thumb|[[Artefaktens mekaniske diagram.]]

thumb|250px|Antikythera-mekanismen, som den ser ud i dag.

'''Antikythera-mekanismen''' er en artefakt fra antikken på størrelse med en skotøjsæske, som man i lang tid ikke vidste hvad var. Den indeholder mere end 30 tandhjul og drejeskiver og den er i dag delt i tre hovedstykker og nogle mindre fragmenter. Herudover er den fyldt med græske inskriptioner.

Den blev fundet i Antikythera-skibsvraget ud for den Græske ø Antikythera mellem Kythera og Kreta.  

Skibsvraget blev opdaget i år 1900 i en dybde på omkring 43&nbsp;m og mange statuer og andre ting blev hentet op af svampedykkere. Skibet er dateret til at være sunket 87 f.Kr.-80 f.Kr.. Den 17. maj 1902 opdagede arkæologen Spyridon Stais at et af stenstykkerne havde tandhjul indlejret.

Mekanismen er en af de ældste kendte Den Sydpegende Hestevogn. I Antikythera-mekanismen er et ur lavet i det 18. århundrede.
<ref>[http://www.nature.com/nature/journal/v444/n7119/full/444534a.html Nature 444, 534-538 (30 November 2006): In search of lost time] Citat: "...How can the capacity to build a machine so magnificent have passed through history with no obvious effects?...three-dimensional reconstructions of the fragments have turned up a new aspect of the mechanism that is both stunningly clever and directly linked to work by Hipparchus..."</ref>  
Den er lavet af bronze og monteret i en træramme. Den har undret videnskabs- og teknologi-historikere siden dens opdagelse.

Den mest accepterede teori for mekanismens funktion er, at den viser hvordan mange af vores ægyptiske kalender månedsnavne kan aflæses. På det tidspunkt kendte man mindst 5 planeter, solen og månen. Mekanismen blev sandsynligvis drevet af et håndsving.
 
Den originale mekanisme er udstillet i ''National Archaeological Museum in Athens'' i Bronze samlingen sammen med en replikation. En anden replikation er i ''American Computer Museum'' i Bozeman, Montana.

===Rekonstruktioner===
thumb|right|Moderne rekonstruktion.
Mekanismen er blevet rekonstrueret talrige gange og viser at den faktisk virkede.

Rekonstruktionerne underbygger nævnelsen af sådanne ting i antikkens tekster. Cicero skrev i det 1. århundrede f.Kr. at "vores ven Poseidonios fornylig har konstrueret et instrument, som ved hver omdrejning, kan vise solens, månens og de 5 planeters bevægelse". Sådanne apparater nævnes også andre steder og dette støtter formodningen om at der i antikken var en græsk tradition for kompleks mekanisk teknologi, som var blevet overleveret via den arabiske verden.

right|thumb|280px|The Antikythera mechanism (main fragment).

The '''Antikythera mechanism''' is an ancient mechanical mechanical computer"<ref>"[http://www.antikythera-mechanism.gr/project/general/the-project.html The Antikythera Mechanism Research Project]", The Antikythera Mechanism Research Project. Retrieved 2007-07-01</ref><ref name="Washington Post">[http://www.washingtonpost.com/wp-dyn/content/article/2006/11/30/AR2006113001303.html Washington Post] Quote: ''Imagine tossing a top-notch laptop into the sea, leaving scientists from a foreign culture to scratch their heads over its corroded remains centuries later. A Roman shipmaster inadvertently did something just like it 2,000 years ago off southern Greece, experts said late Thursday.''</ref>) designed to calculate astronomical positions. It was discovered in the Greek island of Antikythera, between Kythera and Crete, in 1900. Subsequent investigation, particularly in 2006, dated it to about 150&ndash;100 BC, and hypothesised that it was on board a ship that sank en route from the Greek island of Rhodes to Rome, perhaps as part of an official loot. Technological artifacts of similar complexity did not reappear until a thousand years later.<ref>"Planetary gears", ''Nature'' '''444''' (7119).</ref>

==Discovery==
Sometime before April 1900,  a Greek sponge diver named Elias Stadiatos discovered the wreck of an ancient large cargo ship off Antikythera island at a depth of 42 m (138 ft) to 60 m (200 ft). Sponge divers retrieved several statues (including the famous Mercury), and eclipses.

