The Antikythera Mechanism: The Two-Thousand-Year-Old Computer – Mike Beckham (2012)

Antikythera Mechanism is one of the best demonstrations of human intellect attempting to understand nature systematically. The contraption is most certainly a very complex device. It is an impressively accurate “analog model” of our then earth-centric universe. Science gives us prediction power and Antikythera Mechanism is an excellent example for how astronomical observations can be defined mathematically to reconcile lunar and solar calendars and predict eclipses with hourly accuracy using 27 gear pieces. It uses the Metonic Cyle first implemented in the Babylonian calendar and turns math into gearwheels, and gearwheels into a calendar. The Greek astronomer Meton of Athens realized that a period of 19 years is equal to 235 lunar months (6,940 days). The difference between 19 solar years and 235 lunar months is only a few hours.

X-ray technology employed in the analysis provided a non-invasive way to visualize the inner workings of the Antikythera Mechanism. The year 2012 was the centenary of the discovery of X-rays which has been a revolutionary technology in science. The discovery of the DNA molecule structure was made possible by X-ray diffraction chrystallography. Seeing inside of the Antikythera Mechanism through X-ray tomography was the key. A virtual model was produced for the Galileo Museum in Florence, Italy. The inner working is known well enough to create a LEGO model:

The Antikythera Mechanism was built like a clock. Trains of interlocking gearwheels controlled the movements of a minimum of seven pointers perfectly tracking the movements of the Sun, the Moon and the planets observable by naked eye namely Mercury, Venus, Mars, Jupiter and Saturn. Even the phases of the moon were displayed. It was a marvelous portable mechanical planetarium. While seven element solar system was displayed on one face, there was a linked two dial system on the opposite face following a gyre. One dial was pointing to the calendar and the other was pointing to solar and lunar eclipses. Perhaps the most genius design aspect of the contraption is the pin-and-slot device built to correct the epicyclic movements of the Mars, Moon, Jupiter and Saturn which required 4 gearwheels devoted to each planet.

The immediate question everybody ask is what could be the preceding model this complex mechanism was built on? There has to be a precursor. The closest gadget we know of the astrolabe was built way over 1000 years after and was much more simple. The gap in our understanding of astronomy beginning from the Babylonian and that of later civilizations must be rather big. The following TED talk by Tom Wujec is a great introduction to astrolabe. Indeed back in those days people were paying a lot more attention to sky and were more aware of movements of celestial objects. Similar to the Antikythera Mechanism, astrolabes enabled stereographic projection of the sky. Later contraptions from Byzantine Sun Dial to extremely precise chronometers used in ships to calculate longitude employed differential gearwheel technology seen in the Antikythera Mechanism.

Who might have been behind building of this complex device? Many names stand out: Archimedes of Syracuse, Posidonius of Rhodes, Hipparchus of Rhodes and Ctesibius. Archimedes and Ctesibius lived at the same time period and were aware of each others work. Using gearwheels they invented transformational gadgets including odometer to measure distances and water clocks (klepsydra) to measure time. Similarly, Posidonius who built an orrery and Hipparchus had workshops in Rhodes.

Archeological understanding of the shipwreck will give more clues on it’s maker. A shipwreck discovered off the Turkish coast the Uluburun dated back to late bronze age (14th century BC) and is the oldest ship ever excavated archeologically carrying a diverse cargo from at least seven different cultures. Excitingly, in September 2014 two separate shipwrecks were reported to be found again off the coast of Turkey and both are claiming to be even older (early bronze age) but no scientific confirmation has been made so far. Based on the cargo the ship that sank in Antikythera most certainly made a stop in Rhodes. According to Cicero Posidonius of Rhodes designed a contraption that fits to the description:

“Suppose a traveller carried into Scythia or Britain the orrery recently constructed by our friend Poseidonius, which at each revolution reproduces the same motions of the sun, the moon, and the five planets that take place in the heavens every day and night, would any single native doubt that this orrery was the work of a rational being?” — Marcus Tullius Cicero – De natura deorum, 2.34-5 (87-88)

You can view the following two part videos produced by Nature magazine when the second set of articles pdf showing the details of the mechanism was published in year 2008.

Nature video in two parts:

Jacques-Yves Cousteau carried out two expeditions to Antikythera shipwreck site. First expedition in 1953 relocated the wreck and tested an experimental underwater camera designed by the renowned MIT professor Doc Edgarton. The second expedition took place in 1976 which lasted five months. Coins discovered from the dives enabled accurate dating of the Roman ship to 70-50 BC. The ship was traveling from a port in Anatolia either Pergammon or possibly Ephesos. It made a stop in Rhodes and was predicted that was going to Syracuse. The cargo was quite outstanding and was loaded with luxury items. The vessel was clearly Roman. At that time, the Romans were fighting King Mithridates IV of Pontus in Anatolia under the command of the Roman general Lucullus. There’s a speculation that perhaps the sunken ship may have been carrying looted articles from Sinope on the Southern Black Sea.

Cousteau’s second expedition also recovered a hull plank made from elm tree so large that it must have been a very big ship and perhaps a grain carrier. Cousteau also discovered another wreck to the south of the first one. Curiously, the amphoras discovered there also matches to the date of the first ship. Perhaps this was a single very large ship a grain carrier that has never been found before. An unusually large lead anchor collar discovered in 2014 provided further evidence that the archeological site was a single very large ship carrying a cargo of 300 tons. A legendary ship of the same time period called Syracusia was built by Archimedes and could carry up to 1800 tons. In 2014, a giant bronze spear probably belonging to a life-sized warrior statue was also recovered which provided further clues that there’s still a lot waiting to be discovered in the wreck site.

You can learn more about the upcoming expedition plans from the Guardian podcast in which marine archaeologist Brendan Foley who has been exploring the site since 2012 explains recent developments. Using new diving technology including robotic submarines, and the Exosuit the wreck site is now mapped photogrammetrically. The program also hosts Dr. Serafina Cuomo, from Birkbeck, University of London working on the history of mathematics and technology in ancient Greek and Roman times, and the journalist Jo Marchant, author of the book Decoding the Heavens: Solving the Mystery of the World’s First Computer.

 

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