History of Compassion

Compass is an instrument used for orientation that can be used on sets, on water or in space. There are two types: magnetic compasses using magnet needles and electric compasses using electric spinners. In this article, we only talk about magnetic compass .

Compass history from:

The history of the compass dates back to more than 1000 BC, when the Chinese discovered the principle and gradually developed more. Tran Trong Kim wrote in Vietnam Historian ". and Mr. Chu Cong Dan re-invented a male-only vehicle to bring Vietnam home often." ( Book 1, page 13) Western history records record the magnetic compass using magnets used by Chinese navigators about 1100 AD . British sailors, according to scholar Alexander Neckam in De Utensilibus (About Instruments) in 1190, used magnetic compasses while sailing.

(Photo: stanleylondon.com)

The Arabs began using the compass around 1220 and about 1250 the Vikings knew how to use this compass. At that time, a magnet was used, placed on a small piece of wood or on a reed and placed in a bowl of water. A piece of wood or plus sieves helps the magnet needle float on the water, eliminating friction forces. Water makes the needle less wobble when the vessel is tilted or vertical.

The magnet needle is a natural magnetic stone made of stone called lodestone (there is a place to write loadstone, also called magnetite), taken from the word lodestar, according to the seafarer, the star of the direction, pointing North Pole (Polaris or Pole star in English and Étoile polaire, French). It is also soon known that if a metal rod is to touch a magnet stone, the metal bar has the same characteristics as a magnet stone, meaning that it tends to point to a relatively fixed side. And such a magnetic transmission can fade away over time. So ships using compass from ancient times still had to carry a good magnet stone, to be able to magnetize or from the compass needle when needed. It was known about magnetization around the 11th century.

China is considered to be the first country to use compass from the maritime industry . Before the invention of the compass, sailors navigated the sun's position during the day and the star's position at night, and people often followed the seasonal trade winds. Astronomical maps have been found for the positions of the constellations. In an ancient astronomical map of China we can see the Shinto constellation (Scorpio or Scorpion) and the Taurus (Taurus or Taureau). But when it is cloudy or rainy, it is impossible to orient. Magnetic compass has helped solve the orientation in all weather conditions, including the orientation of trade winds.

Arabs learned how to use magnetic compasses while trading with China. The compass was then brought to Western Europe in the end of the 12th century, then to Northern Europe in the 13th century. Under the Ming Dynasty, Zhen He and the Ming court dynasty went 7. The trip is very far, going to the coast of Africa. Each trip, Zheng He used a team of 100 to 200 boats and the magnetic compass played an important role in these journeys.

From the end of the 15th century until the beginning of the 16th century, European navigators traveled many places, drawing new paths, discovering the Americas and making trips around the world. If there is no magnetic compass, it is difficult to carry out these tours.

Structure of the magnetic compass (Photo: VietSciences)

Compass from across the ages:

The first compass was called "the needle of the South " invented by the Chinese very early, as soon as people found magnetism and magnet stone, during the period of the war, the Nationalist state . The male needle is different from the compass today. It is shaped like a spoon cut out of a natural magnet and placed on a polished polished bronze base to reduce friction. (It was then known that copper is a metal with no effect on the magnetic field, and therefore, does not deflect the magnet needle). The round spoonful of the center of the copper base makes the center of the needle to the stretcher of the male needle around. After the spoon stood still (static balance) scooping the spoon only to the south. Chinese people view the south as the direction of the kings, so use the word "just south" and not the north. If the spoon is used on the ground, and is often used in geography, feng shui, choosing to build houses, graves .

The seafarers initially used " South Threaded Fish ", cut the fish with iron, then magnetized. When released into the water, the " Southern Fish " will float in the water and lie in the North-South axis. And people still have to magnetize " Fish " when its magnetism weakens as mentioned above. Gradually, " Fish " was replaced with an iron needle that had been rubbed on a natural magnet. When the needle has obtained the necessary magnetization, the needle will point south when lying on a small piece of wood or a reed, floating in the water. That is the first compass. The magnetized needle is then attached to a cup that has a directional note, usually four

Compass from the wind flower, clearly see the four main directions and four directions (Photo: VietSciences)

East, West, South, North directions and four directions: Southeast, Northeast, Southwest and Northwest . Later, there are eight more side directions, such as North East, West Southwest, etc. It is also gradually known about the deviation of the magnetic field, the degree of magnetism, the degree of deviation, and these variations vary with the location of each place, each region. (declination, variation of magnétique or magnetic variation).

At first the compass face (also known as Compass Rose, Compass Rose) is divided into 32 intervals , then engraved in a circle into 360 degrees. On the ground, the army of magnetic compasses was more accurate, divided into 6400 engravings. The aviation industry also uses magnetic compass. Until now, most helicopters and some small airplanes are still equipped with magnetic compasses as a directional tool.

When used in the maritime industry, the magnetic compass is used to indicate the direction. Equipped with a directional measuring instrument, people use magnetic compass to measure the contrast from two or three objects identified by the naval map (mountain peaks or snails, buoy lights, lighthouses, special structures . to determine the position of the ship, thereby calculating the distance traveled, the speed, the direction to go . and can experiment more, through the calculation, with or without groundwater, wind power .

In modern times , the compass is attached to the wind flower, there is a heart line (lubber line that corresponds to the axis of the length of the ship) placed in the compass, the upper surface has a clear glass and has a bright light. The compass of the compass contains a density of densité which is very close to the general weight of the wind flower and the magnet needle to eliminate the strength of this part on the bearing axis. The compass is hung in the gimbals system to always keep the compass surface from the plane position. The pinnacle is often mounted very firmly on the middle axis along the length of the ship. The two sides of the magnetic compass have two round metal balls and can be moved. People move these two balls on their prices to eliminate the effect on the compass magnet caused by the metals on board. Today it is possible to adjust the magnetic compass by comparing the directions measured with the magnetic compass with the direction measured by the electric compass.

Since the magnetic compass does not need an external source of energy, the magnetic compass is used as a backup device or to be used in case of emergency when the ship loses power. The magnetic compass can also be used at any time, while the electric compass needs to have a time for the electric gyroscope to start and reach a fixed rotation speed. And the most special point is that magnetic compasses can be made in all sizes, can be held in the hand, or attached to the back of the watch, both compact and light, and anyone can use it, no It takes time to guide. In addition to paper inventions and wheels, the magnetic compass is the invention used, with more or less improvements, the longest.

Three parts of the compass:

1. The needle is magnetized, in the north from the field
2. The compass face is etched and rotated on one axis, adjustable with any magnetic field (azimut magnétique)
3. The background has an arrow to indicate the direction you want to go

Thuan Ngoc & Vo Thi Dieu Hang