Anarmillary sphere (variations are known assphericalastrolabe,armilla, orarmil) is a model ofobjects in the sky (on thecelestial sphere), consisting of a spherical framework ofrings, centered onEarth or theSun, that represent lines ofcelestial longitude and latitude and other astronomically important features, such as theecliptic. As such, it differs from acelestial globe, which is a smooth sphere whose principal purpose is to map theconstellations. It was invented separately, inancient China possibly as early as the 4th century BC andancient Greece during the 3rd century BC, with later uses in theIslamic world andMedieval Europe.
With the Earth as center, an armillary sphere is known asPtolemaic. With the Sun as center, it is known asCopernican.[1]
Theflag of Portugal features an armillary sphere. The armillary sphere is also featured in Portugueseheraldry, associated with thePortuguese discoveries during theAge of Exploration.Manuel I of Portugal, for example, took it as one of his symbols where it appeared on his standard, and on early Chinese exportceramics made for the Portuguese court. In the flag of theEmpire of Brazil, the armillary sphere is also featured.
TheBeijing Capital International Airport Terminal 3 features a large armillary sphere metal sculpture as an exhibit ofChinese inventions for international and domestic visitors.
The exterior parts of this machine are acompages [or framework] of brass rings, which represent the principal circles of the heavens:
In the north pole of the ecliptic is a nutb, to which is fixed one end of the quadrantal wire. To the other end is a small sunY, which is carried around the eclipticB—B, by turning the nut. In the south pole of the ecliptic is a pind, on which another quadrantal wire is situated, with a small moonΖ upon it, which may be moved around by hand. A mechanism causes the moon to move in an orbit which crosses the ecliptic at an angle of 51⁄3 degrees, to opposite points called thelunar nodes, and allows for shifting these points backward in the ecliptic, as the lunar nodes shift in the heavens.
Within these circular rings is a small terrestrial globeI, fixed on an axisK, which extends from the north and south poles of the globe atn ands, to those of the celestial sphere atN andS. On this axis the flat celestial meridianL is fixed, which may be set directly over the meridian of any place on the globe, so as to keep over the same meridian upon it. This flat meridian is graduated the same way as the brass meridian of the common globe, and its use is much the same.
To this globe is fitted the movable horizonM, so as to turn upon the two strong wires proceeding from its east and west points to the globe and entering the globe at the opposite points off its equator, which is a movable brass ring set into the globe in a groove all around its equator. The globe may be turned by hand within this ring, so as to place any given meridian upon it, directly under the celestial meridianL. The horizon is divided into 360 degrees all around its outermost edge, within which are the points of thecompass, for showing the amplitude of the sun and the moon, both in degrees and points. The celestial meridianL passes through two notches in the north and south points of the horizon, as in a common globe: if the globe is turned around, the horizon and meridian turn with it. At the south pole of the sphere is a circle of 25 hours, fixed to the rings. On the axis is an index which goes around that circle, if the globe is turned around its axis.
The globe assembly is supported on a pedestalN, and may be elevated or depressed upon the jointO, to any number of degrees from 0 to 90 by means of the arcP, which is fixed in the strong brass armQ. The globe assembly slides in the upright pieceR, in which is a screw atr, to fix it at any proper elevation.
In the boxT are two wheels (as in Dr Long's sphere) and two pinions, whose axes come out atV andU; either of which may be turned by the small winchW. When the winch is put upon the axisV, and turned backward, the terrestrial globe, with its horizon and celestial meridian, keep at rest; and the whole sphere of circles turns round from east, by south, to west, carrying the sunY, and moonZ, round the same way, and causing them to rise above and set below the horizon. But when the winch is put upon the axisU, and turned forward, the sphere with the sun and moon keep at rest; and the earth, with its horizon and meridian, turn round from horizon to the sun and moon, to which these bodies came when the earth kept at rest, and they were carried round it; showing that they rise and set in the same points of the horizon, and at the same times in the hour circle, whether the motion be in the earth or in the heaven. If the earthly globe be turned, the hour-index goes round its hour-circle; but if the sphere be turned, the hour-circle goes round below the index.
