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🔗 Biology 🔗 Palaeontology 🔗 Geology

The Boring Billion, otherwise known as the Mid Proterozoic and Earth's Middle Ages, is the time period between 1.8 and 0.8 billion years ago (Ga) spanning the middle Proterozoic eon, characterized by more or less tectonic stability, climatic stasis, and slow biological evolution. It is bordered by two different oxygenation and glacial events, but the Boring Billion itself had very low oxygen levels and no evidence of glaciation.

The oceans may have been oxygen- and nutrient-poor and sulfidic (euxinia), populated by mainly anoxygenic purple bacteria, a type of chlorophyll-based photosynthetic bacteria which uses hydrogen sulfide (H₂S) instead of water and produces sulfur instead of oxygen. This is known as a Canfield ocean. Such composition may have caused the oceans to be black- and milky-turquoise instead of blue. (By contrast, during the much earlier Purple Earth phase the photosynthesis was retinal-based.)

Despite such adverse conditions, eukaryotes may have evolved around the beginning of the Boring Billion, and adopted several novel adaptations, such as various organelles, multicellularity, and possibly sexual reproduction, and diversified into plants, animals, and fungi at the end of this time interval. Such advances may have been important precursors to the evolution of large, complex life later in the Ediacaran and Phanerozoic. Nonetheless, prokaryotic cyanobacteria were the dominant lifeforms during this time, and likely supported an energy-poor food-web with a small number of protists at the apex level. The land was likely inhabited by prokaryotic cyanobacteria and eukaryotic proto-lichens, the latter more successful here probably due to the greater availability of nutrients than in offshore ocean waters.

🔗 Internet culture 🔗 Games

Wikiracing is a game using the online encyclopedia Wikipedia which focuses on traversing links from one page to another. It has many different variations and names, including The Wikipedia Game, Wikipedia Maze, Wikispeedia, Wikiwars, Wikipedia Ball, and Litner Ball. External websites have been created to facilitate the game.

The Seattle Times has recommended it as a good educational pastime for children and the Larchmont Gazette has said, "While I don't know any teenagers who would curl up with an encyclopedia for a good read, I hear that a lot are reading it in the process of playing the Wikipedia Game".

The Amazing Wiki Race has been an event at the TechOlympics and the Yale Freshman Olympics.

The average number of links separating any Wikipedia page from the United Kingdom page is 3.67. Other common houserules such as not using the United States page increase the difficulty of the game.

As of July 2019, a website and game known as The Wiki Game has been created, allowing players to Wikirace against each other in a server, for more points and recognition on the server. The game reached more recognition as Internet stars such as Game Grumps played it on their channels. There is a version on the App Store as well, in which players can do a variety of Wikirace styles from their phone.

🔗 Architecture 🔗 Classical Greece and Rome

The Roman architectural revolution, also known as the concrete revolution, is the name sometimes given to the widespread use in Roman architecture of the previously little-used architectural forms of the arch, vault, and dome. For the first time in history, their potential was fully exploited in the construction of a wide range of civil engineering structures, public buildings, and military facilities. These included amphitheatres, aqueducts, baths, bridges, circuses, dams, roads, and temples.

A crucial factor in this development that saw a trend to monumental architecture was the invention of Roman concrete (also called opus caementicium), which led to the liberation of the shape from the dictate of the traditional materials of stone and brick.

For the first time in recorded history we find evidence of an interest in the shapes of the space contained strong enough to outweigh the functional logic of the masonry masses that contained it. There was nothing new in the employment of curvilinear or polygonal forms, as such...But in so far as such buildings incorporated curvilinear or polygonal rooms and corridors, the shapes of these were determined by the form of the building as a whole, not by any aesthetic principle.

The development of Roman architecture, however, did not remain limited to these new forms and materials. An unrelated process of architectural innovation continued unabated, which, although less conspicuous, proved their usefulness for solving structural problems and found their way permanently into Western architecture, such as the lintel arch, the independent corbel, and the metal-tie.

During the Age of Augustus, almost the entire city of Rome was rebuilt causing an influx of craftsman and architects from all across Europe. Emperor Augustus aimed to develop new ideas in the construction of his buildings that would forever defy the limits that were ever thought possible. The Mausoleum in Campus Martius was one of the major monuments built by Augustus during his reign that was made almost entirely of concrete using updated construction techniques. The concrete is used in concentric rings that support the structure of the building like walls. The Theatre of Marcellus was another concrete triumph completed during the Age of Augustus, dedicated to the nephew of the emperor. The brick-faced concrete structure construction started under Julius Caesar but was completed under Augustus. It was this building that shows the integration of new concrete building techniques of Augustus's architects as opposed to those of Caesar. The Theatre of Marcellus uses a variety of materials that aid in the growth of the concrete revolution using readily available volcanic stones such as Tuscolo tuff and Tufo Lionato as aggregates in pozzolanic concretes.

These newly concocted recipes for concrete provided durability to walls and barrelled vaults as well as a unique aesthetic appeal. The integrated stone and masonry design illustrate a refinement that came with the concrete revolution as a result of the new techniques and styles developed under Augustus. The craftsmanship of the Theatre Marcellus demonstrated a skilled employment as well as rigorous technical supervision.

