1.
Prague astronomical clock
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The Prague astronomical clock, or Prague orloj, is a medieval astronomical clock located in Prague, the capital of the Czech Republic. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world, the Orloj is mounted on the southern wall of Old Town Hall in the Old Town Square. According to local legend, the city will suffer if the clock is neglected and its operation is placed in jeopardy. According to the legend, the hope was represented by a boy born on New Years night. The first recorded mention of the clock was on 9 October 1410, later, presumably around 1490, the calendar dial was added and the clock facade was decorated with gothic sculptures. Formerly, it was believed that the Orloj was constructed in 1490 by clockmaster Jan Růže, in 1552 it was repaired by Jan Taborský, master clockmaker of Klokotská Hora, who also wrote a report of the clock where he mentioned Hanuš as the maker of this clock. This mistake, corrected by Zdeněk Horský, was due to an interpretation of records from the period. The mistaken assumption that Hanuš was the maker is probably connected with his reconstruction of the Old Town Hall in the years 1470–1473, the clock stopped working many times in the centuries after 1552, and was repaired many times. In 1629 or 1659 wooden statues were added, and figures of the Apostles were added after a repair in 1787–1791. During the next major repair in the years 1865–1866 the golden figure of a rooster was added. The hall and nearby buildings burned along with the sculptures on the clock. After significant effort, the machinery was repaired, the wooden Apostles restored by Vojtěch Sucharda, the Orloj was last renovated in autumn 2005, when the statues and the lower calendar ring were restored. The wooden statues were covered with a net to keep pigeons away, on 9 October 2010, the Orlojs 600th anniversary was celebrated with a light show on the face of the clock tower. Two projectors were used to project several animated videos on the clock, the videos showed it being built, torn down, rebuilt, and peeled away to show its internal mechanisms and the famous animated figures, as well as various events in the clocks history. The video interacted with the architecture, such as rain rolling off the arch. On its 605th anniversary,9 October 2015, the Orloj appeared on the Google home page as a Google Doodle, the astronomical dial is a form of mechanical astrolabe, a device used in medieval astronomy. Alternatively, one may consider the Orloj to be a primitive planetarium, the background represents the Earth and the local view of the sky. The blue circle directly in the centre represents the Earth, the red and black areas indicate portions of the sky below the horizon
2.
Old Town Square
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Old Town Square is a historic square in the Old Town quarter of Prague, the capital of the Czech Republic. It is located between Wenceslas Square and the Charles Bridge, Prague Orloj is a medieval astronomical clock located on the Old Town Hall. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world, the Baroque St. Nicholas Church is another church located in the square, while the tower of the Old Town Hall offers a panoramic view of Old Town. An art museum of the Czech National Gallery is located in Kinský Palace, the squares center is home to a statue of religious reformer Jan Hus, who for his beliefs was burned at the stake in Constance, this led to the Hussite Wars. The statue known as the Jan Hus Memorial was erected on July 6,1915 to mark the 500th anniversary of his death. In front of the Old Town Hall is also a memorial to martyrs beheaded on that spot during the Old Town Square execution by Habsburgs, twenty-seven crosses mark the pavement in their honour. The crosses were installed during the repairs of Old Town Hall after the WW2, on November 3,1918, a Marian Column that had been erected in the square shortly after the Thirty Years War was demolished in celebration of independence from the Habsburg empire. At Christmas and Easter, markets are held on the square, a tall decorated tree and a musical stage are set up. The Christmas Markets on the Old Town Square are the largest Christmas markets in the Czech Republic and are visited by hundreds of thousands of visitors from the Czech Republic, the markets are mostly visited by Germans, Russians, Italians and British. In 2016, CNN rates Prague’s Christmas Markets among the world’s best, Old Town Square execution Old Town Square Live WebCam
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Prague
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Prague is the capital and largest city of the Czech Republic. It is the 14th largest city in the European Union and it is also the historical capital of Bohemia. Situated in the north-west of the country on the Vltava river, the city has a temperate climate, with warm summers and chilly winters. Prague has been a political, cultural, and economic centre of central Europe with waxing and waning fortunes during its history and it was an important city to the Habsburg Monarchy and its Austro-Hungarian Empire. Prague is home to a number of cultural attractions, many of which survived the violence. Main attractions include the Prague Castle, the Charles Bridge, Old Town Square with the Prague astronomical clock, since 1992, the extensive historic centre of Prague has been included in the UNESCO list of World Heritage Sites. The city has more than ten major museums, along with theatres, galleries, cinemas. An extensive modern public transportation system connects the city, also, it is home to a wide range of public and private schools, including Charles University in Prague, the oldest university in Central Europe. Prague is classified as an Alpha- global city according to GaWC studies, Prague ranked sixth in the Tripadvisor world list of best destinations in 2016. Its rich history makes it a popular tourist destination, and the city more than 6.4 million international visitors annually. Prague is the fifth most visited European city after London, Paris, Istanbul, the region was settled as early as the Paleolithic age. In the last century BC, the Celts were slowly driven away by Germanic tribes, around the area where present-day Prague stands, the 2nd century map of Ptolemaios mentioned a Germanic city called Casurgis. In the following century, the Czech tribes built several fortified settlements in the area, most notably in Levý Hradec, Butovice and in the Šárka valley. The construction of what came to be known as the Prague Castle began near the end of the 9th century, the first masonry under Prague Castle dates from the year 885 at the latest. The other prominent Prague fort, the Přemyslid fort Vyšehrad, was founded in the 10th century, Prague Castle is dominated by the cathedral, which was founded in 1344, but completed in the 20th century. The legendary origins of Prague attribute its foundation to the 8th century Czech duchess and prophetess Libuše and her husband, Přemysl, legend says that Libuše came out on a rocky cliff high above the Vltava and prophesied, I see a great city whose glory will touch the stars. She ordered a castle and a town called Praha to be built on the site, a 17th century Jewish chronicler David Solomon Ganz, citing Cyriacus Spangenberg, claimed that the city was founded as Boihaem in c.1306 BC by an ancient king, Boyya. The region became the seat of the dukes, and later kings of Bohemia, under Roman Emperor Otto II the area became a bishopric in 973
4.
Clock
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A clock is an instrument to measure, keep, and indicate time. The word clock is derived from the Celtic words clagan and clocca meaning bell, a silent instrument missing such a striking mechanism has traditionally been known as a timepiece. In general usage today a clock refers to any device for measuring and displaying the time, Watches and other timepieces that can be carried on ones person are often distinguished from clocks. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units, the day, the lunar month. Devices operating on several physical processes have been used over the millennia, a sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, an example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments, spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished, the next development in accuracy occurred after 1656 with the invention of the pendulum clock. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation, the electric clock was patented in 1840. The development of electronics in the 20th century led to clocks with no clockwork parts at all, the timekeeping element in every modern clock is a harmonic oscillator, a physical object that vibrates or oscillates at a particular frequency. This object can be a pendulum, a fork, a quartz crystal. Analog clocks usually indicate time using angles, Digital clocks display a numeric representation of time. Two numeric display formats are used on digital clocks, 24-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays, for convenience, distance, telephony or blindness, auditory clocks present the time as sounds. There are also clocks for the blind that have displays that can be read by using the sense of touch, some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. The evolution of the technology of clocks continues today, the study of timekeeping is known as horology. The apparent position of the Sun in the sky moves over the course of a day, shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a flat surface, sundials can be horizontal, vertical, or in other orientations
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Mechanism (engineering)
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A mechanism is a device designed to transform input forces and movement into a desired set of output forces and the movement. In this context, his use of machine is generally interpreted to mean mechanism, the combination of force and movement defines power, and a mechanism is designed to manage power in order to achieve a desired set of forces and movement. A mechanism is usually a piece of a process or mechanical system. Sometimes an entire machine may be referred to as a mechanism, examples are the steering mechanism in a car, or the winding mechanism of a wristwatch. From the time of Archimedes through the Renaissance, mechanisms were considered to be constructed from simple machines, such as the lever, pulley, screw, wheel and axle, wedge and inclined plane. It was Reuleaux who focussed on bodies, called links, in order to use geometry to study the movement of a mechanism, its links are modeled as rigid bodies. This means distances between points in a link are assumed to be unchanged as the moves, that is the link does not flex. Thus, the movement between points in two connected links is considered to result from the kinematic pair that joins them. A mechanism is modeled as an assembly of rigid links and kinematic pairs, Reuleaux called the ideal connections between links kinematic pairs. He distinguished between higher pairs which were said to have contact between the two links and lower pairs that have area contact between the links. J. Phillips shows that there are ways to construct pairs that do not fit this simple. Lower pair, A lower pair is a joint that has surface contact between the pair of elements. This imposes five constraints on the movement of the links. This imposes five constraints on the movement of the links. A cylindrical joint requires that a line in the body remain co-linear with a line in the fixed body. It is a combination of a joint and a sliding joint. This joint has two degrees of freedom, a spherical joint, or ball joint, requires that a point in the moving body maintain contact with a point in the fixed body. This joint has three degrees of freedom, a planar joint requires that a plane in the moving body maintain contact with a plane in fixed body
6.
