The desire to learn drives scientific inquiry In Alexandria, at that time, there lived a man named Eratosthenes. One of his envious contemporaries called him “beta”—the second letter of the Greek alphabet—because, he said, “Eratosthenes was second-best in the world in everything.” But it seems clear that, in many fields, Eratosthenes was “alpha.” He was an astronomer, historian, geographer, philosopher, poet, theater critic, and mathematician. He was also the chief librarian of the Great Library of Alexandria. And one day, while reading a papyrus book in the library, he came upon a curious account. Far to the south—he read—at the frontier outpost of Syene, something notable could be seen on the longest day of the year. On June 21st, the shadows of a temple column, or a vertical stick, would grow shorter as noon approached. And as the hours crept towards midday, the sun’s rays would slither down the sides of a deep well which on other days would remain in shadow. And then, precisely at ...