How Do We Know the Earth Isn't Flat We Asked a NASA Expert

How do we know the Earth isn’t flat? For thousands of years people have known the Earth is round. Ancient civilizations used the stars and shadows to figure it out. Mariners confirmed it by sailing around the globe. And when the space age began, we saw it with our own eyes — the Earth is round!

A NASA scientist explains how we’ve known for centuries that our planet is a sphere.