How Did People Figure Out That The Earth Was Round Without Any Technology?

The video explores the evolution of beliefs about Earth's shape, from the ancient Flat Earth concept to the acceptance of a spherical Earth. It highlights Greek philosophers like Socrates, who used lunar eclipses to argue for a round Earth, and Eratosthenes, who calculated Earth's circumference using observations in Syene and Alexandria. The video also discusses the eventual global acceptance of the round Earth theory, aided by 15th-century voyages that provided concrete evidence. Despite centuries of scientific evidence, some people still support the Flat Earth theory today.

What evidence did Juan Sebastian Alcano provide regarding the Earth's shape?

Why do some people today still doubt the round Earth theory despite scientific evidence?