A CIESE Collaborative Project

Reference Material



Here are some titles you will find in your favorite book store, library or on-line.

  • Ferguson, Kitty. Measuring the Universe.
  • Lasky, Kathryn. The Librarian who Measured the Earth. A must buy!
  • Diggens, Julia. String, Straight Edge, and Shadow (p. 149-154)
  • Sagan, Carl. Cosmos. The book and video from a PBS series of the same name.
  • Coggins, Jack. By Star and Compass. The Story of Navigation (p. 64-69) Good explanation and diagrams.
  • Moore, P. and Brinton, H. Exploring Maps. p. 13-15
  • Gullberg, Jan. Mathematics: From the Birth of Numbers. p. 467 Did Eratosthenes really get the measurements right? According to Gullberg, historians have done some fudging to make Eratosthenes look good. Since his method was correct, why not give him the benefit of a doubt that he used the right length for his unit of measure - the stadion? Apparently there were at least seven different lengths for a stadion at that time.
  • Adler, Irving. Shadows
  • Gardner, Robert & Webster, David. Shadow Science (Doubleday, 1976). The authors take a fresh look and gives us clues about the world around us. Titles of chapters include: Telling Time with Shadows, Finding North with Shadows, and Night is just a big Shadow. Contains a lot of puzzle pictures. Great book.
  • Severn, Bill. You and Your Shadow.


  • Charischak, Ihor. In the Spirit of Eratosthenes: Measuring the Circumference of the Earth. Learning & Leading with Technology, V. 25, N. 6 (ISTE, March, 1998)
  • Charischak, Ihor. Bringing the Vision of 21st Century Collaborative Projects Into Today's Mathematics Classrooms. Paper presented at the NCTM's Electronic Format's Group Conference, Reston, VA, June, 1998

Relevant Websites

  • All about the Autumnal Equinox
  • Four Seasons: The Movie: Nice animation of the earth moving through the seasons as would be seen from the sun
  • Print Paper rulers for your measurements: Hope Martin from Columbia, Missouri shared this one.
  • Measuring the Globe: An Historical Activity: Eratosthenes' measurement of the earth, in a form easy to use by teachers. (You will need to register. Once in the Convergence site, search for Eratosthenes.)
  • Read about the Noon Day Project in the News

Other Eratosthenes Measurement Projects

  • The Eratosthenes project - Sonoma State University (1999-2000)
  • A similar project that is done by James D. Meinke, Assist. Professor of Educational Technology, Baldwin-Wallace College, Berea, Ohio.

Participants Websites



Aristotle believed the earth was round, but he low-balled how round it was. King Ptolemy of Egypt offered an estimate of 18,000 miles which Columbus used to his advantage in negotiating for his trip. (From a PBS interview with author of Don't Know Much About the Cosmos.)