"There is a lit candle in an elevator mounted on a bracket attached to the middle of one wall (say, 2" from the wall). A drop of mercury is on the floor. The cable snaps and the elevator falls. What happens to the candle and the mercury?" From: http://research.microsoft.com/~mbj/Smiley/Joke_Thread.html Maybe the question was meant to be a joke, but it doesn't have to be.