Ptolemaic armillary sphere

An Earth-centred cosmos

This model depicts Ptolemy’s Earth-centred cosmos. The bands illustrate the motion of the Sun, Moon and stars. Armillary spheres were used in medieval times to teach priests how to calculate the hours of prayer at sunrise and sunset. Portraits of noblemen often included an armillary sphere to suggest wisdom and learning. More recently, novelist Umberto Eco chose the armillary sphere as a gruesome murder weapon in his 1983 book The Name of the Rose.