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🔗 Biography 🔗 Russia 🔗 Mathematics 🔗 Biography/science and academia 🔗 Russia/science and education in Russia

Grigori Yakovlevich Perelman (Russian: Григорий Яковлевич Перельман, IPA: [ɡrʲɪˈɡorʲɪj ˈjakəvlʲɪvʲɪtɕ pʲɪrʲɪlʲˈman] (listen); born 13 June 1966) is a Russian mathematician who is known for his contributions to the fields of geometric analysis, Riemannian geometry, and geometric topology.

In the 1990s, partly in collaboration with Yuri Burago, Mikhael Gromov, and Anton Petrunin, he made influential contributions to the study of Alexandrov spaces. In 1994, he proved the soul conjecture in Riemannian geometry, which had been an open problem for the previous 20 years. In 2002 and 2003, he developed new techniques in the analysis of Ricci flow, thereby providing a detailed sketch of a proof of the Poincaré conjecture and Thurston's geometrization conjecture, the former of which had been a famous open problem in mathematics for the past century. The full details of Perelman's work were filled in and explained by various authors over the following several years.

In August 2006, Perelman was offered the Fields Medal for "his contributions to geometry and his revolutionary insights into the analytical and geometric structure of the Ricci flow", but he declined the award, stating: "I'm not interested in money or fame; I don't want to be on display like an animal in a zoo." On 22 December 2006, the scientific journal Science recognized Perelman's proof of the Poincaré conjecture as the scientific "Breakthrough of the Year", the first such recognition in the area of mathematics.

On 18 March 2010, it was announced that he had met the criteria to receive the first Clay Millennium Prize for resolution of the Poincaré conjecture. On 1 July 2010, he rejected the prize of one million dollars, saying that he considered the decision of the board of the Clay Institute to be unfair, in that his contribution to solving the Poincaré conjecture was no greater than that of Richard S. Hamilton, the mathematician who pioneered the Ricci flow partly with the aim of attacking the conjecture. He had previously rejected the prestigious prize of the European Mathematical Society, in 1996.

🔗 Physics 🔗 Astronomy 🔗 Geology 🔗 Mythology 🔗 Iceland 🔗 Norse history and culture 🔗 Mythology/Norse mythology

The sunstone (Icelandic: sólarsteinn) is a type of mineral attested in several 13th–14th-century written sources in Iceland, one of which describes its use to locate the Sun in a completely overcast sky. Sunstones are also mentioned in the inventories of several churches and one monastery in 14th–15th-century Iceland and Germany.

A theory exists that the sunstone had polarizing attributes and was used as a navigational instrument by seafarers in the Viking Age. A stone found in 2002 off Alderney, in the wreck of a 16th-century warship, may lend evidence of the existence of sunstones as navigational devices.

🔗 Business 🔗 Psychology 🔗 Marketing & Advertising 🔗 Sociology 🔗 Media 🔗 Retailing 🔗 Home Living

Overchoice or choice overload is the paradoxical phenomenon that choosing between a large variety of options can be detrimental to decision making processes. The term was first introduced by Alvin Toffler in his 1970 book, Future Shock.

The photoacoustic effect or optoacoustic effect is the formation of sound waves following light absorption in a material sample. In order to obtain this effect the light intensity must vary, either periodically (modulated light) or as a single flash (pulsed light). The photoacoustic effect is quantified by measuring the formed sound (pressure changes) with appropriate detectors, such as microphones or piezoelectric sensors. The time variation of the electric output (current or voltage) from these detectors is the photoacoustic signal. These measurements are useful to determine certain properties of the studied sample. For example, in photoacoustic spectroscopy, the photoacoustic signal is used to obtain the actual absorption of light in either opaque or transparent objects. It is useful for substances in extremely low concentrations, because very strong pulses of light from a laser can be used to increase sensitivity and very narrow wavelengths can be used for specificity. Furthermore, photoacoustic measurements serve as a valuable research tool in the study of the heat evolved in photochemical reactions (see: photochemistry), particularly in the study of photosynthesis.