Jacques-Yves Cousteau visited the wreck for the last time in 1978,<ref>{{cite book
 | author=Lazos, Christos
 |date=1994
 | title= The Antikythera Computer (<small>Ο ΥΠΟΛΟΓΙΣΤΗΣ ΤΩΝ ΑΝΤΙΚΥΘΗΡΩΝ</small>),
 | publisher= ΑΙΟΛΟΣ PUBLICATIONS GR
 }}</ref> 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." and added: "in terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."<ref>{{cite news 
  | last = Johnston
  | first = Ian
  | title = Device that let Greeks decode solar system
  | publisher = ''The Scotsman''
  | date = 2006-11-30
  | url = http://news.scotsman.com/international.cfm?id=1774262006
  | accessdate = 2007-06-26 
  }}</ref><ref name="Guardian">[http://www.guardian.co.uk/science/2006/nov/30/uknews The Guardian] Mysteries of computer from 65BC are solved Quote: ''This device is extraordinary, the only thing of its kind," said Professor Edmunds. "The astronomy is exactly right ... in terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."'' and ''One of the remaining mysteries is why the Greek technology invented for the machine seemed to disappear.''</ref>

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 and the Children's Museum of Manhattan in New York.

==Origins==
The mechanism is the oldest known complex scientific instrument. It has several accurate scales, and is essentially an analog computer made with gears. It is based on theories of astronomy and mathematics developed by Persian and Egyptian astronomers. Based on the shape of the Egyptian letters used in the manual of the instrument, it is estimated that it was constructed around 150 to 100 BC. The circumstances under which it came to be on the cargo ship are unclear. The ship is estimated to have sunk between 80 to 60 BC and was a Roman or Greek ship with cargo for Rome, perhaps part of official loot. It contained more than 100 statues similar to the ones the Romans took to Italy after their conquest of Greece. Consensus among scholars is that the mechanism itself was made in Greece.<ref name="Guardian"/> All the instructions of the mechanism are written in Greek. 

One hypothesis is that the device was constructed at an academy founded by the ancient triumphal parade being staged by Julius Caesar.<ref>{{cite web
  | url=http://www.iol.co.za/index.php?set_id=1&click_id=588&art_id=vn20060606235853817C767629
  | title=Ancient 'computer' starts to yield secrets
  | accessdate=2007-03-23 }}</ref>

As the new finds of the Antikythera Mechanism Research Project suggest that it was made around 150 to 100 BC, well before the time of Posidonius, it is possible that the great astronomer Hipparchus is behind the genius engineer who constructed it. Hipparchus was at that time the most important astronomer and worked for a long period in Rhodes, Greece. The Mechanism contains a lunar mechanism which uses Hipparchus' theory for the motion of the Moon and this also suggests strong ties of the Mechanism to Hipparchus.

==Function==
frame|Schematic of the artifact's mechanism

The device is remarkable for the level of miniaturization and complexity of its parts, which is comparable to that of 18th 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. It is possible that the mechanism is based on heliocentric principles, rather than the then-dominant geocentric view espoused by Aristotle and others. The heliocentric view proposed by Aristarchus of Samos (310 BC - c. 230 BC) did not receive widespread recognition, but provides for the possibility of the existence of such a system at this time.

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 adjust, to compensate for the effect of the extra quarter day in the year (there are almost 365.25 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 B.C., up to a century after the device was said to have been built (and it 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, except for one unaccounted gear, for such planetary mechanisms survives.

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 dial contains a smaller subsidiary dial which displays the 76 year Callippic cycle. (There are 4 Metonic cycles within 1 Callippic cycle.) Both of these cycles are important in fixing calendars. 

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.)

==Speculation about its purpose==
While a century of research is finally answering the question of what the mechanism did, we are actually no nearer to answering the question of what it was for. There are numerous suggestions, any of which could be right. In order to understand the significance of this device at the period of its manufacture (c. 150 B.C.) one should be aware of the known scientific and cultural status at that period and take into account that:
# The law of gravity was not discovered, so the reason why the heavenly bodies moved was not understood.
# The theory of planetary motion was not complete.
# The only means to transmit knowledge was either speech or hand-written manuscripts.

There was a huge scientific and cultural gap between the very few educated elite that understood basic rules of solar, lunar and planetary motion and the common people who were ignorant about those things. Many ancient references from Cicero, Pliny, Plato, Seneca, Ptolemy and Aristotle ''et al'' indicate that common people viewed solar and lunar eclipses as superstitious events, linked with fear: ".. easy for the ignorant to imagine that all has become confusion and doom"<ref>{{cite web
  | url=http://www.columbia.edu/~rcc20/ma.pdf
  | title=Cultural History of the Lunar and Solar Eclipse in the Early Roman Empire
  | accessdate=2007-10-08
  | author=Richard C. Carrier
  }}</ref> . 

