The Librarian Who Measured the Earth

The Librarian Who Measured the Earth, by Kathryn Lasky (46 pages)

Recommended Grade Level: 4-6

NCTM Standards: Geometry, Algebra, Problem Solving, Connections

Summary: This book tells the story of Eratosthenes, a Greek scholar born over 2,000 years ago. As a child he was a smart and curious boy and excelled in his studies at the gymnasium. He liked to ask big questions such as,“how much of the earth is land?” and, “is there a map of the earth?” When he was older, his parents sent him to Athens to study, and when he was 30 he was hired by Ptolemy III to tutor his son in Alexandria. Eratosthenes thrived in the academic environment of Alexandria, and eventually became head of the famous library there. While in that post he began to create the first-ever comprehensive geography book. He filled it with a great deal of information, but felt it lacked the most important information: the circumference of the earth. This was no easy problem to solve, but Eratosthenes found a way, and his answer was within 200 miles of the answer we get today using modern technology!

Uses: This book could be used in a variety of ways in the classroom. In particular it would be a great way to introduce finding the circumference of a circle. Eratosthenes made predictions about the circumference of the Earth by using observations he made with smaller round object, a grapefruit. I would have students break into small groups, and give each group round objects of different sizes (balls of different sizes: golf, tennis, soccer, basketball; grapefruit, oranges, grapes) and measure their circumference using string and a ruler. Each group would have a small and large object, and would measure the small object first and then make predictions about the circumference of the larger object, as Eratosthenes did. They would then measure the circumference of the larger object and see how accurate their predictions were.

It could also be used in connection with a geography unit, to show how important math was, and still is, for determining distances and creating maps, or in a world history unit, to illustrate the contributions of the Greeks to mathematics.