Zhang Heng is one of the representatives of Huntian theory in the middle of Eastern Han Dynasty. He pointed out that the moon itself does not shine, and moonlight is actually a reflection of the sun's light; He also correctly explained the cause of the solar eclipse and realized the infinity of the universe and the relationship between the speed of planetary motion and the distance from the earth.
Zhang Heng observed and recorded 2,500 stars, created the world's first leaky ball that can accurately perform astronomical phenomena, the first instrument to test earthquakes-the waiting wind seismograph, and also made a South Locomotive, an automatic drum car, a wooden bird flying to Wan Li and so on.
Zhang Heng * * * is the author of 32 scientific, philosophical and literary works, among which astronomical works include Ling Xian and Ling Xian Tu.
In order to commemorate Zhang Heng's achievements, people named a crater on the back of the moon as "Zhang Heng Crater" and the asteroid 1802 as "Zhang Heng Asteroid".
Guo Moruo, a famous writer and historian in China in the 20th century, commented on Zhang Heng: "Such an all-round development figure is rare in world history, and it has been admirable for thousands of years."
Later people called Zhang Heng a wooden saint.
[Edit this paragraph] Biography of historical books
Zhang Hengchuan (from Ye Fan in the Later Han Dynasty)
Original text:
Zhang Heng, a native of Nanyang. Hengshan Mountain belongs to the literature and swims in the third auxiliary. Because when I entered the capital, I saw imperial academy, learned the Five Classics and thoroughly understood the Six Arts. Although only above the world, there is no arrogance. Often calm and quiet, it is not easy to make friends. In Yongyuan, filial piety is not good, and even building a house is not good. The world is long, and since the princes are wasted. Heng Nai designated Ban Gu's Er Du Fu as Er Du Fu because of its satirical admonition. If you think about it carefully, you will succeed in ten years. General Deng Zhi is so talented that he shouldn't be called when he is tired.
Well-balanced and smart, especially thinking about astronomical yin and yang calendar calculation. Andy heard about Hengshan's medical skills and the characteristics of bus worshipping doctors, so he moved to Taishiling. So he studied Yin and Yang, made a wonderful machine, made an armillary sphere, and wrote Lingxian and Analects of Confucius, which were very detailed.
Beginning in Shun Di, it was restored to Taishiling. I don't want to live in the present era, but the officials I live in have accumulated a good place and pushed me to Troy, where the balcony is pleasant and the environment is elegant, and the railway has not moved for many years. It has been five years since I left my post as a historian.
In the first year of Yangjia, the seismograph after the wind was rebuilt. It is made of copper and has a diameter of eight feet. It is covered and raised in the shape of a wine statue, a turtle decorated with seal script, a bird and a beast. All of them are pillars, eight-way, and the engine is turned off. There are eight dragons outside. The first one is a copper pill, and the next one is a toad. Open your mouth and accept it. Its teeth are cleverly made, all hidden in respect, and its coverage is endless. If there is an earthquake, the statue will shake the dragon, the machine will spit out pills and the toad will hold it. The vibration was so exciting that the waiters noticed it. Although Yilong started the engine, Qige didn't move, and the air was full of places that knew about the earthquake. Test it with something, it is like a god. Since it is recorded in the book, there is nothing left. After tasting the opportunity of Yi Long, I didn't know its meaning, and the scholars in the capital blamed it for its lack of levy. A few days later, the post arrived, and there was an earthquake in Longxi. Everyone was convinced. Since then, it has made historians remember what to do.
When political affairs are gradually damaged and power moves to the lower level, the balance is based on the past. ……
At the beginning, he was good at martial arts and described the ancestors of Xian Zong and Su Zongyin. Since ZTE, the Confucians have been fighting for the exotic and the beautiful, and the knowledge of map latitude and longitude has been accompanied by vicious words. Balance is illusory, not a saint's law, but a sparse law. ……
After moving clothes, the emperor led the way and satirized the discussion. Ask those sick and evil people in the world. Eunuchs are afraid of their own destruction, and they all see it in their eyes, and the scales are specious. I'm afraid I'll be castrated eventually, so I swear.
