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🔗 Philosophy 🔗 Greece 🔗 Cognitive science 🔗 Philosophy/Ancient philosophy 🔗 Alternative Views 🔗 Philosophy/Epistemology

The Allegory of the Cave, or Plato's Cave, is an allegory presented by the Greek philosopher Plato in his work Republic (514a–520a) to compare "the effect of education (παιδεία) and the lack of it on our nature". It is written as a dialogue between Plato's brother Glaucon and his mentor Socrates, narrated by the latter. The allegory is presented after the analogy of the sun (508b–509c) and the analogy of the divided line (509d–511e).

In the allegory "The Cave", Plato describes a group of people who have lived chained to the wall of a cave all their lives, facing a blank wall. The people watch shadows projected on the wall from objects passing in front of a fire behind them and give names to these shadows. The shadows are the prisoners' reality, but are not accurate representations of the real world. The shadows represent the fragment of reality that we can normally perceive through our senses, while the objects under the sun represent the true forms of objects that we can only perceive through reason. Three higher levels exist: the natural sciences; mathematics, geometry, and deductive logic; and the theory of forms.

Socrates explains how the philosopher is like a prisoner who is freed from the cave and comes to understand that the shadows on the wall are actually not the direct source of the images seen. A philosopher aims to understand and perceive the higher levels of reality. However, the other inmates of the cave do not even desire to leave their prison, for they know no better life.

Socrates remarks that this allegory can be paired with previous writings, namely the analogy of the sun and the analogy of the divided line.

🔗 Environment 🔗 Energy

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power.

Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, wind) and other renewables, or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand. The reservoirs used with pumped storage can be quite small when contrasted with the lakes of conventional hydroelectric plants of similar power capacity, and generating periods are often less than half a day.

The round-trip efficiency of PSH generally varies between 70%–80%. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020, PSH accounts for around 95% of all active storage installations worldwide, with a total installed throughput capacity of over 181 GW and a total installed storage capacity of over 1.6 TWh.

The main requirement for PSH is hilly country. The global greenfield pumped hydro atlas lists more than 600,000 potential sites around the world, which is about 100 times more than needed to support 100% renewable electricity. Most are closed-loop systems away from rivers. Areas of natural beauty and new dams on rivers can be avoided because of the very large number of potential sites. Some projects utilise existing reservoirs (dubbed "bluefield") such as the 350 Gigawatt-hour Snowy 2.0 scheme under construction in Australia. Some recently proposed projects propose to take advantage of "brownfield" locations such as disused mines such as the Kidston project under construction in Australia.

Water requirements for PSH are small: about 1 gigalitre of initial fill water per gigawatt-hour of storage. This water is recycled uphill and back downhill between the two reservoirs for many decades, but evaporation losses (beyond what rainfall and any inflow from local waterways provide) must be replaced. Land requirements are also small: about 10 hectares per gigawatt-hour of storage, which is much smaller than the land occupied by the solar and windfarms that the storage might support. Closed loop (off-river) pumped hydro storage has the smallest carbon emissions per unit of storage of all candidates for large-scale energy storage.

🔗 Medicine

Pyrotherapy (artificial fever) is a method of treatment by raising the body temperature or sustaining an elevated body temperature using a fever. In general, the body temperature was maintained at 41 °C (105 °F). Many diseases were treated by this method in the first half of the 20th century. In general, it was done by exposing the patient to hot baths, warm air, or (electric) blankets. The technique reached its peak of sophistication in the early 20th century with malariotherapy, in which Plasmodium vivax, a causative agent of malaria, was allowed to infect already ill patients in order to produce intense fever for therapeutic ends. The sophistication of this approach lay in using effective anti-malarial drugs to control the P. vivax infection, while maintaining the fever it causes to the detriment of other, ongoing, and then-incurable infections present in the patient, such as late-stage syphilis. This type of pyrotherapy was most famously used by psychiatrist Julius Wagner-Jauregg, who won the Nobel Prize for Medicine in 1927 for his elaboration of the procedure in treating neurosyphilitics.

🔗 Computing 🔗 Caribbean 🔗 Caribbean/Aruba 🔗 Caribbean/Curaçao 🔗 Caribbean/Caribbean Netherlands

.an was the Internet country code top-level domain (ccTLD) for the former Netherlands Antilles. It was administered by the University of the Netherlands Antilles. The domain was phased out after the Netherlands Antilles were dissolved in 2010. As of November 2010 the .an domain remained live with over 800 domains registered under .an, including secondary levels. On 31 July 2015, use of the domain was discontinued.

🔗 Ships

A sea anchor (also known as a parachute anchor, drift anchor, drift sock, para-anchor or boat brake) is a device that is streamed from a boat in heavy weather. Its purpose is to stabilize the vessel and to limit progress through the water. Rather than tethering the boat to the seabed with a conventional anchor, a sea anchor provides hydrodynamic drag, thereby acting as a brake. Normally attached to a vessel's bows, a sea anchor can prevent the vessel from turning broadside to the waves and being overwhelmed by them.

Early sea anchors were crude devices, but today most take the form of a marine drogue parachute. These are so efficient that they need a tripping line to collapse the parachute for retrieval. Being made of fabric, a sea parachute may be bagged and easily stowed when not in use.

A similar device to the sea anchor is the much smaller drogue, which is streamed from a vessel's stern in strong winds so as to slow the boat to prevent pitchpoling or broaching in an overtaking sea. The fundamental difference between the sea anchor and the drogue is that the drogue will slow the boat while keeping the heading steady, and is intended to be launched from the stern. The parachute anchor is designed to be launched from the bow and effectively stop the boat's progress relative to the current in an open sea.

🔗 United States 🔗 Food and drink 🔗 Correction and Detention Facilities

Nutraloaf (also known as Meal Loaf, prison loaf, disciplinary loaf, food loaf, lockup loaf, confinement loaf, seg loaf, grue or special management meal) is a food served in prisons in the United States and formerly Canada to inmates who have misbehaved; for example, assaulting prison guards or fellow prisoners. It is similar to meatloaf in texture, but has a wider variety of ingredients. Prison loaf is usually bland, perhaps even unpleasant, but prison wardens argue that nutraloaf provides enough nutrition to keep prisoners healthy without requiring utensils to be issued.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Military history/French military history 🔗 Military history/Cold War 🔗 Rocketry 🔗 Military history/European military history

The S3 was a French land-based Intermediate Range Ballistic Missile, equipped with a single 1.2-megatonne thermonuclear warhead. In France it is called an SSBS, for Sol-Sol Balistique Stratégique, or Ground-Ground Strategic Ballistic Missile.

🔗 Italy 🔗 Cryptography 🔗 Cryptography/Computer science

The Vigenère cipher (French pronunciation: ​[viʒnɛːʁ]) is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution.

First described by Giovan Battista Bellaso in 1553, the cipher is easy to understand and implement, but it resisted all attempts to break it until 1863, three centuries later. This earned it the description le chiffre indéchiffrable (French for 'the indecipherable cipher'). Many people have tried to implement encryption schemes that are essentially Vigenère ciphers. In 1863, Friedrich Kasiski was the first to publish a general method of deciphering Vigenère ciphers.

In the 19th century the scheme was misattributed to Blaise de Vigenère (1523–1596), and so acquired its present name.

🔗 Education

Forest kindergarten is a type of preschool education for children between the ages of three and six that is held almost exclusively outdoors. Whatever the weather, children are encouraged to play, explore and learn in a forest environment. The adult supervision is meant to assist rather than lead. It is also known as Waldkindergarten (in German), outdoor nursery, or nature kindergarten.