How does the sun determine the Earth's seasons? This is the question that the National Geographic Education site seeks to answer with a lively 35-minute activity designed for students between the ages of seven and eleven (second through fifth grade). In the activity, students use polystyrene foam balls and light bulbs to simulate the intensity of the sun's energy on the earth's surface. The site is divided into four basic sections so that educators can easily absorb the various aspects of the lesson. Readers may like to start with Directions, which provides a run-through of the activity and step-by-step instructions for how to bring in interesting resources and breathe life into these important concepts.