Composer: the great ancestor-Guo Shoujing.
Send Guo Shoujing to his fellow countryman friend Liu's door to study, so as to broaden his horizons and let his grandchildren continue their studies. Liu is proficient in Confucian classics and astronomy. At that time, he was mourning his father and studying in Zhang You. Guo Shoujing learned a lot from him. More importantly, Guo Shoujing met his good friend Wang Xun there. Wang Xun was four or five years younger than Guo Shoujing, and later he was also an outstanding mathematician and astronomer. This pair of good friends later worked closely together on the astronomical calendar and made outstanding contributions.
Show one's skill by repairing water
Guo Shoujing studied under Liu for a short time. In 125 1 year, Liu was called into Beijing by Kublai Khan. After Liu left Xingtai, Guo Shoujing's whereabouts were not clearly recorded in the history books. Later, Liu Cai knew that he had been introduced to his old classmates. 1260, Zhang Wenqian went to Daming Road (he was in daming county, Hebei Province) and other places as the minister of Fu Xuan, followed by Guo Shoujing. There, he cast a set of formal bronzes from the lotus flowers he tried when he was young, and left them for local use. Later, the observatory of the Yuan government also adopted this instrument.
Guo Shoujing followed Zhang Wenqian in surveying the terrain, planning the water conservancy scheme and helping to do some practical work. Over the past few years, Guo Shoujing's scientific knowledge and technical experience have become more abundant. Seeing that Guo Shoujing was mature, Zhang Wenqian recommended him to Kublai Khan in Yuan Shizu on 1262, saying that he was familiar with water conservancy and smart. Yuan Shizu summoned Guo Shoujing in Xindu (now near Duolun, Inner Mongolia).
When Guo Shoujing first met Yuan Shizu, he put forward six suggestions for water control. The first suggestion is to repair the waterway from Zhongdu (now Beijing) to Tongzhou (now Tongxian); The second and third articles are about the suggestion that his hometown has local urban water and irrigation channels; The fourth part is about water conservancy suggestions in Cizhou (now Cixian County, Hebei Province) and Handan. Articles 5 and 6 are suggestions on the rational utilization of the Qinhe River in the Central Plains (now Henan Province) and the construction of the river course on the north bank of the Yellow River. These six items are all practical plans put forward after careful investigation, and the routes, benefit areas and other items are clearly written. Yuan Shizu thought that Guo Shoujing's suggestion was very reasonable, so he appointed him to remove all canals, take charge of the renovation and management of canals around the country, and was promoted to Deputy Canal Ambassador of Yin Fu next year.
1264 (the first year of Yuan Shizu to Yuan Dynasty), Zhang Wenqian was sent to Xixia (now Gansu, Ningxia and western Inner Mongolia) for inspection. Many canals have been built along the banks of the Yellow River. Han Yan and Tanglai Canal in Ningxia (now Yinchuan) is an ancient canal with hundreds of miles, vertical and horizontal branches and large irrigation area, which is one of the important agricultural bases in northwest China. Genghis Khan did not know how to protect agricultural production when he conquered Xixia. Wherever the soldiers and horses went, the gates and dams were destroyed and the channels were blocked. Zhang Wenqian certainly knows this situation. He went to Xixia to rectify local administration on the one hand and revive water conservancy and agricultural production on the other. So I brought my colleagues from Guo Shoujing who are good at water conservancy.
When Guo Shoujing got there, he immediately began to rectify. In some places, old canals were dredged, new canals were opened, and many sluices and dams were rebuilt. The local people have been looking forward to water for a long time, so they naturally try their best to support such a crucial event. Thanks to everyone's efforts, these projects were actually completed in a few months. On the day when the floodgate was opened, people looked at the endless canal water, how happy they were.
After the canal was completed, Guo Shoujing left Xixia. Before returning to Beijing, he went upstream to explore the birthplace of the Yellow River. In the past, although there were some records of Heyuan exploration in history books, the accounts written by generals and envoys passing by this area were not the result of scientific investigation. Some records are only from hearsay, but they are not accurate. Guo Shoujing was the first person who made a special trip to explore the true source of the Yellow River for the purpose of scientific investigation. Unfortunately, Guo Shoujing's achievements in exploring Heyuan have not been recorded and handed down. Later, in 1280, another explorer was ordered by Yuan Shizu to visit Heyuan. The course of this exploration is recorded in a monograph of Heyuan, and there are many valuable achievements. Undoubtedly, Guo Shoujing, as a pioneer, had a considerable influence on Du Fu's poems.
