Before the invention of the compass, direction at sea was determined mainly by the position of the stars in the sky. For thousands of years sailors have found their way by looking at the positions of the sun and stars. To find their way at sea, sailors in the Northern Hemisphere used Polaris or the North Star to first determine the north direction.
The methods had some limitations. If the sky was not clear at night, the planets and stars would be of no use. This situation changed after the invention of the magnetic compass. However, magnetic lodestones appear before magnetic compasses.
Naturally occurring magnetic iron ore, also called lodestone, is believed to have been first discovered in what is now China. This material can arrange itself along a north-south axis if there is no obstacle of gravity or friction.
The Chinese were fascinated with its mysticism, Lodestone was then considered a magical stone. Astrologers used to predict changes in fortune by interpreting the pattern of signals and lines revealed by the ‘Lodestone’. He used to choose the auspicious moment, determine the season of cultivation, also find the treasure of precious jewels. Besides, they used it to make appropriate designs for buildings like houses, temples or burial grounds.
It is difficult to pinpoint the inventor of the magnetic compass. More than 2,000 years ago, records of the use of “directional instruments” made of simple magnets were found in Han Dynasty China. Sen Kuo first clearly described a magnetic needle in 1088, and Xu Yu in his “Pingzhou Table Talks” mentions the use of a magnetic compass in maritime navigation between 1111–1117. The English word ‘compass’ evolved from Middle English, Latin and other words denoting circles, mathematical instruments, routes, or journeys.
During the Tang Dynasty (seventh century), Chinese scholars devised a way to turn magnets into iron indicators by rubbing them with ‘magnetite’. They also found that a red hot needle becomes magnetized when it is cooled by placing it along a north-south direction.
By the 11th century, the Chinese military was using both wet and dry compasses for navigation and navigation. The so-called “south-pointing fish” was a wooden fish with a magnetized iron needle inside, the needle floated in the water of the pot. Later, a dry compass is formed in the shape of a turtle. Loadstones were embedded in its carved wooden body and balanced on bamboo needles, allowing it to rotate freely.
Navigation compasses made during China’s Song Dynasty (960-1279) had a unique design. The ‘loadstone’ was shaped into what might be called a spoon or sleeve. This spoon-shaped loadstone was placed in the middle of a bronze plate, and could be rotated by magnetism. When the rotation stopped, the handle of the spoon was pointing south and the mouth of the spoon was pointing north. These compasses were known as ‘South Pointers’ or ‘South Governors’. The bronze plaques were engraved with the four cardinal points, the directions of the various constellations, and other important symbols and information.
The magnetic compass has a much longer history. But first let’s know what is a magnetic compass?
What Is A Magnetic Compass?
A magnetic compass is a primary instrument used in navigation, especially as a direction finder on ships. The most common type of compass is the magnetic compass. It is capable of indicating the “magnetic north” direction of the Earth.
At its center is a needle made of magnets, which aligns itself with respect to the horizontal axis of the Earth’s magnetic field. A magnetic compass works because the Earth itself acts as a giant magnet. A magnet needle always aligns itself with this north-south axis because of its north-south magnetic field.
The technology has been used for centuries. The principle behind this simple technology has stood the test of time and is still needed in many areas despite the proliferation of modern satellite-based navigation.
A guide to navigation and commerce for nearly a thousand years, the magnetic compass operates on a simple principle. Today it is possible to navigate or reach a port anywhere in the world using modern navigation charts. Safe travel is possible by making, using and maintaining an accurate compass using some basic principles including the magnetic field.
However, despite the development of the magnetic compass as a universal navigation instrument, it is quite complicated to use in modern times, especially on metal vessels.
Magnetic Compass In Europe
By the 1300s, magnetic compasses began to appear in Europe and the Middle East. Most historians believe that the Chinese introduced their compass to the Muslims, who then shared this knowledge with the Europeans.
The arrival of the compass in Europe made their voyages possible throughout the year. As before, they no longer had to sit around for the summer months with good weather. Thus the compass quickly became an important navigational tool in Europe. It helped them a lot in discovering new countries and exploring trade routes.
The Magnetic Compass In The Age Of Discovery
After the advent of the compass, European sailors became more able to sail from sea to sea without ever seeing land. The ‘Age of Discovery’ was made possible by the compass.
From about the fifteenth to the eighteenth century European exploration of the world took on a new dimension.
Meanwhile, sailors and traders marked sea routes to China, Japan and the islands of Indonesia. Silk, tea and spice trade was established. It was during this time that the Spaniards encountered the Aztec and Inca civilizations of Central and South America, and explorers discovered the amazing natural resources of North America. The expansion of travel and trade routes was made possible by the compass. As a result, Europeans colonized the Americas.
In the 16th century, English scientist William Gilbert discovered that the earth itself is a magnet. Which explains why the compass always points north-south.
Geology And Physics In The Formation Of The Magnetic Compass
As mankind dreams of setting foot on the Moon and other planets, the question that naturally comes to mind is: “Will a magnetic compass work on the Moon?”
Cosmic objects have some similarities, such as gravity, but also some major differences, such as size and composition. Earth’s magnetic field has nothing to do with the size or shape of the Earth, but rather is a special effect of our planet’s outer liquid core.
As the planet rotates, the slowly flowing melts contain a lot of iron. It generates electricity and creates a magnetic field.
But molten iron isn’t the only cause of Earth’s magnetic field. The crust, ionosphere and magnetosphere can also affect it.
