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126-740: With the Earth as center, an armillary 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 . Manuel I of Portugal , for example, took it as one of his symbols where it appeared on his standard, and on early Chinese export ceramics made for

252-673: A Korean inventor, was ordered by King Sejong the Great of Joseon to build an armillary sphere. The sphere, built in 1433 was named Honcheonui (혼천의,渾天儀). The Honcheonsigye , an armillary sphere activated by a working clock mechanism was built by the Korean astronomer Song Iyeong in 1669. It is the only remaining astronomical clock from the Joseon 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

378-728: A heliocentric frame is most useful in those cases, galactic and extragalactic astronomy is easier if the Sun is treated as neither stationary nor the center of the universe, but rather rotating around the center of our galaxy, while in turn our galaxy is also not at rest in the cosmic background . Albert Einstein and Leopold Infeld wrote in The Evolution of Physics (1938): "Can we formulate physical laws so that they are valid for all CS [ coordinate systems ], not only those moving uniformly, but also those moving quite arbitrarily, relative to each other? If this can be done, our difficulties will be over. We shall then be able to apply

504-609: A heliocentric model placing all of the then-known planets in their correct order around the Sun. The ancient Greeks believed that the motions of the planets were circular , a view that was not challenged in Western culture until the 17th century, when Johannes Kepler postulated that orbits were heliocentric and elliptical (Kepler's first law of planetary motion ). In 1687, Isaac Newton showed that elliptical orbits could be derived from his laws of gravitation. The astronomical predictions of Ptolemy's geocentric model , developed in

630-418: A transit of Venus for the year 1631. The change from circular orbits to elliptical planetary paths dramatically improved the accuracy of celestial observations and predictions. Because the heliocentric model devised by Copernicus was no more accurate than Ptolemy's system, new observations were needed to persuade those who still adhered to the geocentric model. However, Kepler's laws based on Brahe's data became

756-464: A 2006 survey that show currently some 20% of the U.S. population believe that the Sun goes around the Earth (geocentricism) rather than the Earth goes around the Sun (heliocentricism), while a further 9% claimed not to know. Polls conducted by Gallup in the 1990s found that 16% of Germans, 18% of Americans and 19% of Britons hold that the Sun revolves around the Earth. A study conducted in 2005 by Jon D. Miller of Northwestern University , an expert in

882-486: A Ptolemaic cosmology, the Venus epicycle can be neither completely inside nor completely outside of the orbit of the Sun. As a result, Ptolemaics abandoned the idea that the epicycle of Venus was completely inside the Sun, and later 17th-century competition between astronomical cosmologies focused on variations of Tycho Brahe 's Tychonic system (in which the Earth was still at the center of the universe, and around it revolved

1008-565: A ball representing the Earth or, later, the Sun is placed in its center. It is used to demonstrate the motion of the stars around the Earth. Before the advent of the European telescope 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, the armilla

1134-399: A belief held by some of his contemporaries "that the motion we see is due to the Earth's movement and not to that of the sky." The prevalence of this view is further confirmed by a reference from the 13th century which states: According to the geometers [or engineers] ( muhandisīn ), the Earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to

1260-409: A breakthrough in scientific thought, using the newly developed mathematical discipline of differential calculus , finally replacing the previous schools of scientific thought, which had been dominated by Aristotle and Ptolemy. However, the process was gradual. Several empirical tests of Newton's theory, explaining the longer period of oscillation of a pendulum at the equator and the differing size of

1386-488: A center of the Solar System with equal validity. Relativity agrees with Newtonian predictions that regardless of whether the Sun or the Earth are chosen arbitrarily as the center of the coordinate system describing the Solar System, the paths of the planets form (roughly) ellipses with respect to the Sun, not the Earth. With respect to the average reference frame of the fixed stars , the planets do indeed move around

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1512-453: 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 statesman Shen Kuo (1031–1095). Being the head official for the Bureau of Astronomy, Shen Kuo

1638-625: A cycle in approximately 18.6 years. The image of the ascending and descending orbital nodes as the head and tail of a dragon, 180 degrees apart in the sky, goes back to the Chaldeans; it was used by the Zoroastrians, and then by Arabic astronomers and astrologers. In Middle Persian, its head and tail were respectively called gōzihr sar and gōzihr dumb ; in Arabic, al-ra's al-jawzihr and al-dhanab al-jawzihr — or in

1764-461: A degree of latitude, would gradually become available between 1673 and 1738. In addition, stellar aberration was observed by Robert Hooke in 1674, and tested in a series of observations by Jean Picard over a period of ten years, finishing in 1680. However, it was not explained until 1729, when James Bradley provided an approximate explanation in terms of the Earth's revolution about the Sun. In 1838, astronomer Friedrich Wilhelm Bessel measured

