orery

An orrery is a mechanical model of the solar system. It typically shows the Sun at the center, with planets orbiting around it. The planets are often depicted as spheres on arms that move at different speeds, representing their relative orbital periods. Some orreries also include moons orbiting their respective planets, and some even show the tilt of the Earth's axis, demonstrating seasons.

Historically, orreries were developed as scientific instruments to demonstrate astronomical theories and planetary motion. Early versions date back to ancient Greece, but the most well-known orreries were created during the 18th century, a period of significant advancements in astronomy and clockwork mechanisms. They were valuable tools for teaching and for astronomical calculations.

The complexity and craftsmanship of orreries vary greatly. Simpler models might only show the Sun and a few planets, while more elaborate ones can include all known planets, their moons, and even comets. The term "orrery" is derived from the name of an early patron, Charles Boyle, 4th Earl of Orrery. Today, orreries are often appreciated as decorative objects and as historical artifacts, though modern digital simulations serve a similar educational purpose.