Last modified on 22 July 2014, at 20:32

Antikythera mechanism

For the BT song "The Antikythera Mechanism", see This Binary Universe.
The Antikythera mechanism (Fragment A – front)
The Antikythera mechanism (Fragment A – back)

The Antikythera mechanism (/ˌæntɨkɨˈθɪərə/ ANT-i-ki-THEER or /ˌæntɨˈkɪθərə/ ANT-i-KITH-ə-rə) is an ancient analog computer[1][2][3][4] designed to predict astronomical positions and eclipses. It was recovered in 1900–01 from the Antikythera wreck, a shipwreck off the Greek island of Antikythera.[5] The instrument has been designed and constructed by Greek scientists and dated between 150 to 100 BC.[6] 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.[7]

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.[8][9]

Since their discovery the fragments of the Antikythera mechanism are kept at the National Archaeological Museum of Athens.

Origins and discoveryEdit

This machine has the oldest known complex gear mechanism and is sometimes called the first known analog computer,[10][11][12][13][14][15][16][17] although the quality of its manufacture suggests that it had undiscovered predecessors[18] 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.[5] 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, 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.[21] 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.[22] 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.[7]

The mechanism was discovered in a shipwreck off Point Glyphadia on the Greek island of Antikythera. The wreck had been found in April 1900 by a group of Greek sponge divers. They retrieved numerous artifacts, including bronze and marble statues, pottery, unique 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 two years: it was a lump of corroded bronze and wood and the museum staff had many other pieces with which to busy themselves.[7] On 17 May 1902, 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.[23] 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.[7] 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 a triumphal parade being staged by Julius Caesar.[24]

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".[25][26]

DescriptionEdit

[6][27][28]

The original mechanism apparently came out of the Mediterranean as a single encrusted piece. Soon afterwards it fractured into three major pieces. Other small pieces have broken off in the interim from cleaning and handling,[29] and still others were found on the sea floor by the Cousteau expedition. Other fragments may still be in storage, undiscovered since their initial recovery; Fragment F came to light in that way in 2005.

Of the 82 known fragments, seven are mechanically significant and contain the majority of the mechanism and inscriptions. There are also 16 smaller parts that contain fractional and incomplete inscriptions.

The seven major fragments are listed below:

Fragment Size [mm] Weight [g] Gears Inscriptions
A 180 × 150 369.1 27 Yes
B 125 × 60 99.4 1 Yes
C 120 × 110 63.8 1 Yes
D 45 × 35 15.0 1
E 60 × 35 22.1 Yes
F 90 × 80 86.2 Yes
G 125 × 110 31.7 Yes

Major fragmentsEdit

Fragment A can be seen as the main fragment and contains the majority of the known mechanism. Clearly visible on the front is the large b1 gear, and under closer inspection further gears behind said gear (parts of the l, m, c and d trains are clearly visible as gears to the naked eye). The crank mechanism socket and the side mounted gear that meshes with b1 is on Fragment A. The back of the fragment contains the rearmost e and k gears for synthesis of the moon anomaly, noticeable also is the pin and slot mechanism of the k train. It is noticed from detailed scans of the fragment that all gears are very closely packed and have sustained damage and displacement due to their years in the sea. The fragment is approximately 30 mm thick at its thickest point.

Fragment A also contains divisions of the upper left quarter of the Saros spiral and 14 inscriptions from said spiral. The fragment also contains inscriptions for the Exeligmos dial and visible on the back surface the remnants of the dial face itself. Finally, this fragment contains some back door inscriptions.

Fragment B contains approximately the bottom right third of the Metonic spiral and inscriptions of both the spiral and back door of the mechanism. The Metonic scale would have consisted of 235 cells of which 49 have been deciphered from fragment B either in whole or partially. The rest so far are assumed from knowledge of the Metonic cycle itself. This fragment also contains a single gear (o1) used in the Olympic train.

Fragment C contains parts of the upper right of the front dial face showing calendar and zodiac inscriptions. This fragment also contains the moon indicator dial assembly including the moon phase sphere in its housing and a single bevel gear (ma1) used in the moon phase indication system.

Fragment D contains at least one unknown gear and according to M.T.Wright possibly two. Their purpose and position has not been ascertained to any accuracy or consensus but lends to the debate for the possible planet displays on the face of the mechanism.

Fragment E was found in 1976 and contains 6 inscriptions from the upper right of the Saros spiral.

Fragment F was found in 2005 and contains 16 inscriptions from the lower right of the Saros spiral. It also contains remnants of the mechanism's wooden housing.

Fragment G is a combination of fragments taken from fragment C while cleaning.

Minor fragmentsEdit

Many of the smaller fragments that have been found contain nothing of value however a few have some inscriptions on them.

Fragment 19 contains significant back door inscriptions including one reading "...76 years...." which refers to the Callippic cycle. Other inscriptions seem to describe the function of the back dials. In addition to this important minor fragment, 15 further minor fragments have remnants of inscriptions on them.

MechanismEdit

Schematic of the artifact's known mechanism

Information on the specific data gleaned from the ruins by the latest inquiries are detailed in the supplement to Freeth's 2006 Nature article.[6]

OperationEdit

On the front face of the mechanism (see reproduction here:[30]) there is a fixed ring dial representing the ecliptic, the twelve zodiacal signs marked off with equal 30 degree sectors. This matched with the Babylonian custom of assigning one twelfth of the ecliptic to each zodiac sign equally, even though the constellation boundaries were variable. Outside of that dial is another ring which is rotatable, marked off with the months and days of the Sothic Egyptian calendar, twelve months of 30 days plus five intercalary days. The months are marked with the Egyptian names for the months transcribed into the Greek alphabet. The first task, then, is to rotate the Egyptian calendar ring to match the current zodiac points. The Egyptian calendar ignored leap days, so it advanced through a full zodiac sign in about 120 years.[31]

The mechanism was operated by turning a small hand crank (now lost) which was linked via a crown gear to the largest gear, the four-spoked gear visible on the front of fragment A, the gear named b1. This moved the date pointer on the front dial, which would be set to the correct Egyptian calendar day. The year is not selectable, so it is necessary to know the year currently set, or by looking up the cycles indicated by the various calendar cycle indicators on the back in the Babylonian ephemeris tables for the day of the year currently set, since most of the calendar cycles are not synchronous with the year. The crank moves the date pointer about 78 days per full rotation, so hitting a particular day on the dial would be easily possible if the mechanism was in good working condition. The action of turning the hand crank would also cause all interlocked gears within the mechanism to rotate, resulting in the simultaneous calculation of the position of the Sun and Moon, the moon phase, eclipse and calendar cycles, and perhaps the locations of planets.

The operator also had to be aware of the position of the spiral dial pointers on the two large dials on the back. The pointer had a "follower" that tracked the spiral incisions in the metal as the dials incorporated four and five full rotations of the pointers. When a pointer reached the terminal month location at either end of the spiral, the pointer's follower had to be manually moved to the other end of the spiral before proceeding further.

FacesEdit

Computer-generated front panel of the Freeth model.

Front faceEdit

The front dial has two concentric circular scales which represent the path of the ecliptic through the heavens. 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 the Zodiac and divided into degrees. The outer calendar dial can be moved against the inner dial 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 36514-day year was used in the Callippic cycle about 330 BC and in the Decree of Canopus in 238 BC, but that is not reflected in the dials.

The position of the sun on the ecliptic is synonymous with the current date in the year. The moon and the five planets known to the Greeks travel along the ecliptic fairly closely, close enough that it makes sense defining their position on the ecliptic.