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 heavens.
To reset the sphere for use, one must first slacken the screwr in the upright stemR, and taking hold of the armQ, move it up or down until the given degree of latitude for any place lies at the side of the stemR; then the axis of the sphere will be properly elevated, so as to stand parallel to the axis of the terrestrial globe, if the globe assembly is to be aligned to north and south by a small compass: once this is done, the user must count the latitude from the north pole, upon the celestial meridianL, down towards the north notch of the horizon, and set the horizon to that latitude. The user then must turn the nutb until the sunY comes to the given day of the year in the ecliptic, and the sun will be at its proper place for that day.
To find the place of the moon'sascending node, and also the place of the moon, anephemeris must be consulted to set them right accordingly. Lastly, the user must turn the winchW, until either the sun comes to the meridianL, or until the meridian comes to the sun (moving the sphere or globe at the user's discretion), and then set the hour-index to the XII, marked noon, the whole sphere will be reset. Then the user must turn the winch, and observe when the sun or moon rises and sets in the horizon. The hour-index will show the times thereof for the given day.[2]
ThroughoutChinese history,astronomers have createdcelestial globes (Chinese:渾象;pinyin:húnxiàng) to assist the observation of the stars. The Chinese also used the armillary sphere in aidingcalendrical computations and calculations.
According toJoseph Needham, the earliest development of the armillary sphere inChina goes back to the astronomersShi Shen andGan De in the 4th century BC, as they were equipped with a primitive single-ring armillary instrument.[3] This would have allowed them to measure the north polar distance (declination) a measurement that gave the position in axiu (right ascension).[3] Needham's 4th century BC dating, however, is rejected by British sinologistChristopher Cullen, who traces the beginnings of these devices to the 1st century BC.[4]
During theWestern Han dynasty (202 BC – 9 AD) additional developments made by the astronomersLuoxia Hong (落下閎), Xiangyu Wangren, and Geng Shouchang (耿壽昌) advanced the use of the armillary in its early stage of evolution. In 52 BC, it was the astronomer Geng Shouchang who introduced the first permanently fixed equatorial ring of the armillary sphere.[3] In the subsequentEastern Han dynasty (23–220 AD) period, the astronomers Fu An and Jia Kui added the ecliptic ring by 84 AD.[3] With the famous statesman, astronomer, and inventorZhang Heng (張衡, 78–139 AD), the sphere was totally complete in 125 AD, with horizon and meridian rings.[3] The world's first water-powered celestial globe was created byZhang Heng, who operated his armillary sphere by use of an inflowclepsydra clock.
Subsequent developments were made after the Han dynasty that improved the use of the armillary sphere. In 323 AD the Chinese astronomer Kong Ting was able to reorganize the arrangement of rings on the armillary sphere so that the ecliptic ring could be pegged on to the equator at any point desired.[3] The Chinese astronomer and mathematicianLi Chunfeng (李淳風) of theTang dynasty created one in 633 AD with three spherical layers to calibrate multiple aspects of astronomical observations, calling them 'nests' (chhung).[3] He was also responsible for proposing a plan of having a sighting tube mounted ecliptically in order for the better observation of celestial latitudes. However, it was the Tang Chinese astronomer, mathematician, and monkYi Xing in the next century who would accomplish this addition to the model of the armillary sphere.[5] Ecliptical mountings of this sort were found on the armillary instruments of Zhou Cong and Shu Yijian in 1050, as well as Shen Kuo's armillary sphere of the later 11th century, but after that point they were no longer employed on Chinese armillary instruments until the arrival of theEuropean Jesuits.
