More like 3.5. Fascinating and educational for a layperson like me, but I felt it was bloated. Yes, Eratosthenes was covered--even with the sketchy information on his life from the Suda [the Byzantine encyclopedia] and what his conclusions on geodesy--shape of the earth and its circumference--were and how he reached them. The earth as a globe was only one out of several theories current at that time. It was amazing that he reached pretty accurate conclusions using only primitive surveying techniques of that time and his knowledge of geometry--no trigonometry tables back then. But the book was swollen was tangential information such as: the Hellenistic society in Alexandria of his time and its exhaustive description; the Ptolemaic dynasty; The Museum and Great Library in Alexandria; how knowledge of the ancients was lost [much through the vandalism of Christian zealots who I'd compare to the present-day Taliban or to ISIS rampaging through the ruins of Palmyra] and finally recovered, some through the Arab scholars, some on palimpsests, and some through references in other writings that have come down to us.

I feel this readable book could have been condensed into a volume half its size. Interesting to me was the fact that Columbus knew the world was round, BUT he underestimated the size of its circumference. Also interesting was the fact that his successor at the Great Library, Aristophanes of Byzantium, was the man who first developed a system of diacritics used in the Greek language; they are still used today in Modern Greek in a simpler form. The author closes with a metaphor: as the Eratosthenes Mountain Range 6000 feet undersea, Eratosthenes the man has remained obscure to us.

Recommended for popular science fans. ( )

A good read, particularly for those interested in the topic. If you enjoyed "Longitude", you'll likely enjoy this book but towards the end it seems to get a bit 'fuzzy'. The first 2/3rds was really quite interesting even if the author's style may make it somewhat more difficult for readers to understand. Drawing a straight line - around the earth or in a book's presentation of topic - is never an easy task. It's a good read, though, and a book I'm glad I picked up! ( )

A very well written, necessarily tangential account of Erastosthenes' calculation of the circumference of the Earth. I really enjoy these excursions into popular science. If you enjoyed Longitude, you will enjoy Circumference. ( )

Author Nicholas Nicastro has written several historical novels set in the ancient world; here he moves into popular history with an account of Eratosthenes' calculation of the circumference of the Earth. Since little is known about Eratosthenes, much of the book involves filling in various tangents, such as details about ancient Alexandria where Eratosthenes became head librarian of the Museum in 245 BC. The beginning of the book is rather choppy with the first chapter moving from ancient sea travel to the Pharos lighthouse, Euergetes, the Ptolemaic king who brought Eratosthenes to Alexandria, the author's own trip to Alexandria in 2007, and finally the method and assumptions Erathosthenes used to calculate the Earth's circumference.

This is another of that group of books of which Longitude is probably the most famous example. Nicholas Nicastro explores the history of the idea of the circumference of the globe. It is a journey that starts with questions raised by an ancient Greek named Eratosthenes, about whom we learn a great deal more than his discovery of circumference, and doesn't end until almost two thousand years later. For those who love the history of science and how ideas develop it is a great read. Enjoy! ( )