Armillary sphere
A brass framework of graduated rings stands at the center of an armillary sphere. This metal skeleton represents lines of celestial longitude and latitude. The equinoctial ring divides into 360 degrees starting from its intersection with the ecliptic in Aries. It also splits into 24 hours to show the sun's right ascension in time. Another ring called the ecliptic divides into 12 signs. Each sign contains 30 degrees and marks the months and days of the year. The tropic of Cancer touches the ecliptic at the beginning of Cancer. The tropic of Capricorn touches it at the beginning of Capricorn. Both circles sit 23 degrees from the equinoctial circle. The Arctic Circle and Antarctic Circle each measure 23 degrees from their respective poles. An equinoctial colure passes through the north and south poles of the heavens. It crosses the solstitial points in Cancer and Capricorn within the ecliptic. A small sun Y moves around the ecliptic B-B by turning a nut b fixed in the north pole. A mechanism causes the moon to move in an orbit crossing the ecliptic at an angle of 5 degrees. This allows for shifting lunar nodes backward in the ecliptic as they shift in the heavens. Within these circular rings sits a small terrestrial globe I fixed on an axis K. The flat celestial meridian L is set directly over the meridian of any place on the globe. A movable horizon M turns upon two strong wires proceeding from its east and west points. The sphere can show either the real motion of the earth or the apparent motion of the heavens depending on how the winch W is turned.
Chinese astronomers Shi Shen and Gan De developed primitive single-ring armillary instruments during the 4th century BC. These early devices measured the north polar distance known as declination. Astronomer Geng Shouchang introduced the first permanently fixed equatorial ring in 52 BC during the Western Han dynasty. Fu An and Jia Kui added the ecliptic ring by 84 AD in the subsequent Eastern Han period. Zhang Heng completed the world's first water-powered celestial globe in 125 AD. He operated his armillary sphere using an inflow clepsydra clock. Kong Ting reorganized the arrangement of rings in 323 AD so that the ecliptic ring could be pegged to the equator at any desired point. Li Chunfeng created one with three spherical layers in 633 AD to calibrate multiple aspects of astronomical observations. Yi Xing combined Zhang Heng's water powered celestial globe with an escapement device in 723 AD. This device hit drums every quarter-hour and rang bells automatically every full hour. Su Song built a famous clock tower by 1094 during the Song dynasty. It employed Yi Xing's escapement with waterwheel scoops filled by clepsydra drip. The mechanism powered a crowning armillary sphere and mechanically operated manikins exiting doors to ring bells and gongs.
The Greek astronomer Hipparchus credited Eratosthenes as the inventor of the armillary sphere between 276 BC and 194 BC. Names of this device in Greek include astrolabos and krikōtē sphaira meaning ringed sphere. Slightly developed versions were crossed by another ring fixed in the plane of the meridian. Shadows served as indices of the sun's positions in combinations with angular divisions. When several rings or circles combined representing great circles of the heavens, the instrument became an armillary sphere. These spheres were used as teaching tools already in the 3rd century BC. Fully developed forms 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 likely used an armillary sphere of four rings. The Greco-Roman geographer Ptolemy described his instrument the astrolabon in his Almagest. It consisted of at least three rings with a graduated circle inside carrying two small tubes positioned opposite each other. A vertical plumb-line supported these tubes within the sliding mechanism.
Persian and Arab astronomers such as Ibrahim al-Fazari and Abbas Ibn Firnas continued to build and improve on armillary spheres. The spherical astrolabe 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. This text remains the earliest extant treatise on the instrument. The earliest description of the spherical astrolabe dates back to the Persian astronomer Nayrizi who flourished between 892 and 902. Pope Sylvester II applied the use of sighting tubes with his armillary sphere to fix the position of the pole star. He recorded measurements for the tropics and equator using these devices. Jamal al-Din of Bukhara commissioned astronomical instruments including an armillary sphere when asked to set up an Islamic Astronomical Institution in Khubilai Khan's new capital. Chinese astronomers had been building them since at least 1092 according to historical records. These adaptations refined the design before its adoption in Renaissance Europe.
Danish astronomer Tycho Brahe constructed three large armillary spheres between 1546 and 1601. He used these instruments for highly precise measurements of the positions of stars and planets. His findings were described in his work Astronomiae Instauratae Mechanica published in Wandesburg in 1598. Renaissance scientists and public figures often had their portraits painted showing them with one hand on an armillary sphere. This gesture represented the zenith of wisdom and knowledge. The development of these complex mechanical devices led to many improvements in techniques and design of all mechanical devices. 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. Artist Jon Bausor created this sphere which includes a wheelchair that users can rotate to spark the flame. London 2012 gold medallist Hannah Cockroft lit the first-ever ceremony flame.
The flag of Portugal features an armillary sphere as a central element. In the end of the 15th century it became the personal heraldic badge of the future King Manuel I of Portugal. During his reign the intense use of this badge transformed the sphere from a simple personal symbol into a national one. It represented the Kingdom of Portugal and 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. When Brazil gained status as kingdom united with Portugal in 1815 its coat of arms was formalized as a golden armillary sphere in a blue field. Representing Brazil the armillary sphere appeared in the arms and flag of the United Kingdom of Portugal, Brazil and the Algarves. When Brazil became independent as an empire in 1822 the sphere remained present in its national arms and flag. The celestial sphere replaced the armillary sphere in the Flag of Brazil in 1889. The sphere was reintroduced in the national arms and flag of Portugal in 1911. Early Chinese export ceramics made for the Portuguese court also featured this symbol on their surfaces.
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Common questions
Who invented the armillary sphere and when was it created?
The Greek astronomer Hipparchus credited Eratosthenes as the inventor of the armillary sphere between 276 BC and 194 BC. Chinese astronomers Shi Shen and Gan De developed primitive single-ring armillary instruments during the 4th century BC.
What rings make up an armillary sphere and what do they measure?
An armillary sphere consists of a brass framework of graduated rings that represent lines of celestial longitude and latitude. The equinoctial ring divides into 360 degrees to show the sun's right ascension in time while the ecliptic ring divides into 12 signs to mark the months and days of the year.
How did ancient Chinese astronomers improve the design of the armillary sphere?
Astronomer Geng Shouchang introduced the first permanently fixed equatorial ring in 52 BC during the Western Han dynasty. Zhang Heng completed the world's first water-powered celestial globe in 125 AD using an inflow clepsydra clock to operate his armillary sphere.
Why is the armillary sphere featured on the flag of Portugal?
In the end of the 15th century it became the personal heraldic badge of the future King Manuel I of Portugal. During his reign the intense use of this badge transformed the sphere from a simple personal symbol into a national one representing the Kingdom of Portugal and its Overseas Empire.
When was the modern Paralympic heritage flame model created by Jon Bausor?
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. Artist Jon Bausor created this sphere which includes a wheelchair that users can rotate to spark the flame.