Antikythera mechanism: Difference between revisions

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The front dial has two concentric circular scales. The inner scale marks the Greek signs of the zodiac, with division in degrees. The outer scale, which is a moveable ring that sits flush with the surface and runs in a channel, is marked off with what appear to be days and has a series of corresponding holes beneath the ring in the channel.
 
Since the discovery of the mechanism, this outer ring has been presumed to represent the 365&nbsp;day Egyptian calendar, but recent research challenged this presumption and provided evidence it is most likely divided into 354 intervals.<ref>{{cite report |author1=Budiselic |display-authors=etal |date=December 2020 |title=Antikythera mechanism: Evidence of a lunar calendar |place=Newark, UK |publisher=British Horological Institute |website=BHI.Co.UK |url=https://bhi.co.uk/wp-content/uploads/2020/12/BHI-Antikythera-Mechanism-Evidence-of-a-Lunar-Calendar.pdf |access-date=12 December 2020 |archive-date=13 December 2020 |archive-url=https://web.archive.org/web/20201213144005/https://bhi.co.uk/wp-content/uploads/2020/12/BHI-Antikythera-Mechanism-Evidence-of-a-Lunar-Calendar.pdf |url-status=live }}</ref> Since this initial discovery, two research teams, using different methods, independently calculated the interval count. Woan and Bayley calculate 354-355 intervals using two different methods, confirming with higher accuracy the Budiselic et al. findings noting "365 holes is not plausible."<ref>{{cite report |author1=Woan and Bayley |date=February 2024 |title= An improved calendar ring hole-count for the Antikythera mechanism |url=https://arxiv.org/pdf/2403.00040 |access-date=15 April 2024 |archive-date=29 February 2024 |archive-url=https://arxiv.org/pdf/2403.00040.pdf |url-status=live }}</ref> Malin and Dickens' weighted estimate is 354.8±5.6 and conclude 354 is "by far the more likely" interval count.<ref>{{cite report |author1= Malin and Dickens |date=April 2024 |title=How Many Days in an Egyptian Year? Evidence from the Antikythera Mechanism |place=Newark, UK |publisher=British Horological Institute |website=BHI.Co.UK |url=https://bhi.co.uk/wp-content/uploads/2024/04/04-HJApril24-AOTM.pdf |access-date=15 April 2024 |url-status=live }}</ref>
 
If one subscribes to the 365&nbsp;day presumption, it is recognized the mechanism predates the [[Julian calendar]] reform, but the [[Sothic cycle|Sothic]] and [[Callippus|Callippic]] cycles had already pointed to a {{sfrac|365|1|4}}&nbsp;day solar year, as seen in [[Ptolemy III Euergetes|Ptolemy&nbsp;III]]'s attempted calendar reform of 238&nbsp;BC. The dials are not believed to reflect his proposed leap day ([[Epag.]]&nbsp;6), but the outer calendar dial may be moved against the inner dial to compensate for the effect of the extra quarter-day in the solar year by turning the scale backward one day every four years.