Jackie Jones, age 11, of Prospect, N.Y., for his question:

Does a falling stone make a sound in an empty room?

This brings to mind a trick question that teachers may ask of their science students. Does a falling tree make a sound if there is no living animal or person within a hundred miles? Many thoughtful students assume that sound must be heard before it can be called a sound. But this is not so. The tree falls and bangs the ground whether there is anyone to hear it or not. The vibrating echoes of the fall pass through the ground in any case.

The same holds true of the stone that falls down with a bang in an empty room. The fall produces sound waves in the air whether anyone is there to hear them or not. The bang causes the floor to shiver with small vibrations.