Meton of Athens
Meton of Athens (Greek: Μέτων ὁ Ἀθηναῖος; gen.: Μέτωνος) was a Greek mathematician, astronomer, geometer, and engineer who lived in Athens in the 5th century BC. He is best known for calculations involving the eponymous 19-year Metonic cycle which he introduced in 432 BC into the lunisolar Attic calendar.
The metonic calendar assumes that 19 solar years are equal to 235 lunar months, which is, in turn equal to 6940 days. This system was based on calculations made by Meton using his own observations of the summer solstice in 432 BC, and an observation made by Aristarchus 152 years later. Meton's observations were made in collaboration with Euctemon about whom nothing else is known.
The Greek astronomer Callippus continued the work of Meton, proposing the Callippic cycle. The Callippic cycle is 76 years long—approximately 4 times longer than the Metonic cycle, with one less solar day in the full cycle. Ironically, whereas the Metonic cycle overestimates the length of a solar year by 5 minutes, the Callippic cycle underestimates the length of a solar year by 11 minutes, and therefore produces results that are less accurate than those produced using the Metonic cycle.
The world's oldest known astronomical calculator, the Antikythera Mechanism (2nd century BC), performs calculations based on both the Metonic, and Callipic calendar cycles, with separate dials for each.
The foundations of Meton's observatory in Athens are still visible just behind the podium of the Pnyx, the ancient parliament. Meton found the dates of equinoxes and solstices by observing sunrise from his observatory. The bisectrice[clarification needed] of the observatory lies in an easterly direction, between the Acropolis and the Lycabetus hill.
What little is known of Meton come through ancient historians. According to Ptolemy, a stella or table erected in Athens contained a record of Meton's observations, and a description of the Metonic cycle. None of Meton's works survive.
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