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🔗 Spaceflight 🔗 Physics 🔗 Rocketry

The Tsiolkovsky rocket equation, classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity can thereby move due to the conservation of momentum.

${\displaystyle \Delta v=v_{\text{e}}\ln {\frac {m_{0}}{m_{f}}}=I_{\text{sp}}g_{0}\ln {\frac {m_{0}}{m_{f}}}}$

where:

${\displaystyle \Delta v\ }$ is delta-v – the maximum change of velocity of the vehicle (with no external forces acting).

${\displaystyle m_{0}}$ is the initial total mass, including propellant, also known as wet mass.

${\displaystyle m_{f}}$ is the final total mass without propellant, also known as dry mass.

${\displaystyle v_{\text{e}}=I_{\text{sp}}g_{0}}$ is the effective exhaust velocity, where:

${\displaystyle I_{\text{sp}}}$ is the specific impulse in dimension of time.

${\displaystyle g_{0}}$ is standard gravity.

${\displaystyle \ln }$ is the natural logarithm function.

🔗 Physics

Wigner's friend is a thought experiment in theoretical quantum physics, first conceived by the physicist Eugene Wigner in 1961., and developed into a thought experiment by David Deutsch in 1985. The scenario involves an indirect observation of a quantum measurement: An observer W observes another observer F who performs a quantum measurement on a physical system. The two observers then formulate a statement about the physical system's state after the measurement according to the laws of quantum theory. However, in most of the interpretations of quantum theory, the resulting statements of the two observers contradict each other. This reflects a seeming incompatibility of two laws in quantum theory: the deterministic and continuous time evolution of the state of a closed system and the probabilistic, discontinuous collapse of the state of a system upon measurement. Wigner's friend is therefore directly linked to the measurement problem in quantum mechanics with its famous Schrödinger's cat paradox.

🔗 Germany 🔗 Africa 🔗 Birds 🔗 European history

The term Pfeilstorch (German for "arrow stork") is given to storks injured by an arrow while wintering in Africa, before returning to Europe with the arrow stuck in their bodies. To date, around 25 Pfeilstörche have been documented.

The first and most famous Pfeilstorch was a white stork found in 1822 near the German village of Klütz, in the state of Mecklenburg-Vorpommern. It was carrying a 30-inch (76 cm) spear from central Africa in its neck. The specimen was stuffed and can be seen today in the zoological collection of the University of Rostock. It is therefore referred to as the Rostocker Pfeilstorch.

This Pfeilstorch was crucial in understanding the migration of European birds. Before migration was understood, people struggled to explain the sudden annual disappearance of birds like the white stork and barn swallow. Besides migration, some theories of the time held that they turned into other kinds of birds, mice, or hibernated underwater during the winter, and such theories were even propagated by zoologists of the time. The Rostocker Pfeilstorch in particular proved that birds migrate long distances to wintering grounds.

🔗 Food and drink 🔗 Plants 🔗 Alternative medicine 🔗 Women's Health

Silphium (also known as silphion, laserwort, or laser) was a plant that was used in classical antiquity as a seasoning, perfume, as an aphrodisiac, or as a medicine. It also was used as a contraceptive by ancient Greeks and Romans. It was the essential item of trade from the ancient North African city of Cyrene, and was so critical to the Cyrenian economy that most of their coins bore a picture of the plant. The valuable product was the plant's resin (laser, laserpicium, or lasarpicium).

Silphium was an important species in prehistory, as evidenced by the Egyptians and Knossos Minoans developing a specific glyph to represent the silphium plant. It was used widely by most ancient Mediterranean cultures; the Romans who mentioned the plant in poems or songs, considered it "worth its weight in denarii" (silver coins), or even gold. Legend said that it was a gift from the god Apollo.