The following months are inscribed, in Greek letters, on the outer ring:

  • ΘΟΘ (Thoth)
  • ΦΑΩΦΙ (Phaophi)
  • ΑΟΤΡ (Athyr, Hathor)
  • ΧΟΙΑΚ (Choiak)
  • ΤΥΒΙ (Tybi)
  • ΜΕΧΕΙΡ (Mecheir)
  • ΦΑΜΕΝΩΘ (Phamenoth)
  • ΦΑΡΜΟΤΘΙ (Pharmouthi)
  • ΠΑΧΩΝ (Pachon)
  • ΠΔΥΝΙ (Payni)
  • ΕΠΙΦΙ (Epiphi)
  • ΜΕΣΟΡΗ (Mesore)
  • ΕΠ Ep[agomene]

The zodiac dial contains inscriptions of the members of the zodiac, which is believed to be tropical as opposed to sidereal:

Front panel of a 2007 reproduction.
  • ΚΡIOΣ (Krios (Ram), Aries)
  • ΤΑΥΡΟΣ (Tavros (Bull), Taurus)
  • ΔIΔΥΜΟΙ (Didymoi (Twins), Gemini)
  • ΚΑΡΚIΝΟΣ (Karkinos (Crab), Cancer)
  • ΛEΩΝ (Leon (Lion), Leo)
  • ΠΑΡΘEΝΟΣ (Parthenos (Maiden), Virgo)
  • ΧΗΛΑΙ (Chlai (Scorpio's Claw aka Zygos), Libra)
  • ΣΚΟΡΠΙΟΣ (Skorpios (Scorpion), Scorpio)
  • ΤΟΞΩΤΗΣ (Toxotes (Archer), Sagittarius)
  • ΑIΓOΚΕΡΩΣ (Aigokeros (Sea goat), Capricorn)
  • YDΡΟΚΟΟΣ (Hydrokoos (Water carrier), Aquarius)
  • IΧΘΕIΣ (Ichtheis (Fish), Pisces)

Also on the zodiac dial are a number of single characters at specific points (see reconstruction here:[30]). They are keyed to a parapegma, a precursor of the modern day almanac inscribed on the front face beyond the dials, and they mark the locations of specific stars' longitudes on the ecliptic. Some of the parapegma reads (brackets indicate inferred text):

  • {Κ} Evening
  • {Λ} The Hyades set in the evening
  • {Μ} Taurus begins to rise
  • {N} Vega rises in the evening
  • {Θ} The Pleiades 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

At least two pointers indicated positions of bodies upon the ecliptic. A lunar pointer indicated the moon's position, and a mean sun pointer was also shown. The moon position was not a simple mean moon indicator which would indicate movement uniformly around a circular orbit; it allowed for the acceleration and deceleration typical of what we know today is an elliptical orbit, through the first ever known use of epicyclic gearing. It also tracked the precession of the elliptical orbit around the ecliptic in a 8.88 year cycle. The mean sun position is, by definition, the current date. It is speculated that since such pains were taken to get the moon's position correct, then there was likely to have also been a "true sun" pointer in addition to the mean sun pointer to likewise track the elliptical anomaly of the sun (actually the Earth's orbit around the sun), but there is no sign of it in the mechanism today, nor for the possibility, unsupported by the ruins, of planetary orbit pointers for the five then-known planets. See Proposed planet indication gearing schemes below.

Finally, Michael Wright has shown that there was a mechanism to supply the lunar phase in addition to the position.[32] The indicator was a small ball embedded in the lunar pointer, half white and half black, which rotated to show the phase (new, 1st quarter, half, 3rd quarter, full and back) graphically. The data to support this function is available given the sun and moon positions as angular rotations; it is essentially the angle between the two translated into the ball's rotation. It requires a differential gear, a gearing arrangement that sums or differences two angular inputs. Among its other firsts, the Antikythera Mechanism is the first verified construction of a deliberate differential gear scheme in history.

Rear faceEdit

Computer-generated back panel

In July 2008, scientists reported new findings in the journal Nature showing that the mechanism tracked not only the Metonic calendar and predicted solar eclipses, but also calculated the timing of the Ancient Olympic Games.[21] 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.[17][33]

On the back of the mechanism, there are five dials: the two large displays, the Metonic and the Saros, and three smaller indicators, the Olympiad, the Callippic, and the Exeligmos.

The Metonic Dial is the main upper dial. The Metonic cycle, defined in several physical units, is 235 synodic months, which is very close (less than 13 parts per million difference) to 19 tropical years. It is therefore a convenient interval over which to convert between lunar and solar calendars. The Metonic dial covers 235 months in 5 rotations of the dial, following a spiral track with a follower on the pointer that keeps track of the layer of the spiral. The pointer points to the synodic month, counted from new moon to new moon, and the cell contains the Corinthian month names:

  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)

Thus, setting the correct solar time (in days) on the front panel will indicate the current lunar month on the back to within a week or so resolution.

The Callippic dial is the left secondary upper dial, which follows a 76-year cycle. The Callippic cycle is four Metonic cycles, and this dial indicates which of the four Metonic cycles is the current one in the Callippic cycle.

The Olympiad dial is the right secondary upper dial; it is the only pointer on the instrument which travels in a counter-clockwise direction as time is advanced. The dial is divided into four sectors, each of which is inscribed with a year indicator 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.[34] The inscriptions on each one of the four divisions are:

Olympic dial
Year of the cycle Inside the dial inscription Outside the dial inscription
1 LA ΙΣΘΜΙΑ (Isthmia)
ΟΛΥΜΠΙΑ (Olympia)
2 LB NEMEA (Nemea)
NAA (Naa)
3 ΙΣΘΜΙΑ (Isthmia)
ΠΥΘΙΑ (Pythia)
4 L∆ ΝΕΜΕΑ (Nemea)
[undeciphered]

The Saros dial is the main lower spiral dial. The Saros cycle is 18 years and 11⅓ days long (6585.333... days), which is very close to 223 synodic months (6585.3211 days). It is defined as the cycle of repetition of the positions required to cause solar and lunar eclipses, and therefore it can be used to predict them - not only the month, but the day and time of day. Note that the cycle is about 8 hours longer than an integer number of days. Translated into global spin, that means an eclipse occurs not only eight hours later, but 1/3 of a rotation farther to the west. Glyphs in 51 of the 223 synodic month cells of the dial specify the occurrence of 38 lunar and 27 solar eclipses. Some of the abbreviations in the glyphs read:

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

The glyphs show whether the eclipse is solar or lunar, and give the day of the month and hour; obviously, solar eclipses may not be visible at any given point, and lunar eclipses are visible only if the moon is above the horizon at the appointed hour.

The Exeligmos Dial is the secondary lower dial. The Exeligmos cycle is a 54-year triple Saros cycle, 19,756 days long. Since the length of the Saros cycle is to a third of a day (eight hours), so a full Exeligmos cycle returns counting to integer days, hence the inscriptions. The labels on its three divisions are:

  • Blank, which represents the number zero.
  • H (number 8)
  • Iς (number 16)

Thus the dial pointer indicates how many hours must be added to the glyph times of the Saros dial in order to get the exact eclipse times.

