BY day, Eratosthenes was responsible for the world-famous library in the Egyptian city of Alexandria. He tutored the Pharaoh’s sons, and - no mean poet himself - amassed a superb collection of the epic poetry, plays and philosophical writings of ancient Greece.

In his spare time, Eratosthenes (who counted Archimedes among his friends) was also one of the most remarkable scientists in history.

He did not merely coin the term ‘geography’. He invented geography. Using the shadows cast by the noon-tide sun, he became the first man to calculate the circumference of the earth, which he did with remarkable accuracy, and produced the first scientific map of the world, showing parallels and meridians.

Because of his wide interests, from verse to Number Theory, some called him a dabbler, nicknaming him ‘Beta’ because he was always second in his field.

His admirers, however, were much nearer the mark: they called him the Pentathlete, a champion in many disciplines.