A needle magnet, usually a narrow diamond.It is supported in the middle and can rotate freely in the horizontal direction. Under the effect of geomagnetism, the two tips point to the south and north respectively when it is stationary.Compass and compass are applications of magnetic needle.
Chinese name
magnetic needle
Alias
compass
Appearance
It is usually a long and narrow diamond, and is supported in the middle
Before the invention of the compass, human navigation in the vast sea, often lost its way, causing unimaginable consequences. It was the Chinese who invented the compass that gave human navigation a direction.One of the four great inventions in ancient China.The main component is a magnetic needle mounted on a shaft that can rotate freely.Magnetic needlegeomagnetic fieldIt can be kept atMagnetic meridianIn the tangent direction of.The north pole of the magnetic needle points to the geographical north pole (the south pole of the geomagnetic field), which can be used to identify directions.It is often used in navigation, geodesy, travel and military affairs.
The invention of the compass is the result of our working people's understanding of the magnetism of objects in long-term practice.Because of production labor, people came into contact with magnetite and began to understand the magnetic properties.People first discovered the nature of magnetite.Later, the directivity of magnetite was discovered.After many experiments and researches, a practical compass was finally invented.
Guide Fish
In ancient times, thin iron leaves were often cut into the shape of a fish. The belly of the fish was slightly concave, like a small boat. When it was magnetized and floated on the water, it could mean north and south.At that time, it was used as a game.Cui Bao of the Eastern Jin Dynasty once mentioned this "guide fish" in his "Ancient and Modern Notes".
In the Northern Song Dynasty, Zeng Gongliang wrote the method of making and using the guide fish in the General Introduction to the Martial Arts: "Cut it with thin iron leaves, two inches long and five cents wide, with the head and tail sharp as fish, burn it in a charcoal fire, Hou Tongchi, seal the head of the fish with an iron seal, align the tail with the child position, dip it in a water basin, stop if there is no tail cent, and close it with a secret device.When using, place the water bowl flat in a windless place, and let the fish float on the water surface. The head of the fish often faces noon. "This is an artificial magnetization method, which uses the earth's magnetic field to magnetize the iron sheet.That is, place the red hot iron sheet in the direction of the meridian.The molecules inside the red hot iron sheet are in a relatively active state, so that the iron molecules are arranged along the direction of the earth's magnetic field to achieve the purpose of magnetization.Dip into the water to fix this arrangement quickly, while the downward inclination of the fish tail can increase the magnetization.
Artificial magnetization
The invention of artificial magnetization has played a huge role in the application and development of the compass.staymagnetismAnd geomagnetism is also a great event in the history of development.
Shen Kuo of the Northern Song Dynasty mentioned another method of artificial magnetization in Mengxi Bittan: "The Fangs can guide the needle by rubbing the tip with a magnet." According to Shen Kuo, technicians at that time could make the needle magnetic by rubbing the needle with a magnet.From the present point of view, this is a kind of utilizationNatural magnetThe magnetic field of the steel needle can make the arrangement of the magnetic domains inside the steel needle tend to a certain direction, thus making the steel needle show magnetism.This method is simpler than the geomagnetic method, and the magnetization effect is better than the geomagnetic method,Friction methodThe invention of not only is the earliest in the world, but also creates conditions for the emergence of a practical magnetic pointing device.
Shen Kuo also talked about various phenomena during friction magnetization in his supplement to Mengxi Bittan: "If you use a magnet to rub the needle tip, it will be sharp, but it will also point to the north, and it is not stony... The north and south are opposite, so there should be differences, which has not been deeply examined." This means that when you use a magnet to rub a sewing needle, the needle tip will sometimes point to the north, and sometimes it will point to the north.From the current point of view, both magnets have N and S poles. When magnetizing, the orientation of the sewing needle tip is different, so is the direction after magnetization.But Shen Kuo did not know this truth. He recorded this phenomenon truthfully and frankly admitted that he did not think deeply.In the hope that future generations can further explore.[1]
Ancestor - Sinan
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the Warring States period
The compass originated in the Warring States Period.It is made of natural magnetite.It looks like a spoon with a round bottom. It can be placed on a smooth "territory" and kept in balance, and can rotate freely.When it is still, the spoon handle will point south.The ancients called it "Sinan". The book Han Feizi at that time said, "The first king established Sinan to end the day and night.".The application of Sinan is recorded in Guiguzi. When Zheng people picked jade, they took Sinan with them to ensure that they would not lose their way.
