Antikathera Mechanism – How Technologically Advanced Were The Ancient Greeks?



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Antikythera mechanism
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The Antikythera mechanism (/ˌæntɨkɨˈθɪərə/ ant-i-ki-theer-ə or/ˌæntɨˈkɪθərə/ ant-i-kith-ə-rə) is an ancient analog computer[1][2][3][4] designed to predict astronomical positions andeclipses. It was recovered in 1900–01 from the Antikythera wreck, a shipwreck off the Greek island of Antikythera.[5] The computer's construction has been attributed to the Greeks and dated to the early1st century BC. Technological artifacts approaching its complexity and workmanship did not appear again until the 14th century, when mechanical astronomical clocks began to be built in Western Europe.[6]

The mechanism was housed in a wooden box about 340 × 180 × 90 mm in size and comprised 30 bronze gears (although more could have been lost). The largest gear, clearly visible in fragment A, was about 140 mm in diameter and had 223 teeth. The mechanism's remains were found as 82 separate fragments of which only seven contain any gears or significant inscriptions.[7][8]

Today, the fragments of the Antikythera mechanism are kept at theNational Archaeological Museum of Athens.

Origins and discovery[edit]
See also: Antikythera wreck

This machine has the oldest known complex gear mechanism and is sometimes called the first known analog computer,[9][10][11][12][13][14][15][16] although the quality of its manufacture suggests that it may have had undiscovered predecessors[17] during the Hellenistic Period.

It appears to be constructed upon theories of astronomy and mathematics developed by Greek astronomers and is estimated to have been made around 100 BC. In 1974, British science historian and Yale University professor Derek de Solla Price concluded from gear settings and inscriptions on the mechanism's faces that the mechanism was made about 87 BC and was lost only a few years later.[18] Jacques Cousteau visited the wreck in 1978[19] and recovered new dating evidence. It is believed the mechanism was made of a low-tin bronze alloy (95% copper, 5% tin), but the device's advanced state of corrosion has made it impossible to perform an accurate compositional analysis.[20] All of the mechanism's instructions are written in Koine Greek,[21][not in citation given] and the consensus among scholars is that the mechanism was made in the Greek-speaking world.

Recent findings of The Antikythera Mechanism Research Project suggest the concept for the mechanism originated in the colonies of Corinth, since some of the astronomical calculations seem to indicate observations that can be made only in the Corinth area of ancient Greece. Syracuse was a colony of Corinth and the home of Archimedes, which might imply a connection with the school of Archimedes.[22] Another theory states that coins found by Jacques Cousteau in the 1970s at the wreck site and dated to the time of the construction of the device, suggest that its origin may have been from the ancient Greek city of Pergamon.[23] Pergamon was also the site of the famous Library of Pergamum which housed many scrolls of art and science. The Library of Pergamum was only second in importance to the Library of Alexandria during the Hellenistic period.

The ship carrying the device also contained vases that were in the Rhodian style. One hypothesis is that the device was constructed at an academy founded by the Stoic philosopher Posidonius on the Greek island of Rhodes, which at the time was known as a center of astronomy and mechanical engineering; this hypothesis further suggests that the mechanism may have been designed by the astronomer Hipparchus, since it contains a lunar mechanism which uses Hipparchus's theory for the motion of the Moon. Hipparchus was thought to have worked from about 140 BC to 120 BC. Rhodes was a trading port at that time.[24]

The mechanism was discovered in a shipwreck off Point Glyphadia on the Greek island of Antikythera. The wreck had been found in October 1900 by a group of Greek sponge divers. They retrieved numerous artifacts, including bronze and marble statues, pottery, glassware, jewelry, coins, and the mechanism itself, which were transferred to the National Museum of Archaeology in Athens for storage and analysis. The mechanism itself went unnoticed for 2 years: it was a lump of corroded bronze and wood and the museum staff had many other pieces with which to busy themselves.[24] 

On 17May1902,archaeologist Valerios Stais was examining the finds and noticed that one of the pieces of rock had a gear wheel embedded in it. Stais initially believed it was an astronomical clock, but most scholars considered the device to be prochronistic, too complex to have been constructed during the same period as the other pieces that had been discovered. Investigations into the object were soon dropped until Derek J. de Solla Price became interested in it in 1951.[25] In 1971, both Price and a Greek nuclear physicist named Charalampos Karakalos made X-ray and gamma-ray images of the 82 fragments. Price published an extensive 70-page paper on their findings in 1974.[24] It is not known how it came to be on the cargo ship, but it has been suggested that it was being taken to Rome, together with other treasure looted from the island, to support atriumphal parade being staged by Julius Caesar.[26]

Cardiff University professor Michael Edmunds, who led a 2006 study of the mechanism, described the device as "just extraordinary, the only thing of its kind", and said that its astronomy was "exactly right". He regarded the Antikythera mechanism as "more valuable than the Mona Lisa".[21][27]
Faces[edit]


Computer-generated front panel of the Freeth model.

