What did ancient astronomers mainly do?

After reading the life stories of two famous astronomers, we can know what they are mainly doing.

Zu Chongzhi, also known as Fan Yang (now Laiyuan, Hebei Province) was born in Kuaixian County. Born in 429 A.D. in Jiankang (now Nanjing, Jiangsu), he was an official family. Although he was originally from the north, several generations of ancestors were officials in Jiangnan and were familiar with the calendar. My grandfather is in charge of civil engineering construction, and my father is also knowledgeable. He had the opportunity to receive scientific knowledge from his family since he was a child. When he was young, he entered Hualin University, which specializes in academic research. Zu Chongzhi once worked as a state official, joined the army, served as a county magistrate, from the highest official to a captain in Changshui, and enjoyed four salaries. He died in 500 AD.

Zu Chongzhi was a great mathematician and astronomer in ancient China. His life's works are varied. Unfortunately, all the books on mathematics have been lost. In all kinds of book catalogues at home and abroad, we can see that the titles of his mathematical works are "Composition" 6 volumes, "Notes on Nine Chapters of Arithmetic Meaning" 9 volumes and "Notes on Heavy Difference" 1 volume respectively. In astronomical calendar, he compiled Da Ming Calendar and wrote a refutation for Da Ming Calendar. In the annotation of ancient books, Zu Chongzhi has such works as The Book of Changes, Lao Zi Yi, Zhuangzi Yi, The Analects of Confucius and The Interpretation of Filial Piety, but they are all lost. In terms of literary works, he wrote 10 volume "Telling Different Stories", and fragments of this work can be seen in books such as "Taiping Magnolia".

Zu Chongzhi was interested in astronomy and mathematics since he was a child. He collected almost all kinds of documents, records and materials from ancient times to his life for research, and personally made accurate measurements and careful calculations. As he himself said, "measure your feet, bow detector, do your best, make a decision before you move." He carefully studied the work of scientists such as Liu Xin, Zhang Heng, Zheng Xuan, Kan Yi, Wang Fan and Liu Hui, refuted their mistakes one by one, and obtained many valuable results. A well-known example is the value of garden rate, which is accurate to 7 digits.

The calculation of garden rate π shows the mathematical level of a country and a nation. In ancient China, like any other countries and regions with earlier cultural development in the world, the earliest rate of people using gardening was 3. This value with great error has been used until the Han Dynasty. After entering the Han Dynasty, the improvement of garden rate attracted the attention of many scientists, who all did some work. The most important is Liu Hui, a mathematician in Wei and Jin Dynasties. He used "gardening" to calculate the gardening rate as 3. 14.

Regarding Zu Chongzhi's work on the rate of garden completion, its historical materials can only be found in the records of Sui Shu's Law, and Zu Chongzhi also gives two approximate fractional values of the rate of garden completion:

Security rate: π=355/ 1 13, with 6 digits after the decimal point accurate,

Approximation rate: π=22/7, accurate to 2 decimal places.

In Europe, the calculated value after 1 100 years is 355/13, which is called "Anthonis rate". 19 12 years, Japanese mathematician Masao Sanshi proposed that π=355/ 1 13 was called "ancestral rate".

It is a great pity that there is no historical record about how Zu Chongzhi calculated such an accurate result. But judging from the situation at that time, Zu Chongzhi still used Liu Hui's Horticulture. If so, Zu Chongzhi needs to calculate the area of the regular 12288 polygon and the regular 24576 polygon in the garden. You need to add, subtract, multiply, divide, square root and other operations for more than 130 times, and each operation must be accurate to 9 digits. It is conceivable that in those days, it took great care and superhuman perseverance to calculate by listing. The calculation of sphere volume is another great achievement of Zu Chongzhi and his son (Rihuan) in mathematics. Grandfather got the formula of sphere volume according to Liu Hui's correct method in "Nine Chapters Arithmetic Note".