1265, Guo Shoujing returned to Shangdu. In the same year, he was appointed as the warden, assisting the warden in charge of the restoration of canals, dikes, bridges and dams. 127 1 year, promoted to municipal water director. 1276, Du Shuijian was merged into the Ministry of Industry and became a doctor of the Ministry of Industry.
Exquisite astronomical instruments
China is one of the countries with advanced astronomy. After the Western Han Dynasty, the equipment and organization of the National Astronomical Observatory reached a fairly perfect level. One of its main tasks is to make a calendar. The content of ancient calendars in China is extensive. Including the movement of the sun and the moon and the calculation of their positions, the compilation of the annual calendar, the position prediction of the five major planets, the advance of solar and lunar eclipses, etc. Calendar is related to production, life and even political activities. Therefore, this work has always been highly valued. If a calendar is used for a long time, the errors will become more and more obvious and need to be revised. Every major calendar revision will always bring some creative and innovative progress, such as the accuracy of basic astronomical data, new achievements in astronomical theory or new inventions in calculation methods. The development of calendar is a main line in the history of astronomy in China.
In the early years of the Yuan Dynasty, the Jin Dynasty's Rebuilding Daming Calendar was used. This calendar was revised on 1 180 (the 20th year of Jin Shizong Dading). In the past few decades, the accumulation of errors has become more and more obvious, and several events that are inconsistent with the actual phenomenon have appeared. It needs to be revised again.
1276 (in the twentieth year of Yuan Dynasty), the Yuan army captured Lin 'an (now Hangzhou, Zhejiang Province), the capital of the Southern Song Dynasty, and national reunification was a foregone conclusion. This year, he moved the capital to Dadu, adopted the suggestion of the late minister Liu, and decided to revise the old calendar and promulgate the Yuan Dynasty's own calendar. Therefore, the Yuan government ordered the organization of the Calendar Bureau in Xindu to mobilize the national astronomers and revise the new calendar.
In name, Zhang Wenqian is in charge of this work, but in fact, Wang Xun, who is proficient in astronomy and mathematics, is in charge of calendar affairs and specific compilation.
At that time, Wang Xun thought of his old classmate Guo Shoujing. Although Guo Shoujing's official position has been in the water conservancy department, Wang Yao has long known that he is good at making utensils and is familiar with astronomy. Therefore, Guo Shoujing was recommended by Wang Xun to participate in the revision of the calendar, and was ordered to make instruments for actual observation. Since then, the history of Guo Shoujing's scientific activities has opened a new chapter, and he has played a very talented role in the field of astronomy.
Guo Shoujing first inspected the instruments and equipment of the Metropolitan Observatory. These musical instruments are relics of the Jin Dynasty. Among them, the armillary sphere belonged to the Northern Song Dynasty, and it was transported to Yanjing from there after the Jinbing attacked Bianjing (now Kaifeng, Henan), the capital of the Northern Song Dynasty. At first, a * * * touched three soldiers. Because the latitude difference between Bianjing and Yanjing is about 4 degrees, it cannot be used directly. The civil servants of the Jin Dynasty once modified one of them. This modified musical instrument was also destroyed in the early Yuan Dynasty. Guo Shoujing transformed the remaining one and put it into temporary use. In addition, with the passage of time, the standard watches used by the Observatory have become distorted. Guo Shoujing immediately set about repairing it and put it in the right place.
After all, these instruments are too old. Although it has been trimmed, it still cannot meet the increasingly sophisticated astronomical observation requirements. Guo Shoujing had to create a set of more sophisticated instruments to lay a solid technical foundation for calendar revision.
In ancient times, making calendars required two main astronomical observations. First, determine the exact time of the 24 solar terms, especially the winter solstice and summer solstice; The instrument used is a standard watch. One is to determine the position of celestial bodies on the celestial sphere, and the main tool used is the armillary sphere.
