CIRCUMFERENCE

Democritus of Abdera posited the existence of atoms. Aristotle accurately described the embryology of the chick.  Aristarchus put the sun at the center of the planetary system.  Yet nothing like “science” existed before the Renaissance. When Eratosthenes measured the circumference of the Earth by comparing shadows at noon on the summer solstice, remarkable as it was, and enduring as it would prove to be, his work was singular: neither a test, nor a disproof; neither a challenge, nor an argument.  It simply was.  But what was it?

St. Martin's Press, 2008.

 Nicholas Nicastro wrote five historical novels (three of them set in ancient times) before taking on this thin biography.  The life and works of Eratosthenes are mostly lost to us, destroyed when the Great Library of Alexandria and smaller collections across the world were looted and their  books burned as Hellenistic civilization collapsed. What we know about him is second-hand from Strabo, Polybius, the 10^th century Suda, and similar sources.  Nicastro reconstructs as much as seemed relevant to the story here: how and why the librarian of Alexandria computed the size of the Earth as one element in his general geography.  In fact, Eratosthenes invented the word geography.

The Hellenistic world was very much like our own time: held in tension by science and superstition, commerce and war, ecumenism and parochialism.  Nicastro spans all of that because the known facts of the life and works of Eratosthenes are so few.  Much of the book is given over to calculations in various ancient stade measures (whence the modern "stadium").  Like many other technical reads for large audiences, the end notes are not keyed within the text.  Keep a bookmark there so that you can flip back and forth. 

Coin from Cyrene c. 480-435.
3.34 gr.  1.5 cm.
Zeus Ammon / Silphium.

Eratosthenes came from Cyrene, a city in what is today Libya near what is today Benghazi.  He studied philosophy in Athens before being appointed to the Great Library by Ptolemy III Euergetes.  Nicastro underscores the fact that contrary to our common opinions today, Athens was not a home to learning and philosophy until after its Golden Age and eventual downfall in the Peloponnesian Wars. Anaxagoras, Protagoras, and Socrates all had been tried for impiety.  Nicastro also argues that Eratosthenes probably did not travel to Siwa (Aswan) to see the sun overhead.  He might have sent an underling from the Museum to do that.  A single fragment letter from Archimedes to Eratosthenes suggests a long correspondence between the two.  

But Eratosthenes was more than a geometer.  Just as most of Newton’s writings were not about physics, so, too, did Eratosthenes mostly write on grammar, poetry, and history.  That was apparently the attraction for Nicastro. “[He] received a BA in English from Cornell University (1985), an MFA in filmmaking from New York University (1991), an M.A. in archaeology and a Ph.D. in psychology from Cornell (1996 and 2003).” (Wikipedia).  It takes one to know one.

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