Price Identifies an Ancient Astronomical Computer Summary

  • Last updated on November 10, 2022

The studies of Derek de Solla Price on a corroded, ancient Greek mechanism showed that the technology of the ancient world was much more advanced than had previously been recognized.

Summary of Event

In the early spring of 1900, a party of Greek sponge fishermen were returning home from their fishing grounds off North Africa when they were driven off course by storms and took refuge off the island of Antikythera, between the southern tip of mainland Greece and the island of Crete. After the storm abated, they decided to try diving for sponges in this unfamiliar site. At a depth of 42 meters, diver Elias Stadiatis Stadiatis, Elias found the remains of an ancient ship and returned to the surface with the arm of a bronze statue. After carefully noting the location of the site, the divers returned to their home port and spent the next six months deliberating on what to do about their find. They finally decided to report the find to the authorities and did so on November 6. Computers;ancient precursors Astronomy;ancient astronomers Antikythera Mechanism [kw]Price Identifies an Ancient Astronomical Computer (June, 1959) [kw]Ancient Astronomical Computer, Price Identifies an (June, 1959) [kw]Astronomical Computer, Price Identifies an Ancient (June, 1959) [kw]Computer, Price Identifies an Ancient Astronomical (June, 1959) Computers;ancient precursors Astronomy;ancient astronomers Antikythera Mechanism [g]Europe;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] [g]Greece;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] [c]Astronomy;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] [c]Computers and computer science;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] [c]Science and technology;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] [c]Archaeology;June, 1959: Price Identifies an Ancient Astronomical Computer[06110] Price, Derek de Solla[Price, Derek desolla Stais, Spyridon Svoronos, Joannes N. Rehm, Albert

The Greek authorities acted quickly. The divers were hired to recover artifacts from the wreck, and a naval vessel was detailed to support the expedition. This was the first submarine archaeological investigation. Diving continued from late November, 1900, until September 30, 1901, without benefit of any underwater breathing apparatus. Divers could remain submerged for only a few minutes at a time, and because of the great water depth, could dive only twice a day. Free diving (without breathing devices) in such deep water is very dangerous; one diver died and two were permanently disabled during the operations.

The wreck yielded many amphorae (oil jars) and marble and bronze statues, which eventually allowed archaeologists to date the shipwreck at about 65 b.c.e. During the reassembly of the large bronze statues, small unidentified pieces of bronze were kept in a storage area until they could be fitted into place. On May 17, 1902, Spyridon Stais noted that one of the scraps bore an inscription. Further study by Joannes N. Svoronos revealed the imprint of gears in the corroded bronze. Additional scrutiny revealed portions of several rotating dials. The nature of the device was the subject of immediate controversy. Some researchers considered the device to be an astrolabe (an early navigation instrument). Others considered the gearing far too complex for such a device and argued that it was part of a water clock or planetarium of a sort described by ancient writers, but not previously known to have survived. A few scholars argued that the device was so complex it could not have been ancient, but must have been lost on the site of the shipwreck at a much later date.

Over the next half century, additional descriptions of the device, which came to be called the Antikythera Mechanism, were published by researchers such as Ioannes Theophanidis Theophanidis, Ioannes and Albert Rehm. Although additional details of its construction were clarified, little new insight into its function resulted. In 1951, the device attracted the attention of Derek de Solla Price, a historian of science with an interest in time-keeping devices. He studied newly available photographs of the artifact and was able to examine the device in person in 1958. Based on analysis of the visible gears in the device and the inscriptions on it, he concluded that it was a computing device for calculating the positions of the Sun and Moon; the results were published in June, 1959.

A diagram showing the complex inner workings of the reconstructed Antikythera Mechanism.





Despite Price’s studies, too little of the device was visible for a detailed reconstruction of its action. After two thousand years in seawater, the original bronze had altered to a mass of copper and tin compounds, and it was impossible to dismantle the object. In fact, the mechanism was in several pieces and some of it had crumbled away. Price considered X-raying the device, but initially no suitable facilities were available. In 1971, Price learned of an alternative technique, gamma radiography, Radiography, gamma Gamma radiation which used a small amount of radioactive material as a radiation source. With the cooperation of the Greek Atomic Energy Commission, Atomic Energy Commission, Greek gamma radiographs were made in 1971. Eventually, X-ray photographs were made.

The radiographs revealed a total of twenty-two gears in four layers, which formed part of a compact apparatus originally measuring about 15 centimeters wide and 30 centimeters high. The gears had triangular teeth, easy to fabricate by hand with a file, but less efficient than modern gear design. The Antikythera Mechanism is the only complex mechanical device known to have survived from antiquity.

Although the radiographs helped enormously in interpreting the device, they did not answer every question. None of the gears was complete enough or visible enough to allow an unambiguous count of their teeth. Because the gears are not perfectly circular and the teeth are not perfectly uniform in spacing, the tooth counts could be off by one or more teeth for some gears. A difference of one tooth (47 versus 48 or 127 versus 128 teeth) can be of considerable significance in interpreting the astronomical function of the clock. Fortunately, it is possible to rule out many alternative gear schemes, because they conflict with the arrangement of other gears or dials on the device.

The Antikythera Mechanism was driven by a shaft that entered one side of the device. The shaft turned a toothed drum, or contrate gear, which in turn meshed with a large gear at right angles to the shaft. Five turns of the shaft resulted in one turn of the main drive gear, which represented a year. The other gears were used to display the positions of the Sun and Moon on dials. Letters on one of the dials appear to correspond to a list of heliacal risings and settings of major stars, a common timekeeping device in ancient calendars. Heliacal rising is the first appearance of a celestial body before sunrise; heliacal setting is the last appearance of an object after sunset.

