Eratosthenes, a Greek mathematician and astronomer, made a groundbreaking estimation of the Earth’s circumference in the 3rd century BCE. Contrary to the varied and often inaccurate guesses by his contemporaries, including Plato and Archimedes, Eratosthenes’ method involved measuring the angles of shadows cast in Alexandria and Syene at noon during the summer solstice. Observing that in Syene, the Sun was directly overhead, while in Alexandria, it cast a small shadow, he deduced that the Sun’s angle of elevation differed by about 7 degrees between the two cities.
Eratosthenes calculated the Earth’s circumference to be approximately 250,000 stadia, translating to about 25,000 miles (40,000 kilometers), remarkably close to modern measurements. His method demonstrated the immense potential of simple yet cleverly designed experiments in uncovering fundamental truths about our world. This achievement not only marked a significant advancement in geographic knowledge but also showcased the ingenuity and scientific acumen of ancient scholars.
