Compass is a simple tool to judge the direction. Originally known as Sina. The main component is a magnetic needle (commonly known as a magnet) that can rotate freely on the shaft. The magnetic needle can be kept in the tangential direction of magnetic meridian under the action of geomagnetic field. The north pole of the magnetic needle points to the geographical south pole, which can be used to identify the direction. It is often used in navigation, geodesy, tourism and military affairs.

The invention of the compass is the result of China ancients' understanding of the magnetism of objects in their long-term practice. In ancient China, people came into contact with magnetite and began to understand its magnetism. People first discovered the property that magnets attract iron. Later, the directivity of magnets was discovered. After many experiments and studies, a practical compass was finally invented.

After the compass was introduced into Europe, it played an irreplaceable role in navigation discovery. But scientists know that it was not China who first answered "Why can a compass guide the way?" , but British scientist Gilbert. So, after China invented the compass theory, how did he discuss it? Did Gilbert's theory reach China in time? What influence did the "western learning spread to the east" in the late Ming and early Qing dynasties have on the development of compass theory in China? Guan Zengjian, a professor in the Department of Science History and Philosophy of Shanghai Jiaotong University, began to study these basic blank problems in 2003.

"China's earliest compass theory is the" induction theory "based on the theory of Yin-Yang and Five Elements." Guan Zengjian introduced that Shen Kuo, a great scientist in China, was still puzzled by the compass in the middle of 1 1 century. He introduced the artificial magnetization method of compass, the discovery of magnetic declination and the installation method of compass in "Talk about Meng Xi", but he didn't know why the compass was guided-"the guidance of magnet" ... was beyond reason! Subsequently, scholars put forward various compass theories based on the theory of yin-yang and five elements and people's understanding of the shape of the earth at that time. For example, Guan's Geography refers to Mongolia, which was written in the Song Dynasty at the latest, first put forward the following logic:

"Magnetic needle is made of iron, and iron belongs to gold. According to the five elements, gold is born in water and the north belongs to water, so the water in the north is the son of gold. Iron comes from magnets, which are bred by the spirit of the sun, which belongs to fire and is located in the south, so the south is equivalent to the mother of magnetic needles. In this way, the magnetic needle should not only take care of the mother, but also miss the children, naturally pointing to the north-south direction. "

Guan Zengjian said that from the perspective of modern physics, the "Montessori theory" is completely whimsical, but it is a common practice in the history of science in the East and the West to explain the behavior of things from their attributes. China's theory of Yin and Yang was very popular in ancient times. It is natural to explain the compass guidance and the principle of "always slightly eastward" with the theory of Yin and Yang. In particular, the theory holds that different end faces of magnets have different properties, which determine the direction of the magnetic needle. This statement can easily inspire people to find the two poles of a magnet, and further associate it with the relationship between the magnetic pole and the orientation of the magnetic needle, so as to find a possible way to correctly understand this problem.

The compass principle of the Southern Song people still thinks that "the compass refers to the spirit where the sun is located" only revolves around the phenomenon of magnetic declination, and the argument is based on the coordinate system that turns to geographical orientation-the ancients in China thought that the ground was flat and limited in area, so there must be a center on the ground, and the meridian passing through the center is the only north-south direction. Zeng Sanyi, a member of the Southern Song Dynasty, believed that once the geodesy is not on this north-south line, the compass points to nature "less biased". In the Ming Dynasty, it was pointed out that the correct guiding direction was determined by the earth azimuth system, and the deviation angle was determined by the celestial azimuth division system. Guan Zengjian believes that this statement "embodies the embarrassment of traditional compass theory in the face of the contradiction between yin-yang induction theory and magnetic declination".

