Antikythera Mechanism

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. A number of individuals and groups have been instrumental in advancing the knowledge and understanding of the mechanism including: Derek J. de Solla Price (with Charalampos Karakalos); Allan George Bromley (with Frank Percival, Michael Wright and Bernard Gardner); Michael Wright; The Antikythera Mechanism Research Project and Dionysios Kriaris, a Greek mathematician. Discovered in 1900–1901 by sponge divers from a shipwreck of ca 60 BCE off Antikythera island, this bronze and wood device (a box ca 10 by 20 by 30 cm) containing triangular-toothed gears was reconstructed by Price as a calendar computer for predicting lunar and (possible) solar eclipses; a crank was turned to drive the gears from day to day. The device displays the Babylonian “Saros” cycle, the 235 months of the 19-year cycle of Meton, and the 76 years of the cycle of Kallippos. Enough of the text survives to show that a parapegma was inscribed on the bronze front of the box. Recent re-examination by Freeth at al. has recovered further text, containing the word sphairion, which Keyser argued was the name for such a device. They also establish that the gearing was based on Hipparkhos / Hipparchus’ model of lunar motion.
It contains many gears, and is sometimes called the first known analog computer, although its flawless manufacturing suggests that it had a number of predecessors which have not yet been discovered. It appears to be constructed upon theories of astronomy and mathematics developed by Greek astronomers and it is estimated that it was made around 150 to 100 BC. The mechanism has three main dials, one on the front, and two on the back. The front dial has two concentric 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. Inside this, there is a second dial marked with the Greek signs of the Zodiac and divided into degrees.

Schematic of the Artifact's Mechanism

The calendar dial can be moved to compensate for the effect of the extra quarter day in the year (there are 365.2422 days per year) by turning the scale backwards one day every four years. Note that the Julian calendar, the first calendar of the region to contain leap years, was not introduced until about 46 BC, up to a century after the device was said to have been built (and the leap year was implemented with errors until the early first century). The front dial probably carried at least three hands, one showing the date, and two others showing the positions of the Sun and the Moon.

The Moon indicator is adjusted to show the first anomaly of the Moon's orbit. It is reasonable to suppose the Sun indicator had a similar adjustment, but any gearing for this mechanism (if it existed) has been lost. The front dial also includes a second mechanism with a spherical model of the Moon that displays the lunar phase. There is reference in the inscriptions for the planets Mars and Venus, and it would have certainly been within the capabilities of the maker of this mechanism to include gearing to show their positions.

There is some speculation that the mechanism may have had indicators for all the five planets known to the Greeks. None of the gearing for such planetary mechanisms survives, except for one gear otherwise unaccounted for. Finally, the front dial includes a parapegma, a precursor to the modern day Almanac, which was used to mark the rising and setting of specific stars. Each star is thought to be identified by Greek characters which cross reference details inscribed on the mechanism. The upper back dial is in the form of a spiral, with 47 divisions per turn, displaying the 235 months of the 19 year Metonic cycle. This cycle is important in fixing calendars. The lower back dial is also in the form of a spiral, with 225 divisions showing the Saros cycle; it also has a smaller subsidiary dial which displays the 54 year "Triple Saros" or "Exeligmos" cycle. (The Saros cycle, discovered by the Chaldeans, is a period of approximately 18 years 11 days 8 hours—the length of time between occurrences of a particular eclipse.)

The designers did not need a theory of planetary motion to compute planetary positions. The Babylonian 'System B', the mathematical formulae which calculated planetary positions, and which the Greeks inherited, was devised by 260 BC, and perhaps as early as 500 BC. There was a huge scientific and cultural gap between the very few educated elite who understood basic rules of solar, lunar and planetary motion and the common people who were ignorant of those things. Many ancient references from Cicero, Pliny, Plato, Seneca, Ptolemy, Aristotle et al. indicate that common people viewed solar and lunar eclipses as supernatural events, linked with fear: "... easy for the ignorant to imagine that all has become confusion and doom".

The device is unlikely to have been intended for navigation use because:
a) Some data, such as eclipse predictions, are unnecessary for navigation.
b) The harsh environment of the sea would corrode the gears in a short period of time, rendering it useless.

On 30 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. 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. 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, and that perhaps the astronomer Hipparchus was the engineer who designed it since it contains a lunar mechanism which uses Hipparchus' theory for the motion of the Moon.

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. However, the most recent findings of The Antikythera Mechanism Research Project, as published in the July 30, 2008, edition of Nature also suggest that the concept for the mechanism originated in the colonies of Corinth, which might imply a connection with Archimedes. The circumstances under which it came to be on the cargo ship are unknown. Consensus among scholars is that the mechanism itself was made in Greece. All the instructions of the mechanism are written in Greek.

(Sources : Encyclopedia of Ancient Natural Scientists : “The Greek Tradition and Its Many Heirs” Edited by Paul Keyser & Georgia Irby-Massie; and 
 
 
Antikythera Mechanism Antikythera Mechanism Reviewed by Tripzibit on 07:04 Rating: 5

2 comments:

  1. wahh ini gear ya... dah tua bgt ya ^^

    ReplyDelete
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