China has the longest unbroken history of progress in science and technology (over 4000 years) of any nation in the world. Four inventions that had a major impact on Western culture were paper, printing from movable type, gunpowder, and the magnetic compass. Paper-making began in China around 50 bc and by the 7th century ad had spread to Korea, Japan, and the Arab world. Wood-block printing was well established in China by 1000 ad, while movable type came about a century later. Gunpowder was first used in China early in the 12th century. It reached Europe less than a century later, where it almost overnight transformed the art of warfare. A form of magnetic compass was probably used in China as early as the 5th century bc, but it was not used for navigation until the 12th century, almost the same time as in Europe. An enormous number of other inventions have their origins in China. Examples include the stern rudder and compartmentalized hulls for ships, the horse-collar harness, paddle-wheel propulsion, and the seismograph. The Great Wall of China and the Grand Canal are outstanding Chinese civil engineering projects.