Magnetic Compass

Magnetic Compass Definition

Humans have always used the skies to make their way from place to place. At night, the North Star points the way northward. During the day, the rising, and setting of the sun displays the directions of east and west. These natural navigational tools allowed humans to explore and find their way back, but there is always room for improvement. That improvement came in the man made tool known as the compass.

How a Magnetic Compass Works

A magnetic compass works by using a magnetic material, which will align itself with the earth’s magnetic poles. When aligned, a magnet is oriented north and south. This allows not just discerning in what direction north lies, but finding more accurate bearings in all directions.

This can be done by measuring the angle from north. The mathematical idea of a 360-degree circle goes back 6,000 years to the ancient world. When the circle is combined with the compass needle, 0 degrees is north, 90 degrees is east, 180 degrees is south, and 270 degrees is west. Using a circle in this manner allows a person to much more accurately create and navigate with maps.

The Magnet Compass through History

Through history, we find many great technological inventions that impacted on humanity at large. But there are a few that, even if today we deemed as simple as a piece of paper, changed and shaped our past and present. One of these remarkable inventions is the magnetic compass.

Chinese Magnetic Compass

Sometime between 950 and 1000, the Chinese began to use magnetic compasses. The first Chinese compasses were constructed using the naturally magnetic mineral lodestone. Initially, their use as a navigational tool was ignored. Instead, the compass took on more mystical uses. The earliest tasks for which the Chinese used the magnet compass were fortune telling and aligning buildings according to the principles of Feng Shui.

It was not until the Song Dynasty that the magnetic compass was first used as a navigational instrument. Like many scientific advances, it was first exploited by the military for land navigation around 1040. In 1111, it was finally being used for sea navigation.

Interestingly, this breakthrough device was originally only used as a backup to the traditional methods of celestial navigation. Zhu Yu’s writing in 1111 states that the compass was used when the weather blocked out the sun or stars to the point where they could not be used in navigation.

Fig. 2 - 16th Century Compass

European Magnetic Compass

The Chinese may have used the magnetic compass first, but by the late twelfth or early thirteenth century, European sailors were also navigating by the magnetic wonder. Like their Chinese counterparts, they initially used it only when poor weather impeded the use of the sun and stars for navigation. By the end of the thirteenth century, Europeans had expanded the devices use to study astronomy.

Middle Eastern Magnetic Compass

The thirteenth century also saw the introduction of the compass to the Middle East. Descriptions of designs indicate that the compass likely spread from China. Like the Chinese, they commonly used it for spiritual reasons. The magnetic compass was used to determine the directions of Mecca, towards which Muslims must pray. Later the compass was combined with a sundial to create a device that told both proper the time and direction for prayer.

The Compass Rose

A compass is an image on a map that aids the map reader in more clearly determining a specific direction. The image usually takes the form of a star with between 8 and 32 points. The star can be used to find degrees on a map, which can be used with either celestial bodies or a compass to very accurately navigate. This became popular with Arab navigators in the late tenth century before spreading throughout the Mediterranean and then to the rest of Europe.

Fig. 3 - A Compass Rose

Challenges of the Magnetic Compass

By the fifteenth century, the age of exploration was on. Portuguese sailors like Gonzalo Cabral and Ferdinand Magellan made their ways to distant lands. Sailors were increasingly reliant on the magnetic compass as they travelled exceptionally far from the sight of land. As sailors travelled further and further north, they began to discover that magnetic north was not quite the same as true north. It was English scientist William Gilbert who demonstrated that the Earth itself was a magnet, finally explaining the manner in which a magnetic compass operated.

Fig. 4 - Edmund Halley

Edmund Halley

The country most interested in the development of the magnetic compass was Britain. The British invested in determining the variation of magnetic north as sailors travelled. Taking on the task was scientist Edmund Halley in 1698. Halley embarked upon many journeys through the Atlantic Ocean, measuring the distance between true and magnetic north. This information was published in a map by the Royal Navy in 1701.