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🔗 Biography 🔗 Biography/science and academia 🔗 Trains 🔗 Trains/UK Railways 🔗 Mills 🔗 Trains/Transport in Scotland 🔗 North East England

George Stephenson (9 June 1781 – 12 August 1848) was an English civil engineer and mechanical engineer during the Industrial Revolution. Renowned as the "Father of Railways", Stephenson was considered by the Victorians as a great example of diligent application and thirst for improvement. His chosen rail gauge, sometimes called "Stephenson gauge", was the basis for the 4-foot-8+1⁄2-inch (1.435 m) standard gauge used by most of the world's railways.

Pioneered by Stephenson, rail transport was one of the most important technological inventions of the 19th century and a key component of the Industrial Revolution. Built by George and his son Robert's company Robert Stephenson and Company, the Locomotion No. 1 was the first steam locomotive to carry passengers on a public rail line, the Stockton and Darlington Railway in 1825. George also built the first public inter-city railway line in the world to use locomotives, the Liverpool and Manchester Railway, which opened in 1830.

🔗 Time

The Doomsday rule is an algorithm of determination of the day of the week for a given date. It provides a perpetual calendar because the Gregorian calendar moves in cycles of 400 years. The algorithm for mental calculation was devised by John Conway in 1973, drawing inspiration from Lewis Carroll's perpetual calendar algorithm. It takes advantage of each year having a certain day of the week, called the doomsday, upon which certain easy-to-remember dates fall; for example, 4/4, 6/6, 8/8, 10/10, 12/12, and the last day of February all occur on the same day of the week in any year. Applying the Doomsday algorithm involves three steps: Determination of the anchor day for the century, calculation of the doomsday for the year from the anchor day, and selection of the closest date out of those that always fall on the doomsday, e.g., 4/4 and 6/6, and count of the number of days (modulo 7) between that date and the date in question to arrive at the day of the week. The technique applies to both the Gregorian calendar and the Julian calendar, although their doomsdays are usually different days of the week.

The algorithm is simple enough that it can be computed mentally. Conway can usually give the correct answer in under two seconds. To improve his speed, he practices his calendrical calculations on his computer, which is programmed to quiz him with random dates every time he logs on.

🔗 Biography 🔗 Philosophy 🔗 Politics 🔗 Philosophy/Social and political philosophy 🔗 Biography/science and academia 🔗 Philosophy/Philosophers 🔗 India 🔗 Philosophy/Ancient philosophy 🔗 India/Bihar 🔗 Philosophy/Eastern philosophy 🔗 Hinduism 🔗 India/Indian history workgroup 🔗 India/Patna

Chanakya (IAST: Cāṇakya, pronunciation ) was an ancient Indian teacher, philosopher, economist, jurist and royal advisor. He is traditionally identified as Kauṭilya or Vishnugupta, who authored the ancient Indian political treatise, the Arthashastra, a text dated to roughly between the 3rd century BCE and the 3rd century CE. As such, he is considered the pioneer of the field of political science and economics in India, and his work is thought of as an important precursor to classical economics. His works were lost near the end of the Gupta Empire in the 6th century CE and not rediscovered until the early 20th century.

Chanakya assisted the first Mauryan emperor Chandragupta in his rise to power. He is widely credited for having played an important role in the establishment of the Maurya Empire. Chanakya served as the chief advisor to both emperors Chandragupta and his son Bindusara.

🔗 Books 🔗 Alternative Views 🔗 Chemistry 🔗 Psychoactive and Recreational Drugs

PiHKAL: A Chemical Love Story is a book by Dr. Alexander Shulgin and Ann Shulgin, published in 1991. The subject of the work is psychoactive phenethylamine chemical derivatives, notably those that act as psychedelics and/or empathogen-entactogens. The main title, PiHKAL, is an acronym that stands for "Phenethylamines I Have Known and Loved".

The book is arranged into two parts, the first part being a fictionalized autobiography of the couple and the second part describing 179 different psychedelic compounds (most of which Shulgin discovered himself), including detailed synthesis instructions, bioassays, dosages, and other commentary.

