Theodosius
of Bithynia

The man who made the sky behave on paper. Theodosius of Bithynia (fl. 2nd–1st century BCE) wrote Spherics, the go-to manual for anyone trying to make sense of celestial geometry. Long before telescopes, he mapped the heavens with pure reasoning — helping astronomers figure out how circles, spheres, and stars all lined up. His math was precise, his diagrams tight, and his influence long-lasting. Theodosius didn’t reach for the stars — he brought them into geometric order.