The "table" in the standard table is a pole or stone pillar standing vertically on the ground; "Gui" is a slate extending horizontally from the heel of the watch to the north. Whenever the sun turns due south, the shadow falls on the water of Guiyu. By measuring the length of the shadow, we can calculate the time of each solar term, such as winter solstice and summer solstice. When the shadow is the longest, the solstice of winter comes; In the shortest time, the summer solstice came. It is the oldest and most common astronomical instrument in China.
This kind of instrument looks simple, but it will encounter several difficulties in use.
The first is that the shadow edge is not clear. The closer the shadow is to the edge, the brighter it becomes. It is difficult to draw a clear line where the shadow ends. If the boundary of the shadow is not clear, the shadow length will be inaccurate.
The second problem with using standard meters is that the technique for measuring the shadow length is not accurate enough. In ancient times, rulers for measuring length generally only had energy of minutes at most, which could be estimated to centimeters, that is, one tenth. According to the traditional method for thousands of years, the length of the surface shadow during the winter solstice can be measured. If there is a little error in the measurement, it is enough to make the calculated winter solstice time differ by one or half an hour. This is a big mistake.
Also, the old standard can only observe the sun shadow. The light of the stars and the moon is very weak, so the old standard watch can't observe the star shadow and the moon shadow.
Scientists have made great efforts to solve these problems since the Tang and Song Dynasties, but they have never been well solved. Now, these difficulties are still in front of Guo Shoujing. What shall we do? Guo Shoujing first analyzed the causes of the mistakes, and then found out the ways to overcome the difficulties.
First, he tried to raise the pole of the standard watch to five times, so the shadow of the watch was stretched to five times. When the shadow is elongated, the error of calculating the time of each solar term in proportion can be greatly reduced.
Secondly, he created an instrument called "mirror volt", which made the sunlight shining on the gauge pass through a small hole and then hit the surface of the gauge, so that the edge of the shadow was very clear and the accurate shadow length could be measured.
Secondly, he also created an instrument called "Peeping at a few" so that watches can also be observed under the irradiation of stars and the moon.
In addition, he also improved the technology of measuring length, so that the position of "minute" can only be directly measured to the position of "centimeter", and the position of "milli" can only be estimated.
Guo Shoujing has made a series of improvements to the standard meter and solved a series of problems. Naturally, his observation work can be better than his predecessor's.
The improvement of standard tables in Guo Shoujing was probably completed in the summer of 1277. It has been used to measure the sun shadow this winter. Because of the urgent need for observation, the first high column was made of wood, and later it was cast of metal. Unfortunately, this watch has been destroyed for a long time, and now it can't be seen. Fortunately, there is also a masonry stargazing platform in Dengfeng County, Henan Province, the main part of which is the standard watch of Guo Shoujing. This watch is slightly different from most watches. It adapts to local conditions, uses one side of this high platform as a watch, and lays 36 huge stones under the platform to form a watch 10 feet long. The local people gave this standard a very heroic name, called "celestial ruler".
The improvement of the standard is only the first step for Guo Shoujing to start astronomical work, and there will be more inventions in the future! Now let's talk about his improvement of the armillary sphere.
The armillary sphere was invented by astronomers in China in the second century BC at the latest, and it has been developed since the Tang and Song Dynasties. Its structure is completely modeled after the spinning celestial sphere reflected in people's minds at that time. There are many rings in this sphere, one weight covers the other. Some of these rings can rotate and some can't. In the middle of these overlapping rings is a slender tube called a peephole. Aim this thin tube at a planet. From these rings, we can infer the position of the planet in the sky. Because this instrument looks like a ball, it is called an armillary sphere. This is an outstanding creation of ancient astronomical instruments in China. In Europe, it was not until about16th century that there was an instrument as fine as China's Northern Song Dynasty armillary sphere.
However, the structure of this armillary sphere also has great shortcomings. The space of a ball is very limited. There are seven or eight rings in it, one ring inside the other, which covers many sky areas and narrows the observation range of the instrument. This is the first major shortcoming. In addition, several rings have their own scales, and the reading system is very complicated, which brings inconvenience to observers. This is the second biggest disadvantage. Guo Shoujing has made great improvements in view of these shortcomings.
