Atlantis Arisen

Maps, Explorers & Adventurers => Ancient Instruments and Devices => Topic started by: Trinity on June 17, 2010, 03:14:44 pm

Title: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:14:44 pm
Antikythera mechanism


Fragment principal de la machine d'Anticythère. Le mécanisme consiste en un système complexe de 32 roues et plaques portant des inscriptions relatives aux signes du zodiaque et aux mois. L'étude des fragments suggère qu'il s'agissait d'une sorte d'astrolabe utilisée pour la navigation maritime. L'interprétation désormais généralement acceptée remonte aux études du professeur Derek de Solla Price, qui fut le premier à suggérer que le mécanisme est une machine à calculer le calendrier solaire et lunaire, c'est-à-dire une machine ingénieuse pour déterminer le temps sur la base des mouvements du soleil et de la lune, leur relation (éclipses) et les mouvements des autres étoiles et des planètes connues à cette époque. Le mécanisme fut probablement construit par un mécanicien ingénieux de l'école de Poséidonios à Rhodes. Cicéron, qui visita l'île en 79/78 a. C. rapporte que de tels engins étaient en effet conçus par le philosophe stoïcien Poséidonios d'Apamée. La conception du mécanisme d'Anticythère paraît suivre la tradition du planétarium d'Archimède, et peut être reliée aux cadrans solaires. Son mode opératoire est basé sur l'utilisation de roues dentées. La machine est datée de 89 a. C. environ et provient de l'épave trouvée au large de l'île d'Anticythère. Musée archéologique national, Athènes, n°15987.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:15:59 pm
The Antikythera mechanism (pronounced /ˌæntɪkɪˈθɪərə/ AN-ti-ki-THEER-ə), is conjectured to be an ancient mechanical computer[1][2] designed to calculate astronomical positions. It was recovered in 1900–01 from the Antikythera wreck,[3] but its complexity and significance were not understood until decades later. It is now thought to have been built about 150–100 BC. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanical astronomical clocks appeared in Europe.[4]

Jacques-Yves Cousteau visited the wreck for the last time in 1978,[5] but found no more remains of the Antikythera Mechanism. Professor Michael Edmunds of Cardiff University who led the most recent 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 terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."[6][7]

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. Other reconstructions are on display at the American Computer Museum in Bozeman, Montana, the Children's Museum of Manhattan in New York, and in Kassel, Germany.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:16:28 pm
The mechanism is the oldest known complex scientific calculator. It contains many gears, and is sometimes called the first known analog computer,[8] although its flawless manufacturing suggests that it may have had a number of predecessors during the Hellenistic Period which have not yet been discovered.[9] It appears to be constructed upon theories of astronomy and mathematics developed by Greek astronomers and it is estimated that it was made around 150-100 BC. 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's 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.[10] 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 the Greek speaking world.[7] All the instructions of the mechanism are written in Greek.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:17:25 pm

Schematic of the artifact's mechanism.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:17:59 pm

The device is remarkable for the level of miniaturization and for the complexity of its parts, which is comparable to that of 17th century clocks. It has over 30 gears, although Michael Wright (see below) has suggested as many as 72 gears, with teeth formed through equilateral triangles. When a date was 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. Since the purpose was to position astronomical bodies with respect to the celestial sphere, with reference to the observer's position on the surface of the Earth, the device was based on the geocentric model.[11]

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. The calendar dial can be moved to compensate for the effect of the extra quarter day in the solar 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.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:18:10 pm
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.

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:18:24 pm
The lower back dial is also in the form of a spiral, with 223 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 Antikythera Mechanism Research Project, with experts from Britain, Greece and the United States, detected in July 2008 the word "Olympia" on a bronze dial thought to display the 76 year Callippic cycle, as well as the names of other games in ancient Greece, and probably used to track dates of the ancient Olympic games. According to BBC news:

"The four sectors of the dial are inscribed with a year number and two Panhellenic Games: the 'crown' games of Isthmia, Olympia, Nemea, and Pythia; and two lesser games: Naa (held at Dodona) and a second game which has not yet been deciphered."[12]

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:19:33 pm
Speculation about its purpose
Derek J. de Solla Price suggested that it 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 speciality of the Rhodians. Pindar, one of the nine lyric poets of ancient Greece, said this of Rhodes in his seventh Olympic Ode:
"The animated figures stand
Adorning every public street
And seem to breathe in stone, or
Move their marble feet."
Arguments against it being on public display include:
1.   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 size of the Tower of the Winds in Athens could give us a hint to suggest that the aim of the Antikythera mechanism manufacturer was the mobility of this device rather than its public display in a fixed place (such as a temple, museum or public hall).
2.   The mechanism had door plates attached to it that contain at least 2,000 characters, forming what members of the Antikythera mechanism research project often refer to as an instruction manual for the mechanism. The neat attachment of this manual to the mechanism itself implies ease of transport and personal use.
3.   The existence of this "instruction manual" implies that the device was constructed by an expert scientist and mechanic in order to be used by a non-expert traveler (the text gives a lot of information associated with well known geographical locations of the Mediterranean area).

Title: Re: Antikythera mechanism
Post by: Trinity on June 17, 2010, 03:20:05 pm
The device is unlikely to have been intended for navigation use because:
1.   Some data, such as eclipse predictions, are unnecessary for navigation.
2.   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.[13] 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.[14][15]