It's callled a Foucault Pendulum. They have a beautiful one at the California Academy of Sciences in Golden Gate Park, to show that the Earth rotates. Each time my family goes to the museum we make it a point to see it. I have come to expect kids, squatted on the floor alongside their parents, watching the pendulum swing. It swings continuously, slowly tracing a circle. What the small crowd gathers to see are the little pins arranged at the perimeter of the circle. Every hour or so, the pendulum knocks down one little pin. What makes the exhibit enjoyable is the reaction of the audience.
The crowd gathers like clockwork, even though we know the pin's fall is as predictable as sunrise. Tantrums vanish, eyes grow wider with expectation as the pendulum comes closer to a pin. My daughter, who has the attention span of a butterfly, stands transfixed by it. With every swing, we expect that the pin's end is near. Yet somehow, the pin stands -- like a resolute little David, against the Goliath pendulum.
The crowd jumps with expectation, then gives out a resigned "Oh that was close!" Finally, when the pin falls, the children's faces are jubilant, as though they have experienced something profound. To me, it was the feeling I get after reading a very good book.
It is the pendulum's lethargic buildup of suspense, like chapters in a good book, that draws the crowds, and the surprise that something so small could withstand the onslaught of something so big. Like a tenacious little dandelion growing in a busy road.
It is a simple thing, but we breeze through so many great things in our lives -- a museum exhibit, a nice landscape on the way to work, or that severely dog-eared library book. That day, the Foucault's Pendulum succeeded in slowing us down, and stayed with us like a little mile marker in time.