Museo Galileo
Virtual Museum
Armillary sphere
Armillary sphere

Astronomical instrument providing a concrete representation of the orbits of the planets and the Sun by means of armillae (rings) pivoting on a common center. Generally, the armillary sphere reflects the geocentric vision of the universe characteristic of the Ptolemaic system, but there are also heliocentric and Copernican variants, with the Earth and planet armillae pivoting on a common center representing the Sun.