Topic: Russia/science and education in Russia (Page 2)

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๐Ÿ”— Alexey Chervonenkis found dead

๐Ÿ”— Biography ๐Ÿ”— Russia ๐Ÿ”— Statistics ๐Ÿ”— Biography/science and academia ๐Ÿ”— Russia/science and education in Russia

Alexey Yakovlevich Chervonenkis (Russian: ะะปะตะบัะตะน ะฏะบะพะฒะปะตะฒะธั‡ ะงะตั€ะฒะพะฝะตะฝะบะธั; 7 September 1938 โ€“ 22 September 2014) was a Soviet and Russian mathematician, and, with Vladimir Vapnik, was one of the main developers of the Vapnikโ€“Chervonenkis theory, also known as the "fundamental theory of learning" an important part of computational learning theory. Chervonenkis held joint appointments with the Russian Academy of Sciences and Royal Holloway, University of London.

Alexey Chervonenkis got lost in Losiny Ostrov National Park on 22 September 2014, and later during a search operation was found dead near Mytishchi, a suburb of Moscow. He had died of hypothermia.

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๐Ÿ”— MARS-500

๐Ÿ”— Russia ๐Ÿ”— Russia/technology and engineering in Russia ๐Ÿ”— Spaceflight ๐Ÿ”— Europe ๐Ÿ”— China ๐Ÿ”— Russia/science and education in Russia ๐Ÿ”— Europe/ESA ๐Ÿ”— Solar System/Mars ๐Ÿ”— Solar System

The Mars-500 mission was a psychosocial isolation experiment conducted between 2007 and 2011 by Russia, the European Space Agency and China, in preparation for an unspecified future crewed spaceflight to the planet Mars. The experiment's facility was located at the Russian Academy of Sciences' Institute of Biomedical Problems (IBMP) in Moscow, Russia.

Between 2007 and 2011, three different crews of volunteers lived and worked in a mock-up spacecraft at IBMP. The final stage of the experiment, which was intended to simulate a 520-day crewed mission, was conducted by an all-male crew consisting of three Russians (Alexey Sitev, Sukhrob Kamolov, Alexander Smoleevskij), a Frenchman (Romain Charles), an Italian (Diego Urbina) and a Chinese citizen (Yue Wang). The mock-up facility simulated an Earth-Mars shuttle spacecraft, an ascent-descent craft, and the Martian surface. The volunteers who participated in the three stages included professionals with experience in engineering, medicine, biology, and human spaceflight. The experiment yielded important data on the physiological, social and psychological effects of long-term close-quarters isolation.

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๐Ÿ”— Tennis racket theorem โ€“ Wikipedia

๐Ÿ”— Russia ๐Ÿ”— Physics ๐Ÿ”— Russia/science and education in Russia

The tennis racket theorem or intermediate axis theorem is a result in classical mechanics describing the movement of a rigid body with three distinct principal moments of inertia. It is also dubbed the Dzhanibekov effect, after Russian cosmonaut Vladimir Dzhanibekov who noticed one of the theorem's logical consequences while in space in 1985 although the effect was already known for at least 150 years before that.

The theorem describes the following effect: rotation of an object around its first and third principal axes is stable, while rotation around its second principal axis (or intermediate axis) is not.

This can be demonstrated with the following experiment: hold a tennis racket at its handle, with its face being horizontal, and try to throw it in the air so that it will perform a full rotation around the horizontal axis perpendicular to the handle, and try to catch the handle. In almost all cases, during that rotation the face will also have completed a half rotation, so that the other face is now up. By contrast, it is easy to throw the racket so that it will rotate around the handle axis (the third principal axis) without accompanying half-rotation around another axis; it is also possible to make it rotate around the vertical axis perpendicular to the handle (the first principal axis) without any accompanying half-rotation.

The experiment can be performed with any object that has three different moments of inertia, for instance with a book, remote control or smartphone. The effect occurs whenever the axis of rotation differs only slightly from the object's second principal axis; air resistance or gravity are not necessary.

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๐Ÿ”— Domesticated Silver Fox

๐Ÿ”— Russia ๐Ÿ”— Dogs ๐Ÿ”— Russia/science and education in Russia ๐Ÿ”— Genetics

The domesticated silver fox is a form of the silver fox that has been to some extent domesticated under laboratory conditions. The silver fox is a melanistic form of the wild red fox. Domesticated silver foxes are the result of an experiment designed to demonstrate the power of selective breeding to transform species, as described by Charles Darwin in On the Origin of Species. The experiment at the Institute of Cytology and Genetics in Novosibirsk, Siberia explored whether selection for behaviour rather than morphology may have been the process that had produced dogs from wolves, by recording the changes in foxes when in each generation only the most tame foxes were allowed to breed. Many of the descendant foxes became both tamer and more dog-like in morphology, including displaying mottled or spotted coloured fur.

In 2019, an international research team questioned the conclusion that this experiment had provided strong support for the validity of domestication syndrome. They did conclude that it remains "a resource for investigation of the genomics and biology of behavior".