During the Wanli period of the Ming Dynasty (A.D. 1573 ~ 1620), missionaries came to China, bringing western compass theory, earth theory and related scientific and technological knowledge. Influenced by it, China scholars began to explore the compass theory from a new angle. In this process, the functions of Yin-Yang and Five Elements are gradually weakened, and the analysis from the mechanical point of view is increasing. However, the scientific theory put forward by Gilbert in 1600 is not unified in western academic circles, let alone in the East. Among the missionaries, ferdinand verbiest, a Belgian Jesuit who came to China in 1658, has the most systematic compass theory, but he thinks that the magnetic needle points to the geographical north and south poles of the earth itself, and his theory is still limited to the scope of ancient science, unlike Gilbert who realized that the earth itself has magnets. Ferdinand ferdinand verbiest's theory has far-reaching influence in China. Until the middle of19th century, some scholars in China still used it to explain the compass problem. At this time, missionaries who came to China in the late Qing Dynasty began to introduce modern western magnetic knowledge to China.

In the pre-Qin era, our ancestors have accumulated a lot of knowledge in this field, and they often encounter magnetite, that is, magnetite (the main component is ferroferric oxide) when exploring iron ore. These findings have long been recorded. These discoveries were first recorded in several articles in Guanzi: "There are magnets on the mountain and gold and copper under it." There are similar records in other ancient books, such as Shan Hai Jing. The iron-absorbing characteristics of magnets have long been discovered. The main chapter of the nine volumes of Lu's Spring and Autumn Annals is: "Kindly absorb iron, or absorb it." At that time, people called "magnetism" "kindness". They think that magnets attract iron is the attraction of loving mothers to their children. And think: "Stone is the mother of iron, but there are two kinds of stones: kind and unkind. Kindness can attract his children, but not kindness. " It is said that after Qin Shihuang unified the six countries, Epang Palace was built near Xianyang. There is a door made of magnets in the palace. If someone wears armor and hides weapons to assassinate in the palace, they will be attracted by the magnet door. This story tells us that the ancient working people mastered the knowledge of magnetism very early.

Before the Han Dynasty, people wrote magnets as "Ci Shi", which means to love stones.

Since magnets can attract iron, can they attract other metals? Our ancestors made many attempts and found that magnets can not only attract metals such as gold, silver and copper, but also attract bricks and tiles. In the Western Han Dynasty, people realized that magnets can only attract iron (now it is known that magnets can also attract nickel) and cannot attract other objects.

When two magnets are put together and close to each other, sometimes they attract each other and sometimes they repel each other. Now people all know that magnets have two poles, one is called N pole and the other is called S pole. Like-sex repulsion, opposites attract. People didn't know this truth at that time, but they could still perceive this phenomenon.

In the Western Han Dynasty, there was an alchemist named Luan Da. He used this characteristic of magnet to make something similar to two chess pieces. By adjusting the mutual position of the polarities of the two pieces, sometimes the two pieces attract each other and sometimes repel each other. Luan Da called it "playing chess". He dedicated the novel to Emperor Wu of the Han Dynasty and gave a live demonstration. Emperor Wu of the Han Dynasty was pleasantly surprised. He was named "General Five Blessingg". Luan made great use of the properties of magnets to make novel things to deceive Emperor Wu of Han Dynasty.

The earth is also a big magnet, and its poles are close to the geographical south pole and the geographical north pole respectively. Therefore, when the magnets on the earth's surface can rotate freely, they will represent the north and south because of the nature that magnets repel each other with the same polarity and attract each other with the opposite polarity. The ancients did not understand this truth, but they knew this phenomenon very well.

The ancestor of the compass appeared in the Warring States period. It is made of natural magnets. It looks like a spoon with a round bottom, which can be balanced on a smooth "field" and can rotate freely. When it is at rest, the handle of the spoon will point to the south. The ancients called it "Sina", and in the book Han Feizi at that time, there was: "Wang Li Sina took the time first." "Sooner or later" means square, east. Guiguzi recorded the application of Sina, and Zheng people took Sina with them when picking jade to make sure they didn't get lost.