Always thinking about the body, thinking that good or bad depends on the body, which is difficult to understand. It was written as "Fu Xuan" to express feelings. (Introduction of the Company)
At the beginning of Yonghe, it was a river phase. At that time, the king was arrogant and disobeyed the constitution; How arrogant, * * * is not good. Weigh the car, rule the majesty, improve the statutes, know the name of the traitor by Yin, and gather birds for a while, which is called politics. For three years, I have written to beg for bones and worship ministers. In sixty-two, Yonghe died in four years.
When Cui Yuan wrote the exegesis of Zhou Guan, he thought that he could not be different from other Confucianism. Those who want to say that "Xun" and "Xiang" are incomplete according to Confucius' Book of Changes can't do it. There are 32 poems, including Fu, Ming, Seven-character poems, Lingxian poems, Yingxian poems, Seven-sided poems, poems and drawings. 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. Zhang Heng is one of the representatives of Huntian theory in the middle of Eastern Han Dynasty. He pointed out that the moon itself does not shine, and moonlight is actually a reflection of the sun's light; He also correctly explained the cause of the solar eclipse and realized the infinity of the universe and the relationship between the speed of planetary motion and the distance from the earth.
[Edit this paragraph] The life of the character
Zhang Heng was born in a famous family. His grandfather, Zhang Kan, was called a holy boy since childhood, and once gave his nephew a family heirloom worth millions. After Emperor Guangwu acceded to the throne, he recommended Zhang Kan to worship the official. Gongsun Shu used to be the prefect of Shu County, and together with Fu Han, he crusaded against Shu County and made great contributions. Later, he led the troops to crusade against the Huns and worshipped Yuyang (now near Beijing) as the satrap. Thousands of cavalry used to break the Huns' attack. Since then, during his tenure, the Huns have never dared to intrude. He also taught the people to farm and cultivated 8000 hectares of rice fields, which made the people rich. Therefore, some folk songs praised him, saying that "Junwei Zhang politics was overjoyed" and Zhang Kan was an honest official. When attacking Shu, he was the first to attack Chengdu, but he got nothing from the mountains of treasures left by Gongsun Shu. Shu County is known as Tianfu, but when Zhang Kan was transferred from the magistrate of Shu County, he took an old car with only a roll of cloth and a quilt.
Like his grandfather, Zhang Heng studied hard since childhood and was very literary. /kloc-left home to study abroad after 0/6. He first went to the then academic and cultural center Sanfu (now Xi, Shaanxi). The magnificent mountains and rivers in this area and the magnificent ruins of the ancient capital of Qin and Han dynasties provided him with rich literary creation materials. Later, he went to Luoyang, the capital of the Eastern Han Dynasty. There, he went to imperial academy, the highest institution of learning at that time, met Cui Yuan, a young scholar, and became close friends with him. Cui Yuan was a student of Jia Kui, a scholar and astronomer at that time. He was also proficient in astronomy, calendar and mathematics. In the 12th year of Yongyuan (A.D. 100), Zhang Heng was asked by Baode, the magistrate of Nanyang, to be the master book, in charge of clerical work. Eight years later, Baode was transferred to the capital and Zhang Heng resigned to live at home. During his stay in Nanyang, he devoted himself to astronomy, Yin and Yang, calendar calculation, etc., and repeatedly studied Xuan Jing by Yang Xiong in the Western Han Dynasty. His fame in these aspects attracted the attention of Emperor Wu of the Han Dynasty. In the fifth year of Yongchuan (A.D.11), Zhang Heng was called to Beijing and became a doctor.
In the first year of Yuan Dynasty (A.D. 1 14), the merchants moved. The following year, I moved to Taishi Order. Later, he was transferred to other posts, but five years later, he was reinstated as Taishiling. In short, he held this position for 14 years, and many important scientific research work of Zhang Heng was completed during this period. In the second year of Yangjia in Shun Di (AD 133), he was promoted to assistant middle school. However, he was soon slandered by eunuchs. In the first year of Yu Yonghe (A.D. 136), he was transferred to Beijing as the photograph of Hejian Wang Liu Zheng. Liu is an arrogant and extravagant person who does not abide by the central code. Many local strongmen violate the law with him. After Zhang Heng took office, he was strict in law and discipline and cracked down on the strongmen, which made everyone respect him. Three years later, he asked Shun Di to retire, but the court made him an official. This is a bit strange, because the official position of Shangshu is much lower than that of Shi Zhong or Xiang, and it is not clear in history whether he applies or not. This year (Yonghe four years, that is, AD 139), he died.