Spring and Autumn Period
In the Spring and Autumn Period, people were able to grind nephrite and jadeite with hardness of 5 to 7 degrees into various shapes, so they could also make Sinan from natural magnetite with hardness of 5.5 to 6.5 degrees.Wang Chong in the Eastern Han Dynasty clearly recorded the shape and usage of Sinan in his book Lunheng.Sinan uses a whole piece of natural magnet to shape a spoon. The handle of the spoon points to the South Pole and makes the center of gravity of the whole spoon fall right into the middle of the bottom of the spoon. The spoon is placed in a smooth territory. The territory is round inside and outside, and is carved with four dimensions of trunks and branches around, forming 24 directions.This design was completed by the ancients after long-term research after they carefully observed many natural phenomena related to magnetism, accumulated a lot of knowledge and experience.The appearance of Sinan is the practical application of people's understanding of the polarity of magnets.However, Sinan also has many defects. It is difficult to find natural magnets, which are easy to lose magnetism due to striking and heating during processing.Therefore, Sinan's magnetism is relatively weak, and its contact with the site must be very smooth, otherwise it will be difficult to rotate due to excessive rotational friction resistance, and the expected guiding effect cannot be achieved.Moreover, Sinan has a certain volume and weight, which is very inconvenient to carry, which may be the main reason why Sinan has not been widely used for a long time.
Sinan is composed of a bronze plate and a magnetic spoon made of natural magnets. The bronze plate is engraved with 24 directions. The magnetic spoon is placed on the central circular surface of the plate. When it is still, the spoon tail points to the south.[2]
Compass positioning
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Azimuth dial
In order to determine the direction, in addition to the compass, the azimuth wheel is also required.When the compass was first used, there may not be a fixed azimuth plate. With the need of azimuth measurement, a compass with magnetic needle and azimuth plate has emerged.Compass hasGood public opinionUsedcompassDisks andWater compass, dry compass‘
The azimuth plate is still 24 directions, but the plate type has evolved from square to round.In this way, you can determine the direction by looking at the position of the magnetic needle on the direction dial.In the Southern Song Dynasty, Zeng Sanyi recorded the literature on this aspect in "Yin Hua Lu": "The earth snail may have Ziwu Zhengzhen, or use Ziwu Bingren to sew needles." This is the earliest literature record on the compass plate.The "earth snail" mentioned in the literature is the earth compass, that is, the compass plate.In the literatureMagnetic declinationThe knowledge of is applied to the compass.This compass includes not only the meridian needle (the magnetic needle that determines the north and south directions of the geomagnetic field), but also the angle between the meridian needle and the sewing needle (the geographical north and south directions determined by the sun shadow), which is the magnetic declination angle.
Around the panel, there are twenty-four directions. Inside, there is water. The magnetic needle crosses the lamp grass and floats on the water.
