For the past 10 years, physicists have been banging their heads against the wall, trying to understand one of the greatest new mysteries of the cosmos: Why is the universe pulling itself apart at an ever-increasing rate? Is this a mysterious new force - dark energy - or must we alter our most fundamental theories of time and space? For 30 years we have been struggling to understand the nature of dark matter - the mysterious invisible matter that outweighs 'normal' matter 10 to one and fills the 'empty' spaces in our galaxies. For 50 years we have grappled with the seditious theory of gravity, which has failed to fall in line with all other known forces. But the biggest mystery of all time - one that dates back to man's earliest writings - is our universe and physicists are the detectives trying to piece together disparate clues that continually turn our view of the cosmos upside down. THE UNKNOWN UNIVERSE describes how physicists view the creation of our universe, when space and time itself came into being and how stars formed and exploded, seeding the universe with new stars and galaxies, including our own solar system. This book also explores some of science's newest theories and their implications, such as string theory, which suggests a seemingly bizarre world of 10 dimensions, yet may explain quantum gravity. It also describes the biggest conundrums physicists are grappling with today. From dark matter to cosmic rays, from black holes to wormholes, Dr. Hammond explains how these vexatious riddles arose.