Sphere volume =4/3πγ3.

Grandfather summed up the so-called "Zu's principle" in the process of deducing the formula of sphere volume. In the west, this principle is called "cavalieri's principle", but its discoverer, Italian mathematician cavalieri (1598 ~ 1647), was many years later than his grandfather.

Zu Chongzhi's achievements in astronomical calendar are mostly contained in his Da Ming Calendar and his Refutation for Da Ming Calendar. Through precise observation and measurement, Zu Chongzhi found many mistakes in the Yuan Kerry Calendar compiled by the famous astronomer He Chengtian, so he set out to compile the Daming Calendar, which was compiled in 462 AD at the age of 33. Zu Chongzhi made many creative contributions to the compilation of calendars. Daming Calendar is the best calendar in this era, but it was opposed by court courtiers. It was not until 10 year after Zu Chongzhi's death that Daming Calendar was officially promulgated due to the insistence of his son (Rihuan) and the textual research on the actual astronomical phenomena.

About 1800 years ago, in the Eastern Han Dynasty (AD 1 17), a large astronomical instrument driven by water was successfully manufactured in Luoyang, Kyoto, Eastern Han Dynasty. Twenty years later (A.D. 138), another instrument installed in Luoyang, Kyoto, "Houfeng Seismograph", accurately reported earthquakes thousands of miles away in the west. This marks the beginning of a new era of human recording and studying earthquakes with instruments.

The inventors of these two famous instruments were Zhang Heng, a great scientist and writer in the Eastern Han Dynasty. Zhang Heng made outstanding contributions to ancient astronomy, seismology and mechanics in China. It is said that he also made a south guide car and a drum car in his memory. Because of its high level of mechanical manufacturing, it is honored as "Wood Sage".

Zhang Heng's life

Zhang Heng, whose real name is Zhang Dijian, was born in Shiqiao, E County, Nanyang County (now Shili Shiqiao, north of Nanyang City, Henan Province) in a ruined bureaucratic family for three years (AD 78). Grandfather Zhang Kan is a local official, who was once the prefect of Shu County and the prefect of Yuyang. When Zhang Heng was young, his family had declined, and sometimes he had to rely on relatives and friends for help. It was this poor life that enabled him to get in touch with the working people in the lower class and some production and life realities, which brought positive influence to his later scientific creation.

At that time, Nanyang was an economically and culturally developed area, known as the "Southern Capital". Influenced by such an environment, Zhang Heng, who was diligent and eager to learn since childhood, laid a good foundation for later arts and sciences in his youth.

Because the classics at home can't satisfy Zhang Heng's thirst for knowledge, he left his hometown to study and make friends with literati and celebrities since he was sixteen. He has been to Chang 'an, the old capital of the Han Dynasty, visited local places of interest, and inspected the surrounding mountains, rivers, products, customs and human feelings. Later, he went to Luoyang, then the capital, to study in imperial academy, the highest institution of higher learning. Become a more knowledgeable scholar. At that time, the local government recommended him to be a "dutiful son", and the government repeatedly invited him to be an official, but he refused.

Zhang Heng has a special hobby and research on literature since childhood. His literary works are many and have different styles. Some forms are short and lyrical, such as Return to Talent. Some are magnificent and have a wide range of scenery, such as "Erjing Fu"; Some features are outstanding and unique, such as "four mourning poems" and "simultaneous songs".

In the 12th year of Yongyuan (A.D. 100), 23-year-old Zhang Heng was invited to return to his hometown to be the master book of Nanyang Taishou Baode, in charge of paperwork. In addition to dealing with government affairs, he also devoted himself to literary creation. Based on his experience of studying in Chang 'an and Luoyang, he carefully carved and revised it in ten years. In the first year of Ernst & Young (A.D. 107), he wrote the famous Ode to Tokyo and Ode to Xijing, which were collectively called Ode to Erjing, which was widely circulated among the people and well painted.

