Twenty years after Stephen Hawking's 9-million-copy selling A Brief History of Time, pioneering theoretical physicist Sean Carroll takes our investigation into the nature of time to the next level. You can't unscramble an egg and you can't remember the future. But what if time doesn't (or didn't!) always go in the same direction? Carroll's paradigm-shifting research suggests that other universes experience time running in the opposite direction to our own. Exploring subjects from entropy and quantum mechanics to time travel and the meaning of life, Carroll presents a dazzling new view of how we came to exist.