Astrarium

The astrarium made byGiovanni Dondi dell'Orologioshowed hour, year calendar, movement of the planets, Sun and Moon. Reconstruction,Museo Nazionale Scienza e Tecnologia Leonardo da Vinci,Milan.

Anastrarium,also called aplanetarium,is a medievalastronomical clockmade in the 14th century by Italian engineer and astronomerGiovanni Dondi dell'Orologio.The Astrarium was modeled after thesolar systemand, in addition to counting time and representingcalendar datesand holidays, showed how theplanetsmoved around thecelestial spherein one timepiece.This was its main task, in comparison with the astronomical clock, the main task of which is the actual reading of time. A complex mechanism, it combined the functions of a modern planetarium, clock, and calendar into a singular constructive device. Devices that perform this function were known to have been created prior to the design of Dondi, though relatively little is known about them. It is occasionally erroneously claimed by the details of some sources that the Astrarium was the first mechanical device showing the movements of the planets.

History

Greek and Roman World

TheAntikythera mechanism(main fragment)

The first astraria were mechanical devices.Archimedesis saidto have used a primitive version that could predict the positions of theSun,theMoon,and theplanets.On May 17, 1902, an archaeologist namedValerios Staisdiscovered that a lump of oxidated material, which had been recovered from a shipwreck near the Greek island ofAntikythera,held within it a mechanism withcogwheels.This mechanism, known as theAntikythera mechanism,was recently redated to end of the 2nd century BCE.Extensive study of the fragments, using X-rays, has revealed enough details (gears, pinions, crank) to enable researchers to build partial replicas of the original device.Engraved on the major gears are the names of the planets, which leaves little doubt as to the intended use of the mechanism.

By the collapse of theRoman Empire,the know-how and science behind this piece of clockwork was lost.

Middle Ages and Renaissance

According to historiansBediniandMaddison,the earliest astrarium clock with an "almost complete description and incontestable documentation" to have survived is theastrarium completed in 1364byGiovanni de' Dondi(1318–1388), a scholar and physician of theMiddle Ages.The original clock, consisting of 107 wheels andpinions,has been lost, perhaps during the sacking of Mantua in 1630, but de' Dondi left detailed descriptions, which have survived, enabling a reconstruction of the clock. It displays the mean time, sidereal (or star) time and the motions of the Sun, Moon and the five then-known planetsVenus,Mars,Saturn,Mercury,andJupiter.It was conceived according to aPtolemaicconception of the Solar System. De' Dondi was inspired by his fatherJacopowho designed theastronomical clockin the Piazzi dei Signori,Padua,in 1344 – one of the first of its type.

In later ages, more astraria were built. A famous example is theEise Eisinga Planetarium,built in 1774 byEise Eisingafrom Dronrijp, Friesland, the Netherlands. It displayed all the planets and was fixed to the ceiling in a house inFraneker,where it can still be visited.

In modern times, the astrarium has grown into a tourist attraction as a commercially exploitedplanetarium-showing inIMAXtheaters, with such presentations asThe History of the Universe,as well as other astronomical phenomena.

See also

• Astronomical clock
• Planetarium
• Orrery

Literature

• Giovanni Dondi dell'Orologio – "Tractatus astarii"

External links

• AnnosphereAn electro-mechanical model of the earth/sun relationship.
• Science and Society Picture Library:- a picture of De Dondi’s "Astrarium", the world’s first astronomical clock, 1364.
• de Dondi's Astrarium Hi-Tech, 14th Century style
• Het Eise Eisinga Planetarium
• Solar tempometerAn astrarium clock running to the sun.