News Astronomy & Earth Science Classroom Activity

Project Worldview announces a new addition to its website: a page for Astronomy and Earth Science teachers. Of the links to be found there, perhaps the one of most interest is to a new classroom activity "Making Observations (New Mexico Style) to Estimate the Size of the Earth." While travel and night-time observation enhance this learning activity, it can be done entirely in the classroom. Students will gauge the Earth’s circumference using the same method employed by Greek geographer Posidonius around 100 BCE. He measured the altitude of the bright southern star Canopus at its high point (culmination) at two different locations, then used simple math based on geometry.

From the 35 degree latitude of Albuquerque, the highest Canopus gets is a mere 2 degrees in altitude above the horizon. Then, if you hold your thumb at arm’s length, it should just fit between Canopus and the horizon If you’re farther south—say at the 32 degree latitude of Las Cruces—you’ll see this star a bit higher in the sky. How much higher? Students can be challenged to make these (or similar) observations (or rely on computer simulation), compute the Albuquerque—Las Cruces distance based on a New Mexico map, and use all of this to get an estimate for the Earth’s circumference.

Do we live on a small planet? Answers to this question have both modern environmental and ancient historical connections—including Columbus’s underestimate of the Earth's size and the unexpected consequences! The new activity from Project Worldview can help students get a sense of how big the Earth is and how one’s eyes reveal this. The activity can be adapted for use outside New Mexico for locations in the 31^o to 36^o N latitude range. You can find a link to this activity at www.projectworldview.org/astronomy education.htm