[Edit this paragraph] Academic achievements
Zhang Heng is a versatile scientist. His achievements involve astronomy, seismology, mechanical technology, mathematics, literature and art and many other fields.
Zhang Heng has two most important jobs in astronomy-writing spiritual lines and making armillary sphere. In addition, the calendar was studied.
Lingxian is Zhang Heng's masterpiece on astronomy, which fully embodies Zhang Heng's achievements and development in astronomy. The original text was quoted by Liu Zhao in the Book of the Later Han Dynasty and passed down from generation to generation. The main points of astronomy introduced in this paper are as follows:
(1) The origin of the universe. Lingxian believes that the universe is an invisible and colorless yin essence, quiet and lonely. This is a long stage called "I". This stage is the root of Tao. From Doggett's root, the trunk is produced and the gas is colored. But "chaos does not distinguish", you can't see any shape, and you can't measure its moving speed. This gas is called "Tai Su". This is another long stage, called "Pang Hong". With the trunk, objects begin to come into being. At this time, "the vitality is judged, just divided, turbid, sex is outside, and the ground is inside." The cooperation between heaven and earth produces everything. This stage is called "Tai Xuan", which is the reality of Tao. Lingxian called the three stages of the evolution of the universe "Daogen", "Daogan" and "Daoshi". When explaining the chaotic Tai Su Qi, I quoted a sentence from the Tao Te Ching: "Things are born in harmony, and they are born naturally." All these explain the concept of the origin of the universe in Lingxian, which originated from Laozi's Taoist philosophy. The theory of the origin of the universe in Lingxian is very similar to that in Huainanzi Astronomical Training, but Huainanzi thinks that after the qi is clear and turbid, "those who clear the yang are sparse and those who are heavy and turbid are stagnant." Heaven and earth, Gaitian said so. Lingxian advocates that the sky made by pure gas is outside, and the land made by turbid gas is inside. This is the saying of Huntian.
In a word, Zhang Heng inherited and developed China's ancient ideological tradition, thinking that the universe is not inherently perfect, but has a process of emergence and evolution. The ideological tradition represented by Zhang Heng is quite different from the ancient western ideological tradition that the structure of the universe is eternal, but it is similar to the spirit of modern universe evolution theory.
(2) About the infinity of the universe. During the Warring States period, the definition of "corpse" was as follows: "Up and down in all directions, talk about the universe, talk about ancient and modern times." Space is space and the universe is time. China's traditional thought is to connect space and time. This is also very different from the concept of treating them as two independent concepts in ancient western countries. However, China, like the West, has been debating whether they are finite or infinite. There is a saying in Zhuangzi that the universe is infinite in space and time. At the end of the Western Han Dynasty, Yang Xiong thought that "closing the sky for the universe and opening the sky for the universe" had a space limitation and a time starting point. Although Zhang Heng studied Yang Xiong's Taixuan Jing for a long time and was deeply influenced by Yang Xiong, he didn't want to follow Yang Xiong in the infinite universe. Lingxian believes that the size of the world seen by human eyes is limited, but beyond this range, people will "don't know it and don't know it." 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. "The universe has no boundaries in space and no starting point in time. Yang Xiong's thought and the most famous Big Bang cosmology in astronomy are interlinked in the ultimate essence. But Zhang Heng's conclusion is consistent with contemporary dialectical materialism philosophy. It seems that the problem of finite universe will be debated for a long time.
(3) About the structure of heaven and earth. Lingxian describes the sky as the place where the stars are. It is an ellipsoid with minimal eccentricity: "The dimension of octupole is 232,300 li in diameter. The north and south are shortened by thousands of miles, and the east and west are widened by thousands of miles. If you wear it, you will be embarrassed. " There is a north pole in the sky, and the pivot star is in this position. The sun, the moon and five stars all revolve around it. There is also a south pole in the sky, which is invisible to people underground. The ground seen by human eyes is flat, in the center of the sky, "from the ground to the sky, half of the octupole;" Then the depth of the land is the same. " This shows that the land in Zhang Heng's mind is a hemisphere. On the ground, if the length of the sun shadow is measured at noon on the same day with an 8-foot-high watch, the difference between the length of the sun shadow measured at two locations thousands of miles apart from the north and the south is 1 inch.
