The compass appeared in China during the Warring States Period. The original compass was made of natural magnets. It looked like a spoon with a round bottom. It can rotate freely on the smooth "field", and when it is stationary, the handle of the spoon will point to the south. Zhan called it "Sina". Wang Chong of the Eastern Han Dynasty said in "On Shi Heng's English Articles": "The shovel of Sina, throw it. There are 8,000 branches (A, B, C, D, G, Xin, Ren and Gui) and 12 branches (Zi, Ugly, Yin, Mao, Chen, Ji, Wu, Wei, Shen, Xu and Hai) around the site, plus four dimensions (Gan, Kun, Dung and Min). " "Seize the day" means to take it as soon as possible. "Guiguzi seeks articles" also records that "Zheng people will take Sina when they take jade, so that it will not be chaotic. "That is to say, when Zheng's people go to the distant place to collect jade, they will take Sina with them to avoid getting lost.
In ancient times, Sina was made of natural magnets that cut jade by hand. During the Shang and Zhou Dynasties, jade cutting workers in China were very skilled. At the latest in the Spring and Autumn Period, they have been able to cut nephrite and jadeite with hardness of five to seven into jade articles of various shapes, so they can also use natural magnets with hardness of only five to six to make Sina.
Because it is not easy to find out the exact polar orientation of natural magnets in the process of cutting SiNa, it is also easy to lose magnetism due to earthquakes, and the yield is low. At the same time, the Sina cut in this way is not widely used because of its weak magnetism and large rotating friction resistance when it comes into contact with the site, and the effect is not very good.
With the continuous development of social productive forces, the continuous progress of science and technology, and the continuous expansion and development of navigation, it is not only necessary but also possible to manufacture a better director than Sina. After long-term production practice and repeated experiments by working people, people finally found the method of artificial magnetization, thus producing a higher level of magnetic direction indicator.
In the early years of the Northern Song Dynasty, Ceng Gongliang's military work "General Theory of Wu Jing" and the famous scientist Shen Kuo's "On Meng Xi" introduced the compass and the guide fish respectively. Guide fish is cut into fish shape with thin iron leaves, and then magnetized by magnetic field (detailed later). When marching, use a bowl, put it in a windless place and then put it in a windless place. However, the magnet obtained by geomagnetic field magnetization method is weak in magnetism and has little practical value. Another pointing tool is a compass, which is made by rubbing a steel needle with a natural magnet. The steel needle is magnetized after being rubbed by a magnet, and can also be used as a guide. According to his own experience, Shen Kuo said in Volume XXIV of Meng Qian's Bi Tan: "Only by grinding the tit-for-tat with a magnet can we guide it." Until19th century, modern electromagnets. Almost all compasses are made by this artificial magnetization method. At this time, the compass has crossed two stages in the history of development-Sina and Peak, and developed into a simpler and more practical pointing instrument. All kinds of magnetic pointing instruments in the future are based on this kind of magnetic needle, but the shape and installation method of the magnetic needle have changed.
Compass-History of Invention
compass
In ancient times, people often cut thin iron leaves into the shape of fish, and the belly of the fish was slightly concave, like a boat. After magnetization, it floats on the water surface, so it can refer to north and south. It was used as a game at that time. In Wu Yao, the Northern Song Dynasty recorded the method of making and using the fish guide: "Cut the fish with thin iron leaves, two inches long and five points wide, with the head and tail like the tip of a fish, and burn it with charcoal. Collect in dense containers. When you use it, put the water bowl flat in a windless place and let the fish float on the water. Its head is always in the afternoon. " This is an artificial magnetization method, which uses the earth's magnetic field to magnetize the iron sheet. That is, put the red-hot iron sheet in the meridian direction. After the iron sheet burns red, the temperature is higher than Curie point, and the magnetic domain in the iron sheet collapses and becomes paramagnetic. After quenching in water, magnetic domains are formed again. So it can refer to north and south. Because the geomagnetic field in the Yangtze River and Yellow River basins in China has an inclination of about 50 degrees, if it is placed horizontally, only the horizontal component will play a role, while if it is placed in water at a certain angle, the effective magnetic field intensity of fish magnetization will increase and the magnetization effect will be better. The invention of artificial magnetization method has played a great role in the application and development of compass, and it is also an important event in the history of the development of magnetism and geomagnetism. Shen Kuo in the Northern Song Dynasty mentioned another method of artificial magnetization in "Talk about Meng Xi": "The Fang family can guide by rubbing the needle with a magnet." According to Shen Kuo, technicians at that time rubbed the sewing needle with a magnet, and the needle was magnetized. From the current point of view, this is the use of the magnetic field of natural magnets. The method of making the arrangement of magnetic domains in the steel needle tend to a certain direction makes the steel needle show magnetism. This method is simpler than geomagnetic method, and the magnetization effect is better than geomagnetic method. The invention of friction method is not only the earliest in the world, but also creates conditions for the emergence of practical magnetic direction finder. Shen Kuo introduced four methods of installing magnetic needles:
1. water float-float several wicks on the magnetic needle to indicate the direction.
2. Bowl lip rotation method-put the magnetic needle on the edge of the bowl, and the magnetic needle can rotate to indicate the direction.
3. nail rotation method-put the magnetic needle on the nail. Because the nail surface is smooth, the magnetic needle can rotate freely to indicate the direction.
4. Thread-hanging method-paint some wax in the middle of the magnetic needle, stick a silk on it, and hang it in a windless place to indicate the direction. Shen Kuo also compared four methods. He pointed out that the biggest disadvantage of Shui Piao method is that the water surface is easy to shake, which affects the measurement results. Bowl lip rotation method and nail rotation method are flexible because of low friction, but they are easy to fall off. Shen Kuo pays more attention to the hanging line method, he thinks.
In the Southern Song Dynasty, Chen introduced another method of making fish guide and turtle guide in The Stone Forest. This kind of guide fish is different from that recorded in Wu Yao. It is carved from wood into a finger-sized fish. Put a natural magnet in the belly of the wooden fish, and the S pole of the magnet points to the head of the fish. After sealing with wax, insert a needle from the mouth of the fish to become a guide fish. It floats on the water. Put a natural magnet in the belly of the woodcut turtle, dig a smooth hole under the belly of the woodcut turtle, aim at it and put it on the pointed bamboo nail standing on the board, so that the woodcut turtle is placed on a fixed and freely rotatable fulcrum. Because of the small friction at the fulcrum, the woodcut turtle can rotate the guide rail freely. At that time, it was not used for navigation and guidance, but for illusion. But this is the predecessor of the later dry compass. The guide turtle was not invented.
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