More than a hundred years ago an extraordinary mechanism was found by sponge divers at the bottom of the sea near the island of Antikythera. It astonished the whole international community of experts on the ancient world. Was it an astrolabe? Was it an orrery or an astronomical clock? Or something else?
For decades, scientific investigation failed to yield much light and relied more on imagination than the facts. However research over the last half century has begun to reveal its secrets. It dates from around the end of the 2nd century B.C. and is the most sophisticated mechanism known from the ancient world. Nothing as complex is known for the next thousand years. The Antikythera Mechanism is now understood to be dedicated to astronomical phenomena and operates as a complex mechanical "computer" which tracks the cycles of the Solar System.
Previous researchers have used the latest technologies available to them -such as x-ray analysis- to try to begin to unravel its complex mysteries. Now a new initiative is building on this previous work, using the very latest techniques available today. The Antikythera Mechanism Research Project is an international collaboration of academic researchers, supported by some of the world's best high-technology companies, which aims to completely reassess the function and significance of the Antikythera Mechanism.
The project is under the aegis of the Hellenic Ministry of Culture and was initially supported by a grant from the Leverhulme Trust, UK. More details bout subsequent funding are here. The project has received strong backing from the National Archaeological Museum in Athens, which is custodian of this unique artefact. Two of the Museum's senior staff, Head of Chemistry, Eleni Magou, and Archaeologist-museologist, Mary Zafeiropoulou, have co-ordinated the Museum's side of the project and are actively involved with the research.
One UK and two Greek universities are the core of the academic research group -the astronomer Mike Edmunds and the mathematician and filmmaker Tony Freeth (University of Cardiff), the astronomer John Seiradakis (University of Thessalonica), the astronomer Xenophon Moussas and the physicist and historian of science Yanis Bitsakis (University of Athens). And last, but not least, the philologist and palaeographer Agamemnon Tselikas (NBG Cultural Foundation).
-------------
The Antikythera mechanism is believed to be an ancient mechanical analog computer (as opposed to most computers today which are digital computers) designed to calculate astronomical positions. It was discovered in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to about 150-100 BC. It is especially notable for being a technological artifact with no known predecessor or successor; other machines using technology of such complexity would not appear until the 18th century.
Discovery
Sometime during the year 1901, Elias Stadiatis, a Greek sponge diver, with a sponge diving group, discovered the wreck of an ancient cargo ship off Antikythera island at a depth of 50 meters. (Sponge divers had earlier retrieved several statues and other artifacts from the site. The mechanism itself was discovered in 1901.) The name has been confused in some recent publications with that of a politician of the same name.
It was noticed that a piece of rock recovered from the site had a gear wheel embedded in it. Examination revealed that the rock was in fact a heavily encrusted and corroded mechanism that had survived the shipwreck in three main parts and dozens of smaller fragments.The device itself was surprisingly thin, about 33 cm (13 in) high, 17 cm (6.7 in) wide, and 9 cm (3.5 in) thick, made of bronze and originally mounted in a wooden frame. It was inscribed with a text of over 2,000 characters, many of which have been deciphered.
Jacques-Yves Cousteau visited the wreck for the last time in 1978, but found no more remains of the Antikythera Mechanism. Professor Michael Edmunds of Cardiff University who led the study of the mechanism said: "This device is just extraordinary, the only thing of its kind. The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop. Whoever has done this has done it extremely carefully."
The device is displayed in the Bronze Collection of the National Archaeological Museum of Athens, accompanied by a reconstruction made and offered to the museum by Derek de Solla Price. Another reconstruction is on display at the American Computer Museum in Bozeman, Montana.
Origins
The origins of the mechanism are unclear, as are the circumstances by which it came to be on the cargo ship. The ship was Roman, but there is no doubt that the mechanism itself was made in Greece.
One hypothesis is that the device was constructed at an academy founded by the ancient Stoic philosopher Posidonius on the Greek island of Rhodes, which at the time was known as a centre of astronomy and mechanical engineering. Investigators have suggested that the ship could have been carrying it to Rome, together with other treasure looted from the island to support a triumphal parade being staged by Julius Caesar.
Function and Purpose
The Antikythera mechanism is one of the world's oldest known geared devices. It has puzzled and intrigued historians of science and technology since its discovery. Following decades of work in order to clean the device, systematic investigations were undertaken in 1951 by British Derek J. de Solla Price, professor of history of science at Yale University at that time.
