Gravity by Jason Chin is amazing. It's a picture book, but in the non-fiction area, so teachers, heads up! If you want to use his books in your classroom check here, for standards and ideas. The art is incredible along with the topic. What a great book to introduce the science and then expand on it with fascinating watercolors. It will catch your student's curiosity and encourage them to find out more about the subject. There are author notes and a bibliography in the back. Chin has an awesome eye for perspective and is so clever about capturing our mind with wonder. I'll use this book with preschool to 4th or 5th graders.