An antique brass clockwork solar system: meshing gears drive planetary arms orbiting a glowing sun. Real orrery machines, first built in the early 1700s and named after the Earl of Orrery, used stacks of precisely-cut gears to reproduce the relative orbital periods of the planets purely through mechanical ratios—no motors or electronics. In reality Mercury circles the Sun in 88 days versus Neptune's 165 years, a ratio of over 680:1, which clockmakers approximated with nested gear trains exactly like the meshing gears driving these arms. Drag to orbit, scroll to zoom.