Compasses come in various flavours, and originated in the 12th century. Apparently discovered / invented independently by both Chinese and European mariners, compasses have come a long way.

The first compasses were basically just a piece of lodestone (a naturally ocurring magnetic ore) floated (usually on a stick) in water. The stone would align itself toward North, because the Earth acts as a giant magnet with a North-South field. Free magnets align themselves along this field, and can thus be used for navigation.

The evolution of the compass (in Europe at least) was largely due to the efforts of English mariners, since England had the largest navy in the world at the time. Early compasses only had North and South marked on their faces, but in time the tally increased to 32.

Although it was discovered in the 15th century that magnetic north and 'true north' weren't always the same, it wasn't until Gowin Knight discovered a way to magnetise steel for long periods of time in 1745 that compass technology seriously progressed.

A modern shipboard compass is usually mounted in a binnacle, which will contain pieces of metal and counter-magnets to neutralise the effects of the metal in the ship (many ships are made of metal, making this essential).

These days compasses can be found in many forms, from the tiny little ones you get in Physics class, to the ones that come mounted in some Swiss Army Knives. Essentially they're the same as the one's used by 12th century mariners, and even though GPS systems and other pathfinding equipment are becoming more affordable, you'd be an idiot to wander into unknown territory without a compass.

Typical compass face layout






The principle points (clockwise from North) are North, East, South and West. This order is usually taught to children in the form of an easy to remember phrase such as "Naughty Elephants Squirt Water". Children actually learn this order through a juvenile corruption of this easy to remember phrase: "Never Ever Suck Willys". Unarguably good advice for young children, it's perhaps not the kind of thing parents want to hear.