Note: Ptolemy (tol-eh-mee) was a Roman astronomer who lived in Alexandria, Egypt, about 100 years CE. He developed a theory of the universe that was adopted by most scholars during the Middle Ages. The Polish astronomer Nicolaus Copernicus lived from 1473 to 1543. Relying mostly on mathematics, he developed a very different understanding of the universe. Geocentric means "earth-centered" and heliocentric means "sun-centered."
Source: Drawings of the universe by Claudius Ptolemy (circa 100 CE) and Nicolaus Copernicus (circa 1500).