Me and My Human, 2004
Skaters at the Lasker Rink in Central Park are dwarfed by their shadows, at least in this aerial view, Feb. 22, 2004.
Click on image for a larger view.

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Longitude And Latitude!
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Resources that discuss Eratosthenes and his Measurement
  • Following in the Footsteps of Eratosthenes: Measuring the Circumference of the Earth Very impressive. In several different languages no less.

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.
I found these books in the children's section of my local library. If you find any good books, let me know and I'll add them to this list.
  • 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. 
Articles Relevant Websites
Other Eratosthenes Measurement Projects

Participants Websites

Read about the Noon Day Project in the News


  • Cosmos #1: The Shores of the Cosmic Ocean (1980) Carl Sagan Productions/PBS, 1/2" video Color 1 cass., 60 min. Explores the universe from clusters of galaxies to the Milky Way and earth. Discusses early scientific discoveries concerning measurement of the earth's circumference and its spherical nature. Journeys through time from the Big Bang to the present. Included in this video is a wonderful presentationn of Carl telling the Eratosthenes measurement story. See link below (with French subtitles.)
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.)

Somewhere on or very near 
the Tropic of Cancer or the Tropic of Capricorn. (Why?)
Congratulations to the students of Mr. Langstaff at Hendrix Junior High in Chandler, AZ for being the first to come up with that.
Additional websites and other strange phenomena
Finding your latitude and Longitude

If I dig a very deep hole, where I go to stop?
Was your mother right when she said that if you dug a hole through the earth to the other side you would wind up in China? Assuming you are in New York City, how close to China would you end up? Not sure? Try this completely "stupid" use of Google Maps.

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