Pendulum

Pendulum, originally uploaded by William 74.

The Foucault pendulum display at the Museum of Science and Industry in Chicago. As the steel bob swings back and forth, it's plane doesn't change at all-the Earth rotates underneath it, eventually bringing the ball into contact with one of the posts around the circumference of the circle. There's always a crowd around it, and every once in a while you'll hear some cheering as a post gets knocked over, but I've never managed to see it happen.

I always thought the Foucault pendulum was neat. When I was a kid this display was in one of the stairwells, and it knocked over these little metal things that looked like Parcheesi playing pieces. Not these fancy stainless steel hinged things! (shakes cane angrily)