In the Spring and Autumn Period, people can grind nephrite and jadeite with hardness of 5-7 degrees into various shapes, so they can also use natural magnets with hardness of only 5.5-6.5 degrees to make SiNa. In the book Lun Heng, Wang Chong of the Eastern Han Dynasty made a clear record of the shape and usage of Sina. Sina is made of a whole natural magnet after pondering. The handle of the spoon is guided by the pole, so that the center of gravity of the whole spoon falls right in the middle of the bottom of the spoon. The spoon is placed in a smooth field, surrounded by a four-dimensional stem and branches, which synthesize 24 directions. This design was completed through long-term research after the ancients carefully observed many phenomena related to magnetism in nature and accumulated a lot of knowledge and experience. The appearance of Sina is the practical application of people's understanding of the polarity of magnet fingers. However, Sina also has many defects. Natural magnets are hard to find, and they are easy to lose their magnetism when they are impacted and heated during processing. Therefore, Sina's magnetism is relatively weak, and the contact with the site should be very smooth, otherwise it will be difficult to rotate because of the great friction resistance, and the expected guiding effect will not be achieved. Moreover, Sina has a certain volume and weight, which is inconvenient to carry, which may be the main reason why Sina has not been widely used for a long time.

Sina consists of a bronze disc and a magnetic spoon made of a natural magnet. The bronze disc is engraved with 24 directions, and the magnetic spoon is placed on the central circular surface of the disc. When it is at rest, the tail of the spoon points to the south.

The compass is made of magnets. Magnets can attract iron and are often called "magnets". In ancient times, it was called "Ci Shi" because it attracted iron as soon as it touched it, just as a kind mother attracted her children. Later, people called it a "magnet".

The magnetic poles at both ends of each magnet are different, one is called S pole and the other is called N pole. The earth where we live is also a huge natural magnet, with different magnetic poles in the north and south. The South Pole near the Earth's North Pole and the North Pole near the Earth's South Pole. It is precisely because the geomagnetic poles do not completely coincide with the geographical level that the geomagnetic declination phenomenon appears. As we know, like magnetic poles repel and opposite magnetic poles attract, so no matter where on the earth's surface, take a magnetic needle that can rotate freely, and its N pole will always point to the north and its S pole will always point to the south.

Compass is made by using the characteristics of magnets. So, which country in the world first discovered magnets and their characteristics?

More than two thousand years ago, during the Spring and Autumn Period and the Warring States Period, China had already made farm tools out of iron. When working people are looking for iron ore, they find a magnet and know that it can absorb iron.

There is such a record in China's ancient book "Guanzi": "There are mercy stones on the top and copper and gold on the bottom." "Copper gold" is an iron ore. The book "Tube" was produced in the third century BC, which shows that China knew that magnets can attract iron at the latest in the third century BC.

In the Qin Dynasty, there was an interesting legend. After Qin Shihuang unified China, he built a large Epang Palace in Xianyang, Shaanxi. There is a magnet door in Epang Palace, which is made entirely of magnets. If someone wants to stab with iron, as long as they pass by, the magnet door will attract this person.

In addition, according to ancient records, when Emperor Wu was in power, there was a Lu 'an University in Jiaodong, which was dedicated to Emperor Wu as a chess game. As soon as these pieces are put on the chessboard, they will collide with each other and fight automatically. Emperor Wu of Han Dynasty was very surprised. Originally, the big chess pieces were made of magnets, so they were magnetic and could attract each other, but Emperor Wu of the Han Dynasty did not understand this truth.

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. Float on the water surface after magnetization, which can refer to north and south. It was used as a game at that time. Cui Bao of the Eastern Jin Dynasty once mentioned this kind of "guiding blind fish" in Notes on Ancient and Modern Times.

Ceng Gongliang in the Northern Song Dynasty recorded the method of making and using the fish guide in the General Introduction to the Five Classics: "Cut it with thin iron leaves, two inches long and five points wide, with the head and tail as sharp as a fish's tip, and burn it with charcoal. Hou Tongchi, with iron wok and iron pot fish as the initial fire, the tail is straight, dipped in the basin and sealed. When in use, put the water bowl flat in a windless place, and the fish will float on the water. Its first direction is always noon. " 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. The molecules inside the hot iron sheet are in a relatively active state, which makes the iron molecules arrange along the direction of the earth's magnetic field to achieve the purpose of magnetization. This arrangement can be quickly fixed by immersing it in water, and the degree of magnetization can be increased by tilting the fish tail slightly downward. The invention of artificial magnetization has played a great role in the application and development of compass. This is also a great 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 Meng Qian Bi Tan: "Fang Jia can be guided by a magnet." According to Shen Kuo, technicians at that time rubbed sewing needles with magnets to make them magnetic. From now on, this is a method to make the arrangement of magnetic domains in the steel needle tend to a certain direction by using the magnetic field of natural magnets, thus making the steel needle appear magnetic. 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.

