armillary sphere

armillary sphere
an ancient instrument consisting of an arrangement of rings, all of which are circles of the same sphere, used to show the relative positions of the celestial equator, ecliptic, and other circles on the celestial sphere.

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 early astronomical device for representing the great circles of the heavens, including in the most elaborate instruments the horizon, meridian, Equator, tropics, polar circles, and an ecliptic hoop. The sphere is a skeleton celestial globe, with circles divided into degrees for angular measurement. In the 17th and 18th centuries such models—either suspended, rested on a stand, or affixed to a handle—were used to show the difference between the Ptolemaic theory of a central Earth and the Copernican theory of a central Sun.

      The earliest known complete armillary sphere with nine circles is believed to have been the meteōroskopion of the Alexandrine Greeks (c. AD 140), but earlier and simpler types of ring instruments were also in general use. Ptolemy, in the Almagest, enumerates at least three. It is stated that Hipparchus (146–127 BC) used a sphere of four rings; and in Ptolemy's instrument, the astrolabon, there were diametrically disposed tubes upon the graduated circles, the instrument being kept vertical by a plumb line.

      The Arabs employed similar instruments with diametric sight rules, or alidades, and it is likely that those made and used in the 12th century by Moors in Spain were the prototypes of all later European armillary spheres.

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Universalium. 2010.

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  • Armillary sphere — Sphere Sphere, n. [OE. spere, OF. espere, F. sph[ e]re, L. sphaera,. Gr. ??? a sphere, a ball.] 1. (Geom.) A body or space contained under a single surface, which in every part is equally distant from a point within called its center. [1913… …   The Collaborative International Dictionary of English

  • Armillary sphere — Armillary Ar mil*la*ry, a. [LL. armillarius, fr. L. armilla arm ring, bracelet, fr. armus arm: cf. F. armillaire. See {Arm}, n.] Pertaining to, or resembling, a bracelet or ring; consisting of rings or circles. [1913 Webster] {Armillary sphere},… …   The Collaborative International Dictionary of English

  • armillary sphere — [är′mə ler΄ē] n. [< L armilla, armlet, bracelet < armus: see ARM2] an ancient astronomical sighting instrument representing the great circles of the horizon, the ecliptic, the meridian, etc …   English World dictionary

  • Armillary sphere — An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of the celestial sphere. Description and use of the armillary sphere The exterior parts of this machine are a compages of brass rings, which represent …   Wikipedia

  • armillary sphere — noun Etymology: French sphère armillaire, from Medieval Latin armilla, from Latin, bracelet, iron ring, from armus shoulder more at arm Date: 1664 an old astronomical instrument composed of rings showing the positions of important circles of the… …   New Collegiate Dictionary

  • armillary sphere — ar′millary sphere′ n. astron. an ancient astronomical instrument consisting of an arrangement of metal rings used to show the relative positions of the celestial equator and other circles on the celestial sphere …   From formal English to slang

  • armillary sphere — /aˌmɪləri ˈsfɪə/ (say ah.miluhree sfear) noun Astronomy an arrangement of rings, all circles of a single sphere, showing the relative positions of the principal circles of the celestial sphere …  

  • armillary sphere — noun a revolving model of the celestial sphere constructed from metal rings representing the equator, the tropics, etc. Origin C17: from mod. L. armillaris relating to an armilla , a similar astronomical instrument used by ancient astronomers,… …   English new terms dictionary

  • armillary sphere — noun An instrument consisting of graduated metal circles used to represent the motions of celestial bodies around the earth …   Wiktionary

  • armillary sphere — noun a celestial globe consisting of metal hoops; used by early astronomers to determine the positions of stars • Syn: ↑armilla • Hypernyms: ↑celestial globe …   Useful english dictionary

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