History of science and technology development history handbook information

China is one of the four ancient civilizations in the world, with a long history and profound culture.

In the long history, the industrious and wise Chinese people have made fruitful achievements in the field of natural science and technology.

Ancient astronomy, physics, chemistry, geology, medicine, and outstanding achievements in architecture, textiles, ceramics, shipbuilding, water conservancy construction, etc., once in the world's leading position, the world-famous four major inventions of papermaking, printing, compass, gunpowder, and so on, contributed to the progress of the entire human civilization.

Astronomy

China was one of the first countries in the world to develop astronomy.

According to the literature, more than 4,000 years ago, Emperor Yao had an official in charge of astronomy.

With the progress of society, ancient astronomy was rapidly developed.

In terms of astronomical observation, China had astronomical records in the sixteenth century BC, and they successively left records of sunspots, comets, meteors, novae, five stars of the sun and moon, as well as a variety of star charts, star charts, rich in content, continuous, and many of which are still the earliest in the world; in the astronomical theories and astronomical instruments, they created the Hun-Tian theory of the universe and invented the armillary sphere, the armillary sphere, the armillary sphere and the armillary sphere. In terms of astronomical theory and astronomical instruments, they created such an insightful view of the universe as the Huntian theory, and invented the Hunyi and Jianyi instruments to illuminate the future generations of astronomical instruments; in terms of calendar, as early as in the sixteenth to eleventh centuries B.C., China already had a primitive calendar, which is still inherited today after continuous reforms and improvements, which takes care of the solstice month and takes into account the year of return, and it is the unique yin and yang combined calendar.

Ancient Chinese celestial events

As early as the Neolithic era, Chinese ancestors noticed a close connection between the weather and the cycles of the celestial events, and began observing the sun, the moon, and other celestial events.

Since then, the Chinese people have long been diligently committed to the observation and recording of celestial phenomena, and have made brilliant achievements, leaving behind a variety of records on sunspots, comets, meteors, novae, etc.

These celestial phenomena are the first to be recorded in China, and the first to be recorded in China.

These astronomical chronicles are not only detailed and chronological, many of them are the earliest records in the world, and still play an important role in the study of modern astronomy, which is an extremely valuable cultural heritage.

Sunrise yellow with black gas - the record of black

Black is a gas vortex on the surface of the Sun, due to its temperature than the rest of the Sun's temperature is low, so the light is also darker than the rest of the place, from the Earth as if the surface of the Sun appeared as black spots or patches, so also known as the sun spot.

About sunspots, China has the world's earliest record of observation.

About 140 years ago, in the book "Huainanzi", there is "the sun in the administrative crow" of the account.

Now the world's earliest recognized record of sunspots, is contained in the "Book of Han" - "Five Elements" in the first year of the River Ping (28 BC) in March of the appearance of sunspots: "River Ping first year of ...... March Heiwei, the sunrise yellow, there is a black gas as big as a money, living in the center of the day. " This record recounts the time and location of the appearance of the sunspot in detail.

Europe on the sunspot chronicle of the earliest time is 807 AD in August, when it was also mistaken for Mercury transits phenomenon, until the Italian astronomer Galileo 1660 invented the astronomical telescope, only to confirm that the black is really there.

And before that, there have been 101 records of the black spot in our history, which not only have the time, but also the shape, size, location, and changes, etc.

It's hard to believe that there is no such thing as a black spot.

It is no wonder that the American astronomer Hale would marvel: "Ancient China observed the heavens with such diligence, it is amazing.

They observed the sun spots, about 2,000 years earlier than the West, the historical records are endless, and are very correct and credible."

A Star Comes into the Big Dipper - The Record of Comets

A comet is a small massed celestial body orbiting the Sun with a distinctive cloud-like appearance.

A comet consists of three parts: the hair, the nucleus, and the tail.

The comet's tail is the comet close to the sun, the comet hair becomes larger, the solar wind and the sun's radiation pressure of the comet's gas and dust pushed away from the generation of the comet hair, the shape of which resembles a large broom, so the Chinese folk comet is also called the "broom star".

