Astrario Dondi 05869 01 dia - Museo scienza e tecnologia Milano

An astrarium, also called a planetarium, is the

mechanical Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations ...

representation of the cyclic nature of

astronomical object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often u ...

s in one timepiece. It is an

astronomical clock An astronomical clock, horologium, or orloj is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the Sun, Moon, zodiacal constellations, and sometimes major planets. Definition ...

History

Greek and Roman World

The first astraria were mechanical devices.

Archimedes Archimedes of Syracuse (;; ) was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. Although few details of his life are known, he is regarded as one of the leading scientis ...

is said to have used a primitive version that could predict the positions of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

, and the

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

s. On May 17, 1902, an archaeologist named Valerios Stais discovered that a lump of oxidated material, which had been recovered from a shipwreck near the Greek island of

Antikythera Antikythera or Anticythera ( ) is a Greek island lying on the edge of the Aegean Sea, between Crete and Peloponnese. In antiquity the island was known as (). Since the 2011 local government reform it is part of the municipality of Kythira isla ...

, held within it a mechanism with cogwheels. This mechanism, known as the

Antikythera mechanism The Antikythera mechanism ( ) is an Ancient Greek hand-powered orrery, described as the oldest example of an analogue computer used to predict astronomical positions and eclipses decades in advance. It could also be used to track the four-y ...

, 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 end of the

Roman Empire The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Roman Republic, Republican period of ancient Rome. As a polity, it included large territorial holdings aro ...

, the know-how and science behind this piece of clockwork was lost.

Middle Ages and Renaissance

The first modern documented astrarium clock was completed in 1364 by Giovanni de' Dondi (1318–1388), a scholar and physician of the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...

interested in astronomy and

horology Horology (; related to Latin '; ; , interfix ''-o-'', and suffix ''-logy''), . is the study of the measurement of time. Clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clo ...

. The original clock, consisting of 107 wheels and

pinion A pinion is a round gear—usually the smaller of two meshed gears—used in several applications, including drivetrain and rack and pinion systems. Applications Drivetrain Drivetrains usually feature a gear known as the pinion, which may ...

s, 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 planets

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

, Mercury, and

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...

. It was conceived according to a Ptolemaic conception of the Solar System. De' Dondi was inspired by his father

Jacopo Jacopo (also Iacopo) is a masculine Italian given name, derivant from Latin ''Iacōbus''. It is an Italian variant of Giacomo. * Jacopo Aconcio (), Italian religious reformer * Jacopo Bassano (1592), Italian painter * Iacopo Barsotti (1921–1987) ...

who designed the

in the Piazzi dei Signori,

Padua Padua ( ; it, Padova ; vec, Pàdova) is a city and ''comune'' in Veneto, northern Italy. Padua is on the river Bacchiglione, west of Venice. It is the capital of the province of Padua. It is also the economic and communications hub of the ...

, in 1344 – one of the first of its type. In later ages, more astraria were built. A famous example is the

Eise Eisinga Planetarium The Royal Eise Eisinga Planetarium ( nl, Koninklijk(e) Eise Eisinga Planetarium) is an 18th-century orrery in Franeker, Friesland, Netherlands. It is currently a museum and open to the public. The orrery has been on the top 100 Dutch heritage sit ...

, built in 1774 by

Eise Eisinga Eise Jeltes Eisinga (21 February 1744 – 27 August 1828) was a Frisian amateur astronomer who built the Eise Eisinga Planetarium in his house in Franeker, Dutch Republic. The orrery still exists and is the oldest functioning planetarium in the w ...

from Dronrijp, Friesland, the Netherlands. It displayed all the planets and was fixed to the ceiling in a house in

Franeker Franeker (; fry, Frjentsjer) is one of the eleven historical cities of Friesland and capital of the municipality of Waadhoeke. It is located north of the Van Harinxmakanaal and about 20 km west of Leeuwarden. As of 1 January 2014, it had 12 ...

, where it can still be visited. In modern times, the astrarium has grown into a tourist attraction as a commercially exploited

planetarium A planetarium ( planetariums or ''planetaria'') is a Theater (structure), theatre built primarily for presenting educational entertainment, educational and entertaining shows about astronomy and the night sky, or for training in celestial navi ...

-showing in

IMAX IMAX is a proprietary system of high-resolution cameras, film formats, film projectors, and theaters known for having very large screens with a tall aspect ratio (approximately either 1.43:1 or 1.90:1) and steep stadium seating. Graeme ...

theaters, with such presentations as ''The History of the Universe'', as well as other astronomical phenomena.

References

Literature

* Giovanni Dondi dell'Orologio – "''Tractatus astarii''"

External links