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🔗 Middle Ages 🔗 Middle Ages/History 🔗 Celts 🔗 Writing systems 🔗 Ireland 🔗 Medieval Scotland

Ogham (Modern Irish: [ˈoː(ə)mˠ]; Middle Irish: ogum, ogom, later ogam [ˈɔɣəmˠ]) is an Early Medieval alphabet used primarily to write the early Irish language (in the "orthodox" inscriptions, 4th to 6th centuries AD), and later the Old Irish language (scholastic ogham, 6th to 9th centuries). There are roughly 400 surviving orthodox inscriptions on stone monuments throughout Ireland and western Britain, the bulk of which are in southern Munster. The largest number outside Ireland are in Pembrokeshire, Wales.

The vast majority of the inscriptions consist of personal names.

According to the High Medieval Bríatharogam, the names of various trees can be ascribed to individual letters. For this reason, ogam is sometimes known as the Celtic tree alphabet.

The etymology of the word ogam or ogham remains unclear. One possible origin is from the Irish og-úaim 'point-seam', referring to the seam made by the point of a sharp weapon.

🔗 Technology 🔗 Computing 🔗 Mathematics

A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for evaluating mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonometry. It is one of the simplest analog computers.

Slide rules exist in a diverse range of styles and generally appear in a linear, circular or cylindrical form. Slide rules manufactured for specialized fields such as aviation or finance typically feature additional scales that aid in specialized calculations particular to those fields. The slide rule is closely related to nomograms used for application-specific computations. Though similar in name and appearance to a standard ruler, the slide rule is not meant to be used for measuring length or drawing straight lines. Nor is it designed for addition or subtraction, which is usually performed using other methods, like using an abacus. Maximum accuracy for standard linear slide rules is about three decimal significant digits, while scientific notation is used to keep track of the order of magnitude of results.

English mathematician and clergyman Reverend William Oughtred and others developed the slide rule in the 17th century based on the emerging work on logarithms by John Napier. It made calculations faster and less error-prone than evaluating on paper. Before the advent of the scientific pocket calculator, it was the most commonly used calculation tool in science and engineering. The slide rule's ease of use, ready availability, and low cost caused its use to continue to grow through the 1950s and 1960s, even as desktop electronic computers were gradually introduced. But after the handheld scientific calculator was introduced in 1972 and became inexpensive in the mid-1970s, slide rules became largely obsolete, so most suppliers departed the business.

In the United States, the slide rule is colloquially called a slipstick.

🔗 Disability 🔗 Writing systems 🔗 Constructed languages

Blissymbols or Blissymbolics is a constructed language conceived as an ideographic writing system called Semantography consisting of several hundred basic symbols, each representing a concept, which can be composed together to generate new symbols that represent new concepts. Blissymbols differ from most of the world's major writing systems in that the characters do not correspond at all to the sounds of any spoken language.

Blissymbols was published by Charles K. Bliss in 1949 and found use in the education of people with communication difficulties.

🔗 Technology 🔗 Electronics 🔗 Engineering 🔗 Industrial design

Muntzing is the practice and technique of reducing the components inside an electronic appliance to the minimum required for it to sufficiently function in most operating conditions, reducing design margins above minimum requirements toward zero. The term is named after the man who invented it, Earl "Madman" Muntz, a car and electronics salesman, who was not formally educated or trained in any science or engineering discipline.

In the 1940s and 1950s, television receivers were relatively new to the consumer market, and were more complex pieces of equipment than the radios which were then in popular use. TVs often contained upwards of 30 vacuum tubes, as well as transformers, rheostats, and other electronics. The consequence of high cost was high sales pricing, limiting potential for high-volume sales. Muntz expressed suspicion of complexity in circuit designs, and determined through simple trial and error that he could remove a significant number of electronic components from a circuit design and still end up with a monochrome TV that worked sufficiently well in urban areas, close to transmission towers where the broadcast signal was strong. He carried a pair of wire clippers, and when he felt that one of his builders was overengineering a circuit, he would begin snipping out some of the electronics components. When the TV stopped functioning, he would have the technician reinsert the last removed part. He would repeat the snipping in other portions of the circuit until he was satisfied in his simplification efforts, and then leave the TV as it was without further testing in more adverse conditions for signal reception.

As a result, he reduced his costs and increased his profits at the expense of poorer performance at locations more distant from urban centers. He reasoned that population density was higher in and near the urban centers where the TVs would work, and lower further out where the TVs would not work, so the Muntz TVs were adequate for a very large fraction of his customers. And for those further out, where the Muntz TVs did not work, those could be returned at the customer's additional effort and expense, and not Muntz's. He focused less resources in the product, intentionally accepting bare minimum performance quality, and focused more resources on advertising and sales promotions.

🔗 Germany 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/Maritime warfare 🔗 Military history/World War II 🔗 Military history/German military history 🔗 Military history/European military history 🔗 Military history/British military history

Operation Sea Lion, also written as Operation Sealion (German: Unternehmen Seelöwe), was Nazi Germany's code name for the plan for an invasion of the United Kingdom during the Battle of Britain in the Second World War. Following the Battle of France, Adolf Hitler, the German Führer and Supreme Commander of the Armed Forces, hoped the British government would accept his offer to end the war, and he reluctantly considered invasion only as a last resort if all other options failed.

