The Antikythera Mechanism
By: Ella Alderson
Tags: Astronomy, Space, History, Science, Mathematics

In Ancient Babylon, it is believed lunar eclipses are a message for the king. Whether the message brings good fortune or impending death depends upon how much of the moon is lost in shadow and where the other stars and planets lie in the sky. If the message is thought to be an omen of chaos and death, a strange custom is set into play. The king officially steps down from his throne, giving it to a substitute king — often a criminal — who is bathed, anointed with oil, and fed cooked birds and wine. Rulers like Alexander the Great wait for the eclipse to pass. It is thought that all misfortune befalls the temporary king as the moon is moth-eaten by a fiery red or an incandescent orange. Important signs are written down during the eclipse. Anomalies in the sky or the Earth. Birth defects among the mothers. Once the eclipse is over, the substitute king is killed and many of his possessions are burned to purify the land. Alexander returns to his throne.

This is one of many examples detailing mankind’s fascination with the skies — it color, its composition, the spectacles that take place against the blue backdrop. But it wasn’t until the discovery of the Antikythera mechanism that we realized just how early on we were able to understand events as complex as eclipses or the motion of the moon. It is a mystery still being unravelled today. A strange object, lost at the bottom of the ocean for over 2,000 years, bearing hidden inscriptions and a pattern of numbers that took decades of studies to decode. It has possible ties to Archimedes, the most famous mathematician of ancient Greece, and is a technology many researchers believe to have been impossible for that day and age. If the dating of the Antikythera Mechanism is correct (originally thought to be from around 70 BC but the artifact could be from as far back as the second century BC), then similar technology isn’t seen again for thousands of years. It’s the kind of intricate ingenuity common of the 16th century. So ahead of its time that it’s often referred to as the world’s first analog computer.

The discovery begins in 1900 when a sponge diver finds a shipwreck near the Greek island of Antikythera. Lying hundreds of feet deep in the ocean are the scathed, battered faces of men, their arms sunken crookedly into the sand a few feet away. It is the resting ground of one of the largest collections of marble and bronze sculptures ever discovered, with many masterpieces recovered from the scene. There is glassware, rusted coins, glints of jewelry and broken pots that would have carried wine. But when the diver resurfaces to tell the captain what he’s found, he’s met with disbelief. The story is so incredible that the crew assumes the diver must have been hallucinating due to an accumulation of nitrogen in his helmet. It’s not until 1902 that an archeologist inspecting artifacts from the wreck comes across the Antikythera mechanism.

The three largest pieces of the artifact are on display, with the main gear seen in the center. It resides at the National Archeological Museum in Athens and was theoretical physicist Richard Feynman’s favorite piece in the collection.

It’s unimpressive at first. Just three fragments of corroded bronze, all in different shades of damp green or gray. It was because of the corrosion that it was difficult to see the gears and rings inside, with dials punctuating an outer case measuring just over a foot long. Many believed it to have little importance and so true progress isn’t made until the 1970’s and 1990’s when physicists, historians, mathematicians, and astronomers begin to detail and x-ray the mechanism.

Even before the real mysteries arose, researchers knew it must be used to track astronomical events. In the pieces recovered, there are about 30 masterfully calibrated gears with up to 60 gears likely to have been inside the full mechanism. The gears — which in turn move seven hands at different speeds — were operated by a single crank on the side. Once a user chose a date, dials and clock faces would reveal the movements of the sun, the moon, the stars, and five different planets for the chosen day. The only planets visible to the naked eye are Mercury, Venus, Mars, Jupiter, and Saturn. These planets would have been represented by small, colored glass balls while a separate silver ball would have turned to display the phases of the moon. In fact, the mechanism could predict a series of complex astronomical phenomena: the rising and setting of the stars, solar and lunar eclipses, the relationship between the moon, sun, and the 12 astrological constellations, a 365 day solar calendar and 19 year lunar calendar. It’s this lunar aspect that’s particularly impressive.

Amongst a backdrop of parallel universes, black holes, and quantum entanglement, the orbit of the moon may seem like a rather unextraordinary event. It may even come across as a simple thing to calculate, but even something as familiar as the moon involves layers of math and meticulous attention to detail. Modeling future orbits, as the Antikythera Mechanism did, involves taking into account the Saros cycle (a period of 223 months after which lunar eclipses begin to repeat), the hour at which the eclipse will occur decades in advance, the 9 year periodical rotation of the moon’s elliptical path, and the moon’s varying speed as it’s positioned either closer or farther from the Earth. The moon’s speed is accounted for by a small pin within the gears. The 9 year elliptical path rotation is mathematically engrained in a gear with 53 teeth that divides into the number 0.112579655 — an accurate calculation of the extremely subtle path rotation. Planetary motion was similarly accurate to one degree every 500 years.

A computer reconstruction shows what the device would have looked like in its day. The crank for turning the gears, as well as a representation of the geocentric cosmos, is seen on the left. The mechanism tracked the seasons, festivals like the Olympics, and it might’ve been used in navigation and mapping. Image by NIKOS NIKOLOPOULOS.

A hidden inscription of over 3,000 Greek characters was found during CT scans in 2006. The inscription described colored balls on the now-missing planetary pointers, with red for Mars and a gold color dedicated to the sun. The writing also spoke of the mechanism’s ability to predict the eclipse color, size, and any associated wind patterns. The color would have been important to the ancient Greeks in discerning benign from treacherous omens. It was, in a way, an opportunity to peer into the future even if it was first and foremost a scientific instrument to teach about the cosmos.

The inscriptions also gave clues for two other mysteries surrounding the object. A calendar with month names could be traced back to Corinth and its northwest colonies. Among these colonies was Syracuse, where Archimedes lived. Credited with the first calculation of pi, the volumes of spheres, and the distance from the Earth to the moon, he was a brilliant mathematician and inventor. Cicero’s writings tell of Archimedes’s astronomical machine, an invention which closely resembles the Antikythera Mechanism. But if researchers are correct, then the inscriptions are the mark of two different people, possibly done in a workshop or a family business. The mechanism could be based on Archimedes’s older designs. As for the fate of the original machines, bronze was precious at the time and prone to being recycled.

Certainly it would have taken a mind as great as Archimedes’s to craft such an artifact. Its ingenious blueprint and its out-of-place conception in the world have given rise to speculation of aliens sharing their secrets with the ancient Greeks. But there’s no need to look for an otherworldly explanation. It was these same people that laid significant foundations for our understanding of the natural world — the science, the mathematics, the geometry and the art. The Antikythera mechanism offers a chance to rewrite the development of technology over the years. It would seem mankind has been capable of greater creations much earlier than we thought possible. It makes one wonder what history would be re-written if we could take back events like the burning at Alexandria. Or if we could explore more murky, patient shipwrecks out at sea.