Why do you think that heaven and earth are ellipsoid structures? We can't understand, perhaps, one possibility is that we are bound by tradition. As early as in Lu Chunqiu, it was mentioned that "within the four seas, things are 28,000 Li, and north and south are 26,000 Li", and things are 2,000 Li longer than north and south. These two values are also quoted in Huainanzi Wrestling Training. It can be seen that the ancients probably thought that things in heaven and earth were longer than things in the north and south.
Horizon theory and "the difference between surface and shadow is 1 inch" were once considered as the contents of Gaitian theory. However, it is not appropriate to think that the structure of heaven and earth in Lingxian covers the sky. The main difference between Huntian model and Gaitian model is that Huntian sky is spherical, which can turn to the ground. The sky has not only the North Pole from the ground, but also the South Pole hidden underground. The sky that covers the sky is either covered on the flat ground like a cover (recently called the first theory of covering the sky) or forms two parallel planes with the ground (recently called the second theory of covering the sky). In short, the sky is always above the ground. There is only the North Pole in the sky, and there can be no South Pole. Therefore, from the understanding of the structure of the sky, the spirit fairy can only be classified as the theory of muddy sky, but not as the theory of covering the sky. Regarding the land issue, it must be pointed out that the dispute over mud cover in history mainly lies in the sky, not the land. Until the Tang Dynasty and his party completely denied the old saying that the shadow of the sun 1 inch away, the concept of horizon still existed in Huntian Theory. Even after some quarrels, until the introduction of western astronomy, China still failed to establish a clear mathematical model of the spherical earth. On the contrary, the theory of "heaven is round and earth is flat" in Lingxian still occupies an important position.
(4) About the angular diameters of the sun and the moon. Lingxian records that the diameter of the sun and the moon is "one-seventh of the whole day". The modern universal angle unit is 29'2 1 ". According to Qian Baoyu's textual research, it is considered that "the diameter of (day and month) is one-seventh of the week of that day and one-half of the land width" in Lingxian should be corrected to "the diameter of (day and month) is one-third of the week of that day and one-third of the land width". Then the angular diameter of the sun and the moon should be 29' 35.3 "]. Compared with the daily and monthly average angular diameters of 31'59 "and 31'5" measured by modern astronomy, the error is only about 2'. According to the observation conditions two thousand years ago, Zhang Heng's measurement is accurate.
Zhang Heng also introduced an observation in his previous Weekly Parallel Calculations: an 8-foot-high pole stands vertically on the ground, and the shadow length of the pole is measured whenever the sun crosses the meridian. When the shadow is 6 feet long, watch the sun with an 8-foot-long bamboo tube with an aperture of 1 inch. Zhou Kuai and suan Jing think that the sun's visual circle at this time is just a circle of bamboo tubes. Therefore, according to the proportional relationship of "the difference of thousands of miles is 1 inch", it is concluded that the distance between the sun and human eyes at this time is 10 Wan Li, and the line diameter of the sun is 1250 Li. Because the basic starting points such as "the difference of a thousand miles 1 inch" are all wrong, the result of the book "Weekly Parallel Calculation" is extremely absurd (the diameter of the sun's line is actually1.39.5438+00,000 kilometers). As far as the observation itself is concerned, the results of Zhou Bi and Shu Jing are quite rough. According to the bamboo tube length of 8 feet and the diameter 1 inch, the solar angle diameter is 42 ′ 58 ″. The error is much larger than that of Lingxian County.