Meng Qian Bi Tan is a book about ancient science and technology in China written by Shen Kuo (1031-1095), which talks about some problems of magnetism and compass. In "A Supplementary Talk with Meng Xi Bitan", he talked about various phenomena in the process of friction magnetization: "It is always sharp to use a magnet to confront each other, which means that the north is not afraid of stones ... On the contrary, there should be differences between the north and the south, which has not been thoroughly studied." That is to say, after rubbing the sewing needle with a magnet, it sometimes points to the north in a tit-for-tat manner. From now on, all magnets have two poles, N and S, and the direction of the sewing needle is different when magnetized, so the direction after magnetization is also different. But Shen Kuo didn't know this truth. He truly recorded this phenomenon and frankly admitted that he didn't think deeply. I hope future generations can explore further.

Regarding the installation method of the magnetic needle, Shen Kuo introduced four methods:

1. Shui Piao —— Put some wicks on the magnetic needle to make it float on the water, and you can indicate the direction.

2. Bowl lip rotation method-put the magnetic needle on the edge of the bowl mouth, 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. Twilight hanging method-coat 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 water flotation is that the water surface is easy to shake, which affects the measurement results. Bowl lip rotation and nail rotation are flexible because of low friction, but they are easy to fall off. Shen Kuo emphasized the hanging method, which he thought was an ideal and practical method. In fact, the four methods pointed out by Shen Kuo have summarized the two systems of compass devices so far-water needle and dry needle.

In the Southern Song Dynasty, Chen introduced another method of making fish and turtle guides in Guang Ji. This fingerless fish is different from that recorded in the General Theory of Wu Jing. Carve the finger-sized wood into the shape of a 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 fish's mouth and it becomes a fingerless fish. Floating it on the water, a fish head guide, is also a kind of water needle.

The guide turtle was a popular new device at that time. Place a natural magnet in the abdomen of the wooden turtle, dig a smooth hole under the abdomen of the wooden turtle, align it, and put it on a sharp bamboo nail, which stands upright on the board, so that the wooden turtle is placed on a fixed fulcrum that can rotate freely. Because the friction at the fulcrum is very small, the wooden turtle can rotate the guide rail freely. It was not used for navigation, but for illusion. But this is the predecessor of the drought compass that appeared later.

The guide turtle was invented no later than 1325. The wooden block is carved into the shape of a turtle, and a magnet is embedded in the center of the turtle's abdomen. The wooden turtle was placed on a column with a pointed tip, pointing to the north and south respectively when it was at rest.

In order to determine the direction, in addition to the compass, it is also necessary to have an azimuth disk to cooperate. When you first use a compass, you may not have a fixed azimuth dial. With the need of azimuth measurement, a compass with integrated magnetic needle and azimuth disk appeared. Compasses include feng shui compass, water compass and drought compass.

The azimuth disk is still 24 directions, but the disk has evolved from a square to a circle. In this way, the orientation can be determined only by looking at the position of the magnetic needle on the orientation board. In the Southern Song Dynasty, Zeng Sanyi recorded the literature in this regard in the Record of Yin Hua: "The snail either has a meridian needle or sews a needle between the meridian needles." This is the earliest document about the compass. The "ground snail" mentioned in the literature is the ground snail, that is, the compass. The knowledge of magnetic declination has been applied to the compass in the literature. This compass has not only the meridian needle (the magnetic needle that determines the direction of the north and south poles of the geomagnetic field), but also the meridian needle (the geographical direction of the north and south poles determined by the sun shadow). The angle between these two directions is the magnetic declination.

