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Pole Star
A pole star or polar star is a star, preferably bright, nearly aligned with the axis of a rotating astronomical body. Currently, Earth's pole stars are Polaris (Alpha Ursae Minoris), a bright magnitude-2 star aligned approximately with its northern axis that serves as a pre-eminent star in celestial navigation, and a much dimmer magnitude-5.5 star on its southern axis, Polaris Australis (Sigma Octantis). From around 1700 BC until just after 300 AD, Kochab (Beta Ursae Minoris) and Pherkad (Gamma Ursae Minoris) were twin northern pole stars, though neither was as close to the pole as Polaris is now. History In classical antiquity, Beta Ursae Minoris (Kochab) was closer to the celestial north pole than Alpha Ursae Minoris. While there was no naked-eye star close to the pole, the midpoint between Alpha and Beta Ursae Minoris was reasonably close to the pole, and it appears that the entire constellation of Ursa Minor, in antiquity known as '' Cynosura'' (Greek Κυνό� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johannes Kepler
Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws of planetary motion, and his books '' Astronomia nova'', '' Harmonice Mundi'', and '' Epitome Astronomiae Copernicanae''. These works also provided one of the foundations for Newton's theory of universal gravitation. Kepler was a mathematics teacher at a seminary school in Graz, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to the astronomer Tycho Brahe in Prague, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He also taught mathematics in Linz, and was an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting (or Keplerian) telescop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thuban
Thuban (), with Bayer designation Alpha Draconis or α Draconis, is a binary star system in the northern constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star from the 4th to 2nd millennium BC. Johann Bayer gave Thuban the designation Alpha and placed it as the only member of his ''secundae'' magnitude class in Draco, although its current apparent magnitude of 3.65 means it is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), which Bayer placed in his ''tertiae'' magnitude class although its current apparent magnitude is 2.24. Nomenclature ''α Draconis'' ( Latinised to ''Alpha Draconis'') is the star's Bayer designation. The traditional name ''Thuban'' is derived from the Arabic word ' ('large snake' (e.g. a python or a legendary draconian serpent)). It is sometimes known as the ''Dragon's Tail'' and as ''Adib'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precession Of The Equinoxes
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particular, axial precession can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 26,000 years.Hohenkerk, C.Y., Yallop, B.D., Smith, C.A., & Sinclair, A.T. "Celestial Reference Systems" in Seidelmann, P.K. (ed.) ''Explanatory Supplement to the Astronomical Almanac''. Sausalito: University Science Books. p. 99. This is similar to the precession of a spinning top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis—nutation and polar motion—are much smaller in magnitude. Earth's precession was historically called the precession of the equinoxes, bec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambridge
Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge became an important trading centre during the Roman and Viking ages, and there is archaeological evidence of settlement in the area as early as the Bronze Age. The first town charters were granted in the 12th century, although modern city status was not officially conferred until 1951. The city is most famous as the home of the University of Cambridge, which was founded in 1209 and consistently ranks among the best universities in the world. The buildings of the university include King's College Chapel, Cavendish Laboratory, and the Cambridge University Library, one of the largest legal deposit libraries in the world. The city's skyline is dominated by several college buildings, along with the spire of the Our Lady and the English Martyrs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Lutterworth Press
The Lutterworth Press, one of the oldest independent British publishing houses, has traded since the late eighteenth century - initially as the Religious Tract Society (RTS). The Lutterworth imprint, named after the small English town of Lutterworth in Leicestershire, where John Wyclif served as Rector in the fourteenth century, has been used since 1932, and Lutterworth continued most of the then current RTS publications. The main areas have been religion, children's books and general adult non-fiction. The religious list, as with the RTS, tended to publish fairly evangelical writers, such as Norman Grubb, but gradually broadened in the second half of the twentieth century. Well-known general writers first published by Lutterworth include David Attenborough and Patrick Moore. The list specialises in popular history and art history, but also publishes books on a wide range of other subjects. The children's list, which built on the strength of the '' Boy's Own Paper'' and ''Gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epoch (astronomy)