China's observation and study of comets has a history of more than 4,000 years, with the world's earliest and most complete record of comets.

In ancient China, comets were called "star comets", and the Spring and Autumn Annals recorded a comet that appeared in the 14th year of the Duke of Lu (613 BC): "In the seventh month of the autumn, there was a star comet in the Big Dipper.

"This is the earliest record of Halley's Comet.

Halley's Comet is a periodic comet, appearing once every 76 years, from the beginning of the fourteenth year of Duke Lu Wen to the Qing Dynasty Xuantong two years (1910 AD), Halley's Comet appeared 31 times, each time, China has a detailed record.

Such as the "Historical Records - Qin Shihuang Benji" recorded: "Shihuang seven years, the comet first out of the East, see the North, see the West in May, ...... comet resumed to see the West for sixteen days." This record of the number of years, months and days, the location and modern scientists projected to be completely consistent.

By the Warring States period, China's observation of the comet has accumulated a relatively rich experience.

Mawangdui, Changsha, No. 3 tomb of the Han Dynasty, there are 29 Palindromes painted with various forms of comet map, the comet's comet tail has a wide and narrow, there are long and short, there are straight and curved, and the number of strips varies, the head of the comet there is a circle or a circle, there are circles in the center of the circle there is also a small dot or circle, which indicates that the people at that time have paid attention to the comet of the different forms of the degree of precision of the observations on today, is also of scientific value, but also to the point that the comet is not the same as the one in the first half of this century, but it is not the only one. The accuracy of its observations today, is also of scientific value.

On the cause of the comet's tail, China also had a relatively early explanation of the correct, "Jinshu - Astronomical Records" recorded: "comet body without light, Fuzhi and for the light, so the evening to see the east pointing, the morning to see the west pointing.

In the day north and south, all with daylight and finger.

Stuttering its mane, or long or short ...... ".

And Europe until the sixteenth century mistakenly believed that comets were a burning phenomenon in the atmosphere.

China's comet observations, highly praised by modern Western astronomers.

The Frenchman Baldé said in the 1950s, after studying the General Catalogue of Comet Orbits, "The best records of comets (with very few exceptions) are those of China."

Eclipse of the Sun in the month of Shuo, Xinmao - a record of solar eclipse

A solar eclipse is a phenomenon in which the Sun is obscured by the Moon.

When the Moon, in its orbit around the Earth, sometimes comes between the Sun and the Earth, at which time the Moon's shadow falls on the surface of the Earth, observers located in the shadow will see the Sun being obscured by the Moon, and this is a solar eclipse.

? When a solar eclipse occurs, the sun, which is originally radiant, will suddenly become dim and dark, becoming a dark round surface, while the stars appear in the daytime sky. Such a peculiar sight, which was a shocking event for the ancients who did not understand its cause, naturally became the celestial phenomenon that the Chinese ancestors focused on observing.

As early as three thousand years ago, there were records of solar eclipses in the Yinxu oracle bones.

The Book of Books - Yinzheng Chapters recorded: "It is the first day of the month in the third quarter of autumn, and the star is not set in the room ......, goze plays the drum, and the mean is out of gear, and the cover is gone ......", which describes how people panicked when the solar eclipse occurred in the first year of the Xia dynasty Zhongkang. The eclipse occurred in the first year of Zhongkang in the Xia Dynasty, when people were panicked.

"Poetry Classic - Xiao Ya" also recorded the occurrence of solar eclipse in the form of poetry: "the intersection of October, Shuozhi Xinmao, the sun has an eclipse of the".

From the Spring and Autumn period in China to the Qing Dynasty Tongzhi eleven years (770 BC - AD 1874), there are records of solar eclipse **** 985 times, of which the year and month do not match, no eclipse can be examined only 8 times, less than 1% of the total.

? The occurrence of solar eclipses has a certain periodicity.

China is one of the earlier countries in the world to discover the cycle of solar eclipses.

