Armillary sphere

An armillary sphere is a model of objects in the sky, consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features such as the ecliptic. It differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations rather than a skeletal framework of rings. The device was invented separately, in ancient China possibly as early as the 4th century BC and in ancient Greece during the 3rd century BC, with later use in the Islamic world and medieval Europe.