Random Articles

Have a deep view into what people are curious about.

πŸ”— Hemispherical Combustion Chamber

πŸ”— Automobiles

A hemispherical combustion chamber is a type of combustion chamber in a reciprocating internal combustion engine with a domed cylinder head. An engine featuring this type of hemispherical chamber is known as a hemi engine.

πŸ”— Sweden Solar System

πŸ”— Astronomy πŸ”— Sweden πŸ”— Solar System πŸ”— Astronomy/Solar System

The Sweden Solar System is the world's largest permanent scale model of the Solar System. The Sun is represented by the Ericsson Globe in Stockholm, the largest hemispherical building in the world. The inner planets can also be found in Stockholm but the outer planets are situated northward in other cities along the Baltic Sea. The system was started by Nils Brenning and GΓΆsta Gahm and is on the scale of 1:20 million.

Discussed on

πŸ”— Sunflower (Mathematics)

πŸ”— Mathematics

In the mathematical fields of set theory and extremal combinatorics, a sunflower or Ξ” {\displaystyle \Delta } -system is a collection of sets whose pairwise intersection is constant. This constant intersection is called the kernel of the sunflower.

The main research question arising in relation to sunflowers is: under what conditions does there exist a large sunflower (a sunflower with many sets) in a given collection of sets? The Ξ” {\displaystyle \Delta } -lemma, sunflower lemma, and the ErdΕ‘s-Rado sunflower conjecture give successively weaker conditions which would imply the existence of a large sunflower in a given collection, with the latter being one of the most famous open problems of extremal combinatorics.

Discussed on

πŸ”— Uranium can be extracted from seawater in useful amounts

πŸ”— Energy πŸ”— Mining

Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2019 amounted to 53,656Β tonnes. Kazakhstan, Canada, and Australia were the top three uranium producers, respectively, and together account for 68% of world production. Other countries producing more than 1,000 tonnes per year included Namibia, Niger, Russia, Uzbekistan, the United States, and China. Nearly all of the world's mined uranium is used to power nuclear power plants.

Uranium is mined by in-situ leaching (57% of world production) or by conventional underground or open-pit mining of ores (43% of production). During in-situ mining, a leaching solution is pumped down drill holes into the uranium ore deposit where it dissolves the ore minerals. The uranium-rich fluid is then pumped back to the surface and processed to extract the uranium compounds from solution. In conventional mining, ores are processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, "yellowcake," which is sold on the uranium market as U3O8.

Discussed on

πŸ”— Noam Chomsky Passed Away

Avram Noam Chomsky (born December 7, 1928) is an American professor and public intellectual known for his work in linguistics, political activism, and social criticism. Sometimes called "the father of modern linguistics", Chomsky is also a major figure in analytic philosophy and one of the founders of the field of cognitive science. He is a laureate professor of linguistics at the University of Arizona and an institute professor emeritus at the Massachusetts Institute of Technology (MIT). Among the most cited living authors, Chomsky has written more than 150 books on topics such as linguistics, war, and politics. Ideologically, he aligns with anarcho-syndicalism and libertarian socialism.

Born to Ashkenazi Jewish immigrants in Philadelphia, Chomsky developed an early interest in anarchism from alternative bookstores in New York City. He studied at the University of Pennsylvania. During his postgraduate work in the Harvard Society of Fellows, Chomsky developed the theory of transformational grammar for which he earned his doctorate in 1955. That year he began teaching at MIT, and in 1957 emerged as a significant figure in linguistics with his landmark work Syntactic Structures, which played a major role in remodeling the study of language. From 1958 to 1959 Chomsky was a National Science Foundation fellow at the Institute for Advanced Study. He created or co-created the universal grammar theory, the generative grammar theory, the Chomsky hierarchy, and the minimalist program. Chomsky also played a pivotal role in the decline of linguistic behaviorism, and was particularly critical of the work of B. F. Skinner.

An outspoken opponent of U.S. involvement in the Vietnam War, which he saw as an act of American imperialism, in 1967 Chomsky rose to national attention for his anti-war essay "The Responsibility of Intellectuals". Becoming associated with the New Left, he was arrested multiple times for his activism and placed on President Richard Nixon's list of political opponents. While expanding his work in linguistics over subsequent decades, he also became involved in the linguistics wars. In collaboration with Edward S. Herman, Chomsky later articulated the propaganda model of media criticism in Manufacturing Consent, and worked to expose the Indonesian occupation of East Timor. His defense of unconditional freedom of speech, including that of Holocaust denial, generated significant controversy in the Faurisson affair of the 1980s. Chomsky's commentary on the Cambodian genocide and the Bosnian genocide also generated controversy. Since retiring from active teaching at MIT, he has continued his vocal political activism, including opposing the 2003 invasion of Iraq and supporting the Occupy movement. An anti-Zionist, Chomsky considers Israel's treatment of Palestinians to be worse than South African-style apartheid, and criticizes U.S. support for Israel.

Chomsky is widely recognized as having helped to spark the cognitive revolution in the human sciences, contributing to the development of a new cognitivistic framework for the study of language and the mind. Chomsky remains a leading critic of U.S. foreign policy, contemporary capitalism, U.S. involvement and Israel's role in the Israeli–Palestinian conflict, and mass media. Chomsky and his ideas are highly influential in the anti-capitalist and anti-imperialist movements. Since 2017, he has been Agnese Helms Haury Chair in the Agnese Nelms Haury Program in Environment and Social Justice at the University of Arizona.

