How The Ancient Greeks Proved Earth Wasn't Flat 2,200 Years Ago?

The Ancient Greeks used shadows and clever thinking to show that Earth was round, not flat, way back when people still thought Earth was a big flat plate.

Imagine you're playing with your shadow at different times of the day. When the sun is high up, your shadow is short. But when the sun is low, like in the morning or evening, your shadow gets long. That’s because the angle of the sunlight changes.

A smart Greek man named Eratosthenes did something similar with big sticks and shadows, but on a much bigger scale. He lived in two cities that were far apart, one was Alexandria, and the other was Syene (which is now Aswan).

On a special day, when the sun was directly above Syene, he noticed there were no shadows at noon. But in Alexandria, a stick did cast a shadow. By measuring how long the shadow was and using some clever math, Eratosthenes figured out how big Earth was, and that it must be round!

It’s like if you drew a circle on the ground with chalk, and then you stood at two different points on that circle, one in the middle, one near the edge. The shadow would help you see that the circle (or Earth) was curved!