Guo Shoujing's main idea of improving the armillary sphere is to simplify the structure. He intends to omit some of the rings so as not to block each other and hinder observation. At that time, spherics's calculation had been invented in mathematics, and the degrees of the running positions of some stars could be obtained through mathematical calculation, so there was no need to install a ring in this armillary sphere for direct observation. It is possible to realize Guo Shoujing's idea of omitting some rings in the armillary sphere.
Guo Shoujing only kept the two most important and necessary ring systems in the armillary sphere; And separate a group of ring systems and change them into another independent instrument; Completely cancel the loop of other systems. This fundamentally changed the structure of the armillary sphere. Then all the rings originally covered as fixed brackets are removed, and a set of main ring system left on this instrument is supported by a pair of arched columns and four other columns. In this way, the ring flew in all directions and there was nothing to hide. Compared with the original armillary sphere, this structure is really practical and simple, so it is named "Jane Instrument". This structure of Jane's instrument is basically consistent with the structure of modern so-called "sky schema telescope". In Europe, astronomical instruments of this structure did not spread from England until after18th century.
The scale division of Guo Shoujing bamboo musical instruments is also unprecedented fine. In the past, instruments could only read 1/4 once, while simple instruments could read 1/36 once, which improved the accuracy a lot. This musical instrument was preserved until the early Qing Dynasty, but it was later destroyed by Ji Lian, a French missionary who worked in Qin Tian Jian Prison. Now there is only one copy of the Ming Dynasty (1436 ~ 1449) which is kept in Nanjing Purple Mountain Observatory.
Guo Shoujing made many precise observations with this simple instrument, two of which were of great significance to the compilation of the new calendar.
One is to determine the intersection angle between the ecliptic and the equator. The equator refers to the equator of the celestial sphere. The earth hangs on the celestial sphere. Imagine that the equatorial plane of the earth extends around and cuts into a big circle with the edge of the celestial sphere. This circle is the celestial equator. The ecliptic is a great circle formed by the earth's orbital plane extending around the sun and intersecting with the celestial sphere. The intersection of the ecliptic and the equator on the celestial sphere. Is the angle between the equatorial plane of the earth and the orbital plane of the earth. This is a basic astronomical constant. This value has been determined to be 24, 1000 since the Han Dynasty, and no one has doubted it for many years. In fact, this intersection angle is shrinking every year, but the annual reduction is very small, only half a second, and I don't think it will be in the short term. However, although it has not changed much, it will still have an impact after accumulating 1000 years. The accuracy of the intersection angle between yellow and equator is closely related to the accuracy of other calculation results. Therefore, Guo Shoujing first investigated the data that had been used for thousands of years. Sure enough, according to his actual measurement, the angle between yellow and equator at that time was only 23 90'. This is a figure calculated by the ancient angular system. In ancient times, the whole circumference was divided into 1365 degrees, and 1 degree was divided into 100 minutes. Thus, the angle is 23 90'. It is changed into a modern universal 360 system, that is, 23 33 ′ 23 ″ .3. According to modern astronomical theory, the intersection angle at that time should actually be 23 31'58 ".0. Actually, the angular error measured by Guo Shoujing is1'25 ".3. But this kind of observation, in the era of Guo Shoujing, is valuable.
Another observation is the measurement of 28-night distance. In ancient China, when measuring the distance between constellations of 28 stars, a star was often designated as a sign, which was called "distance star". Because the distance star is used as a sign, the position of the distance star itself must be set accurately. The distance between this distance star and the next distance star is called "distance" This distance can determine the relative position between two distant stars. From the Han Dynasty to the Northern Song Dynasty, the distance between twenty-eight lodging houses was measured five times. Their accuracy is gradually improving. During the last observation in Chongning, Song Huizong (1102 ~1106), the average error of these 28 distance values was 0. 15, which was 9 ′. When he arrived in Guo Shoujing, the average error of the data he measured was only 4'.5, which was half that of the Chongning period. This is also a very rare achievement.
When compiling the new calendar, Guo Shoujing provided a lot of accurate data, which is indeed an important reason for the success of the new calendar.
In the process of changing the calendar, Guo Shoujing created nearly 20 kinds of instruments and tools. Here is another original musical instrument created by Guo Shoujing to see his technical achievements.
