In this episode, part four of four on a series on Greek philosophy, mathematics, and science in the 5th century BC, we describe the earliest astronomical observations and calculations in ancient Mesopotamia and Egypt and their influence on ancient Greek astronomy; the various planets and star constellations found in Greek literature, as well as the origins of the Zodiac; the earliest Greek astronomical speculations of the universe found in Greek mythology (Homer and Hesiod) and in Pre-Socratic philosophy; the Pythagorean model of the universe put forward by Philolaus; and the astronomical calculations made by Oenopides and Meton