Dial (measurement)
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There are many instruments used in scientific and industrial applications that use dials with pointers as indicators of a specific physical property. Typical examples include pressure and vacuum gauges, fluid-level gauges, voltmeters and ammeters, thermometers and hygrometers, speedometers and tachometers, traditionally these have been mechanical devices, but with the advent of electronic displays, analog dials are often simulated from digital measurements. Styles of dials, Circular, Fixed pointer with moving scale, examples of dial usage, Pressure and vacuum gauges, Level gauges, Volt and current meters, Thermometers and thermostats, Speedometers and tachometers. Mirror dials are designed to reduce or eliminate the effect of parallax and they usually consist of a small mirrored strip running parallel to the graduations of the scale under the pointer. When the observer moves his position so that the pointer obscures the pointers reflection in the mirror, an accurate reading may be taken
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Astronomy
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Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros
8.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
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Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
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Zodiac
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The zodiac is an area of the sky centered upon the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, in western astrology and astronomy, the zodiac is divided into twelve signs, each sign occupying 30° of celestial longitude. Because the signs are regular, they do not correspond exactly to the boundaries of the twelve constellations after which they are named, the English word zodiac derives from zōdiacus, the Latinized form of the Ancient Greek zōidiakòs kýklos, meaning circle of little animals. Zōidion is the diminutive of zōion, the name reflects the prominence of animals among the twelve signs. The construction of the zodiac is described in Ptolemys vast 2nd century AD work, the term zodiac may also refer to the region of the celestial sphere encompassing the paths of the planets corresponding to the band of about eight arc degrees above and below the ecliptic. The zodiac of a planet is the band that contains the path of that particular body, e. g. the zodiac of the Moon is the band of five degrees above. By extension, the zodiac of the comets may refer to the band encompassing most short-period comets, the division of the ecliptic into the zodiacal signs originates in Babylonian astronomy during the first half of the 1st millennium BC. The zodiac draws on stars in earlier Babylonian star catalogues, such as the MUL. APIN catalogue, around the end of the 5th century BC, Babylonian astronomers divided the ecliptic into twelve equal signs, by analogy to twelve schematic months of thirty days each. Each sign contained thirty degrees of longitude, thus creating the first known celestial coordinate system. Because the division was made into equal arcs, 30° each, in Babylonian astronomical diaries, a planet position was generally given with respect to a zodiacal sign alone, less often in specific degrees within a sign. When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, in astronomical ephemerides, the positions of significant astronomical phenomena were computed in sexagesimal fractions of a degree. For daily ephemerides, the positions of a planet were not as important as the astrologically significant dates when the planet crossed from one zodiacal sign to the next. The Babylonian star catalogs entered Greek astronomy in the 4th century BC, Babylonia or Chaldea in the Hellenistic world came to be so identified with astrology that Chaldean wisdom became among Greeks and Romans the synonym of divination through the planets and stars. Hellenistic astrology derived in part from Babylonian and Egyptian astrology, horoscopic astrology first appeared in Ptolemaic Egypt. The Dendera zodiac, a dating to ca.50 BC, is the first known depiction of the classical zodiac of twelve signs. The earliest extant Greek text using the Babylonian division of the zodiac into 12 signs of 30 equal degrees each is the Anaphoricus of Hypsicles of Alexandria. Particularly important in the development of Western horoscopic astrology was the astrologer and astronomer Ptolemy, whose work Tetrabiblos laid the basis of the Western astrological tradition. Under the Greeks, and Ptolemy in particular, the planets, Houses, Ptolemy lived in the 2nd century AD, three centuries after the discovery of the precession of the equinoxes by Hipparchus around 130 BC
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Constellation
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A constellation is formally defined as a region of the celestial sphere, with boundaries laid down by the International Astronomical Union. The constellation areas mostly had their origins in Western-traditional patterns of stars from which the constellations take their names, in 1922, the International Astronomical Union officially recognized the 88 modern constellations, which cover the entire sky. They began as the 48 classical Greek constellations laid down by Ptolemy in the Almagest, Constellations in the far southern sky are late 16th- and mid 18th-century constructions. 12 of the 88 constellations compose the zodiac signs, though the positions of the constellations only loosely match the dates assigned to them in astrology. The term constellation can refer to the stars within the boundaries of that constellation. Notable groupings of stars that do not form a constellation are called asterisms, when astronomers say something is “in” a given constellation they mean it is within those official boundaries. Any given point in a coordinate system can unambiguously be assigned to a single constellation. Many astronomical naming systems give the constellation in which an object is found along with a designation in order to convey a rough idea in which part of the sky it is located. For example, the Flamsteed designation for bright stars consists of a number, the word constellation seems to come from the Late Latin term cōnstellātiō, which can be translated as set of stars, and came into use in English during the 14th century. It also denotes 88 named groups of stars in the shape of stellar-patterns, the Ancient Greek word for constellation was ἄστρον. Colloquial usage does not draw a distinction between constellation in the sense of an asterism and constellation in the sense of an area surrounding an asterism. The modern system of constellations used in astronomy employs the latter concept, the term circumpolar constellation is used for any constellation that, from a particular latitude on Earth, never sets below the horizon. From the North Pole or South Pole, all constellations south or north of the equator are circumpolar constellations. In the equatorial or temperate latitudes, the term equatorial constellation has sometimes been used for constellations that lie to the opposite the circumpolar constellations. They generally include all constellations that intersect the celestial equator or part of the zodiac, usually the only thing the stars in a constellation have in common is that they appear near each other in the sky when viewed from the Earth. In galactic space, the stars of a constellation usually lie at a variety of distances, since stars also travel on their own orbits through the Milky Way, the star patterns of the constellations change slowly over time. After tens to hundreds of thousands of years, their familiar outlines will become unrecognisable, the terms chosen for the constellation themselves, together with the appearance of a constellation, may reveal where and when its constellation makers lived. The earliest direct evidence for the constellations comes from inscribed stones and it seems that the bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC
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Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
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Astrarium
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An astrarium, also called a planetarium, is the mechanical representation of the cyclic nature of astronomical objects in one timepiece. The first astraria were mechanical devices, archimedes is said to have used a primitive version that could predict the positions of the sun, the moon, and the planets. This mechanism, known as the Antikythera mechanism, was recently re-dated to between, extensive study of the fragments, using X-rays, has revealed enough details to enable researchers to build partial replicas of the original device. Engraved on the gears are the names of the planets. However, by the end of the Roman Empire, the know-how, the first modern documented astrarium clock was completed in 1364 by Giovanni de Dondi, a scholar and physician of the Middle Ages interested in astronomy and horology. It displays the time, sidereal, time and the motions of the sun, moon and the five then-known planets Venus, Mars, Saturn, Mercury. It was conceived according to a Ptolemaic conception of the solar system, de Dondi was inspired by his father Jacopo who designed the astronomical clock in the Piazzi dei Signori, Padua, in 1344 - one of the first of its type. In later ages more astraria were built, a famous example is the one built in 1774 by Eise Eisinga from Dronrijp, Friesland, the Netherlands. It displayed all the planets and was fixed to the ceiling in a house in Franeker where it can still be visited, in modern times, the astrarium has grown into a tourist attraction as a commercially exploited planetarium-showing in IMAX theaters. With such presentations as The history of the Universe, as well as astronomical phenomena. Astronomical clock Planetarium Orrery Annosphere An electro-mechanical model of the earth/sun relationship, Giovanni Dondi dellOrologio - Tractatus astarii
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Giovanni Dondi dell'Orologio
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Giovanni Dondi dellOrologio, also known as Giovanni de Dondi, was a doctor and clock-maker in Padua, now in Italy. He is remembered today as a pioneer in the art of clock design, Giovanni was the second son of Jacopo Dondi dellOrologio and Zaccarota Centrago or Centraco of Chioggia. His father was a doctor and astronomer, and builder of an astronomical clock in the tower of the Palazzo Capitaniato of Padua in 1344. Giovanni lived with his father from 1348 to 1359, and shared his fathers interest in astronomy, in 1348 he began working on what he called his astrarium or planetarium. He described in detail the design and construction of this project and his manuscripts provided enough material for modern clockmakers to build reconstructions. He is buried at SantEustorgio in Milan, Dondi wrote on a wide range of subjects. His most celebrated work is the Tractatus astrarii or Planetarium, which describes the Astrarium and it is one of the earliest surviving descriptions of its kind, predated by only a few years by the Albion and Horologium of Richard of Wallingford. The Tractatus survives in manuscript sources. The autograph in the Biblioteca Capitolare of Padua and a copy of it, the other sources are rewritten versions of the autograph, to which Dondis contribution is as yet unclear. The autograph manuscript was published in 1987 in an edition with colour facsimile and French translation by Poulle as the first volume of the Opera omnia of Jacopo. The Quaestiones are to date unpublished, as are Dondis Experimenta or medical prescriptions, conserved in a manuscript of Iohannes de Livonia dated 1453 and now in the Biblioteca Civica of Padua. A manuscript in the Biblioteca Nazionale Marciana, though not in Dondis hand, Dondis quaedani apostillae or notes on a letter of Seneca, mentioned in a manuscript of Gasparino Barzizza from 1411, have not been traced. The astrarium was considered to be a marvel of its day, Giovanni Manzini of Pavia writes that it is a work full of artifice, worked on and perfected by your hands and carved with a skill never attained by the expert hand of any craftsman. I conclude that there was never invented an artifice so excellent and marvelous, Dondi writes that he obtained the idea of an astrarium from the Theorica planetarum of Giovanni Campano da Novara, who describes the construction of the equatorium. The astrarium was primarily a clockwork equatorium with astrolabe and calendar dials, and indicators for the sun, moon and it provided a continuous display of the major elements of the solar system and of the legal, religious, and civil calendars of the day. Dondis intention was that it would help understanding of astronomical and astrological concepts. Astrology was then considered a subject worthy of study by the elite and was taken reasonably seriously. In 1381 Dondi presented his clock to the Duke Gian Galeazzo Visconti and it remained there until at least 1485
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Lunar phase
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The lunar phase or phase of the moon is the shape of the illuminated portion of the Moon as seen by an observer on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the positions of the Moon. The Moons rotation is locked by the Earths gravity, therefore the same lunar surface always faces Earth. This face is variously sunlit depending on the position of the Moon in its orbit, therefore, the portion of this hemisphere that is visible to an observer on Earth can vary from about 100% to 0%. The lunar terminator is the boundary between the illuminated and darkened hemispheres, each of the four intermediate lunar phases is roughly seven days but this varies slightly due to the elliptical shape of the Moons orbit. Aside from some craters near the lunar poles such as Shoemaker, all parts of the Moon see around 14.77 days of sunlight, in Western culture, the four principal lunar phases are new moon, first quarter, full moon, and third quarter. These are the instants when the Moons apparent geocentric celestial longitude minus the Suns apparent geocentric longitude is 0°, 90°, 180° and 270°. Each of these phases is instantaneous, lasting theoretically zero time, during the intervals between principal phases, the Moon appears either crescent-shaped or gibbous. These shapes, and the periods of time when the Moon shows them, are called the intermediate phases. They last, on average, one-quarter of a month, roughly 7.38 days, but their durations vary slightly because the Moons orbit is slightly elliptical. The descriptor waxing is used for a phase when the Moons apparent size is increasing, from new moon toward full moon. As the moon waxes, the lunar phases progress through new moon, crescent moon, first-quarter moon, gibbous moon, the moon is then said to wane as it passes through the gibbous moon, third-quarter moon, crescent moon and back to new moon. The terms old moon and new moon are not interchangeable, the old moon is a waning sliver until the moment it aligns with the sun and begins to wax, at which point it becomes new again. Half moon is used to mean the first- and third-quarter moons, while the term quarter refers to the extent of the moons cycle around the Earth. When a crescent Moon occurs, the phenomenon of earthshine may be apparent, in the Northern Hemisphere, if the left side of the Moon is dark then the light part is growing, and the Moon is referred to as waxing. If the right side of the Moon is dark then the part is shrinking. Assuming that the viewer is in the hemisphere, the right portion of the Moon is the part that is always growing. Nearer the Equator the Moon with its terminator will appear apparently horizontal during the morning and evening, the crescent Moon can open upward or downward, with the horns of the crescent pointing up or down, respectively
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Sidereal time
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Sidereal time /saɪˈdɪəriəl/ is a time-keeping system that astronomers use to locate celestial objects. Using sidereal time it is possible to point a telescope to the proper coordinates in the night sky. Briefly, sidereal time is a scale that is based on Earths rate of rotation measured relative to the fixed stars rather than the Sun. From a given point, a star found at one location in the sky will be found at the same location on another night at the same sidereal time. This is similar to how the time kept by a sundial can be used to find the location of the Sun, just as the Sun and Moon appear to rise in the east and set in the west due to the rotation of Earth, so do the stars. Both solar time and sidereal time make use of the regularity of Earths rotation about its polar axis, a mean sidereal day is 23 hours,56 minutes,4.0916 seconds, the time it takes Earth to make one rotation relative to the vernal equinox. The longer true sidereal period is called a day by the International Earth Rotation. It is also referred to as the period of rotation. Maps of the stars in the night sky use declination and right ascension as coordinates and these correspond to latitude and longitude respectively. In the sky, the meridian is the north to south line that goes through the point directly overhead. Solar time is measured by the apparent diurnal motion of the Sun, a mean solar day is the average time between local solar noons. Earth makes one rotation around its axis in a sidereal day, so after a sidereal day has passed, Earth still needs to rotate slightly more before the Sun reaches local noon according to solar time. A mean solar day is, therefore, nearly 4 minutes longer than a sidereal day, the stars are so far away that Earths movement along its orbit makes nearly no difference to their apparent direction, and so they return to their highest point in a sidereal day. Another way to see this difference is to notice that, relative to the stars, therefore, there is one fewer solar day per year than there are sidereal days. This makes a sidereal day approximately 365. 24/366.24 times the length of the 24-hour solar day, Earths rotation is not a simple rotation around an axis that would always remain parallel to itself. Earths rotational axis itself rotates about an axis, orthogonal to Earths orbit. This phenomenon is called the precession of the equinoxes, because of this precession, the stars appear to move around Earth in a manner more complicated than a simple constant rotation. In this reference frame, Earths rotation is close to constant and it is also in this reference frame that the tropical year, the year related to Earths seasons, represents one orbit of Earth around the Sun
