Copernicus & the Heliocentric Revolution
The radical idea that moved the Earth from the center of the universe
1.1 The Ptolemaic Universe
Claudius Ptolemy (c. 100–170 CE) constructed a geocentric model using epicycles and deferents that dominated astronomy for 1,400 years. The model was mathematically sophisticated but increasingly cumbersome as observations improved.
1.2 Nicolaus Copernicus
Nicolaus Copernicus (1473–1543) proposed in De Revolutionibus Orbium Coelestium (1543) that the Sun, not the Earth, lay at the center of the planetary system. His heliocentric model simplified many orbital calculations but still relied on circular orbits and epicycles.
1.3 Impact and Opposition
The Copernican model met resistance from both the Catholic Church and Protestant reformers. Yet it inspired a new generation — Tycho Brahe, Kepler, Galileo — to look at the heavens with fresh eyes and better instruments. The revolution had begun.