TECHNOLOGY

The Antikythera Mechanism

~2nd century BCE

History · Antiquity · Holocene · Meghalayan

The Antikythera Mechanism is a geared bronze instrument of ancient Greece, raised in 1901 from a Roman shipwreck off the island of Antikythera. About a third survives, in 82 fragments that include 30 corroded gearwheels. It calculated and displayed celestial information: the phases of the Moon, a luni-solar calendar, the eclipses to come, read from a spiral dial of 223 lunar months, and the four-year round of the Panhellenic Games. Those eclipses were computed, not observed, from Babylonian arithmetical cycles, so the instrument answered for dates its makers would never see. What is known of it comes mostly from imaging: surface photography and high-resolution X-ray tomography, applied in 2005, recovered the gear trains and doubled the number of legible inscriptions. The gearing holds a mechanical form of the theory by which Hipparchos explained the irregular lunar motion, and inscriptions naming the five planets known in antiquity point to a lost front display of the Greek cosmos.

Why it matters

Nothing of comparable complexity survives from the thousand years that followed, so the object measures a technical capacity the written sources of antiquity barely record: Hellenistic mechanics could embody an astronomical theory in bronze instead of merely stating it. The machine also joins two kinds of time usually studied apart, since the gearing that follows the Moon also counts the return of the Games, and the cycles of Greek institutions are read from the same train as the cycles of the sky.

Dating & uncertainty

Two lines of evidence date the instrument and they do not agree. The inscriptions and the technical context place its construction near the end of the second century BCE, while the eclipse dial carries a starting point of its own: the engraved sequence works best if its first month is a full Moon of 205 BCE, earlier than the second century in which Hipparchos is placed. Whether that epoch dates the machine or only the astronomical table it copies is unsettled, and with it whether the gearing follows the theory of Hipparchos or precedes it. The Roman wreck that swallowed the instrument is later again, so the sinking and the making are not one date.

Sources

1. Freeth et al. (2006), Nature · Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanismdoi:10.1038/nature05357
2. Freeth et al. (2008), Nature · Calendars with Olympiad display and eclipse prediction on the Antikythera Mechanismdoi:10.1038/nature07130
3. Freeth et al. (2021), Scientific Reports · A Model of the Cosmos in the ancient Greek Antikythera Mechanismdoi:10.1038/s41598-021-84310-w
4. Carman et al. (2014), Archive for History of Exact Sciences · On the epoch of the Antikythera mechanism and its eclipse predictordoi:10.1007/s00407-014-0145-5

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