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Eclipse
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An eclipse occurs during a syzygy. The term eclipse is most often used to either a solar eclipse, when the Moons shadow crosses the Earths surface, or a lunar eclipse. A binary star system can also produce eclipses if the plane of the orbit of its constituent stars intersects the observers position, for any two objects in space, a line can be extended from the first through the second. The latter object will block some amount of light being emitted by the former, as viewed from such a location, this shadowing event is known as an eclipse. Typically the cross-section of the involved in an astronomical eclipse are roughly disk shaped. The region of an objects shadow during an eclipse is divided into three parts, The umbra, within which the object completely covers the light source, for the Sun, this light source is the photosphere. The antumbra, extending beyond the tip of the umbra, within which the object is completely in front of the light source, the penumbra, within which the object is only partially in front of the light source. A total eclipse occurs when the observer is within the umbra, an annular eclipse when the observer is within the antumbra, during a lunar eclipse only the umbra and penumbra are applicable. This is because Earths apparent diameter from the viewpoint of the Moon is nearly four times that of the Sun, the same terms may be used analogously in describing other eclipses, e. g. the antumbra of Deimos crossing Mars, or Phobos entering Marss penumbra. For Earth, on average L is equal to 1. 384×106 km, hence the umbral cone of the Earth can completely envelop the Moon during a lunar eclipse. If the occulting object has an atmosphere, however, some of the luminosity of the star can be refracted into the volume of the umbra. This occurs, for example, during an eclipse of the Moon by the Earth—producing a faint, on Earth, the shadow cast during an eclipse moves very approximately at 1 km per sec. This depends on the location of the shadow on the Earth, http, //www. sciforums. com/threads/speed-of-eclipse-shadow. 53722/ An eclipse cycle takes place when a series of eclipses are separated by a certain interval of time. This happens when the orbital motions of the bodies form repeating harmonic patterns, a particular instance is the saros, which results in a repetition of a solar or lunar eclipse every 6,585.3 days, or a little over 18 years. Because this is not a number of days, successive eclipses will be visible from different parts of the world. An eclipse involving the Sun, Earth, and Moon can occur only when they are nearly in a line, allowing one to be hidden behind another. Because the orbital plane of the Moon is tilted with respect to the plane of the Earth. The Sun, Earth and nodes are aligned twice a year, there can be from four to seven eclipses in a calendar year, which repeat according to various eclipse cycles, such as a saros
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Pendulum clock
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A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is an oscillator, it swings back and forth in a precise time interval dependent on its length. From its invention in 1656 by Christiaan Huygens until the 1930s, Pendulum clocks must be stationary to operate, any motion or accelerations will affect the motion of the pendulum, causing inaccuracies, so other mechanisms must be used in portable timepieces. They are now mostly for their decorative and antique value. The pendulum clock was invented in 1656 by Dutch scientist and inventor Christiaan Huygens, Huygens contracted the construction of his clock designs to clockmaker Salomon Coster, who actually built the clock. Huygens was inspired by investigations of pendulums by Galileo Galilei beginning around 1602, Galileo discovered the key property that makes pendulums useful timekeepers, isochronism, which means that the period of swing of a pendulum is approximately the same for different sized swings. Galileo had the idea for a clock in 1637, which was partly constructed by his son in 1649. These early clocks, due to their verge escapements, had wide pendulum swings of up to 100°, clockmakers realization that only pendulums with small swings of a few degrees are isochronous motivated the invention of the anchor escapement around 1670, which reduced the pendulums swing to 4–6°. The anchor became the standard escapement used in pendulum clocks, in addition to increased accuracy, the anchors narrow pendulum swing allowed the clocks case to accommodate longer, slower pendulums, which needed less power and caused less wear on the movement. The seconds pendulum,0.994 m long, in which each swing takes one second, the long narrow clocks built around these pendulums, first made by William Clement around 1680, became known as grandfather clocks. The increased accuracy resulting from these developments caused the hand, previously rare. The 18th and 19th century wave of innovation that followed the invention of the pendulum brought many improvements to pendulum clocks. Observation that pendulum clocks slowed down in summer brought the realization that thermal expansion and contraction of the rod with changes in temperature was a source of error. This was solved by the invention of temperature-compensated pendulums, the pendulum by George Graham in 1721. With these improvements, by the mid-18th century precision pendulum clocks achieved accuracies of a few seconds per week, until the 19th century, clocks were handmade by individual craftsmen and were very expensive. The rich ornamentation of pendulum clocks of this period indicates their value as symbols of the wealthy. The clockmakers of each country and region in Europe developed their own distinctive styles, by the 19th century, factory production of clock parts gradually made pendulum clocks affordable by middle-class families. During the Industrial Revolution, daily life was organized around the pendulum clock
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Geocentric model
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In astronomy, the geocentric model is a superseded description of the universe with the Earth at the center. Under the geocentric model, the Sun, Moon, stars, the geocentric model served as the predominant description of the cosmos in many ancient civilizations, such as those of Aristotle and Ptolemy. Two observations supported the idea that the Earth was the center of the Universe, first, the Sun appears to revolve around the Earth once per day. While the Moon and the planets have their own motions, they appear to revolve around the Earth about once per day. The stars appeared to be on a sphere, rotating once each day along an axis through the north and south geographic poles of the Earth. Second, the Earth does not seem to move from the perspective of an Earth-bound observer, it appears to be solid, stable, Ancient Greek, ancient Roman and medieval philosophers usually combined the geocentric model with a spherical Earth. It is not the same as the older flat Earth model implied in some mythology, the ancient Jewish Babylonian uranography pictured a flat Earth with a dome-shaped rigid canopy named firmament placed over it. The astronomical predictions of Ptolemys geocentric model were used to prepare astrological and astronomical charts for over 1500 years. The geocentric model held sway into the modern age, but from the late 16th century onward, it was gradually superseded by the Heliocentric model of Copernicus, Galileo. There was much resistance to the transition between these two theories, christian theologians were reluctant to reject a theory that agreed with Bible passages. Others felt a new, unknown theory could not subvert an accepted consensus for geocentrism, the geocentric model entered Greek astronomy and philosophy at an early point, it can be found in Pre-Socratic philosophy. In the 6th century BC, Anaximander proposed a cosmology with the Earth shaped like a section of a pillar, the Sun, Moon, and planets were holes in invisible wheels surrounding the Earth, through the holes, humans could see concealed fire. About the same time, the Pythagoreans thought that the Earth was a sphere, later these views were combined, so most educated Greeks from the 4th century BC on thought that the Earth was a sphere at the center of the universe. In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle, wrote works based on the geocentric model, according to Plato, the Earth was a sphere, stationary at the center of the universe. In his Myth of Er, a section of the Republic, Plato describes the cosmos as the Spindle of Necessity, attended by the Sirens and these spheres, known as crystalline spheres, all moved at different uniform speeds to create the revolution of bodies around the Earth. They were composed of a substance called aether. Aristotle believed that the moon was in the innermost sphere and therefore touches the realm of Earth, causing the dark spots and he further described his system by explaining the natural tendencies of the terrestrial elements, Earth, water, fire, air, as well as celestial aether. His system held that Earth was the heaviest element, with the strongest movement towards the center, the tendency of air and fire, on the other hand, was to move upwards, away from the center, with fire being lighter than air
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Antikythera mechanism
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Found housed in a 340 millimetres ×180 millimetres ×90 millimetres wooden box, the device is a complex clockwork mechanism composed of at least 30 meshing bronze gears. Its remains were found as one lump, later separated in three fragments, which are now divided into 82 separate fragments after conservation works. Four of these fragments contain gears, while inscriptions are found on many others, the largest gear is approximately 140 millimetres in diameter and originally had 223 teeth. The artefact was recovered probably in July 1901 from the Antikythera shipwreck off the Greek island of Antikythera. Believed to have designed and constructed by Greek scientists, the instrument has been dated either between 150 and 100 BC, or, according to a more recent view, in 205 BC. All known fragments of the Antikythera mechanism are kept at the National Archaeological Museum, in Athens, the Antikythera mechanism was discovered in 45 metres of water in the Antikythera shipwreck off Point Glyphadia on the Greek island of Antikythera. All were transferred to the National Museum of Archaeology in Athens for storage, merely a lump of corroded bronze and wood at the time, the mechanism went unnoticed for two years while museum staff worked on piecing together more obvious statues. On 17 May 1902, archaeologist Valerios Stais was examining the finds, investigations into the object were soon dropped until British science historian and Yale University professor, Derek J. de Solla Price became interested in it in 1951. In 1971, both Price and Greek nuclear physicist Charalampos Karakalos made X-ray and gamma-ray images of the 82 fragments, Price published an extensive 70-page paper on their findings in 1974. Generally referred to as the first known computer, the quality and complexity of the mechanisms manufacture suggests it has undiscovered predecessors made during the Hellenistic period. Its construction relied upon theories of astronomy and mathematics developed by Greek astronomers, in 1974, Derek de Solla Price concluded from gear settings and inscriptions on the mechanisms faces that it was made about 87 BC and lost only a few years later. Jacques Cousteau and associates visited the wreck in 1976 and recovered coins dated to between 76 and 67 BC, though its advanced state of corrosion has made it impossible to perform an accurate compositional analysis, it is believed the device was made of a low-tin bronze alloy. All its instructions are written in Koine Greek, and the consensus among scholars is that the mechanism was made in the Greek-speaking world, syracuse was a colony of Corinth and the home of Archimedes, which might imply a connection with the school of Archimedes. With its many scrolls of art and science, it was second in only to the Library of Alexandria during the Hellenistic period. A busy trading port in antiquity, Rhodes was also a centre of astronomy and mechanical engineering, home to the astronomer Hipparchus and that the mechanism uses Hipparchuss theory for the motion of the moon suggests the possibility he may have designed, or at least worked on it. He regarded the Antikythera mechanism as more valuable than the Mona Lisa, in 2014, a study by Carman and Evans argued for a new dating of approximately 200 BC. Moreover, according to Carman and Evans, the Babylonian arithmetic style of prediction fits much better with the devices predictive models than the traditional Greek trigonometric style, further dives are being undertaken in the hope of discovering more of the mechanism. The original mechanism apparently came out of the Mediterranean as a single encrusted piece, soon afterward it fractured into three major pieces
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24-hour analog dial
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Clocks and watches with a 24-hour analog dial have an hour hand that makes one complete revolution, 360°, in a day. The more familiar 12-hour analog dial has a hand that makes two complete revolutions in a day. Twenty-four-hour analog clocks and watches are used today by pilots, scientists, and the military, note that this definition refers to the use of a complete circular dial to represent a 24-hour day. Using the numbers from 0 to 23 to mark the day is the 24-hour clock system, sundials use 24-hour analog dials—the shadow traces a path that repeats approximately once per day. Many sundials are marked with the double-XII or double-12 system, in which the numbers I to XII are used twice, once for the morning hours, so VI appears twice on many dials, once near sunrise and once near sunset. Modern 24-hour analog dials—other than sundials—are almost always marked with 24 numbers or hour marks around the edge and these dials do not need to indicate AM or PM. The ancient Egyptians divided the day into 24 hours, there are diagrams of circles divided into 24 sections in the astronomical ceiling in the tomb of Senemut. Sundials use some or all of the 24-hour dial, because they show the position of the sun in the sky, sometimes, for aesthetic rather than practical reasons, all the 24 hour marks are shown. Medieval clocks often used the 24-hour analog dial, influenced by the example of the astrolabe. In Italy, the numbers from 1 to 24 were used, on Italian clocks, though, the I was often shown at the right side of the dial, rather than the top. This probably reflects the influence of the Italian timekeeping system, which started counting the hours of the day at sunset or twilight. In northern Europe, the double XII system was superseded during the 14th and 15th centuries by the single XII. The 24-hour analog dial continued to be used, but primarily by technicians, astronomers, scientists, john Harrison, Thomas Tompion, and Mudge built a number of clocks with 24-hour analog dials, particularly when building astronomical and nautical instruments. In the 20th century, the 24-hour analog dial was adopted by radio amateurs, pilots, submariners, 24-hour analog watches and clocks are still being manufactured today, and are sought after by collectors and enthusiasts. A famous brand is the Glycine Airman watch, other manufacturers who make 24-hour analog watches include Breitling, Raketa, Vostok, Fortis, Poljot, Swatch, and many others. The major variation in the design of 24-hour analog dials is the location of midnight, although always opposite each other, 180° apart, noon is sometimes at the top, sometimes at the bottom. A few rare variants place noon and midnight at the right, there is no ambiguity if the 24-hour numbering is used. In the United States, the government and military commonly use 24-hour clocks having noon at the bottom, the Chinese traditional shi-ke system may be an optimum design of 24-hour clock
22.
