Geminos (or Geminus) of Rhodes is a very important figure of late Greek antiquity, in astronomy and mathematics. He lived in the 1st century, but we know almost nothing about his life and work. Heath mentions that he was a Stoic philosopher and a pupil of Posidonius.

Simplicius has preserved that Geminos wrote a commentary entitled "Exegesis" on Posidonius' work "On Meteors," and he also refers to Alexander of Aphrodesius (around 210 AD), who quotes an excerpt from the summary of Posidonius' "Meteorological Explanations." In fact, Simplicius concludes by noting: "Thus, I also present the difference according to Geminos, or according to Posidonius beside Geminos... He delivers."

From the entirety of his work, there is only one significant astronomical treatise "Introduction to the Phenomena," which is presented in this edition. This work, first published in 1590, is characterized by Paul Tannery as one of the best astronomical works of Greek antiquity.

Geminos' "Introduction," which is divided into 18 chapters, contains important theories of Greek astronomy. The author refers to the solar year, the twelve zodiac signs, the constellations, the phases of the Moon, solar and lunar eclipses, the movements of the planets, and the zones of the Earth.

In the 17th chapter, he examines the principles by which the calendars, the astronomical calendars, are linked to weather indications (signs). The last chapter is considered by several scholars to be unrelated to the rest of the work's content, as it deals with quite difficult technical issues (evolution).

At the end of the work, there is an astronomical calendar (calendar), about which there have been some doubts as to whether it is truly the work of Geminos. Nevertheless, Geminos' "Introduction" amazes the scholar with its concise and advanced scientific discourse.