For most of history, people imagined the Earth sitting still at the center of everything. Aristotle argued this around 340 BC, pointing out that the Moon's shadow during a lunar eclipse is always circular — a clue that Earth is a sphere. The stars and planets, he thought, moved around us on perfect crystalline spheres.

Ptolemy refined this picture into a detailed mathematical model that could predict planetary positions. It worked well enough that the Catholic Church adopted it, and for over a thousand years it shaped how educated people thought about the heavens.

Then Copernicus quietly proposed something radical: maybe the Sun, not the Earth, sits at the center. Galileo and Kepler found observational and mathematical evidence in favor of this view, and Newton later explained why it all worked — gravity pulls every object toward every other object, and that single force governs everything from falling apples to orbiting moons.