1890-481: A different element by heat or moisture. Atmospheric explanations for many phenomena were preferred because the Eudoxan–Aristotelian model based on perfectly concentric spheres was not intended to explain changes in the brightness of the planets due to a change in distance. Eventually, perfectly concentric spheres were abandoned as it was impossible to develop a sufficiently accurate model under that ideal, with

2016-533: A line running from the Earth through the Sun, such as placing the center of the Venus epicycle near the Sun. In this case, if the Sun is the source of all the light, under the Ptolemaic system: If Venus is between Earth and the Sun, the phase of Venus must always be crescent or all dark. If Venus is beyond the Sun, the phase of Venus must always be gibbous or full. But Galileo saw Venus at first small and full, and later large and crescent. This showed that with

2142-400: A long time the geocentric postulate produced more accurate results. Additionally some felt that 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 Earth shaped like a section of

2268-450: A new model was required. The Ptolemaic order of spheres from Earth outward is: Ptolemy did not invent or work out this order, which aligns with the ancient Seven Heavens religious cosmology common to the major Eurasian religious traditions. It also follows the decreasing orbital periods of the Moon, Sun, planets and stars. Muslim astronomers generally accepted the Ptolemaic system and

2394-450: A pillar (a cylinder), held aloft at the center of everything. The Sun, Moon, and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; he believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from

2520-433: A problem which geocentrists could not easily overcome. In 1687, Isaac Newton stated the law of universal gravitation , described earlier as a hypothesis by Robert Hooke and others. His main achievement was to mathematically derive Kepler's laws of planetary motion from the law of gravitation, thus helping to prove the latter. This introduced gravitation as the force which both kept the Earth and planets moving through

2646-403: A real relativistic physics valid in all CS; a physics in which there would be no place for absolute, but only for relative, motion? This is indeed possible!" Despite giving more respectability to the geocentric view than Newtonian physics does, relativity is not geocentric. Rather, relativity states that the Sun, the Earth, the Moon, Jupiter, or any other point for that matter could be chosen as

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2772-454: 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. A representation of an armillary sphere is present in the modern flag of Portugal and has been a national symbol since the reign of Manuel I . An artwork-based model of an Armillary sphere has been used since

2898-587: A vertical plumb-line. Persian and Arab astronomers such as Ibrahim al-Fazari and Abbas Ibn Firnas continued to build and improve on armillary spheres. The spherical astrolabe, a variation of both the astrolabe and the armillary sphere, was likely invented during the Middle Ages in the Middle East . About 550 AD, Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which

3024-483: Is contrary to these Scriptures of ours, that is to Catholic faith, we must either prove it as well as we can to be entirely false, or at all events we must, without the smallest hesitation, believe it to be so." To understand how just is the rule here formulated we must remember, first, that the sacred writers, or to speak more accurately, the Holy Ghost "Who spoke by them, did not intend to teach men these things (that

3150-432: Is due to any loss of light caused by its phases being compensated for by an increase in apparent size caused by its varying distance from Earth.) Objectors to heliocentrism noted that terrestrial bodies naturally tend to come to rest as near as possible to the center of the Earth. Further, barring the opportunity to fall closer the center, terrestrial bodies tend not to move unless forced by an outside object, or transformed to

3276-470: 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. Armillary spheres were developed by

3402-407: Is so high because several spheres are needed for each planet.) 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 an incorruptible substance called aether . Aristotle believed that the Moon was in the innermost sphere and therefore touches the realm of Earth, causing the dark spots ( maculae ) and

3528-600: Is the earliest extant treatise on the instrument. The earliest description of the spherical astrolabe dates back to the Persian astronomer Nayrizi ( fl. 892–902). Pope Sylvester II applied the use of sighting tubes with his armillary sphere in order to fix the position of the pole star and record measurements for the tropics and equator , and used armillary spheres as a teaching device. Chinese ideas of astronomy and astronomical instruments were introduced to Korea, where further advancements were also made. Jang Yeong-sil ,

3654-471: Is to say, the essential nature of the things of the visible universe), things in no way profitable unto salvation." Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science. Ordinary speech primarily and properly describes what comes under

3780-552: Is turned around its axis. The globe assembly is supported on a pedestal N , and may be elevated or depressed upon the joint O , to any number of degrees from 0 to 90 by means of the arc P , which is fixed in the strong brass arm Q . The globe assembly slides in the upright piece R , in which is a screw at r , to fix it at any proper elevation. In the box T are two wheels (as in Dr Long's sphere) and two pinions, whose axes come out at V and U ; either of which may be turned by

