Astronomy in Travelling

In order to bear to windward, away from the land, ancient mariners had to orient. Kalypso's guidance to Odysseus: "Look, Odyssey, as you travel, have on your left the star which is named Ursa Major", shows us how important was the progress of astronomy for travelling. One of the most impressive inventions of ancient times was "Anticythera Mechanism", which finally proved to be not an astrolabe, but an astronomic calculator.

The Antikythera Treasure

It was found by some sponge-fishermen Symi (a greek island) at 1901, inside a shipwreck from roman ages, near to Anticythera. The ship was full of art treasures (statues, jewellery, amphoras, furniture etc), and was heading from Rhodos to Rome and its load would probably decorate the villa of some Roman citizen. Among the findings of the famous "Antikythera Treasure" (big part of which is now placed in the Archaeologic Museum of Athens) is a unique astronomical circle, an articraft, known as the "Antikythera Mechanism". In the beginning, this important finding passed unobserved and 8 months passed until the pieces with the clear traces of the cogwheels and illegible writing actually catched the attention of the specialists. However, the long stay inside the sea and the bad conservation due to lack of experience, destroyed a big part of the mechanism, which made difficult the researchers' work.

Studying the Mechanism

With the first studies, two streams dominated: the one claimed that it was some kind of astrolabe ( N. Sroronos, Rediadis) and others that it was a more complicate mechanism (K. Rhados, I. Theofanidis). Professor Stais was the first to perceive its use and Dean Meritt found that it was from the 1st century BC, by examinating its handwriting. In the researching center Dimocritos, at 1951, professor Derek de Solla Price from the University of Yale and professor of nucleonics Haralambos Karakalos, examined the astrolabe with radials X and gamma (radiograph) and found this mechanism was suprisingly complicated, especially because of its old age. Finally, Derek de Solla Price completed his study and at 1974 he publiced his famous book for the Antikythera Mechanism.

Schematic of the mechanism

After its pulling up and many inobservances, adventures and faults, 4 parts were salvaged from the mechanism, which were named a, b, c, d from Derek de Solla Price. In it, there were 30 different handmade cogwheels, with diameters varying from 9 to 132mm. There were indices that showed the route of the Sun and the phases of planets in the zodiac. Everything was placed in a wooden box, that closed with front and back lockers, and external larks. Upon the larks and the frame there were texts in greek that were istructions and indications. In the front part there were two concentric discs with date indications having to do with the sun's position, and a date having to do with the moon. In the bigger disc that's in the front part, the months of the year are noted, while others noted the movement of the Sun inside the zodiac, as well as the annual routes of stars and constellations. In the back there were two discs - the one counted the days of the moon month, and the other did the calculations for the eclipses of the moon. All these may seem simple, but calculations like these need numbers with 6 decimal points. According to Derek de Solla Price there were initially two different mechanisms, one in the front lark and one in the back, which were both independent from each other.

Another technical application was the use of a differential system of movement from one entrance to two exits. English scientist Derek de Solla Price, that studied this calculator for 23 years ascertained the existence of a complicated system of different rotations. In the Antikythera Mechanism, the differential is used in such a way that it allows the correlation between the sessional data and the astral ones. As Derek de Solla Price mentions, it is a machine calculating a calendar of the Sun and the Moon. Its most advanced characteristic is an astonishing complicated system of a differential cogwheel.

Most of the epigraphs in the mechanism cannot be read at all due to the corrosion. Unfortunately, only in two of the saved parts the conversed text is big and clear: in the big part of the board and in the bottom part of the back entrance. The identifications that come from them, as, for example, the writing amplify the dating of the shipwreck and the construction of the machine, because they are characteristics of the 1st century BC.

The Construction

It was probably constructed in Rhodos, in the Apollo's school, and was an astonishing circle, unique in the history of worldwide technology. It is the most complicated known mechanism until 1200 AC. There have been, though, reports for a mechanism that showed the movement of the Sun and the planets (it would be the first planetarium), but only a few believe that the mechanics at this age (80 BC) had the appropriate tools and knowledge to construct mechanisms of such complexity. The Antikythera Mechanism had many metallic circular cogwheels placed in such a way that the movements of some planets were emulated. Who and how someone would construct it with such astronomical knowledge and accuracy at this time remains a mystery. The analysis shows that it was an mechanical astronomical calculator.

We have very little information for the ability of construction of complicated mechanisms from cogwheels, because we don't have a clear mentioning to the cogwheels until the alexandrian mechanic Heronas. However, there are indications that suggest Archimedes or Ktesibios as possible inventors of the cogwheel. Archimedes is well-known for his complicate constructions that represented the movements of the stars and the planets in the welkin, but we only know about the functions that were used, not how they were used. Probably their way of function would be similar to the Antikythera Mechanism. The famous Sphere of Archimedes is mentioned by Pappos, Proclus, Sextus, Ebeirikus, Firmikius, Martianus, Kapella, Obidius and Tertullianus, but the most important witness is given by Cicero. In the most primitive evolutional stages of similar mechanisms, we find that the solar clocks had a great complication, because they tried to count not the time, but the phases of the moon and the movements of stars.

Complicacy and Similar Mechanisms

We don't encounter anything similar in any other mechanical construction until the 19th century AC! Mathematician Dionysis Criaris studied and reconstructed a model of Antikythera Mechanism, as Derek de Solla Price had done before. In the Archaeological Museum of Athens, apart from the parts of the mechanism found in the shipwreck, there is also a draft of the Antikythera Mechanism.

A similar mechanism has not been found anywhere else. At around 500 AC we encounter a similar construction in the Byzantium that would calculate with some kind of mechanism positions of the Sun, the Moon and planets for some geographical places. Its construction seems to be simpler and fortunately it is saved in relatively good condition in the Museum of Science in London, where it was studied and reconstructed by J. Field and M. Right.

Later enough, at about 1200 AC, we encounter a similar construction from Arab astronomers, who, developping the science of astronomy, used astrolabes of similar functions. Similar mechanism is described by Arab Al Birouni. A big percentage of the technological coquests in this domain were made by Arabs. As it is also known, many ancient greek testimonies have been saved only in arabic translations. Arabs experimented with different various design and constructions in order to prove the correctness of the greek texts.

The technology of the cogwheels evoluted and flourished at the 13th and 14th century. Especially for the differential cogwheel, that is the most astonishing finding due to its mechanism, it has do be mentionned that it reappeared many centuries later.

This instrument of astonishing beauty and scientific apprehension, is the quintessence of tradition to the cogwheels, developped during the hellenistic period. The Antikythera Mechanism is an extraordinary result of application of the science in action: Mathematics, Geometry, Astronomy and Mechanics. Not only the complicacy but also the astonishing accuracy of the construction shows us that it was not constructed by chance, but it was a product of evolution and it should have been based in an elder mechanism, maybe from some proving ground that constructed similar mechanism. The great accuracy in the cut of the cogwheels shows the high abilities of the metal working of the first century BC. It is claimed that the "Uranian Sphere" or the "Uranian Pole" of Archimedes was its ancestor. Unfortunately, we don't know its constructor. According to Arthur Clark, if the evolution of knowledge, as depicted in the Antikythera Mechanism, had not been cut in the middle, science would be a million years in front of its time!