Geminus of Rhodes (Γεμῖνος ὁ Ῥόδιος) was a Greek astronomer and mathematician of the 1st century BCE, active around 70–50 BCE [1][2]. A pupil of the Stoic philosopher Posidonius on Rhodes, his work reflects this philosophical influence [1][2]. He was primarily a compiler and systematizer of existing astronomical knowledge rather than an original observer [1][2].

His only surviving complete work is the Introduction to the Phenomena (Εἰσαγωγὴ εἰς τὰ Φαινόμενα), an astronomical textbook [1][2][3]. He is also credited with a lost Theory of the Mathematical Sciences and a lost commentary on the mathematical sections of Posidonius's Meteorology [1].

Geminus’s significance lies in his Introduction to the Phenomena, which became a standard astronomical primer. It systematically explains the celestial sphere, constellations, and planetary motions, preserving crucial details of Greek astronomy from the era of Hipparchus [1][2][3]. The work also demonstrates the application of Stoic philosophy to the classification of mathematical sciences, illustrating the integration of philosophy and science in the Hellenistic period [1].

Sources 1. Stanford Encyclopedia of Philosophy: Geminus: https://plato.stanford.edu/entries/geminus/ 2. Encyclopædia Britannica: Geminus: https://www.britannica.com/biography/Geminus 3. Perseus Digital Library: Geminus, Introduction to the Phenomena: http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0371