He measured the circumference of the Earth using nothing but a vertical stick, a deep well, and a shadow, over 2,000 years ago. His reward? The intellectual elite of his day mockingly nicknamed him "Beta," the eternal number two, because he refused to specialize in any single discipline. Eratosthenes of Cyrene coined the word geography, dated the Trojan War, calculated the Earth's tilt, and ran the Library of Alexandria, and his peers still called him a runner-up.

This episode follows the ultimate ancient generalist from his education across rival philosophical schools in Athens, through the job offer that handed him the greatest data center of antiquity, to the elegant shadow experiment at Syene that measured the planet. It also covers the prime-number sieve that still bears his name, the respect of Archimedes, who dedicated a book to this supposed second-rater, and the heartbreaking final choice of a man who could no longer read.

• Pentathlos and Beta: why hyper-specialized Athens despised the man who crossed every lane
• Chief Librarian of Alexandria: the ancient world's biggest dataset and the king who hired a generalist
• A stick, a well, and a 7.2-degree shadow: measuring the Earth with geometry and a camel caravan
• The Sieve of Eratosthenes and the cattle problem: respect from Archimedes, the era's true alpha
• Blindness and a final fast: the tragic end of the man who saw the curve of the world in his mind