What are China's four great inventions?

compass

Before the invention of the compass, human beings often lost their way in the vast sea, resulting in unimaginable consequences. It was China who invented the compass and pointed out the direction for human navigation. Compass is a simple tool to judge the direction. One of four great inventions of ancient china. The main component is a magnetic needle 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 compass is the result of our working people's understanding of the magnetism of objects in long-term practice. Due to productive labor, 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.

Discovery of magnetic phenomena

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. "

Before the Han Dynasty, people wrote magnets as "Guanyin Stone", which means love stone.

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. During 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. 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 two chess pieces, sometimes the two chess 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 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 compass-Sina

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, nephrite and jadeite with hardness of 5-7 degrees can be polished into various shapes, so natural magnets with hardness of only 5.5-6.5 degrees can also be used 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 too much friction and 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 invention of the 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. 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.

Shen Kuo also talked about various phenomena in the process of friction magnetization in Meng Qian's Notes: "If a magnet is used for tit-for-tat, it will be sharp and always guided. Some people point to the north and are not afraid of stones ... On the contrary, there should be differences between the north and the south, which has not been studied in depth." 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.

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 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.

Compass positioning

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 relevant documents in Yanzhi: "Snails either have meridian needles or sew them between 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.

Application of magnetism

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 was only used when the sun, moon and stars could not be seen at that time, indicating that the compass was 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.

China invented two methods of artificial magnetization in the Northern Song Dynasty: one is to rub steel needles with natural magnets, as Shen Kuo said, and the other is to magnetize steel by using the earth's magnetic field.

People put a magnetized steel needle through several rushes and put it in a bowl filled with water, so that it can float on the water to point out the direction for the ship. This is the first instrument in the world to point out the direction-compass. And many animals have learned to use the earth's magnetic field to identify the direction in front of us.

gunpowder

Gunpowder is one of the four great inventions in ancient China. Because it is a mixture of saltpeter, sulfur and charcoal, and people used these three things as medicines to treat diseases at that time, it was named "gunpowder", which means "gunpowder".

Since the Qin and Han Dynasties, alchemists have used sulfur, saltpeter and other substances to make alchemy, and got inspiration from accidental explosions. After many practices, they found the formula of gunpowder. During the Three Kingdoms period, Ma Jun, a clever technician, wrapped gunpowder in paper, made an "explosion head battle" for entertainment and pioneered the application of gunpowder.

At the end of the Tang Dynasty, gunpowder began to be used in the military. People use trebuchets to ignite gunpowder bags and throw them out to burn the enemy. This is the most primitive artillery. Later, people wrapped spherical powder near the head of the arrow shaft and lit the fuse. Later, they shot gunpowder with bows and arrows and burned the enemy. There are also gunpowder, poison, plus some leaching, tung oil and so on. Mash them together to make poison balls. After lighting, shoot the enemy with a bow and arrow, becoming an "enemy of ten thousand people." In the Song Dynasty, people put gunpowder into bamboo tubes, tied tiny "directional sticks" behind the gunpowder, and ignited the nitrate on the fire tube, so that the gunpowder in the tube burned rapidly, generating forward thrust and making it fly to the enemy line to explode. This is the world's first gunpowder rocket. Later, muskets and guns were invented. These are primitive tubular firearms made of bamboo. They are the ancestors of modern guns.

make paper

The invention of papermaking is one of the contributions of the Chinese nation to world civilization.

About 3,500 years ago, in Shang Dynasty, China had written words carved on tortoise shell bones, called Oracle Bone Inscriptions. In the Spring and Autumn Period, tortoise shells and animal bones were replaced by bamboo chips and sawdust, which were called bamboo slips and wooden slips. Oracle Bone Inscriptions and bamboo slips are very heavy. During the Warring States Period, Hui Shi, a thinker, went out to give lectures and took five books and bamboo slips with him, so there was an allusion to being rich in learning and learning. In the Western Han Dynasty, among the court nobles, they wrote with silk or cotton paper. Silk is the general name of silk. Writing on silk is easy. It is not only much more than bamboo slips, but also can be painted on them, but it is expensive and can only be used by a few royal nobles. Paper appeared in the early Western Han Dynasty in the 2nd century BC.

creator

In the first year of Yuan Xing in the Eastern Han Dynasty (A.D. 105), Cai Lun, on the basis of summarizing the previous experience in making silk-woven crystals, invented plant fiber paper suitable for writing with bark, broken fishing nets, rags and hemp heads as raw materials, making paper a widely used writing material.

Papermaking was introduced to Japan through Korea in the 7th century. It spread to the United Arab Emirates in the middle of the 8th century. It was not until the12nd century that Europe began to follow China's example and set up factories to make paper.

Place of invention

Luoyang

print

Printing is one of the four great inventions in ancient China. Woodblock printing, which began in Sui Dynasty, was developed and perfected by Bi Sheng in Song Renzong, resulting in movable type printing, which was spread to Europe by Mongols, so Bi Sheng was later called the ancestor of printing. China's printing is the pioneer of modern human civilization, which has created conditions for the wide spread and exchange of knowledge.

Engraving printing is to carve a protruding reverse writing on a piece of wood with a knife, and then ink it on paper. Every time a new book is printed, the board has to be engraved from scratch, which is very slow. If you make a mistake, you have to engrave it again. You can imagine the hard work.

From A.D. 1004 to 1048, Bi Sheng, an engraver in the Northern Song Dynasty, made a rectangular long column with fine and sticky clay, carved characters on it, and put it into a kiln to make it into movable type. Then, according to the content of the article, put the words in order, put them on the iron frame to make a printing plate, and then put them on the fire to heat and flatten them, and you can print. Take off the movable type after printing and use it next time.

Although this printing method is primitive and simple, it is the same as the principle of modern printing, which makes printing technology enter a new era.

Later, Wang Zhen, a famous agronomist and mechanic in Yuan Dynasty, invented wooden movable type and relatively simple turntable typesetting method suitable for the complex characteristics of Chinese characters, and later invented metal movable type and improved movable type printing. Printed prints of the Tang Dynasty spread to Japan. In the late 8th century, Japan completed the "Dalagni Sutra" of wooden boards, which was later spread to the Democratic People's Republic of Korea, the United Arab Emirates and Eastern Europe. /kloc-In the 5th century, Germans learned to cast buildings with alloys, and movable type printing pioneered by Bi Sheng spread all over Europe.