Book excerpt: Our universe is filled with important questions that both captivate the minds of scientists and capture popular imagination. This volume traces many of these questions, shedding light on everything from time travel to the nature of atoms. Divided into sections called Physical Matter and Forces, Space, Human Body, Earth, Other Life-Forms, and Human Triumphs and Troubles, the book elucidates the latest scientific theories in easy-to-follow, engaging terms.