In the third year of the Eastern Han Dynasty (AD 78), Zhang Heng was born in a famous family of poetry, calligraphy and painting in Nanyang, Henan. His grandfather, Zhang Kan, was knowledgeable and virtuous. In the Book of the Later Han Dynasty, Zhang Kan was praised as the "son" by people at that time because of his excellent character and knowledge. Later, Liu Xiu rose up against Wang Mang's New Deal. At the beginning of the Eastern Han Dynasty, he helped haing s ngor destroy Gongsun Shu, and made outstanding achievements repeatedly. After the official reached the prefect of Yuyang, he fought against the Huns, cherished the people's resources and developed production, so folk music ruled the country. The popular folk song at that time was "Junwei Zhang is in high spirits". Zhang Kan is an upright official. After his death, he left no wealth. When Zhang Heng was a child, his family gradually became poor due to the decline of his family, and he always got help from his old friends.

Zhang Heng was born in such a family, with a prominent family background, and his grandfather was a model, but his family was not rich and lived in poverty. Such an environment made Zhang Heng aim high from an early age, instead of indulging in happiness, he studied hard in difficulties, persevered and made progress by himself. During his growing up, his family study and his grandfather's moral achievements had a great influence on Zhang Heng's later becoming a great scientist. Later, his grandparents and grandchildren were listed in the Book of the Later Han Dynasty and went down in history together.

Zhang Heng's youth began with his study tour career, mainly engaged in literary creation. Zhang Hengchuan described his experience in the Book of the Later Han Dynasty as follows: "Heng Shaoshan is a scholar, and he is good at three things. Because of entering the capital, watching imperial academy, learning the Five Classics and buying skills "(Five Classics: Book of Songs, Book, Ceremony, Book of Changes, Spring and Autumn Period; Six arts: ceremony, music; , shoot, royal, book, number).

In 93 AD, Zhang Heng, who was only 15 years old, bid farewell to his family and went out to study. Enter Wuguan first, then visit Sanfu; From 95 AD to Luoyang, he lived in Luoyang for five or six years. He often went to imperial academy to visit famous teachers and humbly asked for advice, which laid a good foundation for his future scientific research work. In AD 100, Zhang Heng went to Wancheng as editor-in-chief at the request of Baode, the magistrate of Nanyang. During this period, he created many famous literary works. In 108, Baode was transferred to the capital and invited Zhang Heng to work together. But Zhang Heng felt that his studies were not successful enough to help the world, so he resigned and returned to his hometown to study at home. In the following five years, his research focus shifted from Confucian classics and literature to philosophy, astronomy and calendar calculation. It is worth mentioning that Zhang Heng turned from literature to scientific research, which was greatly influenced by his close friend Cui Yuan. Cui Yuan is Zhang Heng's junior in Luoyang and a disciple of Jia Kui, a famous Confucian scholar. He has a quick mind and likes astronomy and calendar calculation. In the following decades, the two exchanged views and consulted together, and they have always been like-minded friends. During my stay in Nanyang. Zhang Heng carefully studied Yang Xiong's Xuan Jing in the Western Han Dynasty. He read and thought repeatedly and communicated with Cui Yuan. Finally, both of them wrote their own unique notes on the Xuan Jing, which became the story of a philosopher. In addition, he also devoted himself to the research of astronomy and calendar calculation. In 1 1 1 year, Zhang Heng's reputation of reading widely and linking ancient and modern times spread far and wide in the capital, and he was named Shang Shulang by the "bus special event" and moved to Taishiling the following year. Before and after assuming this position, the total amount reached 14 years. Many of Zhang Heng's major scientific research work was completed at this stage.

Write "Lingxian"

Zhang Heng, with noble character and outstanding talent, is the best candidate for Taishiling. And his life is based on "no respect for position, no respect for virtue;" Not ashamed of not being thick, ashamed of not being rich in wisdom ",indifferent to fame and fortune. "Taishiling is only a middle-level official, and his salary is not very rich, but he is very satisfied with this position and can further develop the field of astronomical research.

During his tenure as Taishiling, Zhang Heng actively engaged in theoretical research, systematically observed the movement of celestial bodies, wrote books such as Lingxian, created planetarium, and studied the calendar.

Lingxian is an astronomical masterpiece written by Zhang Hengji after years of practice and theoretical research, and it is also an immortal masterpiece in the history of astronomy in the world. The book comprehensively expounds the generation of heaven and earth, the evolution of the universe, the structure of heaven and earth, the nature and movement of the sun, moon and stars, and many other major topics, which raised the level of ancient astronomy in China to an unprecedented new stage, made China's astronomical research ahead of the world at that time, and had a far-reaching impact on later generations.

