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🔗 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.

🔗 Technology

A planimeter, also known as a platometer, is a measuring instrument used to determine the area of an arbitrary two-dimensional shape.

🔗 Engineering 🔗 Metalworking

Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can avoid, or greatly reduce, the need to use metal removal processes, thereby drastically reducing yield losses in manufacture and often resulting in lower costs.

Powder metallurgy is also used to make unique materials impossible to get from melting or forming in other ways. A very important product of this type is tungsten carbide (WC). WC is used to cut and form other metals and is made from WC particles bonded with cobalt. It is very widely used in industry for tools of many types and globally ~50,000 tonnes/year (t/y) is made by PM. Other products include sintered filters, porous oil-impregnated bearings, electrical contacts and diamond tools.

Since the advent of industrial production–scale metal powder–based additive manufacturing (AM) in the 2010s, selective laser sintering and other metal AM processes are a new category of commercially important powder metallurgy applications.

🔗 Germany 🔗 Archaeology 🔗 Germany/Hamburg

The Ovelgönne Bread Roll is the remaining part of a bread roll originating from the Pre-Roman Iron Age of Northern Europe, which was found in 1952 during archaeological excavations in a loam mine in the Buxtehude district Ovelgönne in Lower Saxony, Germany. The piece of bread is the oldest surviving viennoiserie and formed bakery product from Europe. The find, along with a reconstruction, are in the permanent exhibition of the Archaeological Museum Hamburg in Harburg, Hamburg.

🔗 Biography 🔗 Military history 🔗 Military history/North American military history 🔗 Mexico 🔗 Military history/Military biography 🔗 Military history/Early Modern warfare 🔗 Military history/Spanish military history 🔗 Mesoamerica 🔗 Spain 🔗 Military history/European military history

Gonzalo Guerrero (also known as Gonzalo Marinero, Gonzalo de Aroca and Gonzalo de Aroza) was a sailor from Palos, Spain who was shipwrecked along the Yucatán Peninsula and was taken as a slave by the local Maya. Earning his freedom, Guerrero became a respected warrior under a Maya lord and raised three of the first mestizo children in Mexico and one of the first mestizo children in the Americas, alongside Miguel Díez de Aux and the children of Caramuru and João Ramalho in Brazil. Little is known of his early life.

🔗 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.

🔗 United States 🔗 Law 🔗 Politics 🔗 National Archives 🔗 Politics/American politics

The Alien and Sedition Acts were a set of four laws enacted in 1798 that applied restrictions to immigration and speech in the United States. The Naturalization Act increased the requirements to seek citizenship, the Alien Friends Act allowed the president to imprison and deport non-citizens, the Alien Enemies Act gave the president additional powers to detain non-citizens during times of war, and the Sedition Act criminalized false and malicious statements about the federal government. The Alien Friends Act and the Sedition Act expired after a set number of years, and the Naturalization Act was repealed in 1802. The Alien Enemies Act is still in effect.

The Alien and Sedition Acts were controversial. They were supported by the Federalist Party, and supporters argued that the bills strengthened national security during the Quasi-War, an undeclared naval war with France from 1798 to 1800. The acts were denounced by Democratic-Republicans as suppression of voters and violation of free speech under the First Amendment. While they were in effect, the Alien and Sedition Acts, and the Sedition Act in particular, were used to suppress publishers affiliated with the Democratic-Republicans, and several publishers were arrested for criticism of the Adams administration. The Democratic-Republicans took power in 1800, in part because of backlash to the Alien and Sedition Acts, and all but the Alien Enemies Act were eliminated by the next Congress. The Alien Enemies Act has been invoked several times since, particularly during World War II. The Alien and Sedition Acts are generally received negatively by modern historians, and the Supreme Court has since indicated that aspects of the laws would be found unconstitutional if challenged.

🔗 Color 🔗 Physiology

Eigengrau (German: "intrinsic gray", lit. "own gray"; pronounced [ˈʔaɪ̯gn̩ˌgʁaʊ̯]), also called Eigenlicht (Dutch and German: "own light"), dark light, or brain gray, is the uniform dark gray background that many people report seeing in the absence of light. The term Eigenlicht dates back to the nineteenth century, but has rarely been used in recent scientific publications. Common scientific terms for the phenomenon include "visual noise" or "background adaptation". These terms arise due to the perception of an ever-changing field of tiny black and white dots seen in the phenomenon.

