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Abstract

The main dials of the back face of the Antikythera Mechanism have partially survived together with the pointer of the upper dial and a few remains of the mechanism that supported and rotated it. The reconstruction of this mechanism, described in this article, fits perfectly its description in the Mechanism’s inscriptions. Our results also show that both spirals were Half Circles spirals, drawn from two different centres. The unwanted eccentricity that would be produced from the pointer’s being placed at one of the centres is proven to have been ingeniously avoided with the appropriate drawing of the cell divisions.

Keywords

Division of circular scale Archimedean spiral eccentric pointer Greek inscriptions half circles

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References

de Solla Price

, “Gears from the Greeks: The Antikythera Mechanism – A calendar computer from ca. 80 B.C.”, Transactions of the American Philosophical Society, n.s., lxiv/7 (1974) (reprinted New York, 1975). Also: Freeth

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, “X-ray tomography of the Antikythera Mechanism”, in Proceedings of science (PoS), From Antikythera to the Square Kilometre Array: Lessons from the Ancients, Kerastari, Greece, 12–15 June 2012, published online at http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=170

Price (“Gears” (ref. 1)) originated this idea, but did not pursue it; Wright

M. T.

in “Epicyclic gearing and the Antikythera Mechanism, Part I”, Antiquarian horology, xxvii (2003), 270–9, published a persuasive gear train to turn the Metonic Dial.

Freeth ., “Calendars” (ref. 2).

Both of these new findings were added to the 2011 Aristotle University Antikythera Mechanism Model (v2.1), that was first publicly presented at the opening of the exhibition “Science and Archaeology: The Antikythera Mechanism” in Pafos, Cyprus on 1 July 2011.

All measurements throughout this article were make using the software “VGStudio Max 2.0” Reinhardt

, VG Studio Max, http://www.volumegraphics.com/en/

The dimensions of the remains of the pointer according to Price (“Gears” (ref. 1), 15) are 55mm × 4.5mm × 2.5mm.

Price , “Gears” (ref. 1), 15.

10.

Wright , “The scholar” (ref. 2), 10.

11.

Freeth ., “Decoding” (ref. 1).

12.

A possible explanation could be that the cavities were used to smooth the motion of the pointer with grease, or even that the cavities had a decorative role.

13.

So far, none of the surviving parts of the Mechanism seems to allow for recalibration.

14.

Wright

M. T.

, “The Antikythera Mechanism and the early history of the Moon-phase display”, Antiquarian horology, xxix (2006), 319–29.

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Freeth ., “Decoding” (ref. 1).

16.

The transcription of the Greek text was made following the Leiden convention ( Woodhead

A. G.

, The study of Greek inscriptions, 2nd edn (Cambridge, 1981)).

17.

Jones

Alexander

, after seeing the reconstruction of the pointer mechanism proposed here, immediately suggested that its publication should be accompanied by the inscription describing the construction of the pointer, adding that the physical evidence and the inscription confirmed each other very well.

18.

Wright , “The scholar” (ref. 2), 10.

19.

Freeth ., “Decoding” (ref. 1), 589.

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Freeth ., “Decoding” (ref. 1), 589.

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, Polynomial texture mapping, http://www.hpl.hp.com/research/ptm/ (2006)

22.

Solver is a method that finds an optimal value for a formula in one cell (called the target cell) by adjusting the values in specified modifiable cells (the adjustable cells).

23.

As it is much more difficult to design the cells of the right half of the Saros spiral (which are gradually wider cells (§4.3)).

24.

Freeth . (“Decoding” (ref. 1)) however suggested that the Antikythera Mechanism might have been used as its own dividing engine in setting out the Saros Dial, since it was difficult at this era to divide a four-turn spiral into 223 divisions. In that case, these errors would have been generated by the gearing.

25.

Wright , “The scholar” (ref. 2), 10.

26.

Evans

Carman

C. C.

Thorndike

A. S.

, “Solar anomaly and planetary displays in the Antikythera Mechanism”, Journal for the history of astronomy, xli (2010), 1–39.

Supplementary Material

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The Antikythera Mechanism: The Construction of the Metonic Pointer and the Back Plate Spirals

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