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A Belt Size of 250,000 Stades

Any idea how one can measure the circumference of the earth? Eratosthenes of Cyrene accomplished it in about 200 B.C., using a measurement lengths called "stades," or the length of stadiums during that time period in Greece.

You can do it in a similar way today, combining your data with others throughout the world. The project, known as the Noon Day Project, has large groups of students measure shadows cast by a meter stick and then compare/combine their results....the result being a good estimate of the circumference of the earth.

The project occurs twice a year, so you need to coordinate times as well:

  • Time Frame: March 7 April 11
  • Fall Time Frame: September 7 October 11
The Project is coordinated by The Center for Innovation in Science and Engineering at the Stevens Institute of Technology. So, you need to register (It is FREE) in order to participate with the full group. But, if you do not want to register, you can still do the measuring experiment and calculations yourself.

Also, while you are at it, why not:

  • Watch the related Carl Sagan video, to gain a historical perspective (NOTE: Many other online videos exist as well, but I enjoy Carl Sagan.)
  • Read further about Eratosthenes of Cyrene, as he made many contributions to mathematics...think "Sieve"!
  • Explore other informal techniques for measuring the circumference of the earth, using sunsets, Polaris (brightest star in Ursa Minor), and GPS.

So, how close were you?