🔗 Etymology 🔗 Holidays 🔗 Scotland

Hogmanay ( HOG-mə-nay, -⁠NAY, Scots: [ˌhɔɡməˈneː]) is the Scots word for the last day of the old year and is synonymous with the celebration of the New Year in the Scottish manner. It is normally followed by further celebration on the morning of New Year's Day (1 January) or in some cases, 2 January—a Scottish bank holiday.

The origins of Hogmanay are unclear, but it may be derived from Norse and Gaelic observances of the winter solstice. Customs vary throughout Scotland, and usually include gift-giving and visiting the homes of friends and neighbours, with special attention given to the first-foot, the first guest of the new year.

🔗 Glass 🔗 Photography

The Nikon F-mount is a type of interchangeable lens mount developed by Nikon for its 35mm format single-lens reflex cameras. The F-mount was first introduced on the Nikon F camera in 1959, and features a three-lug bayonet mount with a 44 mm throat and a flange to focal plane distance of 46.5 mm. The company continues, with the 2020 D6 model, to use variations of the same lens mount specification for its film and digital SLR cameras.

🔗 Mathematics

Bellman's lost-in-a-forest problem is an unsolved minimization problem in geometry, originating in 1955 by the American applied mathematician Richard E. Bellman. The problem is often stated as follows: "A hiker is lost in a forest whose shape and dimensions are precisely known to him. What is the best path for him to follow to escape from the forest?" It is usually assumed that the hiker does not know the starting point or direction he is facing. The best path is taken to be the one that minimizes the worst-case distance to travel before reaching the edge of the forest. Other variations of the problem have been studied.

A proven solution is only known for a few shapes or classes of shape. A general solution would be in the form of a geometric algorithm which takes the shape of the forest as input and returns the optimal escape path as the output. Although real world applications are not apparent, the problem falls into a class of geometric optimization problems including search strategies that are of practical importance. A bigger motivation for study has been the connection to Moser's worm problem. It was included in a list of 12 problems described by the mathematician Scott W. Williams as "million buck problems" because he believed that the techniques involved in their resolution will be worth at least a million dollars to mathematics.

🔗 Computing 🔗 Time 🔗 Linux

Unix time (also known as Epoch time, POSIX time, seconds since the Epoch, or UNIX Epoch time) is a system for describing a point in time. It is the number of seconds that have elapsed since the Unix epoch, that is the time 00:00:00 UTC on 1 January 1970, minus leap seconds. Leap seconds are ignored, with a leap second having the same Unix time as the second before it, and every day is treated as if it contains exactly 86400 seconds. Due to this treatment, Unix time is not a true representation of UTC.

Unix time is widely used in operating systems and file formats. In Unix-like operating systems, date is a command which will print or set the current time; by default, it prints or sets the time in the system time zone, but with the -u flag, it prints or sets the time in UTC and, with the TZ environment variable set to refer to a particular time zone, prints or sets the time in that time zone.

🔗 Biology 🔗 Engineering 🔗 Science

Xenobots, named after the African clawed frog (Xenopus laevis), are synthetic organisms that are automatically designed by computers to perform some desired function and built by combining together different biological tissues.

Xenobots are less than a 1 millimeter (0.039 inches) wide and composed of just two things: skin cells and heart muscle cells, both of which are derived from stem cells harvested from early (blastula stage) frog embryos. The skin cells provide rigid support and the heart cells act as small motors, contracting and expanding in volume to propel the xenobot forward. The shape of a xenobot's body, and its distribution of skin and heart cells, are automatically designed in simulation to perform a specific task, using a process of trial and error (an evolutionary algorithm). Xenobots have been designed to walk, swim, push pellets, carry payloads, and work together in a swarm to aggregate debris scattered along the surface of their dish into neat piles. They can survive for weeks without food and heal themselves after lacerations.

🔗 Military history 🔗 Military history/Fortifications 🔗 Military history/Cold War 🔗 Military history/Balkan military history 🔗 Albania 🔗 Military history/European military history

Concrete military bunkers are a ubiquitous sight in Albania, with an average of 5.7 bunkers for every square kilometer (14.7 per square mile). The bunkers (Albanian: bunkerët) were built during the Hoxhaist government led by the Leader Enver Hoxha from the 1960s to the 1980s, as the government fortified Albania by building more than 750,000 bunkers.

Hoxha's program of "bunkerization" (bunkerizimi) resulted in the construction of bunkers in every corner of the then-People's Socialist Republic of Albania, ranging from mountain passes to city streets. They were never used for their intended purpose during the years that Hoxha governed. The cost of constructing them was a drain on Albania's resources, diverting them away from dealing with the country's housing shortage and poor roads.

The bunkers were abandoned following the dissolution of the communist government in 1992. A few were used in the Insurrection of 1997 and the Kosovo War of 1999. Most are now derelict, though some have been reused for a variety of purposes, including residential accommodation, cafés, storehouses, and shelters for animals or the homeless.