Why Is the Sky Blue?This enthralling early encyclopedia answers more than 200 questions that children ask about science This revised edition of DK's science encyclopedia answers children's biggest questions about scientific exploration, covering forces and energy, materials, the human body, the living world, and our planet. Why does chocolate melt? Where does wind come from? How do we know dinosaurs existed? This fully updated, fact packed kids' book, ideal for ages 7 9,