The second part was made freely available by Shulgin on Erowid while the first part is available only in the printed text. While the reactions described are beyond the ability of people with a basic chemistry education, some tend to emphasize techniques that do not require difficult-to-obtain chemicals. Notable among these are the use of mercury-aluminum amalgam (an unusual but easy to obtain reagent) as a reducing agent and detailed suggestions on legal plant sources of important drug precursors such as safrole.

🔗 Astronomy 🔗 Hawaii

Lāhainā Noon is a semi-annual tropical solar phenomenon when the Sun culminates at the zenith at solar noon, passing directly overhead (above the subsolar point). The term "lāhainā noon" was coined by the Bishop Museum in Hawaiʻi.

🔗 Evolutionary biology 🔗 Molecular Biology 🔗 Molecular Biology/Genetics

In evolutionary biology and population genetics, the error threshold (or critical mutation rate) is a limit on the number of base pairs a self-replicating molecule may have before mutation will destroy the information in subsequent generations of the molecule. The error threshold is crucial to understanding "Eigen's paradox".

The error threshold is a concept in the origins of life (abiogenesis), in particular of very early life, before the advent of DNA. It is postulated that the first self-replicating molecules might have been small ribozyme-like RNA molecules. These molecules consist of strings of base pairs or "digits", and their order is a code that directs how the molecule interacts with its environment. All replication is subject to mutation error. During the replication process, each digit has a certain probability of being replaced by some other digit, which changes the way the molecule interacts with its environment, and may increase or decrease its fitness, or ability to reproduce, in that environment.

🔗 Music theory

The Parsons code, formally named the Parsons code for melodic contours, is a simple notation used to identify a piece of music through melodic motion — movements of the pitch up and down. Denys Parsons developed this system for his 1975 book The Directory of Tunes and Musical Themes. Representing a melody in this manner makes it easier to index or search for pieces, particularly when the notes values are unknown.

The book was also published in Germany in 2002 and reprinted by Piatkus as The Directory of Classical Themes in 2008.

🔗 Computer science 🔗 Mathematics

In combinatory logic for computer science, a fixed-point combinator (or fixpoint combinator),^: p.26 is a higher-order function (i.e. a function which takes a function as argument) that returns some fixed point (a value that is mapped to itself) of its argument function, if one exists.

Formally, if ${\displaystyle {\textsf {fix}}}$ is a fixed-point combinator and the function ${\displaystyle f}$ has one or more fixed points, then ${\displaystyle {\textsf {fix}}\ f}$ is one of these fixed points, i.e.

${\displaystyle f\ ({\textsf {fix}}\ f)={\textsf {fix}}\ f\ .}$

Fixed-point combinators can be defined in the lambda calculus and in functional programming languages and provide a means to allow for recursive definitions.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Military history/Middle Eastern military history

Zamburak (Persian: زمبورک‎), literally meaning wasp, was a specialized form of self-propelled artillery from the early modern period, featuring small cannons fired from swivel-mounts on camels. The operator of a zamburak is known as a zamburakchi. The weapon was used by the gunpowder empires, especially the Iranian empires of the Safavid dynasty, Timurid Empire and Afsharid dynasty, due to the ruggedness of the Iranian Plateau, which made typical transportation of heavy cannons problematic.

The zamburak became a deadly weapon in the 18th century. The Pashtuns used it to deadly effect in the Battle of Gulnabad, routing a numerically superior imperial Safavid army. The zamburak was also used successfully in Nader's Campaigns, when the shah and military genius Nader Shah utilized a zamburak corps in conjunction with a regular artillery corps of conventional cannon to devastating effect in numerous battles such as at the Battle of Damghan (1729), the Battle of Yeghevārd, and the Battle of Karnal.

🔗 Linguistics 🔗 Linguistics/Applied Linguistics 🔗 Writing systems

The Shavian alphabet (also known as the Shaw alphabet) is an alphabet conceived as a way to provide simple, phonetic orthography for the English language to replace the difficulties of conventional spelling. It was posthumously funded by and named after Irish playwright Bernard Shaw. Shaw set three main criteria for the new alphabet: it should be (1) at least 40 letters; (2) as "phonetic" as possible (that is, letters should have a 1:1 correspondence to phonemes); and (3) distinct from the Latin alphabet to avoid the impression that the new spellings were simply "misspellings".