The exact identity of silphium is unclear. It is commonly believed to be a now-extinct plant of the genus Ferula, perhaps a variety of "giant fennel". The still-extant plants Margotia gummifera and Ferula tingitana have been suggested as other possibilities. Another plant, asafoetida, was used as a cheaper substitute for silphium, and had similar enough qualities that Romans, including the geographer Strabo, used the same word to describe both.

🔗 United States 🔗 International relations 🔗 Espionage 🔗 History 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Politics 🔗 Politics/American politics 🔗 United States/U.S. history

United States involvement in regime change describes United States government participation or interference, both overt and covert, in the replacement of foreign governments. In the latter half of the 19th century, the U.S. government initiated actions for regime change mainly in Latin America and the southwest Pacific, including the Spanish–American and Philippine–American wars. At the onset of the 20th century, the United States shaped or installed governments in many countries around the world, including neighbors Panama, Honduras, Nicaragua, Mexico, Haiti, and the Dominican Republic.

During World War II, the United States helped overthrow many Nazi Germany or imperial Japanese puppet regimes. Examples include regimes in the Philippines, Korea, the Eastern portion of China, and much of Europe. United States forces were also instrumental in ending the rule of Adolf Hitler over Germany and of Benito Mussolini over Italy. After World War II, the United States in 1945 ratified the UN Charter, the preeminent international law document, which legally bound the U.S. government to the Charter's provisions, including Article 2(4), which prohibits the threat or use of force in international relations, except in very limited circumstances. Therefore, any legal claim advanced to justify regime change by a foreign power carries a particularly heavy burden.

In the aftermath of World War II, the U.S. government struggled with the Soviet Union for global leadership, influence and security within the context of the Cold War. Under the Eisenhower administration, the U.S. government feared that national security would be compromised by governments propped by the Soviet Union's own involvement in regime change and promoted the domino theory, with later presidents following Eisenhower's precedent. Subsequently, the United States expanded the geographic scope of its actions beyond traditional area of operations, Central America and the Caribbean. Significant operations included the United States and United Kingdom-orchestrated 1953 Iranian coup d'état, the 1961 Bay of Pigs Invasion targeting Cuba, and support for the overthrow of Sukarno by General Suharto in Indonesia. In addition, the U.S. has interfered in the national elections of countries, including the Philippines in 1953, and Japan in the 1950s and 1960s as well as Lebanon in 1957. According to one study, the U.S. performed at least 81 overt and covert known interventions in foreign elections during the period 1946–2000. Another study found that the U.S. engaged in 64 covert and six overt attempts at regime change during the Cold War.

Following the dissolution of the Soviet Union, the United States has led or supported wars to determine the governance of a number of countries. Stated U.S. aims in these conflicts have included fighting the War on Terror, as in the ongoing Afghan war, or removing dictatorial and hostile regimes, as in the Iraq War.

🔗 Biography 🔗 Military history 🔗 Architecture 🔗 Greece 🔗 Military history/Military biography 🔗 Biography/military biography 🔗 Military history/World War II 🔗 Military history/Cold War 🔗 Dance 🔗 Composers 🔗 Dance/Ballet 🔗 Classical music 🔗 Military history/Balkan military history 🔗 Biography/Musicians 🔗 Military history/European military history

Iannis Xenakis (also spelt as Yannis Xenakis) (Greek: Γιάννης (Ιάννης) Ξενάκης [ˈʝanis kseˈnacis]; 29 May 1922 – 4 February 2001) was a Greek-French composer, music theorist, architect, performance director and engineer. After 1947, he fled Greece, becoming a naturalized citizen of France. He is considered an important post-World War II composer whose works helped revolutionize 20th-century classical music.

Xenakis pioneered the use of mathematical models in music such as applications of set theory, stochastic processes and game theory and was also an important influence on the development of electronic and computer music. He integrated music with architecture, designing music for pre-existing spaces, and designing spaces to be integrated with specific music compositions and performances.