The gear ratios in the device show that it was used to simulate several major solar and lunar cycles. The phases of the Moon fall on the same date after an interval of nineteen years. This cycle, the Metonic cycle, was known in antiquity. Nineteen years corresponds to 254 sidereal revolutions (revolutions of the Moon with respect to the stars), and the Antikythera Mechanism is geared to reflect these cycles.

Because a whole number of years occur in the Metonic cycle, after each cycle Earth, the Sun, and the Moon have the same positions relative to the stars. The Moon makes 235 revolutions with respect to the Sun (synodic revolutions) in a Metonic cycle. That is, there are 235 lunations, or intervals from new moon to new moon, in a Metonic cycle. It is physically possible that other planetary motion gears could have fitted within the space available in the device, but no such gears survived.

The 235 revolutions are the most startling feature of the Antikythera Mechanism. It would be possible to produce this cycle with a separate gear, but there are no gears with the necessary number of teeth. The device actually produces the cycle by subtracting the 19 revolutions of one gear from the 235 revolutions of another. It was not previously suspected that such an arrangement, called a differential gear Differential gears , had been known in antiquity. The earliest differential gear known before Price’s study dated from 1575, more than sixteen hundred years later than the Antikythera Mechanism.


The study of the Antikythera Mechanism has shown that ancient technology was capable of much more sophistication than anyone had hitherto suspected. The Antikythera Mechanism was not an attempt to model the physical behavior of the heavens. Instead, it was a mechanized version of mathematical formulas used for predicting the cycles of the Sun and Moon. In modern terms, it was a mechanical calculator or analog computer. The exact purpose of the device is still unknown. It may have been used as a portable calculating device. Alternatively, it could have been part of a larger display in a temple or other public building, as other timekeeping devices of the period were. It was definitely not a navigation instrument for the ship, but an artwork like much of the rest of the cargo.

A device as complex as the Antikythera Mechanism cannot have been an isolated creation. It verified an extensive and elaborate gear-making tradition. The impression of the ancient world created by its most imposing artifacts (statues and buildings) is incomplete. The lack of perishable materials (paper, cloth, wood, and even most metal) creates an erroneous impression of a lack of advanced technology. To some extent, this lack is filled by ancient writers who have left descriptions of mechanical devices, yet even these descriptions are incomplete. Often they were written by members of the educated class, who may have been intrigued by the devices but lacked the technical expertise to describe them correctly.

Even in the few cases of writings left by ancient technologists, the record is incomplete. For example, the Roman military engineer Vitruvius has left one of the best records of ancient technology, but it mostly concerns heavy military engineering. Someone like Vitruvius would be unlikely to have described the Antikythera Mechanism. The apparent lack of ancient advanced technology often has been attributed to slavery; as Price notes, the Antikythera Mechanism “gives the lie to an historical theory that has long been outworn and is now unworthy of serious consideration.”

The Antikythera Mechanism and the rare devices related to it that have survived from later times help solve the mystery of one of the modern world’s most fundamental devices. One of the salient features of Western European civilization is its emphasis on time and timekeeping. Mechanical clocks appeared abruptly in history, fully developed and highly sophisticated. Indeed, some of the most complex clocks in existence are among the earliest. If clocks are regarded solely as timekeeping devices, they appear to have come mysteriously from nowhere. Many early clocks, however, included astronomical displays, and these devices, as the Antikythera Mechanism shows, have a very ancient history. Thus, it appears that clocks, so influential in regulating the modern world, evolved out of astronomical mechanisms. Their development was stimulated more by a desire to model the movements of the heavens rather than simply to keep time. Computers;ancient precursors Astronomy;ancient astronomers Antikythera Mechanism

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">De Camp, L. Sprague. The Ancient Engineers. Garden City, N.Y.: Doubleday, 1963. A comprehensive survey of technology from earliest times to the beginning of the Renaissance, written in nontechnical language. De Camp makes extensive use of the writings of ancient technologists and briefly describes the Antikythera Mechanism.
  • citation-type="booksimple"

    xlink:type="simple">North, J. D. “The Astrolabe.” Scientific American 230 (January, 1974): 96-106. A summary of one of the most beautifully crafted and deeply ingenious ancient scientific instruments. For a time, the Antikythera device was thought to be an ancient astrolabe.
  • citation-type="booksimple"

    xlink:type="simple">Price, Derek de Solla. “An Ancient Greek Computer.” Scientific American 200 (June, 1959): 60-67. The result of Price’s first detailed analysis of the Antikythera Mechanism. Although made without benefit of radiography, Price’s study was confirmed largely by his later work. This article contains a number of diagrams showing the probable original design of the Antikythera device.
  • citation-type="booksimple"

    xlink:type="simple">_______. Gears from the Greeks: The Antikythera Mechanism, a Calendar Computer from c. 80 B.C.E. New York: Science History, 1975. A reprint of a lengthy journal article in which Price describes his findings. Includes many radiographs and diagrams of the gear arrangements as well as a thorough history of investigations into the Antikythera Mechanism. By far the most thorough account of the mechanism.
  • citation-type="booksimple"

    xlink:type="simple">_______. “Piecing Together an Ancient Puzzle: The Tower of the Winds.” National Geographic 131 (April, 1967): 586-596. A description of a building in Athens that once housed an elaborate public timekeeping display. Although the device in this building probably was not similar to the Antikythera Mechanism, the investigation nevertheless sheds light on the use of mechanical timekeeping devices in the ancient world.
  • citation-type="booksimple"

    xlink:type="simple">Woods, Michael, and Mary B. Woods. Ancient Computing: From Counting to Calendars. Minneapolis, Minn.: Runestone Press, 2000. Written for middle-school students, but one of the only texts entirely devoted to ancient computers. Includes discussion of the Antikythera Mechanism.

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