Ancient Greek Astronomy

How the ancient Greeks understood the universe; what they got right and what they got wrong. How Aristotle understood the Earth was round by observing lunar eclipses; how Aristarchus of Samos used these results to work out the relative sizes of Earth, the Sun, and Moon, how Eratosthenes of Cyrene measured Earth’s circumference, and how Hipparchus of Nicaea determined created the first catalog of stars and discovered Earth’s 26,000 year axial precession, Finally, we take a look at Claudius Ptolemy’s collection of works in the Almagest, and how he came up with a system of epicycles to explain planets’ retrograde motion.