The universe has a huge hole in it that dwarfs anything else of its kind. The discovery caught astronomers by surprise. The hole is nearly a billion light-years across. It is not a black hole, which is a small sphere of densely packed matter. Rather, this one is mostly devoid of stars, gas and other normal matter, and it's also strangely empty of the mysterious "dark matter" that permeates the cosmos. Other space voids have been found before, but nothing on this scale. Astronomers don't know why the hole is there. "Not only has no one ever found a void...