On the front of the mechanism, there is one dial with two confirmed pointers, but, due to references on the inscriptions, there might have been as many as eight pointers: one for the day of the year and the rest representing the orbital positions for Mercury, Venus, Sun, Mars, Jupiter, Saturn and the Moon; although no fragments have been found to confirm more than the sun and moon. It has been confirmed that the pointer for the moon also rotates on its axis to show its phase along with its position, although there is no direct evidence about whether the Sun position pointer would have been separated from a date pointer, or whether any planetary positions might have been displayed.[22]
Front face[edit]

The front dial has two concentric circular scales. The outer ring is marked off with the days of the 365-day Egyptian calendar, or the Sothic year, based on the Sothic cycle. On the inner ring, there is a second dial marked with the Greek signs of theZodiac and divided into degrees. The calendar dial can be moved to compensate for the effect of the extra quarter day in the solar year by turning the scale backwards one day every four years. A 3651⁄4-day year was used in the Callippic cycleabout 330 BC and in the Decree of Canopus in 238 BC, but that is not reflected in the dials. The following months are inscribed, in Greek letters, on the outer ring

Finally, the front face includes a parapegma, an inscripted precursor of the modern day almanac, which was used to mark the rising and setting of specific stars. The inscription, to the extent that it has been decoded into Greek characters, is displayed here: [2]. Each star is thought to be identified by Greek characters which cross-reference details inscribed on the mechanism.

Computer-generated back panel
In July 2008, scientists reported new findings in the journal Nature showing that the mechanism tracked the Metonic calendar, predicted solar eclipses, and calculated the timing of the Ancient Olympic Games.[32] Inscriptions on the instrument closely match the names of the months on calendars from Illyria and Epirus in northwestern Greece and with the island of Corfu.[33][34]

On the back of the mechanism, there are five dials: the Metonic, the Olympiad, the Callippic, the Saros and the Exeligmos. The Metonic Dial is the main upper dial. It is a 19-year calendar with a total of 235 months. Each month is written over two or three lines within one of the 235 cells spread over a spiral with five turnings. The Corinthian months are:

The Olympiad dial is the right secondary upper dial. The dial is divided into four sectors, each of which is inscribed with a year number and the name of two Panhellenic Games: the "crown" games of Isthmia, Olympia, Nemea, and Pythia; and two lesser games: Naa (held at Dodona) and another games which has not yet been deciphered.[35

The Callippic dial is the left secondary upper dial, which follows a 76-year cycle, quadrupling the Metonic dial.

The Saros dial is the main lower dial. It is an 18-year calendar with a total of 223 lunar months. Each month is represented by one of the 223 cells spread over a spiral with four turnings. This dial predicts eclipses and the predictions are shown in the relevant months as glyphs, which indicate lunar and solar eclipses and their predicted times of day. There are 51 glyphs, specifying 38 lunar and 27 solar eclipses. The glyph times are still incomplete. Beneath each glyph is an index letter.

The mechanism is remarkable for the level of miniaturisation and the complexity of its parts, which is comparable to that of 14th-century astronomical clocks. It has at least 30 gears, although Michael Wright has suggested that the Greeks of this period were capable of implementing a system with many more gears.[citation needed] There is much debate that the mechanism may have had indicators for all five of the planets known to the ancient Greeks. No gearing for such a planetary display survives and all gears are accounted for, with the exception of one 63 toothed gear (r1) otherwise unaccounted for in fragment D.

The purpose of the front face was to position astronomical bodies with respect to the celestial sphere along the ecliptic, in reference to the observer's position on the Earth. 

The gear teeth were in the form of equilateral triangles with an average circular pitch of 1.6 mm, an average wheel thickness of 1.4 mm and an average air gap between gears of 1.2 mm. They were probably created from a blank bronze round using hand tools; this is evident because they are not all divided very evenly.[31] Due to advances in imaging and X-ray technology it is now possible to know the precise number of teeth and size of the gears within the located fragments. Thus the basic operation of the device is no longer a mystery and has been accurately replicated. The major unknown now regards the presence and nature of any planet indicators.

