## Wednesday, January 26, 2011

### 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.

Debbie said...

I chuckled over your son trying to walk across the living room in equal stride. Tell him to practice, my dad could walk off in yards to measure exactly where a tree would fall when cut down. I never did figure that one out.

Ticia said...

That is the right pronunciation, or at least the one I learned in high school.

I love how your kids tried to keep the same stride. It's hard.

Christy Killoran said...

Very interesting. I don't remember learning about bematists, fascinating!

Unknown said...

Oh! I have to get this book. Wonderful lessons!! Thank you for sharing.

Joyful Learner said...

I don't know what I learned in high school but this wasn't it!

Valerie @ Inner Child Fun said...

This is so interesting!! Thanks for sharing, and the timeline is looking great! :-)

SYoung said...

Hi... I just found your blog and love it! Do you have more information about the time line your family is creating in another post? What a great idea... I would love to read more about it.

An Almost Unschooling Mom said...

OootSnoot - Firstly, thanks! Secondly, yes, I've mentioned the timeline in a few posts before - if you start here:

http://almostunschoolers.blogspot.com/2010/02/more-timeline-fun-american-history.html

You can work your way back through the links to the other posts :)

Natalie PlanetSmarty said...

Fascinating stuff for older kids, and I learned something new (bematists) today. How fun it is when history, geography, math and literature naturally merge into one.

Jeff Schmitz said...

Great post on a great topic of history and science. Thanks.

An Almost Unschooling Mom said...

Raising a Happy Child - It's what unschooling is all about :)

Phyllis said...

Fun stuff!! I love that book.