DoorsEdit

The mechanism has a wooden casing with a front and a back door. The Back Door appears to be the "Instruction Manual". On one of its fragments is written "76 years, 19 years" representing the Callippic and Metonic cycles. Also written is "223" for the Saros cycle. On another one of its fragments is written on the spiral subdivisions "235" for the Metonic dial. The front door also has inscriptions.[21][35]

GearingEdit

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.c

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. That is irrelevant to the question of whether that position was computed using a heliocentric or geocentric view of the solar system; either computational method should and does result in the same position (ignoring ellipticity), within the error factors of the mechanism. Ptolomy's epicyclic solar system (still 300 years in the mechanism's future), carried forward with more epicycles, was more accurate predicting the positions of planets than Copernicus' view, up until Kepler introduced the possibility that orbits are ellipses.[36]

Evans et al. suggest that to display the mean positions of the five classical planets would require only 17 further gears which could be positioned in front of the large driving gear and indicated using individual circular dials on the face.[37]

Tony Freeth and Alexander Jones have modeled and published details of a version using several gear trains mechanically similar to the lunar anomaly system allowing for indication of the planets' positions as well as synthesis of the sun anomaly. Their system, they claim, is more authentic than Wright's model as it utilises the known skill sets of the Greeks of that period and does not add excessive complexity or internal stresses to the machine.[31]

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.

A table of the gears, their teeth, and the expected and computed rotations of various of the important gears follows. The gear functions comes from.[21] The computed values start with 1 year/revolution for the b1 gear, and the remainder are computed directly from gear teeth ratios. The gears marked with the * are missing, or have predecessors missing, from the known mechanism; these gears have been estimated with reasonable gear teeth counts.

The Antikythera Mechanism: known gears and accuracy of computation
Gear name Function Expected simulated interval of a 360 degree revolution Formula ("Time" is interval represented by one complete revolution of the gear) Computed value
B1, B2 Year gear 1 tropical year 1 (by definition) 1 year (assumed)
E2, K1, K2, E6, B3 the moon's orbit 1 sidereal month (27.321661 days) Time(E2,K1,K2,E6,B3) = Time(B1) * C1 / B2 * D1 / C2 * E2 / D2 27.321 days (on average)
R1 lunar phase display 1 synodic month (29.530589 days) Time(R1) = 1 / (1 / Time(B2 [mean sun] or sun3 [true sun])) + (1 / Time(B3))) 29.530 days
N1* Metonic pointer Metonic cycle () / 5 spirals around the dial = 1387.94 days Time(N1) = Time(B1) * (L1 / B2) * (M1 /L2) * (N1 / M2) 1387.9 days
O1* Olympiad pointer 4 years Time(O1) = Time(N1) * (O1 / N3) 4.00 years
Q1* Callippic pointer 27758.8 days Time(Q1) = Time(N1) * (P1 / N2) * (Q1 /P2) 27758 days
E3* lunar orbit precession 8.85 years Time(E3) = Time(B1) * (L1 / B2) * (M1 / L2) * (E3 / M3) 8.8826 years
G1* Saros cycle Saros time / 4 turns = 1646.33 days Time(G1) = Time(E3) * (F1 / E4) * (G1 / F2) 1646.3 days
I1* Exeligmos pointer 19755.8 days Time(I1) = Time(G1) * (H1 / G2) * (I1 / H2) 19756 days
The following are proposed gearing from the 2012 Freeth and Jones reconstruction:
sun3* True sun pointer 1 mean year Time(sun3) = Time(B1) * (sun3 / sun1) * (sun2 / sun3) 1 mean year (on average)
mer2* Mercury pointer 115.88 days (synodic period) Time(mer2) = Time(B1) * (mer2 / mer1) 115.89 days (on average)
ven2* Venus pointer 583.93 days (synodic period) Time(ven2) = Time(B1) * (ven1 / sun1) 584.39 days (on average)
mars4* Mars pointer 779.96 days (synodic period) Time(mars4) = Time(B1) * (mars2 / mars1) * (mars4 / mars3) 779.84 days (on average)
jup4* Jupiter pointer 398.88 days (synodic period) Time(jup4) = Time(B1) * (jup2 / jup1) * (jup4 / jup3) 398.88 days (on average)
sat4* Saturn pointer 378.09 days (synodic period) Time(sat4) = Time(B1) * (sat2 / sat1) * (sat4 / sat3) 378.06 days (on average)

Known gear schemeEdit

[6][27][38]

A schematic representation of the gearing of the Antikythera Mechanism, including the latest published interpretation of existing gearing, gearing added to complete known functions and proposed gearing to accomplish additional functions, namely true sun pointer and pointers for the five then-known planets, as proposed by Freeth and Jones, 2012. Proposed gearing crosshatched.

The Sun gear is operated from the hand operated crank (connected to gear a1, driving the large four-spoked mean sun gear, b1) and in turn drives the rest of the gear sets. The sun gear is b1/b2 and b2 has 64 teeth. It directly drives the date/mean sun pointer (there may have been a second, "true sun" pointer which displayed the sun's elliptical anomaly; that is discussed below in the Freeth reconstruction). In this discussion, we refer to modeled rotational period of various pointers and indicators; they all assume the input rotation of the b1 gear of 360 degrees, corresponding with one tropical year, and are computed solely on the basis of the gear ratios of the gears named.

The Moon train starts with gear b1 and proceeds through c1, c2, d1, d2, e2, e5, k1, k2, e6, e1 and b3 to the moon pointer on the front face. The gears k1 and k2 form an epicyclic gear system; they are an identical pair of gears that don't mesh, but rather they operate face-to-face, with a short pin on k1 inserted into a slot in k2. The two gears have different centres of rotation, so the pin must move back and forth in the slot. That increases and decreases the radius at which k2 is driven, necessarily also varying its angular velocity (assuming the velocity of k1 is even) faster in some parts of the rotation than others. Over an entire revolution the average velocities are the same, but the fast-slow variation models the effects of the moon's elliptical orbit, in consequence of Kepler's 2nd and 3rd laws. The modeled rotational period of the moon pointer (averaged over a year) is 27.321 days, compared to the modern length of a lunar sidereal month of 27.321661 days. As mentioned, the pin/slot driving of the k1/k2 gears varies the displacement over a year's time, and the mounting of those two gears on the e3 gear supplies a precessional advancement to the ellipticity modelling with a period of 8.8826 years, compared with the current value of precession period of the moon of 8.85 years.

The system also models the phases of the moon. The moon pointer holds a shaft along its length, on which is mounted a small gear named r, which meshes to the sun pointer at B0 (the connection between B0 and the rest of B is not visible in the original mechanism, so whether b0 is the current date/mean sun pointer or a hypothetical true sun pointer is not known). The gear rides around the dial with the moon, but is also geared to the sun - the effect is to perform a differential gear operation, so the gear turns at the synodic month period, measuring in effect the angle of the difference between the sun and moon pointers. The gear drives a small ball that appears through an opening in the moon pointer's face, painted longitudinally half white and half black, displaying the phases pictorially. It turns with an modeled rotational period of 29.53 days; the modern value for the synodic month is 29.530589 days.

The Metonic train is driven by the drive train b1, b2, l1, l2, m1, m2 and n1, which is connected to the pointer. The modeled rotational period of the pointer is the length of the 6939.5 days (over the whole five-rotation spiral), while the modern value for the Metonic cycle is 6939.7 days.

The Olympiad train is driven by b1, b2, l1, l2, m1, m2, n1, n3 and o1, which mounts the pointer. It has a computed modeled rotational period of exactly 4 years, as expected. It is, incidentally, the only pointer on the mechanism which rotates counter-clockwise; all the others rotate clockwise.