Magnetic dip
It has been known that the two magnetic poles of the earth are only close to the geographical north and south poles, not coincident.The magnetic needle points to the magnetic pole of the earth rather than the north and south poles of the geography, so that the magnetic needle points to a slight deviation from the due south and north directions. This angle is called magnetic declination.Because the earth is nearly spherical, the magnetic needle must tilt downward when pointing to the magnetic pole, and there is an included angle with the horizontal direction, which is calledMagnetic dip。The magnetic declination and inclination are different at different locations.When it comes to making compass with geomagnetic method in Wujing Zongyao, written in the Northern Song Dynasty, we pay attention to the use of magnetic dip angle.Shen Kuo talked about the compass's incomplete guide in Mengxi Bi Tan, often slightly to the east.The existence of magnetic declination is pointed out.The discovery of magnetic declination and inclination makes the compass point more accurately.[3]
Magnetic phenomenon
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Discovery process
In the pre Qin period, our ancestors have accumulated a lot of knowledge about this. When exploring iron ore, they often encounter magnetite, that is, magnetite (mainly composed of ferric oxide).These findings have been recorded long ago.Among several articles in Guanzi, these discoveries were first recorded: "If there is a magnet on the mountain, there is gold and copper under it." Similar records are found in other ancient books, such as Shanhaijing.The iron absorption characteristics of magnets have been discovered for a long time. The nine volumes of the Lv's Spring and Autumn Annals have been well versed: "Mercy attracts iron, or introduces it." At that time, people called "magnetism" "kindness." They regarded magnet attracting iron as the attraction of a loving mother to her children.He thought: "Stone is the mother of iron, but there are two kinds of stone: kind and unkind. The kind stone can attract his children, but the unkind stone cannot."
Before the Han Dynasty, people wrote "Ci Shi" for magnetite, which means "Ci Ci Shi".
Since magnets can attract iron, can they also attract other metals?Our ancestors made many attempts and found that magnets could not attract gold, silver, copper and other metals, nor bricks and tiles.In the Western Han Dynasty, people realized that magnets could only attract iron, but not other objects.
When two magnets are put together and close to each other, sometimes they attract each other and sometimes they repel each other.The magnet has two poles, one is called N pole and the other is called S pole.Homosexual poles repel each other, while opposite poles attract each other.However, people at that time did not know this truth, but they were able to detect this phenomenon.
In the Western Han Dynasty, there was a alchemist named Luan Da who made two pieces like things by using the nature of magnets. By adjusting the mutual position of the polarity of the two pieces, sometimes the two pieces attracted each other, and sometimes they repelled each other.Luan Da called it "Duqi".He dedicated this novel gadget to Emperor Wu of the Han Dynasty and demonstrated it on the spot.Emperor Wu of the Han Dynasty was so surprised that his heart was so happy that he made Luan a "general with five benefits".Luan Da used the nature of the magnet to make novel gadgets to deceive Emperor Wu of the Han Dynasty.
The earth is also a big magnet. Its two poles are near the geographical south pole and geographical north pole respectively.Therefore, when the magnets on the earth's surface can rotate freely, they will repel each other because of their sameness and attract each other because of their opposites.The ancients did not understand this truth, but they were very clear about this kind of phenomenon.
Application of magnetic properties
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.It is recorded in Pingzhou Ketan, a book written slightly later than Mengxi Bitan, that "the navigator knows geography, observes the stars at night, the sun at day, and the compass when it is dark." This is the earliest record of using the compass in the world's navigation history.The article points out that the compass was only used when the sun, moon and stars were not visible. It can be seen that the compass was not skilled when it was first used.More than 20 years later, Xu Jing's "The Koryo Sutra of Xuanhe as an Emissary" also recorded a similar record: "Only look at the stars to move forward, and if the dark, use the guide float needle to make the south and north of Coyett." By the Yuan Dynasty, the compass had become the most important instrument for sea navigation.Whether it's sunny or cloudy day and night, I use the compass to navigate.In addition, the wiring diagram of compass needle positions at different navigation locations using compass navigation is also prepared, which is called "needle path".When the ship arrives at a certain place, which direction to use, all the routes are clearly marked as the basis for navigation.