Copernican Revolution
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The Copernican Revolution is named for Nicolaus Copernicus, whose Commentariolus, written before 1514, was the first explicit presentation of the heliocentric model in Renaissance scholarship. Ancient heliocentrism was, however, eclipsed by the model presented by Ptolemy. European scholars were aware of the problems with Ptolemaic astronomy since the 13th century. The debate was precipitated by the the reception by Averroes criticism of Ptolemy, otto E. Peuerbach attempts to give a new, mathematically more elegant presentation of Ptolemys system, but he does not arrive at heliocentrism. Regiomontanus himself was the teacher of Domenico Maria Novara da Ferrara, Copernicus studied at Bologna University during 1496–1501, where he became the assistant of Domenico Maria Novara da Ferrara. He is known to have studied the Epitome in Almagestum Ptolemei by Peuerbach and Regiomontanus and he continued to refine his system until publishing his larger work, De revolutionibus orbium coelestium, which contained detailed diagrams and tables. The Copernican model makes the claim of describing the reality of the cosmos. Copernicus removed Earth from the center of the universe, set the bodies in rotation around the Sun. While Copernicus’s work sparked the Copernican Revolution, it did not mark its end, in fact, Copernicus’s own system had multiple shortcomings that would have to be amended by later astronomers. Tycho Brahe was a Danish nobleman who was known as an astronomer in his time. Further advancement in the understanding of the cosmos would require new, more accurate observations than those that Nicolaus Copernicus relied on, Tycho Brahe accepted Copernicuss model but reasserted geocentricity. However, Tycho challenged the Aristotelian model when he observed a comet that went through the region of the planets and this region was said to only have uniform circular motion on solid spheres, which meant that it would be impossible for a comet to enter into the area. In 1572, Tycho Brahe observed a new star in the constellation Cassiopeia, for eighteen months, it shone brightly in the sky with no visible parallax, indicating it was part of the heavenly region of stars according to Aristotles model. However, according to model, no change could take place in the heavens so Tycho’s observation was a major discredit to Aristotle’s theories. In 1577, Tycho observed a comet in the sky. Based on his observations, the comet passed through the region of the planets. According to Aristotelian theory, only uniform circular motion on solid spheres existed in this region, Tycho concluded there were no such spheres, raising the question of what kept a planet in orbit. With the patronage of the King of Denmark, Tycho Brahe established Uraniborg, for 20 years, Tycho and his team of astronomers compiled astronomical observations that were vastly more accurate than those made before
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History of timekeeping devices
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For thousands of years, devices have been used to measure and keep track of time. The current sexagesimal system of time measurement dates to approximately 2000 BC from the Sumerians, the Ancient Egyptians divided the day into two 12-hour periods, and used large obelisks to track the movement of the sun. The Zhou dynasty is believed to have used the water clock around the same time. The sundial, another clock, relies on shadows to provide a good estimate of the hour on a sunny day. It is not so useful in weather or at night. The pendulum clock remained the most accurate timekeeper until the 1930s, many ancient civilizations observed astronomical bodies, often the Sun and Moon, to determine times, dates, and seasons. The first calendars may have been created during the last glacial period, by hunter-gatherers who employed tools such as sticks, as those megalithic civilizations left no recorded history, little is known of their calendars or timekeeping methods. Methods of sexagesimal timekeeping, now common in both Western and Eastern societies, are first attested nearly 4,000 years ago in Mesopotamia, mesoamericans similarly modified their usual vigesimal counting system when dealing with calendars to produce a 360-day year. The oldest known sundial is from Egypt, it dates back to around 1500 BC, sundials have their origin in shadow clocks, which were the first devices used for measuring the parts of a day. Ancient Egyptian obelisks, constructed about 3500 BC, are also among the earliest shadow clocks, Egyptian shadow clocks divided daytime into 12 parts with each part further divided into more precise parts. One type of shadow clock consisted of a stem with five variable marks. It was positioned eastward in the morning, and was turned west at noon, obelisks functioned in much the same manner, the shadow cast on the markers around it allowed the Egyptians to calculate the time. The obelisk also indicated whether it was morning or afternoon, as well as the summer and winter solstices, a third shadow clock, developed c.1500 BC, was similar in shape to a bent T-square. It measured the passage of time by the shadow cast by its crossbar on a non-linear rule, the T was oriented eastward in the mornings, and turned around at noon, so that it could cast its shadow in the opposite direction. Although accurate, shadow clocks relied on the sun, and so were useless at night, the Egyptians therefore developed a number of alternative timekeeping instruments, including water clocks, and a system for tracking star movements. The oldest description of a clock is from the tomb inscription of the 16th-century BC Egyptian court official Amenemhet. There were several types of clocks, some more elaborate than others. The oldest-known waterclock was found in the tomb of pharaoh Amenhotep I, another Egyptian method of determining the time during the night was using plumb-lines called merkhets
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Richard of Wallingford
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For the Constable of Wallingford Castle, see Richard of Wallingford. Richard of Wallingford was a monk and English mathematician who made major contributions to astronomy. Richard was born, the son of a blacksmith, at Wallingford in Berkshire in England in 1292, when he was orphaned he was taken to William de Kirkeby the Prior of Holy Trinity Priory. Richard subsequently spent 6 years studying at Oxford University before becoming a monk at St Albans and he later studied for 9 more years at Oxford. In 1327 he became abbot of St Albans, Richard of Wallingford is best known for the astronomical clock he designed, while he was abbot, which is described in the Tractatus Horologii Astronomici. The clock was completed about 20 years after Richards death by William of Walsham but was destroyed during Henry VIIIs reformation. His clock almost certainly was the most complex clock mechanism in existence at the time in the British isles, the only other clocklike mechanism of comparable complexity that is documented in the 14th century is the astrarium by Giovanni de Dondi. It gave not just the hours and minutes of the day, based on the 14th-century literary evidence still surviving in the 20th century, several scholars of horological history have tried to build recreations of Richard of Wallingfords clock. Richard also designed and constructed calculation devices, a torquetum, the Rectangulus, and an equatorium and this could be used for astronomical calculations such as lunar, solar and planetary longitudes and could predict eclipses. This is described in the Tractatus Albionis and he published other works on trigonometry, celestial coordinates, astrology, and various religious works. Richard suffered from what was thought to be leprosy which he apparently contracted when he went to have his position as abbot of St Albans Abbey confirmed by the Pope at Avignon. He died at St Albans in 1336, Giovanni Dondi dellOrologio Yi Xing Su Song North, J. Gods Clockmaker, Richard of Wallingford and the Invention of Time. ISBN 1-85285-451-0 North, J. ISBN 0-19-858139-4 Watson, E The St Albans Clock of Richard of Wallingford, antiquarian Horology, Number 4, Volume 11, Summer 1979, p. 372-384. Astronomical Clock, Originally designed by Richard, the Astronomical Clock of Richard of Wallingford, essay by Nicholas Whyte. Richard of Wallingford and the Clock of St. Albans, by Deryl Bender
25.
British Library
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The British Library is the national library of the United Kingdom and the second largest library in the world by number of items catalogued. It holds well over 150 million items from many countries, as a legal deposit library, the British Library receives copies of all books produced in the United Kingdom and Ireland, including a significant proportion of overseas titles distributed in the UK. The Library is a public body sponsored by the Department for Culture, Media. The Librarys collections include around 14 million books, along with holdings of manuscripts. In addition to receiving a copy of every publication produced in the UK and Ireland, the Library adds some three million items every year occupying 9.6 kilometres of new shelf space. Prior to 1973, the Library was part of the British Museum, the Euston Road building is classified as a Grade I listed building, of exceptional interest for its architecture and history. The British Library was created on 1 July 1973 as a result of the British Library Act 1972. Prior to this, the library was part of the British Museum. In 1983, the Library absorbed the National Sound Archive, which holds many sound and video recordings, with over a million discs, the core of the Librarys historical collections is based on a series of donations and acquisitions from the 18th century, known as the foundation collections. From 1997 to 2009 the main collection was housed in this new building. Construction work on the Newspaper Storage Building was completed in 2013, the collection has now been split between the St Pancras and Boston Spa sites. The British Library Document Supply Service and the Librarys Document Supply Collection is based on the site in Boston Spa. Collections housed in Yorkshire, comprising low-use material and the newspaper and Document Supply collections, the Library previously had a book storage depot in Woolwich, south-east London, which is no longer in use. The new library was designed specially for the purpose by the architect Colin St John Wilson, facing Euston Road is a large piazza that includes pieces of public art, such as large sculptures by Eduardo Paolozzi and Antony Gormley. It is the largest public building constructed in the United Kingdom in the 20th century, in December 2009 a new storage building at Boston Spa was opened by Rosie Winterton. The building was Grade I listed on 1 August 2015, in England, Legal Deposit can be traced back to at least 1610. The other five libraries are, the Bodleian Library at Oxford, the University Library at Cambridge, the Trinity College Library at Dublin, in 2003 the Ipswich MP Chris Mole introduced a Private Members Bill which became the Legal Deposit Libraries Act 2003. The Act extends United Kingdom legal deposit requirements to electronic documents, such as CD-ROMs, the Library also holds the Asia, Pacific and Africa Collections which include the India Office Records and materials in the languages of Asia and of north and north-east Africa
26.
