Experiment

Eratosthenes, who lived from 275-194 BC was the chief Librarian at the library in Alexandria, Egypt. He heard about an interesting phenomenon that occurred in Syene, a town several hundred kilometers to the south of Alexandria. At noon on the longest day of the year vertical poles cast no shadow. Even in the deepest wells, the sun could be seen reflected on the water at the bottom. On that same day in Alexandria there were shadows at noon.

Follow the links below to find out how he used this information to make a pretty accurate calculation of the circumference of the Earth and how you can join an exciting collaborative Internet project going on right now to replicate and explore this legendary investigation.

How Long is the Day - Experiment

Measuring the Circumference of the Earth: The Noon Day Project
This project offers teachers and students an opportunity to recreate his amazing experiment by collaborating with teachers and students from other schools throughout the world.