3906-527: The Hellenistic 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 the Roman Empire . Eratosthenes most probably used a solstitial armilla for measuring the obliquity of

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4032-537: The Islamic Golden Age . Two observations supported the idea that Earth was the center of the Universe. First, from anywhere on Earth, the Sun appears to revolve around Earth once per day . While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through

4158-519: The Portuguese dominion of Brazil . In 1815, when Brazil 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 the United Kingdom of Portugal, Brazil and the Algarves . When Brazil became independent as an empire in 1822,

4284-681: The Qur'anic verse, "All praise belongs to God, Lord of the Worlds," emphasizing the term "Worlds." The "Maragha Revolution" refers to the Maragha school's revolution against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the Maragha observatory and continuing with astronomers from the Damascus mosque and Samarkand observatory . Like their Andalusian predecessors,

4410-598: The United States between 1870 and 1920, for example, various members of the Lutheran Church–Missouri Synod published articles disparaging Copernican astronomy and promoting geocentrism. However, in the 1902 Theological Quarterly , A. L. Graebner observed that the synod had no doctrinal position on geocentrism, heliocentrism, or any scientific model, unless it were to contradict Scripture. He stated that any possible declarations of geocentrists within

4536-408: The aether of the higher spheres. Galileo could also see the moons of Jupiter, which he dedicated to Cosimo II de' Medici , and stated that they orbited around Jupiter, not Earth. This was a significant claim as it would mean not only that not everything revolved around Earth as stated in the Ptolemaic model, but also showed a secondary celestial body could orbit a moving celestial body, strengthening

4662-721: The geocentric model (also known as geocentrism , often exemplified specifically by the Ptolemaic system ) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun , Moon , stars , and planets all orbit Earth. The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt, as well as during

4788-482: The geocentric model . Ptolemy argued that the Earth was a sphere in the center of the universe, from the simple observation that half the stars were above the horizon and half were below the horizon at any time (stars on rotating stellar sphere), and the assumption that the stars were all at some modest distance from the center of the universe. If the Earth were substantially displaced from the center, this division into visible and invisible stars would not be equal. In

4914-484: The geographic poles of Earth. Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary. Ancient Greek , ancient Roman , and medieval philosophers usually combined the geocentric model with a spherical Earth , in contrast to the older flat-Earth model implied in some mythology . However, the Greek astronomer and mathematician Aristarchus of Samos ( c.  310  – c.  230 BC ) developed

5040-471: The parallax of the star 61 Cygni successfully, and disproved Ptolemy's claim that parallax motion did not exist. This finally confirmed the assumptions made by Copernicus, providing accurate, dependable scientific observations, and conclusively displaying how distant stars are from Earth. A geocentric frame is useful for many everyday activities and most laboratory experiments, but is a less appropriate choice for Solar System mechanics and space travel. While

5166-454: The 2nd century AD, finally standardised geocentrism. His main astronomical work, the Almagest , was the culmination of centuries of work by Hellenic , Hellenistic and Babylonian astronomers. For over a millennium, European and Islamic astronomers assumed it was the correct cosmological model. Because of its influence, people sometimes wrongly think the Ptolemaic system is identical with

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5292-431: The 2nd century CE, served as the basis for preparing astrological and astronomical charts for over 1,500 years. The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473–1543), Galileo (1564–1642), and Kepler (1571–1630). There was much resistance to the transition between these two theories, since for

5418-410: The 4th century BC onwards 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. The stars and planets were carried around the Earth on spheres or circles , arranged in

5544-540: The Earth about its axis. For example, in Joshua 10:12 , the Sun and Moon are said to stop in the sky, and in Psalms the world is described as immobile. Psalms 93:1 says in part, "the world is established, firm and secure". Contemporary advocates for such religious beliefs include Robert Sungenis (author of the 2006 book Galileo Was Wrong and the 2014 pseudo-documentary film The Principle ). These people subscribe to

5670-451: The Earth at different points in its orbit, and explained the observation that planets slowed down, stopped, and moved backward in retrograde motion , and then again reversed to resume normal, or prograde, motion. The deferent-and-epicycle model had been used by Greek astronomers for centuries along with the idea of the eccentric (a deferent whose center is slightly away from the Earth), which

5796-409: The Earth away from the center of rotation of the rest of the universe. Another sphere, the epicycle, is embedded inside the deferent sphere and is represented by the smaller dotted line to the right. A given planet then moves around the epicycle at the same time the epicycle moves along the path marked by the deferent. These combined movements cause the given planet to move closer to and further away from