Discussed on

πŸ”— Lockheed Bribery Scandals

πŸ”— United States πŸ”— Aviation πŸ”— Military history πŸ”— Military history/Military aviation πŸ”— Military history/North American military history πŸ”— Military history/United States military history πŸ”— Crime πŸ”— Business πŸ”— Politics πŸ”— Military history/German military history πŸ”— Military history/Dutch military history πŸ”— Japan πŸ”— Japan/Japanese military history πŸ”— Military history/Asian military history πŸ”— Military history/Japanese military history πŸ”— Military history/Italian military history πŸ”— Japan/Politics πŸ”— Military history/European military history

The Lockheed bribery scandals encompassed a series of bribes and contributions made by officials of U.S. aerospace company Lockheed from the late 1950s to the 1970s in the process of negotiating the sale of aircraft.

The scandal caused considerable political controversy in West Germany, Italy, the Netherlands and Japan. In the U.S., the scandal nearly led to Lockheed's downfall, as it was already struggling due to the commercial failure of the L-1011 TriStar airliner.

Discussed on

πŸ”— Fumifugium, or, The inconveniencie of the aer and smoak of London

πŸ”— Environment πŸ”— London πŸ”— History of Science

Fumifugium, or, The inconveniencie of the aer and smoak of London dissipated together with some remedies humbly proposed by J.E. esq. to His Sacred Majestie, and to the Parliament now assembled is a pamphlet published in London, 1661 (see 1661 in literature), by John Evelyn. It is one of the earliest known works on air pollution and is broken down into three parts which explain the problem, a proposed solution, and a way of improvement upon the air in London. The letter was specifically addressed to King Charles II of England and discussed problems with the capital's air pollution dating back to medieval times. Evelyn refers to Greek philosophers, who once believed that air was the principle of the earth and primary substance of the soul up until the time that air pollution began to cause ill health.

Evelyn was appointed to the newly formed Royal Society, and both Society and pamphlet are celebrated in the 1663 "Ballad of Gresham College". Stanza 23 (given here in modern English) describes how Evelyn

[...] shows that 'tis the sea-coal smoke

That always London does environ,
Which does our lungs and spirits choke,
Our hanging spoil, and rust our iron.
Let none at Fumifuge be scoffing

Who heard at Church our Sunday's coughing.

The sea-coal to which Evelyn referred was appropriately named because it came by sea from Newcastle. When burned, it gave off a terrible smell because of high amounts of sulfur in its composition. When burned the sea coal released sulfur dioxide, carbon dioxide, nitric oxide, soot, and particulates of organic matter into the atmosphere. The pamphlet suggests that burning wood, particularly aromatic woods, will be less harmful to the lungs and recommends relocating some of London's more polluting industries outside the capital, in particular lime-burning and brewing.

Discussed on

πŸ”— Body Doubling

πŸ”— Disability

Body doubling or parallel working is a strategy used to initiate and complete tasks, such as household chores or writing and other computer tasks. It involves the physical presence, virtual presence through a phone call, videotelephony or social media presence, of someone with whom one shares their goals, which makes it more likely to achieve them. For some people, it works best to both do similar tasks, while for others, just being in the same (virtual) room is enough.

It was partially popularized by those with attention deficit hyperactivity disorder (ADHD) to help manage symptoms. Its usefulness has also been noted by those with autism, but efficacy is not clearly known as long term studies have not been conducted on the topic. In 2023, J. Russel Ramsay, professor of clinical psychiatry at the Perelman School of Medicine and co-director of the ADHD treatment and research program of the University of Pennsylvania, noted that, while extensive research on the strategy's effect on productivity doesn't exist, "the idea of externalizing motivation is a longstanding evidence-based mechanism for managing ADHD."

ADHD body doubling comes into play allowing individuals with ADHD to perform and complete tasks more easily and with less distractions, where otherwise they might struggle more. "ADHD body doubling is a productivity strategy used by individuals with ADHD to finish possibly annoying jobs while having another person beside them."

Body doubling is said to aid individuals with focus and productivity while working. Another person, known as a 'body double' sits alongside the individual with ADHD to help them focus while completing a certain task. The role of this individual is to not partake in the task but, more importantly, serve as a support system and create a welcoming environment that allows the individual to focus by reducing any distractions. The idea of body doubling allows for specific reminders to the individual to stay on task which helps alleviate the symptoms of ADHD.

Discussed on

πŸ”— Great Britain road numbering scheme

πŸ”— Highways πŸ”— Road transport πŸ”— Transport in Scotland πŸ”— Highways/United Kingdom Roads πŸ”— UK geography

The Great Britain road numbering scheme is a numbering scheme used to classify and identify all roads in Great Britain. Each road is given a single letter, which represents the road's category, and a subsequent number, of 1 to 4 digits. Introduced to arrange funding allocations, the numbers soon became used on maps and as a method of navigation. Two sub-schemes exist: one for motorways, and another for non-motorway roads. While some major roads form part of the International E-road network, no E-routes are signposted in Great Britain, or the rest of the UK.

The scheme applies only to Great Britain (England, Scotland and Wales); a similar system is used in Northern Ireland, as well as outside the UK in the Isle of Man, Jersey and British overseas territories. These other numbering schemes use similar conventions.

Discussed on

πŸ”— Ask HN: using only static magnetism - impossible to stably levitate against gravity?

πŸ”— Mathematics πŸ”— Physics

Earnshaw's theorem states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges. This was first proven by British mathematician Samuel Earnshaw in 1842. It is usually referenced to magnetic fields, but was first applied to electrostatic fields.

Earnshaw's theorem applies to classical inverse-square law forces (electric and gravitational) and also to the magnetic forces of permanent magnets, if the magnets are hard (the magnets do not vary in strength with external fields). Earnshaw's theorem forbids magnetic levitation in many common situations.

If the materials are not hard, Braunbeck's extension shows that materials with relative magnetic permeability greater than one (paramagnetism) are further destabilising, but materials with a permeability less than one (diamagnetic materials) permit stable configurations.

Discussed on