Geocentric armillary sphere

Also called Ptolemaic
signed: G. B. Paravia and comp. Italy, 19th century

Linked to the most ancestral vision of the universe that thought the earth was the center of everything.

This type of Armillary Sphere (or spherical astrolabe) was invented by Eratosthenes in 225 BC.

It envisaged a structure of wooden or metal rings (armille) placed in a horizontal position to represent from north to south: the circle of the Northern Arctic Pole, the Tropic of Cancer, the equinoctial line or Equator, the Tropic of Capricorn and finally the Arctic Pole Southern.

Wedged in the large vertical armilla of the colure of the equinoxes, and enclosed by the Ecliptic (the ideal circular trajectory described by the sun on the celestial sphere in one year) in this case represented by a slightly transversal band, richly graduated and decorated with the names of the months and the corresponding zodiac symbols.

At the center of the structure is the earth, represented as a spherical planet bearing the cartography, updated according to the knowledge of the period; and around it, connected to a thin metal band, the Sun and the Moon rotate, represented as two circles of different diameters.

This spherical structure is enclosed in the meridian circle (the outermost vertical armilla) and locked into the horizon circle
(the largest horizontal armilla) which is fixed, by means of four semicircular band uprights bearing the names and technical data of numerous cities of the world to the turned and ebonized base.