The almighty compass: the ultimate necessity of navigation
There is no reliable information about when and how the magnetic compass was found, but everyone agrees that the ancient Chinese were the ones who, long before the New Era, according to some even 500 years before Christ, were the first to use some kind of such a compass.
To move on land, the help of the Sun and the Moon was enough for man in his orientation. When he saw where the sun was rising from, he knew where the east was, so it was easy for him to determine the other parts of the world.
At sea, it was necessary to know the sides of the world almost every hour, and not only them, but also one’s position on the Earth’s globe, i.e. know your latitude and longitude.
The magnetic compass has always represented, in fact, a thin iron needle or rod that rests on a spike for easier turning around the vertical axis. That needle is magnetized, which is the reason for its placement in the direction of the Earth’s natural magnetic field, north-south.
Previously, the magnetization of a steel needle was done using a permanent magnet, and with the invention of electric current, it will be magnetized by passing an electric (direct current) through a coil wound around it. That’s how it’s done today.
The magnetic needle is placed in a housing on the rim of which are written letters – symbols for the cardinal directions: N for North, S for South, E for East, and W for West, as well as markings for intermediate directions: Northeast (NE), Southeast (SE), Northwest (NW) and Southwest (SW), and then for another division between: North Northeast (NNE), East Northeast (ESE), East southeast (ESE) and south southeast (SSE) etc.
It is usual for such compasses to be divided into 32 equal “slices”.
Modern compasses may also have an inclinometer, an instrument that determines the angle of the Earth’s magnetic field relative to the horizontal plane, and which can be adjusted to account for various local magnetic variations.
The case of the magnetic compass is attached to e.g. ship construction. No matter how the ship deviates from its sailing direction, which is determined every hour by the ship’s captain or the first officer on duty, the compass needle remains set in the north-south direction.
The helmsman is obliged to place the ship according to the angle on the compass determined by the captain. This means that on the circumference of the compass there is a degree division from 0° to 360°, and not just markings for the sides of the world and between sides.
It should be said that the ship’s compasses must always be calibrated additionally, because due to the steel structure of the ship, the so-called compass deviations. Today it is done automatically, but it was not like that before.
There are also so-called liquid magnetic compasses. With them, the magnetic needle is located in a glass hemispherical capsule with a liquid (oil or a mixture of alcohol and water, etc.) in which it rotates freely but “damped” and always takes the north-south direction.
Since the Earth’s magnetic poles do not strictly coincide with the geographic ones, magnetic compasses are not reliable for orientation in bordering, polar regions, because the magnetic poles are more than a thousand kilometers away from the geographic ones.
In order to eliminate the mentioned shortcoming, gyroscopic compasses were made based on the principle of terns. That principle uses the feature of the spinneret that, during rapid rotation, its axis always remains in the same position (north-south), parallel to the Earth’s axis of rotation.
Gyrocompasses are not affected by the Earth’s magnetism and its anomalies. The tern is adjusted in the gyrocompass so that its axis always points north-south, and it rotates continuously with the help of a small electric motor.
In addition to it, airplanes also have a radio compass (VOR), which enables the pilot to turn in the direction from which he hears certain signals from the radio compass station. Those tones are monotonous while the plane is on course; as soon as the aircraft deviates from that direction, the signals become intermittent, which is a sign to the pilot that he has deviated from the required course and that he should correct it.
Instead of sound, a classic indicator can be used. However, today all that navigation technology is slowly becoming obsolete, and the satellite positioning system, GPS (Global Positioning System), or even more precisely WAAS (Wide Area Augmentation System), is taking hold more and more.
Today, you can sometimes see small compasses built into cars, watches, or other electronic equipment. These are the so-called “solid-state” electronic devices, which have 2 or 3 magnetic field sensors, and with the help of trigonometry, their data is processed by a single microprocessor and determines the position of the pointing hand or sends a digital signal.
But let’s go back in time and see how the seas were navigated then, where a compass was very necessary.
After the Chinese, the magnetic compass was used in the 11th century by Arab sailors sailing across the Indian Ocean towards the rich archipelagos of Indonesia.
In all likelihood, the compass reached the navigators of the Mediterranean via Arab traders or with goods and other inventions via the Silk Road directly from China. The first notes about its use in Europe can be found in the works of the English scientist Alexander Neckham (1157-1217), in the book “De naturis rerum” (“On the nature of things”) printed in Paris in 1190.
It is interesting that Chinese compass needles pointed south for centuries, so the magnetic compasses used in Europe in the 17th century, used by astronomers and surveyors, also pointed south, while those used by sailors pointed north.
Historians believe that it was only later that the Europeans modified the compass brought from China so that it points north, and the greatest merits are attributed to the Italian Flavio Gioia.
The South Magnetic Pole is located about 2,600 kilometers away from the geographic South Pole, near the French overseas Adelie Coast, in Antarctica.
Strictly speaking, since it attracts the south sides of all other magnets, it is actually the north magnetic pole.
During Earth’s turbulent geological past, the magnetic poles changed places many times; last time 780,000 years ago (Brunhes-Matujama change). So far, no one can explain how and why this happens.
However, as with other inventions, many more years will pass before its widespread use and the stronger development of seafaring thanks to it.
At the time of the great maritime discoveries in the 15th and 16th centuries, no one sailed the seas without a magnetic compass and a few magnetic needles in reserve.
Thus, when Magellan set sail from Spain on the western voyage around the world in 1519, he had no less than 35 magnetic needles on his ship, so that he could replace the one under the circular compass map if it was demagnetized by any chance and deviated from the “north direction”.
Just as the clock freed people from the need to measure time according to the position of the Sun, so the compass enabled sailors to sail “both in the sun and in the ice”, when it is cloudy, at night, and at any time of the year.
Until the 13th century, navigation in the Mediterranean, including the Adriatic and the Black Sea, as well as maritime trade between distant ports, did not take place in winter precisely because of poor orientation and the possibility of ships getting lost in fog and storms.
Regarding the navigation in the Mediterranean, there are records from that time that have stated that the most unfavorable time for navigation is from October to March, so ships that departed from the Levant and carried loads of goods from the Far from the east to Venice (carpets, silver, silk, fragrances, spices, teas, dyes, etc.) could make only “one tour” in a year.
Likewise, ships from Venice set sail for the Levant at Easter time and returned in September, before the “bad times” for sailing without a compass began. If the Venetian ships set sail for Egypt in, say, August, they would have to spend the winter there, and would not return home until May of the following year.
When the compass finally arrived in the Mediterranean in the 14th century, trade also revived, so the Venetian fleet could make two or more “tours” in one year, doubling its trading activities.
Thanks to the invention of the compass, the Mediterranean finally became navigable even during the winter.
At that time, there were completely different conditions for sailing ships in the Indian Ocean, because the seasonal monsoon winds were so regular in their formation and blowing direction that, in an emergency, sailors could align themselves with them, as a kind of natural compass.
Sailors in the North and Baltic Seas did not know about the compass for a long time. However, other circumstances were in their favor during the voyage.
Those seas are not so deep, so they were helped in their orientation by observing the sky and measuring the bottom of the sea, and it is known that the polar light, the aurora, which they thought was a mysterious guide for lost souls, was especially useful for them.
So, as far as Europe is concerned, the sailors of the Mediterranean were the first to accept the compass and thanks to it, Columbus will be able to set off into uncertainty – on the way to the west.
Legend has it that the word magnet is derived from the name of the shepherd Magnetes, who (they say) discovered the magical mineral magnetite (Fe3O4) while tending sheep around the river Meander in ancient Thessaly, on the shores of the Aegean Sea.