Song dynasty
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The Song dynasty was an era of Chinese history that began in 960 and continued until 1279. It succeeded the Five Dynasties and Ten Kingdoms period, coincided with the Liao and Western Xia dynasties and it was the first government in world history to issue banknotes or true paper money nationally and the first Chinese government to establish a permanent standing navy. This dynasty also saw the first known use of gunpowder, as well as the first discernment of true north using a compass, the Song dynasty is divided into two distinct periods, Northern and Southern. During the Northern Song, the Song capital was in the city of Bianjing. The Southern Song refers to the period after the Song lost control of its half to the Jurchen Jin dynasty in the Jin–Song Wars. During this time, the Song court retreated south of the Yangtze, the Southern Song dynasty considerably bolstered its naval strength to defend its waters and land borders and to conduct maritime missions abroad. To repel the Jin, and later the Mongols, the Song developed revolutionary new military technology augmented by the use of gunpowder, in 1234, the Jin dynasty was conquered by the Mongols, who took control of northern China, maintaining uneasy relations with the Southern Song. Möngke Khan, the fourth Great Khan of the Mongol Empire and his younger brother Kublai Khan was proclaimed the new Great Khan, though his claim was only partially recognized by the Mongols in the west. In 1271, Kublai Khan was proclaimed the Emperor of China, after two decades of sporadic warfare, Kublai Khans armies conquered the Song dynasty in 1279. The Mongol invasion led to a reunification under the Yuan dynasty, the population of China doubled in size during the 10th and 11th centuries. The Northern Song census recorded a population of roughly 50 million, much like the Han and this data is found in the Standard Histories. However, it is estimated that the Northern Song had a population of some 100 million people and this dramatic increase of population fomented an economic revolution in pre-modern China. The expansion of the population, growth of cities, and the emergence of a national economy led to the withdrawal of the central government from direct involvement in economic affairs. The lower gentry assumed a role in grassroots administration and local affairs. Appointed officials in county and provincial centers relied upon the gentry for their services, sponsorship. Social life during the Song was vibrant, citizens gathered to view and trade precious artworks, the populace intermingled at public festivals and private clubs, and cities had lively entertainment quarters. The spread of literature and knowledge was enhanced by the expansion of woodblock printing. Technology, science, philosophy, mathematics, and engineering flourished over the course of the Song, although the institution of the civil service examinations had existed since the Sui dynasty, it became much more prominent in the Song period
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Su Song
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Su Song was the engineer of a hydro-mechanical astronomical clock tower in medieval Kaifeng, which employed the use of an early escapement mechanism. Sus clock tower featured the oldest known endless power-transmitting chain drive, called the tian ti, or celestial ladder. The clock tower had 133 different clock jacks to indicate and sound the hours, Su Songs treatise about the clock tower, Xinyi Xiangfayao, has survived since its written form in 1092 and official printed publication in 1094. The book has been analyzed by historians, such as Joseph Needham. The clock itself, however, was dismantled by the invading Jurchen army in AD1127, and although attempts were made to reassemble it, the Xinyi Xiangfayao was Sus best-known treatise, but the polymath compiled other works as well. He completed a large celestial atlas of several maps, several terrestrial maps. The latter discussed related subjects on mineralogy, zoology, botany and they thought that advanced mechanical clockworks were new to China and that these mechanisms were something valuable that Europeans could offer to the Chinese. Su Song was a Hokkien who was born in modern-day Fujian, like a contemporary, Shen Kuo, Su Song was a polymath, a person whose expertise spans a significant number of different interests. From an early age, his interests in astronomy and calendrical science led him onto a path as a state bureaucrat. In his spare time he was fond of writing poetry, which he used to praise the works of such as the painter Li Gonglin. He also was an antiquarian and collector of old artworks from previous dynasties, after serving in the Ministry of Personnel, he became a Minister of Justice in 1086. Eventually, Su rose to the post of Vice President of the Chancellery Secretariat, among many honorable positions and titles conferred upon him, Su Song was also one of the Deputy Tutors of the Heir Apparent. Historian Liu Heping states that Emperor Zhezong of Song sponsored Su Songs clocktower in 1086 in order to compete with the Liao for scientific and national superiority. In 1081, the court instructed Su Song to compile into a book the diplomatic history of Song-Liao relations, with his extensive knowledge of cartography, Su Song was able to settle a heated border dispute between the Song and Liao dynasties. Furthermore, Su Song must have taken advantage of the findings of his political rival. There were many star maps written before Songs book, but the greatest significance of these star maps by Su Song is, that they represent the oldest extant star maps in printed form. In 1070, Su Song and a team of scholars compiled and edited the Bencao Tujing, which was a treatise on pharmaceutical botany, zoology. In compiling information for pharmaceutical knowledge, Su Song worked with such scholars as Zhang Yuxi, Lin Yi, Zhang Dong
28.
Water clock
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A water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into or out from a vessel where the amount is then measured. Water clocks, along with sundials and hourglasses, are likely to be the oldest time-measuring instruments, with the exceptions being the vertical gnomon. Where and when they were first invented is not known, the bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BCE. Other regions of the world, including India and China, also have evidence of water clocks. Some authors, however, claim that water clocks appeared in China as early as 4000 BCE, some modern timepieces are called water clocks but work differently from the ancient ones. Independently, the Chinese developed their own advanced water clocks, incorporating gears, escapement mechanisms, some water clock designs were developed independently and some knowledge was transferred through the spread of trade. These early water clocks were calibrated with a sundial, a water clock uses a flow of water to measure time. If viscosity is neglected, the physical principle required to study such clocks is Torricellis law, there are two types of water clocks, inflow and outflow. In an outflow water clock, a container is filled with water, and this container has markings that are used to show the passage of time. As the water leaves the container, an observer can see where the water is level with the lines, an inflow water clock works in basically the same way, except instead of flowing out of the container, the water is filling up the marked container. As the container fills, the observer can see where the water meets the lines, according to Callisthenes, the Persians were using water clocks in 328 BC to ensure a just and exact distribution of water from qanats to their shareholders for agricultural irrigation. The use of clocks in Iran, especially in Zibad. Later they were used to determine the exact holy days of pre-Islamic religions, such as the Nowruz, Chelah, or Yaldā - the shortest, longest. The water clocks used in Iran were one of the most practical ancient tools for timing the yearly calendar, -Persian water clocks were a practical and useful tool for the qanats shareholders to calculate the length of time they could divert water to their farm. The qanat was the water source for agriculture and irrigation so a just. The Fenjaan consisted of a pot full of water and a bowl with a small hole in the center. When the bowl became full of water, it would sink into the pot, and he would record the number of times the bowl sank by putting small stones into a jar. The place where the clock was situated, and its managers, were known as khaneh Fenjaan
29.
Kaifeng
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Kaifeng, known previously by several names, is a prefecture-level city in east-central Henan, China. It was once the capital of the Song dynasty, and is one of the Eight Ancient Capitals of China, there are currently nearly 5 million people living in its metropolitan area. The postal romanization for the city is Kaifeng and its official one-character abbreviation in Chinese is 汴. Its name was originally Qifeng, but the syllable qi was changed to the essentially synonymous kai to avoid the naming taboo of Liu Qi, as with Beijing, there have been many reconstructions during its history. In 364 BC during the Warring States period, the State of Wei founded a city called Daliang as its capital in this area, during this period, the first of many canals in the area was constructed linking a local river to the Yellow River. When the State of Wei was conquered by the State of Qin, Kaifeng was destroyed and abandoned except for a market town. Early in the 7th century, Kaifeng was transformed into a commercial hub when it was connected to the Grand Canal as well as through the construction of a canal running to western Shandong. In 781 during the Tang dynasty, a new city was reconstructed and named Bian, Bian was the capital of the Later Jin, Later Han, and Later Zhou of the Five Dynasties and Ten Kingdoms period. The Song dynasty made Bian its capital when it overthrew the Later Zhou in 960, shortly afterwards, the city underwent further expansion. During the Song, when it was known as Dongjing or Bianjing, Kaifeng was the capital, typhus was an acute problem in the city. In 1049, the Youguosi Pagoda – or Iron Pagoda as it is called today – was constructed measuring 54.7 metres in height and it has survived the vicissitudes of war and floods to become the oldest landmark in this ancient city. Another Song-dynasty pagoda, Po Tower, dating from 974, has partially destroyed. Another well-known sight was the clock tower of the engineer, scientist. Kaifeng reached its peak importance in the 11th century when it was a commercial and industrial center at the intersection of four major canals. During this time, the city was surrounded by three rings of city walls and probably had a population of between 600,000 and 700,000 and it is believed that Kaifeng was the largest city in the world from 1013 to 1127. This period ended in 1127 when the city fell to Jurchen invaders during the Jingkang Incident and it subsequently came under the rule of the Jurchen Jin dynasty, which had conquered most of North China during the Jin–Song Wars. While it remained an important administrative center, only the city area inside the city wall of the early Song remained settled. One major problem associated with Kaifeng as the capital of the Song was its location
30.
Escapement
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An escapement is a device in mechanical watches and clocks that transfers energy to the timekeeping element and allows the number of its oscillations to be counted. The impulse action transfers energy to the timekeeping element to replace the energy lost to friction during its cycle. The escapement is driven by force from a spring or a suspended weight. Each swing of the pendulum or balance wheel releases a tooth of the escape wheel gear. This regular periodic advancement moves the hands forward at a steady rate. At the same time the tooth gives the timekeeping element a push, before another tooth catches on the escapements pallet, the sudden stopping of the escapements tooth is what generates the characteristic ticking sound heard in operating mechanical clocks and watches. Escapements are used elsewhere as well, manual typewriters used escapements to step the carriage as each letter was typed. The importance of the escapement in the history of technology is that it was the key invention that made the all-mechanical clock possible, oscillating timekeepers are used in every modern clock. The earliest liquid-driven escapement was described by the Greek engineer Philo of Byzantium in his technical treatise Pneumatics as part of a washstand, a counterweighted spoon, supplied by a water tank, tips over in a basin when full, releasing a spherical piece of pumice in the process. Once the spoon has emptied, it is pulled up again by the counterweight, remarkably, Philos comment that its construction is similar to that of clocks indicates that such escapement mechanisms were already integrated in ancient water clocks. In China, the Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 723 to the workings of an armillary sphere. Song dynasty horologists Zhang Sixun and Su Song duly applied escapement devices for their astronomical clock towers, according to historian Derek J. de Solla Price, the medieval Chinese escapement spread west and was the source for Western escapement technology. Hassan, a mercury escapement in a Spanish work for Alfonso X in 1277 can be traced back to earlier Arabic sources, knowledge of these mercury escapements may have spread through Europe with translations of Arabic and Spanish texts. However, none of these were true mechanical escapements, since they depended on the flow of liquid through an orifice to measure time. For example, in Su Songs clock, water flowed into a container on a pivot, the escapements role was to tip the container over each time it filled up, thus advancing the clocks wheels each time an equal quantity of water was measured out. The time between releases depended on the rate of flow, which decreased with water pressure as the level of water in the source container dropped. The development of mechanical clocks depended on the invention of an escapement which would allow a movement to be controlled by an oscillating weight. The Chinese one worked intermittently, the European, in discrete, both systems used gravity as the prime mover, but the action was very different
31.
Chain drive
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Chain drive is a way of transmitting mechanical power from one place to another. It is often used to power to the wheels of a vehicle. It is also used in a variety of machines besides vehicles. The gear is turned, and this pulls the chain putting mechanical force into the system, another type of drive chain is the Morse chain, invented by the Morse Chain Company of Ithaca, New York, United States. Sometimes the power is output by simply rotating the chain, which can be used to lift or drag objects, in other situations, a second gear is placed and the power is recovered by attaching shafts or hubs to this gear. By varying the diameter of the input and output gears with respect to each other, for example, when the bicycle pedals gear rotate once, it causes the gear that drives the wheels to rotate more than one revolution. The oldest known application of a chain appears in the Polybolos. Two flat-linked chains were connected to a windlass, which by winding back and it is here that the flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance. The chain drive itself was given power via the works of Sus water clock tank and waterwheel. Roller chain and sprockets is an efficient method of power transmission compared to belts. Although chains can be stronger than belts, their greater mass increases drive train inertia. Drive chains are most often made of metal, while belts are often rubber, plastic, urethane, or other substances. Drive belts can slip unless they have teeth, which means that the side may not rotate at a precise speed. Wear on rubber or plastic belts and their teeth is often easier to observe, one problem with roller chains is the variation in speed, or surging, caused by the acceleration and deceleration of the chain as it goes around the sprocket link by link. It starts as soon as the line of the chain contacts the first tooth of the sprocket. This contact occurs at a point below the circle of the sprocket. As the sprocket rotates, the chain is raised up to the circle and is then dropped down again as sprocket rotation continues. This rising and falling of the line is what causes chordal effect or speed variation
32.