5922-404: The Earth's radius away from the centre of the Earth (thus closer to the surface than the center). What the principle of relativity points out is that correct mathematical calculations can be made regardless of the reference frame chosen, and these will all agree with each other as to the predictions of actual motions of bodies with respect to each other. It is not necessary to choose the object in

6048-506: The Earth. By using an equant, Ptolemy claimed to keep motion which was uniform and circular, although it departed from the Platonic ideal of uniform circular motion . The resultant system, which eventually came to be widely accepted in the west, seems unwieldy to modern astronomers; each planet required an epicycle revolving on a deferent, offset by an equant which was different for each planet. It predicted various celestial motions, including

6174-633: 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

6300-440: The Maragha astronomers attempted to solve the equant problem (the circle around whose circumference a planet or the center of an epicycle was conceived to move uniformly) and produce alternative configurations to the Ptolemaic model without abandoning geocentrism. They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than

6426-465: The Maragha school never made the paradigm shift to heliocentrism. The influence of the Maragha school on Copernicus remains speculative, since there is no documentary evidence to prove it. The possibility that Copernicus independently developed the Tusi couple remains open, since no researcher has yet demonstrated that he knew about Tusi's work or that of the Maragha school. Not all Greeks agreed with

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6552-636: The March 1, 2014 to light the Paralympic heritage flame at Stoke 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 artist Jon Bausor and will be used for future Heritage Flame events. The flame in

6678-480: The Moon in the ecliptic plane were called the "dragon's head" ( Latin : caput draconis , Arabic : رأس الجوزهر ) and "dragon's tail" ( Latin : cauda draconis ), respectively. These terms originally referred to the times when the Moon crossed the apparent path of the sun in the sky (as in a solar eclipse ). Also, corruptions of the Arabic term such as ganzaar , genzahar , geuzaar and zeuzahar were used in

6804-463: The Portuguese court. In the flag of the Empire of Brazil , the armillary sphere is also featured. The Beijing Capital International Airport Terminal 3 features a large armillary sphere metal sculpture as an exhibit of Chinese inventions for international and domestic visitors. The exterior parts of this machine are a compages [or framework] of brass rings, which represent the principal circles of

6930-483: The Ptolemaic model in numerically predicting planetary positions, and were in better agreement with empirical observations. The most important of the Maragha astronomers included Mo'ayyeduddin Urdi (died 1266), Nasīr al-Dīn al-Tūsī (1201–1274), Qutb al-Din al-Shirazi (1236–1311), Ibn al-Shatir (1304–1375), Ali Qushji ( c.  1474 ), Al-Birjandi (died 1525), and Shams al-Din al-Khafri (died 1550). However,

7056-442: The Ptolemaic system, each planet is moved by a system of two spheres: one called its deferent; the other, its epicycle . The deferent is a circle whose center point, called the eccentric and marked in the diagram with an X, is distant from the Earth. The original purpose of the eccentric was to account for the difference in length of the seasons (northern autumn was about five days shorter than spring during this time period) by placing

7182-422: The Solar System with the largest gravitational field as the center of the coordinate system in order to predict the motions of planetary bodies, though doing so may make calculations easier to perform or interpret. A geocentric coordinate system can be more convenient when dealing only with bodies mostly influenced by the gravity of the Earth (such as artificial satellites and the Moon ), or when calculating what

7308-407: The Solar System, the ascending node is the node where the orbiting secondary passes away from the observer, and the descending node is the node where it moves towards the observer. The position of the node may be used as one of a set of parameters, called orbital elements , which describe the orbit. This is done by specifying the longitude of the ascending node (or, sometimes, the longitude of

7434-463: The Sun) is very noticeable even with low eccentricities as possessed by the planets. To summarize, Ptolemy conceived a system that was compatible with Aristotelian philosophy and succeeded in tracking actual observations and predicting future movement mostly to within the limits of the next 1000 years of observations. The observed motions and his mechanisms for explaining them include: The geocentric model

7560-468: The Sun, but all other planets revolved around the Sun in one massive set of epicycles), or variations on the Copernican system. Johannes Kepler analysed Tycho Brahe 's famously accurate observations and afterwards constructed his three laws in 1609 and 1619, based on a heliocentric view where the planets move in elliptical paths. Using these laws, he was the first astronomer to successfully predict

7686-438: The Sun, which due to its much larger mass, moves far less than its own diameter and the gravity of which is dominant in determining the orbits of the planets (in other words, the center of mass of the Solar System is near the center of the Sun). The Earth and Moon are much closer to being a binary planet ; the center of mass around which they both rotate is still inside the Earth, but is about 4,624 km (2,873 miles) or 72.6% of

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7812-402: The ability to go through lunar phases . 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, thus water formed a layer surrounding the sphere of Earth. The tendency of air and fire, on the other hand,

