② Beyond the Edge of the World▪On worldviews in Columbus’ time

What this episode covers

Columbus discovers America. But more importantly, he discovers discovery itself. In 1492, Columbus sailed west to prove that the world was round. His sailors, terrified of falling off the edge of the world, were on the brink of mutiny just as America’s coastline came into view. Except they weren’t. Ever since antiquity, nobody who had given it a moment’s thought actually believed the world was flat. Especially sailors, who could see the world’s curvature on the horizon with their own eyes. This myth of medieval people believing the world to be flat was constructed after the fact. It was a story of ignorance that neatly fitted with the newly defined ‘Dark Ages’. It showed just how far men had come, and how truly the Renaissance man was head and shoulders above his ancestors. Or is there more to the story than that? The discovery of America may not have proven to anyone that the earth was round, but it did completely uproot everyone’s concept of what the world looked like. Hello and welcome to A History of Science. Episode 2: Beyond the Edge of the World. Introduction In 600 BC, Pythagoras was the first of the ancients to call the world round. In the centuries that followed, revered Greek writers including Plato and Aristotle all paid lip service to the idea, until in the second century AD the Alexandrian writer Ptolemy settled the issue once and for all. In his Almagest, he summarized all arguments made over the centuries for a spherical earth. The book would remain the standard on astronomy for the next 1400 years, and ensured that the spherical earth was known throughout medieval Europe. Among the proofs that Ptolemy gave were theoretical and practical ones. To his more learned readers, he argued that every part of the earth’s surface tended towards the center, and so logically formed a perfectly round globe. Yet he also described how mountains seem to rise out of the sea to sailors on an approaching ship, indicating that they must have been hidden by the curved surface of the sea. And it were imaginative explanations like these that ensured that no fifteenth century sailor was afraid of falling of the edge of the world. So Columbus’ voyage did not convince his supposedly backwards contemporaries of the sphericity of the earth. His discovery of the American continent, however, did completely change the perspective medieval people had of the earth. Not from a flat disc to a round globe, but from perfectly shaped spheres of land and water to a seemingly random pattern of continents. In this episode, we will explore how Columbus’ discovery changed that perspective, and how it planted into the minds of fifteenth century people the seed of discovery. The Ptolemaic System and Planetary Orbits What did the world look like to Columbus and his contemporaries? It was as round to them as it is to us, but apart from that? Well, for starters, it was the center of the universe. Ptolemy summarized earlier philosophers’ arguments for the earth being the universe’s center in his Almagest. This idea fitted neatly with the Christian idea of man and his habitat being the core of God’s Creation, and went down like butter in medieval Europe. The ancients envisioned the universe as a geometrically based system, built up from perfect circles, triangles, and other forms. They reasoned that for any movement to continue indefinitely, such as the planets’ orbits, only perfect mathematical shapes would suffice. Any other shape would be inefficient causing the planets to lose their speed and eventually crawl to a halt. A map of the Ptolemaic system, then, closely resembles a clockwork. The earth forms an orb in the center, with all other planets moving around it in perfect circles. Now, in reality the planets move in egg-like ellipses, not in perfect circles. And earth rotates in an ellipse of its own, of course. And, just for the record,