Eratosthenes, a Greek mathematician, was the first to calculate the Earth’s circumference with remarkable accuracy over 2,000 years ago using a simple yet brilliant method. He observed that at noon in Syene (modern-day Aswan, Egypt), the Sun was directly overhead and cast no shadow, while at the same time in Alexandria, a shadow formed at an angle of about 7.2 degrees. Realizing that this angle represented 1/50th of a full circle and assuming the Sun’s rays were parallel and the Earth was spheri