks later" from automata theory. Morris and Vaughan Pratt published a technical report in 1970. The three also published the algorithm jointly in 1977. Independently, in 1969, Matiyasevich discovered a similar algorithm, coded by a two-dimensional Turing machine, while studying a string-pattern-matching recognition problem over a binary alphabet. This was the first linear-time algorithm for string matching.

Balloonomania was a strong public interest or fad in balloons that originated in France in the late 18th century and continued into the 19th century, during the advent of balloon flights. The interest began with the first flights of the Montgolfier brothers in 1783 (in a balloon inflated with hot air). Soon afterwards Jacques Alexandre César Charles flew another type of balloon (inflated with hydrogen) and both types of balloon were in use from then on. The fad quickly spread in France and across the channel in England.