In the late Western Han Dynasty, Liu Xin summarized a cycle that 23 solar eclipses occur in 135 months.

Since about the third century AD, China has been able to predict the direction of the first loss and recirculation of solar eclipses, and by the Tang Dynasty, the prediction of solar eclipses had become more accurate.

The stars fall like rain in the night - the record of meteors

In the starry night sky, you can often see a flash of white light, which is a meteor.

Sometimes you can also see a region of the sky with countless bright lights in all directions, like rain, which is the spectacular phenomenon of popular rain.

Meteors and meteor showers are light trails produced by the friction and combustion of dust particles and solid blocks called meteoroids in interplanetary space as they break into the Earth's atmosphere.

? The Chinese recorded meteor swarms and meteors earlier than other countries.

The ancient book "Bamboo Book Chronicles" has a record of meteors: "In the fifteenth year of the Xia Emperor's Decade, the stars fell like rain in the night." Zuo Zhuan" records, Lu Zhuanggong seven years "summer April Xin Mao night, the stars are not visible, the star in the middle of the night fell like rain", is the world's earliest record of the Lyrae meteor shower.

China's ancient meteor shower records as many as 180 times.

? The Chinese not only recorded meteors, but were able to pinpoint the origin of meteorites: "When a star falls to the ground, it is a stone" (in Shi Ji - Tian Guan Shu.

) In Europe, three meteorites were found in 1768 AD, to which the Paris Academy of Sciences elected Lavoisier to do the research, he concluded that "the stone in the ground, did not enter the soil, lightning and thunder, breaking out of the ground, not from the sky." Until 1803 AD Europeans know the origin of meteorites.

Guest stars in the room - the record of novae and supernovae

Certain stars that are usually very faint, suddenly burst out thousands to millions of times brighter than the original brightness of the light, called a nova, and some of the brightness increased to 100 million or even hundreds of millions of times, called a supernova.

Later, they are gradually weakened, as if they were guests in the starry sky, so they were called "guest stars" by the ancients.

? The emergence of novae and supernovae has been documented in China for a long time.

The oracle bone inscriptions of the Shang Dynasty recorded a new star that appeared near Alpha Scorpii in about the 14th century BC.

The Book of Han - Tianwen Zhi (汉书-天文志)records that "In the fifth month of the first year of Yuan Guang, the guest star was seen in the room." This record is a new star appeared in 134 BC, this new star is the first new star recorded in both Chinese and foreign history books, and other countries than the record, China's record not only write the time, but also the orientation, so the French astronomer Bio in the book "compilation of nova" when the record of the "Book of the Han" as the first.

At the end of the 18th century, a nebula in the shape of a crab was discovered near the star Tian Guan through a telescope, and was named the Crab Nebula.

In 1921, scientists discovered a pulsar in the Crab Nebula that has the shortest period of any pulsar ever discovered, and is the only full-wave pulsar known to date.

Based on the rate of expansion of the Crab Nebula, this star would have been produced by a supernova that erupted in 1054 AD.

And this supernova is well documented in our history book, the Song Huayao Zhiqi (宋會要辑稿).

? Since the Shang Dynasty to the end of the 17th century, China's history books *** recorded about 90 or so novae and supernovae, of which about 12 belong to the supernova, such a rich and systematic record of nova outbursts through the ages is unique in the world.

Ancient Chinese astrometry

Astrometry is the oldest and most basic branch of astronomy, which mainly studies how to determine the position of stars and the time of their arrival at a certain position.

China's ancient astronomers designed and manufactured a variety of sophisticated and advanced astrometric instruments and observatories, and made great achievements in astrometry, leaving behind many valuable star charts, star lists and other historical materials.

Hunyi

China's ancient use of astrometric instruments are mainly hunyi, simple instrument, etc.; the performance of the celestial visual movement of the instrument is mainly hunxiang and so on.

(1) Hunyi The Hunyi is an instrument for measuring the heavenly bodies based on the theory of the Hunyi theory.