Armillary sphere
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As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations. It was invented separately in ancient Greece and ancient China, with use in the Islamic world. With the Earth as center, a sphere is known as Ptolemaic. With the sun as center, it is known as Copernican, the flag of Portugal features an armillary sphere. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration and this section refers to labels in the diagram below. The exterior parts of machine are a compages of brass rings. The equinoctial A, which is divided into 360 degrees for showing the right ascension in degrees. The Arctic Circle E, and the Antarctic Circle F, each 23½ degrees from its respective pole at N and S.5. The equinoctial colure G, passing through the north and south poles of the heaven at N and S, the solstitial colure H, passing through the poles of the heaven, and through the solstitial points Cancer and Capricorn, in the ecliptic. Within these circular rings is a terrestrial globe J, fixed on an axis K. On this axis is fixed the flat celestial meridian L L and this flat meridian is graduated the same way as the brass meridian of the common globe, and its use is much the same. The globe may be turned by hand within this ring, so as to any given meridian upon it. The horizon is divided into 360 degrees all around its outermost edge, within which are the points of the compass, for showing the amplitude of the sun and the moon, both in degrees and points. The celestial meridian L passes through two notches in the north and south points of the horizon, as in a common globe, both here, if the globe be turned round, the horizon and meridian turn with it. At the south pole of the sphere is a circle of 25 hours, fixed to the rings, in the box T are two wheels and two pinions, whose axes come out at V and U, either of which may be turned by the small winch W. If the earthly globe be turned, the hour-index goes round its hour-circle, but if the sphere be turned, and so, by this construction, the machine is equally fitted to show either the real motion of the earth, or the apparent motion of the heaven. — Then turn the winch, and observe when the sun or moon rise and set in the horizon, throughout Chinese history, astronomers have created celestial globes to assist the observation of the stars. The Chinese also used the sphere in aiding calendrical computations and calculations
33.
Astronomy in the medieval Islamic world
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Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age, and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa and these included Greek, Sassanid, and Indian works in particular, which were translated and built upon. Islamic astronomy also had an influence on Chinese astronomy and Malian astronomy, a significant number of stars in the sky, such as Aldebaran, Altair and Deneb, and astronomical terms such as alidade, azimuth, and nadir, are still referred to by their Arabic names. A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed. These observations were based on the rising and setting of stars. Anwa continued to be developed after Islamization by the Arabs, where Islamic astronomers added mathematical methods to their empirical observations, according to David King, after the rise of Islam, the religious obligation to determine the qibla and prayer times inspired more progress in astronomy for centuries. The first astronomical texts that were translated into Arabic were of Indian and Persian origin, another text translated was the Zij al-Shah, a collection of astronomical tables compiled in Sasanid Persia over two centuries. Fragments of texts during this period indicate that Arabs adopted the function in place of the chords of arc used in Greek trigonometry. The House of Wisdom was an established in Baghdad under Abbasid caliph Al-Mamun in the early 9th century. From this time, independent investigation into the Ptolemaic system became possible, Astronomical research was greatly supported by the Abbasid caliph al-Mamun through The House of Wisdom. Baghdad and Damascus became the centers of such activity, the caliphs not only supported this work financially, but endowed the work with formal prestige. The first major Muslim work of astronomy was Zij al-Sindh by al-Khwarizmi in 830, the work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Ptolemaic concepts into Islamic sciences and this work also marks the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others, al-Khwarizmis work marked the beginning of nontraditional methods of study and calculations. In 850, al-Farghani wrote Kitab fi Jawani, the book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy based on findings of earlier Arab astronomers, al-Farghani gave revised values for the obliquity of the ecliptic, the precessional movement of the apogees of the sun and the moon, and the circumference of the earth. The book was circulated through the Muslim world, and even translated into Latin. The period when a distinctive Islamic system of astronomy flourished, the period began as the Muslim astronomers began questioning the framework of the Ptolemaic system of astronomy
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Muslim inventions
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Such innovations are listed below, in chronological order. 8th century Tin-glazing, The tin-glazing of ceramics was an imitation of white Chinese stoneware by local Islamic potters in 8th-century Basra, the first examples of this technique can be found as blue-painted ware in 8th-century Basra. The oldest fragments found to-date were excavated from the palace of Samarra about 80 kilometres north of Baghdad, 9th century Lusterware, Lustre decoration was invented during Roman and Coptic Egypt during the centuries preceding the rise of Islam. Lustre glazes were applied to pottery in Mesopotamia in the 9th century, earlier uses of lustre are known. Frequency analysis in cryptology, the first known recorded explanation of cryptanalysis was given by Al-Kindi and this treatise includes the first description of the method of frequency analysis. 10th century Vertical-axle windmill, A small wind wheel operating an organ is described as early as the 1st century AD by Hero of Alexandria, the first vertical-axle windmills were eventually built in Sistan, Persia as described by Muslim geographers. These windmills had long vertical driveshafts with rectangle shaped blades and they may have been constructed as early as the time of the second Rashidun caliph Umar, though some argue that this account may have been a 10th-century amendment. Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind grains and draw up water, horizontal axle windmills of the type generally used today, however, were developed in Northwestern Europe in the 1180s. 11th century Mercuric chloride, used to disinfect wounds, elemental mercury was known to the ancient Greeks, Romans, Chinese, and Hindus before Arabs. 12th century Bridge mill, The bridge mill was a type of watermill that was built as part of the superstructure of a bridge. The earliest record of a mill is from Córdoba, Spain in the 12th century. Hybrid trebuchet, The term Al-Ghadban was applied to the hybrid trebuchet, though the usage of the term was not consistent, the first record of a counterweight trebuchet was in the 12th century from Mardi ibn Ali al-Tarsusi while talking of the conquests of Saladin. 13th century Rocket technology was adopted from China in the 13th century,1275, Hasan al-Rammah described. an egg which moves itself and burns. Fritware, It refers to a type of pottery which was first developed in the Near East, beginning in the late 1st millennium, for which frit was a significant ingredient. A recipe for fritware dating to c.1300 AD written by Abu’l Qasim reports that the ratio of quartz to frit-glass to white clay is 10,1,1 and this type of pottery has also been referred to as stonepaste and faience among other names. A 9th-century corpus of proto-stonepaste from Baghdad has relict glass fragments in its fabric, hispano-Moresque ware was distinguished from the pottery of Christendom by the Islamic character of its decoration. 15th century Coffee, The ancestors of todays Oromo people in a region of Kaffa in Ethiopia were believed to have been the first to recognize the energizing effect of the coffee plant and it was in Yemen that coffee beans were first roasted and brewed as they are today. From Mocha, coffee spread to Egypt and North Africa, and by the 16th century, it had reached the rest of the Middle East, Persia and Turkey
35.
Observatory
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An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed, historically, observatories were as simple as containing an astronomical sextant or Stonehenge. Astronomical observatories are mainly divided into four categories, space based, airborne, ground based, ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum. Most optical telescopes are housed within a dome or similar structure, Telescope domes have a slit or other opening in the roof that can be opened during observing, and closed when the telescope is not in use. In most cases, the upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky. Radio telescopes usually do not have domes, for optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution. The ideal locations for modern observatories are sites that have dark skies, a percentage of clear nights per year, dry air. At high elevations, the Earths atmosphere is thinner, thereby minimizing the effects of atmospheric turbulence, sites that meet the above criteria for modern observatories include the southwestern United States, Hawaii, Canary Islands, the Andes, and high mountains in Mexico such as Sierra Negra. Major optical observatories include Mauna Kea Observatory and Kitt Peak National Observatory in the USA, Roque de los Muchachos Observatory in Spain, and Paranal Observatory in Chile. Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the part of Eastern Antarctica. This location provides the least atmospheric disturbances and best visibility, beginning in 1930s, radio telescopes have been built for use in the field of radio astronomy to observe the Universe in the radio portion of the electromagnetic spectrum. Since the mid-20th century, a number of observatories have been constructed at very high altitudes, above 4. The largest and most notable of these is the Mauna Kea Observatory, the Chacaltaya Astrophysical Observatory in Bolivia, at 5,230 m, was the worlds highest permanent astronomical observatory from the time of its construction during the 1940s until 2009. It has now surpassed by the new University of Tokyo Atacama Observatory. As a result, the resolution of space telescopes such as the Hubble Space Telescope is often much smaller than a ground-based telescope with a similar aperture. However, all these advantages do come with a price, Space telescopes are much more expensive to build than ground-based telescopes. Due to their location, space telescopes are also difficult to maintain. The Hubble Space Telescope was serviced by the Space Shuttle while many other space telescopes cannot be serviced at all, Airborne observatories have the advantage of height over ground installations, putting them above most of the Earths atmosphere
36.
Castle clock
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Clock towers are a specific type of building which houses a turret clock and has one or more clock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another building, Clock towers are a common sight in many parts of the world with some being iconic buildings. One example is the Elizabeth Tower in London, there are many structures which may have clocks or clock faces attached to them and some structures have had clocks added to an existing structure. According to the Council on Tall Buildings and Urban Habitat a building is defined as a building if at least fifty percent of its height is made up of plates containing habitable floor area. Structures that do not meet this criterion, are defined as towers, not all clocks on buildings therefore make the building into a clock tower. The mechanism inside the tower is known as a turret clock and it often marks the hour by sounding large bells or chimes, sometimes playing simple musical phrases or tunes. Although clock towers are today mostly admired for their aesthetics, they served an important purpose. Before the middle of the century, most people did not have watches. The first clocks didnt have faces, but were solely striking clocks and they were therefore placed in towers so the bells would be audible for a long distance. Clock towers were placed near the centres of towns and were often the tallest structures there, as clock towers became more common, the designers realized that a dial on the outside of the tower would allow the townspeople to read the time whenever they wanted. The use of clock towers dates back to the antiquity, the earliest clock tower was the Tower of the Winds in Athens which featured eight sundials. In its interior, there was also a clock, driven by water coming down from the Acropolis. In Song China, a clock tower was designed by Su Song and erected at Kaifeng in 1088. In England, a clock was put up in a tower, the medieval precursor to Big Ben, at Westminster, in 1288. Al-Jazari constructed a clock and described it in his Book of Knowledge of Ingenious Mechanical Devices in 1206. It was about 3.3 metres high, and had multiple functions alongside timekeeping, line synchronous tower clocks were introduced in the United States in the 1920s. Some clock towers have become famous landmarks, the Allen-Bradley Clock Tower in Milwaukee, Wisconsin has the largest four faced clock in the world, with clock diameter 40 ft 3 1⁄2 in, it is 283 ft tall. The Elizabeth Tower has the largest chiming clock in the world, the tallest freestanding clock tower in the world is the Joseph Chamberlain Memorial Clock Tower at the University of Birmingham in Birmingham, United Kingdom
37.
