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history meme / three inventions / the compass 

A compass is a navigational instrument that shows directions in a frame of reference that is stationary relative to the surface of the earth. The compass was invented in China, during the Han Dynasty between the 2nd century BC and 1st century AD. The first compasses were made of lodestone, a naturally magnetized ore of iron. Ancient Chinese people found that if a lodestone was suspended so it could turn freely, it would always point in the same direction, toward the magnetic poles. Early compasses were used for geomancy “in the search for gems and the selection of sites for houses,” but were later adapted for navigation during the Song Dynasty in the 11th century. Later compasses were made of iron needles, magnetized by striking them with a lodestone. The dry compass was invented in medieval Europe around 1300. [+more]