Huntian theory is an important cosmological theory in ancient China, that "the sky as a chicken, the body of the sky as round as an egg pill, the earth as a chicken in the yellow", the sky is full of water, the sky is supported by the gas, and the earth floats on the water surface.

The great circle of the sky is divided into 365.25 degrees, and the two ends of the spinning axis of the muddy sky are called the South Pole and the North Pole, and the equator is perpendicular to the celestial pole, and the ecliptic is diagonally intersected by the great circle of the sky, and the yellow equator intersection angle is 24 degrees.

It is on this basis that the Hunyi instrument was designed.

The invention of the Hunyi instrument in China occurred between the fourth and first centuries BC (i.e., from the middle of the Warring States period to the Qin-Han period).

The early armillary sphere was relatively simple, and was improved by astronomers through the ages. In the Tang Dynasty, the astronomer Li Chunfeng designed a more sophisticated armillary sphere.

The whole instrument is divided into three layers. The outer layer is called the hexagram, which includes the horizon circle, meridian circle and equatorial circle.

The middle layer is called the Three Stars Instrument, which consists of the White Way Ring, the Ecliptic Ring and the Equatorial Ring.

The inner layer is called the Tetragrammaton, which consists of a tetragrammaton ring and a peep tube.

The existing Ming Hunyi is basically this structure, the difference is that the White Way ring in the Three Stars is canceled, and the two-part ring and the two-to ring are added.

Because the rings of the armillary sphere are too complex, covering the sky area and affecting the observation, Guo Shoujing, an astronomer in the Yuan Dynasty, simplified it and created the simple instrument.

The simple instrument

Yuan dynasty astronomer Guo Shoujing created in 1276 AD, a measurement of the sky *** position of the instrument.

Because of the complex structure of the Tang and Song Hunyi to innovate and simplify, so called simple instrument.

It consists of an equatorial device and a terrestrial device that are independent of each other, and is divided by the time of the Earth's revolution around the Sun, which is 365.25 days.

The equatorial device of the simple instrument is used to measure the depolarization and ingress (equatorial coordinates) of celestial bodies, and has the same basic structure as the celestial chart equatorial device widely used in modern telescopes.

It consists of two brackets, high in the north and low in the south, holding the polar axis in the positive north-south direction, and rotating around the polar axis is a four-tour double ring, with cross filaments at the ends of the peep tubes on the four-tour ring, which is the ancestor of the cross filaments in the telescopes of the later generations.

At the south end of the polar axis, the fixed Centurion ring and the traveling equatorial ring are placed in duplicate.

In order to reduce the friction between the Bacchus ring and the equatorial ring, Guo Shoujing installed four small cylinders between the two rings, this structure is the same as the modern "roller bearings" to reduce the friction resistance principle.

The leveling device of the simple meter is called the Lifun meter, which is basically similar to the modern leveling latitude and longitude meter.

It consists of a stationary cathode ring and an upright, rotating around the plumb line, with a peep tube and a boundary scale.

This device measures the horizon orientation and horizon altitude of celestial bodies.

The base frame of the simplex is equipped with an orthographic scheme to correct the north-south orientation of the instrument.

In the Ming system of janitorial instruments, the positive program was changed to a sundial.

The creation of a simple instrument is a major leap in the history of China's astronomical instrumentation, is an advanced technology in the world at that time.

Europe until more than three hundred years later in 1598 by the Danish astronomer Diya invented a similar device.

Guo Shoujing created a simple instrument, which was melted down as scrap copper by the missionary Gillian in 1715.

The jianyi now preserved at the Zijinshan Observatory in Nanjing is a replica from the second to seventh years of the Zhengtong period of the Ming Dynasty (1437-1422 AD).

Guo Shoujing (1231-1316), a native of Xingtai, Hebei, was a famous astronomer of the Yuan Dynasty.

Guo Shoujing studied astronomy, arithmetic and water conservancy under his grandfather Guo Rong since childhood.

He was particularly interested in astronomy, and often made his own astronomical instruments for observing the sky.

