References: Letter to nature(444 30 November 2006) Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism

References:

Letter to nature(444 30 November 2006) – Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism.

www.antikythermechanism.gr

Technology is always advancing and can be used for an immense number of applications ranging from the most mundane to the extremely intensive. In today’s world society tends to associate technology with electronic circuitry, computers, micro-chips etc, however thousands of years before the discovery of electricity this digital image doesn’t hold. Currently, information regarding the cycles of the universe is calculated by using complex algorithms in computer programs and with the help of fast processors to do the calculations, so how did our ancestors manage to do the same with the aid of a mechanism the size of a shoe-box? Could it be possible that in decades of advances in computer science and understanding of our universe we have only managed to verify what could’ve already been known thousands of years ago?

As with most great discoveries, this landmark in historical knowledge was found almost by accident by deep sea sponge divers almost a hundred years ago. The fragments retrieved were terribly eroded and managed to hide their true meaning very well. For years scientists thought that perhaps it was an astronomical clock or perhaps an astrolabe. Only very recently have researchers built on previous research using the very latest techniques to reveal the true history of these priceless fragments. The secrets slowly unfolded to reveal that the remains were indeed part of a complex astronomical computer which is known as the Antikythera mechanism.

Ascertaining the name and overall function of this mechanism is all very well and good but what was it used for exactly and what features did it posses? Today’s research team together with established companies specialising in X-ray and digital imaging have managed to accurately replicate the various components of the system using the authentic fragments. More importantly the inscriptions can also be seen enabling researchers to create a more complete overall picture of the mechanism and eventually be able to reconstruct a working model. Historically, it seems, our ancestors could well have been more advanced than ever previously imagined and the results of all this research is living proof of that.

The ancient Greeks used to rely heavily on celestial information in order to plan agricultural activity or to organise religious festivals. Various events such as eclipses and solar motion were often philosophically interpreted and used to sometimes explain phenomena occurring in the world. Hipparchos developed a theory explaining the irregularities of the Moon’s motion due to its elliptical orbit and the mechanism uses this theory to track that particular motion. The complexity of the device is thus well acknowledged, but knowing how important it was to the ancient world has helped in understanding its various functions and decoding the complex gearing.

From the remaining fragments found it’s been determined that it was most probably fabricated from bronze, hand driven and encased in a wooden box. The structure could go some way in explaining how these pieces have survived so many years near the bottom of the ocean. The inscriptions were difficult to read having been smoothed down by corrosion but one of the first pieces of text to be decoded was the word ‘Sterigmos’ meaning stationary point. So perhaps this indicated how a planet’s apparent motion changed direction in reference to this point. Also the numbers found near the text could well be related to planetary cycles.

It seems the research is on the right track but there are more fragments which have been badly affected by corrosion and until recently even their original functions couldn’t be determined let alone the inscriptions written on them. This is where modern technology has exponentially increased the development in this research. Three dimensional X-ray microfocus topography developed by X-Tek systems and digital optical imaging developed by Hewlett-Packard have been able to not only clearly see the fragments but have been able to hypothesise and reconstruct the original components. A more complete picture of the device can now be constructed and from that the positioning and function of the mechanism’s functions can be deduced.

The front of the mechanism is dominated by a dial displaying the positions of the sun and the moon. There are two scales with the inner one showing the Greek zodiac and the outer scale is a calendar depicting the Egyptian names of the months with Greek letters. The latter could be moved around, the purpose of which was to correct the effect of an extra quarter day by turning the scale one day every four years.

To the rear of the device there are dials most probably used as an eclipse function with inscriptions in order to predict solar or lunar eclipses. The Greek letters Sigma and Itta depicted a lunar eclipse and a solar eclipse respectively. All modern eclipse data matches the sequence of eclipses which would’ve occurred during the period in which the mechanism was used.

By taking a further look at the individual components and gears, the number of teeth helped determined their exact functions and extensive digital imaging has shown that the main dials had a pointer which followed a groove therefore being able to be reset once the pointers reached the centre of the dials. This tooth count was determined by taking angular measurements from the centre to the remains of the tooth tips. The software has helped to reconstruct and speculate what the complete component would’ve looked like. In cases when it was unclear adjustments had to be made as to where the centre was set in order to find the best fit solution.

When it came to construct the gear linkage between the dials and the handle that drives the mechanism, at first four gears were missing probably due to the lack of appropriate fragments. A complete reconstruction using the remaining gears was proposed and only the assumption of one further gear was needed. Recently using this research other groups have managed to create fully working models of the Anitkythera mechanism.