In 723 AD, Yi Xing (一行) and government official Liang Ling-zan (梁令瓚) combined Zhang Heng's water powered celestial globe with anescapement device. With drums hit every quarter-hour and bells rung automatically every full hour, the device was also astriking clock.[6] The famousclock tower that the Chinese polymathSu Song built by 1094 during theSong dynasty would employ Yi Xing's escapement with waterwheel scoops filled by clepsydra drip, and powered a crowning armillary sphere, a central celestial globe, and mechanically operated manikins that would exit mechanically opened doors of the clock tower at specific times to ring bells and gongs to announce the time, or to hold plaques announcing special times of the day. There was also the scientist and statesmanShen Kuo (1031–1095). Being the head official for the Bureau of Astronomy, Shen Kuo was an avid scholar of astronomy, and improved the designs of several astronomical instruments: thegnomon, armillary sphere, clepsydra clock, and sighting tube fixed to observe thepole star indefinitely.[7] When Jamal al-Din of Bukhara was asked to set up an 'Islamic Astronomical Institution' in Khubilai Khan's new capital during theYuan dynasty, he commissioned a number of astronomical instruments, including an armillary sphere. It was noted that "Chinese astronomers had been building [them] since at least 1092".[8]
The armillary sphere was used for observation in India since early times, and finds mention in the works ofĀryabhata (476 CE).[9] TheGoladīpikā—a detailed treatise dealing with globes and the armillary sphere was composed between 1380 and 1460 CE byParameśvara.[9] On the subject of the usage of the armillary sphere in India, Ōhashi (2008) writes: "The Indian armillary sphere (gola-yantra) was based on equatorial coordinates, unlike the Greek armillary sphere, which was based on ecliptical coordinates, although the Indian armillary sphere also had an ecliptical hoop. Probably, the celestial coordinates of the junction stars of the lunar mansions were determined by the armillary sphere since the seventh century or so."[10]
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TheGreek astronomerHipparchus (c. 190 – c. 120 BC) creditedEratosthenes (276 – 194 BC) as the inventor of the armillary sphere.[11][12][13][14][15] Names of this device in Greek includeἀστρολάβοςastrolabos andκρικωτὴ σφαῖραkrikōtē sphaira "ringed sphere".[16] The English name of this device comes ultimately from theLatinarmilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking thepoles and representing theequator, theecliptic,meridians andparallels. Usually a ball representing theEarth or, later, theSun is placed in its center. It is used to demonstrate themotion of thestars around the Earth. Before the advent of the Europeantelescope in the 17th century, the armillary sphere was the prime instrument of all astronomers in determining celestial positions.
In its simplest form, consisting of a ring fixed in the plane of the equator, thearmilla is one of the most ancient of astronomical instruments. Slightly developed, it was crossed by another ring fixed in the plane of the meridian. The first was an equinoctial, the second a solstitial armilla. Shadows were used as indices of the sun's positions, in combinations with angular divisions. When several rings or circles were combined representing the great circles of the heavens, the instrument became an armillary sphere.[1]
Armillary spheres were developed by theHellenistic Greeks and were used as teaching tools already in the 3rd century BC. In larger and more precise forms they were also used as observational instruments. However, the fully developed armillary sphere with nine circles perhaps did not exist until the mid-2nd century AD, during theRoman Empire.[17] Eratosthenes most probably used a solstitial armilla for measuring theobliquity of the ecliptic. Hipparchus probably used an armillary sphere of four rings.[17] TheGreco-Roman geographer and astronomerPtolemy (c. 100 – c. 170 AD) describes his instrument, theastrolabon, in hisAlmagest.[17] It consisted of at least three rings, with a graduated circle inside of which another could slide, carrying two small tubes positioned opposite each other and supported by a vertical plumb-line.[1][17]
Persian and Arab astronomers such asIbrahim al-Fazari andAbbas Ibn Firnas continued to build and improve on armillary spheres. The spherical astrolabe, a variation of both theastrolabe and the armillary sphere, was likely invented during theMiddle Ages in theMiddle East.[18] About 550 AD, Christian philosopherJohn Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant treatise on the instrument.[19] The earliest description of the spherical astrolabe dates back to the Persian astronomerNayrizi (fl. 892–902).Pope Sylvester II applied the use of sighting tubes with his armillary sphere in order to fix the position of thepole star and record measurements for thetropics andequator, and used armillary spheres as a teaching device.[20]
Chinese ideas of astronomy and astronomical instruments were introduced to Korea, where further advancements were also made.Chang Yŏngsil, aKorean inventor, was ordered byKing Sejong the Great of Joseon to build an armillary sphere. The sphere, built in 1433 was named Honcheonui (혼천의,渾天儀).