This musical instrument is a hollow hemispherical surface made of copper, shaped like a pot lying face up. It's called "Yang Yi". The mouth of the hemisphere is engraved with the directions of east, west, north and south. A small board is supported on the mouth of the hemisphere with two vertical and horizontal rods, and a small hole is opened on the board. The hole is located right in the center of the hemisphere. Sunlight passes through the small hole, casts a circular image on the sphere, and reflects on the carved grid, so that the position of the sun on the celestial sphere can be read immediately. People can avoid staring at the sun itself with their eyes and know the position of the sun, which is very clever. Even better, in the event of a solar eclipse, the sun image on the mirror will be correspondingly missing. In this way, you can directly observe the direction of solar eclipse, the number of deficient parts and the time of various solar eclipses from the supine instrument. Although Islamic astronomers have observed solar eclipses in ancient times by using the phenomenon of sunlight imaging through small holes, they only observed solar eclipses with a perforated board to help determine the time of various solar eclipses. No instrument can read data directly like Yang Yi.
Wang Xun and Guo Shoujing cooperated with a Nepalese architect, Brother Ani, to build a new observatory in Dadu, and those astronomical instruments created by Guo Shoujing were put on the stage. This was one of the best-equipped observatories in the world at that time.
Due to Guo Shoujing's suggestion, Yuan Shizu sent 14 astronomers to 26 locations in China at that time (mostly not counting) to make several important astronomical observations. At six locations, the length of surface shadow and the length of day and night from summer solstice were measured. These observations provide scientific data for compiling calendars suitable for the whole country. The scale of this astronomical observation is also rare in the history of world astronomy.
Through the collective efforts of Wang Xun, Guo Shoujing and others, the new calendar was published in the spring of 1280 (the seventeenth year from Yuan Shizu to Yuan Dynasty). According to the ancient motto of "respecting the people", it was named "time calendar". In the winter of the same year, the calendar for the next year calculated according to the service calendar was officially promulgated.
1294 rose to imperial academy. But about water conservancy work, the government at that time often asked him.
1298 (the second year of Yuan Chengzong Dade), the government decided to open a canal near Shangdu, and Yuan Chengzong summoned Guo Shoujing to discuss it. Guo Shoujing went to the local area to survey the terrain and learn about the rainfall. He found the river close to the mountain. Although the annual rainfall in the passing area is not much, it is very concentrated. When it rains for several days, the mountain torrents are fierce. He believes that even if the river flow is not large at ordinary times, the river itself must be fifty or seventy steps wide. At that time, the official in charge of this matter was short-sighted, thinking that Guo Shoujing overestimated the rainy season discharge and handled it too cautiously, and even reduced the width set by Guo Shoujing by 1/3. The year after the canal was opened, when it rained heavily, mountain torrents flowed down the river, and the river was too narrow to stop the flood. The banks of the river were flooded, and countless people, livestock and tents were lost, which almost destroyed Yuan Chengzong's palace. When Yuan Chengzong was forced to move northward to avoid water, he remembered Guo Shoujing's prediction last year and could not help sighing to the left and right: "Master Guo is really a man of god. Unfortunately, I didn't listen to him! "
From then on, Guo Shoujing became more famous. 1303, Yuan Chengzong wrote that all officials who have reached the age of 70 can retire, and Guo Shoujing is the only one, because the court still has a lot of work to rely on him, and he is not allowed to retire.
After Yuan Chengzong, the Yuan regime quickly decayed, the internal struggle of the ruling group became increasingly fierce, and the life was extravagant and absurd to the extreme, completely abandoning the positive factors that encouraged agriculture and mulberry in the Yuan Shizu era. In this case, Guo Shoujing's creative activities are naturally greatly restricted. Compared with his rising fame at that time, his creative activities in his later years were inevitably too quiet. Except for the construction of an astronomical instrument-Lingtai Water Soul in 1298, there are no other major creations and remarkable achievements.
It is conceivable that if he had better social and political conditions in his later years, he might have made greater contributions.
13 16 (three years in Yuan Renzong) Guo Shoujing, who worked hard for the scientific cause of the motherland for more than 60 years, died at the age of 86.
In memory of him, the main street in Xingtai City was named "Guo Shoujing Street".