Monday, May 8, 2017

Eratosthenes' Method = Fun

One of our high school math teachers shared an email with me she had received from a teacher in Chicago. Of course I jumped at the chance to take math outside of our classroom and {bonus} outside our state!

Yes, we would LOVE to measure the world using the sunshine! So the emailing started to set a date for estimating the Earth's circumference! We needed to sync our watches so our measurements would be taken at the same time. It needed to be when the sun was due south so we did 12:47 or solar noon. We used a meter stick with a level to be sure we had the stick vertical. The meter stick is one leg of the triangle and the shadow is the other leg. We had to determine the angle that is opposite from the shadow. That angle is the key to measuring the Earth! I knew I needed to call in the big dogs for this because my 8th graders' minds were going to be blown! Enter my amazing Math Consulting Teacher and 8th grade science neighbor, Go Team!

The meter stick was held vertically on the sidewalk, using the level to be sure it was as vertical as possible, putting the shadow as horizontal as possible.

Since both our stick in Alabama and their stick in Illinois were vertical, they were pointing to center of the earth. We needed to find the angle that our two meter sticks created.

At earth's distance, sunlight approaches parallel, so we assumed it was parallel for our purposes. ANGLE 1 (in Country Club Hills, Illinois) minus ANGLE 2 (in Foley, Alabama) would give us ANGLE 3 (in the center of the earth).

There is my Math Consulting Teacher blowing minds! After he walked them through Eratosthenes' method of calculating the circumference, he talked the kids through finding the angles and setting up the proportion. They used google maps to see where the school was we were working with. The whole thing was amazing!

Parallel sunshine and math with kids saying this was so awesome, not a bad day at school!


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