Twenty-four directions are carved around the disc, which is filled with water. The magnetic needle passed through the rush and floated on the water.

It is now known that the two magnetic poles of the earth are only close to the geographical North Pole and South Pole and do not coincide. The magnetic needle points to the magnetic pole of the earth rather than the geographical north and south poles, so the magnetic needle points slightly away from the direction of due south rather than due north. This angle is called magnetic declination. Because the earth is almost spherical, the magnetic needle will tilt downward when it points to the magnetic pole, and there is an angle with the horizontal direction, which is called the magnetic inclination angle. The magnetic declination and inclination are different at different positions. Wu Yao in the Northern Song Dynasty paid attention to the application of magnetic inclination when discussing how to make a compass by geomagnetic method. Shen Kuo talked about an incomplete compass in Meng Qian Bi Tan, which is often slightly to the east. The existence of magnetic declination is pointed out. The discovery of magnetic declination and magnetic inclination makes the compass point more accurately.

Once the compass was invented, it was quickly applied to military affairs, production, daily life, topographic survey and other aspects, especially navigation. The application of compass in navigation has a gradual development process. Zhou Pingke Tan, which is a little later than Meng Qian's Bi Tan, records: "Sailors know geography, but they watch the stars at night, the sun by day and the compass in the dark." This is the earliest record of using a compass in the history of world navigation. It is pointed out that the compass is only used when the sun, the moon and the stars are invisible, which shows that the compass is not skilled at first. More than 20 years later, Xu Jing's "Illustrated Classic of Xuanhefeng Li Zhigao" has a similar record: "Just look at the stars. If it is gloomy, pat the north and south with a floating needle." In the Yuan Dynasty, the compass became the most important tool for maritime navigation. Whether it is sunny or cloudy, I use a compass to navigate. Moreover, the connection diagram of compass needle position in different navigation places using compass navigation is compiled, which is called "needle road". When the ship travels to a certain place, the direction of needle position and the route along the way are clearly marked as the basis of navigation.

The invention of compass is the result of ancient ancestors' observation and research on magnetic phenomena. In the process of observing and studying magnetic phenomena, ancient ancestors further understood the properties of magnetism and tried to apply these properties more. Legend has it that when Qin Shihuang built Epang Palace, one of the palace doors was made of magnets. If an assassin passes by with a sword, he will be caught by the guards at once. There are many such stories. According to the biography of Malone in the Book of Jin, Malone led his troops westward into Gansu and Shaanxi, and piled up magnets on both sides of the narrow path that the enemy had to pass through. When enemy soldiers wearing real armor passed by, they were firmly absorbed and could not move. Malone's soldiers wear rhinoceros armour, and the magnets have no effect on them, so they can move freely. The enemy thought the magic weapon would retreat without a fight. It is recorded in the Foreign Matter Records of the Eastern Han Dynasty that there are some reefs and shoals around the South China Sea Islands containing magnets, which often attract ships that are "blocked by iron leaves", making it difficult to sail.

During the Wei, Jin, Southern and Northern Dynasties, our ancestors already had a lot of knowledge about the properties of magnets. Even Cao Zhi, a poet at that time, used "a magnet attracts iron, but gold is not connected" in Jiao Zhi's poems. Sentence. It can be seen that he also knows the nature of magnets. Tao Hongjing of Liang Southern and Northern Dynasties put forward the magnetic survey method in Records of Famous Doctors. He pointed out that excellent magnets are produced in the south, which are very magnetic and can attract three or four iron needles, so that several needles can be hung on the magnets end to end. Magnets with stronger magnetism can attract more than ten iron needles, and even hold one or two pounds of knives. Tao Hongjing not only pointed out the strength and weakness of magnetism, but also pointed out the measurement method. This may be the earliest magnetic measurement record in the world.

Our ancestors' research and understanding of the properties of magnets is the basis for the invention and development of compasses.

