The other day I mentioned our trip to the National Mall for the Book Festival. That mall downtown is one of my favorite places. Having grown up just outside the nation’s capital, I spent many a Sunday on what’s often called America’s front lawn, enjoying the free museums. My parents had moved to the area when I was a toddler, and my father had never gotten over his delight at all the things there were to see and do in D.C. He used to pile my brothers and sisters and me into the car early Sunday morning, letting my mother sleep in, and take us sightseeing. I still remember standing on the second floor balcony at the Museum of American History, and watching the giant Foucault’s pendulum they used to have there, swinging back and forth, knocking over pegs they had laid in a great circle on the floor. The trick of it was that the pendulum was always moving in a straight line; it was the world that was turning, inching slowly forward until another peg was in the way, ready to be toppled. I could never get enough of that pendulum. Besides the hypnotic quality of its rhythmic back and forth, the idea that I was standing on a turning world – and could see it – just amazed me. A few years ago, the Smithsonian Institute renovated the museum, trying to focus it more on the American experience, and the pendulum went into storage. When I asked a guard there why, he said: “It was French. This is the American history museum.” Now, it’s still a great museum – in some ways better than ever, with some fabulous living history performances that liven the place up. But I miss that pendulum. Even if it was French.