The compass is one of the four great inventions of ancient China.
Before the compass was invented, people depended upon the position of the sun and stars to tell them the direction when at sea, which only worked when it wasn't cloudy.
As early as the Warring States Period (475-221 BC), Chinese discovered that a magnet could indicate south and north, and, on the basis of this feature, made a southward-pointing instrument that was the prototype of the compass. The instrument comprised a smooth magnetic spoon and a copper plate carved with directions; the handle of the spoon points south. In the Song Dynasty, people combined an artificially magnetized compass with an azimuth plate to create a proper compass.
In the Northern Song Dynasty (960-1127 AD), the compass was being used for navigation at sea. In the Southern Song Dynasty, its use spread to Europe via Arabia, and Arabs called it affectionately "the Eye of Sailors".
The invention of the compass had epochal influence on navigation, opening up a new chapter in the history of world navigation. Thus, Admiral Zheng He made seven voyages across seas to Southeast Asia and around Indian Ocean in the early Ming Dynasty (1368-1644 AD), Christopher Columbus discovered the New World, and Ferdinand Magellan sailed round the world.