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The mysterious Antikythera Mechanism – how does 14th century technology exist in a 2,000 year old device?


Antikythera Mechanism


Discovered on a shipwreck off the coast of Antikythera in 1901, some have called the Antikythera Mechanism the first analog computer; others the first mechanical computing device. Consisting of a sophisticated, intricate system of bronze gears, wheels, and differential cogs, the technology used to construct the device resembles that of 18th century clocks. Gearing of this complexity was not known to exist until no earlier than 1600 A.D. when mechanical astronomical clocks began to be built in Western Europe. You can imagine the shockwave that rocked the scientific community when the device was conclusively dated to the second century B.C., thousands of years earlier than it should have been possible to construct. It is still unknown who constructed the instrument 2,000 years ago, how the device was constructed, or how the technology used to build the Antikythera Mechanism remained lost for thousands of years.

The discovery and importance of the find

The found fragments of the Antikythera MechanismIn 1901, remnants of a broken wooden and bronze instrument containing more than 37 gears (of which 30 were found) were discovered about 164 feet underwater by sponge divers exploring a shipwreck off the island of Antikythera, a busy trade route between southern mainland Greece and Crete. The device, along with bronze and marble statues, pottery, glassware, jewelry, and coins, was placed in the National Museum of Archaeology in Athens where it remained unnoticed for two years. In 1902, an archaeologist was examining the puzzling metal scraps when he noticed what appeared to be a gear embedded in the rock-encrusted material.  This could not be.  Coins found on the wreck were dated 85 B.C. while the first clockwork devices appeared more than a thousand years later in Western Europe. Too complex to have been constructed during the same period as the other pieces that had been discovered, the archaeologist was puzzled, although apparently not intrigued, and moved on to other pieces of the archaeological find. The significance of the discovery was not truly understood until almost a century later.

In 1951, science historian and Smithsonian consultant Derek J. de Solla Price became fascinated with the device. 20 years later (in 1971), Price, with the aid of a Greek physicist, shot X-ray images of the 82 surviving fragments. X-ray analysis revealed that the mechanism was housed in a wooden box measuring 340 by 180 mm and only 90 mm thick, with a front and a back door that when opened, allowed access to a complex system of wheels, cogs, and gears. The largest gear was found to be 140 mm in diameter and the smallest gear measuring a mere 45 mm in diameter, a remarkable accomplishment even for clock makers thousands of years later. The average thickness of the gear wheels was measured and found to be 1.4 mm with an air gap between gears measuring a thread-thick 1.2 mm. Researchers were stunned when they found inscriptions on the device that indicated it had been utilized as far back as 150 B.C. Their 70-page paper documenting their findings rocked the archaeological world.

A proposed reconstruction of the Antikythera MechanismAccording to the Antikythera Mechanism Research Project:

“The mechanism has 3 main dials, one on the front, and two on the back. The front dial is marked with the divisions of the Egyptian calendar, or the Sothic year. Inside this there is a second dial marked with the Greek signs of the Zodiac. This second dial is movable dial so that it can be adjusted to compensate for leap years.

The front dial probably carried three hands, one showing the date, and two others showing the positions of the Sun and the Moon. The Moon indicator is ingeniously adjusted to show the fist anomaly of the Moon’s orbit. It is reasonable to suppose the Sun indicator had a similar adjustment. The front dial also includes a second mechanism with a spherical model of the Moon that displays its 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 the 5 planets known to the Greeks.

Finally the front dial includes a parapegma used to mark the rising and setting of specific stars. Each star is thought to be identified by Greek characters which cross references 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 eclipse cycle. It also has a smaller subsidiary dial which displays the 54 year Exeligmos cycle. (There are 3 Saros cycles, within 1 Exeligmos cycle.)”

Another proposed reconstruction of the Antikythera MechanismIn 2006, Professor Michael Edmunds of Cardiff University, led a new study of the Antikythera Mechanism. He described the importance of the archaeological find:

“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 … in terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa.”

Although we now know what the device did, we still do not know what the mechanism was used for. Detailed examination of the gears in the mechanism showed it was able to track astronomical movements with remarkable precision. The device is capable of following the movements of the moon through the Zodiac, predict eclipses, and even recreate the irregular orbit of the moon. Researchers now believe that it may also have predicted the positions of the planets (Greeks knew of five planets at the time).

The device worked by hand cranking a main dial to display a chosen date, causing the wheels and gears inside to display (via tabs on separate dials) the position of the sun, moon, and the five known planets at that time.  It is a mechanical and technical feat that would not be seen again until the fourteenth century in Europe with introduction of precision clocks.


After more careful examination of the mechanism, scientists were excited to discover inscriptions on the front and rear facings. Here is what we know about the inscriptions.

