In the New York Times best-selling book from the creator of the wildly popular webcomic xkcd, Randall Munroe gives hilarious and informative answers to important questions you probably never thought to ask. Fans of xkcd ask Munroe a lot of strange questions. What if you tried to hit a baseball pitched at 90 percent the speed of light? How fast can you hit a speed bump while driving and live? If there was a robot apocalypse, how long would humanity last? What if everyone only had one soulmate? What would happen if the moon went away? In pursuit of answers, Munroe ran computer simulations, pored over stacks of declassified military research memos, solved differential equations, and consulted with nuclear reactor operators. His responses are masterpieces of clarity and hilarity, complemented by signature xkcd comics. (They often predict the complete annihilation of humankind, or at least a really big explosion.) Far more than a book for geeks, What If? explains the laws of science in operation in a way that every intelligent reader will enjoy and feel much smarter for having read.