Astronomer, mathematician, and all-around curriculum designer. Geminus of Rhodes (fl. 1st century BCE) wrote a handy intro to astronomy that doubled as a science textbook for Hellenistic students. He linked the stars to geometry, the seasons to the heavens, and everyday life to celestial mechanics. Not flashy, but practical — and deeply influential. If you wanted to learn how the cosmos worked (without jumping straight into Ptolemy), Geminus was your guide. Think of him as antiquity’s favorite science teacher.