In June 1959, in a front-page article in Scientific American titled "An ancient Greek computer", he brought forth the theory that the Antikythera mechanism was a device for calculating the motions of stars and planets, which would make the device the first analog computer. Up until that time the function of the Antikythera mechanism was largely unknown, though it had been correctly identified as an astronomical device, perhaps being an astrolabe.
In 1971 the Greek nuclear research center "DEMOKRITOS" performed gamma-ray scans of the mechanism. In 1972 Price teamed up with Greek nuclear physicist Christoforos Karakalos to carry out X-ray analysis of the mechanism, in this way revealing critical information concerning the device's interior configuration.
In 1974 he authored "Gears from the Greeks: the Antikythera mechanism - a calendar computer from ca. 80 B.C.", where he presented a model of how the mechanism could have functioned. Recent research breakthroughs seem to give credence to Price's theory.
The device is all the more impressive for its use of a differential gear - previously believed to have been invented in the 16th century - and for the level of miniaturization and complexity of its parts, which is comparable to that of clocks made in the 18th century.
The differential gear arrangement is composed of 30+ gears with teeth formed through equilateral triangles. When past or future dates were entered via a crank (now lost), the mechanism calculated the position of the sun, moon or other astronomical information such as the location of other planets.
The use of differential gears enabled the mechanism to add or subtract angular velocities. The differential was used to compute the synodic lunar cycle by subtracting the effects of the sun's movement from those of the sidereal lunar movement.
It is possible that the mechanism is based on heliocentric principles, rather than the then dominant geocentric view espoused by Aristotle and others. This may indicate that the heliocentric view was more widely accepted at the time than was previously thought.While the Antikythera mechanism was certainly remarkably advanced for its era, it was possibly not unique.
Cicero, writing in the 1st century BC, mentions an instrument "recently constructed by our friend Poseidonius, which at each revolution reproduces the same motions of the sun, the moon and the five planets." (Cicero was himself a student of Poseidonius.)
Similar devices are mentioned in other ancient sources. It also adds support to the idea that there was an ancient Greek tradition of complex mechanical technology which was later transmitted to the Arab world, where similar but simpler devices were built during the medieval period.
The early 9th century Kitab al-Hiyal ("Book of Ingenious Devices"), commissioned by the Caliph of Baghdad, records over a hundred mechanical devices described in Greek texts that had been preserved in monasteries. Such knowledge could have yielded to or been integrated with European clockmaking and ancient cranes.
The device's actual purpose still remains unclear, as we do not know its full range of capabilities. Some investigators believe that the Antikythera mechanism could have been used to track celestial bodies for auspicious occasions such as religious events or births.
Price suggested that it might have been on public display, possibly in a museum or public hall in Rhodes. The island was renowned for its displays of mechanical engineering, particularly automata, which apparently were a speciality of the Rhodians; to quote Pindar's seventh Olympic Ode:
The animated figures stand
Adorning every public street
And seem to breathe in stone, or
move their marble feet.
Investigations and Reconstructions
Price's model, as presented in his "Gears from the Greeks: the Antikythera mechanism - a calendar computer from ca. 80 B.C.", was the first, theoretical, attempt at reconstructing the device. According to that model, the front dial shows the annual progress of the sun and moon through the zodiac against the Egyptian calendar. The upper rear dial displays a four-year period and has associated dials showing the Metonic cycle of 235 synodic months, which approximately equals 19 solar years. The lower rear dial plots the cycle of a single synodic month, with a secondary dial showing the lunar year of 12 synodic months. A British orrery maker named John Gleave, constructed a replica based hereupon, though with some very slight modifications of his, in order for it to be functional. The following link gives an idea of the internals of this device, though later researchers have doubts as to whether Price's model is an accurate representation of the original Antikythera mechanism.
A partial reconstruction was built by Australian computer scientist Allan George Bromley (19472002) of the University of Sydney and Sydney clockmaker Frank Percival. This project led Bromley to review Price's X-ray analysis and to make new, more accurate X-ray images that were studied by Bromley's student, Bernard Gardner, in 1993. His model differed significantly from Price's earlier proposition, though it wasn't considered satisfactory either.
Another reconstruction was made in 2002 by Michael Wright, mechanical engineering curator for The Science Museum in London, working with Allan Bromley. He analyzed the mechanism using linear tomography, which can create images of a narrow focal plane, and thus visualized the gears in great detail. In Wright's reconstruction, the device not only models the motions of the sun and moon, but of all the classical planets.
0 yorum:
Yorum Gönder