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Planetarium

        Science | Astronomy Terms

Early Planetariums

Early planetariums were either portable pictures of the starry sky painted on the inside of a sphere or dome, or mechanical models of the solar system. In late 17th century Europe, small model planetariums imitating the movement of planets around the sun were built inside clocks. Some of them even showed the revolution of moons around their planets.

During this time, one of the first planetariums, known as the Gottorp Globe, with a portable painting of the starry sky, was made in what now is Germany. The principal part of the planetarium was a hollow copper sphere 10.2 feet (3.1 m) in diameter with a table and a curved bench for 12 people inside it. The sphere's inner surface had the pictures of the constellations. The stars were gold-coated copper nail heads which shone by the light from a central oil lamp. A copper globe representing Earth lay on the table.

In the early 18th century, a model planetarium known as an orrerynamed for the Earl of Orrery, an Irish nobleman who had one made in 1712was built. To this day, small orreries are used by science teachers, because they help students understand the movements of the planets.

After the invention of electric lights and motors in the late 19th century, it became feasible to build large orreries. The first of these was installed in the Deutsches Museum in Munich, Germany, in the early 1920s.

At the center of a circular room was a large lighted globe, which represented the sun. Smaller lighted globes represented the planets and the smaller globes were suspended from the ceiling by rods. The rods were fixed to motor-driven cars that traveled along "orbital" tracks around the globe. Below the globe representing Earth was a small, motor-driven platform that an individual could ride. As the orrery ran, a rider could see a simulation of the planets' revolution around the sun from Earth's perspective. Similar kinds of orreries were later built at the Hayden Planetarium in New York City and at the University of North Carolina at Chapel Hill.