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๐Ÿ”— Gaussโ€“Markov theorem

๐Ÿ”— Russia ๐Ÿ”— Mathematics ๐Ÿ”— Statistics ๐Ÿ”— Russia/science and education in Russia

In statistics, the Gaussโ€“Markov theorem states that the ordinary least squares (OLS) estimator has the lowest sampling variance within the class of linear unbiased estimators, if the errors in the linear regression model are uncorrelated, have equal variances and expectation value of zero. The errors do not need to be normal, nor do they need to be independent and identically distributed (only uncorrelated with mean zero and homoscedastic with finite variance). The requirement that the estimator be unbiased cannot be dropped, since biased estimators exist with lower variance. See, for example, the Jamesโ€“Stein estimator (which also drops linearity) or ridge regression.

The theorem was named after Carl Friedrich Gauss and Andrey Markov, although Gauss' work significantly predates Markov's. But while Gauss derived the result under the assumption of independence and normality, Markov reduced the assumptions to the form stated above. A further generalization to non-spherical errors was given by Alexander Aitken.

๐Ÿ”— Sputnik is 60 today

๐Ÿ”— Soviet Union ๐Ÿ”— Russia ๐Ÿ”— Russia/technology and engineering in Russia ๐Ÿ”— Spaceflight ๐Ÿ”— Russia/science and education in Russia ๐Ÿ”— Russia/history of Russia

Sputnik 1 ( or ; "Satellite-1", or "PS-1", ะŸั€ะพัั‚ะตะนัˆะธะน ะกะฟัƒั‚ะฝะธะบ-1 or Prosteyshiy Sputnik-1, "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957, orbiting for three weeks before its batteries died, then silently for two more months before falling back into the atmosphere. It was a 58ย cm (23ย in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable by radio amateurs, and the 65ยฐ inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. The satellite's unanticipated success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War. The launch was the beginning of a new era of political, military, technological, and scientific developments. The name "Sputnik" is Russian for spouse/traveling companion or satellite when interpreted in an astronomical context.

Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data about the ionosphere.

Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR (now known as the Baikonur Cosmodrome). The satellite travelled at about 29,000 kilometres per hour (18,000ย mph; 8,100ย m/s), taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 21 days until the transmitter batteries ran out on 26 October 1957. Sputnik burned up on 4 January 1958 while reentering Earth's atmosphere, after three months, 1440 completed orbits of the Earth, and a distance travelled of about 70ย millionย km (43ย millionย mi).

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๐Ÿ”— Cherenkov radiation โ€“ Faster then light in water

๐Ÿ”— Russia ๐Ÿ”— Russia/technology and engineering in Russia ๐Ÿ”— Physics ๐Ÿ”— Physics/relativity ๐Ÿ”— Russia/science and education in Russia

Cherenkov radiation (; Russian: ะญั„ั„ะตะบั‚ ะ’ะฐะฒะธะปะพะฒะฐ โ€” ะงะตั€ะตะฝะบะพะฒะฐ, Vavilov-Cherenkov effect) is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity (speed of propagation of a wavefront in a medium) of light in that medium. A classic example of Cherenkov radiation is the characteristic blue glow of an underwater nuclear reactor. Its cause is similar to the cause of a sonic boom, the sharp sound heard when faster-than-sound movement occurs. The phenomenon is named after Soviet physicist Pavel Cherenkov.

๐Ÿ”— Novikov Self-Consistency Principle

๐Ÿ”— Russia ๐Ÿ”— Physics ๐Ÿ”— Physics/relativity ๐Ÿ”— Russia/science and education in Russia

The Novikov self-consistency principle, also known as the Novikov self-consistency conjecture and Larry Niven's law of conservation of history, is a principle developed by Russian physicist Igor Dmitriyevich Novikov in the mid-1980s. Novikov intended it to solve the problem of paradoxes in time travel, which is theoretically permitted in certain solutions of general relativity that contain what are known as closed timelike curves. The principle asserts that if an event exists that would cause a paradox or any "change" to the past whatsoever, then the probability of that event is zero. It would thus be impossible to create time paradoxes.

๐Ÿ”— The Tunguska Event

๐Ÿ”— Soviet Union ๐Ÿ”— Russia ๐Ÿ”— Disaster management ๐Ÿ”— Skepticism ๐Ÿ”— Astronomy ๐Ÿ”— Russia/science and education in Russia ๐Ÿ”— Geology ๐Ÿ”— Russia/physical geography of Russia ๐Ÿ”— Russia/history of Russia ๐Ÿ”— Paranormal

The Tunguska event was a massive ~12 megaton explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of June 30, 1908. The explosion over the sparsely populated Eastern Siberian Taiga flattened an estimated 80ย million trees over an area of 2,150ย km2 (830ย sqย mi) of forest, and eyewitness reports suggest that at least three people may have died in the event. The explosion is generally attributed to the air burst of a stony meteoroid about 50โ€“60 metres (160โ€“200 feet) in size.:โ€Šp. 178โ€Š The meteoroid approached from the east-southeast, and likely with a relatively high speed of about 27 km/s. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres (3 to 6 miles) rather than to have hit the surface of the Earth.

The Tunguska event is the largest impact event on Earth in recorded history, though much larger impacts have occurred in prehistoric times. An explosion of this magnitude would be capable of destroying a large metropolitan area. It has been mentioned numerous times in popular culture, and has also inspired real-world discussion of asteroid impact avoidance.