This activity, from the Real World Learning Objects Resource Library, helps students estimate the circumference of the earth by recreating "Eratosthenes' amazing experiment utilizing data generated from the...

The International Solar-Terrestrial Physics Science Initiative (ISTP), a collaborative effort by NASA, the European Space Agency (ESA), and the Institute of Space and Astronautical Science (ISAS) of Japan, has recently...

This reference provides an introduction to the geoid, the equipotential surface of the Earth's gravity field which best fits global mean sea level. There is a narrative of early attempts to describe the geoid, and...