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.
