WASHINGTON - Astronomers have stumbled upon a tremendous hole in the universe. That's got them scratching their heads about what's just not there. The cosmic blank spot has no stray stars, no galaxies, no sucking black holes, not even mysterious dark matter. It is 1 billion light years across of nothing. That's an expanse of nearly 6 billion trillion miles of emptiness, a University of Minnesota team announced Thursday. Astronomers have known for many years that there are patches in the universe where nobody's home. In fact, one such place is practically a neighbor, a mere 2 million light years...