The ionosphere is the ionized part of the Earth’s upper atmosphere, which is about 48 km above sea level. Mr. 965 km from Mr. located at altitude. It consists of thermosphere, mesosphere and parts of exosphere. The ionosphere is ionized by solar radiation. The ionosphere plays an important role in generating the atmospheric electric field and forming the inner boundary of the magnetosphere.
And the magnetosphere is the region of space surrounding the Earth where the influence of the Earth’s own magnetic field is greater than the magnetic field of interplanetary space. The magnetosphere is formed as a result of the interaction of the Earth’s magnetic field with the solar wind.
Development Of The Magnetic Compass
Many technical improvements have been made to the magnetic compass over the centuries. Many of these developments were led by the British, as their vast empire depended on naval power. So their dependence on navigational machinery was very high.
By the 13th century, the magnetic needle of a compass was mounted on a pin in the bottom of the compass bowl. At first only north and south were marked on the bowl, later the other 30 cardinal points were added. These dots were drawn on a card and placed just below the needle. As a result, sailors could see the direction from the card.
The bowl itself is then hung on a ‘gimbal’ (the gimbal is basically the ring on the side of the bowl that allows the bowl to swing freely). This would have the card in parallel. In the seventeenth century the magnetic needle took the ‘parallelogram’ shape, which was easier to place than the thin needle.
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In the fifteenth century, sailors began to realize that the compass needle did not point directly to the geographic North Pole, but to a point close to it.
In Europe, the compass needle pointed slightly east of true north. To solve this problem, British sailors developed a special type of meridional compass. A special type of compass, which calculates the difference between magnetic north and geographic north.
The direction of north marked on this compass card and the direction the needle pointed would be the same direction as the “magnetic north” when passing a certain point in Cornwall, England. (However, the magnetic poles move in a certain pattern—in recent centuries, Europeans have seen magnetic north move largely west of true north. It’s important to keep this in mind when navigating directions.)
‘Variation’ And ‘Deviation’ Of Compass
In the fifteenth century, travelers realized that the ‘north’ direction shown on the compass was not the same as the geographic north of the Earth. This difference between the magnetic north of the compass and the earth’s north is called ‘variation’.
The variation varies depending on location. Closer to the equator the difference is less noticeable. However, the difference increases as you get closer to the North and South Poles. Even then the difference between the position shown on the compass and the original position can be up to several kilometers. Because of this, sailors in these regions must always adjust their compasses to these changes.
Over time, the magnetic compass has undergone a number of changes, particularly in the area of nautical guidance. As ships made of wood replaced ships made of iron and steel, the ship’s magnetism began to affect compass readings. This is called ‘deviation’.
Placing a soft iron ball (called a Kelvin sphere) and a bar magnet (called a Flinders bar) near the compass increases the accuracy of compass readings. Moreover, there is iron in the aircraft, which is why this ‘deviation’ has to be taken into account in using the compass in the aircraft.
Gwynne Knight’s Important Contribution
In 1744, English inventor Gwynne Knight demonstrated before the ‘Royal Society of London’ that compass needles were not as magnetized as before, and accuracy was decreasing.
He proved that it was possible to make great improvements in the magnetization of steel. He then proposed a new shape of magnet needle, which would have a rhombus (diamond shape) shape. Besides, he also suggested better way to hang the needle.
Shortly thereafter, Gowin Knight discovered a method of magnetizing steel. In this manner the steel can retain its magnetism for a much longer period of time. He gave the compass needle a rod shape and made it large enough to add a cap to place the needle on the pivot (where the needle rests).
The Royal Navy (British Navy), after some experimentation, adopted Knight’s new compass as their standard and continued to use it for nearly a century.
Transition From ‘Dry-Card’ To ‘Liquid’ Compass
Some early compasses did not contain water in their bowls, they were known as ‘dry-card’ compasses. Its readings were easily disturbed by jolts or vibrations. On the other hand, water-filled compasses, although less affected by shaking, were more difficult to repair if their water dried up and the pivot (where the needle rested) corroded.
The first ‘liquid’ compass was made in 1862 by adding a floating device to a compass card. This takes most of the weight off the needle. A system of bellows (a type of air pump) was also invented to prevent fluid from leaking during expansion and contraction. Due to these improvements, the liquid compass replaced the dry card compass at the end of the 19th century.
Modern Compass
A modern mariner’s compass is usually placed in a cylindrical recess called a ‘binnacle’, from under which the surface of the compass is illuminated. Each ‘binacle’ is made of specially placed magnets and pieces of steel, which neutralize the magnetic effects of the ship’s metal.
A similar device is used in aircraft, but has the added feature of correcting errors in the magnetic compass caused by sudden changes in direction of the aircraft. Its name is gyromagnetic compass.
Gyrocompass
A gyrocompass is a non-magnetic compass that can automatically determine geographic direction based on a fast-rotating disk and the Earth’s rotation. The gyroscope is mounted on a set of 3 concentric rings, which are connected to each other by ‘gimbals’ and each ring can rotate freely.
In 1885 Marinus Gerardus van den Bos patented the first gyrocompass. The compass, however, was not so useful back then. In 1906, Hermann Anschutz-Kempfi invented the practical gyrocompass in Germany. After successful trials in 1908, it began to be widely used in the German Imperial Navy.
The gyrocompass was a very important invention in marine navigation. Regardless of the course of the ship, the weather or how much steel was used in the construction of the ship, it is always possible to determine the exact position of a ship through this device.
If it ‘presses’ (ie starts swinging), the weight of the pendulum pulls it back into a straight line. The gyrocompass is commonly used in navigation systems, as it can be set to true north rather than magnetic north.