(5) The reasons for the eclipse. Before Zhang Heng, people already knew the cause of the solar eclipse. Liu Xiang once said in the Western Han Dynasty, "An eclipse will be covered by the moon" (see Kaiyuan Zhan Jing, Volume 9). Wang Chong of the Eastern Han Dynasty quoted others' more explicit statement in On the Balance of Days: "Or, the eclipse is also covered." The sun is above and the moon is below, which is blocked by the shape of the sun. "For the reason of the eclipse, Zhang Heng did not have a clear explanation before. Probably in view of this situation, Zhang Heng did not mention the cause of solar eclipse in Lingxian, but specifically discussed the cause of lunar eclipse: "Moon, light is born in the sun; Born in the sun. The day is full of light, the day is full of light. The stars are shining, because water becomes light. A day's rush, the light is often inconsistent, but also all over the ground, which is called virtual. In the stars, the moon will eat. "This passage, said the moon itself does not shine, the sun shines on the moon to produce a bright moon. The reason why the moon is in deficit is that it can't get sunlight. Therefore, when the moon is opposite to the sun, there will be a full moon. As the moon gets closer and closer to the sun, the moon's deficit is getting bigger and bigger, and finally it disappears completely. Such a theory of the moon phase has been roughly stated in the book Zhou Pian Shu Jing: "The sun shines on the moon, and the moonlight is born, so it becomes a bright moon. "Jing Fang in the Western Han Dynasty put it more clearly:" The former teacher thought that the sun was like a projectile and the moon was like a mirror; Or think that the moon is like a projectile, the sun is shining, and it is dark if it is not bright "(Volume 1 of Kaiyuan Zhan Jing). There is no essential difference between Zhang Heng's moon phase theory and theirs. What is outstanding is that Zhang Heng emphasizes the relationship between the moon phase and the relative position of the sun and the moon. But in this way, people naturally have to ask, since there is a "total solar eclipse", why is there sometimes a lunar eclipse on that day? In this regard, Zhang Heng replied: "Covered in the ground", that is, the earth blocked the sunlight, so that the sunlight could not reach the moon. Zhang Heng named the shadow produced by this land "virtual". When the moon enters the void, the eclipse occurs. The explanation of the eclipse in Lingxian is very scientific.
But if you think about it, people will ask questions again. According to the celestial structure of Lingxian, the earth is a semi-ellipsoid, and its lower part is in close contact with the celestial sphere. Then: (1) In order to make the sun and the moon sink into the ground level and move underground, the sun and the moon can only be two round surfaces without thickness, which is in contradiction with the moon phase theory mentioned above. (2) When the sun sinks below the horizon, the light will be completely blocked by the hemisphere and will not be projected on the moon at any time. In this way, the moon should always be invisible at night, so there is no eclipse at all. To explain these two contradictions, we can only think that the land in Lingxian has two different meanings. The first meaning is that the earth is a semi-ellipsoid relative to the sky. The second layer means a small solid hanging in the center of the celestial sphere relative to the sun and the moon. Or, we can unify these two meanings: a piece of land is hanging alone in the sky, and the other piece of land is full of water, so it can be closely combined with the lower part of the celestial sphere. In this understanding, the sun and the moon can still be a ball; But after the sun reaches the water surface, the sunlight can still penetrate the water surface and shine on the moon, and only that relatively small piece of land can produce void. Of course, when speculating in this way, it needs to be added that in Zhang Heng's view, water is a highly transparent substance, so the sunlight after going deep underground can still penetrate the thick water layer and shine on the moon, thus producing a bright moon.
(6) About the five-star movement. Lingxian put forward four extremely valuable opinions. First, the sun, the moon and the five stars are not on the spherical shell of the celestial sphere, but run between heaven and earth at different distances from the ground. Second, the seven celestial bodies move at different speeds. The speed near the ground is fast, and the speed away from the ground is slow. Thirdly, Lingxian explained why the planets have motion changes such as stopping, reversing, delaying and speeding with the power of heaven. It's late recently, but it's far away. If you do this, you will bend, if you bend, you will stay behind. If you stay back, you will violate it, it will be too late, and you will be forced by heaven. Fourth, five stars can be divided into two categories according to their distance from the ground and their running speed. A kind of lunar attachment, which belongs to Yin, includes Mercury and Venus. The other is attached to and belongs to the sun, including Mars, Jupiter and Saturn.
