A compass has a small-magnetized pointer or needle, which is hung, pivoted or floated in order to allow it to move freely. The needle always points to the north as the earth's magnetism always attracts it.
No one really knows when exactly the compass was invented. It is generally believed that the Chinese were the first to use it. Simple compasses using lodestone, a magnetic rock, may have been in use china in the 5th century BC. Certain historians say that the compass has been referred to in a Chinese book dating to the 11th century AD.
The Arab merchant learnt the use of the compass from the Chinese. They in turn introduced this instrument to the European sailors. It is a well-known fact that the compass was in common use in the European countries by the 12th century.
During those days the compass consisted of a loadstone attached to a wooden crossbar which was allowed to float in a bowl of water. The lodestone always pointed north. They also discovered that a steel or iron needle kept in contact with a lodestone long enough gained magnetic properties. These needles thus replaced the lodestone.
There was however one problem with these compasses. Today we know that the earth's magnetic north and the true north are not the same. In those days the sailors were not aware of this and so often got confused. In modern days this problem is solved by using gyrocompasses. These are non-metallic and give the true north bearings with the help of a gyroscope. Once a gyroscope is spinning it is very difficult to change its direction.
