Three armillary, Jérôme de Lalande – Paris 1775:
1. Heliocentric model of our Solar System (with the Sun at the center)
Inv. ROB ID 028
2. Celestial sphere Inv. ID ROB 026
3. Geocentric model of our Solar System (with the Earth at the center)
Inv.ROB ID 029

OBJECT 5

Three armillary
All three instruments were designed in Paris in 1775 by Jérôme de Lalande. They are made of wood, paper and cardboard and were probably a part of a set of four instruments (the terrestrial globe, the celestial sphere, the solar system and the stars). The fourth instrument, the terrestrial globe, is missing from the collection.

On the celestial sphere are the different artistically painted constellations, with indications of equidistant longitudes and latitudes, the meridian, the ecliptic and the inscription « M. Delalande de l’Acad. des Sciences sous le Priv. De l’Acad. 1775 ».

The armillary sphere with the Earth at the center, the geocentric model, is made of rings which symbolize different circles of latitude of the Earth, such as the Equator, the Polar Circles, the Tropic of Cancer and the Tropic of Capricorn. Moreover, there are fixed rings that indicate the calendar, the celestial equator and the constellations. The apparent movement of the Sun is illustrated with an extra support.

The armillary sphere with the Sun at the center, the heliocentric model, shows our Solar System. It contains the orbit of the Moon around the Earth and rings which represents the orbits of the planets Mercury, Venus, Mars and Jupiter.

The armillary sphere was invented by Eratosthenes in 255 BC. The name of the instrument comes from the Latin armilla, which means bracelet. The armillary sphere was an instrument developed to determine time and positions.

Portraits of Renaissance scientists show them with an armillary sphere, and reprent a symbol of wisdom and knowledge. In Christian iconography, an armillary sphere is the attribute of Astronomy, the symbol of the universe and one of the seven liberal arts.

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