Front Face Inscriptions

A few of the following months are inscribed, in Greek letters, on the outer ring of the Front face of the Antikythera device:

  • Mecheir
  • Phamenoth
  • Pharmouthi
  • Pachon
  • Payni
  • Epeiph
  • Mesore
  • Epagomene
  • Thoth
  • Phaophi
  • Hathyr
  • Choiak
  • Tybi

Magnified view of Antikythera Mechanism inscriptionsIn addition, a few of the following Zodiac signs appear on the inner ring:

  1. ΚΡIOΣ (Aries)
  2. ΤΑΥΡΟΣ (Taurus)
  3. ΔIΔΥΜΟΙ (Gemini)
  4. ΚΑΡΚIΝΟΣ (Cancer)
  5. ΛEΩΝ (Leo)
  6. ΠΑΡΘEΝΟN (Virgo)
  7. ΧΗΛΑΙ (Scorpio’s Claw, i.e., Libra)
  8. ΣΚΟΡΠΙΟΣ (Scorpio)
  9. ΤΟΞΩΤΗΣ (Sagittarius)
  10. ΑIΓOΚΕΡΩΣ (Capricorn)
  11. YΔΡΟΧOΟΣ (Aquarius)
  12. IΧΘΕIΣ (Pisces)

Other inscriptions on the front face of the Antikythera Mechanism’s dial include:

  • {Κ} Evening
  • {Λ} The Hya{des se}t in the evening
  • Μ Taurus {be}gins to rise
  • {N} Vega rises in the evening
  • Θ {The Pleiad}es rise in the morning
  • Ο The Hyades rise in the morning
  • Π Gemini begins to rise
  • Ρ Altair rises in the evening
  • Σ Arcturus sets in the {morning}

Antikythera MechanismRear Face Inscriptions

On the back of the mechanism, an upper dial was found containing the inscription of the Corinthian months:

  1. ΦΟΙΝΙΚΑΙΟΣ (Phoinikaios)
  2. ΚΡΑΝΕΙΟΣ (Kraneios)
  3. ΛΑΝΟΤΡΟΠΙΟΣ (Lanotropios)
  4. ΜΑΧΑΝΕΥΣ (Machaneus)
  5. ΔΩΔΕΚΑΤΕΥΣ (Dodekateus)
  6. ΕΥΚΛΕΙΟΣ (Eukleios)
  7. ΑΡΤΕΜΙΣΙΟΣ (Artemisios)
  8. ΨΥΔΡΕΥΣ (Psydreus)
  9. ΓΑΜΕΙΛΙΟΣ (Gameilios)
  10. ΑΓΡΙΑΝΙΟΣ (Agrianios)
  11. ΠΑΝΑΜΟΣ (Panamos)
  12. ΑΠΕΛΛΑΙΟΣ (Apellaios)

Another rear facing dial contains numbered years, marking the iterations between leap years.

  1. ΙΣΘΜΙΑ, ΟΛΥΜΠΙΑ (corresponding to year 1)
  2. NEMEA, NAA (corresponding to year 2)
  3. ΙΣΘΜΙΑ, ΠΥΘΙΑ (corresponding to year 3)
  4. ΝΕΜΕΑ, undeciphered text (corresponding to year 4)

X-Ray image of the Antikythera MechanismOn the main lower dial are the partial remains of inscriptions spread over a spiral that researchers believe point to lunar cycles and solar eclipses. Some of the remaining letters include:

  • Σ = ΣΕΛΗΝΗ (Moon)
  • Η = ΗΛΙΟΣ (Sun)
  • H\M = ΗΜΕΡΑΣ (of the day)
  • ω\ρ = ωρα (hour)
  • N\Y = ΝΥΚΤΟΣ (of the night)

On the “back door” of the box appears to be the “Instruction Manual”. On one of its fragments, it is written “76 years, 19 years” representing the Callippic and Metonic cycles. It also is inscribed with the number “223”, presumably for the Saros cycle. On another one of its fragments, it is written “on the spiral subdivisions 235”.

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.


It is not known where the device was headed when a storm blew the cargo ship against an underwater cliff off Antikythera’s Point Glyphadia but it has been theorized that it was loot taken from Antikythera that was being transported back to Greece to be included in a parade being staged in honor of Julius Caesar’s military successes. Researchers are baffled as to who could have constructed the device a millennium before the sophisticated technology was reinvented. To date it is the most elaborate mechanical device known from antiquity until the Middle Ages.

The Antikythera mechanism is currently on display at the National Archaeological Museum of Athens.

Update: 11/27/14 New analysis of the device suggests that the calendar function of the device began in 205 BC hinting that the Antikythera mechanism is even older than originally thought.  The most recent analysis of the inscriptions dated the mechanism from 150 to 100 BC but the new discovery of the “epoch date” 50-100 years earlier has stunned scientists.  This new finding suggests that the mechanism’s eclipse prediction strategy was not based on Greek trigonometry, which did not exist at the time, but on Babylonian arithmetical methods borrowed by the Greeks.

Sources: The Antikythera Mechanism Research Project, National Archaeological Museum of Athens, BBC, The Guardian, Wikipedia, MSNBC,, Discovery Magazine