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🔗 Ships

The Voith Schneider propeller (VSP), also known as a cycloidal drive is a specialized marine propulsion system (MPS). It is highly maneuverable, being able to change the direction of its thrust almost instantaneously. It is widely used on tugs and ferries.

🔗 Physics 🔗 Geology

A fossil natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions have occurred. This can be examined by analysis of isotope ratios. The conditions under which a natural nuclear reactor could exist had been predicted in 1956 by Paul Kazuo Kuroda. The phenomenon was discovered in 1972 in Oklo, Gabon by French physicist Francis Perrin under conditions very similar to what was predicted.

Oklo is the only known location for this in the world and consists of 16 sites at which self-sustaining nuclear fission reactions are thought to have taken place approximately 1.7 billion years ago, and ran for a few hundred thousand years, averaging probably less than 100 kW of thermal power during that time.

🔗 Mathematics

The Banach–Tarski paradox is a theorem in set-theoretic geometry, which states the following: Given a solid ball in 3‑dimensional space, there exists a decomposition of the ball into a finite number of disjoint subsets, which can then be put back together in a different way to yield two identical copies of the original ball. Indeed, the reassembly process involves only moving the pieces around and rotating them without changing their shape. However, the pieces themselves are not "solids" in the usual sense, but infinite scatterings of points. The reconstruction can work with as few as five pieces.

A stronger form of the theorem implies that given any two "reasonable" solid objects (such as a small ball and a huge ball), the cut pieces of either one can be reassembled into the other. This is often stated informally as "a pea can be chopped up and reassembled into the Sun" and called the "pea and the Sun paradox".

The reason the Banach–Tarski theorem is called a paradox is that it contradicts basic geometric intuition. "Doubling the ball" by dividing it into parts and moving them around by rotations and translations, without any stretching, bending, or adding new points, seems to be impossible, since all these operations ought, intuitively speaking, to preserve the volume. The intuition that such operations preserve volumes is not mathematically absurd and it is even included in the formal definition of volumes. However, this is not applicable here because in this case it is impossible to define the volumes of the considered subsets. Reassembling them reproduces a volume, which happens to be different from the volume at the start.

Unlike most theorems in geometry, the proof of this result depends in a critical way on the choice of axioms for set theory. It can be proven using the axiom of choice, which allows for the construction of non-measurable sets, i.e., collections of points that do not have a volume in the ordinary sense, and whose construction requires an uncountable number of choices.

It was shown in 2005 that the pieces in the decomposition can be chosen in such a way that they can be moved continuously into place without running into one another.

🔗 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.

🔗 Lists 🔗 Buddhism

The Buddhist games list is a list of games that Gautama Buddha is reputed to have said that he would not play and that his disciples should likewise not play, because he believed them to be a 'cause for negligence'. This list dates from the 6th or 5th century BCE and is the earliest known list of games.

There is some debate about the translation of some of the games mentioned, and the list given here is based on the translation by T. W. Rhys Davids of the Brahmajāla Sutta and is in the same order given in the original. The list is duplicated in a number of other early Buddhist texts, including the Vinaya Pitaka.

1. Games on boards with 8 or 10 rows. This is thought to refer to ashtapada and dasapada respectively, but later Sinhala commentaries refer to these boards also being used with games involving dice.
2. The same games played on imaginary boards. Akasam astapadam was an ashtapada variant played with no board, literally "astapadam played in the sky". A correspondent in the American Chess Bulletin identifies this as likely the earliest literary mention of a blindfold chess variant.
3. Games of marking diagrams on the floor such that the player can only walk on certain places. This is described in the Vinaya Pitaka as "having drawn a circle with various lines on the ground, there they play avoiding the line to be avoided". Rhys Davids suggests that it may refer to parihāra-patham, a form of hop-scotch.
4. Games where players either remove pieces from a pile or add pieces to it, with the loser being the one who causes the heap to shake (similar to the modern game pick-up sticks).
5. Games of throwing dice.
6. "Dipping the hand with the fingers stretched out in lac, or red dye, or flour-water, and striking the wet hand on the ground or on a wall, calling out 'What shall it be?' and showing the form required—elephants, horses, &c."
7. Ball games.
8. Blowing through a pat-kulal, a toy pipe made of leaves.
9. Ploughing with a toy plough.
10. Playing with toy windmills made from palm leaves.
11. Playing with toy measures made from palm leaves.
12. Playing with toy carts.
13. Playing with toy bows.
14. Guessing at letters traced with the finger in the air or on a friend's back.
15. Guessing a friend's thoughts.
16. Imitating deformities.