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Declination
In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the celestial equator, along the hour circle passing through the point in question. The root of the word ''declination'' (Latin, ''declinatio'') means "a bending away" or "a bending down". It comes from the same root as the words ''incline'' ("bend foward") and ''recline'' ("bend backward"). In some 18th and 19th century astronomical texts, declination is given as ''North Pole Distance'' (N.P.D.), which is equivalent to 90 – (declination). For instance an object marked as declination −5 would have an N.P.D. of 95, and a declination of −90 (the south celestial pole) would have an N.P.D. of 180. Explanation Declination in astronomy is comparable to geographic latitude, projected onto the celestial sphere, and right ascension is l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Precession
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface is made up of the ocean, dwarfing Earth's polar ice, lakes, and rivers. The remaining 29% of Earth's surface is land, consisting of continents and islands. Earth's surface layer is formed of several slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth's liquid outer core generates the magnetic field that shapes the magnetosphere of the Earth, deflecting destructive solar winds. The atmosphere of the Earth consists mostly of nitrogen and oxygen. Greenhouse gases in the atmosphere like carbon dioxide (CO2) trap a part of the energy from the Sun close to the surface. Water vapor is widely present in the atmosphere and forms clouds that cover most of the planet. More solar energy is r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gemma Frisius
Gemma Frisius (; born Jemme Reinerszoon; December 9, 1508 – May 25, 1555) was a Frisian physician, mathematician, cartographer, philosopher, and instrument maker. He created important globes, improved the mathematical instruments of his day and applied mathematics in new ways to surveying and navigation. Gemma's rings, an astronomical instrument, are named after him. Along with Gerardus Mercator and Abraham Ortelius, Frisius is often considered one of the founders of the Netherlandish school of cartography, and significantly helped lay the foundations for the school's golden age (approximately 1570s–1670s). Biography Frisius was born in Dokkum, Friesland (present-day Netherlands), of poor parents who died when he was young. He moved to Groningen and later studied at the University of Leuven (Louvain), Belgium, beginning in 1525. He received the degree of MD in 1536 and remained on the faculty of medicine of Leuven for the rest of his life where, in addition to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dhruva
Dhruva (Sanskrit: ध्रुव, , lit. "''unshakeable, immovable, or fixed"'') was an ascetic devotee of Vishnu mentioned in the Vishnu Purana and the Bhagavata Purana. The Sanskrit term ''dhruva nakshatra'' (ध्रुव नक्षत्र, "polar star") has been used for Pole Star in the Mahabharata, personified as son of Uttānapāda and grandson of Manu, even though Polaris at the likely period of the recension of the text of the Mahabharata was still several degrees away from the celestial pole. Narrative Dhruva was born as son of the King Uttānapāda (the son of Svayambhuva Manu) and his wife Suniti. The king also had another son Uttama, born to his second queen Suruchi, who was the preferred object of his affection. Once, when Dhruva was a child of five years of age, he saw his younger brother, Uttama sitting on his father's lap at the King's throne. Suruchi, who was jealous of the older son from the first wife (since he - Dhruva - would be heir to throne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purana
Purana (; sa, , '; literally meaning "ancient, old"Merriam-Webster's Encyclopedia of Literature (1995 Edition), Article on Puranas, , page 915) is a vast genre of Indian literature about a wide range of topics, particularly about legends and other traditional lore. The Puranas are known for the intricate layers of symbolism depicted within their stories. Composed originally in Sanskrit and in other Indian languages,John Cort (1993), Purana Perennis: Reciprocity and Transformation in Hindu and Jaina Texts (Editor: Wendy Doniger), State University of New York Press, , pages 185-204 several of these texts are named after major Hindu gods such as Vishnu, Shiva, Brahma, and Adi Shakti. The Puranic genre of literature is found in both Hinduism and Jainism. The Puranic literature is encyclopedic, and it includes diverse topics such as cosmogony, cosmology, genealogies of gods, goddesses, kings, heroes, sages, and demigods, folk tales, pilgrimages, temples, medicine, astronomy, gra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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