A detailed educational infographic titled "How Eratosthenes Calculated the Circumference of the Earth," featuring a cross-section of the Earth and historical scenes from ancient Egypt. To the left, Eratosthenes stands in Alexandria measuring a $7.2^\circ$ shadow cast by a gnomon, while to the right, a deep well in Syene is shown with the sun directly overhead, casting no shadow.The central diagram uses geometric lines to show that the $7.2^\circ$ angle at the surface is equal to the angle at the Earth's center between the two cities. Four labeled steps explain the calculation: since $7.2^\circ$ is $1/50$th of a full circle ($360^\circ$), the distance between the cities (5,000 stades) is multiplied by 50 to find the total circumference of 250,000 stades.
Discoveries & Inventions

How Eratosthenes Calculated the Circumference of the Earth

Introduction More than two thousand years ago, Eratosthenes Calculated the Circumference of the Earth using a simple but brilliant scientific […]