Winter, spring, summer, and fall—Earth experiences them all! But what about Mars? Scholars compare the planets in terms of distance, tilt, and rotation during a lesson from PBS's Space series. Great visual models of Earth and Mars, plus...

Ever wonder why Pluto isn't considered a planet? Or how large the Earth is compared to the other inner planets? Explore the universe with a series of projects that simulate different aspects of our solar system. The activities require...