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🔗 California 🔗 LGBT studies

Stonewall Nation was the informal name given to a proposition by gay activists to establish a separatist community in Alpine County, California in 1970. The small population of the county and the election rules for California counties at the time suggested to these activists that if they could induce a relatively small number of gay people to move to the county, they could recall the county government and replace it with an all-gay slate.

The plan did not gain traction in the LGBT community and a right-wing Christian minister announced plans to move large numbers of Christians to the county to counteract any attempt by gay people to take over the county government. The plan was abandoned about a year after it was conceived and the idea has come to be seen as a practical joke.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Cold War 🔗 Military history/Asian military history 🔗 Military history/Southeast Asian military history 🔗 Vietnam

The Fall of Saigon, also known as the Liberation of Saigon by North Vietnamese, was the capture of Saigon, the capital of South Vietnam, by the People's Army of Vietnam (PAVN) and the Viet Cong on 30 April 1975. The event marked the end of the Vietnam War and the start of a transition period to the formal reunification of Vietnam into the Socialist Republic of Vietnam.

The PAVN, under the command of General Văn Tiến Dũng, began their final attack on Saigon on 29 April 1975, with the Army of the Republic of Vietnam (ARVN) forces commanded by General Nguyễn Văn Toàn suffering a heavy artillery bombardment. By the afternoon of the next day, the PAVN had occupied the important points of the city and raised their flag over the South Vietnamese presidential palace. The city was renamed Hồ Chí Minh City, after the late North Vietnamese President Hồ Chí Minh.

The capture of the city was preceded by Operation Frequent Wind, the evacuation of almost all American civilian and military personnel in Saigon, along with tens of thousands of South Vietnamese civilians who had been associated with the Republic of Vietnam. A few Americans chose not to be evacuated. United States ground combat units had left South Vietnam more than two years prior to the fall of Saigon and were not available to assist with either the defense of Saigon or the evacuation. The evacuation was the largest helicopter evacuation in history. In addition to the flight of refugees, the end of the war and the institution of new rules by the communists contributed to a decline in the city's population.

🔗 Volcanoes 🔗 Islands 🔗 British Overseas Territories 🔗 Argentina 🔗 South America/South Georgia and the South Sandwich Islands 🔗 South America

South Georgia and the South Sandwich Islands (SGSSI) is a British Overseas Territory in the southern Atlantic Ocean. It is a remote and inhospitable collection of islands, consisting of South Georgia Island and a chain of smaller islands known as the South Sandwich Islands. South Georgia is 165 kilometres (103 mi) long and 35 kilometres (22 mi) wide and is by far the largest island in the territory. The South Sandwich Islands lie about 700 kilometres (430 mi) southeast of South Georgia. The territory's total land area is 3,903 km² (1,507 sq mi). The Falkland Islands are about 1,300 kilometres (810 mi) west from its nearest point.

No permanent native population lives in the South Sandwich Islands, and a very small non-permanent population resides on South Georgia. There are no scheduled passenger flights or ferries to or from the territory, although visits by cruise liners to South Georgia are increasingly popular, with several thousand visitors each summer.

The United Kingdom claimed sovereignty over South Georgia in 1775 and the South Sandwich Islands in 1908. The territory of "South Georgia and the South Sandwich Islands" was formed in 1985; previously, it had been governed as part of the Falkland Islands Dependencies. Argentina claimed South Georgia in 1927 and claimed the South Sandwich Islands in 1938.

Argentina maintained a naval station, Corbeta Uruguay, on Thule Island in the South Sandwich Islands from 1976 until 1982 when it was closed by the Royal Navy. The Argentine claim over South Georgia contributed to the 1982 Falklands War, during which Argentine forces briefly occupied the island. Argentina continues to claim sovereignty over South Georgia and the South Sandwich Islands.

Toothfish are vital to the islands' economy; as a result, Toothfish Day is celebrated on 4 September as a bank holiday in the territory.

🔗 Spaceflight 🔗 Physics

The South Atlantic Anomaly (SAA) is an area where Earth's inner Van Allen radiation belt comes closest to Earth's surface, dipping down to an altitude of 200 kilometres (120 mi). This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation.

The effect is caused by the non-concentricity of Earth and its magnetic dipole. The SAA is the near-Earth region where Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field.

🔗 Physics

In the philosophy of thermal and statistical physics, the Brownian ratchet or Feynman–Smoluchowski ratchet is an apparent perpetual motion machine of the second kind, first analysed in 1912 as a thought experiment by Polish physicist Marian Smoluchowski. It was popularised by American Nobel laureate physicist Richard Feynman in a physics lecture at the California Institute of Technology on May 11, 1962, during his Messenger Lectures series The Character of Physical Law in Cornell University in 1964 and in his text The Feynman Lectures on Physics as an illustration of the laws of thermodynamics. The simple machine, consisting of a tiny paddle wheel and a ratchet, appears to be an example of a Maxwell's demon, able to extract mechanical work from random fluctuations (heat) in a system at thermal equilibrium, in violation of the second law of thermodynamics. Detailed analysis by Feynman and others showed why it cannot actually do this.

