After decades of research, a discrete find recovered from a Roman shipwreck turned out to be a scientific sensation: the ancient Greeks had mechanical models of the cosmos of unimaginable precision. The so-called “Antikythera mechanism” is an analog calendar computer.
Thomas Weibel / Swiss National Museum
In May 1902, when the Greek Minister of Education, Spyridon Stais, collected a badly corroded piece of bronze that had not yet been examined in detail at the National Archaeological Museum in Athens in May 1902, something unfortunate happened: a piece of the piece it broke. – reveals a surprisingly well-preserved gear with teeth only 1.5 millimeters high, as would be expected in a modern clockwork mechanism.
However, the lump came from the remains of a Roman ship that sank around 70 BC. It sank in a bay on the island of Antikythera, off the southern tip of Greece, in 1900 and was discovered by sponge divers. The wreck carried war loot from the eastern Aegean and Asia Minor, marble and bronze statues, ceramic and glass vessels, jewelry and coins dating from 70 to 62 BC Allowed.
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A precision gear from ancient times was a real shock to science. What the hell was that? British physicist and science historian Derek de Solla Price found the answer in the 1950s. “Price understood that the original device was flat and rectangular, about the size of a modern table clock, and had a knob or crank on the lateral,” says London mathematician Tony Freeth.
And further: “A complicated train of gears inside the casing moved a series of hands on round dials on the front and back of the device. In this way the positions of the sun and the moon could be represented exactly. For a certain day and sometimes exactly at the time of day.” Because the names of the celestial bodies are engraved on the mechanism, many researchers even speculate, although no piece of said gears has been preserved, about the position indications of the five planets known at that time: Mercury, Venus, Mars, Jupiter and Saturn.
It has long been known in literature that the ancient Greeks built these types of gear trains. In the 1st century BC The scholar Poseidonius worked on the island of Rhodes in 200 BC. C., and the lawyer and later Roman consul Cicero saw a device that «cuius singulae conversions idem efficiunt in sole et in luna et in quinque stellis errantibus quod efficitur in caelo singulis diebus et noctibus» (“whose individual revolutions produce in the sun, the moon and the five planets the same thing that occurs in the real sky in each day and night”) as he did around 45 BC BC in his work. “De natura deorum” wrote. No one thought it possible that this description could be understood literally.
If you want to understand what a mechanical transmission does, first examine the gears: their position, their circumference and, above all, the number of teeth. But even with the first X-ray images of the mechanism, it wasn’t easy. The photographs were not particularly clear and the gears themselves were only preserved in fragments. There was a wheel in which the radiologists thought they counted 128 teeth. 128 is a power of 2 and has no meaning for astronomy.
Price, for his part, stated that the wheel must have had 127 teeth. “127 is a prime number,” explains Freeth. «It refers to the orbit of the moon. If you watch the moon night after night, you will see that it moves across the starry sky, once every 27.3 days throughout the zodiac. Already in the 5th century BC. C., the ancient Babylonians knew that the Moon travels through the zodiac almost exactly 254 times in 19 years.” 254 is double 127, and with that Price found this precise Babylonian lunar calendar, integrated into an ancient gear with more than 30 gears .
Today, after extensive examinations of the 82 found fragments, including high-resolution metal-penetration CT scans, we know that the Antikythera Mechanism was a complex mechanical calendar made of bronze, a gear-driven analog computer, with scales and Texts about individual functions were engraved on their circuit boards.
On one side was a solar calendar with the date indicated. Embedded in one of her hands was a rotating semi-silver ball that displayed the phase of the moon. The dial had a static display of the 12 signs of the zodiac and an annular scale for the 365 days of the year, as marked by the Egyptian calendar, with 12 months of 30 days plus five additional days. This scale was sliding to allow for the additional leap day that occurred once every four years.
On the other side of the device were two more displays: at the top, a large spiral-shaped lunar calendar with the 19-year lunar cycle named after the Greek astronomer Meto. Below was the spiral display of a large eclipse calendar to show solar and lunar eclipses. And finally, within the lunar calendar display was a small four-year display of the Olympic calendar, showing the Panhellenic Games, including the change of venue.
Replica of the mechanism…Image: Ludwig Oechslin
…from Antikythera.Image: Ludwig Oechslin
Ludwig Oechslin, historian of technology and science and qualified master watchmaker, was director from 2001 to 2014 International Museum of Watchmaking in La Chaux-de-Fonds. In 2006 a new analysis of the Antikythera mechanism appeared in the journal. “Nature” Oechslin caught his attention and decided to recreate the device himself. Using a computer-controlled milling machine, he made the gears and assembled them into a replica of the ancient mechanism.
“We know from the literature that these types of gear trains existed in ancient times,” says Oechslin, “but none have ever been found. According to the latest discoveries, it can now be rightly said: The Antikythera Mechanism is an analog calendar computer and therefore a model of the cosmos of enormous precision.”
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After decades of research, a discrete find recovered from a Roman shipwreck turned out to be a scientific sensation: the ancient Greeks had mechanical models of the cosmos of unimaginable precision. The so-called “Antikythera mechanism” is an analog calendar computer.
In May 1902, when the Greek Minister of Education, Spyridon Stais, collected a badly corroded piece of bronze that had not yet been examined in detail at the National Archaeological Museum in Athens in May 1902, something unfortunate happened: a piece of the piece it broke. – reveals a surprisingly well-preserved gear with teeth only 1.5 millimeters high, as would be expected in a modern clockwork mechanism.