The first armillary sphere was not a smooth globe but a skeletal framework of brass rings, a mechanical skeleton designed to map the invisible architecture of the sky. This device, known as an armillary sphere, consists of a spherical framework of rings centered on Earth or the Sun that represent lines of celestial longitude and latitude. Unlike a celestial globe which is a solid sphere used to map constellations, the armillary sphere uses open rings to demonstrate the motion of stars and planets. The exterior parts of this machine are a compages or framework of brass rings that represent the principal circles of the heavens. These include the equinoctial ring divided into 360 degrees to show the sun's right ascension, and the ecliptic ring divided into 12 signs to track the sun's position throughout the year. The instrument also features the tropic of Cancer and the tropic of Capricorn, each circle 23 degrees from the equinoctial circle, as well as the Arctic and Antarctic circles. A mechanism within the sphere allows a small sun and moon to be moved around the ecliptic, with the moon's orbit crossing the ecliptic at an angle of 5 degrees to opposite points called the lunar nodes. This intricate construction allowed astronomers to demonstrate either the real motion of the earth or the apparent motion of the heavens, depending on which part of the machine was turned by hand.
Ancient Chinese Innovations
The earliest development of the armillary sphere in China goes back to the astronomers Shi Shen and Gan De in the 4th century BC, who were equipped with a primitive single-ring armillary instrument. This device allowed them to measure the north polar distance, a measurement that gave the position in a xiu or right ascension. During the Western Han dynasty, additional developments were made by the astronomers Luoxia Hong, Xiangyu Wangren, and Geng Shouchang. 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 period, the astronomers Fu An and Jia Kui added the ecliptic ring by 84 AD. With the famous statesman, astronomer, and inventor Zhang Heng, the sphere 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 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 of the Tang dynasty created one in 633 AD with three spherical layers to calibrate multiple aspects of astronomical observations, calling them nests. It was the Tang Chinese astronomer, mathematician, and monk Yi Xing in the next century who would accomplish the addition of an ecliptical mounting to the model of the armillary sphere. In 723 AD, Yi Xing and government official Liang Ling-zan 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 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.
The Greek astronomer Hipparchus credited Eratosthenes as the inventor of the armillary sphere, with names of this device in Greek including astrolabos and krikōtē sphaira. The English name of this device comes ultimately from the Latin armilla, meaning circle or bracelet, since it has a skeleton made of graduated metal circles linking the poles and representing the equator, the ecliptic, meridians and parallels. Usually 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 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 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 the ecliptic. Hipparchus probably used an armillary sphere of four rings. The Greco-Roman geographer and astronomer Ptolemy 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 a vertical plumb-line.
Islamic and Medieval Expansions
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 is the earliest extant treatise on the instrument. The earliest description of the spherical astrolabe dates back to the Persian astronomer Nayrizi. 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. In the Indian Subcontinent, the armillary sphere was used for observation in India since early times, and finds mention in the works of Aryabhata. The Goladipika, a detailed treatise dealing with globes and the armillary sphere, was composed between 1380 and 1460 CE by Parameśvara. The Indian armillary sphere 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. 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 was noted that Chinese astronomers had been building them since at least 1092.
Korean and Renaissance Mastery
Chinese ideas of astronomy and astronomical instruments were introduced to Korea, where further advancements were also made. Chang Yongsil, 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. 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 and celestial sphere, and the Jade Clepsydra's sun-carriage apparatus. Such mechanisms are similar to Choe Yu-ji's armillary sphere. 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-yong's Armillary Clock adopts 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, 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 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.
Symbols of Empire and Nation
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. 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 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 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, 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. The flag of Portugal features an armillary sphere, and 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 the Portuguese court. In the flag of the Empire of Brazil, the armillary sphere is also featured.
Modern Ceremonies and Legacy
An artwork-based model of an Armillary sphere has been used since the 1st of March 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 the first-ever ceremony was lit by London 2012 gold medallist Hannah Cockroft. 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 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. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration. The celestial sphere of the present Flag of Brazil replaced the armillary sphere in 1889, yet the symbol remains a powerful representation of human attempts to map the cosmos. The 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. The development of the armillary sphere led to many improvements in techniques and design of all mechanical devices, serving as a bridge between ancient observation and modern engineering.