Four o'clock above Lingxian is very interesting. The first point can be said to be basically correct, although the actual situation is much more complicated than this generalization. The second point is exactly the same as that of the ancient Greeks. In China, Zhang Heng was not mentioned before, and nobody paid attention to it after, which greatly limited the development of ancient mathematical astronomy in China. Although the third point is vague and completely incorrect, it is obviously seeking to explain the mechanical reasons why planetary motion is backward and forward. This kind of effort itself is worth writing into the whole history of astronomy. More than 65,438+0,500 years later, Wang Xichan mentioned a similar idea in the Interpretation of the Five Elements, and further proposed that Heaven has a magnet-like force that attracts the needle to the sun, the moon and the five stars. The mechanism of Wang Xizhi's thought is clearer. Although the ideas of Zhang Heng and Wang Xichan are incorrect, the motion of the planet and its satellites (the moon is the satellite of the earth and the earth is the planet) is indeed governed by the law of universal gravitation. Therefore, it is undoubtedly a correct direction to investigate the mechanical reasons in the movement of these celestial bodies. In the west, there is still no discussion about this mechanical reason for more than 1000 years after Zhang Heng. Many great Greek astronomers only described the movements of the sun, the moon and the five stars in detail, but never tried to explain their mechanical reasons. The discussion of mechanical causes was put forward only after the scientific revolution began in16th century. The fourth point is also interesting. The classification of the planets of Lingxian is only the classification of the planets in the solar system and the planets outside. Of course, now we know that all planets, including the earth, revolve around the sun, while the moon revolves around the earth. Therefore, the statement of "attachment to the moon" is of course wrong. The reason for this mistake is that Zhang Heng, like other ancients, regarded the moon as the representative of Yin. However, from the movement of inner planets, gold and water, what people see is rarely completely different from that of outer planets. That is, exoplanets can only start a rendezvous cycle from the morning in the east. On the other hand, the inner planet can not only rise from the east in a rendezvous period, but also dim in the west like the moon. It is precisely because of this similarity that Lingxian put forward the idea that it is attached to the moon.
(7) about the star officer. The sky is full of stars. In order to identify and observe them, the ancients combined them into a group of stars. These constellations range from one star to dozens of stars. Such stars were called star officials by the ancients. Because astronomers have different methods of choice and combination, many different star official systems have been formed. By the time of Zhang Heng, the star official system spread all over the world, including the star official system represented by Records of the Historian Tianguanshu, the system of Shi, Gan, Huangdi and the system of "occupying the sea". Zhang Heng compared, sorted out and summarized these distinctive systems, and developed a new system with the largest number of stars. "Lingxian" records that "the total wisdom of Chinese and foreign officials is 24, which can be named as 320, which is 2,500 stars, but the proportion of sea people does not exist." Zhang Heng's arrangement of this star official system is more than 100 years earlier than the time when astronomer Chen Zhuo summarized the three-star officials of Gan, Shi and Hsien Wu, and it includes many more star officials and stars than Chen Zhuo (Chen Zhuo summarized 283 officials with 1464 stars), and its achievement is certainly greater than that of Chen Zhuo. Unfortunately, Zhang Hengxing's official system has been lost, which is a great loss in the history of stargazing in China.
One of the problems related to the official stars is that it is proposed in Lingxian that there is also a kind of "microsatellite" in the sky, that is, very weak stars, the number of which is 1 1520. Strictly speaking, this figure does not come from the actual measurement, but from the mysterious "number of everything" in the Book of Changes. The figures are of course incorrect. However, Zhang Heng believes that there are microsatellites, and the number is much more than that of bright stars, which is in line with objective reality.
(8) Meteors and meteorites. In the sky, except the sun, the moon and the stars. Stars including planets and stars are common members, and meteors and other celestial bodies are also seen from time to time. "Lingxian" holds that "and (according to: referring to the three light) decline, God rests, so there are meteorites. However, when the star falls, it will be a stone on the ground. " Here, Zhang Heng inherited the view of predecessors that "a star falls on the ground and is also a stone" (Historical Records of Heaven), and made a more correct explanation of the source of meteorites. At the same time, Zhang Heng also discussed the causes of meteorites, which were related to the decline of the sun, moon and stars. Although this idea is not correct (there are some large and small meteoroids in the solar system, which become meteors when they meet the earth in operation, and burn due to friction after entering the atmosphere; Large meteoroids fall to the ground and become meteorites before they burn out in the atmosphere, but every celestial body has a stage of "decline" and death, which is a very scientific conclusion. Zhang Heng's thought is dialectical, which is also lacking in ancient western astronomy.
