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Stevens Institute of Technology

Estimate the Circumference of the Earth
using Eratosthenes' Method

Project Overview

By the third century BC, scholars realized that the earth might be round rather than flat and believed that the earth was a sphere. One empirical piece of evidence they noticed was that sails disappear last when observing ships approach the horizon. But how large was the earth? No one had any idea.

It wasn't until over 2200 years ago that Eratosthenes (276-194 BC), the chief librarian in Alexandria, Egypt, discovered a remarkably simple method for measuring the north-south circumference of the earth. He did this by measuring the sun's angles at two different positions on the earth, Alexandria and Syene (now Aswan in Egypt), at the same time and then calculating the central angle to determine an empirical value for the circumference of the earth.

During this activity, students will recreate Eratosthenes' amazing experiment utilizing data generated from the Stevens-sponsored telecollaborative project the Noon Day Project.


(NOTE: this RWLO is based on the Noon Day Project)

Copyright 2005 Stevens Institute of Technology
Center for Innovation in Engineering & Science Education, All Rights Reserved