Armillary Sphere

This astronomical instrument is used to represent the orbits of the planets, stars, and the Sun by means of rings pivoting on a common center. Typically, at the center is a large globe representing the Earth. Surrounding brass rings portray celestial coordinates, meridians, equators, and zodiac constellations. Armillary spheres were first developed in Asia in the 4th century BCE and came into use in Europe by the 10th century. They are essentially the 3-D version of the astrolabe. The modern equivalent is the planetarium.