Bill shows how humans measure time with the help of "Beverly Hills 90210" heartthrob Ian Ziering and comedian Ellen Cleghorne. When he's not demonstrating how to make a water clock, Bill is explaining Einstein's Theory of Relativity. The DVD has extra features: fully indexed "chapters" correlated to national science standards, interactive glossaries and quizzes, bonus footage of never-before-seen segments, interviews and demos, Spanish translation, and on-disk implementation guide. .