7938-403: 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: 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

8064-479: The ancient Greek idea of uniform circular motions by hypothesizing that the planet Mercury moves in an elliptic orbit , while Alpetragius proposed a planetary model that abandoned the equant , epicycle and eccentric mechanisms, though this resulted in a system that was mathematically less accurate. His alternative system spread through most of Europe during the 13th century. Fakhr al-Din al-Razi (1149–1209), in dealing with his conception of physics and

8190-620: The armillary sphere continued to be present in its national arms and in its national flag. The celestial sphere of the present Flag of Brazil replaced the armillary sphere in 1889. The armillary sphere was reintroduced in the national arms and in the national Flag of Portugal in 1911. "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." Geocentric model In astronomy ,

8316-481: The armillary sphere so that the ecliptic ring could be pegged on to the equator at any point desired. The Chinese astronomer and mathematician Li Chunfeng (李淳風) of the Tang dynasty created one in 633 AD with three spherical layers to calibrate multiple aspects of astronomical observations, calling them 'nests' (chhung). He was also responsible for proposing a plan of having a sighting tube mounted ecliptically in order for

8442-677: The arrival of the European 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 an escapement device. With drums hit every quarter-hour and bells rung automatically every full hour, the device was also a striking clock . The famous clock tower that the Chinese polymath Su Song built by 1094 during the Song dynasty would employ Yi Xing's escapement with waterwheel scoops filled by clepsydra drip, and powered

8568-409: The beginning and end of retrograde motion, to within a maximum error of 10 degrees, considerably better than without the equant. The model with epicycles is in fact a very good model of an elliptical orbit with low eccentricity. The well-known ellipse shape does not appear to a noticeable extent when the eccentricity is less than 5%, but the offset distance of the "center" (in fact the focus occupied by

8694-545: The better observation of celestial latitudes. However, it was the Tang Chinese astronomer, mathematician, and monk Yi Xing in the next century who would accomplish this addition to the model of the armillary sphere. 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

8820-433: The center of the universe, while the Earth and other planets revolved around it. His theory was not popular, and he had one named follower, Seleucus of Seleucia . Epicurus was the most radical. He correctly realized in the 4th century BC that the universe does not have any single center. This theory was widely accepted by the later Epicureans and was notably defended by Lucretius in his poem De rerum natura . In 1543,

8946-426: The early 17th century pendulum clock system which could remarkably improve the accuracy of a clock. Further advances in this instrument were made by Danish astronomer Tycho 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 his Astronomiae Instauratae Mechanica . Armillary spheres were among

9072-425: The ecliptic at an angle of 5 1 ⁄ 3 degrees, to opposite points called the lunar 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 globe I , fixed on an axis K , which extends from the north and south poles of the globe at n and s , to those of the celestial sphere at N and S . On this axis

9198-410: The ecliptic. Hipparchus probably used an armillary sphere of four rings. The Greco-Roman geographer and astronomer Ptolemy ( c.  100  – c.  170 AD ) describes his instrument, the astrolabon , in his Almagest . 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

9324-481: The equants instead of the epicycles because the former was easier to calculate, and gave the same result. It has been determined that the Copernican, Ptolemaic and even the Tychonic models provide identical results to identical inputs: they are computationally equivalent. It was not until Kepler demonstrated a physical observation that could show that the physical Sun is directly involved in determining an orbit that

9450-399: 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 of wisdom and knowledge . The armillary sphere survives as useful for teaching, and may be described as

9576-482: The first-ever ceremony was lit by London 2012 gold medallist Hannah Cockroft . The armillary sphere is commonly used in heraldry and vexillology , being mainly known as a symbol associated with Portugal , the Portuguese Empire and the Portuguese discoveries . In the end of the 15th century, the armillary sphere became the personal heraldic badge of the future King Manuel I of Portugal , when he

9702-501: The fixed stars due to stellar parallax . Thus if the Earth was moving, the shapes of the constellations should change considerably over the course of a year. As they did not appear to move, either the stars are much farther away than the Sun and the planets than previously conceived, making their motion undetectable, or the Earth is not moving at all. Because the stars are actually much further away than Greek astronomers postulated (making angular movement extremely small), stellar parallax

9828-411: The flat celestial meridian L 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 horizon M , so as to turn upon the two strong wires proceeding from its east and west points to

9954-413: The following: If a reference direction from one side of the plane of reference to the other is defined, the two nodes can be distinguished. For geocentric and heliocentric orbits, the ascending node (or north node ) is where the orbiting object moves north through the plane of reference, and the descending node (or south node ) is where it moves south through the plane. In the case of objects outside