Later, Baode was transferred, and Zhang Heng resigned and went home. In order to win over the scholars, Deng Zhi, the imperial relative in charge of state affairs, sent someone to ask Zhang Heng to be his staff several times to strengthen his faction. However, on the one hand, Zhang Heng disliked the exclusive rights of consorts, on the other hand, he wanted to concentrate on his studies and was resolutely rejected.

When Zhang Heng was thirty-four, his research interests gradually turned to philosophy and natural science. He likes Yang Xiong's philosophical work Xuan Jing very much. The contents of Taixuan Jing involve astronomy, calendar, mathematics, etc., which aroused his great interest. Some simple materialistic views in Xuan Jing also greatly inspired Zhang Heng.

In the fourth year of Andiyong (AD 1 1 1), Zhang Heng was recruited to Beijing, and successively held low-and middle-level official positions such as Langzhong, Taishiling and Bussimaling. Among them, he served as Taishiling for the longest time, reaching fourteen years before and after. Taishiling is an official who is responsible for observing astronomical phenomena, compiling calendars, waiting for the weather, and adjusting the clock rhythm (measurement and temperament). During his tenure, he made a superb study of astronomical calendars and made great contributions.

There are three theories about celestial movement and cosmic structure in Han Dynasty: Gaitian theory, Huntian theory and Michelle Ye theory. The theory of covering the sky, also known as the sky is round like an umbrella and the place is like a chessboard. Huntian said that the shape of heaven and earth is like an egg, and the relationship between heaven and earth is like an eggshell wrapped with egg yolk; Michelle Ye said that the sky has no certain shape, and the sun, moon and five stars (gold, wood, water, fire and earth) all float in the gas.

According to his own understanding and actual observation of celestial bodies, Zhang Heng carefully studied these three theories and thought that Huntian theory was more in line with actual observation. He inherited and developed the previous theory of Huntian, and boldly put forward many new ideas about astronomical phenomena.

On the basis of the armillary sphere invented by Geng Shouchang in the Western Han Dynasty, Zhang Heng created a more accurate and comprehensive armillary sphere according to his own armillary sphere theory. Created a "armillary sphere" that can accurately implement the thought of armillary sphere.

The armillary sphere is a rotatable hollow copper ball. The surface of the copper ball is engraved with the positions of 28 constellations and other constant stars; There is an iron shaft running through the center of the ball, and the two ends of the shaft symbolize the North Pole and the South Pole. There are several copper circles outside the sphere, which represent the horizon circle, meridian circle circle, ecliptic circle and equatorial circle. Twenty-four solar terms are engraved on the equator and the ecliptic. All the important astronomical phenomena that Zhang Heng knew at that time were engraved on the armillary sphere.

In order to make the "armillary sphere" rotate automatically, Zhang Heng used the principle of hydraulic transmission gear to drive the hollow copper ball to rotate around the shaft by using the hydraulic transmission gear dripping from the drip pot. The speed at which a copper ball rotates once is equal to that of the earth. In this way, people sitting in the room can see the movement of celestial bodies from the armillary sphere.

From 89 to 140, there were 33 earthquakes in Luoyang and Longxi, the capitals of the Eastern Han Dynasty. Especially in A.D. 1 19, two major earthquakes occurred in Luoyang and other areas, which prompted Zhang Heng to step up his research on earthquakes. Finally, in A.D. 132, he invented and manufactured the first seismograph in China.

This seismograph made by Zhang Heng is quite sensitive and accurate. One day in A.D. 138, the seismograph accurately detected an earthquake in Longxi, which was more than 0/000 miles away from Luoyang/KLOC-0, indicating that its accuracy reached a quite high level. Europe made a similar seismograph in 1880, which was later than Zhang Heng 1700 years.

