Philosopher, Mathematician, Astronomer, Geographer (c.110 BC – c.40 BC)

Geminus was a polymath from Rhodes. He studied in the philosophic school of Poseidonius and was initiated into the Stoic philosophy. Geminus wrote numerous books on mathematics and astronomy, only fragments of which survive today.

Although he was mistaken for Roman because of his seemingly Latin name, he was purely Greek as his name’s true origin suggests (from γέμος/gemos = φορτίον/ load). His primary field of interest was astronomy and mathematics. He wrote the book Isagogue to the Phenomena or Introduction to Astronomy, which fully survives. It contains the most important theories of ancient Greek astronomy, serving as a simple astronomical textbook. It includes commentaries on the works of Hipparchus, the greatest astronomer who ever lived as well as detailed descriptions on the constellations, the variation of on the length of day and night at different latitudes, rising of the signs of the zodiac cycle and the lunar month’s length. Furthermore, Geminus explains the solar and lunar eclipses, the motion of the planets and the weather prognostications connected with the movement of stars.

His books Epitome on Poseidononius’ Meteorological Explanations and On the order of Mathematics survive only in fragments. The latter is a book on the history of mathematics. It features works on arithmetics and geometry, as well as applied mathematics such as logistics, geodesy, harmony, optics, mechanics and astronomy. In it, Geminus provides historical data on how mathematical terms such as hypothesis, axiom, theorem, figure, angle etc were founded. This mathematic encyclopaedia was one Proclus’ most valuable tools on mathematics since he quotes it extensively in his own works. It was also used extensively by Eutocius and Heron of Alexandria.

Geminus’ mathematical and astronomical work, while not as influential as his predecessors, exerted great influence to the mathematicians and philosophers of the late antiquity. Today, a crater on the moon bears the name “Geminus” in his honour.


  1. D.R. Dicks. Geminus. Complete Dictionary of Scientific Biography. Web.
  2. Georgakopoulos, Konstantinos. Ancient Greek Scientists. Georgiades, Athens: 1995. Print.
  3. Tziropoulou, Anna Eustathiou. Ἀρχιγένεθλος Ἑλληνικὴ Γλῶσσα. Georgiades, Athens: 2011. Print.
  4. J J O’Connor, E F Robertson. Geminus. University of St. Andrews, Scotland. Web.

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