Everyone knows that there are things no one can see, for example, the air you're breathing or a black hole, to be more exotic. But not everyone knows that what we can see makes up only 5 percent of the Universe. The rest is totally invisible to us.

The invisible stuff comes in two varieties--dark matter and dark energy. One holds the Universe together while the other tears it apart. What these forces really are has been a mystery for as long as anyone has suspected they were there, but the latest discoveries of experimental physics have brought us closer to that knowledge. Particle physicist Dan Hooper takes his readers, with wit, grace, and a keen knack for explaining the toughest ideas science has to offer, on a quest few would ever have expected: to discover what makes up our dark cosmos.

Dan Hooper is an associate scientist in the theoretical astrophysics group at the Fermi National Accelerator Laboratory in Batavia, Illinois, where he investigates dark matter, supersymmetry, neutrinos, extra dimensions, and cosmic rays. Originally from Cold Spring, Minnesota, Dr. Hooper received his PhD at the University of Wisconsin and was a postdoctoral fellow at the University of Oxford in the United Kingdom. He is the author of Dark Cosmos: In Search of our Universe's Missing Mass and Energy, a SEED magazine Notable Book.