Timeline

Greek philosopher Pythagoras proposed the idea of a spherical Earth, often theorizing that a sphere was the most "perfect" geometric shape.

Anaxagoras and Empedocles provided observational evidence, noting that during lunar eclipses, the Earth cast a circular shadow on the Moon.

Aristotle provided definitive physical arguments. He used the changing constellations visible at different latitudes and pointed out that ships gradually disappear hull-first over the horizon, proving the surface is curved.

Eratosthenes used solar observations (measuring shadows in Alexandria and Syene) to calculate its circumference within an incredibly small margin of error.

Ferdinand Magellan and Juan Sebastián Elcano completed the first circumnavigation of the world.