Anastrarium, also called aplanetarium, is a medievalastronomical clock made in the 14th century by Italian engineer and astronomerGiovanni Dondi dell'Orologio. The Astrarium was modeled after theSolar System and, in addition to counting time and representingcalendar dates and holidays, showed how theplanets moved around thecelestial sphere in one timepiece.[1] 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.[2][3]
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The first astraria were mechanical devices.Archimedes is said[by whom?] to have used a primitive version that could predict the positions of theSun, theMoon, and theplanets[citation needed]. On May 17, 1902, an archaeologist namedValerios Stais discovered 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.[4] 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.[5][6][7] 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.
According to historiansBedini andMaddison, the earliest astrarium clock with an "almost complete description and incontestable documentation" to have survived is theastrarium completed in 1364 byGiovanni de' Dondi (1318–1388), a scholar and physician of theMiddle Ages.[8] 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 planetsMercury,Venus,Mars,Jupiter, andSaturn. It was conceived according to aPtolemaic conception of the Solar System. De' Dondi was inspired by his fatherJacopo who designed theastronomical clock in 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 Eisinga from 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 inIMAX theaters, with such presentations asThe History of the Universe, as well as other astronomical phenomena.
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