Have you ever wondered what holds the ocean on the Earth? Or what makes the Earth round? Perhaps you've thought about what holds humans to the ground? Host Bill Nye provides the explanation for these and other questions about the Earth's gravity.

Originally an episode of the television program Bill Nye, the science guy. Features: fully indexed "chapters" correlated to National Science Standards; interactive glossaries and quizzes; bonus footage of never-before-seen segments, interviews, and demos; on-disk implementation guide.