The world’s oldest working planetarium is located in the living room of a small, two-story house in the city of Franeker, in the Netherlands. The house belonged to an 18th-century wool comber called Eise Eisinga, who built this remarkable mechanical model of the solar system (also called an orrery) to show to his townsfolk how the heavens actually worked.

Eisinga’s planetarium was built at a time when the nation was gripped by panic and hysteria. It started with a small book published in 1774 by a Dutch preacher named Eelco Alta, from the Frisian village of Bozum, in which he made a clichéd yet terrifying prediction — the end of earth. Earlier, astronomers had announced that an unusual conjunction of the moon and the planets Mercury, Venus, Mars, and Jupiter was to happen on 8 May, 1774. Alta argued that on this very day, the planets and their moon would collide, with the result that the earth would be propelled out of its orbit and burned by the sun.

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Eise Eisinga, who had mastered mathematics and astronomy in addition to combing wool, wanted to show there was no reason for panic. To prove Alta wrong and to reassure the Dutch people, Eisinga decided to build a planetarium in his living room.

The Eisinga Planetarium “hangs” from the ceiling — a golden orb, somewhat larger than a baseball, represents the sun and descends from the middle of the ceiling, with a number of other smaller orbs, representing the planets, rest in concentric grooves around the sun. A pendulum clock and a series of intricate mechanical gears, which Eisinga fashioned with his own hand, drives the planets at the precise rate they do in our solar system. This means that the Earth takes exactly 365 days to make one complete rotation. Mercury takes 88 days, Venus 224 days, Mars 687 days and Saturn over 29 years. These gears are located in the attic above the ceiling and hidden from view.

The planetarium was built at a scale of 1 millimeter: 1 million kilometers, so that it would fit on Eisinga’s living room ceiling. The planets, however, are not to scale because this would make them too small to see. In addition to the basic orrery, the model provides information such as time of sunrise and sunset, the phase of the moon and other astronomical phenomena. Aside from some minor adjustments that need to be made every four years to account for the extra day in a leap year, the model is still precise to this day.

Eisinga expected to finish the planetarium within six months, but it took him seven long years. He eventually completed it in 1781. The Eisinga Planetarium received a lot of visitors when it opened. When King William I visited the planetarium in 1818, he was so impressed that he subsequently bought it for the Dutch state.

Eisinga died in 1828, after which his son took over the running of the planetarium. The Eisinga family continued to run the planetarium until 1922. Since then, it's run by curators appointed by the city of Franeker.

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Sources: Wikipedia / www.entoen.nu / Mokeham