Although the modern game of chess had not been invented at the time the list was made, earlier chess-like games such as chaturaji may have existed. H.J.R. Murray refers to Rhys Davids' 1899 translation, noting that the 8×8 board game is most likely ashtapada while the 10×10 game is dasapada. He states that both are race games.

🔗 Constructed languages

Lojban (pronounced [ˈloʒban] (listen)) is a constructed, syntactically unambiguous human language created by the Logical Language Group and succeeding the Loglan project.

The Logical Language Group (LLG) began developing Lojban in 1987. The LLG sought to realize Loglan's purposes, and further improve the language by making it more usable and freely available (as indicated by its official full English title, "Lojban: A Realization of Loglan"). After a long initial period of debating and testing, the baseline was completed in 1997, and published as The Complete Lojban Language. In an interview in 2010 with The New York Times, Arika Okrent, the author of In the Land of Invented Languages, stated: "The constructed language with the most complete grammar is probably Lojban—a language created to reflect the principles of logic."

Lojban is proposed as a speakable language for communication between people of different language backgrounds, as a potential means of machine translation and to explore the intersection of human language and software.

🔗 Chess

Zugzwang (German for "compulsion to move", pronounced [ˈtsuːktsvaŋ]) is a situation found in chess and other turn-based games wherein one player is put at a disadvantage because they must make a move when they would prefer to pass and not move. The fact that the player is compelled to move means that their position will become significantly weaker. A player is said to be "in zugzwang" when any possible move will worsen their position.

Although the term is used less precisely in games such as chess, it is used specifically in combinatorial game theory to denote a move that directly changes the outcome of the game from a win to a loss. Putting the opponent in zugzwang is a common way to help the superior side win a game, and in some cases it is necessary in order to make the win possible.

The term zugzwang was used in German chess literature in 1858 or earlier, and the first known use of the term in English was by World Champion Emanuel Lasker in 1905. The concept of zugzwang was known to chess players many centuries before the term was coined, appearing in an endgame study published in 1604 by Alessandro Salvio, one of the first writers on the game, and in shatranj studies dating back to the early 9th century, over 1000 years before the first known use of the term.

Positions with zugzwang occur fairly often in chess endgames, especially in king and pawn endgames. According to John Nunn, positions of reciprocal zugzwang are surprisingly important in the analysis of endgames.

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Contemporary philosophy 🔗 Philosophy/Philosophy of religion 🔗 Christianity 🔗 Christianity/theology 🔗 Military history/European military history

Gödel's ontological proof is a formal argument by the mathematician Kurt Gödel (1906–1978) for the existence of God. The argument is in a line of development that goes back to Anselm of Canterbury (1033–1109). St. Anselm's ontological argument, in its most succinct form, is as follows: "God, by definition, is that for which no greater can be conceived. God exists in the understanding. If God exists in the understanding, we could imagine Him to be greater by existing in reality. Therefore, God must exist." A more elaborate version was given by Gottfried Leibniz (1646–1716); this is the version that Gödel studied and attempted to clarify with his ontological argument.

Gödel left a fourteen-point outline of his philosophical beliefs in his papers. Points relevant to the ontological proof include

4. There are other worlds and rational beings of a different and higher kind.

5. The world in which we live is not the only one in which we shall live or have lived.

13. There is a scientific (exact) philosophy and theology, which deals with concepts of the highest abstractness; and this is also most highly fruitful for science.

14. Religions are, for the most part, bad—but religion is not.

🔗 Computing 🔗 Computer science 🔗 Cognitive science 🔗 Software 🔗 Software/Computing 🔗 Databases 🔗 Databases/Computer science

Cyc (pronounced SYKE, ) is a long-living artificial intelligence project that aims to assemble a comprehensive ontology and knowledge base that spans the basic concepts and rules about how the world works. Hoping to capture common sense knowledge, Cyc focuses on implicit knowledge that other AI platforms may take for granted. This is contrasted with facts one might find somewhere on the internet or retrieve via a search engine or Wikipedia. Cyc enables AI applications to perform human-like reasoning and be less "brittle" when confronted with novel situations.

Douglas Lenat began the project in July 1984 at MCC, where he was Principal Scientist 1984–1994, and then, since January 1995, has been under active development by the Cycorp company, where he is the CEO.

🔗 International relations 🔗 Mass surveillance 🔗 Internet 🔗 History 🔗 Computing 🔗 Internet culture 🔗 Economics 🔗 Law 🔗 Business 🔗 Politics 🔗 International relations/International law 🔗 Sociology 🔗 Futures studies 🔗 Capitalism 🔗 Globalization 🔗 Google

Surveillance capitalism has a number of meanings around the commodification of personal information. Since 2014, social psychologist Shoshana Zuboff has used and popularized the term.