Cambridge Discovery Education Interactive Readers are the next generation of graded readers - captivating topics, high-impact video, and interactive exercises designed to motivate and engage. Are humans alone in the universe, or is intelligent life out there somewhere? Find out how people throughout the years have explored this age-old question. Use the unique code inside the book to access the online reader, complete with videos and interactive exercises. Word count: 1934. Lexile: 780L