Measuring the Earth

Peter Copeland

University of Houston

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- Scientific Accuracy
- Alignment of Learning Goals, Activities, and Assessments
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Initial Publication Date: May 19, 2008 | Reviewed: November 2, 2013 (see revision history: 2 events)

Summary

With a colleague at the University of Kansas, we measure the size of the Earth using the method of Eratosthenese. This is handy because the UH and KU campuses are almost directly on a N-S line.

Physical | College Introductory

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Context

Audience

This is a demonstration I have done in Physical and Historical geology classes. Both are classes with mostly non-majors.

Skills and concepts that students must have mastered

none

How the activity is situated in the course

a stand alone exercise

Goals

Content/concepts goals for this activity

I want to demonstrate that simple measurements can be used to work out big problems. I also use the demonstration to illustrate the problems of precision vs. accuracy and the effect of error magnification. I have several students make the measurements with mm precision and then show how the differences in the values correspond to different final estimates of the size of Earth.

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description of the activity/assignment

Because the campuses of the University of Kansas and the University of Houston are almost directly on a N-S line we can duplicate many aspects of the classic measurement of Eratosthenese in determining the circumference of the Earth. We use a web cast (backed up by cell phones) to communicate between the two campuses in real time. We measure the shadow of a 2 m stick in both locations at the same time and then go through the math required to calculate the size of the planet.

Determining whether students have met the goals

We don't do this during regular class time because it is best to do it near noon and because we have to coordinate between classes on different campuses. Therefore I don't think it is appropriate to require students to be present at the demonstration. However, to give credit to those that show up I as a question on the test that will be considered separately as extra credit.

More information about assessment tools and techniques.