Eigengrau is perceived as lighter than a black object in normal lighting conditions, because contrast is more important to the visual system than absolute brightness. For example, the night sky looks darker than Eigengrau because of the contrast provided by the stars.

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/Military science, technology, and theory 🔗 Aviation/aircraft

In aerobatics the Cobra maneuver, also known as just the Cobra, is a dramatic and demanding maneuver in which an airplane flying at a moderate speed suddenly raises the nose momentarily to the vertical position and slightly beyond, before dropping it back to normal, effectively making the plane a full body air brake.

The maneuver relies on the ability of the plane to be able to quickly change alpha which momentarily stalls the plane without overloading the airframe and powerful engine thrust to maintain approximately constant altitude through the entire move. It is an impressive maneuver to demonstrate an aircraft's pitch control authority, high alpha stability and engine-versus-inlet compatibility, as well as the pilot's skill.

Although the maneuver is mainly performed at air shows it has use in close range air combat as a last ditch maneuver to make a pursuing plane overshoot. There is currently no widely spread or readily available evidence of the Cobra being used in real combat, although, there are records of it being used during mockup-dogfights and during border protection.

🔗 Human rights 🔗 History 🔗 Military history 🔗 Crime 🔗 China 🔗 Politics 🔗 Socialism 🔗 Law Enforcement 🔗 Sociology 🔗 Sociology/social movements 🔗 Military history/Cold War 🔗 Military history/Asian military history 🔗 Military history/Chinese military history

The Tiananmen Square protests or Tiananmen Square Incident, commonly known in mainland China as the June Fourth Incident (Chinese: 六四事件; pinyin: liùsì shìjiàn, literally six-four incident), were student-led demonstrations held in Tiananmen Square in Beijing during 1989. The popular national movement inspired by the Beijing protests is sometimes called the '89 Democracy Movement (Chinese: 八九民運; pinyin: bājiǔ mínyùn). The protests started on April 15 and were forcibly suppressed on June 4 when the government declared martial law and sent the military to occupy central parts of Beijing. In what became known as the Tiananmen Square Massacre (Chinese: 天安門大屠殺; pinyin: tiān'ānmén dà túshā), troops with assault rifles and tanks fired at the demonstrators and those trying to block the military's advance into Tiananmen Square. Estimates of the death toll vary from several hundred to several thousand, with thousands more wounded.

Set off by the death of pro-reform Communist general secretary Hu Yaobang in April 1989, amid the backdrop of rapid economic development and social changes in post-Mao China, the protests reflected anxieties about the country's future in the popular consciousness and among the political elite. The reforms of the 1980s had led to a nascent market economy which benefited some people but seriously disaffected others, and the one-party political system also faced a challenge of legitimacy. Common grievances at the time included inflation, corruption, limited preparedness of graduates for the new economy, and restrictions on political participation. The students called for greater accountability, constitutional due process, democracy, freedom of the press, and freedom of speech, although they were highly disorganized and their goals varied. At the height of the protests, about 1 million people assembled in the Square.

As the protests developed, the authorities responded with both conciliatory and hardline tactics, exposing deep divisions within the party leadership. By May, a student-led hunger strike galvanized support for the demonstrators around the country, and the protests spread to some 400 cities. Ultimately, China's paramount leader Deng Xiaoping and other Communist Party elders believed the protests to be a political threat and resolved to use force. The State Council declared martial law on May 20 and mobilized as many as 300,000 troops to Beijing. The troops advanced into central parts of Beijing on the city's major thoroughfares in the early morning hours of June 4, killing both demonstrators and bystanders in the process.

The international community, human rights organizations, and political analysts condemned the Chinese government for the massacre. Western countries imposed arms embargoes on China. The Chinese government made widespread arrests of protesters and their supporters, suppressed other protests around China, expelled foreign journalists, strictly controlled coverage of the events in the domestic press, strengthened the police and internal security forces, and demoted or purged officials it deemed sympathetic to the protests. More broadly, the suppression halted the policies of liberalization in the 1980s. Considered a watershed event, the protests set the limits on political expression in China up to the present day. Its memory is widely associated with questioning the legitimacy of Communist Party rule and remains one of the most sensitive and most widely censored topics in China.