Disappearing the Milky Way in Medieval Europe

Disappearing the Milky Way in Medieval Europe George Latura A ncient astronomical knowledge of the Milky Way survived in medieval Western Europe through Martianus Capella’s Marriage of Philology and Mercury and Macrobius’ Commentary on the Dream of Scipio (McCluskey, 1998). But these texts also transmitted a Platonist belief that ecclesiastical authorities found disturbing – the pagan belief that the celestial abode of virtuous souls was the Milky Way (according to Macrobius, Martianus Capella, Porphyry, Numenius, Manilius, Ovid, Cicero, and a student at Plato’s Academy, Heraclides of Pontus). Twelfth-century Chartrian scholars who delved into related Platonist matters were censured, and at times, accused of heresy (Dutton, 2006; Ellard, 2007). Various strategies evolved to combat the perceived threat of the Platonist Milky Way. Michael Scot (c. 1225) hung the label ‘Demon Meridianus’ on the Milky Way (Bertola, 2003; Harris, 2012) in an effort to demonize it. Sacrobosco, whose De Sphaera was one of the most popular astronomical university texts of the era, ignored the Galaxy altogether (see Thorndike, 1949), as if it simply did not exist. But the most effective tactic would be provided by Plato’s other student, Aristotle, who had removed the Milky Way from the heavens and placed it in the sublunary atmospheric region (Meteorologica, trans. Lee, 1916). Perusing Moerbeke’s new translations of Aristotle’s works from Greek (c. 1260), Aquinas adopted Aristotle as The Philosopher, displacing Plato from that lofty position. This coup introduced an anti-Platonism that lasted for centuries and that scholars still find difficult to comprehend (Hankins, 1996). The status of the Milky Way provides a key to this puzzle. On the Platonist side, the Milky Way was a celestial phenomenon. On the Aristotelian side, it was an atmospheric phenomenon. How could this dilemma be resolved? Enter Galileo who, with his telescopic observations (Sidereus Nuncius, 1610), placed the Milky Way back among the stars.