Mike Stukel, age 12, of Ottawa, Ontario, Canada, for his question:

What exactly is a lodestone?

"Lode" was an old English word for journey, and a lodestone is a mineral that can help a traveler to pursue his journey in the right direction. You've already guessed what it is. The lodestone discovered in ancient days was a magnet. When a sliver of magnetized iron is suspended from a string, it always swings around until one end points to the earth's north magnetic pole, The other end, of course, points to the opposite south magnetic pole. This gadget is the basis for the magnetic compass. When you have verified which way is north, you can figure out the other directions. Facing the north, east is to your right, west is to your left and south is behind you.

The words "lodestone" and "lodestar" are not commonly used in modern English, which seems a pity. A lodestar, naturally, performs somewhat the same function as a lodestone but from a celestial point of view. North of the equator, Polaris is the dependable . lodestar that points the northward journey. Navigators in the know also use other lodestars to verify various directions north and south of the equator.