I was walking yesterday on a trail called “Main Road,” which is a good indication of its degree of difficulty, when I tripped on a small root and fell on my face. I got up, cursed myself for being old and clumsy, and walked on. I realized that I walk inside my head, lost in my thoughts and unaware of my surroundings and the dangers they hold. So I made a Zen-like effort to pay attention to the world around me. It was a cold and beautiful day, more like fall than spring. The trees were still bare, and little was blooming except skunk cabbage along the stream. About 15 minutes later, absorbed now in the nature's beauty, I went down again. Lying there, I wondered, “How do you fully experience the place you are in and still keep moving?” This is an especially poignant question for the elderly, who are in no particular hurry to get where we know we are going, even as time speeds us along the way. Perhaps this is what drove Albert Einstein to his ideas of relativity, in which space and time fuse into one. In a letter to the family of a friend who had died, Einstein wrote, “for us physicists (sic) believe the separation between past, present, and future is only an illusion, although a convincing one." If only he’d left out the last phrase.