Ismail al-Jazari
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Badīʿ az-Zaman Abū l-ʿIzz ibn Ismāʿīl ibn ar-Razāz al-Jazarī was an Islamic polymath, a scholar, inventor, mechanical engineer, artisan, artist and mathematician. Nothing is known about early life. He is famed for authoring the Book of Knowledge of Ingenious Mechanical Devices, according to Mayr, the books style resembles that of a modern do-it-yourself book. Some of his devices were inspired by earlier devices, such as one of his water clocks. He also cites the influence of the Banū Mūsā brothers for his fountains, al-Saghani for the design of a candle clock, and Hibatullah ibn al-Husayn for musical automata. A camshaft, a shaft to which cams are attached, was introduced in 1206 by al-Jazari, the cam and camshaft also appeared in European mechanisms from the 14th century. The eccentrically mounted handle of the rotary quern-stone in fifth century BCE Spain that spread across the Roman Empire constitutes a crank, the earliest evidence of a crank and connecting rod mechanism dates to the 3rd century AD Hierapolis sawmill in the Roman Empire. The crank also appears in the century in several of the hydraulic devices described by the Banū Mūsā brothers in their Book of Ingenious Devices. In 1206, al-Jazari invented an early crankshaft, which he incorporated with a crank-connecting rod mechanism in his twin-cylinder pump and he used the crankshaft with a connecting rod in two of his water-raising machines, the crank-driven saqiya chain pump and the double-action reciprocating piston suction pump. His water pump also employed the first known crank-slider mechanism, al-Jazari invented a method for controlling the speed of rotation of a wheel using an escapement mechanism. According to Donald Hill, al-Jazari described several early mechanical controls, including a metal door, a combination lock. A segmental gear is a piece for receiving or communicating reciprocating motion from or to a cogwheel, consisting of a sector of a gear, or ring, having cogs on the periphery. It was in these machines that he introduced his most important ideas. The first known use of a crankshaft in a pump was in one of al-Jazaris saqiya machines. The concept of minimizing intermittent working is also first implied in one of al-Jazaris saqiya chain pumps, al-Jazari also constructed a water-raising saqiya chain pump which was run by hydropower rather than manual labour, though the Chinese were also using hydropower for chain pumps prior to him. Saqiya machines like the ones he described have been supplying water in Damascus since the 13th century up until modern times, and were in everyday use throughout the medieval Islamic world. This pump is driven by a wheel, which drives, through a system of gears. The pistons work in horizontally opposed cylinders, each provided with valve-operated suction, the delivery pipes are joined above the centre of the machine to form a single outlet into the irrigation system
38.
Astrolabe
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An astrolabe is an elaborate inclinometer, historically used by astronomers and navigators, to measure the inclined position in the sky of a celestial body, day or night. It can thus be used to identify stars or planets, to determine local latitude given local time and vice versa, to survey and it was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and the Renaissance for all these purposes. While the astrolabe is effective for determining latitude on land or calm seas, the mariners astrolabe was developed to solve that problem. OED gives the translation star-taker for the English word astrolabe and traces it, through medieval Latin, to the Greek word astrolabos from astron star, in the medieval Islamic world the word asturlab was given various etymologies. In Arabic texts, the word is translated as akhdh al-kawakib which corresponds to an interpretation of the Greek word, al-Biruni quotes and criticizes the medieval scientist Hamzah al-Isfahani who had stated, asturlab is an arabization of this Persian phrase. In medieval Islamic sources, there is also a fictional and popular etymology of the words as lines of lab, in this popular etymology, Lab is a certain son of Idris. This etymology is mentioned by a 10th-century scientist named al-Qummi but rejected by al-Khwarizmi, Lab in Arabic also means sun and black stony places. An early astrolabe was invented in the Hellenistic world by Apollonius of Perga, a marriage of the planisphere and dioptra, the astrolabe was effectively an analog calculator capable of working out several different kinds of problems in spherical astronomy. Theon of Alexandria wrote a treatise on the astrolabe. Some historians attribute the invention to Hypatia, the daughter of Theon of Alexandria, noting that Synesius. Astrolabes continued in use in the Greek-speaking world throughout the Byzantine period, about 550 AD the Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant Greek treatise on the instrument. In addition, Severus Sebokht, a bishop who lived in Mesopotamia, Astrolabes were further developed in the medieval Islamic world, where Muslim astronomers introduced angular scales to the astrolabe, adding circles indicating azimuths on the horizon. It was widely used throughout the Muslim world, chiefly as an aid to navigation and as a way of finding the Qibla, the first person credited with building the astrolabe in the Islamic world is reportedly the 8th-century mathematician Muhammad al-Fazari. The mathematical background was established by the Muslim astronomer Albatenius in his treatise Kitab az-Zij, the earliest surviving dated astrolabe is dated AH315. In the Islamic world, astrolabes were used to find the times of sunrise and the rising of fixed stars, to help schedule morning prayers. In the 10th century, al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, navigation, surveying, timekeeping, prayer, Salat, Qibla, etc. The spherical astrolabe, a variation of both the astrolabe and the sphere, was invented during the Middle Ages by astronomers and inventors in the Islamic world. The earliest description of the spherical astrolabe dates back to Al-Nayrizi, in the 12th century, Sharaf al-Dīn al-Tūsī invented the linear astrolabe, sometimes called the staff of al-Tusi, which was a simple wooden rod with graduated markings but without sights
39.
Ibn al-Shatir
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Ibn al-Shatir or Ibn ash-Shatir was an Arab astronomer. He worked as muwaqqit in the Umayyad Mosque in Damascus and constructed a magnificent sundial for its minaret in 1371/72 and his most important astronomical treatise was kitab nihayat al-sul fi tashih al-usul. In it he drastically reformed the Ptolemaic models of the Sun, Moon and planets, eliminating the eccentric, although his system was firmly geocentric, the mathematical details of his system were identical to those in Copernicuss De revolutionibus. It is unknown whether Copernicus read ibn al-Shatir, list of Arab scientists and scholars Islamic scholars Fernini, Ilias. A Bibliography of Scholars in Medieval Islam, abu Dhabi Cultural Foundation,1998 Kennedy, Edward S. Kennedy, Edward S. and Ghanem, Imad, the Life and Work of Ibn al-Shatir, an Arab Astronomer of the Fourteenth Century. Aleppo, History of Arabic Science Institute, University of Aleppo,1976, the Solar and Lunar Theory of Ibn ash-Shatir, A Pre-Copernican Copernican Model. Roberts, Victor and Edward S. Kennedy, the Planetary Theory of Ibn al-Shatir. Theory and Observation in Islamic Astronomy, The Work of Ibn al-Shatir of Damascus, journal for the History of Astronomy,18, 35-43. Science in Medieval Islam, an illustrated introduction, University of Texas Press, Austin,1995. ISBN 0-292-78149-0 ISBN 0-292-78147-4 King, David A. Ibn al‐Shāṭir, Science in Medieval Islam by Howard R. Turner The Lights of the Stars
40.
St Albans
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St Albans /sənt ˈɔːlbənz/, /seɪn. / is a city in Hertfordshire, England, and the major urban area in the City and District of St Albans. It lies east of Hemel Hempstead and west of Hatfield, about 19 miles north-northwest of London,8 miles southwest of Welwyn Garden City and 11 miles south-southeast of Luton. St Albans was the first major town on the old Roman road of Watling Street for travellers heading north and it is a historic market town and is now a dormitory town within the London commuter belt and the Greater London Built-up Area. St Albans takes its name from the first British saint, Alban, Alban met a Christian priest fleeing from his persecutors and sheltered him in his house, where he became so impressed with the priests piety that he converted to Christianity. When the authorities searched Albans house, he put on the priests cloak, consequently, he was sentenced to endure the punishments that were to be inflicted upon the priest, unless he renounced Christianity. Alban refused and was taken for execution, in later legends, his head rolled downhill after execution and a well sprang up where it stopped. The name Verulamium is Celtic, meaning settlement over or by the marsh, the town was on Prae Hill,2 km to the west of modern St Albans, now covered by the village of St. Michaels, Verulamium Park and the Gorhambury Estate. It is believed that the capital was moved to the site by Tasciovanus. Cunobelinus may have constructed Beech Bottom Dyke, an earthwork near the settlement whose significance is uncertain. It grew steadily, by the early 3rd century, it covered an area of about 125 acres, behind a deep ditch and wall. Verulamium contained a forum, basilica and a theatre, much of which were damaged during two fires, one in 155 and the other in around 250, one of the few extant Roman inscriptions in Britain is found on the remnants of the forum. The town was rebuilt in stone rather than timber at least twice over the next 150 years, occupation by the Romans ended between 400 and 450. St Alban was probably buried outside the city walls in a Roman cemetery near the present Cathedral and his hillside grave became a place of pilgrimage. Recent investigation has uncovered a basilica there, indicating the oldest continuous site of Christian worship in Great Britain, in 429 Germanus of Auxerre visited the church and subsequently promoted the cult of St Alban. More remains under the agricultural land which have never been excavated were for a while seriously threatened by deep ploughing. After the Roman withdrawal the town, became the centre of the territory or regio of the Anglo-Saxon Waeclingas tribe, St Albans Abbey and the associated Anglo-Saxon settlement were founded on the hill outside the Roman city where it was believed St Alban was buried. An archaeological excavation in 1978, directed by Martin Biddle, failed to find Roman remains on the site of the chapter house. The medieval town grew on the hill to the east of Wæclingacaester where the Benedictine Abbey of St Albans was founded by Ulsinus in 793, there is some evidence that the original site was higher up the hill than the present building, which was begun in 1077
41.
Padua
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Padua is a city and comune in Veneto, northern Italy. It is the capital of the province of Padua and the economic, the city is sometimes included, with Venice and Treviso, in the Padua-Treviso-Venice Metropolitan Area, which has a population of c. Padua stands on the Bacchiglione River,40 kilometres west of Venice and 29 km southeast of Vicenza, the Brenta River, which once ran through the city, still touches the northern districts. Its agricultural setting is the Venetian Plain, to the citys south west lies the Euganaean Hills, praised by Lucan and Martial, Petrarch, Ugo Foscolo, and Shelley. It hosts the University of Padua, founded in 1222, where Galileo Galilei was a lecturer, Padua is the setting for most of the action in Shakespeares The Taming of the Shrew. There is a play by the Victorian writer Oscar Wilde, titled The Duchess Of Padua, the original significance of the Roman name Patavium is uncertain. It may be connected with the ancient name of the River Po, additionally, the root pat-, in the Indo-European language may refer to a wide open plain as opposed to nearby hills. The ending -ium, signifies the presence of villages that have united themselves together, Padua claims to be the oldest city in northern Italy. According to a tradition dated at least to the time of Virgils Aeneid and to Livys Ab Urbe Condita, Padua was founded in around 1183 BC by the Trojan prince Antenor. After the Fall of Troy, Antenor led a group of Trojans and their Paphlagonian allies, the Eneti or Veneti, thus, when a large ancient stone sarcophagus was exhumed in the year 1274, officials of medieval commune declared the remains within to be those of Antenor. Nevertheless, archeological remains confirm a date for the foundation of the center of the town to between the 11th and 10th centuries BC. The Roman historian Livy records an invasion of the Spartan king Cleonimos around 302 BC. The Spartans came up the river but were defeated by the Veneti in a naval battle, still later, the Veneti of Padua successfully defended themselves against the aggression of Etruscans and Gauls. According to Livy and Silius Italicus, the Veneti, including those of Padua, formed an alliance with the Romans by 226 BC, against their common enemy, men from Padua fought and died besides the Romans at Cannae. As the Romans advanced northward, Padua was gradually assimilated into the Roman Republic, in 175 BC, Padua requested the aid of Rome in putting down a local civil war. In 91 BC, Padua, along with cities of the Veneti. Around 49 BC, Padua was made a Roman municipium under the Lex Julia Municipalis and its citizens ascribed to the Roman tribe, at that time the population of the city was perhaps 40,000. The city was reputed for its excellent breed of horses and the wool of its sheep, in fact, the poet Martial remarks on the thickness of the tunics made there
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London
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London /ˈlʌndən/ is the capital and most populous city of England and the United Kingdom. Standing on the River Thames in the south east of the island of Great Britain and it was founded by the Romans, who named it Londinium. Londons ancient core, the City of London, largely retains its 1. 12-square-mile medieval boundaries. London is a global city in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism. It is crowned as the worlds largest financial centre and has the fifth- or sixth-largest metropolitan area GDP in the world, London is a world cultural capital. It is the worlds most-visited city as measured by international arrivals and has the worlds largest city airport system measured by passenger traffic, London is the worlds leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. Londons universities form the largest concentration of education institutes in Europe. In 2012, London became the first city to have hosted the modern Summer Olympic Games three times, London has a diverse range of people and cultures, and more than 300 languages are spoken in the region. Its estimated mid-2015 municipal population was 8,673,713, the largest of any city in the European Union, Londons urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census. The citys metropolitan area is the most populous in the EU with 13,879,757 inhabitants, the city-region therefore has a similar land area and population to that of the New York metropolitan area. London was the worlds most populous city from around 1831 to 1925, Other famous landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Pauls Cathedral, Tower Bridge, Trafalgar Square, and The Shard. The London Underground is the oldest underground railway network in the world, the etymology of London is uncertain. It is an ancient name, found in sources from the 2nd century and it is recorded c.121 as Londinium, which points to Romano-British origin, and hand-written Roman tablets recovered in the city originating from AD 65/70-80 include the word Londinio. The earliest attempted explanation, now disregarded, is attributed to Geoffrey of Monmouth in Historia Regum Britanniae and this had it that the name originated from a supposed King Lud, who had allegedly taken over the city and named it Kaerlud. From 1898, it was accepted that the name was of Celtic origin and meant place belonging to a man called *Londinos. The ultimate difficulty lies in reconciling the Latin form Londinium with the modern Welsh Llundain, which should demand a form *lōndinion, from earlier *loundiniom. The possibility cannot be ruled out that the Welsh name was borrowed back in from English at a later date, and thus cannot be used as a basis from which to reconstruct the original name. Until 1889, the name London officially applied only to the City of London, two recent discoveries indicate probable very early settlements near the Thames in the London area
43.
