Gravity dominates the universe. It holds the Earth, the Sun, and the Milky Way together, and it keeps our feet firmly planted on the surface of our planet. When an object goes up, it is pulled back to Earth by gravity. These facts make it easy to conclude that gravity is a strong force, but it is actually a very weak force whose confusing and contradictory nature has stumped many investigators. Gravity explains how two of the greatest scientific minds in history--Isaac Newton and Albert Einstein--finally unraveled most of the mystery surrounding this peculiar force, and how scientists today are continuing to search for answers to the remaining questions.