The Moon Machine
It is old hat that the ancient Greeks were excellent at mathematics and astronomy. But then it comes as a surprise that they constructed sophisticated calculating machines down to the smallest detail: The more than 2000-year-old gear mechanism from Antikythera - discovered a hundred years ago - turns out to be even more complicated than expected.
It began with a violent storm: At Easter 1900, the weather drove the boat of Greek sponge divers off the rocky coast of the small island of Antikythera between Crete and Kythera. The sky finally cleared up again and the divers proved to be flexible workers who could also do their daily work in this remote location - a wise decision from an archaeological point of view.
Because at a depth of 42 meters the divers came across a Roman shipwreck. The summoned archaeologists were able to salvage numerous amphorae, marble statues and bronze figures in order to restore them in the National Archaeological Museum in Athens and present them to the amazed public.
So nothing special – after all, the Aegean Sea is teeming with sunken shiploads from the ancient Greeks, Romans and Byzantines. And so today hordes of tourists would probably shrug their shoulders at a small glass case with the inscription "Findings from Antikythera, 1st century BC." pass by and soon be forgotten - if a misshapen and completely corroded chunk of bronze hadn't also come to light.
The strange structure lay unnoticed in the National Museum for another two years until the archaeologist Spyridon Stais took care of it on May 17, 1902. The researcher meticulously cleaned the objects that had been broken into four pieces and came across something he probably least expected: gears.
While gearing techniques were well known to the ancient Greeks, they mostly used them in rather simple applications, such as pairs of gears to transmit power in windmills. But the ship that sunk more than 2000 years ago seemed to have had somewhat more complex machinery on board, the function and origin of which was soon the subject of wild speculation. "Is the Antikythera Mechanism from another world?" asked the Acropolis newspaper.
It would be more than half a century before the strange machine came back into the public spotlight. From the mid-1950s to the early 1970s, Yale University historian of science Derek de Solla Price studied the thing more closely. In 1959 he published in Scientific American the thesis that the Antikythera find was a unique, sophisticated mechanical device for making astronomical calculations - an ancient computer.
Price's x-rays in particular revealed a clockwork mechanism made up of 29 individual gears. Particularly surprising was the discovery of a component that every driver knows today - after all, it helps to compensate for the speed difference between the outer and inner wheels when cornering: The differential gear, patented in 1828 by the Frenchman Onésime Pecquer, was probably already known to Leonardo da Vinci. But nobody would have believed that the ancient Greeks were also familiar with this technique.
The numerical ratio of some gears was also amazing: the teeth, which are no longer completely preserved, must once have meshed in a ratio of 254 to 19. This corresponds - with an error of only 0.015 percent - to the ratio of the speeds of the sun and moon. Coincidence? "From what we know about the science and technology of the Hellenistic Age, such a device should not really exist"
(Derek de Solla Price) In any case, Price was convinced that he had in front of him an ancient machine for calculating the orbits of the sun and moon, possibly even of the then known planets Mercury, Venus, Mars, Jupiter and Saturn. "From what we know about the science and technology of the Hellenistic Age," Price pointed out, "such a device should not exist."
The interpretation remained controversial. In order to finally unravel the mystery of Antikythera, scientists from all over the world joined forces last year for the Antikythera Mechanism research project - including the astronomer Mike Edmunds from Cardiff University, the mathematician and film producer Tony Freeth, the physicist Yanis Bitsakis and the astronomer Xenophon Moussas from the University of Athens, the astronomer John Seiradakis from the University of Thessaloniki and the philologist and writer Agamemnon Tselikas from the National Bank of Greece.
The team used heavy equipment: a twelve-tonne X-ray tomograph was hoisted into the museum to scan the remains of the ancient mechanism. The examination of the 82 individual parts confirms the thesis of an astronomical calculating machine.
The device was probably in a wooden box measuring 32 by 19 by 10 centimeters and was made around 150 to 100 BC. built - so it is a little older than previously assumed. The number of gears also increased – the researchers working with Edmunds were now able to identify 37, of which nine remain hypothetical. Deciphering the only sparsely preserved inscriptions on the individual components was particularly exciting - the researchers sometimes had to fall back on the mirror-inverted impressions of the letters.
The researchers suspect that the clockwork was able to calculate two astronomical cycles in particular: the 76-year Callipic cycle, in which the sun and moon have the same position in the firmament, and the approximately 18-year Saros cycle, with which solar and lunar eclipses are repeated.
But who built this moon machine? The scientists do not know, but they have a suspicion of intellectual authorship: the Greek astronomer Hipparchus lived on Rhodes at the time and was already able to calculate the movement of the moon quite precisely. Perhaps the plane was en route from Rhodes to an unknown destination it was never to reach.
The wheelwork of Antikythera, which suddenly appeared out of nowhere and apparently found no successors, remains a mystery. For the researchers, however, one thing is certain: "It testifies to the extraordinary technical performance of ancient Greece, which may have been lost in the Roman Empire."
