Planetariums: from Antikythera's machine to modern projectorsSince ancient times humans, through patient observations, have tried to give an explanation to the celestial motions, elaborating rational and coherent theories.
The oldest representations of the sky are the celestial globes, which date back to classical antiquity: tradition attributes the construction of the first one to Anaximander of Miletus.
One of the oldest globes that has reached us is the Farnese Atlas: it comes from the Farnese Palace in Rome, to which it owes its name, and is currently kept in the Archaeological Museum of Naples.
It is a marble statue composed of a giant, Atlas, which holds on its shoulders a celestial globe on which 42 constellations, the ecliptic and the celestial equator, are carved in bas-relief.
An enigma of antiquity is represented by the so-called Antikythera Machine dated between the 1st BC and the 3rd century AD. It was found in 1902 among the remains of an ancient ship wrecked off the coast of the Antikythera island between Greece and Crete.
It was composed of four copper fragments, which showed the remains of what must have been a mechanical device with complicated gears.
The astrolabe (from the Greek meaning star-taker), considered one of the oldest scientific measuring instruments in the world. Its origin is uncertain: it seems that the authors in antiquity indicated with this name instruments built according to similar principles, but in different ways; perhaps it was already in use many centuries before Ptolemy.
The astrolabe must have been built with great technical and manual skill if Ptolemy and Hipparchus, the other great astronomer of antiquity (about 180 -125 BC), used this type of instrument to make most of the observations for their famous star catalogues.
One of the derivation tools of the astrolabe is the armillary sphere. This was also the work of Greek astronomers, but became very popular from the 15th century onwards.
It was formed by a series of graduated circles representing imaginary circles such as the equator, the tropics, the Arctic and Antarctic polar circles, the meridians passing at the points of Aries and Libra to indicate the spring and autumn equinoxes and the oblique band of the ecliptic divided into the 12 signs of the zodiac.
At the center of the rings there was the sphere representing the Earth (in the geocentric system) or the Sun (in the Copernican system). From the point of view of their author, the armillary spheres, built essentially for educational purposes, had different characteristics.In addition to the astrolabe and the armillary spheres, from the 13th century onwards, clocks were built that had little to do with the passage of time, but which represented the planets and measured their movement.
The first large public clocks in the 15th century usually resembled more gigantic planetariums than modern time measuring devices.
Famous is the one on Prague City Hall dating back to 1410 where an astronomical sphere indicates the beginning of the astronomical seasons and the relative movements of the Sun and Moon and the phases of the moon.
In Italy the first astronomical clock, which reproduced the movements of the Sun and the Moon, was built in Padua in 1344 by Jacopo Dondi.
The planetarium table or orrery was invented in England at the beginning of the 18th century.
This word first appeared in 1713 and derives from the name of the scientific instrument collector Charles Boyle, fourth Earl of Orrery. He had encouraged and favored the creation of this kind of instruments that reproduced the motion of the Sun, Earth and Moon.
The most common image of the planetarium is that of a building with a large hemispherical dome, on which the images of the stars and other celestial bodies are projected. In fact, the planetarium consists of a projector of the stars and a dome that forms the screen, various optional accessories for the projection of slides and some special effects equipment.
The "old" Planetarium of Rome
After the First World War (1915-18), Germany offered Italy a Zeiss planetarium to repair the war damage. It was a very newly designed device that had met with great enthusiasm in the German public: it was the first planetarium that had to open outside the Austro-German world.
In 1928 the Planetarium of Rome was inaugurated.