|Measuring shadows in Passic, NJ (2006)
"I’ve wanted to do this experiment ever since I was a sophomore in high school, and heard of how Eratosthenes was able to measure the circumference of the earth just by looking down a well in a couple of towns in Egypt 2000 years ago. A few years ago, when I was at a boarding school, I even got up on stage and challenged the students to come with me to measure the earth with a stick, but somehow, I never followed through. This year, I had the equinox marked on my calendar, and contacted my reliable, physics partner in crime, Frank Noschese. [...] We thought it would be great to give skype a shot, and try reproduce the Eratosthenes measurement between our two classrooms." (Read John’s entire blog.)I too was inspired to recreate the measurement way back in 1972. Here’s what I wrote about it iin my book “The Wannado Curriculum” starting on page 100:
"In 1972, I came across an article in an issue of NCTM’s The Mathematics Teacher that described one teacher’s effort to collaborate with another school in an attempt to duplicate the astonishing experiment in which Eratosthenes successfully measured the circumference of the earth from Alexandria, Egypt, in approximately 200 BCE. I was inspired to try the activity with my second-year algebra class. I attempted to involve two schools—one in Michigan and the other in Florida—but sadly, nothing materialized.
Fast forward to 1995. While creeping along the Internet (surfing was in its infancy), I read that a high school mathematics teacher in Illinois was hosting something that she called the Noon Observation Project. It turned out to be a worldwide collaboration among schools that sought to recreate what Eratosthenes had done so long before. Because the experiment required participants to measure shadows at about the same time (when the sun was at its highest point in the sky), “real-time” communication was extremely important."
Fast Forward to today. You too can recreate the measurement! It's a great way to kick off the school year with your students. The easiest way to do this is to participate in the World Wide Noon Day Observation Project starting this week.