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🔗 Technology 🔗 Sweden 🔗 Metalworking

Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length.

An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called wringing, which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using 3 blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999 mm in 0.001 mm steps (or .3000 to .3999 inches in 0.0001 inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson. They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.

🔗 China 🔗 Mythology 🔗 Taoism

Erlang Shen (二郎神), or Erlang is a Chinese God with a third truth-seeing eye in the middle of his forehead.

Er-lang Shen may be a deified version of several semi-mythical folk heroes who help regulate China's torrential floods dating variously from the Qin, Sui, and Jin dynasties. A later Buddhist source identifies him as the second son of the Northern Heavenly King Vaishravana.

In the Ming semi-mythical novels Creation of the Gods and Journey to the West, Erlang Shen is the nephew of the Jade Emperor. In the former, he assists the Zhou army in defeating the Shang. In the latter, he is the second son of a mortal and Jade emperor's sister. In the legend, he is known as the greatest warrior god of heaven.

🔗 United States/U.S. Government 🔗 United States 🔗 International relations 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Terrorism 🔗 Military history/Cold War 🔗 Cold War 🔗 Military history/South American military history 🔗 Cuba

Operation Northwoods was a proposed false flag operation against the Cuban government that originated within the U.S. Department of Defense (DoD) and the Joint Chiefs of Staff (JCS) of the United States government in 1962. The proposals called for the Central Intelligence Agency (CIA) or other U.S. government operatives to both stage and actually commit acts of terrorism against American military and civilian targets, blaming them on the Cuban government, and using it to justify a war against Cuba. The possibilities detailed in the document included the possible assassination of Cuban immigrants, sinking boats of Cuban refugees on the high seas, hijacking planes to be shot down or given the appearance of being shot down, blowing up a U.S. ship, and orchestrating violent terrorism in U.S. cities. The proposals were rejected by President John F. Kennedy.

Communists led by Fidel Castro had taken power in Cuba in 1959, which aroused the concern of the U.S. military due to the Cold War. The operation proposed creating public support for a war against Cuba by blaming it for terrorist acts that would actually be perpetrated by the U.S. Government. To this end, Operation Northwoods proposals recommended hijackings and bombings followed by the introduction of phony evidence that would implicate the Cuban government. It stated:

The desired result from the execution of this plan would be to place the United States in the apparent position of suffering defensible grievances from a rash and irresponsible government of Cuba and to develop an international image of a Cuban threat to peace in the Western Hemisphere.

Several other proposals were included within Operation Northwoods, including real or simulated actions against various U.S. military and civilian targets. The operation recommended developing a "Communist Cuban terror campaign in the Miami area, in other Florida cities and even in Washington".

The plan was drafted by the Joint Chiefs of Staff, signed by Chairman Lyman Lemnitzer and sent to the Secretary of Defense. Although part of the U.S. government's anti-communist Cuban Project, Operation Northwoods was never officially accepted; it was authorized by the Joint Chiefs of Staff, but then rejected by President John F. Kennedy. According to currently released documentation, none of the operations became active under the auspices of the Operation Northwoods proposals.

WikiReader was a project to deliver an offline, text-only version of Wikipedia on a mobile device. The project was sponsored by Openmoko and made by Pandigital, and its source code has been released.

The project debuted an offline portable reader for Wikipedia in October 2009. Updates in multiple languages were available online and a twice-yearly offline update service delivered via Micro SD card was also available at a cost of $29 per year. WikiReader versions of the English Wikipedia, Wikiquote, Wiktionary and Project Gutenberg can be installed together on a user-supplied 16 GB Micro SDHC memory card. Unlike Wikipedia itself, the device features parental controls.

The device can also run programs written in the Forth programming language; a simple calculator program is included.

In late 2014, the WikiReader website and project itself were shut down and abandoned for unknown reasons. Existing WikiReaders no longer receive updates to their database. Devices, professionally produced updates, and homegrown updates continue to be available from the secondary markets (e.g. eBay and Amazon), as well as from community efforts centered around the WikiReader subreddit.

