The Dawn of Modern Cosmology

Abstract: In the late fifteenth century, the earth stood motionless at the center of a relatively small, hierarchically-ordered cosmos. Around it revolved the moon, sun, and planets, embedded in crystalline spheres and moving in perfect, eternally unchanging circles. The earth, by contrast, was the realm of change, of growth and decay, generation and corruption. By the early eighteenth century, the sun had replaced the earth at the center, rotating on its axis as spots moved across its surface. The earth was a planet, just like the others, some of which had moons too; despite our commonsense perceptions to the contrary, it hurtled through an indescribably large cosmos at incredible speeds. The crystalline spheres had been shattered and dissolved, the perfect circles swapped for ellipses, and the contrast between heavens and earth abolished in favor of a set of laws that united both. This talk will tell the story of these changes, commonly described as the Copernican Revolution—a story that is less simple and straightforward than is commonly supposed.