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🔗 Spaceflight 🔗 Physics 🔗 Science Fiction

A black hole starship is a theoretical idea for enabling interstellar travel by propelling a starship by using a black hole as the energy source. The concept was first discussed in science fiction, notably in the book Imperial Earth by Arthur C. Clarke, and in the work of Charles Sheffield, in which energy extracted from a Kerr-Newman black hole is described as powering the rocket engines in the story "Killing Vector" (1978).

In a more detailed analysis, a proposal to create an artificial black hole and using a parabolic reflector to reflect its Hawking radiation was discussed in 2009 by Louis Crane and Shawn Westmoreland. Their conclusion was that it was on the edge of possibility, but that quantum gravity effects that are presently unknown will either make it easier, or make it impossible. Similar concepts were also sketched out by Bolonkin.

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Epistemology

In epistemology, the Münchhausen trilemma is a thought experiment used to demonstrate the impossibility of proving any truth, even in the fields of logic and mathematics. If it is asked how any given proposition is known to be true, proof may be provided. Yet that same question can be asked of the proof, and any subsequent proof. The Münchhausen trilemma is that there are only three options when providing further proof in response to further questioning:

• The circular argument, in which the proof of some proposition is supported only by that proposition
• The regressive argument, in which each proof requires a further proof, ad infinitum
• The axiomatic argument, which rests on accepted precepts which are merely asserted rather than defended

The trilemma, then, is the decision among the three equally unsatisfying options.

The name Münchhausen-Trilemma was coined by the German philosopher Hans Albert in 1968 in reference to a trilemma of "dogmatism versus infinite regress versus psychologism" used by Karl Popper. It is a reference to the problem of "bootstrapping", based on the story of Baron Munchausen (in German, "Münchhausen") pulling himself and the horse on which he was sitting out of a mire by his own hair.

It is also known as Agrippa's trilemma or the Agrippan trilemma after a similar argument reported by Sextus Empiricus, which was attributed to Agrippa the Skeptic by Diogenes Laërtius, as well as Fries's trilemma after German philosopher Jakob Friedrich Fries. Sextus' argument, however, consists of five (not three) "modes". Popper in his original 1935 publication mentions neither Sextus nor Agrippa, but attributes his trilemma to Fries.

In contemporary epistemology, advocates of coherentism are supposed to accept the "circular" horn of the trilemma; foundationalists rely on the axiomatic argument. The view that accepts infinite regress is called infinitism.

🔗 Internet culture 🔗 Cats

Longcat (2002 – 20 September 2020) was a Japanese domestic cat that became the subject of an Internet meme due to her length. Longcat, whose real name was "Shiroi", was born in 2002. An image depicting her being held with "outstretched paws" became popular on Japanese imageboard Futaba Channel, where it was nicknamed "Nobiko" ("Stretch" in Japanese) some time around 2005 or 2006. She was reportedly 65 centimetres (26 in) "from head to toe".

Subsequently, the meme spread to English-language websites, primarily 4chan's /b/, where it was edited into various images, and even had a song written about it. A backstory was invented for the cat, involving a world-ending battle called "Catnarok" with a nemesis named "Tacgnol" (resembling Longcat with the colors inverted).

The virtual community and message board Subeta, which made available a number of pixel art virtual accessories for user avatars, briefly introduced a "Longcat scarf" in 2007; this prompted "a legion of internet users to attack Subeta", primarily in the form of a DDoS campaign involving "all of the chans", until the Longcat item was removed later in the month. A Pokémon design released in 2019, the "Gigantamax Meowth", was compared by some commentators to Longcat.

In a 2019 interview, Longcat's owner said that the cat was "originally rescued after being discovered on the street in 2002", and at the time was thin with gray hair; as she grew older, she became white and fluffy. The cat was deaf. In 2019, Longcat's owner said that, at the age of 17, the cat no longer "climbed to high places" but was "relaxing and living her life".

In September 2020, after a period of ill health, Longcat was taken to the hospital, and died at the age of 18.

🔗 Aviation 🔗 Russia 🔗 Military history 🔗 Disaster management 🔗 Aviation/Aviation accident 🔗 Death 🔗 Ukraine 🔗 Netherlands 🔗 Military history/Russian, Soviet and CIS military history 🔗 Malaysia

Malaysia Airlines Flight 17 (MH17/MAS17) was a scheduled passenger flight from Amsterdam to Kuala Lumpur that was shot down on 17 July 2014 while flying over eastern Ukraine. All 283 passengers and 15 crew were killed. Contact with the aircraft, a Boeing 777-200ER, was lost when it was about 50 km (31 mi) from the Ukraine–Russia border, and wreckage of the aircraft fell near Hrabove in Donetsk Oblast, Ukraine, 40 km (25 mi) from the border. The shoot-down occurred in the War in Donbas in an area controlled by pro-Russian rebels.

The responsibility for investigation was delegated to the Dutch Safety Board (DSB) and the Dutch-led joint investigation team (JIT), who concluded that the airliner was downed by a Buk surface-to-air missile launched from pro-Russian separatist-controlled territory in Ukraine. According to the JIT, the Buk that was used originated from the 53rd Anti-Aircraft Missile Brigade of the Russian Federation and had been transported from Russia on the day of the crash, fired from a field in a rebel-controlled area and the launch system returned to Russia afterwards. The findings by the DSB and JIT are consistent with the earlier claims by American and German intelligence sources and claims by the Ukrainian government. On the basis of the JIT's conclusions, the governments of the Netherlands and Australia held Russia responsible for the deployment of the Buk installation and were pursuing legal routes as of May 2018. The Russian government denied involvement in the shooting down of the airplane, and its account of how the aircraft was shot down has varied over time. Coverage in Russian media has also differed from that in other countries.