The Callippic train is driven by b1, b2, l1, l2, m1, m2, n1, n2, p1, p2 and q1, which mounts the pointer. It has a computed modeled rotational period of 27758 days, while the modern value is 27758.8 days.

The Saros train is driven by b1, b2, l1, l2, m1, m3, e3, e4, f1, f2 and g1, which mounts the pointer. The modeled rotational period of the Saros pointer is 1646.3 days (in four rotations along the spiral pointer track); the modern value is 1636.33 days.

The Exeligmos train is driven by b1, b2, l1, l2, m1, m3, e3, e4, f1, f2, g1, g2, h1, h2 and i1, which mounts the pointer. The modeled rotational period of the Exeligmos pointer is 19756 days; the modern value is 19755.96 days.

Gears m3, n1-3, p1-2 and q1 did not survive in the wreckage. The functions of the pointers was deduced from the remains of the dials on the back face, and reasonable, appropriate gearage to fulfill the functions was proposed, and is generally accepted.

Proposed planet indication gearing schemesEdit

Because of the large space between the mean sun gear and the front of the case and the size of and mechanical features on the mean sun gear it is very likely that the mechanism contained further gearing that has either been lost in or subsequent to the shipwreck or was removed before being loaded onto the ship. This lack of evidence and nature of the front part of the mechanism has led to numerous attempts to emulate what the Greeks of the period would have done and of course because of the lack of evidence many solutions have been put forward.

Wright proposal
Evans et al. proposal
Freeth et al. proposal

Michael Wright was the first person to design and build a model with not only the known mechanism but also with his emulation of a potential planetarium system. He suggested that along with the lunar anomaly the deeper understood solar anomaly would also be indicated. He achieved this by the attachment of three meshing and equally sized gears to one of the spokes of the b1 mean sun gear. The farthest gear away from the central spindle was fitted with an offset pin over which an arm with a slot was fitted which in turn attached to the sun spindle, causing anomalous movement indicative of the solar anomaly.

Inferior body (Sun, Mercury and Venus) motions are essentially the sun's mean orbit around the Earth (i.e., in the current view, the Earth's mean orbit around the sun). There are additional limited excursions to fore and aft along the ecliptic, which average out to zero after several years observation; the true sun's deviation is due to Earth's orbital ellipticity, and the other two to both orbital ellipticity and apparent retrograde motion at superior conjunction. The inferior planets are indicated using more gears attached to b1 or attached to a plate via the use of pillars which may have existed on b1. These gears ultimately drive disks protruding from which are pins over which arms with slots are placed. The arms are attached to the relevant planet indication spindle and through a combination of both the rotation of b1 and the action of the pin and slot mechanisms the planets' motions are synthesised and indicated on the front dial.

The superior planets are more complex - starting with the Earth's orbit as a basis, Mars, Jupiter and Saturn make excursions along the ecliptic which accumulate year by year and never average out, so the "back and forth" movement of a simple epicycle, as in the inferior planets, doesn't work. Each superior planet system is mounted on a separate 223 toothed main gear (the same tooth count as b1) which is mounted on a rectangular plate. This plate is mounted to the frame with wooden spacer blocks on each short end of the rectangular plate. These plates are vertically mounted together and attached to the mechanism as a whole. The individual main gears are driven by smaller transfer gears driven by b1, as all of these gears share the same tooth counts the ratio between b1 and superior gear is 1. Each superior system is very similar with the only differences being the size of the gears. The main gears and upper plate are free to rotate, while the central spindle gear is fixed. The main gear is driven by the b1 transfer gear and drives the smaller coaxial gear attached to its surface. This gear drives a larger transfer gear which drives two smaller gears, one of these is coaxial and on the other side of the upper plate, the other is on the same side of the upper plate and drives the pin carrier wheel which is on the other side of the upper plate. The smaller driven gear then drives the fixed gears on the top of the upper plate, the smaller of those (or in the case of the Mars mechanism the only one) drives the fixed spindle gear. Attached to the spindle is an arm with a slot which engages with the aforementioned pin carrier wheel. This whole system rotates with the mean sun gear and subtracts from that gear's angular velocity to make the required ratio and indicate it on the front face.[28][39][40]

In Wright's paper there is a footnote:

Note added 29 November 2006: This paper was submitted on 2 September 2006 and accepted for publication on 26 October 2006. Since then the Antikythera Mechanism Research Project Group has published interesting findings [citation:[6]]. Their independent survey has included study of the newly discovered fragment F, a part of the lower back dial which was not available to me. Their reading of the inscriptions on this dial reveals that the function displayed on it was the eclipse cycle of 223 synodic months, distributed around the four-turn spiral scale. (As eclipses of the Sun are rare events, the engraved sequence may, in principle, afford means for dating the Mechanism.) One revolution of the pointer thus represented (223÷4) synodic months, not one draconitic month as I have suggested. The Group offers a modification of my gear train which achieves this function and also incorporates exactly those mechanical features that I characterised as having probably been made redundant by alteration of the instrument. The satisfactory way in which the Group’s suggestions for these parts fall in with my own observations of the artifact itself, and remove residual difficulties with my reconstruction, lead me to believe that they are correct. I have no hesitation either in adopting the Group’s revisions of the function of the lower back dial and of the internal mechanism or in withdrawing statements concerning these features that conflict with them. The changes, though important, are physically quite slight, and do not affect my arguments for other significant features of my reconstruction. I stand by the conclusions of my paper.

Wright incorporated the indicated changes into his model.

Evans, Carman and Thorndike published a solution[37] with significant differences from Wright's. Their proposal centred on what they observed as irregular spacing of the inscriptions on the front dial face which to them seemed to indicate an off centre sun indicator arrangement, this would simplify the mechanism by removing the need to simulate the solar anomaly. They also suggested that rather than accurate planetary indication (rendered impossible by the offset inscriptions) there would be simple dials for each individual planet showing information such as key events in each planet's cycle, initial and final appearances in the night sky and apparent direction changes. This system would lead to a much simplified gear system, with much reduced forces and complexity.

Their proposal used simple meshed gear trains and accounted for the previously unexplained 63 toothed gear in fragment D. They proposed two face plate layouts, one with evenly spaced dials and another with a gap in the top of the face to account for criticism regarding their not using the apparent fixtures on the b1 gear. They proposed that rather than bearings and pillars for gears and axles they simply held weather and seasonal icons to be displayed through a window.[37]

In a paper published in 2012 Carman, Thorndike and Evans proposed a system of epicyclic gearing with pin and slot followers.[41]

Freeth and Jones published their proposal in 2012 after extensive research and work they came up with a compact and feasible solution to the question of planetary indication. They also propose indicating the solar anomaly (that is, the sun's apparent position in the zodiac dial) on a separate pointer from the date pointer, which indicates the sun's mean position as well as the date on the month dial, if the two dials are correctly synchronised. Their front panel display is essentially the same as Wright's. Unlike Wright's model however, this model has not been physically built and is only a 3D static model. Freeth notes the backside inscription mentions "little spheres", apparently confirming round stones used to identify the various pointers.

Internal gearing relationships of the Antikythera Mechanism, based on the Freeth and Jones proposal

The system to synthesise the solar anomaly is very similar to that used in Wright's proposal. Three gears, one fixed in the centre of the b1 gear and attached to the sun spindle, the other fixed on one of the spokes (in their proposal the one on the bottom left) acting as an idle gear and the final positioned next to that one, the final gear is fitted with an offset pin and over said pin an arm with a slot which is in turn attached to the sun spindle inducing anomaly as the mean sun wheel turns.