Associated with meteorites is the explanation of the stars in Lingxian: "There are mountains on the ground to announce their qi and gather the stars. Stars are also born in the earth and refined in the sky. " This view that stars were born on the earth is of course completely wrong. It was a reflection of the thought of correspondence between heaven and earth that was popular for hundreds of years at that time. "Spirit Fairy" said: "It seems to be in the sky, and it seems to be underground. There are nine places in the sky and nine domains in the earth. There are three days in the sky and three shapes in the earth. Some images are effective and tangible. Different emotions, thin empathy, and natural life. " These so-called correspondence between heaven and earth are purely subjective and have no scientific connection in connotation. For example, the so-called land of nine days (that is, nine days as the ancients said) and the land of nine domains (that is, Kyushu) were artificially divided by ancient people in China. Therefore, this correspondence is purely digital coupling. However, the reason why Zhang Heng has the idea that the essence of mountains rises to stars is because all the meteors he sees are stones, and mountains are the place with the most stones. How can stones go to heaven? Therefore, it is inevitable that this is the essence of mountains, which can ascend to heaven and become stars. These reflect the view that meteorites come from outer space. In the west, until the17th century, there were still astronomers who believed that meteorites did not come from extraterrestrials.
As an excellent ancient astronomical work, Lingxian still has many shortcomings. In addition to the points mentioned above, for example, the myth of the Goddess Chang'e flying to the moon is recorded as a fact, and it is even said that Chang 'e became a toad after she entered the month. As for the various thoughts of astrology revealed in the article, it was the ethos of the whole era at that time, and it was not necessary to demand Zhang Heng. In a word, although Lingxian has some shortcomings, its significance in the history of astronomy is not inferior. Liu Zhao in the Liang Dynasty praised Zhang Heng as "the wonder of astronomy, the best in a generation", and one of the main bases of his evaluation was Lingxian, an outstanding work.
[Edit this paragraph] Making an armillary sphere
Zhang Heng's armillary sphere is a performance instrument to demonstrate the operation of celestial bodies. Its external outline has the image of a ball, which conforms to the theory of Huntian advocated by Zhang Heng, so it is named Huntian Instrument. This armillary sphere is recorded in three places in Jin Zhi. One is in the "Celestial Body" Festival, which quoted Ge Hong, a scientist in Jin Dynasty, as saying: "Zhang, as a bronze armillary sphere, turned it around in the secret room by leaking water, making the waiter close the door and ring. Waiting for his people to tell the sky watcher in GV: When Xuan Ji added, he first saw a star, and a star was in the middle. Today, a star is gone, all like a combination. " In the section of "instrument and image", there is a more specific description: "Zhang Heng is also an elephant. There are internal and external rules, north and south poles, and yellow equator. The 24th column, 28 nights, China and foreign officials and the sun, the moon and five latitudes. Turn it into the upper room of the temple by leaking water. In the stars, outside, it doesn't correspond to the sky. Because of its embarrassment, it turned to the Swiss wheel ■ pod under the steps. It was full and empty with the moon, and it opened and fell according to the calendar. " This is also called Hunxiang, which is a reflection of the nonstandard naming of early instruments. It does not mean that it is two different instruments of Hunxiang. The third place is at the end of the "elephant" body, talking about the size of Zhang Heng's armillary sphere: "The ancient elephant is divided into two parts, each week is seven feet, three inches and a half. Zhang Heng was restructured and divided into four parts, four feet six inches every Monday. "
From these three records, we can see that Zhang Heng's celestial body is similar to today's celestial body. However, Zhang Heng's celestial sphere is painted with 444 officials and 2500 stars named by him. The yellow and equatorial paintings of the armillary sphere have twenty-four atmospheres. Passing through the north and south poles of the armillary sphere, there is a rotatable polar axis. In the center of the celestial sphere, there should be a horizontal ring, indicating that the ground is flat. There should also be a pair of meridian double rings perpendicular to the horizontal ring, with the center of the double rings being the meridian of the observation point. When the celestial sphere rotates, some stars on the sphere are exposed above the horizon, that is, the stars come out; Some pass through the meridian, that is, in the stars, while the stars below the horizon are not. Some stars in the celestial sphere will always rotate on the horizon without falling below it. The boundary of this part of the sky is a small circle with the north pole as the center and the local latitude as the radius, which was called the internal gauge at that time. Similarly, there is a small circle with the south pole as the center and the local latitude as the radius, which is called the outer gauge. The sky area within the external ruler will never rise above the horizon.
There are sun, moon and five stars on Zhang Heng's celestial sphere. These seven celestial bodies not only rotate with the celestial sphere on Sunday, but also have their own complex movements in the background of stars and starry sky. Simulating these complex movements is far from what ancient mechanical technology can do. So we should think that they are just an appendage attached to the celestial sphere and can be moved by hand at any time. The purpose of moving is to make the positions of the sun, moon and five stars on the starry background adapt to the real position.