Aristotle, Ptolemy and Copernicus. Frontispiece etched by Sefano della Bella from Galileo Galilei's Dialogo...sopra i due massimi sistemi del mondo (Dialogue Concerning the Two Chief World Systems), published in Florence by Giovannie Batista Landini, 1632. Aristotle (384 BC - 322 BC) was a Greek philosopher known as the founder of logic. He had a geocentric view of the heavens that consisted of 55 concentric and crystalline spheres. Ptolemy (c. 85 - 165 AD) was an Egyptian astronomer who devised the Ptolematic system, which held that the Earth was at the center of the universe, with the planets revolving around it. This view dominated astronomical thinking until it was unseated by Nicolaus Copernicus (1473-1543) and his heliocentric system in the 16th century.