JSC NES School Measures Up
To determine the circumference of the Earth, students measure the shadow cast by sticks
In the third century B.C., the Greek mathematician Eratosthenes used his observations of the sun to become the first person to measure the circumference of the Earth.

More than two millennia later, 35 juniors from the James Madison High School Astronomy Club in Houston arrived at Johnson Space Center on the first day of spring to use his methods and principles to size up the Earth.

Image to right: JSC physicist Jerry Elliot (far left) eyes the angle of the sun's rays, which are measured by three James Madison High School 11th-graders during 2006's Vernal Equinox. James Madison was selected a NASA Explorer School in 2004. Credit: NASA

Previously, JSC physicist Jerry Elliott approached the JSC education office about conducting a simple science project to duplicate Eratosthenes' experiment. After receiving a tour request from the school, JSC's NASA Explorer Schools coordinator Joan Sanders wanted to turn a visit into a learning experience. That's when she contacted Elliott about leading the Eratosthenes activity.

"It was appropriate timing for spring, the Vernal Equinox, and was simple and fun," said Elliott. "I think people have lost things like this that happened thousands of years ago and how advanced and modern the thinking was back then."

"Eratosthenes used the basic idea of geometry to compute these measurements and he was within five to 10 percent of the actual number of the Earth's circumference -- about 24,860 miles," he said. On March 20, shortly before and after 12:28 p.m., known as "local noon," when the sun is the highest in the sky, students planted sticks vertically in the ground outside the Gilruth Pavilion to measure the angle and length of the sticks’ shadows. Those measurements were used to calculate the Earth’s circumference, and then, in turn, the radius and diameter.

"This is where their trig comes in," Aerospace Educator Specialist Lisa Ogle said during the activity. Ogle was one of several JSC employees who helped serve as mentors for the students during their visit.

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Earlier that day, clouds and rain threatened to stall the event, but they cleared just in time for the activity after Elliott, an Osage/Cherokee Indian, said an Indian prayer.

"The students were disappointed at first when it started raining. But once there was a breakthrough in the clouds, one of the students spotted sun in the corner and ran for it," James Madison NES Team Lead Margarita Simon said.

"Since the school started its partnership with JSC in 2004, when it was selected to be a NASA Explorer School, I've noticed an increase in the students' interests in science and math," said Simon. "A few even want to pursue engineering."

"We got to see how the shadows move at different times and how it correlates with the sun. It was great to learn something new and different," said James Madison student Shamara. "It makes you want to share this with people you know and say, 'Hey, look at that. Do you know why it does that?'"
A student measures a shadow created by the sun

In addition to measuring the Earth, students also got to meet some of JSC's employees.

Image to left: To determine the circumference of the Earth, a James Madison High School student first determines the length of a shadow cast during "local noon." This technique was developed by Greek mathematician Eratosthenes in 200 B.C. Credit: NASA

"When the students think of the men and women of NASA, they think 'unreachable.' But after meeting them, they know they have a place here. If we weren't a NASA Explorer School, this might not have happened," said Simon. "This experience has made learning fun. When the kids get more involved, it makes you, as the teacher, want to be more involved and excited. It [the partnership with NASA] has made learning student-centered."

Elliott discovered the Eratosthenes activity while he studied Greek science at the University of Oklahoma. This exercise was done with one school, but there are plans to expand this activity to other NASA Explorer Schools nationwide in the fall. Elliott said he hopes that the students don't just stop at the sun.

"Hopefully they'll continue to discover and explore and think, "What can I do with this information now?' Science is fun. It's not just about discovering and exploring -- there's an excitement in learning. It's not just an academic pursuit -- it's a way of life," he said.

"This activity shows them the relevance of science. It's not just all mystery," Elliott said.

Debbie Nguyen, JSC Public Affairs