The Librarian Who Measured the Earth Activities

We learned how to measure the circumference of the earth, yesterday. Or, at least, how it was done over 2000 years ago, in Kathryn Lasky's The Librarian Who Measured the Earth.

The librarian is of course, Eratosthenes (AIR-uh-TOS-thuh-neez, if the pronunciation guide in the book is to be trusted). He measured the circumference of the earth, with amazing accuracy, in 240 BC, using only his mathematical skill, knowledge of a round earth, a couple of shadows, and a sure footed young man to pace off distances for him.

The children were interested in the fact, that there were people, called bematists, trained to walk with equal steps, so they could accurately pace off distances.

They gave it a try themselves marching across our living room, and then back again, and discovered not only did the number of steps they counted not match each others', but not all of them were able to keep a steady number from one side of the room to the other.

The bematists, Eratosthenes used, kept a steady count for a distance of about 800 km. That's pretty amazing.

We also had to test the idea, that the amount of curve to the earth could change the amount of shadow, cast by the sun, directly overhead.

We put two candles into a flat piece of playdough, and held a flashlight high above them, in the bathroom, where there aren't any windows, to let in side light.

While the playdough was flat, there were no, or almost no shadows, on either candle.

But, if we curved the playdough, one candle cast a long shadow, while the other didn't have any.


Carl Sagan actually does a better job of this experiment, using a map of the area, where the original experiment occurred. I might not always agree with Carl Sagan, but we enjoyed the clip below.



And, since the The Librarian Who Measured the Earth, has a good dose of history to go along with the math, we printed out a picture of the cover art, to cut out...


...and add to our timeline. I should probably mention too, that the book, while full of very engaging illustrations, was a touch too long, and detailed for the younger children.


You can find more fun with history, and geography at this week's History and Geography link-up, hosted by Children Grow, Children Explore, Children Learn.

Or, if you're really interested in better understanding the math Eratosthenes used to measure the circumference of the earth, check out this NASA for Kids clip, that not only explains it, but suggests another great hands on math activity to try at home.



It's great to be a homeschooler.