Ptolemy
He was an astronomer, mathematician, and geographer. He described in his writing the Greek geocentric view of the universe. Earlier Greek philosophers changed the old assumption of a flat Earth below a "vault of the heavens". They substituted a spherical Earth surrounded by a Celestial sphere. Ptolemy built these two spheres into a system of nested spheres. He also thought out and described the apparent motions of the planets as they were known in his time.