The inferior planet mechanism includes the sun (treated as a planet in this context), Mercury and Venus. For each of the three systems there is an epicyclic gear whose axis is mounted on b1, thus the basic frequency is the Earth year (as it is, in truth, for epicyclic motion in the sun and all the planets, excepting only the moon). Each meshes with a gear grounded to the mechanism frame. Each has a pin mounted, potentially on an extension of one side of the gear that enlarges the gear but doesn't interfere with the teeth; in some cases the needful distance between the gear's centre and the pin is farther than the radius of the gear itself. A bar with a slot along its length extends from the pin towards the appropriate coaxial tube, at whose other end is the object pointer, out in front of the front dials. The bars could have been full gears, though there is no need for the waste of metal, since the only working part is the slot. Also, using the bars avoids interference between the three mechanisms, which are each set on one of the four spokes of b1. Thus there is one new grounded gear (one was identified in the wreckage, and the second is shared by two of the planets), one gear used to reverse the direction of the sun anomaly, three epicyclic gears and three bars/coaxial tubes/pointers, which would qualify as another gear each. Five gears and three slotted bars in all.

The superior planets systems - Mars, Jupiter and Saturn - all follow the same general principle of the lunar anomaly mechanism. Like the inferior systems, each has a gear whose centre pivot is on an extension of b1, and which meshes with a grounded gear. It presents a pin and a centre pivot for the epicyclic gear which has a slot for the pin, and which meshes with a gear fixed to a coaxial tube and thence to the pointer. Each of the three mechanisms can fit within a quadrant of the b1 extension, and they are thus all on a single plane parallel with the front dial plate. Each one uses a ground gear, a driving gear, a driven gear and a gear/coaxial tube/pointer, thus twelve gears additional in all.

There are in total eight coaxial spindles of various nested sizes to transfer the rotations in the mechanism to the eight pointers. So in all, there are 30 original gears, seven gears added to complete calendar functionality, 17 gears and three slotted bars to support the six new pointers, for a grand total of 54 gears, three bars and eight pointers in Freeth and Jones' design.[31]

Latest resultsEdit

New technology has been brought to bear on the Antikythera Mechanism, and late results, and some surprising facts, have been brought to light about it.

2006Edit

In November 2006, the science journal Nature published a new reconstruction of the mechanism by the Antikythera Mechanism Research Project, based on the high-resolution X-ray tomography described above.[42] This work doubled the amount of readable text, corrected prior transcriptions, and provided a new translation. The character style of the inscriptions led to another dating of the mechanism to around 150 to 100 BC. It is evident that the inscriptions contain a manual with an astronomical, mechanical and geographical section, estimated at 22,000 characters.

The new discoveries confirm that the mechanism is an astronomical analog calculator, or orrery, used to predict the positions of celestial bodies. This work proposes that the mechanism possessed 37 gears, of which 30 survive, and was used for prediction of the position of the Sun and the Moon. Based on the inscriptions, which mention the stationary points of the planets, the authors speculate that planetary motions may also have been indicated (see the 2012 paper below).

On the front face are graduations for the solar scale and the zodiac together with pointers that indicated the position of the Sun, the Moon, the lunar phase, and possibly the planetary motions.

On the back, two spiral scales (made of half-circles with two centers) with sliding pointers indicated the state of two further important astronomical cycles: the Saros cycle, the period of approximately 18 years separating the return of the Sun, Moon and Earth to the same relative positions and the more accurate Exeligmos cycle of 54 years and one day (essential in eclipse prediction, see Eclipse cycle). It also contains another spiral scale for the Metonic cycle (19 years, equal to 235 lunar months) and the Callippic cycle with a period of 1016 lunar orbits in approximately 76 years.

The Moon mechanism, using an ingenious train of gears, two of them linked with a slightly offset axis and pin in a slot, shows the position of the Moon during the month. The velocity of the Moon appears to vary according to the theory of Hipparchus, and to a good approximation follows Kepler's second law for the angular velocity, being faster near the perigee and slower at the apogee.

2008Edit

In July 2008, a paper providing further details about the mechanism was published in Nature.[21] In this paper it is demonstrated that the mechanism also contained a dial divided into four parts, and demonstrated a four-year cycle through four segments of one year each, which is thought to be a means of describing which of the games (such as the ancient Olympics) that took place in two and four-year cycles were to take place in any given year.

The names of the months have been read; they are the months attested for the colonies of Corinth (and therefore also traditionally assumed for Corinth, Kerkyra, Epidamnos, and Syracuse, which have left less direct evidence). The investigators suggest that the device might well be of Syracusan design and so descend from the work of Archimedes; alternatively it could have been ordered by and customized for any of these markets and was being shipped.

Access to the full text of this 2008 paper requires a paid subscription. However, the submitted version can be downloaded.[43]

2010Edit

Nature published another study in November 2010,[44] which suggests that the mechanism may be based on computation methods used in Babylonian astronomy, not ancient Greek astronomy, implying that Babylonian astronomy inspired the Greek counterpart; including the mechanical constructs.

The article concentrates on suggestions by James Evans, Christián Carman and Alan Thorndike that a simpler gearing system was used to display key events of displayed bodies. Their first suggestion is that the zodiac indicator dial was unevenly graduated to comply with the sun's anomalous progress through the sky. This system would simplify the sun's gear system. However the uneven graduation of the zodiac dial would lead to any planet indicators not being very accurate. To overcome this problem they suggest that each planet had a dial of its own and rather than showing precise location indication they simply show key events in each planet's cycle, such as initial and final appearances in the night sky and direction changes. This would supply the same information as a complex epicyclic gearing system but using much simpler gear trains.

The article also states that inscriptions are still being deciphered from x-ray images.

2012Edit

In their article entitled The Cosmos in the Antikythera Mechanism Freeth and Jones suggest that it is quite likely that the mechanism included gearing and indicators for the planets as well as possibly indicating solar anomalies.[31]

They base their proposal on inscriptions detailing the motion of the five known planets as well as on the noticeable holes and brackets on the main driving gear.

They suggest that the mean sun wheel (b1) may have been utilised as a carrier for various gear trains and other hardware and they describe and simulate how this could have been possible. They also describe in detail the evidence they have found for additional fixings on the gear. These include bearings for shafts on some of the spokes, a recess and a raised flat area possibly used to attach fixings with solder or rivets and pillars around the edge of the wheel which were potentially used to hold a sub plate and fixing bridges. They also find evidence for a 1 mm hole drilled lengthwise into the spoke at the bottom left; this would have been a complex technical achievement at the time and they are unable to explain its purpose, but tentatively suggest something to do with lubrication.

Their model simulates the solar anomaly, inferior planets and superior planets and indicates their positions on the front face along with the date and lunar pointers.

Investigations reveal that their simulated mechanism is not particularly accurate, the Mars pointer being up to 38° off at times. This is due to the inaccuracies of the Greek theories of the planets and their lack of more detailed knowledge.

In short, the Antikythera Mechanism was a machine designed to predict celestial phenomena according to the sophisticated astronomical theories current in its day, the sole witness to a lost history of brilliant engineering, a conception of pure genius, one of the great wonders of the ancient world—but it didn’t really work very well!