In 1276, Kublai, the first emperor of the Yuan Dynasty, ordered the preparation of a new calendar, and Guo Shoujing was ordered to participate in the revision of the calendar.

Four years later, the new calendar, the Calendar of the Ruling of the Hours, was almost complete.

This is an excellent calendar in ancient China, and Guo Shoujing made outstanding achievements in the process of making it.

Guo Shoujing, at the beginning of the calendar, proposed that "the basis of the calendar lies in the test, and the instrument of the test is not preceded by the meter".

To this end, within three years, he **** designed a simple meter, high table, sundial timer, as well as a standing instrument, eclipse instrument, Linglong instrument and other 12 kinds of new astronomical instruments, the degree of sophistication and accuracy greatly exceeded the predecessor.

In addition, he was also an outstanding water conservancy expert and geographer, who presided over a number of important water conservancy projects, which are still praised by Chinese and foreign experts.

Hunxiang, False Celestial Instrument

Hunxiang Hunxiang is a kind of instrument that performs the visual movement of celestial bodies.

It draws the sun, the moon, the twenty-eight constellations and other celestial bodies, as well as the equator and the ecliptic, on a spherical surface, which enables people to understand the celestial phenomena at any time without time constraints.

During the day one could see the stars and the moon, which were not visible in the sky at that time, and not in a bad position; on cloudy days and at night one could also see where the sun was.

With it, you can perform the moments and directions of the sun, the moon, and other stars rising in the east and setting in the west, and you can also visualize the reasoning that the day is long in the summer and the night is long in the winter, and so on.

China's first Hunxiang was created by Geng Shouchang in 70-50 BC.

Later generations have attached great importance to the manufacture of the Hunxiang, Zhang Heng, a line, Su Song and many other astronomers have been designed, these objects are now gone, the only surviving celestial instrument in the Qing Dynasty can be regarded as a replica of the ancient Hunxiang.

False Celestial Instrument The general Hunxiang, mostly people standing outside the ball to see, which for the calculation of coordinates and observation of the starry sky has its convenient place, but for the symbol of the vault of the sky, is not realistic enough.

In the Song Dynasty, Su Song and Han Gonglian*** developed a device that could view the image from the inside.

It is in the sphere corresponding to the position of the sky stars chiseled with small holes, people into the ball, you can see points of light such as the stars in the sky, turn the sphere, then "in the star, dusk, evening (dawn), should be all the time to see in the trick.

"This false celestial instrument can be said to be the ancestor of the modern planetarium.

Dengfeng Observatory

Ancient Chinese astronomical observatory, located in Dengfeng County, Henan Province, designed and manufactured by Guo Shoujing, an astronomer of the Yuan Dynasty, in 1279.

Observatory plane is square, the side length of more than 16 meters, platform height of 9.40 meters, the platform of the north side of the stone Kei 31.19 meters long, commonly known as the measuring tape.

Measuring tape and the observation deck constitutes a giant kuai table, stone kuai in the direction of the meridian.

There are scales in the center and on both sides of the surface to measure the length of the shadow.

According to the change in the length of the projection of the beams on the platform, the spring equinox, summer solstice, autumn equinox and winter solstice are determined, dividing the four seasons.

In order to observe the accuracy, Guo Shoujing also invented a "Jing Fu", that is, with a width of two inches, four inches long copper leaf, the top through a small hole, put on the bracket in the surface of the Kei moving back and forth, the use of small holes in the principle of imaging the sun and the table beams through the small holes of the Jing Fu is clear and real, as thin as a hair on the Kei surface projection.

When the beam shadow is equal to the sun image, you can measure the length of the sun shadow.

Star charts and star tables

In ancient times, China achieved a lot of astrometric results, leaving many valuable star charts and star tables for future generations.

The star catalog is a compilation of the coordinates of the measured stars.

Around the fourth century BC, during the Warring States period, the Wei man Shi Shen compiled a book called Astronomy*** in 8 volumes, which was later called Shi's Star Scriptures.

