One night, two hours after sunset, I flew from Chicago to Pittsburgh. For about 10 minutes, before we reached Lake Michigan and left the city behind, I saw a sea of twinkling lights outside my window. I saw cars and trucks moving slowly down big city blocks. Then we reached downtown, which was even brighter. The skyscrapers sparkled, and looked like they were made of diamonds. Looking down, everything appeared entirely within my control, like I could reach out and rearrange the whole city with my fingers. And then we reached the big dark lake, and I could see nothing but black.