Try this at home: Fill a pie pan with an inch of water and float a small piece of cork in it. Next, stroke a needle from the middle to the tip 15 times with a magnet. Lay the needle across the center of the cork and watch as it slowly turns to point north. Congratulations! You’ve made a compass.
The first compasses were used in China as early as 200 B.C., derived from the tools of fortune-tellers who divined the future using a spoon made of a magnetic iron ore called lodestone. The handle of the spoon always pointed south. When someone realized that this feature could be used to navigate, not just predict, the magnetic compass was born. The spoon was mounted on a slab marked with the constellations and the cardinal points. The magnetized needle replaced the spoon around the eighth century.
Western Europeans, as usual trailing the Chinese in the arena of invention, adopted the magnetic compass in the 12th century. This was a great improvement over the navigational strategy of following the sun, especially in inclement weather. It’s a matter of dispute whether the technology traveled from China to Europe by sea or whether it came via the Silk Road, but its arrival changed the world. Could Columbus or Cortez have found the Americas without it?
The Europeans, to their credit, improved the device. The English, for example, mounted the needle on a pin in the 13th century. In 1907, American Elmer Sperry invented the gyroscopic compass, which remains level and therefore accurate when in motion, useful on ships and airplanes. Compasses still rule navigation, though today they sport tungsten steel needles, jeweled bearings and other modern fixtures. None of that matters, however, as long as Mother Nature doesn’t mess with the location of north.