The Patch of Sky That Wasn't Empty

In December 1995, astronomer Robert Williams made a decision his colleagues thought was foolish. As director of the Space Telescope Science Institute, he chose to aim the Hubble Space Telescope at a tiny, seemingly empty patch of darkness in the constellation Ursa Major — a sliver of sky no bigger than a grain of sand held at arm's length. For ten consecutive days, Hubble stared into what appeared to be nothing.…