Verge escapement
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Verge escapements were used from the 14th century until the mid 19th century in clocks and pocketwatches. The name verge comes from the Latin virga, meaning stick or rod and its invention is important in the history of technology, because it made possible the development of all-mechanical clocks. Oscillating timekeepers are used in all modern timepieces, the verge escapement dates from 13th-century Europe, where its invention led to the development of the first all-mechanical clocks. Starting in the 13th century, large tower clocks were built in European town squares, cathedrals and they kept time by using the verge escapement to drive the foliot, a primitive type of balance wheel, causing it to oscillate back and forth. The foliot was a bar with weights on the ends. The verge probably evolved from the alarum, which used the mechanism to ring a bell and had appeared centuries earlier. It is believed that sometime in the late 13th century the verge escapement mechanism was applied to tower clocks, creating the first mechanical clock. In spite of the fact that these clocks were celebrated objects of pride which were written about at the time. None of the mechanisms have survived unaltered. Sources differ on which was the first clock known to be mechanical, another is the clock built at the Palace of the Visconti, Milan, Italy, in 1335. However, there is agreement that mechanical clocks existed by the late 13th century and it consisted of a pair of escape wheels on the same axle, with alternating radial teeth. The verge rod was suspended between them, with a short crosspiece that rotated first in one direction and then the other as the staggered teeth pushed past, although no other example is known, it is possible that this design preceded the verge in clocks. For the first two hundred years or so of the existence, the verge was the only escapement used in mechanical clocks. Early verge clocks were probably no more accurate than the water clocks. By the mid-17th century, when the pendulum replaced the foliot, most of the gross inaccuracy of the early verge and foliot clocks was not due to the escapement itself, but to the foliot oscillator. The first use of pendulums in clocks around 1656 suddenly increased the accuracy of the clock from hours a day to minutes a day. Most clocks were rebuilt with their foliots replaced by pendulums, to the extent that it is difficult to find original verge, a similar increase in accuracy in verge watches followed the introduction of the balance spring in 1658. The verge escapement consists of a wheel shaped like a crown, with sawtooth-shaped teeth protruding axially toward the front, and with its axis oriented horizontally
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Pendulum
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A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, when released, the restoring force combined with the pendulums mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a degree on the amplitude. Pendulums are also used in instruments such as accelerometers and seismometers. Historically they were used as gravimeters to measure the acceleration of gravity in geophysical surveys, the word pendulum is new Latin, from the Latin pendulus, meaning hanging. The simple gravity pendulum is a mathematical model of a pendulum. This is a weight on the end of a massless cord suspended from a pivot, when given an initial push, it will swing back and forth at a constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines and it is independent of the mass of the bob. For small swings the period of swing is approximately the same for different size swings, that is and this property, called isochronism, is the reason pendulums are so useful for timekeeping. Successive swings of the pendulum, even if changing in amplitude, for larger amplitudes, the period increases gradually with amplitude so it is longer than given by equation. For example, at an amplitude of θ0 = 23° it is 1% larger than given by, the period increases asymptotically as θ0 approaches 180°, because the value θ0 = 180° is an unstable equilibrium point for the pendulum. The length L used to calculate the period of the simple pendulum in eq. above is the distance from the pivot point to the center of mass of the bob. Any swinging rigid body free to rotate about a horizontal axis is called a compound pendulum or physical pendulum. The appropriate equivalent length L for calculating the period of any such pendulum is the distance from the pivot to the center of oscillation. This point is located under the center of mass at a distance from the pivot traditionally called the radius of oscillation, if most of the mass is concentrated in a relatively small bob compared to the pendulum length, the center of oscillation is close to the center of mass. Substituting this expression in above, the period T of a pendulum is given by T =2 π I m g R for sufficiently small oscillations. For example, a rigid rod of length L pivoted about one end has moment of inertia I = m L2 /3
45.
Gros Horloge
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The Great-Clock is a fourteenth-century astronomical clock in Rouen, Normandy. The clock is installed in a Renaissance arch crossing the Rue du Gros-Horloge, the mechanism is one of the oldest in France, the movement was made in 1389. The clock was constructed without a dial, with one revolution of the hour-hand representing twenty-four hours. The movement is cast in iron, and at approximately twice the size of the Wells Cathedral clock. A facade was added in 1529 when the clock was moved to its current position, the Renaissance facade represents a golden sun with 24 rays on a starry blue background. The dial measures 2.5 metres in diameter, the phases of the moon are shown in the oculus of the upper part of the dial. It completes a rotation in 29 days. The week days are shown in an opening at the base of the dial with allegorical subjects for each day of the week, the mechanism was electrified in the 1920s and it was restored in 1997. The Gros Horolge has featured in paintings by J. M. W. Turner, Turner watercolour Rouen, the Gros-Horloge, with the Towers of the Cathedral Beyond, c.1832
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Rouen
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Rouen is a city on the River Seine in the north of France. It is the capital of the region of Normandy, formerly one of the largest and most prosperous cities of medieval Europe, Rouen was the seat of the Exchequer of Normandy during the Middle Ages. It was one of the capitals of the Anglo-Norman dynasties, which ruled both England and large parts of modern France from the 11th to the 15th centuries. The population of the area at the 2007 census was 532,559. People from Rouen are known as Rouennais, Rouen and its metropolitan area of 70 suburban communes form the Agglomeration community of Rouen-Elbeuf-Austreberthe, with 494,382 inhabitants at the 2010 census. Rouen was founded by the Gaulish tribe of Veliocasses, who controlled an area in the lower Seine valley. The Gauls named the settlement Ratumacos and the Romans called it Rotomagus, Roman Rotomagus was the second city of Gallia Lugdunensis, after Lugdunum. In the 5th century, it became the seat of a bishopric, in the 10th century Rouen became the capital of the Duchy of Normandy and the residence of the dukes, until William the Conqueror established his castle at Caen. During the early 12th century the population reached 30,000. In 1150, Rouen received its charter, which permitted self-government. During the 12th century, Rouen was probably the site of a Jewish yeshiva, at that time, about 6,000 Jews lived in the town, comprising about 20% of the total population. The well-preserved remains of a medieval Jewish building, that could be a yeshiva, were discovered in the 1970s under the Rouen Law Courts. In 1200, a destroyed part of Rouens Romanesque cathedral, leaving just St Romains tower, the side porches of its front. New work on the present Gothic cathedral of Rouen began, in the nave, transept, choir, on 24 June 1204, Philip Augustus entered Rouen and annexed Normandy to the French Kingdom. The fall of Rouen meant the end of Normandys sovereign status and he demolished the Norman castle and replaced it with his own, the Château Bouvreuil, built on the site of the Gallo-Roman amphitheatre. A textile industry developed based on wool imported from England, competing with the northern County of Flanders, the city found its market niche in the Champagne fairs. Rouen also depended on the traffic of the Seine for its prosperity. Wine and wheat were exported to England, with tin and wool received in return, in the late 13th century urban strife threatened the city, in 1291, the mayor was assassinated and noble residences in the city were pillaged
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Wells Cathedral clock
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The Wells Cathedral clock is an astronomical clock in the north transept of Wells Cathedral, England. The clock is one of the group of famous 14th to 16th century astronomical clocks to be found in the West of England. The surviving mechanism, dated to between 1386 and 1392, was replaced in the 19th century, and was moved to the Science Museum in London. The dial represents the view of the universe, with sun. It may be unique in showing a model of the pre-Copernican universe. Another dial is mounted on the wall, driven from the same mechanism. This was first installed in the 14th or 15th centuries, but has been restored a number of times, the dial proposes a model of the universe. Against a background of stars, the sun moves in a circle, and indicates the time using the 24-hour analogue dial, noon is at the top of the dial reflecting the position of the sun in the sky at this time. In the corners, four angels hold the four cardinal winds and these may be generating the power that makes the universe operate. The minutes are indicated by a star on the ring inside. The inner circle shows the moon, a pointer indicates the age of the moon, between 1 and 30 days. The black and white disk above the shows the moons phase. The white disk rotates once in a synodic month, the inscription around the moon phase indicator says sphericus archetypum globus hic monstrat microcosmum, which translates as This spherical globe here shows the archetypal microcosm. Howgrave-Graham suggests that the scribe erroneously put microcosmum, when macrocosmum is the obvious word. Opposite the moon circle is a weighted pivoted disc, containing a painting of Phoebe. The inscription reads, Sic peragrat Phobe, or So progresses Phoebe, at the centre of the dial, the ball represents the earth, and the clouds suggest the same. Above the clock and to the right is a figure, known as Jack Blandifers, a set of jousting knights also chase each other every 15 minutes. There are mentions of a clock at Wells during the first half of the 14th century, in 1388, Bishop Ralph Erghum moved from Salisbury to Wells
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Oculus
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An oculus is a circular opening in the centre of a dome or in a wall. Originating in antiquity, it is a feature of Byzantine and Neoclassical architecture and it is also known as an œil de boeuf from the French, or simply a bulls-eye. The oculus was used by the Romans, one of the finest examples being that in the dome of the Pantheon, open to the weather, it allows rain to enter and fall to the floor, where it is carried away through drains. Though the opening looks small, it actually has a diameter of 27 ft allowing it to light the building just as the sun lights the earth, the rain also keeps the building cool during the hot summer months. Pliny in his Natural history call counters also oculus, oculi, the oculus was widely used in the architecture of the Byzantine Empire. It was applied to buildings in Syria in the 5th and 6th centuries, in Constantinoples Myrelaion Church, there are two oculi above the stringcourse on both lateral facades. Early examples of the oculus in Renaissance architecture can be seen in Florence Cathedral, in the nave clerestorey, since the revival of dome construction beginning in the Italian Renaissance, open oculi have been replaced by light-transmitting cupolas and other round windows, openings, and skylights. They can be seen in the pediments of Palladios Villa Rotonda, use of oculus windows became more popular in Baroque architecture. Widely used by Neo-Palladian architects including Colen Campbell, one can be seen in the dome of Thomas Jeffersons Rotunda at the University of Virginia
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