🔗 United States 🔗 Biography 🔗 California 🔗 Women scientists 🔗 Biography/science and academia 🔗 Astronomy 🔗 United States/Arizona 🔗 Solar System 🔗 California/California State University

Carolyn Jean Spellmann Shoemaker (June 24, 1929 – August 13, 2021) was an American astronomer and a co-discoverer of Comet Shoemaker–Levy 9. She once held the record for most comets discovered by an individual.

Although Shoemaker earned degrees in history, political science and English literature, she had little interest in science until she met and married geologist Eugene M. ("Gene") Shoemaker in 1950–51. She later said that his explanations of his work thrilled her. Despite her relative inexperience and lack of a science degree, California Institute of Technology (Caltech) had no objection to her joining Gene's team there as a research assistant. She had already shown herself to be unusually patient, and demonstrated exceptional stereoscopic vision, which were particularly valuable qualities for looking for objects in near-Earth space.

🔗 Lists 🔗 Transport 🔗 Automobiles 🔗 Countries 🔗 Trucks

This article is a list of countries by the number of road motor vehicles per 1,000 inhabitants. This includes cars, vans, buses, and freight and other trucks; but excludes motorcycles and other two-wheelers.

China has the largest fleet of motor vehicles in the world in 2021, with 292 million cars, and in 2009 became the world's largest new car market as well. In 2011, a total of 80 million cars and commercial vehicles were built, led by China, with 18.4 million motor vehicles manufactured.

🔗 Spaceflight 🔗 Psychology 🔗 Spirituality

The overview effect is a cognitive shift in awareness reported by some astronauts during spaceflight, often while viewing the Earth from outer space.

It is the experience of seeing firsthand the reality of the Earth in space, which is immediately understood to be a tiny, fragile ball of life, "hanging in the void", shielded and nourished by a paper-thin atmosphere. From space, national boundaries vanish, the conflicts that divide people become less important, and the need to create a planetary society with the united will to protect this "pale blue dot" becomes both obvious and imperative.

The thing that really surprised me was that it [Earth] projected an air of fragility. And why, I don’t know. I don’t know to this day. I had a feeling it’s tiny, it’s shiny, it’s beautiful, it’s home, and it’s fragile.

Astronauts Michael Collins, Ron Garan, Rusty Schweikart, Edgar Mitchell, Tom Jones, Scott Kelly, James Irwin, Mike Massimino, André Kuipers, Chris Hadfield, and Sally Ride are all reported to have experienced the effect.

The term and concept were coined in 1987 by Frank White, who explored the theme in his book The Overview Effect — Space Exploration and Human Evolution (Houghton-Mifflin, 1987), (AIAA, 1998).

In 2018, the SpaceBuzz project was created so "children around the world can also get to experience the Overview Effect." It was announced in a press release on December 20 by astronaut André Kuipers on the European Space Agency's (ESA) website. Spacebuzz aims to give children an overview effect like experience using virtual reality (VR) in order to have the same insight astronauts have when seeing planet Earth from space. Spacebuzz is a project started by the Overview Effect Foundation backed by ESA and the Netherlands Space Office..

In late 2019 it was reported that researchers at the University of Missouri aimed to reproduce the experience, with an isolation tank, half a tonne of Epsom salts, and a waterproof VR headset.

🔗 Technology

A Tesla valve, called by Tesla a valvular conduit, is a fixed-geometry passive check valve. It allows a fluid to flow preferentially in one direction, without moving parts. The device is named after Nikola Tesla, who was awarded U.S. Patent 1,329,559 in 1920 for its invention. The patent application describes the invention as follows:

The interior of the conduit is provided with enlargements, recesses, projections, baffles, or buckets which, while offering virtually no resistance to the passage of the fluid in one direction, other than surface friction, constitute an almost impassable barrier to its flow in the opposite direction.

Tesla illustrates this with the drawing, showing one possible construction with a series of eleven flow-control segments, although any other number of such segments could be used as desired to increase or decrease the flow regulation effect.

One computational fluid dynamics simulation of Tesla valves with two and four segments showed that the flow resistance in the blocking (or reverse) direction was about 15 and 40 times greater, respectively, than the unimpeded (or forward) direction. This lends support to Tesla's patent assertion that in the valvular conduit in his diagram, a pressure ratio "approximating 200 can be obtained so that the device acts as a slightly leaking valve".

The Tesla valve is used in microfluidic applications and offers advantages such as scalability, durability, and ease of fabrication in a variety of materials.

🔗 Computer science 🔗 Systems 🔗 Systems/Scientific modeling

Jackson structured programming (JSP) is a method for structured programming developed by British software consultant Michael A. Jackson and described in his 1975 book Principles of Program Design. The technique of JSP is to analyze the data structures of the files that a program must read as input and produce as output, and then produce a program design based on those data structures, so that the program control structure handles those data structures in a natural and intuitive way.

JSP describes structures (of both data and programs) using three basic structures – sequence, iteration, and selection (or alternatives). These structures are diagrammed as (in effect) a visual representation of a regular expression.