The researchers note that the inevitable "looseness" in the mechanism due to the hand-built gears with their triangular teeth and the frictions between gears and in bearing surfaces would have probably swamped the finer solar and lunar correction mechanisms built into it:

Though the engineering was remarkable for its era, recent research indicates that its design conception exceeded the engineering precision of its manufacture by a wide margin—with considerable accumulative inaccuracies in the gear trains, which would have cancelled out many of the subtle anomal[y corrections] built into its design.

On the visual representation he supplies in the paper, the pointers on the front zodiac dial have small, round identifying stones. Interestingly, Freeth mentions a quote from an ancient papyrus:

...a voice comes to you speaking. Let the stars be set upon the board in accordance with [their] nature except for the Sun and Moon. And let the Sun be golden, the Moon silver, Kronos [Saturn] of obsidian, Ares [Mars] of reddish onyx, Aphrodite [Venus] lapis lazuli veined with gold, Hermes [Mercury] turquoise; let Zeus [Jupiter] be of (whitish?) stone, crystalline (?)...[45]

New dive on wreck siteEdit

The Woods Hole Oceanographic Institution in the United States received permission from the Greek Government in 2012 to conduct new dives around the deep shoals of Antikythera. Brendan Foley of the institute will be conducting a new survey of the debris field along with Theotokis Theodoulou of the Greek Ephorate of Underwater Antiquities. The researchers are hoping to find other small pieces of the Antikythera mechanism on the sea floor. Additionally they hope to locate and survey the wrecks of other ships that foundered on the island's shoals.[46]

In September 2013, the divers located artifacts that spread across the rocky sea floor on a steep slope between 35-60m deep, 200m away from the site excavated by J. Y. Cousteau.[47] The latest expedition objectives were to survey the entire underwater Antikythera coastline to 40m, relocate the shipwreck site and conduct a full underwater archaeology project that would begin in 2014.[48]

Speculation about the mechanism's purposeEdit

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.[6]

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:

  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 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.
  2. 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.
  3. 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 ]

The device is unlikely to have been intended for navigation use because:

  1. Some data, such as eclipse predictions, are unnecessary for navigation.
  2. 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.[49]

Similar devices in ancient literatureEdit

Cicero's De re publica, 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.

I had often heard this celestial globe or sphere mentioned on account of the great fame of Archimedes. Its appearance, however, did not seem to me particularly striking. There is another, more elegant in form, and more generally known, moulded by the same Archimedes, and deposited by the same Marcellus, in the Temple of Virtue at Rome. But as soon as Gallus had begun to explain, by his sublime science, the composition of this machine, I felt that the Sicilian geometrician must have possessed a genius superior to any thing we usually conceive to belong to our nature. Gallus assured us, that the solid and compact globe, was a very ancient invention, and that the first model of it had been presented by Thales of Miletus. That afterwards Eudoxus of Cnidus, a disciple of Plato, had traced on its surface the stars that appear in the sky, and that many years subsequent, borrowing from Eudoxus this beautiful design and representation, Aratus had illustrated them in his verses, not by any science of astronomy, but the ornament of poetic description. He added, that the figure of the sphere, which displayed the motions of the Sun and Moon, and the five planets, or wandering stars, could not be represented by the primitive solid globe. And that in this, the invention of Archimedes was admirable, because he had calculated how a single revolution should maintain unequal and diversified progressions in dissimilar motions.

When Gallus moved this globe it showed the relationship of the Moon with the Sun, and there were exactly the same number of turns on the bronze device as the number of days in the real globe of the sky. Thus it showed the same eclipse of the Sun as in the globe [of the sky], as well as showing the Moon entering the area of the Earth's shadow when the Sun is in line ... [missing text]

[i.e. It showed both solar and lunar eclipses.][50]

Pappus of Alexandria stated that Archimedes had written a now lost manuscript on the construction of these devices entitled On Sphere-Making.[51][52] 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).[53] 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.[54] 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.

An odometer by Leonardo da Vinci based on the design by Roman engineer Vitruvius
If Cicero's account is correct, 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 said 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 ..."[55]

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 the Middle Ages.[56] 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.[57] 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 in monasteries. 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.[57] It is possible that this medieval technology may have been transmitted to Europe and contributed to the development of mechanical clocks there.[7]

Investigations and reconstructionsEdit

Reconstruction of the Antikythera mechanism in the National Archaeological Museum, Athens (made by Robert J. Deroski, based on Derek J. de Solla Price's model)

Various people have investigated the device, including German philologist Albert Rehm; Derek J. de Solla Price (with Charalampos Karakalos and his wife Emily); Allan George Bromley (with Frank Percival, Michael Wright and Bernard Gardner).[58]

The first attempt to reconstruct a model of the device was made by the Greek Rear Admiral Ioannis Theofanidis, who began studying the mechanism in the late 1920s and published a study in 1934. Theofanidis spent most of his final years and much of his family fortune to finance his research onto the mechanism's gearwork, but his death interrupted his work,[7] much of which lay forgotten and unpublished until consulted by de Solla Price twenty years later.

Derek J. de Solla PriceEdit

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

Price published several papers on "Clockwork before the Clock".[7][59] and "On the Origin of Clockwork",[60] before the first major publication in June 1959 on the mechanism: "An Ancient Greek Computer".[61] This was the lead article in Scientific American and appears to have been initially published at the prompting of Arthur C. Clarke, according to the book Arthur C. Clarke's Mysterious World (see end of chapter 3). In "An Ancient Greek Computer" Price advanced the theory that the Antikythera mechanism was a device for calculating the motions of stars and planets, which would make the device the first known analog computer. Until that time, the Antikythera mechanism's function was largely unknown, though it had been correctly identified as an astronomical device, perhaps being an astrolabe.

In 1971, Price, by then the first Avalon Professor of the History of Science at Yale University, teamed up with Charalampos Karakalos, professor of nuclear physics at the Greek National Centre of Scientific Research "DEMOKRITOS". Karakalos took both gamma- and X-ray radiographs of the mechanism, which revealed critical information about the device's interior configuration.

In 1974, Price published "Gears from the Greeks: the Antikythera mechanism – a calendar computer from ca. 80 BC",[5] where he presented a model of how the mechanism could have functioned.

Price's model, as presented in his "Gears from the Greeks", was the first theoretical attempt at reconstructing the device based on its inner structure revealed by the radiographs. According to that model, the front dial shows the annual progress of the Sun and Moon through the zodiac against the Egyptian calendar. The upper rear dial displays a four-year period and has associated dials showing the Metonic cycle of 235 synodic months, which approximately equals 19 solar years. The lower rear dial plots the cycle of a single synodic month, with a secondary dial showing the lunar year of 12 synodic months.

One of the remarkable proposals made by Price was that the mechanism employed differential gears, which enabled the mechanism to add or subtract angular velocities. The differential was used to compute the synodic lunar cycle by subtracting the effects of the Sun's movement from those of the sidereal lunar movement.

Allan George BromleyEdit

Professor Allan Bromley, a computer scientist of the University of Sydney improved on Price's reconstruction with the help of Frank Percival, a clockmaker. Having tested Price's theory using Meccano parts, he found that the mechanism was unworkable. Working with Percival, he improved the device by altering the function of the handle so that one complete rotation would correspond to a single day, which he considered to be the most obvious astronomical unit. Bromley worked with the same set of parts as Price, but suspected that a gap in the mechanism was originally home to several extra gears.[62]

Another breakthrough by Bromley concerned a train of gearing which appeared to have 15 and 63 teeth, for which Price had been unable to discover a purpose. Price considered these numbers to be too difficult to work with, and assumed that they should be corrected to 16 and 64, theorising that it could have operated a four-year cycle on the device. Bromley worked with the original count of 15 and 63 teeth, discovering that the train's cycle was four and a half years; four of such cycles equalled 18 years, a duration equal to the cycle of eclipses. With this gearing, the mechanism worked correctly, with the pointer moving into a new square for each new moon, as the handle is turned, meaning that each square on a dial represented one month. Over 223 months, or 18 years, the complete cycle is shown.[62]

Bromley went on to make new, more accurate X-ray images in collaboration with Michael Wright.

