Dark Cosmos: In Search of Our Universe's Missing Mass and Energy

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 l...