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Niels Bohr Institute > Who, What, When > > Ole Rømer > Ole Rømer's machines

09 February 2012

Ole Rømer’s machines

When Ole Rømer was not occupied with other duties, he constructed various machines for astronomical use.

While he was living in Paris he made a so-called Jovilabe; a machine that shows how Jupiter’s moons move around the planet. Later he made a similar machine to show Saturn and its moons. He also made an Eclipsarium, which could very accurately calculate when solar and lunar eclipses would take place, and a Planet Machine, which knew how Mercury, Venus, the Earth, Mars, Jupiter and Saturn moved around the Sun. A very skilled watchmaker in France assisted Ole Rømer in making the mechanics of the machines.

Drawings of a Jovilabe (left), an Eclipsarium (middle) and a Planet Machine (right).

Both the Eclipsarium and the Planet Machine were made in quadruplicate. The first set was kept by the King in Paris, the second set was transported to Copenhagen to Christian V. The last two sets were sent to the East as gifts to the Emperor of China and the King of Siam. The last two sets no longer exist today, but both the French in Paris and the Danish survive, the latter is currently exhibited at Rosenborg Castle in Kongens Have.

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