Michael WrightEdit

Michael Wright, formerly Curator of Mechanical Engineering at The London Science Museum and now of Imperial College, London, made a completely new study of the original fragments together with Allan George Bromley. They used a technique called linear X-ray tomography which was suggested by retired consultant radiologist, Alan Partridge. For this, Wright designed and made an apparatus for linear tomography, allowing the generation of sectional 2D radiographic images.[63] Early results of this survey were presented in 1997, which showed that Price's reconstruction was fundamentally flawed.[64]

Further study of the new imagery allowed Wright to advance a number of proposals. Firstly he developed the idea, suggested by Price in "Gears from the Greeks", that the mechanism could have served as a planetarium. Wright's planetarium not only modelled the motion of the Sun and Moon, but also the Inferior Planets (Mercury and Venus), and the Superior Planets (Mars, Jupiter and Saturn).[65][66]

Wright proposed that the Sun and Moon could have moved in accordance with the theories of Hipparchus and the five known planets moved according to the simple epicyclic theory suggested by the theorem of Apollonius. In order to prove that this was possible using the level of technology apparent in the mechanism, Wright produced a working model of such a planetarium.[67][68]

Wright also increased upon Price's gear count of 27 to 31[66] including 1 in Fragment C that was eventually identified as part of a Moon phase display.[32] He suggested that this is a mechanism that shows the phase of the Moon by means of a rotating semi-silvered ball, realized by the differential rotation of the sidereal cycle of the Moon and the Sun's yearly cycle. This precedes previously known mechanisms of this sort by a millennium and a half.

More accurate tooth counts were also obtained,[69] allowing a new gearing scheme to be advanced.[70] This more accurate information allowed Wright to confirm Price's perceptive suggestion that the upper back dial displays the Metonic cycle with 235 lunar months divisions over a five-turn scale. In addition to this Wright proposed the remarkable idea that the main back dials are in the form of spirals, with the upper back dial out as a five-turn spiral containing 47 divisions in each turn. It therefore presented a visual display of the 235 months of the Metonic cycle (19 years ≈ 235 Synodic Months). Wright also observed that fragmentary inscriptions suggested that the pointer on the subsidiary dial showed a count of four cycles of the 19-year period, equal to the 76-year Callippic cycle.[71]

Based on more tentative observations, Wright also came to the conclusion that the lower back dial counted Draconic Months and could perhaps have been used for eclipse prediction.[72]

All these findings have been incorporated into Wright's working model,[71] demonstrating that a single mechanism with all these functions could be built, and would work.

Despite the improved imagery provided by the linear tomography Wright could not reconcile all the known gears into a single coherent mechanism, and this led him to advance the theory that the mechanism had been altered, with some astronomical functions removed and others added.[71]

Finally, as an outcome of his considerable research,[63][71][73][74][75][76][77] Wright also conclusively demonstrated that Price's suggestion of the existence of a differential gearing arrangement was incorrect.[32][71]

In 2006 Wright completed what he believed to be an almost exact replica of the mechanism.[78]

Michael Wright's research on the mechanism is continuing in parallel with the efforts of the Antikythera Mechanism Research Project (AMRP). Recently Wright slightly modified his model of the mechanism to incorporate the latest findings of the AMRP regarding the function of the pin and slot engaged gears that simulate the anomaly in the Moon's angular velocity. He has agreed with the AMRP researchers that the lower rear dial represents the Saros eclipse cycle rather than the Draconic calendar, and that what he earlier saw as evidence for the reworking of the mechanism over its life is better explained by these changed functionalities.[28] On 6 March 2007 he presented his model in the National Hellenic Research Foundation in Athens.

Antikythera Mechanism Research ProjectEdit

The Antikythera Mechanism Research Project was launched in 2005,[79] a joint program between Cardiff University (M. Edmunds, T. Freeth), the National and Kapodistrian University of Athens (X. Moussas, Y. Bitsakis), the Aristotle University of Thessaloniki (J.H. Seiradakis), the National Archaeological Museum of Athens, X-Tek Systems UK[80] and Hewlett-Packard USA, initially funded by the Leverhulme Trust supported by the J. F. Costopoulos Foundation [81] and the National Bank of Greece Cultural Foundation.[82]

The mechanism's fragility precluded its removal from the national Archaeological Museum of Greece, so the Hewlett-Packard research team[83] and X-Tek Systems had to bring their devices to Greece. HP built a 3-D surface imaging device, known as the "PTM Dome", that surrounds the object under examination. X-Tek Systems developed a 12-ton 450 kV microfocus computerised tomographer especially for the Antikythera Mechanism.

The team announced in October 2005 that new pieces of the Antikythera mechanism had been found, making a total of 82 fragments.[citation needed] Most of the new pieces had been stabilized but were awaiting conservation. In May 2006, the team announced that the imaging system had allowed much more of the Greek inscription to be viewed and translated, from about 1,000 characters that were visible previously, to over 2,160 characters, representing about 95% of the extant text. The team's findings shed new light on the function and purpose of the Antikythera mechanism. The first results were announced at an international conference in Athens in November and December 2006.[84]

Documentaries, exhibitions and popular cultureEdit

As of 2012, the Antikythera mechanism was now displayed as part of a temporary exhibition about the Antikythera Shipwreck,[85] accompanied by reconstructions made by Ioannis Theofanidis, Derek de Solla Price, Michael Wright, the Thessaloniki University and Dionysios Kriaris. Other reconstructions are on display at the American Computer Museum in Bozeman, Montana, at the Children's Museum of Manhattan in New York, at Astronomisch-Physikalisches Kabinett in Kassel, Germany, and at the Musée des Arts et Métiers in Paris.

The National Geographic documentary series Naked Science had an episode dedicated to the Antikythera Mechanism entitled "Star Clock BC" that aired on January 20, 2011.[86] A documentary, The World's First Computer, was produced in 2012 by the Antikythera mechanism researcher and film-maker Tony Freeth.[87] In 2012 BBC Four aired The Two-Thousand-Year-Old Computer;[88] it was also aired on April 3, 2013 in the United States on NOVA, the PBS science series, under the name Ancient Computer.[89] It documents the discovery and 2005 investigation of the mechanism by the Antikythera Mechanism Research Project.

A fictionalised version of the device was a central plot point in the film Stonehenge Apocalypse (2010), where it was used as the artifact that saved the world from impending doom.[90] On May 25, 2010, the first episode of the History Channel series Ancient Aliens presented it as one of the many "evidences" of ancient alien astronauts visiting earth and leaving behind technology.[91] In Assassin's Creed IV: Black Flag, a game in the popular video game series Assassin's Creed, the Antikythera Mechanism is brought into the game's lore through in-game texts. It is fabled to be a small portion of a much larger device used to "predict the future" through massive probability calculations, and was used by an ancient race to accurately send messages to the series' protagonist, Desmond Miles.

