Book excerpt: Gravity and Gravitation is a physics book that is written in a form that is easy to understand for high school and beginning college students, as well as science buffs. It is based on the lessons from the School for Champions educational website.The book explains the principles of gravity and gravitation, shows derivations of important gravity equations, and provides applications of those equations. It also compares the different theories of gravitation, from those of Newton to Einstein to present-day concepts.