Why Did the Ancient Greeks Believe the Earth Was Flat?

Imagine you're on a boat, sailing out to sea. As you go further away, the shore disappears little by little, like it's being eaten by water. The ancient Greeks thought this meant the Earth was flat, like a big round plate floating in space. But some smart thinkers, like Anaximander and Pythagoras, started wondering if maybe the Earth was actually a ball instead of a plate. They watched the sky and noticed how stars moved across it at different times of year, making them think the Earth might be spinning or moving around the sun.