Among his most important works are Metastaseis (1953–54) for orchestra, which introduced independent parts for every musician of the orchestra; percussion works such as Psappha (1975) and Pléïades (1979); compositions that introduced spatialization by dispersing musicians among the audience, such as Terretektorh (1966); electronic works created using Xenakis's UPIC system; and the massive multimedia performances Xenakis called polytopes, that were a summa of his interests and skills. Among the numerous theoretical writings he authored, the book Formalized Music: Thought and Mathematics in Composition (French edition 1963, English translation 1971) is regarded as one of his most important. As an architect, Xenakis is primarily known for his early work under Le Corbusier: the Sainte Marie de La Tourette, on which the two architects collaborated, and the Philips Pavilion at Expo 58, which Xenakis designed by himself.

🔗 Yugoslavia 🔗 Economics

Despite common origins, the economy of the Socialist Federal Republic of Yugoslavia (SFRY) was significantly different from the economies of the Soviet Union and other Eastern European socialist states, especially after the Yugoslav-Soviet break-up in 1948. The occupation and liberation struggle in World War II left Yugoslavia's infrastructure devastated. Even the most developed parts of the country were largely rural and the little industry of the country was largely damaged or destroyed.

🔗 Biography

Gregory F. Packer (born December 18, 1963), is a retired American highway maintenance worker from Huntington, New York, best known for frequently being quoted as a "man on the street" in newspapers, magazines and television broadcasts from 1995 to the present. He has been quoted in hundreds of articles and television broadcasts as a member of the public (that is, a "man on the street" rather than a newsmaker or expert). Although he always gives his real name, he has admitted to making things up to get into the paper.

Packer's status as a frequent interviewee is due to a number of factors, including seeking out members of the press and appearing friendly, although mostly it is due to his hobby of attending public appearances of celebrities and other media events and attempting to be first in line on such occasions. This has led to him being dubbed a professional line sitter. It has also led to Packer's other claim to fame: being the first person in the world to buy an iPhone, on June 29, 2007 at Apple Fifth Avenue in New York City, after having camped out for five days in front of the store. (He tried to similarly be the first to buy an iPad in 2010, but was bumped from the first position in line due to not having a reservation.) His efforts to be first in line have also allowed him to meet people including Mariah Carey, Garth Brooks, Dennis Rodman and Ringo Starr, as well as at least four presidents of the United States: Jimmy Carter, Bill Clinton, George W. Bush and (before he became president) Donald Trump.

🔗 Biography 🔗 Biography/sports and games 🔗 Cycling

Thomas Stevens (24 December 1854 – 24 January 1935) was the first person to circle the globe by bicycle. He rode a large-wheeled Ordinary, also known as a penny-farthing, from April 1884 to December 1886. He later searched for Henry Morton Stanley in Africa, investigated the claims of Indian ascetics and became manager of the Garrick Theatre in London.

🔗 Physics 🔗 Weather 🔗 Weather/Weather 🔗 Weather/General meteorology

A Fata Morgana (Italian: [ˈfaːta morˈɡaːna]) is a complex form of superior mirage visible in a narrow band right above the horizon. The term Fata Morgana is the Italian translation of "Morgan the Fairy" (Morgan le Fay of Arthurian legend). These mirages are often seen in the Italian Strait of Messina, and were described as fairy castles in the air or false land conjured by her magic.

Fata Morgana mirages significantly distort the object or objects on which they are based, often such that the object is completely unrecognizable. A Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant object, including boats, islands, and the coastline. Often, a Fata Morgana changes rapidly. The mirage comprises several inverted (upside down) and upright images stacked on top of one another. Fata Morgana mirages also show alternating compressed and stretched zones.

The optical phenomenon occurs because rays of light bend when they pass through air layers of different temperatures in a steep thermal inversion where an atmospheric duct has formed. In calm weather, a layer of significantly warmer air may rest over colder dense air, forming an atmospheric duct that acts like a refracting lens, producing a series of both inverted and erect images. A Fata Morgana requires a duct to be present; thermal inversion alone is not enough to produce this kind of mirage. While a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion.