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Yu Xi
Yu Xi (虞喜; 307–345 AD), courtesy name Zhongning (仲寧), was a Chinese astronomer and writer of the Jin dynasty (266–420 AD). He is best known for his discovery of the precession of the equinoxes, independently of the earlier ancient Greek astronomer Hipparchus. He also postulated that the Earth could be spherical in shape instead of being flat and square, long before the idea became widely accepted in Chinese science with the advances in circumnavigation by Europeans from the 16th-20th centuries, especially with their arrival into the capital's imperial court in the 17th century. Background and official career The life and works of Yu Xi are described in his biography found in the ''Book of Jin'', the official history of the Jin dynasty.Knechtges and Chang (2014), p. 2010. He was born in Yuyao, Guiji (modern Shaoxing, Zhejiang province, China). His father Yu Cha (虞察) was a military commander and his younger brother Yu Yu (虞預; fl. 307–329 AD) was likewise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yu (Chinese Surname)
Yu is the pinyin romanisation of several Chinese family names. However, in the Wade–Giles romanisation system, Yu is equivalent to You in pinyin. "Yu" may represent many different Chinese characters, including 余, 于, 由, 魚 (鱼), 漁(渔), 楀, 俞(兪), 喻 (this character is 35th name on the ''Hundred Family Surnames'' poem), 於, 遇, 虞, 郁, 尉, 禹, 游, 尤, 庾, 娛(娱), and 茹 (Rú). The most common of the Yu surnames are 于, 余, and 俞. In China, 0.62% of the population have the family name 于 in 2002 (about 7.4 million), and this surname is most common in Shandong province and northeastern China. Around 0.41% of the population have the surname 余 in 2002 (over five million), and it is most common in Jiangxi, Zhejiang and Fujian provinces. The 俞 surname represents around 0.12% of China's population. Surname Yu (于) Surname Yu (余) Surname Yu (俞) History Yu () is said to have been derived as a term used by medical practitioners Yu (腧) sinc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axial Precession
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, because ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Li Ye (mathematician)
Li Ye (; 1192–1279), born Li Zhi (), courtesy name Li Jingzhai (),Breard, Andrea. (Jan 01, 2021).Li Ye: Chinese mathematician. '' Encyclopaedia Britannica''. Accessed 7 February 2021.Li, Ye (1192-1279) 李, 冶 (1192-1279) IdRef: ''Identifiants et Référentials pour l'enseignement supérieur et la recherche'' (French). Accessed 19 February 2018. was a Chinese scientist and writer who published and improved the method for solving s of one variable. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flat Earth
The flat-Earth model is an archaic and scientifically disproven conception of Earth's shape as a plane or disk. Many ancient cultures subscribed to a flat-Earth cosmography, including Greece until the classical period (5th century BC), the Bronze and Iron Age civilizations of the Near East until the Hellenistic period (31 BC), and China until the 17th century. The idea of a spherical Earth appeared in ancient Greek philosophy with Pythagoras (6th century BC). However, most pre-Socratics (6th–5th century BC) retained the flat-Earth model. In the early 4th century BC, Plato wrote about a spherical Earth. By about 330 BC, his former student Aristotle had provided strong empirical evidence for a spherical Earth. Knowledge of the Earth's global shape gradually began to spread beyond the Hellenistic world. By the early period of the Christian Church, the spherical view was widely held, with some notable exceptions. It is a historical myth or modern misconception that medieval ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History Of Astronomy
Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, cosmological, calendrical, and astrological beliefs and practices of prehistory: vestiges of these are still found in astrology, a discipline long interwoven with public and governmental astronomy. It was not completely separated in Europe (see astrology and astronomy) during the Copernican Revolution starting in 1543. In some cultures, astronomical data was used for astrological prognostication. Early history Early cultures identified celestial objects with gods and spirits. They related these objects (and their movements) to phenomena such as rain, drought, seasons, and tides. It is generally believed that the first astronomers were priests, and that they understood celestial objects and events to be manifestations of the divine, hence early astronomy's connection to what is now called astrology. A 32,500-year-old carved ivory mammoth tusk could cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outer Space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is . The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Observations s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zhang Heng
Zhang Heng (; AD 78–139), formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, seismologist, hydraulic engineer, inventor, geographer, cartographer, ethnographer, artist, poet, philosopher, politician, and literary scholar. Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court. His uncompromising stance on historical and calendrical issues led to his becoming a controversial figure, preventing him from rising to the status of Grand Historian. His political rivalry with the palace eunuchs during the reign of Emperor Shun (r. 125–144) led to his decision to retire from the central court to serve as an administrator of Hejian Kingdom in present-day Hebei. Z ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luoxia Hong
Luoxia Hong (, c. 130-70 BCE) was a Chinese astronomer during the Western Han Dynasty. A folk astronomer from southwest China, Hong was one of over twenty astronomers who traveled to Chang'an (now Xi'an) to propose a new calendar system for Emperor Wu. It was not uncommon for emperors to introduce new calendars in order to place greater emphasis on heavenly bodies that were seen as particularly astrologically relevant to the particular ruler, but this reform was of such a scale that it was called the "Grand Inception" (太初) in contemporary documents. The calendar made by Hong and his associate Deng Ping was accepted over that of other contestants, including several imperial astronomers. It included 12 months of 29 or 30 days, with an additional month in seven out of 19 years. It also included precise calculations for the movement of the sun, moon, planets, and the time of eclipses, which Hong was able to predict using an equatorial armillary sphere which he significantly impro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Universe
In cosmology, a static universe (also referred to as stationary, infinite, static infinite or static eternal) is a cosmological model in which the universe is both spatially and temporally infinite, and space is neither expanding nor contracting. Such a universe does not have so-called spatial curvature; that is to say that it is 'flat' or Euclidean. A static infinite universe was first proposed by English astronomer Thomas Digges (1546–1595). In contrast to this model, Albert Einstein proposed a temporally infinite but spatially finite model as his preferred cosmology during 1917, in his paper ''Cosmological Considerations in the General Theory of Relativity''. After the discovery of the redshift-distance relationship (deduced by the inverse correlation of galactic brightness to redshift) by American astronomers Vesto Slipher and Edwin Hubble, the astrophysicist Georges Lemaître interpreted the redshift as evidence of universal expansion and thus a Big Bang, whereas Swi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observable Universe
The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion. There may be 2 trillion galaxies in the observable universe, although that number was reduced in 2021 to only several hundred billion based on data from '' New Horizons''. Assuming the universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a spherical region centered on the observer and is unique for every unique observational position. The word ''observable'' in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celestial Sphere
In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or the observer. If centered on the observer, half of the sphere would resemble a hemispherical screen over the observing location. The celestial sphere is a conceptual tool used in spherical astronomy to specify the position of an object in the sky without consideration of its linear distance from the observer. The celestial equator divides the celestial sphere into northern and southern hemispheres. Introduction Because astronomical objects are at such remote distances, casual observation of the sky offers no information on their actual distances. All celestial objects seem equally far away, as if fixed onto the inside of a sphere with a large but unknown radius, which appears to rotate westward o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
March Equinox
The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox (spring equinox) in the Northern Hemisphere and as the autumnal equinox in the Southern Hemisphere. On the Gregorian calendar, the northward equinox can occur as early as 19 March or as late as 21 March at 0° longitude. For a common year the computed time slippage is about 5 hours 49 minutes ''later'' than the previous year, and for a leap year about 18 hours 11 minutes ''earlier'' than the previous year. Balancing the increases of the common years against the losses of the leap years keeps the calendar date of the March equinox from drifting more than one day from 20 March each year. The March equinox may be taken to mark the beginning of astronomical spring and the end of astronomical winter in the Northern Hemisphere but m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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