Blog Post 3: Mathematics in a Story

1.  The Librarian Who Measured the Earth by Kathryn Lasky and Kevin Hawkes tells the story of the Greek mathematician and philosopher Eratosthenes, who created the field of geography and was the first person to calculate the circumference of the Earth.  While studying in Athens, Eratosthenes became well known for his incredibly accurate chronologies of Greek history.  When he was 30 years old, he moved to Alexandria and later became the Chief Librarian of the Library of Alexandria.  Eratosthenes was determined to create the first book about geography, and more specifically, to measure the circumference of the Earth.   By using mathematical principles related to circumference, arc, angles, and measuring shadows, Eratosthenes determined the circumference of the Earth and created the first book of geography, Geographica. 

2.  Eratosthenes knew that in order to find the circumference of a circle, he could calculate the length of one arc along the circle and then determine how many arcs comprised the circumference.  To determine how many arcs were necessary, he could measure the inside angle of one of the arcs and divide 360 degrees by that number.  Eratosthenes heard that on June 21, the sun would shine directly onto a well in Syene, a city in southern Egypt, and cast no shadows.  Eratosthenes decided to measure the angle of the shadows in Alexandria at noon on June 21, and this angle would be equal to the inside angle of the arc (the arc was the distance between Alexandria and Syene).  He measured an angle of 7.2 degrees.  360 divided by 7.2 equals 50, so he knew that the distance between Alexandria and Syene multiplied by 50 would equal the circumference of the Earth.  He measured the distance between the two cities by hiring bematists, who are surveyors trained to walk with equal steps.  The distance was about 5,000 stades, or 1/10 of a mile.   Through his calculations, Eratosthenes determined the circumference of the Earth to be 24,662 miles. When the circumference of the Earth was measured using modern technology, Eratosthenes' calculations were only off by about 200 miles, even though he measured the circumference over 2000 years ago.

3. Literature is an effective way to teach mathematical concepts to children because the illustrations and story-telling show them that mathematics is not a dull concept.  Children who are visual learners are stimulated by pictures and physical explanations, and literature is effective at teaching mathematical concepts to visual learners.  Additionally, in The Librarian Who Measured the Earth, the authors write that Eratosthenes loved to question the world around him, which is what led to his discoveries.  By instilling the values of curiosity and questioning into children, literature teaches them that math is not a stagnant subject.  There are always new discoveries to be made, which makes the subject exciting.