Although it was lost after the Song Dynasty, we can still see some fragments of it today from the Tang Dynasty astronomical work Kaiyuan Zhanshingjing, from which we can organize a Shi's Star Table, which has the positions of the 28 distance stars and the equatorial coordinates of 115 stars.

This is one of the oldest star catalogs in the world.

The star chart is an image record of astronomers' observation of the stars, which truly reflects the achievements of astronomers in astrometry during a certain period of time.

At the same time, it is an important tool for astronomers to recognize and measure the stars, and its role is like a map in geography.

As early as the pre-Qin period, China's ancient astronomers began to draw star charts.

The earliest existing star charts depicted on paper are the Dunhuang star charts of the Tang Dynasty.

The Tang Dunhuang star map was first discovered in the Dunhuang Cave of Sutras, and was stolen by the Englishman Stein in 1907, and is still preserved in the Museum of London, England.

It was painted in 940 AD, there are 1350 stars on the map***, it is characterized by the equatorial region using cylindrical projection, the polar region using spherical projection, and the same method of drawing modern star charts, is the earliest in our country to date to use the circular, horizontal two drawing method of the star map.

In 1971, a star map was found in a Liao Dynasty tomb in Xuanhua District, Zhangjiakou City, Hebei Province.

The map was painted in 1116 AD, used for tomb decoration, star map painting in the diameter of 2.17 meters within the circle, drawing method for the cover map type, the figure embedded in the center of a 35-centimeter-diameter bronze mirror, the outer circle is the Chinese twenty-eight constellations, the outermost is derived from the Babylonian zodiac, which can be seen in the field of astronomy in the signs of cultural exchanges between China and foreign countries.

In 1974, in the northern suburbs of Luoyang, Henan Province, the top of a tomb in the Northern Wei Dynasty, found another painted in the Northern Wei Dynasty Xiaochang two years (526 AD) of the star map, the whole map has more than 300 stars, some with straight lines associated with the constellations, the most obvious is the Big Dipper, the center of the Milky Way in pale blue across the north and south.

The whole map is 7 meters in diameter.

This star map is China's current archaeological discoveries in the early years, the larger format, the number of stars is more of a picture.

Suzhou stone astronomical map in the Suzhou Museum, is one of the world's oldest surviving stone star charts, carved in 1247 (Dingwei year of the Southern Song Dynasty), mainly based on the observations of 1078-1085 AD (Northern Song Dynasty Yuanfeng years).

The chart is about 2.45 meters high and 1.17 meters wide, and there are 1434 stars on the chart*** in accurate positions.

The whole map of the Milky Way is clear, and the River Han is bifurcated, which is detailed and fascinating, and to a certain extent reflects the level of development of astronomy at that time.

The invention of the compass

Ancient folk commonly used thin iron leaves cut into a fish shape, the fish's abdomen slightly concave, like a small boat, magnetized floating on the water surface, can point to the north and south.

At that time, this was used as a game.

Cui Bao of the Eastern Jin Dynasty mentioned this "guiding fish" in the "Ancient and Modern Notes".

In the Northern Song Dynasty, Zeng Gongliang wrote in Wujing General Essentials about the method of making and using guide fish: "Cut thin iron leaves, two inches long and five minutes wide, with the head and tail as sharp as a fish, put them in a charcoal fire, and then burn them in red, then inscribe the head of the fish in the fire, and then dip it into a pot of water with the tail facing the sub-base and then stopping it when the tail is gone for a few minutes, and then collect it in a sealed container.

When used, put the water bowl in a windless place flat, the fish in the water, so that floating, its head often to the afternoon also." This is a method of artificial magnetization, which uses the earth's magnetic field to magnetize iron sheets.

That is, a piece of red-hot iron is placed in the direction of the meridian.

The internal molecules of the red-hot iron sheet are in a more active state, so that the iron molecules are aligned in the direction of the Earth's magnetic field to achieve the purpose of magnetization.

Dipped into the water, this arrangement can be fixed faster, and the fish tail tilted slightly downward can increase the degree of magnetization.

The invention of the artificial magnetization method played a huge role in the application and development of the compass.

