Kathryn Lasky's picture book, The Librarian Who Measured the Earth, tells the story of Eratosthenes, a Greek astronomer and geographer who measured the circumference of the earth in around 200 B.C. with incredible accuracy. Lasky writes, "He calculated the circumference of the earth to be 252,000 stades, or 24,662 miles. When the earth was remeasured in this century, there was only a two-hundred-mile difference between the modern-day figure and the one that Eratosthenes had calculated over two thousand years ago!"
I'm a bit perplexed by Amazon's age range for the book, 4-8 years. Last year I shared the story with a class of gifted and talented children in grades 2-6. They, like me, were captivated by this amazing story. Tonight I read it to my bright 7-year-old, who enjoyed it and asked a lot of relevant questions, but clearly didn't comprehend a lot of the mathematics involved. My 4-year-old ignored it and paged through his own book. I'd say it's best for about 7 or 8 years and up...waaayyyy up! ;)
Also see the Measure the Earth Project where students around the world participate:
Your student/class can participate in The Noon Day Project that replicates Eratosthenes's measuring techniques. The spring project runs until April 11 and starts up again in the fall.
The Goal of the Noon Day Project is to have students measure the circumference of the earth using a method that was first used by Eratosthenes over 2000 years ago. Students at various sites around the world will measure shadows cast by a meter stick and compare their results. From this data students will be able to calculate the circumference of the earth.
Possible curricular ties: biographies of mathematicians, circumference, measurement, Ancient Greece