Most generally, electromagnetic radiation of any kind can give rise to a photoacoustic effect. This includes the whole range of electromagnetic frequencies, from gamma radiation and X-rays to microwave and radio. Still, much of the reported research and applications, utilizing the photoacoustic effect, is concerned with the near ultraviolet/visible and infrared spectral regions.

🔗 Soviet Union 🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Spaceflight 🔗 Dogs 🔗 Russia/science and education in Russia 🔗 Russia/history of Russia

Laika (Russian: Лайка; c. 1954 – 3 November 1957) was a Soviet space dog who was one of the first animals in space and the first to orbit the Earth. A stray mongrel from the streets of Moscow, she flew aboard the Sputnik 2 spacecraft, launched into low orbit on 3 November 1957. As the technology to de-orbit had not yet been developed, Laika's survival was never expected. She died of overheating hours into the flight, on the craft's fourth orbit.

Little was known about the impact of spaceflight on living creatures at the time of Laika's mission, and animal flights were viewed by engineers as a necessary precursor to human missions. The experiment, which monitored Laika's vital signs, aimed to prove that a living organism could survive being launched into orbit and continue to function under conditions of weakened gravity and increased radiation, providing scientists with some of the first data on the biological effects of spaceflight.

Laika died within hours from overheating, possibly caused by a failure of the central R‑7 sustainer to separate from the payload. The true cause and time of her death were not made public until 2002; instead, it was widely reported that she died when her oxygen ran out on day six or, as the Soviet government initially claimed, she was euthanised prior to oxygen depletion. In 2008, a small monument to Laika depicting her standing atop a rocket was unveiled near the military research facility in Moscow that prepared her flight. She also appears on the Monument to the Conquerors of Space in Moscow.

🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Software

On the x86 computer architecture, a triple fault is a special kind of exception generated by the CPU when an exception occurs while the CPU is trying to invoke the double fault exception handler, which itself handles exceptions occurring while trying to invoke a regular exception handler.

x86 processors beginning with the 80286 will cause a shutdown cycle to occur when a triple fault is encountered. This typically causes the motherboard hardware to initiate a CPU reset, which, in turn, causes the whole computer to reboot.

🔗 Crime 🔗 Books

Hit Man: A Technical Manual for Independent Contractors is a book written under the pseudonym Rex Feral (real name Nancy Crampton-Brophy) and published by Paladin Press in 1983. Paladin Press owner Peder Lund claimed, in an interview with 60 Minutes, that the book started life as a detailed crime novel written by a Florida housewife, and that the format was later changed to appeal to Paladin's reader base accustomed to the publisher's non-fiction books on military, survivalist, weapons and similar topics. The book portrays itself as a how-to manual on starting a career as a hit man, fulfilling contracts. However, after a number of lawsuits claiming that the book was used as a handbook in several murders, the publication of the book was stopped. It marked "the first time in American publishing history that a publisher has been held liable for a crime committed by a reader."

🔗 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.

🔗 Technology

A moving walkway, also known as an autowalk, moving sidewalk, moving pavement, people-mover, travolator, or travelator, is a slow-moving conveyor mechanism that transports people across a horizontal or inclined plane over a short to medium distance. Moving walkways can be used by standing or walking on them. They are often installed in pairs, one for each direction.

🔗 Psychology 🔗 Education

Bloom's taxonomy is a set of three hierarchical models used to classify educational learning objectives into levels of complexity and specificity. The three lists cover the learning objectives in cognitive, affective and sensory domains. The cognitive domain list has been the primary focus of most traditional education and is frequently used to structure curriculum learning objectives, assessments and activities.

The models were named after Benjamin Bloom, who chaired the committee of educators that devised the taxonomy. He also edited the first volume of the standard text, Taxonomy of Educational Objectives: The Classification of Educational Goals.