A fully functioning Lego reconstruction of the Antikythera mechanism was built in 2010 by hobbyist Andy Carrol, and featured in a short film produced by Small Mammal in 2011.[92]

Several exhibitions have been staged worldwide,[93] leading to the main "Antikythera shipwreck" exhibition at the National Archaeological Museum in Athens, Greece.

See alsoEdit

ReferencesEdit

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  2. ^ Seaman, Bill; Rössler, Otto E. (1 January 2011). Neosentience: The Benevolence Engine. Intellect Books. p. 111. ISBN 978-1-84150-404-9. Retrieved 28 May 2013. "Mike G. Edmunds and colleagues used imaging and high-resolution X-ray tomography to study fragments of the Antikythera Mechanism, a bronze mechanical analog computer thought to calculate astronomical positions" 
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Further readingEdit

BooksEdit

  • James, Peter; Thorpe, Nick (1995). Ancient Inventions. New York: Ballantine. ISBN 0-345-40102-6. 
  • Marchant, Jo (6 November 2008). Decoding the Heavens: Solving the Mystery of the World's First Computer. William Heinemann Ltd. ISBN 0-434-01835-X. 
  • Price, Derek J. de Solla (1975). Gears from the Greeks: The Antikythera Mechanism – A Calendar Computer from ca. 80 BC. New York: Science History Publications. ISBN 0-87169-647-9. 
  • Rosheim, Mark E. (1994). Robot Evolution: The Development of Anthrobotics. John Wiley & Sons. ISBN 0-471-02622-0. 
  • Russo, Lucio (2004). The Forgotten Revolution: How Science Was Born in 300 BC and Why It Had To Be Reborn. Berlin: Springer. ISBN 3-540-20396-6. 
  • Steele, J. M. (2000). Observations and Predictions of Eclipse Times by Early Astronomers. Dordrecht: Kluwer Academic. ISBN 0-7923-6298-5. 
  • Steele, J. M. (1994). Robot Evolution: The Development of Anthrobotics. John Wiley & Sons. ISBN 0-471-02622-0. 
  • Stephenson, F. R. (1997). Historical Eclipses and the Earth's Rotation. Cambridge, UK: Cambridge Univ. Press. ISBN 0-521-46194-4. 
  • Toomer, G. J. (1998). Ptolemy's Almagest (trans. Toomer, G. J.). Princeton, New Jersey: Princeton Univ. Press. 

JournalsEdit

  • Bromley, A. G. (1985). "The Design of Astronomical Gear Trains". Horological Journal 128 (6): 19–23. 
  • Bromley, A. G. (1986). "The Design of Astronomical Gear Trains (b)". Horological Journal 128 (9): 10–11. 
  • Bromley, A. G. (1986). "Notes on the Antikythera Mechanism". Centaurus 29: 5. Bibcode:1986Cent...29....5B. doi:10.1111/j.1600-0498.1986.tb00877.x. 
  • Bromley, A. G. (1990). "The Antikythera Mechanism". Horological Journal 132: 412–415. 
  • Bromley, A. G. (1990). "The Antikythera Mechanism: A Reconstruction". Horological Journal 133 (1): 28–31. 
  • Bromley, A. G. (1990). "Observations of the Antikythera Mechanism". Antiquarian Horology 18 (6): 641–652. 
  • Charette, François (2006). "High tech from Ancient Greece". Nature 444 (7119): 551–552. Bibcode:2006Natur.444..551C. doi:10.1038/444551a. PMID 17136077. 
  • Edmunds, Mike & Morgan, Philip (2000). "The Antikythera Mechanism: Still a Mystery of Greek Astronomy". Astronomy & Geophysics 41 (6): 6–10. Bibcode:2000A&G....41f..10E. doi:10.1046/j.1468-4004.2000.41610.x.  (The authors mention that an "extended account" of their researches titled "Computing Aphrodite" is forthcoming in 2001, but it does not seem to have appeared yet.)
  • Freeth, T. (2002). "The Antikythera Mechanism: 1. Challenging the Classic Research". Mediterranean Archeology and Archeaometry 2 (1): 21–35. 
  • Freeth, T. (2002). "The Antikyhera Mechanism: 2. Is it Posidonius' Orrery?". Mediterranean Archeology and Archeaometry 2 (2): 45–58. 
  • Freeth, T. (2009). "Decoding an Ancient Computer". Scientific American 301 (6): 76–83. doi:10.1038/scientificamerican1209-76. PMID 20058643. . See also abstract.
  • Freeth, T.; Bitsakis, Y., Moussas, X., Seiradakis, J. H., Tselikas, A., Mankou, E., Zafeiropulou, M., Hadland, R., Bate, D., Ramsey, A., Allen, M., Crawley, A., Hockley, P., Malzbender, T., Gelb, D., Ambrisco, W., & Edmunds, M. G. (2006). "Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism". Nature 444 (7119): 587–591. Bibcode:2006Natur.444..587F. doi:10.1038/nature05357. PMID 17136087. 
  • Jones, A. (1991). "The adaptation of Babylonian methods in Greek numerical astronomy". Isis 82 (3): 440–453. doi:10.1086/355836. 
  • Morris, L.R. (1984). "Derek de Solla Price and the Antikythera Mechanism: An Appreciation". IEEE Micro 4: 15–21. doi:10.1109/MM.1984.291304. 
  • Price, D. de S. (1959). "An Ancient Greek Computer". Scientific American 200 (6): 60–67. doi:10.1038/scientificamerican0659-60. 
  • Price, D. de S. (1974). "Gears from the Greeks: The Antkythera Mechanism – A Calendar Computer from ca 80BC". Trans Am Philos. Soc., New Series 64 (7): 1–70. doi:10.2307/1006146. 
  • Price, D. de S. (1984). "A History of Calculating Machines". IEEE Micro 4: 22–52. doi:10.1109/MM.1984.291305. 
  • Spinellis, Diomidis (May 2008). "The Antikythera Mechanism: A Computer Science Perspective". Computer 41 (5): 22–27. doi:10.1109/MC.2008.166. 
  • John A. Koulouris,(Esq.) (2008). "The Heavens of Poseidon: The History and Discovery of the AntiKythera Mechanism (In GREEK)]". IN NOMINE Portal 1: 1–12. 
  • Steele, J. M. (2000). "Eclipse prediction in Mesopotamia". Arch. Hist. Exact Sci. 54 (5): 421–454. doi:10.1007/s004070050007. 
  • Weinberg, G. D.; Grace, V. R., Edwards, G. R., Robinson, H. S;, Throckmorton, P., & Ralph, E. K. (1965). "The Antikythera Shipwreck Reconsidered". Trans Am Philos. Soc. 55 (New Series) (3): 3–48. doi:10.2307/1005929. JSTOR 1005929. 
  • Zeeman, E. C., (1986). "Gears From The Ancient Greeks". Proc. Roy. Inst. GB 58: 137–156.  (See also the slides from a lecture here [1], slide 22 is a view of how the mechanism for a model comes to replace actual reality).

OtherEdit

  • Cousteau, Jacques (1978). The Cousteau Odyssey: Diving for Roman Plunder (Tape). Warner Home Video/KCET, Los Angeles. 
  • Hellenic Ministry of Culture and the National Archaeological Museum, The Antikythera Mechanism Research Project
  • Rice, Rob S. (4–7 September 1997). "Physical and Intellectual Salvage from the 1st Century BC". USNA Eleventh Naval History Symposium. Thessaloniki. pp. 19–25.  see The Antikythera Mechanism

External linksEdit