Last week a close friend moved to the west coast. She had been living there for a few months, but now the move was official. As I reflected on our friendship, my eyes became fixed on a photo hanging in my office. In the photo, which I took in Santa Monica, a man and woman are riding bicycles on the same path, but going in opposite directions. I looked at the photo again and wondered if the path is a circle that would allow the riders to meet again, or if the path is a straight line that will have them riding in opposite directions for the rest of time.