Orreries

I’ll bet you don’t know what an orrery is! It is one of those things you see in museums that model the solar system. The sun and the planets are made out of various size balls held on wires, and they circle around like the hands of a clock.

Orreries are hopelessly out of scale. In reality, if the sun was three feet (one meter) in diameter, the earth would be the size of a pea. The pea would be circling the three-foot sun on a wire 100 feet (30 meters) long. This whole thing, with the pea-size earth, and with all the other planets would be over ninety miles (145 kilometers) in diameter.