Overview
With a compass to show which way was north, navigators could keep to their course under any weather conditions.
Magnetic compasses were probably invented separately in China and Europe, around the twelfth century. People discovered that when a piece of lodestone – a naturally occurring magnetic substance – was floated on a stick in water, it tended to point north towards the bright ‘Pole Star’. This is because the Earth itself is like a giant magnet.
Early compasses were easily disturbed by movement, and were not always completely accurate. And if a ship was made of iron, compass readings could be thrown out even further.