It's not difficult to imagine a line. First, close your eyes. Remember when you were a child and noticed everything about the world: the light stretching just so across the baseball field, the white dog fur on the kitchen floor, the map-like lines on your mother's stomach.             It can't be that hard to see a line.             Open your eyes. Do you see it yet?______Hold it up to the window. To the bedroom lamp. You're searching for light. Take it outside. Squint harder.______Tell your husband, I think I see something. Watch as he squints. I don't see it, he says. Get angry with him. Thi