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🔗 Technology 🔗 Physics

The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion.

The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel (driven wheel) that advances it by one step at a time. The drive wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.

🔗 Typography 🔗 Primates

🔗 Economics 🔗 Business 🔗 Sociology 🔗 Occupations

This is a category of jobs that have been rendered obsolete due to advances in technology and/or social conditions.

🔗 Archaeology 🔗 Cities 🔗 Dacia

This is a list of present-day cities by the time period over which they have been continuously inhabited as a city. The age claims listed are generally disputed. Differences in opinion can result from different definitions of "city" as well as "continuous habitation" and historical evidence is often disputed. Caveats (and sources) to the validity of each claim are discussed in the "Notes" column.

🔗 United States 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Canada 🔗 Agriculture 🔗 Canada/British Columbia 🔗 United States/Washington 🔗 Canada/Geography of Canada 🔗 Military history/European military history 🔗 Military history/British military history 🔗 Agriculture/Livestock

The Pig War was a confrontation in 1859 between the United States and United Kingdom over the British–U.S. border in the San Juan Islands, between Vancouver Island (present-day Canada) and the State of Washington. The Pig War, so called because it was triggered by the shooting of a pig, is also called the Pig Episode, the Pig and Potato War, the San Juan Boundary Dispute and the Northwestern Boundary Dispute. Aside from the death of one pig, this dispute was a bloodless conflict.

🔗 Computer science

TLA⁺ is a formal specification language developed by Leslie Lamport. It is used to design, model, document, and verify programs, especially concurrent systems and distributed systems. TLA⁺ has been described as exhaustively-testable pseudocode, and its use likened to drawing blueprints for software systems; TLA is an acronym for Temporal Logic of Actions.

For design and documentation, TLA⁺ fulfills the same purpose as informal technical specifications. However, TLA⁺ specifications are written in a formal language of logic and mathematics, and the precision of specifications written in this language is intended to uncover design flaws before system implementation is underway.

Since TLA⁺ specifications are written in a formal language, they are amenable to finite model checking. The model checker finds all possible system behaviours up to some number of execution steps, and examines them for violations of desired invariance properties such as safety and liveness. TLA⁺ specifications use basic set theory to define safety (bad things won't happen) and temporal logic to define liveness (good things eventually happen).

TLA⁺ is also used to write machine-checked proofs of correctness both for algorithms and mathematical theorems. The proofs are written in a declarative, hierarchical style independent of any single theorem prover backend. Both formal and informal structured mathematical proofs can be written in TLA⁺; the language is similar to LaTeX, and tools exist to translate TLA⁺ specifications to LaTeX documents.

TLA⁺ was introduced in 1999, following several decades of research into a verification method for concurrent systems. A toolchain has since developed, including an IDE and distributed model checker. The pseudocode-like language PlusCal was created in 2009; it transpiles to TLA⁺ and is useful for specifying sequential algorithms. TLA⁺² was announced in 2014, expanding language support for proof constructs. The current TLA⁺ reference is The TLA⁺ Hyperbook by Leslie Lamport.

🔗 Books 🔗 Socialism 🔗 Anarchism

Bullshit Jobs: A Theory is a 2018 book by anthropologist David Graeber that argues the existence and societal harm of meaningless jobs. He contends that over half of societal work is pointless, which becomes psychologically destructive when paired with a work ethic that associates work with self-worth. Graeber describes five types of meaningless jobs, in which workers pretend their role is not as pointless or harmful as they know it to be: flunkies, goons, duct tapers, box tickers, and taskmasters. He argues that the association of labor with virtuous suffering is recent in human history, and proposes universal basic income as a potential solution.

The book is an extension of a popular essay Graeber published in 2013, which was later translated into 12 languages and whose underlying premise became the subject of a YouGov poll. Graeber subsequently solicited hundreds of testimonials of meaningless jobs and revised his case into a book that was published by Simon & Schuster in May 2018.

🔗 Mathematics

In mathematics, 0.999... (also written as 0.9, among other ways) denotes the repeating decimal consisting of infinitely many 9s after the decimal point (and one 0 before it). This repeating decimal represents the smallest number no less than every decimal number in the sequence (0.9, 0.99, 0.999, ...). This number is equal to 1. In other words, "0.999..." and "1" represent the same number. There are many ways of showing this equality, from intuitive arguments to mathematically rigorous proofs. The technique used depends on the target audience, background assumptions, historical context, and preferred development of the real numbers, the system within which 0.999... is commonly defined. (In other systems, 0.999... can have the same meaning, a different definition, or be undefined.)

More generally, every nonzero terminating decimal has two equal representations (for example, 8.32 and 8.31999...), which is a property of all base representations. The utilitarian preference for the terminating decimal representation contributes to the misconception that it is the only representation. For this and other reasons—such as rigorous proofs relying on non-elementary techniques, properties, or disciplines—some people can find the equality sufficiently counterintuitive that they question or reject it. This has been the subject of several studies in mathematics education.

🔗 Linguistics 🔗 Antarctica 🔗 Languages 🔗 English Language

Antarctic English is a variety of the English language spoken by people living on the continent of Antarctica and within the subantarctic islands.^: vii Spoken primarily by scientists and workers in the Antarctic tourism industry, it consists of various unique words and is spoken with a unique accent. During the 19th and 20th centuries, Antarctic English was influenced by Spanish-speaking South Americans and Northern European explorers who introduced new words that continue to be used today.