Guide to the North

The story of the compas

Why is the compass so important?

The magnetic compass was an important advance in navigation because it allowed mariners to determine their direction even if clouds obscured their usual astronomical cues such as the North Star. It uses a magnetic needle that can turn freely so that it always points to the north pole of the Earth's magnetic field. Knowing where north is allows the other directions to be determined as well. The compass was invented by the Chinese, and was widely used for navigation beginning in about the thirteenth century.

Backround

The phenomenon of magnetism was known to the ancient Greeks, but the magnetic compass was invented by the Chinese. The thirteenth century explorer Marco Polo (1254-1324) is said to have brought a compass with him when he returned to Venice after his twenty years of service in the court of Kublai Khan (1215-1294). He may indeed have carried home such a souvenir. However, the knowledge that a piece of the naturally magnetic iron ore magnetite (Fe3O4), called a lodestone, would align itself from north to south if allowed to move freely, seems to have arisen at least a century before Marco Polo in Europe and the Arab world.

History of the compass

A compass is a magnetometer used for navigation and orientation that shows direction in regards to the geographic cardinal points. For the structure of the compass, it will show the diagram called compass rose in showing the 4 main directions: East (E), South (S), West (W) and North (N). The angle increases in the clockwise position. North corresponds to 0°, so east is 90°, south is 180° and west is 270°. The compass was invented more than 2000 years ago. The first compasses were made of lodestone, a naturally magnetized stone of iron, in Han dynasty China (202 BC – 220 AD). It was originally called the "South Pointing Fish" The compass was later used for navigation during the Chinese Song Dynasty (960–1279 AD), as described by Shen Kuo. Later compasses were made of iron needles, magnetized by striking them with a lodestone. Magnetized needles and compasses were first described in medieval Europe by the English theologian Alexander Neckam (1157–1217 AD). The first usage of a compass in Western Europe and the Islamic world was recorded in around 1190. Dry compasses begin appearing around 1300 in Medieval Europe and the Medieval Islamic world. This was replaced in the early 20th century by the liquid-filled magnetic compass.

Guide me home

Before the introduction of the compass, geographical position and direction at sea were primarily determined by the sighting of landmarks, supplemented with the observation of the position of celestial bodies. Other techniques included sampling mud from the seafloor (China), analyzing the flight path of birds, and observing wind, sea debris, and sea state (Polynesia and elsewhere). Objects that have been understood as having been used for navigation by measuring the angles between celestial objects, were discovered in the Indus Valley site of Lothal. The Norse are believed to have used a type of sun compass to locate true north. On cloudy days, the Vikings may have used cordierite or some other birefringent crystal to determine the sun's direction and elevation from the polarization of daylight; their astronomical knowledge was sufficient to let them use this information to determine their proper heading. The invention of the compass made it possible to determine a heading when the sky was overcast or foggy, and when landmarks were not in sight. This enabled mariners to navigate safely far from land, increasing sea trade, and contributing to the Age of Discovery.