August 13th, 2019

Eratosthenes Experiment – Fall 2019

Measure the Earth with your Students

This Fall All Canadian Classrooms are Invited to Measure the Earth! 

A 2000 year old experiment can be easily recreated in your classroom, letting your students get an accurate measurement of the circumference of the Earth! This experiment, based on Greek mathematician Eratosthenes’ work, is simple and easily undertaken during the Fall Equinox. Classrooms around the globe will be participating, giving you the option of sharing your findings, and collaborating with another classroom thousands of kilometers away, through the international campaign Eratosthenes Experiment.

The Genius of Eratosthenes

Eratosthenes was a Greek mathematician living in c. 276 bce — c. 194 bce. He was curious, smart, and paid attention to detail. One day, he learned that on the summer solstice, the sunlight would reach the bottom of a well in a city far away. He understood that this meant the Sun was directly overhead at noon and therefore no shadows were cast. This intrigued him since this was never the case in Alexandria where he lived. Eratosthenes knew that the reason the shadows were different in different cities was that the Earth was round. Based on this information, he measured the shadows in Alexandria and hired someone to measure the distance between the two cities. Using this information, he was able to measure the circumference of the Earth with great accuracy! All that with the only the simple technology of the time!

Credit: ASTROLab du Mont-Megantic

The Experiment

You can easily reproduce the Eratosthenes Experiment with your classroom.  On the fall equinox (Sept. 23, 2019), at local noon, you need to measure the shadow of a stick. This measurement is very simple and can be done with students of all ages (K-12). With this value, as well as the length of your stick, you can then calculate the circumference of the Earth with amazing accuracy!


Credit: Eratosthenes Experiment


Want to learn more?

You can read through the Eratosthenes Experiment Website to get all the steps of the experiment and register your school.

And watch our free webinar on September 11, 2019 to learn all the details firsthand with the opportunity to ask questions. We will provide resources to help you with every step, including what you need to skip any of the math calculations that might be too advanced for your classroom.



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