Sosigenes of Alexandria

Sosigenes of Alexandria (Greek: Σωσιγένης) was a Greek astronomer who, according to Pliny the Elder, was consulted by Julius Caesar for the design of the Julian calendar.

Little is known about him apart from Pliny's Natural History. Sosigenes appears in Book 18, 210-212:

In Book 2, chapter 6, Sosigenes is credited with work on the orbit of Mercury:

Some sources state that the Julian calendar was designed by Aristarchus of Samos, although it is not clear where this conclusion originates. Ptolemy III Euergetes, Aristarchus' contemporary, did indeed decree a reform of the Egyptian calendar in 238 BC, but it was never implemented. The reform, however, would have added an extra day (leap day) to the 365-day Egyptian calendar every four years, a feature shared by the Julian calendar.

Sosigenes was portrayed by Hume Cronyn in the 1963 movie Cleopatra. This portrayal is heavily fictionalized: he serves as Cleopatra's tutor/adviser and later her envoy to Rome. He is ultimately murdered in the Forum by Octavian, commencing his war against Egypt. None of these events are present in historical record, and were invented for the film.

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