🔗 Mathematics

The potato paradox is a mathematical calculation that has a counter-intuitive result. The Universal Book of Mathematics states the problem as follows:

Fred brings home 100 kg of potatoes, which (being purely mathematical potatoes) consist of 99% water. He then leaves them outside overnight so that they consist of 98% water. What is their new weight? The surprising answer is 50 kg.

In Quine's classification of paradoxes, the potato paradox is a veridical paradox.

🔗 Philosophy 🔗 Classical Greece and Rome 🔗 Greece 🔗 Philosophy/Ancient philosophy 🔗 Philosophy/Epistemology

Pyrrhonism is an Ancient Greek school of philosophical skepticism which rejects dogma and advocates the suspension of judgement over the truth of all beliefs. It was founded by Aenesidemus in the first century BCE, and said to have been inspired by the teachings of Pyrrho and Timon of Phlius in the fourth century BCE. Pyrrhonism is best known today through the surviving works of Sextus Empiricus, writing in the late second century or early third century CE. The publication of Sextus' works in the Renaissance ignited a revival of interest in Skepticism and played a major role in Reformation thought and the development of early modern philosophy.

🔗 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.

🔗 Telecommunications 🔗 Meteorology 🔗 Astronomy 🔗 Solar System

The solar storm of 1859 (also known as the Carrington Event) was a powerful geomagnetic storm during solar cycle 10 (1855–1867). A solar coronal mass ejection (CME) hit Earth's magnetosphere and induced the largest geomagnetic storm on record, September 1–2, 1859. The associated "white light flare" in the solar photosphere was observed and recorded by British astronomers Richard C. Carrington (1826–1875) and Richard Hodgson (1804–1872). The storm caused strong auroral displays and wrought havoc with telegraph systems. The now-standard unique IAU identifier for this flare is SOL1859-09-01.

A solar storm of this magnitude occurring today would cause widespread electrical disruptions, blackouts and damage due to extended outages of the electrical grid. The solar storm of 2012 was of similar magnitude, but it passed Earth's orbit without striking the planet, missing by nine days.

🔗 Archaeology 🔗 Indigenous peoples of North America

The Solutrean hypothesis on the peopling of the Americas claims that the earliest human migration to the Americas took place from Europe, with Solutreans traveling along pack ice in the Atlantic Ocean. This hypothesis contrasts with the mainstream academic narrative that the Americas were first populated by people crossing the Bering Strait to Alaska by foot on what was land during the Last Glacial Period or by following the Pacific coastline from Asia to America by boat.

The Solutrean hypothesis posits that around 21,000 years ago a group of people from the Solutré region of France, who are historically characterized by their unique lithic technique, migrated to North America along pack ice in the Atlantic Ocean. Once they made it to North America, their lithic technique dispersed around the continent (c. 13,000 years ago) to provide the basis for the later popularization of Clovis lithic technology. The premise behind the Solutrean Hypothesis is that the similarities between Clovis and Solutrean lithic technologies are evidence that the Solutreans were the first people to migrate to the Americas, dating far before mainstream scientific theories of the peopling of the Americas.

Originally proposed in the 1970s, the theory has received some support in the 2010s, notably by Dennis Stanford of the Smithsonian Institution and Bruce Bradley of the University of Exeter. However, according to David Meltzer, "[f]ew if any archaeologists—or, for that matter, geneticists, linguists, or physical anthropologists—take seriously the idea of a Solutrean colonization of America." The evidence for the hypothesis is considered more consistent with other scenarios. In addition to an interval of thousands of years between the Clovis and Solutrean eras, the two technologies show only incidental similarities. There is no evidence for any Solutrean seafaring, far less for any technology that could take humans across the Atlantic in an ice age. Genetic evidence supports the theory of Asian, not European, origins for the peopling of the Americas.

🔗 Climate change 🔗 Environment 🔗 Meteorology 🔗 Urban studies and planning

An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the urban heat island effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas.

Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons, and decreases the occurrence of weak tornadoes. The UHI decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems.

Not all cities have a distinct urban heat island, and the heat island characteristics depend strongly on the background climate of the area in which the city is located. Mitigation of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat.

Concerns have been raised about possible contribution from urban heat islands to global warming. While some lines of research did not detect a significant impact, other studies have concluded that heat islands can have measurable effects on climate phenomena at the global scale.