10080-448: The geocentric model, but by the 10th century texts appeared regularly whose subject matter was doubts concerning Ptolemy ( shukūk ). Several Muslim scholars questioned the Earth's apparent immobility and centrality within the universe. Some Muslim astronomers believed that the Earth rotates around its axis , such as Abu Sa'id al-Sijzi (d. circa 1020). According to al-Biruni , Sijzi invented an astrolabe called al-zūraqī based on

10206-423: The geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus , two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It

10332-529: The geocentric system met its first serious challenge with the publication of Copernicus ' De revolutionibus orbium coelestium ( On the Revolutions of the Heavenly Spheres ), which posited that the Earth and the other planets instead revolved around the Sun. The geocentric system was still held for many years afterwards, as at the time the Copernican system did not offer better predictions than

10458-472: The geocentric system, and it posed problems for both natural philosophy and scripture. The Copernican system was no more accurate than Ptolemy's system, because it still used circular orbits. This was not altered until Johannes Kepler postulated that they were elliptical (Kepler's first law of planetary motion ). With the invention of the telescope in 1609, observations made by Galileo Galilei (such as that Jupiter has moons) called into question some of

10584-409: The given degree of latitude for any place lies at the side of the stem R ; 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 meridian L , down towards the north notch of

10710-422: 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 meridian L . The horizon is divided into 360 degrees all around its outermost edge, within which are the points of the compass , for showing

10836-438: The heavens: In the north pole of the ecliptic is a nut b , to which is fixed one end of the quadrantal wire. To the other end is a small sun Y , which is carried around the ecliptic B — B , by turning the nut. In the south pole of the ecliptic is a pin d , on which another quadrantal wire is situated, with a small moon Ζ upon it, which may be moved around by hand. A mechanism causes the moon to move in an orbit which crosses

10962-427: The heliocentric argument that a moving Earth could retain the Moon. Galileo's observations were verified by other astronomers of the time period who quickly adopted use of the telescope, including Christoph Scheiner , Johannes Kepler , and Giovan Paulo Lembo. In December 1610, Galileo Galilei used his telescope to observe that Venus showed all phases , just like the Moon . He thought that while this observation

11088-413: The horizon, and set the horizon to that latitude. The user then must turn the nut b until the sun Y 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's ascending node , and also the place of the moon, an ephemeris must be consulted to set them right accordingly. Lastly, the user must turn the winch W , until either

11214-411: 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 screw r in the upright stem R , and taking hold of the arm Q , move it up or down until

11340-467: The inventor of the armillary sphere. Names of this device in Greek include ἀστρολάβος astrolabos and κρικωτὴ σφαῖρα krikōtē sphaira "ringed sphere". The English name of this device comes ultimately from the Latin armilla (circle, bracelet), since it has a skeleton made of graduated metal circles linking the poles and representing the equator , the ecliptic , meridians and parallels . Usually

11466-405: The laws of nature to any CS. The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS could be used with equal justification. The two sentences, 'the sun is at rest and the Earth moves', or 'the sun moves and the Earth is at rest', would simply mean two different conventions concerning two different CS. Could we build

11592-479: The mathematical methods then available. However, while providing for similar explanations, the later deferent and epicycle model was already flexible enough to accommodate observations. Although the basic tenets of Greek geocentrism were established by the time of Aristotle, the details of his system did not become standard. The Ptolemaic system, developed by the Hellenistic astronomer Claudius Ptolemaeus in

11718-523: The medieval West to denote either of the nodes. The Koine Greek terms αναβιβάζων and καταβιβάζων were also used for the ascending and descending nodes, giving rise to the English terms anabibazon and catabibazon . For the orbit of the Moon around Earth , the plane is taken to be the ecliptic , not the equatorial plane . The gravitational pull of the Sun upon the Moon causes its nodes to gradually precess westward, completing

11844-415: The motion of the Earth and not the stars. Early in the 11th century Alhazen wrote a scathing critique of Ptolemy 's model in his Doubts on Ptolemy ( c.  1028 ), which some have interpreted to imply he was criticizing Ptolemy's geocentrism, but most agree that he was actually criticizing the details of Ptolemy's model rather than his geocentrism. In the 12th century, Arzachel departed from

11970-416: The node .) The line of nodes is the straight line resulting from the intersection of the object's orbital plane with the plane of reference; it passes through the two nodes. The symbol of the ascending node is [REDACTED] ( Unicode : U+260A, ☊), and the symbol of the descending node is [REDACTED] ( Unicode : U+260B, ☋). In medieval and early modern times, the ascending and descending nodes of