In meteorology, Zhang Heng also created an instrument for measuring wind direction-Hou Fengyi, also known as the bronze bird with the wind. A copper bird with a flower in its mouth was placed at the top of a 50-foot-high pole, which could rotate with the wind. The direction of the bird's head is the wind. This instrument is similar to the chicken waiting instrument installed on the roof in Europe, but it didn't appear until the 12th century, which was later than Zhang Heng's chicken waiting instrument 1000.

Zhang Heng made outstanding contributions to China's scientific and cultural undertakings all his life, and was one of the great scientists in ancient China. He is modest, cautious and diligent. "Like the passing of Sichuan, I will never give up day and night", which has been like a day for decades, has demonstrated the academic style of being meticulous, striving for perfection, not afraid of power and forging ahead. And his noble character of not seeking fame and fortune is worth learning.

In the 4th year of Yonghe (AD 139), Zhang Heng requested to retire and was not allowed to return to his hometown. He was transferred to North Korea to be a minister of state affairs, but he died only one year later at the age of 6 1.

Lingxian

Lingyi is the most famous astronomical work of Zhang Heng's life. This is an astronomical theoretical work that expounds the formation and movement of the sky, the earth, the sun, the moon and the stars, and represents the achievements of Zhang Heng's astronomical research. It summed up the astronomical knowledge at that time, and although there were some mistakes, it still put forward many advanced scientific ideas and original opinions.

For example, when Zhang Heng expounded the theory of Huntian, although he still retained the old concept of horizon and increased the diameter of the celestial sphere, he further made it clear that there was room outside the celestial sphere. He said: "Those who have passed away don't know, and they don't know. I don't know, I don't know, the universe is also called. The list of the rest is infinite, and the end of the universe is infinite. " In other words, the space we can observe is limited, and the place we can't observe is an endless universe with no beginning and no end. This passage clearly puts forward the view that the universe is endless in time and space, which is very valuable.

Zhang Heng pointed out in Lingxian that the moon itself does not shine, and moonlight is reflected sunlight. He said: "the husband is like water, the fire is light outside, and the water contains scenery." Therefore, the moonlight was born in the sun, and the soul was born in the sun; On that day, the light was full, and on that day, the light was exhausted "(the scene is the shadow, and the spirit refers to the part that lacks the moon). He vividly compared the sun and the moon to fire and water. Fire can shine and water can reflect light. He pointed out that moonlight is produced by sunlight, and sometimes it is invisible because sunlight is blocked. His views were very fresh and correct at that time.

At the same time, Zhang Heng further explained the cause of the eclipse. He said: "The sun is rushing, the light is often inconsistent, and it is hidden underground, which is called darkness." Among the stars, the stars are very small, and they eat when they meet the moon. "When you look at the moon, you should be able to see the full moon, but sometimes you can't, because the sun is covered by the earth. He called the dark part of the earth's shadow "dark sky", and an eclipse would occur when the moon passed through the "dark sky", and brilliantly expounded the principle of the eclipse. As for the phrase "among the stars, the stars are faint", it means that the stars disappear when they encounter "darkness".

Now it seems that this statement is not correct. Because stars are very far away from the earth, and most of them are luminous stars, unlike the moon, which belongs to planets, so there will be no stars entering the shadow of the earth and losing their light. This is Zhang Heng's short board. It can also be seen that the research of the ancients at that time could not be perfect. People are the same now. Nothing can be absolutely right, but we must reflect the objective reality to the greatest extent.

In addition, Zhang Heng also calculated the angular diameters of the sun and the moon in Lingxian County, and recorded more than 2,500 stars observed in Luoyang, Central China, including 24 regular stars 124 and about 320 stars with names. This is very close to the results observed by modern astronomers.

In another astronomical work by Zhang Heng, The Legend of the Armageddon, it is also determined that the time required for the earth to go around the sun is "365 degrees, one quarter on Sunday", which is very close to the figure of 365 days, 5 hours, 48 minutes and 46 seconds measured by modern astronomers, indicating that Zhang Heng's research on astronomy has reached a relatively high level.