![\"circumference0282\"](\"http:\/\/farm4.static.flickr.com\/3109\/3183590882_c600135995_b.jpg\")
<\/a>Two things about Eratosthenes impressed my pre-adolescent self.\u00a0 First, when my fourth grade teacher was teaching the class that Christopher Columbus had to argue with a group of flat-earth scholars — that the world was round and he wouldn’t fall off the edge if he sailed west — I knew that school lesson was bunk.\u00a0 Scholars had known the earth was round for more than a thousand years by Columbus’s era.\u00a0 In truth, they were debating how big it was and how long the journey might last.\u00a0 Knowing that Eratosthenes (and others) had already measured it gave me my first sense of skepticism.\u00a0 The teacher and the school book were wrong.\u00a0 I never completely trusted a source again.\u00a0 Teachers, experts, supervisors, issue advocates, politicians, judges, and all other authorities are fallible.\u00a0 Be skeptical!<\/p>\nSecond, Eratosthenes helped me realize the power of reasoning.\u00a0 Consider how you would measure your waistline.\u00a0 You’d use a tape measure, right?\u00a0 Now, imagine how you would measure the circumference of the planet.\u00a0 Is your tape measure long enough?\u00a0 Are you prepared to swim great distances?\u00a0 Do you have the time?\u00a0 Eratosthenes, a librarian in Alexandria circa 200 BC, measured the earth using only shadows, angles, and math.\u00a0 He was brilliant to conceive the experiment, and despite feeding a few errors into his calculations, he was remarkably accurate, too.\u00a0 Columbus actually low-balled his 15th century circumference estimates because he hoped the world was smaller than Eratosthenes figured.<\/p>\n
Eratosthenes’ estimate for the distance between the Earth and the Sun was remarkable, as well:\u00a0 it was magnitudes greater than others’ guesses … and reasonably accurate.<\/p>\n
These thoughts came to mind while reading Circumference<\/em><\/strong>, and new book by Nicholas Nicastro.\u00a0 Precious little is known about Eratosthenes himself and most of his work is known to us only from the surviving texts of other ancient writers.\u00a0 Nicastro compensates for that by filling his slim volume with information about the world in which Eratosthenes lived.\u00a0 You could easily read about Eratosthenes’ ingenious method in five pages or less, but Nicastro describes the politics and culture of Alexandria, the famous library in which Eratosthenes worked, and the state of geodesy (the science of earth’s size and shape) since his time.\u00a0 I grew impatient with the political “fluff” at times, but those sections (which I read through quickly) might be enjoyable to readers more interested in Egypt and Greece.\u00a0 On the other hand, I savored the discussion regarding western civilization’s developing concept of geography and places still unknown.<\/p>\n This book was a quick and pleasant read.\u00a0 I read it, ironically, during a transcontinental flight when I could see the curvature of the earth out my window.\u00a0 How might Eratosthenes enjoyed seeing that?<\/p>\n","protected":false},"excerpt":{"rendered":" When I first learned about Eratosthenes from some long-forgotten astronomy book in my youth, roughly age 10, I fell in love with the name: Air-uh-TOSS-the-knees. I’ve always enjoyed pronouncing long words and names like that. Once I had the name … Continue reading