Image: A magnetic compass lying on a nautical chart Getty Images

Compass is one of the oldest scientific inventions, containing a magnetic pointer to determine the direction on the surface of Earth. It has its own place in the history of human civilization and it was a notable discovery from mankind. The invention of compass has been one of the greatest scientific instruments. Compasses may operate on magnetic or gyroscopic principles or by determining the direction of the Sun or a star.

Ancient Chinese found that if loadstone (first natural magnet) was suspended to turn freely, it would always pointed in a same direction, that of the magnetic pole. The invention of first compass “South Pointing Spoon” credited to Han Dynasty (300-200BC) of China, made up of loadstone on polished board, when rotated freely, always point North-South. The first floating needle compass was invented in Song Dynasty (11th century), China. They used a needle and when magnetized by rubbing against loadstone, it swung around and pointed south. Similarly, Ancient Chinese people invented “South Pointing Fish”, in which loadstone chips were kept into a block of wood and decorated as a fish. As fish dipped in a water or liquid, it bobbled around to point south. Later, Dry compass invented in 1300 in Medieval Europe and liquid filled magnetic compass in 20th Century.

Generally, Compass consist of a needle, the dial, housing and other parts like lids, covers or cases to protect the compass, and a transparent base plate marked with a scale of inches or millimeters so that the compass can be used directly on maps. The needle of a magnetic compass must be made of metallic substance, which can be magnetized for the longer period of time. Steel is common substance used in needles, which is an alloy of iron and some amount of Carbon. A dial is a circular card printed with directions and housing is something that holds the other parts in a place.

The oldest and most familiar type of compass is the magnetic compass, which is used in different forms in aircraft, ships, and land vehicles and by surveyors.  Magnetic Compass doesn’t point to a geographic pole, but to the magnetic pole. The earth, itself behave as a huge magnet and interact with Compass magnet in such a way that its north end draws to align with Earth’s Magnetic Field. The deflection of a compass needle due to local magnetic influences is called deviation. The needle of magnetic compass will be parallel with Earth’s surface at the magnetic equator and the point will be increasing downward as it is moved closer to the magnetic pole i.e. any movement from horizontal plane introduces dip error.

Compasses were used for divination for centuries, and navigation today. Solid State compasses and Gyroscope, and other compasses are still used today in some of our sophisticated technology.


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