The invention of the compass is the ancient people'sMagnetic phenomenonObservation and research results.In the process of observing and studying magnetic phenomena, ancient ancestors further understood the properties of magnetism and tried to apply them more.It is said that when the First Emperor of Qin built the Ah Fang Palace, one of the palace gates was made of magnets.If an assassin passes by with a sword, he will be immediately attracted and captured by the guards on the spot.There are many such stories. According to the Jinshu Biography of Malone, Malone led his troops westward to Gansu and Shaanxi, and stacked magnets on both sides of the narrow road that the enemy must pass.When the enemy soldiers in armor passed by, they were firmly absorbed and could not move.Malone's soldiers wear rhinoceros armour. Magnets have no effect on them. They can move freely.The enemy thought it was a magic weapon and retreated without fighting.The Foreign Material Records of the Eastern Han Dynasty recorded that there were some reefs and shoals around the islands in the South China Sea containing magnets, which often sucked ships "locked in iron leaves", making it difficult for them to escape.
During the Wei, Jin, Southern and Northern Dynasties, our ancestors had a lot of knowledge about the nature of magnets.Even Cao Zhi, the poet at that time, used the sentence "A magnet leads iron, but not gold" in his poems.It can be seen that he also knows the nature of magnets.Tao Hongjing of the Liang Dynasty in the Southern and Northern Dynasties proposedmagnetic forceThe method of measurement, he pointed out: the fine magnetite is produced in the south and has strong magnetism, which can attract three or four iron needles and make several needles hang on the magnetite end to end.The stronger magnet can attract more than ten iron needles, and even one or two jin knives.Tao Hongjing not only proposed that magnetism can be divided into strong and weak, but also pointed out the measurement method.This may be the earliest record of magnetic measurement in the world.
Our ancestors' research and understanding of the nature of magnets is the basis for the invention and development of the compass.
China invented two methods of artificial magnetization in the Northern Song Dynasty: one is the use ofNatural magnetThe other method is to use the earth's magnetic field to magnetize the steel.
People put a magnetized steel needle through several lamp grass and put it in a bowl full of water. It can float on the water and point out the direction for the ship. This is the compass, the earliest instrument used to point out the direction in the world.Many animals have learned to use the earth's magnetic field to identify directions before us.[4]
Device of magnetic needle
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Shen Kuo method
Shen Kuo introduced four methods:
1. Water floating method - put several rushes on the magnetic needle and float it on the water to 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 fingernail. Since the nail surface is smooth, the magnetic needle can rotate freely and indicate the direction.
4. Thread hanging method - apply some wax in the middle of the magnetic needle, stick a piece of silk, hang it in a place where there is no wind, and then you can indicate the direction.
Shen Kuo also compared the four methods. He pointed out that the biggest disadvantage of the water floating method is that the water surface is easy to shake, which affects the measurement results.The bowl lip rotation method and nail rotation method are flexible due to small friction, but they are easy to fall off.Shen Kuo put more emphasis on the method of thread hanging, 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 up to now - water needle and dry needle.
Meng Xi Bi Tan is Shen Kuo's (1031-1095) work on ancient science and technology in China. It talks about some problems of magnetism and compass.
Production method
Guide fish and guide turtle:
Chen Yuanliang of the Southern Song Dynasty introduced the method of making another kind of guide fish and guide tortoise in "Shi Lin Guang Ji".This kind of guide fish is different from that recorded in the book "General Introduction to the Martial Arts Classics". It is carved in the shape of a fish, which is the size of a finger. A natural magnet is placed in the belly of the wooden fish. The S pole of the magnet points to the head of the fish. After being sealed with wax, a needle is inserted from the mouth of the fish to become the guide fish.Float it on the water, fish head guide, which is also a kind of water needle.
Guide tortoise was a popular new device at that time. A natural magnet was placed in the belly of the woodcut tortoise, a smooth hole was dug under the belly of the woodcut tortoise, and it was aligned and placed on the top pointed bamboo nail standing on the board, so that the woodcut tortoise was placed on a fixed fulcrum that could rotate freely.Since the friction at the fulcrum is very small, the wooden turtle can rotate the guide freely.At that time, it was not used for navigation, but for magic.But that's what happened laterXerocompassIs the first.
The guide turtle was invented no later than 1325.The wooden block is carved into a turtle shape, and a magnet is embedded in the center of the turtle's abdomen. The wooden turtle is placed on a pointed pole. When it is still, its head and tail point north and south.[5]