TheHoncheonsigye, an armillary sphere activated by a working clock mechanism was built by the Korean astronomer Song Iyeong in 1669. It is the only remainingastronomical clock from theJoseon dynasty. The mechanism of the armillary sphere succeeded that of Sejong era's armillary sphere (Honŭi 渾儀, 1435) and celestial sphere (Honsang 渾象, 1435), and the Jade Clepsydra (Ongnu 玉漏, 1438)'s sun-carriage apparatus. Such mechanisms are similar to Ch'oe Yu-ji (崔攸之, 1603~1673)'s armillary sphere(1657). The structure of time going train and the mechanism of striking-release in the part of clock is influenced by the crown escapement which has been developed from 14th century, and is applied to gear system which had been improved until the middle of 17th century in Western-style clockwork. In particular, timing device of Song I-yŏng's Armillary Clock adopts the early 17th century pendulum clock system which could remarkably improve the accuracy of a clock.[21]
Further advances in this instrument were made by Danish astronomerTycho Brahe (1546–1601), who constructed three large armillary spheres which he used for highly precise measurements of the positions of the stars and planets. They were described in hisAstronomiae Instauratae Mechanica.[22]
Armillary spheres were among the first complex mechanical devices. Their development led to many improvements in techniques and design of all mechanical devices.Renaissance scientists and public figures often had their portraits painted showing them with one hand on an armillary sphere, which represented the zenith ofwisdom andknowledge.
The armillary sphere survives as useful for teaching, and may be described as a skeleton celestial globe, the series of rings representing the great circles of the heavens, and revolving on an axis within a horizon. With the earth as center such a sphere is known as Ptolemaic; with the sun as center, as Copernican.[1]
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A representation of an armillary sphere is present in the modernflag of Portugal and has been a national symbol since the reign ofManuel I.
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An artwork-based model of an Armillary sphere has been used since the March 1, 2014 to light theParalympic heritage flame atStoke Mandeville Stadium, United Kingdom. The sphere includes a wheelchair that the user can rotate to spark the flame as part of a ceremony to celebrate the past, present and future of the Paralympic Movement in the UK. The Armillary Sphere was created by artistJon Bausor and will be used for future Heritage Flame events. The flame in the first-ever ceremony was lit byLondon 2012 gold medallistHannah Cockroft.[23]
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The armillary sphere is commonly used inheraldry andvexillology, being mainly known as a symbol associated withPortugal, thePortuguese Empire and thePortuguese discoveries.
In the end of the 15th century, the armillary sphere became the personalheraldic badge of the future KingManuel I of Portugal, when he was still aPrince. The intense use of this badge in documents, monuments, flags and other supports, during the reign of Manuel I, transformed the armillary sphere from a simple personal symbol to a national one that represented the Kingdom of Portugal and in particular itsOverseas Empire. As a national symbol, the armillary sphere continued in use after the death of Manuel I.
In the 17th century, it became associated with thePortuguese dominion of Brazil. In 1815, whenBrazil gained the status of kingdom united with that of Portugal, its coat of arms was formalized as a golden armillary sphere in a blue field. Representing Brazil, the armillary sphere became also present in the arms and the flag of theUnited Kingdom of Portugal, Brazil and the Algarves. WhenBrazil became independent as an empire in 1822, the armillary sphere continued to be present in its national arms and in its national flag. The celestial sphere of the presentFlag of Brazil replaced the armillary sphere in 1889.
The armillary sphere was reintroduced in thenational arms and in the nationalFlag of Portugal in 1911.
One or more of the preceding sentences incorporates text from a publication now in thepublic domain: Huggins, Margaret Lindsay (1911). "Armilla". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. pp. 575–576."There is no evidence for the Hellenistic origin of the spherical astrolabe, but rather evidence so far available suggests that it may have been an early but distinctly Islamic development with no Greek antecedents."
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