Circles and PiEratosthenes

Of course, it can be difficult to translate his original results into modern units like kilometres. In ancient Greece, distance was measured in stadia (approximately 160 m), but there was no universal standard. Every area had a slightly different version, and we don’t know which one Eratosthenes used.

In the following centuries, scientists tried to use other methods to calculate the radius of Earth – sometimes with very different, and incorrect results.

It was one of these incorrect measurements that prompted Christopher Columbus to sail west from Portugal. He assumed that Earth was much smaller than it actually is, and hoped to reach India. In fact, he arrived at a different continent in between: the Americas.