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How Big is Earth?

posted Jan 13, 2015, 3:46 PM by Bonnie Thurber   [ updated Jan 13, 2015, 3:58 PM ]
Alexandra Egypt tower
The iCollaboratory team is pleased to announce that Bonnie Thurber, as project leader, has been awarded funding support for "How Big is Earth" from IAU-OAD under Task Force 2: Children and Schools.

The project runs February-July 2015 with students participating in March and  again in June (Southern Hemisphere and Summer School). 

Using only the sunlight striking the Earth and a wooden dowel, students can measure the circumference of the earth. Eratosthenes did it over 2,000 years ago. In Cosmos, Carl Sagan shared the process by which Eratosthenes measured the angle of the shadow cast at local noon when sunlight strikes a stick positioned perpendicular to the ground. By comparing his measurement to another made a distance away, Eratosthenes was able to calculate the circumference of the earth. (See Carl Sagan's depiction of this process at (

YouTube Video

Students will be able to do science the same way Eratosthenes did in the iCollaboratory activities. A notable project in which this was done was The Eratosthenes Project, conducted in 2005 as part of the World Year of Physics; in fact, we will be drawing on a simplified version of the teacher's guide developed by that project. The difference between that activity and How Big Is Earth? is the online learning environment provided by the iCollaboratory where teachers and students can collaborate, share data, and reflect on their learning of science and astronomy. We will also maintain and share an ongoing database of student measurements. We will collect data on both teacher and student learning from surveys, discussions, and self-reflection done online. Students in each school will collaborate with students around the world; during the first year, schools in six countries will participate. We will share our research about the kinds of learning that takes place only in global collaborations.

If you are interested in having your middle school students participate, please contact

Thank you,

Bonnie Thurber and iCollaboratory Team