In ancient times, compasses were mainly used by geomancers to take pictures of houses and graves, and also for navigation and other things. It is the latter that has played a great role in the progress of human society, so the compass can be ranked among the four great inventions in ancient times. The ancient books in China recorded that the compass was used for navigation, which began in the Song Dynasty (119) with Mi Zhu's Zhou Ping Carving Tan. The book says: "A boatman knows geography, but he looks at the stars at night, the sun during the day and the compass at night." Since then, similar documents have emerged one after another, which shows that the compass has spread rapidly in navigation activities. This invention was later introduced to Europe through Arabia, which had a great influence on the navigation industry in Europe and even the civilization process of the whole human society.

Compass, also known as compass, is a guiding instrument invented in ancient China by using the polarity of magnetic fingers. Therefore, the introduction of Sina must start with magnets.

Magnets are often called "magnets", which attract many iron filings tightly, just like a kind mother attracts her children, so people call them "magnets".

Magnets attract iron because the magnetic poles at both ends of each magnet are different, one is called positive pole and the other is called negative pole. The earth where human beings live is also a huge natural magnet. The north pole and south pole of the earth also have different magnetic poles. The north pole of the earth is negative, and the south pole of the earth is positive. According to the principle that like magnetic poles repel and opposite magnetic poles attract, take a magnetic needle that can rotate freely. No matter where you stand on the earth, its positive pole always points to the north, and its negative pole always guides you.

During the Warring States period, people used the characteristics of magnets to make a tool to indicate the north and south-Sina. However, what Sina looked like in the Warring States period is impossible to verify. Illustration of China History Textbook-"Sina" is based on the "Sina Model of Han Dynasty" of China History Museum. This model was made by later generations according to historical records and the physical objects of Han Dynasty sites unearthed underground. The site is made of bronze, with an inner circle and an outer circle, and the central round surface is polished very smoothly to ensure the accuracy of the direction indicated by the spoon body. Eight diagrams, heavenly stems, earthly branches and twenty-eight lodges are arranged in turn on the periphery of the central circle, with a total of twenty-four directions. The small spoon in the center of the site was ground with a whole natural magnet. The anode of the magnet was ground into a long handle of Sina, and the bottom of the spoon head was hemispherical and very smooth. When using, first put the site flat, then put Sina in the middle of the site, and move the spoon handle by hand to make it rotate. When Sina stopped, the spoon handle pointed in the direction of the south. This spoon-shaped Sina was used until the eighth century.

By the Song Dynasty, the working people had mastered the technology of making artificial magnets and made guide fish. Compass fish is cut into fish-shaped thin steel plates, two inches long and five points wide. The belly of the fish is partially sunken, so that the fish can float on the water like a boat. Then put the fish and the natural magnet together. Due to the attraction of magnets, steel plates are also magnetic through magnetic induction. The compass fish made by this artificial magnetic transfer method is much more convenient than Sina. As long as there is a bowl of water, you can tell the direction by putting the compass fish on the water. After long-term improvement, people rub the steel needle on the natural magnet, and the steel needle has magnetism. This kind of artificially magnetized steel needle can be said to be a regular compass. Shen Kuo mentioned in Meng Qian's Bi Tan that he had done four experiments on the use of the compass, namely, the float method, the hanging method, the nail method and the bowl and lip method. "Floating" is to put the compass in a bowl filled with water and let it float on the water to indicate the direction. The "hanging thread method" is to coat some wax in the middle of the magnetic needle, stick a silk thread on it, hang the silk thread on the wooden frame, and put a disk marked with orientation under the needle. When the pointer is stationary, the steel needle will indicate north and south. "Nailing method" is to put the steel needle on the surface of the nail and turn it gently. Because nails are smooth, magnetic needles can also play a guiding role like Sina. The "bowl lip method" is to put the magnetic needle on the smooth edge of the bowl and rotate the magnetic object, which will play the same guiding role as the nailing method. After careful observation and experiment, Shen Kuo also found that the direction indicated by the magnetic needle is not due south and north, but slightly northwest and southeast. This discovery is scientifically called magnetic declination. Moreover, the compass can give others a good sense of direction.