As a precondition, Hitler specified the achievement of both air and naval superiority over the English Channel and the proposed landing sites, but the German forces did not achieve either at any point during the war, and both the German High Command and Hitler himself had serious doubts about the prospects for success. Nevertheless, both the German Army and Navy undertook a major programme of preparations for an invasion: training troops, developing specialised weapons and equipment, and modifying transport vessels. A large number of river barges and transport ships were gathered together on the Channel coast, but with Luftwaffe aircraft losses increasing in the Battle of Britain and no sign that the Royal Air Force had been defeated, Hitler postponed Sea Lion indefinitely on 17 September 1940 and it was never put into action.

🔗 Biography 🔗 Physics 🔗 Biography/science and academia 🔗 Physics/Biographies

Ernst Florens Friedrich Chladni (German: [ˈɛʁnst ˈfloːʁɛns ˈfʁiːdʁɪç ˈkladnɪ]; 30 November 1756 – 3 April 1827) was a German physicist and musician. His most important work, for which he is sometimes labeled the father of acoustics, included research on vibrating plates and the calculation of the speed of sound for different gases. He also undertook pioneering work in the study of meteorites and is regarded by some as the father of meteoritics.

🔗 Companies 🔗 Aviation 🔗 Spaceflight 🔗 Aviation/aircraft 🔗 Rocketry

Rotary Rocket Company was a rocketry company that developed the Roton concept in the late 1990s as a fully reusable single-stage-to-orbit (SSTO) crewed spacecraft. The design was initially conceived by Bevin McKinney, who shared it with Gary Hudson. In 1996, Rotary Rocket Company was formed to commercialize the concept. The Roton was intended to reduce costs of launching payloads into low earth orbit by a factor of ten.

The company gathered considerable venture capital from angel investors and opened a factory headquartered in a 45,000-square-foot (4,200 m²) facility at Mojave Air and Space Port in Mojave, California. The fuselage for their vehicles was made by Scaled Composites, at the same airport, while the company developed the novel engine design and helicopter-like landing system. A full-scale test vehicle made three hover flights in 1999, but the company exhausted its funds and closed its doors in early 2001.

🔗 Civil engineering 🔗 Water

A qanat or kariz is a gently sloping underground channel to transport water from an aquifer or water well to surface for irrigation and drinking, acting as an underground aqueduct. This is an old system of water supply from a deep well with a series of vertical access shafts. The qanats still create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates, but the value of this system is directly related to the quality, volume, and regularity of the water flow. Traditionally qanats are built by a group of skilled laborers, muqannīs, with hand labor. The profession historically paid well and was typically handed down from father to son. According to most sources, the qanat technology was developed in ancient Iran by the Persian people sometime in the early 1st millennium BCE, and spread from there slowly westward and eastward. However, some other sources suggest a Southeast Arabian origin.

🔗 Climate change 🔗 Oceans 🔗 Limnology and Oceanography

The ocean temperature varies by depth, geographical location and season. Both the temperature and salinity of ocean water differs. Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh. Deep ocean water is cold, salty water found deep below the surface of Earth's oceans. This water has a very uniform temperature, around 0-3 °C. The ocean temperature also depends on the amount of solar radiation falling on its surface. In the tropics, with the Sun nearly overhead, the temperature of the surface layers can rise to over 30 °C (86 °F) while near the poles the temperature in equilibrium with the sea ice is about −2 °C (28 °F). There is a continuous circulation of water in the oceans. Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface.

Ocean temperature as a term is used either for the temperature in the ocean at any depth, or specifically for the ocean temperatures that are not near the surface (in which case it is synonymous with "deep ocean temperature").

It is clear that the oceans are warming as a result of climate change and this rate of warming is increasing.^: 9 The upper ocean (above 700 m) is warming fastest, but the warming trend extends throughout the ocean. In 2022, the global ocean was the hottest ever recorded by humans.

🔗 Mathematics 🔗 Statistics

Simpson's paradox, which goes by several names, is a phenomenon in probability and statistics, in which a trend appears in several different groups of data but disappears or reverses when these groups are combined. This result is often encountered in social-science and medical-science statistics and is particularly problematic when frequency data is unduly given causal interpretations. The paradox can be resolved when causal relations are appropriately addressed in the statistical modeling.

Simpson's paradox has been used as an exemplar to illustrate to the non-specialist or public audience the kind of misleading results mis-applied statistics can generate. Martin Gardner wrote a popular account of Simpson's paradox in his March 1976 Mathematical Games column in Scientific American.

Edward H. Simpson first described this phenomenon in a technical paper in 1951, but the statisticians Karl Pearson et al., in 1899, and Udny Yule, in 1903, had mentioned similar effects earlier. The name Simpson's paradox was introduced by Colin R. Blyth in 1972.

It is also referred to as or Simpson's reversal, Yule–Simpson effect, amalgamation paradox, or reversal paradox.