Speculation about the mechanism's purpose[edit]

It is thought that the purpose of this device was to predict lunar and solar eclipses based on Babylonian arithmetic progression cycles. The inscriptions on the device also support suggestions of mechanical display of planetary positions.[43]

Derek J. de Solla Price suggested that the mechanism might have been on public display, possibly in a museum or public hall in Rhodes. The island was known for its displays of mechanical engineering, particularly automata, which apparently were a specialty of the Rhodians. Pindar, one of the nine lyric poets of ancient Greece, said this of Rhodes:
The animated figures stand
Adorning every public street
And seem to breathe in stone, or
Move their marble feet.
—Pindar (trans. Rev. C. A. Wheelwright - 1830), Seventh Olympic Ode (95)

Arguments against the device having been on public display include the following:
The device is rather small, indicating that the designer was aiming for compactness and, as a result, the size of the front and back dials is unsuitable for public display. A simple comparison with the size of the Tower of the Winds in Athens would suggest that the Antikythera mechanism manufacturer designed the device for mobility rather than public display in a fixed location.

The mechanism had door plates that contained at least 2,000 characters, forming what members of the Antikythera mechanism research project often refer to as an instruction manual. The attachment of this manual to the mechanism itself implies ease of transport and personal use.

The existence of this "instruction manual" implies that the device was constructed by a scientist and mechanic for use by a non-expert traveler (the text has much information associated with well-known Mediterranean geographical locations).[citation needed][dubious – discuss]

The device is unlikely to have been intended for navigation use because:
Some data, such as eclipse predictions, are unnecessary for navigation.
Damp, salt-laden marine environments would quickly corrode the gears, rendering it useless.

The extent to which the mechanism has stirred interest in its contextual culture may be glimpsed from a preview booklet issued by a conference held in 2006.[44]
Similar devices in ancient literature[edit]

Cicero's De republica, a 1st-century BC philosophical dialogue, mentions two machines that some modern authors consider as some kind of planetarium or orrery, predicting the movements of the Sun, the Moon, and the five planets known at that time. They were both built by Archimedes and brought to Rome by the Roman general Marcus Claudius Marcellus after the death of Archimedes at the siege of Syracuse in 212 BC. Marcellus had great respect for Archimedes and one of these machines was the only item he kept from the siege (the second was offered to the temple of Virtus). The device was kept as a family heirloom, and Cicero has Philus (one of the participants in a conversation that Cicero imagined had taken place in a villa belonging to Scipio Aemilianus in the year 129 BC) saying that Gaius Sulpicius Gallus (consul with Marcellus' nephew in 166 BC, and credited by Pliny the Elder as the first Roman to have written a book explaining solar and lunar eclipses) gave both a "learned explanation" and a working demonstration of the device.

Pappus of Alexandria stated that Archimedes had written a now lost manuscript on the construction of these devices entitledOn Sphere-Making.[46][47] The surviving texts from the Library of Alexandria describe many of his creations, some even containing simple drawings. One such device is his odometer, the exact model later used by the Romans to place their mile markers (described by Vitruvius, Heron of Alexandria and in the time of Emperor Commodus).[48] The drawings in the text appeared functional, but attempts to build them as pictured had failed. When the gears pictured, which had square teeth, were replaced with gears of the type in the Antikythera mechanism, which were angled, the device was perfectly functional.[49] Whether this is an example of a device created by Archimedes and described by texts lost in the burning of the Library of Alexandria, or if it is a device based on his discoveries, or if it has anything to do with him at all, is debatable.

It is unlikely that any one of these machines was the Antikythera mechanism found in the shipwreck since both the devices fabricated by Archimedes and mentioned by Cicero were located in Rome at least 30 years later than the estimated date of the shipwreck, and the third device was almost certainly in the hands of Posidonius by that date. The scientists who have reconstructed the Antikythera mechanism also agree that it was too sophisticated to have been a unique device.

This evidence that the Antikythera mechanism was not unique adds support to the idea that there was an ancient Greek tradition of complex mechanical technology that was later, at least in part, transmitted to the Byzantine and Islamic worlds, where mechanical devices which were complex, albeit simpler than the Antikythera mechanism, were built during theMiddle Ages.[51] Fragments of a geared calendar attached to a sundial, from the 5th or 6th century Byzantine Empire, have been found; the calendar may have been used to assist in telling time.[52] In the Islamic world, Banū Mūsā's Kitab al-Hiyal, or Book of Ingenious Devices, was commissioned by the Caliph of Baghdad in the early 9th century AD. This text described over a hundred mechanical devices, some of which may date back to ancient Greek texts preserved inmonasteries. A geared calendar similar to the Byzantine device was described by the scientist al-Biruni around 1000, and a surviving 13th-century astrolabe also contains a similar clockwork device.[52] It is possible that this medieval technology may have been transmitted to Europe and contributed to the development of mechanical clocks there.[6]