In Who Knew? Physics, you'll learn the mind-blowing answers to questions about the way our universe works. They might be questions you have always wanted to ask, or maybe ones that you have never considered until now. But they will all leave you saying, "Who knew?" So if you're bursting to know where the sky becomes space, or if a butterfly could really cause a tornado, this is the book for you. These pages are packed with information, and each chapter concludes with a quiz to test your knowledge so that you will be able to dazzle your friends and family with some incredible insights.