Everyone knows that the Earth is round. In fact, we’ve known this for thousands of years. Thanks to scientists and philosophers from the past, we’ve got exacting science that proves the fact. But how can us scientific fledglings really prove it?
Well, for one, there are thousands of photos from space that show the Earth as a globe, but those have only been around for half-century. So, how did philosophers, explorers and scientists like Aristotle, Biruni and Magellan figure it out hundreds of years ago? The short answer is astronomy, mathematics and exploration.
Here’s the highly abbreviated version of how humans discovered that the Earth is round. For the cool video version skip to the clip at the bottom:
For thousands of years scholars and philosophers debated and pondered just what the Earth looked like from a distance. Early on, about 2,500 years ago, philosophers like Thales, Demoritus and Anaximander believed that the Earth was flat. They hypothesized that the Earth was a short cylinder with a flat, circular top that remained stable because it was the same distance from all things.
Or that “the earth is flat and rides on air. Or, that “the Earth was flat, with its upper side touching the air, and the lower side extending without limit.” Like a planetary Pringles can. This belief in a flat Earth continued until Greek philosophers like Aristotle, Socrates proposed something new.
Aristotle was the first to notice that “There are stars seen in Egypt which are not seen in the northerly regions.” And since this could only happen on a curved surface, he hypothesized that the Earth was a sphere. He was also the first to observe that the shadow of Earth on the moon during a lunar eclipse is round. Even with his evidence, the world wasn’t yet convinced, after all civilization had always believed the Earth to be flat, and a silly-named Greek philosopher wasn’t going to change their mind so easily.
But it wasn’t until the height of the Roman Empire, several hundred years later, that the theory of a spherical Earth became mainstream when Roman authors included the fact in any and all scientific writings. But even then, no one knew how big of a sphere the Earth actually was, and the whole thing was just as big a mystery as ever.
That calculation wasn’t officially solved until the Middle Ages when a scholar named Biruni used a new method to accurately compute the Earth’s circumference for the first time. Biruni’s method used trigonometric calculations to calculate the curvature of the Earth.
After Biruni’s discovery of the size of the Earth, came the first observable proof of the Earth being a sphere through circumnavigation.
Ferdinand Magellan, a Portuguese explorer, successfully led a fleet of ships continuously around the world in the early 1500s, proving, finally, that the Earth was indeed round.
Obviously, there is much more to the story, including hundreds of years of scientific and technological advancement that offer new and more exact evidence for Earth being round, but that’s it in a nutshell. For a more lighthearted take, here’s a cool video explaining the top ten reasons why we know Earth is round. Take a look: