Orrery

An Orrery [ ʔɔɹəɹi ], or a planet machine is a mechanical device that illustrates the rotation of the planets around the sun.

General

Originally it was the name for the Planetarium Orrery. Since 1713 John Rowley ( 1665-1728 ), a planetary machine for Charles Boyle ( 1674-1731 ), the 4th Earl of Orrery, had to be built, refers to those devices according to this noble family as Orrerys. In Germany, known among other things Johann Georg Philipp Matthäus Hahn Neßtfell and by the construction of such machines. For a model of the Pietists Hahn is a clock with calendar that displays the time until the Apocalypse, combined with synchronized helio - and geocentric world machine. This was not completed until after the death of the faucet.

A kind of transparent Orrerys that were illuminated by a projector, so that the planetary motions could be projected on a screen, Eidouranion is called.

Depending on which celestial objects were presented, one differentiates between various special shapes such as tellurium or Jovilabium.

Tellurium

A Tellurium (Latin tellus, the earth ' ) is the special case of a planetary machine to demonstrate the movements of the Earth and Moon. The models of these celestial bodies rotate on a lever arm to a light source that is supposed to represent the sun. With a Tellurium is the origin of the seasons, moon phases and eclipses can illustrate. Some tellurides possess additionally the model for an inner planet, usually Venus, which they actually Orrerys already are.

Schickard Wilhelm (1592-1635) invented a self-built Tellurium with which it is mapped to a portrait from 1631, an early mechanical hand planetarium. The oldest surviving tellurides are associated with the Dutchman Willem Janszoon Blaeu ( 1571-1638 ).

Tellurium is also the original spelling for the chemical element tellurium.

Jovilabium

A Jovilabium (Latin Iovis, genitive singular of Jupiter ) is the special case of a planetary machine that the circulation of the four Galilean moons - represents the planet Jupiter - Io, Europa, Ganymede, Callisto. The name was derived from the astrolabe, a device that can be determined with the star positions.

As first drafted in 1612 from Galileo Galilei five versions of cardboard. He called them Giovilabio. They had no gears and served as a computing device to vorherzuberechnen the positions of the four moons and their eclipse. The time points are required to determine the longitude especially at sea. A brass version, which was made ​​only after Galileo's death, is now at the Museum of the History of Science ( IMSS ) in Florence.

A Jovilabium to a toothed gear designed for the first time in 1677 the astronomer Ole Roemer. It was powered by a hand crank and showed the circulation of the moons with eclipses and transits and should also be helpful in the determination of longitude. But since the size of the moons and their orbits and distances were not made ​​on the same scale, the times of the eclipse could not be displayed correctly, and thus the device was not used. The device probably by Isaac Thuret, clockmaker Louis XIV was built, it has not survived. A replica stands since 1991 in the Tycho Brahe Planetarium in Copenhagen.

Similar devices are from John Flamsteed and Lothar Zumbach of Koesfeld. A model is located in Astronomy Cabinet in Kassel. Another Jovilabium was developed in 1677 by Giovanni Domenico Cassini. It possessed in place of the gears and rods five rotatable discs. With him, the shadow region of Jupiter should be located. The astronomer Vinzenzo Miotti of Murano built in 1781 in Padua Jovilabium. It had rotatable discs and look-up tables to cardboard.

A much improved model was initiated in 1798 by William Pearson ( 1767-1847 ). The mean circulation time and different shadow direction during the rotation of the earth around the sun are reproduced correctly. It also has the synchronous rotation of the Moon. They always show the same face to Jupiter, as the Earth's moon to the earth. It is now in the Museum of the History of Science in Oxford.

Another of Pearson in 1800 designed receiver is part of an Astronomical Clock at the Royal Institution in London. Also in the London Science Museum a Jovilabium Pearson is seen.

A simple mechanical clock is the revolution of the Earth ( minute hand ) and Jupiter ( hour hand ) an inaccurate but simple model.

The overall conclusion is that the Jovilabien not fulfill its intended purpose, to be precise aids in astronomical longitude determination.