This was Malaysia Airlines' second aircraft loss during 2014, after the disappearance of Flight 370 on 8 March, and is the deadliest airliner shoot-down incident to date.

🔗 Languages 🔗 Constructed languages

Solresol (Solfège: Sol-Re-Sol) is a constructed language devised by François Sudre, beginning in 1827. His major book on it, Langue Musicale Universelle, was published after his death in 1866, though he had already been publicizing it for some years. Solresol enjoyed a brief spell of popularity, reaching its pinnacle with Boleslas Gajewski's 1902 publication of Grammaire du Solresol. An ISO 639-3 language code had been requested on 28 July 2017, but was rejected on 1 February 2018.

Today, there exist small communities of Solresol enthusiasts scattered across the world, able to communicate with one another thanks to the Internet.

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Contemporary philosophy 🔗 Philosophy/Ancient philosophy 🔗 Philosophy/Philosophy of mind 🔗 Philosophy/Modern philosophy 🔗 Philosophy/Metaphysics 🔗 Philosophy/Analytic philosophy 🔗 Folklore

In the metaphysics of identity, the ship of Theseus is a thought experiment that raises the question of whether an object that has had all of its components replaced remains fundamentally the same object. The concept is one of the oldest in Western philosophy, having been discussed by the likes of Heraclitus and Plato by ca. 500-400 BC.

🔗 New York (state) 🔗 Numismatics 🔗 Numismatics/American currency

The Ithaca HOUR is a local currency formerly used in Ithaca, New York and was one of the longest-running local currency systems, though it is now no longer in circulation. It has inspired other similar systems in Madison, Wisconsin; Santa Barbara, California; Corvallis, Oregon; and a proposed system in the Lehigh Valley, Pennsylvania. One Ithaca HOUR is valued at US$10 and is generally recommended to be used as payment for one hour's work, although the rate is negotiable.

🔗 United States 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Korea 🔗 Military history/Maritime warfare 🔗 Ships 🔗 Pritzker Military Library 🔗 Korea/North Korea 🔗 United States/Colorado

USS Pueblo (AGER-2) is a Banner-class environmental research ship, attached to Navy intelligence as a spy ship, which was attacked and captured by North Korean forces on 23 January 1968, in what is known today as the "Pueblo incident" or alternatively, as the "Pueblo crisis".

The seizure of the U.S. Navy ship and her 83 crew members, one of whom was killed in the attack, came less than a week after President Lyndon B. Johnson's State of the Union address to the United States Congress, a week before the start of the Tet Offensive in South Vietnam during the Vietnam War and three days after 31 men of North Korea's KPA Unit 124 had crossed the Korean Demilitarized Zone (DMZ) and killed 26 South Koreans in an attempt to attack the South Korean Blue House (executive mansion) in the capital Seoul. The taking of Pueblo and the abuse and torture of her crew during the subsequent 11-month prisoner drama became a major Cold War incident, raising tensions between western and eastern powers.

North Korea stated that Pueblo deliberately entered their territorial waters 7.6 nautical miles (14 km) away from Ryo Island, and that the logbook shows that they intruded several times. However, the United States maintains that the vessel was in international waters at the time of the incident and that any purported evidence supplied by North Korea to support its statements was fabricated. Pueblo, still held by North Korea today, officially remains a commissioned vessel of the United States Navy. Since early 2013, the ship has been moored along the Pothong River in Pyongyang and used there as a museum ship at the Victorious War Museum. Pueblo is the only ship of the U.S. Navy still on the commissioned roster currently being held captive.

🔗 Mathematics 🔗 Geography

The haversine formula determines the great-circle distance between two points on a sphere given their longitudes and latitudes. Important in navigation, it is a special case of a more general formula in spherical trigonometry, the law of haversines, that relates the sides and angles of spherical triangles.

The first table of haversines in English was published by James Andrew in 1805, but Florian Cajori credits an earlier use by José de Mendoza y Ríos in 1801. The term haversine was coined in 1835 by James Inman.

These names follow from the fact that they are customarily written in terms of the haversine function, given by hav(θ) = sin²(θ/2). The formulas could equally be written in terms of any multiple of the haversine, such as the older versine function (twice the haversine). Prior to the advent of computers, the elimination of division and multiplication by factors of two proved convenient enough that tables of haversine values and logarithms were included in nineteenth and early twentieth century navigation and trigonometric texts. These days, the haversine form is also convenient in that it has no coefficient in front of the sin² function.

🔗 Systems 🔗 Systems/Control theory

In control theory, a bang–bang controller (2 step or on–off controller), also known as a hysteresis controller, is a feedback controller that switches abruptly between two states. These controllers may be realized in terms of any element that provides hysteresis. They are often used to control a plant that accepts a binary input, for example a furnace that is either completely on or completely off. Most common residential thermostats are bang–bang controllers. The Heaviside step function in its discrete form is an example of a bang–bang control signal. Due to the discontinuous control signal, systems that include bang–bang controllers are variable structure systems, and bang–bang controllers are thus variable structure controllers.