In the history of the development of magnetism and geomagnetism is also a major event.

Shen Kuo of the Northern Song Dynasty mentioned another method of artificial magnetization in Mengxi Bianzhan: "Fangjia can guide the compass when he uses a magnet to move the needle blade." According to Shen Kuo, the technicians at that time used magnets to rub sewing needles, which could make the needles take on magnetic properties.

From today's point of view, this is a way to use the magnetic field of natural magnets to make the arrangement of magnetic domains inside the steel needle tend to a certain direction, so that the steel needle shows magnetism.

This method is simpler than the geomagnetic method, and the magnetization effect is better than the geomagnetic method, the invention of the friction method is not only the world's earliest, but also for the emergence of practical value of the magnetic pointers, to create the conditions.

Shen Kuo also talked about the friction method of magnetization of the various phenomena produced in the complementary talk of "Mengxi Bianchuan": "to the magnet Mo needle sharp, the sharp place is often a guide, but also point to the north of the person, the fear of the nature of the stone is also not ......, the north and south of the opposite, the rationale should be different, did not y examine the ear. " This is to say, with a magnet to rub the sewing needle after the needle blade sometimes guide, but also sometimes point north.

From today's point of view, magnets have N and S poles, magnetized sewing needle needle blade orientation is different, then the magnetized pointing is also different.

But Shen Kuo did not know this, he really recorded the phenomenon and frankly admitted that he did not do in-depth thinking.

In anticipation of further exploration by future generations.

On the magnetic needle device method, Shen Kuo introduced four methods: 1. water floating method - will wear a few corduroy on the magnetic needle floating in the water, you can indicate the direction.

2. Bowl lip spinning method - the magnetic needle rests on the edge of the bowl, the magnetic needle can rotate, indicating the direction.

3. Nail spinning method - the magnetic needle rests on top of the fingernail due to the smooth surface of the nail, the magnetic needle can be rotated freely, indicating the direction.

4. Wisps hanging method - in the middle of the magnetic needle coated with some wax, stick a silk, hanging in the place where there is no wind, you can indicate the direction.

Shen Kuo also compared the four methods, he pointed out that the biggest drawback of the water floating method, the water is easy to sway affecting the measurement results.

Bowl lip spinning method and fingernail spinning method, due to small friction, rotation is very flexible, but easy to fall.

Shen Kuo more emphasis on the strand hanging method, he believes that this is a more ideal and practical method.

In fact, Shen Kuo pointed out that the four methods have been summarized so far the two major systems of compass devices - water needle and dry needle.

Mengxi Bianan (梦溪笔谈), a work on ancient Chinese science and technology by Shen Kuo (1031-1095), deals with some of the problems of magnetism and the compass.

Chen Yuanliang of the Southern Song Dynasty introduced the production of another type of guiding fish and guiding turtles in the book, Things of the Forest.

This kind of guiding fish is not the same as the one recorded in the book "General Essentials of Martial Arts", it is carved into a fish shape with wood, as big as a finger, and a natural magnet is placed in the belly of the wooden fish, and the S-pole of the magnet is pointing to the head of the fish, and then after sealing it with wax, it is inserted into the mouth of the fish with a needle, and then it becomes a guiding fish.

Float it on the surface of the water, the fish head guide, which is also a class of water needle.

The Guide Turtle was a new device popular at the time, where a natural magnet was placed inside the belly of a wood-carved turtle, and a small smooth hole was dug underneath the belly of the turtle, aligned with and placed on a bamboo nail with a slippery tip standing upright on a wooden board, so that the wooden turtle was placed on a fixed pivot point that was free to rotate.

Because of the low friction at the pivot point, the tortoise was able to rotate the guide freely.

At the time it was not used for nautical pointing, but for illusions.

But this was the precursor to the dry compass that came later.

The compass turtle was invented no later than 1325.

Wooden blocks carved into a tortoise, the center of the tortoise abdomen embedded with magnets, wooden tortoise placed on a pointed upright, the head and tail pointing to the north and south when stationary.