Practical uses of this device have been said also to include the following:
* Astrology was commonly practiced in the ancient world. In order to create an astrological chart, the configuration of the heavens at a particular point of time is needed. It can be very difficult and time-consuming to work this out by hand, and a mechanism such as this would have made an astrologer's work much easier.
* Setting the dates of religious festivals connected with astronomical events.
* Adjusting calendars, which were based on lunar cycles as well as the solar year.

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 specialty 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:
:a) The device is rather small, indicating that the designer was aiming for compactness (it has been compared to a modern laptop computer) 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 rather the mobility of this device, than the public display of it in a fixed place (such as a university, a temple, a museum or public hall).
:b) The mechanism had door plates attached to it that contain at least 2000 characters, forming what members of the Antikythera mechanism research project often refer to as an instruction manual of the mechanism. The neat attachment of this manual on the mechanism itself implies ease of transport and personal use.
:c) 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 traveller (the text gives a lot of information associated with well known geographical locations of the Mediterranean area).

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.

==Similar devices in ancient literature==

siege of Syracuse in 212 BC. Marcellus had a high respect for Archimedes and this was the only item he kept from the siege. The device was kept as a family heirloom, and Cicero was shown it by Gallus about 150 years later. Gallus gave a 'learned explanation' of it and demonstrated it for Cicero.
:''hanc sphaeram Gallus cum moveret, fiebat ut soli luna totidem conversionibus in aere illo quot diebus in ipso caelo succederet, ex quo et in [caelo] sphaera solis fieret eadem illa defectio, et incideret luna tum in eam metam quae esset umbra terrae, cum sol e regione''
:When Gallus moved the globe, it happened that the Moon followed the Sun by as many turns on that bronze [contrivance] as in the Earth itself, from which also in the sky the Sun's globe became [to have] that same eclipse, and the Moon came then to that position which was [its] shadow [on] the Earth, when the Sun was in line.<ref>{{cite web
  | url=http://www.thelatinlibrary.com/cicero/repub1.shtml#21
  | title=M. TVLLI CICERONIS DE RE PVBLICA LIBER PRIMVS
  | accessdate=2007-03-23
  }}</ref> 

 Science/Nature | Ancient Moon 'computer' revisited<!-- Bot generated title -->]</ref>  The surviving texts from the [[Library of Alexandria describe many of his creations, some even containing simple blueprints. One such device is his odometer, the exact model later used by the Romans to place their mile markers (described by Heron of Alexandria and in the time of Emperor Commodus).<ref name="needham volume 4 part 2 285">Needham, Volume 4, Part 2, 285.</ref> The blueprints 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. 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.

If Cicero's account is correct (and there is reason to doubt it) then this technology existed as early as the 3rd century BC. Archimedes' device is also mentioned by later Roman era writers such as Lactantius (''Divinarum Institutionum Libri VII''), Claudian (''In sphaeram Archimedes''), and Proclus (''Commentary on the first book of Euclid's Elements of Geometry'') in the 4th and 5th centuries.

Cicero also says that another such device was built 'recently' by his friend Posidonius, "... each one of the revolutions of which brings about the same movement in the Sun and Moon and five wandering stars [planets] as is brought about each day and night in the heavens..."<ref>{{cite web
  | url=http://www.thelatinlibrary.com/cicero/nd2.shtml#88
  | title=Cicero, De Natura Deorum II.88 (or 33-34)
  | accessdate=2007-03-23
  }}</ref>

It is unlikely that either of these machines were the Antikythera mechanism found in the shipwreck, because both the devices mentioned by Cicero were located in Rome at least 50 years later than the estimated date of the shipwreck. So we know of three such devices. The modern scientists who have reconstructed the Antikythera mechanism also agree that it was too sophisticated to have been a one-off device.

It is probable that the Antikythera mechanism was not unique, as shown by Cicero's references to such mechanisms. This adds support to the idea that there was an ancient Greek tradition of complex mechanical technology that was later transmitted to the Islamic world, where similarly complex mechanical devices were built by Muslim engineers and astronomers during the Kitab al-Hiyal'' (''Book of Ingenious Devices''), commissioned by the Greek texts preserved in monasteries. Similarly complex astronomical instruments were constructed by Muslim astronomers from the 11th century.<ref>"In search of lost time" and "Archaeology: High tech from Ancient Greece", ''Nature'' '''444''' (7119).</ref> Such knowledge could have yielded to or been integrated with European clockmaking and medieval cranes.

==Investigations and reconstructions==
right|thumb|150px|Reconstruction of the Antikythera mechanism in the National Archaeological Museum, Athens (made by Robert J. Deroski, based on [[Derek J. de Solla Price model).]]

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 mathematician from Greece.

===Derek J. de Solla Price===
Following decades of work cleaning the device, in 1951 British science historian Derek J. de Solla Price undertook systematic investigation of the mechanism. 