Early Models of the Solar System

Early Models of the Solar System

In the 17th century, with the rapid development of the mechanical sciences, the first attempts were made to demonstrate by models the relative motions of the moon and planets on a sun-centered or heliocentric basis. In Paris, the Danish astronomer Ole Römer, famous for his discovery of the finity velocity of light, devised machines which showed the relative motions of four of Jupiter`s satellites, and the satellites and ring of Saturn. Another of his machines, completed in 1680, showed the motions of the planets about the sun, and of the moon about the earth. The gearing, hand operated, lay behind a vertical plate in which elliptical slots represented the orbits of the planets, while in each slot moved a spindle surmounted by a small model planet. This planetarium made a great impression in Paris and copies were sent to Persia and China.

Solar System

In 1682, Johannes van Ceulen of The Hague made a small planetarium to a design provided by the Dutch scientist Christian Huygens. In his design Huygens solved the problem of using only a small number of simple gear-wheels to drive model planets at approximately the correct proportionate speeds. The machine, now in the National Museum of the History of Science, Leyden, takes the form of an octagonal box about 26 inches across and seven inches deep. Under the action of a clockwork mechanism, the model planets move with uniform motions in circular slots cut in the copper faceplate.

The actual planets, however, move with non-uniform motions in elliptical orbits. As a first approximation to this requirement, Huygens arranged the circular slots with their centres displaced from the central sun globe.

When will we announce that other worlds really exist? Image: Close Up © Megan Jorgensen (Elena)