Celestial Mechanism

This one actually works. Celestial Mechanism is a large carved wood wall sculpture with real brass rings built into it that rotate — and as they turn they can show the current phase of the moon, the date, and the time in cities you choose. It's a clock and an astronomical instrument crossed with a piece of art, and the moving brass is the heart of it.

It descends from the most beautiful instruments humans ever built to understand the sky. The astrolabe — the name means "star-taker" in Greek — was an ancient handheld device of rotating discs used to work out the time, the positions of stars, and the moments of sunrise and sunset. It was likely a late Greek invention, credited to Apollonius of Perga around 220–150 BC, and was perfected in the medieval Islamic world, where from the ninth century it became essential for finding prayer times and the direction of Mecca [World History Encyclopedia; BnF]. Early mechanical clocks were essentially clockwork astrolabes — the astronomer Ibn al-Shatir built an astrolabic clock in the early 14th century, and Richard of Wallingford's clock of around 1330 was a star map turning behind a fixed frame [Astrolabe, Wikipedia]. Then came the orrery, a mechanical model of the solar system with gears turning the planets; the first modern one was built around 1704 by clockmakers George Graham and Thomas Tompion [Invaluable]. Celestial Mechanism sits in that lineage: Indian and Islamic sky-instruments plus European clockmaking, rebuilt as something for your wall.