Forget the myth of Columbus' daring in imagining a round earth. Nicastro not only traces the conception of a spherical world back more than a millennium before the seafarer set sail but also recounts in fascinating detail how the ancient Greek geometer Eratosthenes measured that sphere with astonishing accuracy. Though it would be thousands of years before his feat received appropriate recognition, Eratosthenes conducted his revolutionary science with nothing more complex than a sundial and a compass. With reader-friendly clarity, Nicastro explains the surprisingly simple calculations behind the earth measurement. But readers learn about much more than geodesy: Nicastro delivers the deeply human story of a multitalented genius whose tenure as the head of Alexandria's famed library occasioned remarkable achievements in literature, history, linguistics, and philosophy despite the political turmoil that periodically rocked the Ptolemaic world. Indeed, this polymath plays out his long career against a colorful backdrop peopled with a rich variety of conquerors and cosmologists, murderers and mathematicians. A distant yesterday still furnishes fascinating drama for readers today."—Booklist "Propelled by the story of Eratosthenes' solution of an ancient puzzle—'How big is the earth?'— Circumference offers many unexpected pleasures along the way.  With an amiable voice and a flowing style, Nicholas Nicastro brings historical places and people to vivid new life, from the shining city of Alexandria to the great conqueror for whom it was named.  A real treat for lovers of history and science."—Steven Strogatz, author of Sync, and Schurman Professor of Applied Mathematics, Cornell University

"Nick Nicastro's new book is an engaging look at one of the greatest and most neglected minds in antiquity.  The author has a gift for explaining complex ideas clearly and with an eye for the telling (and amusing) detail.  In breadth and style I am reminded more than anything else of James Burke's Connections."—Dr. David B. Hollander, Iowa State University