Sosigenes (astronomer)

Source: Wikipedia, the free encyclopedia.
(Redirected from Sosigenes of Alexandria)
Known forConsulted by Julius Caesar for the design of the Julian calendar
Scientific career

Sosigenes (Greek: Σωσιγένης)[1][2] was an ancient astronomer. According to Pliny the Elder's Natural History 18.210–212, Julius Caesar consulted him while he was designing the Julian calendar.


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

... There were three main schools, the Chaldaean, the Egyptian, and the Greek; and to these a fourth was added in our country by Caesar during his dictatorship, who with the assistance of the learned astronomer Sosigenes (Sosigene perito scientiae eius adhibito) brought the separate years back into conformity with the course of the sun.[citation needed]

Sosigenes is credited with work on the orbit of Mercury, which is described by Pliny in Book 2, chapter 6, of his Natural History:

The star next to Venus is Mercury, by some called Apollo; it has a similar orbit, but is by no means similar in magnitude or power. It travels in a lower circle, with a revolution nine days quicker, shining sometimes before sunrise and sometimes after sunset, but according to Cidenas and Sosigenes never more than 22 degrees away from the sun.[3]

The introduction of the Julian year occurred in 46 BC. This particular year lasted 445 days in Rome to correct the erroneous old Roman calendar.[citation needed]

Cultural depiction

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.[citation needed]

See also


  1. ^ Pliny the Elder Naturalis Historia XVIII, 210-212:Sosigene
  2. ^ Dialetis, Dimitris (2007). "Sosigenes of Alexandria". In Hockey, Thomas; et al. (eds.). Biographical dictionary of astronomers. Vol. II, M–Z. Springer. p. 1074.
  3. ^ Book II, chapter 6, 36-41 in Pliny the Elder, Natural History I. Loeb Classical Library 330. Translated by H. Rackman, 1938, p.193. In a very old translation from C. Plinius Secundus, The Historie of the World, translated by Philemon Holland (1601), it is book 2 chapter 8, and reads: "Next upon it, but nothing of that bignesse and powerful efficacie, is the starre Mercurie, of some cleped Apollo: in an inferiour circle hee goeth, after the like manner, a swifter course by nine daies: shining sometimes before the sunne rising, otherwhiles after his setting, never farther distant from him than 23 degrees, as both the same Timæus and Sosigenes doe shew."