12096-515: The north polar distance (declination) a measurement that gave the position in a xiu (right ascension). Needham's 4th century BC dating, however, is rejected by British sinologist Christopher Cullen , who traces the beginnings of these devices to the 1st century BC. During the Western Han dynasty (202 BC – 9 AD) additional developments made by the astronomers Luoxia Hong (落下閎), Xiangyu Wangren, and Geng Shouchang (耿壽昌) advanced

12222-460: The observation of the stars. The Chinese also used the armillary sphere in aiding calendrical computations and calculations. According to Joseph Needham , the earliest development of the armillary sphere in China goes back to the astronomers Shi Shen and Gan De in the 4th century BC, as they were equipped with a primitive single-ring armillary instrument. This would have allowed them to measure

12348-492: The one advanced by Galileo in the " Letter to the Grand Duchess Christina ". Pope Pius XII (1939–1958) repeated his predecessor's teaching: Ascending node An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit , which is contained in the reference plane, has no nodes. Common planes of reference include

12474-588: The order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere. In his " Myth of Er ", a section of the Republic , Plato describes the cosmos as the Spindle of Necessity , attended by the Sirens and turned by the three Fates . Eudoxus of Cnidus , who worked with Plato, developed a less mythical, more mathematical explanation of

12600-474: The physical world in his Matalib , rejects the Aristotelian and Avicennian notion of the Earth's centrality within the universe, but instead argues that there are "a thousand thousand worlds ( alfa alfi 'awalim ) beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has." To support his theological argument , he cites

12726-418: The planets' motion based on Plato's dictum stating that all phenomena in the heavens can be explained with uniform circular motion. Aristotle elaborated on Eudoxus' system. In the fully developed Aristotelian system, the spherical Earth is at the center of the universe, and all other heavenly bodies are attached to 47–55 transparent, rotating spheres surrounding the Earth, all concentric with it. (The number

12852-409: The public understanding of science and technology, found that about 20%, or one in five, of American adults believe that the Sun orbits the Earth. According to 2011 VTSIOM poll, 32% of Russians believe that the Sun orbits the Earth. The famous Galileo affair pitted the geocentric model against the claims of Galileo . In regards to the theological basis for such an argument, two Popes addressed

12978-559: The question of whether the use of phenomenological language would compel one to admit an error in Scripture. Both taught that it would not. Pope Leo XIII (1878–1903) wrote: we have to contend against those who, making an evil use of physical science, minutely scrutinize the Sacred Book in order to detect the writers in a mistake, and to take occasion to vilify its contents. ... There can never, indeed, be any real discrepancy between

13104-548: The senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us – "went by what sensibly appeared", or put down what God, speaking to men, signified, in the way men could understand and were accustomed to. Maurice Finocchiaro, author of a book on the Galileo affair, notes that this is "a view of the relationship between biblical interpretation and scientific investigation that corresponds to

13230-474: The size of a planet's retrograde loop (especially that of Mars) would be smaller, or sometimes larger, than expected, resulting in positional errors of as much as 30 degrees. To alleviate the problem, Ptolemy developed the equant . The equant was a point near the center of a planet's orbit where, if you were to stand there and watch, the center of the planet's epicycle would always appear to move at uniform speed; all other locations would see non-uniform speed, as on

13356-451: The sky will look like when viewed from Earth (as opposed to an imaginary observer looking down on the entire Solar System, where a different coordinate system might be more convenient). The Ptolemaic model held sway into the early modern age ; from the late 16th century onward it was gradually replaced as the consensus description by the heliocentric model . Geocentrism as a separate religious belief, however, never completely died out. In

13482-411: The small winch W . When the winch is put upon the axis V , and turn 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 sun Y , and moon Z , round the same way, and causing them to rise above and set below the horizon. But when the winch is put upon the axis U , and turned forward,

13608-418: 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,

13734-533: The sun comes to the meridian L , 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 set sin the horizon. The hour-index will show the times thereof for the given day. Throughout Chinese history, astronomers have created celestial globes ( Chinese : 渾象 ) to assist

13860-457: The synod did not set the position of the church body as a whole. Articles arguing that geocentrism was the biblical perspective appeared in some early creation science newsletters pointing to some passages in the Bible , which, when taken literally, indicate that the daily apparent motions of the Sun and the Moon are due to their actual motions around the Earth rather than due to the rotation of

13986-422: The tenets of geocentrism but did not seriously threaten it. Because he observed dark "spots" on the Moon, craters, he remarked that the moon was not a perfect celestial body as had been previously conceived. This was the first detailed observation by telescope of the Moon's imperfections, which had previously been explained by Aristotle as the Moon being contaminated by Earth and its heavier elements, in contrast to

14112-505: The theologian and the physicist, as long as each confines himself within his own lines, and both are careful, as St. Augustine warns us, "not to make rash assertions, or to assert what is not known as known". If dissension should arise between them, here is the rule also laid down by St. Augustine, for the theologian: "Whatever they can really demonstrate to be true of physical nature, we must show to be capable of reconciliation with our Scriptures; and whatever they assert in their treatises which

14238-439: The universe and also kept the atmosphere from flying away. The theory of gravity allowed scientists to rapidly construct a plausible heliocentric model for the Solar System. In his Principia , Newton explained his theory of how gravity, previously thought to be a mysterious, unexplained occult force, directed the movements of celestial bodies, and kept our Solar System in working order. His descriptions of centripetal force were

14364-409: 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. In the subsequent Eastern Han dynasty (23–220 AD) period, the astronomers Fu An and Jia Kui added the ecliptic ring by 84 AD. With the famous statesman, astronomer, and inventor Zhang Heng (張衡, 78–139 AD), the sphere

14490-538: The view that a plain reading of the Bible contains an accurate account of the manner in which the universe was created and requires a geocentric worldview. Most contemporary creationist organizations reject such perspectives. According to a report released in 2014 by the National Science Foundation , 26% of Americans surveyed believe that the Sun revolves around the Earth. Morris Berman quotes

14616-555: Was an avid scholar of astronomy, and improved the designs of several astronomical instruments: the gnomon , armillary sphere, clepsydra clock, and sighting tube fixed to observe the pole star indefinitely. When Jamal al-Din of Bukhara was asked to set up an 'Islamic Astronomical Institution' in Khubilai Khan's new capital during the Yuan dynasty , he commissioned a number of astronomical instruments, including an armillary sphere. It

14742-528: 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." The Greek astronomer Hipparchus ( c.  190  – c.  120 BC ) credited Eratosthenes (276 – 194 BC) as

14868-522: Was even older. In the illustration, the center of the deferent is not the Earth but the spot marked X, making it eccentric (from the Greek ἐκ ec- meaning "from" and κέντρον kentron meaning "center"), from which the spot takes its name. Unfortunately, the system that was available in Ptolemy's time did not quite match observations , even though it was an improvement over Hipparchus' system. Most noticeably

14994-451: Was eventually replaced by the heliocentric model . Copernican heliocentrism could remove Ptolemy's epicycles because the retrograde motion could be seen to be the result of the combination of the movements and speeds of Earth and planets. Copernicus felt strongly that equants were a violation of Aristotelian purity, and proved that replacement of the equant with a pair of new epicycles was entirely equivalent. Astronomers often continued using

15120-435: Was incompatible with the Ptolemaic system, it was a natural consequence of the heliocentric system. However, Ptolemy placed Venus' deferent and epicycle entirely inside the sphere of the Sun (between the Sun and Mercury), but this was arbitrary; he could just as easily have swapped Venus and Mercury and put them on the other side of the Sun, or made any other arrangement of Venus and Mercury, as long as they were always near

15246-458: Was not detected until the 19th century . Therefore, the Greeks chose the simpler of the two explanations. Another observation used in favor of the geocentric model at the time was the apparent consistency of Venus' luminosity, which implies that it is usually about the same distance from Earth, which in turn is more consistent with geocentrism than heliocentrism. (In fact, Venus' luminous consistency

15372-533: Was noted that "Chinese astronomers had been building [them] since at least 1092". The armillary sphere was used for observation in India since early times, and finds mention in the works of Āryabhata (476 CE). The Goladīpikā —a detailed treatise dealing with globes and the armillary sphere was composed between 1380 and 1460 CE by Parameśvara . On the subject of the usage of the armillary sphere in India, Ōhashi (2008) writes: "The Indian armillary sphere ( gola-yantra )

15498-401: Was revived in the Middle Ages by Jean Buridan . Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but it is now known that he did not. Martianus Capella definitely put Mercury and Venus in orbit around the Sun. Aristarchus of Samos wrote a work, which has not survived, on heliocentrism , saying that the Sun was at

15624-488: Was still a Prince . 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 its Overseas 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

15750-403: Was to move upwards, away from the center, with fire being lighter than air. Beyond the layer of fire, were the solid spheres of aether in which the celestial bodies were embedded. They were also entirely composed of aether. Adherence to the geocentric model stemmed largely from several important observations. First of all, if the Earth did move, then one ought to be able to observe the shifting of

15876-462: Was totally complete in 125 AD, with horizon and meridian rings. The world's first water-powered celestial globe was created by Zhang Heng , who operated his armillary sphere by use of an inflow clepsydra 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

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