Next, the astronomical achievements in the article Lingxian are described respectively.

Firstly, the origin and structure of the universe are discussed. Regarding the formation of heaven and earth, Lingxian believes that everything in heaven and earth is developed from the original chaotic and undivided vitality. The vitality was chaotic at first, and then it was divided into turbidity. The interaction of clear and turbid air forms the universe. The clear sky is outside, and the muddy land is inside. This idea of celestial evolution explains the formation of the universe from the material movement itself, and holds that the structure of the universe is not eternal, but constantly developing and changing. These views are basically consistent with the modern theory of cosmic evolution.

Second, the cause of the solar eclipse. Based on the theory of Huntian, the causes of lunar eclipse are scientifically expounded. Zhang Heng wrote in Ling County: "The moonlight shines; Born in the sun. There is light in the sky and light in the day. " The moon itself does not shine, but the sun shines on the moon, and the moon refracts light. Where the sun does not shine, there will be losses. The so-called "the moon is full of rain and shine." If the moon enters the shadow of the earth-Zhang Heng named the shadow "dark", an eclipse will occur. ) It can be seen that the explanation of the eclipse in Lingxian is very scientific.

Third, the universe is finite and infinite. Although Zhang Heng compares the sky to an eggshell and the earth to the yolk in an eggshell, he does not think that a hard shell is the boundary of the universe. The finiteness and infinity of the universe has always been a long-standing debate in astronomical circles at home and abroad. When Zhang Heng wrote Lingxian, he was influenced by some astronomical viewpoints in Yang Xiong's Xuanjing, but he did not follow Yang Xiong's viewpoint about the infinity of the universe, but had his own opinions. Zhang Heng believes that the universe that people can see is limited, but beyond what people can see, they "don't know and don't know". Finally, the knower, the universe is also called. The list of the rest is infinite, and the end of the universe is infinite. "

Fourth, measure the average angular diameter of the sun and the moon. The angular diameter of the sun and the moon measured by Zhang Heng is 1/736 for the whole Sunday, which is converted into the current 360-degree system, which is 29 degrees 2 1 min. Compared with the average angular diameter of the sun and the moon measured by modern astronomy, the absolute error is only 2. Limited by the scientific and technological level and observation conditions more than two thousand years ago, this value can be said to be quite accurate.

Fifth, remake the new star list with 3,000 stars. On the basis of careful observation of celestial bodies, Zhang Heng sorted out and summarized several catalogues handed down by predecessors, and established a new star catalogue with as many as 3,000 stars. According to Lingxian, among them, "there are 24 Chinese and foreign officials and wise men, and 320 are famous, which is 2.5 thousand stars, but the proportion of sea people does not exist." The catalogue made by Zhang Heng is not only far superior to the predecessors, but also inferior to the later generations. At the end of Han Dynasty, the catalogue made by Zhang Heng was lost. The catalog established by Chen Zhuo in the early Jin Dynasty has 1464 stars, which is only half of them. It was not until the Kangxi period of the Qing Dynasty that the number of people passing through the telescope reached 3000. It can be seen that the loss of Zhang Heng's catalog is a great loss in the history of astronomy in China.

Sixth, the five-star movement. Regarding the movement of the five stars, Zhang Heng proposed that the sun, the moon and the five stars run between heaven and earth, not on the sky wall. Moreover, the seven celestial bodies move at different speeds, "the near sky is late and the far sky is fast." The so-called sky refers to the imaginary sky wall, that is, it is fast when it is close to the ground and slow when it is far from the ground. He divided the five stars into water and gold according to their distance from the ground and their running speed. Water and gold are close to the ground, moving fast, and attached to the moon, which belongs to yin; Fire, wood and earth are three stars, which are far from the ground and move slowly. They are attached to and belong to the sun. Inheriting the tradition, he divided the movement direction of celestial bodies into antegrade, retrograde and retrograde. Although this view is wrong, his search direction of trying to trace the mechanical reasons of celestial motion is undoubtedly correct. Although Zhang Heng didn't know that all planets, including the earth, revolve around the sun, he did find that the speed of planetary motion is related to the distance from the central celestial body. Unfortunately, this correct idea did not attract enough attention from later generations, which greatly restricted the development of astronomy in China. Until the17th century, Kepler pointed out three laws of planetary motion on the basis of Copernicus' solar system theory, one of which is that the speed and period of planetary revolution depend on the distance between the planet and its central celestial body, the sun.

Lingxian is one of the most outstanding astronomical works in the history of ancient astronomy in China, and it is also a milestone in the development of astronomy in China. Although there are still some mistakes and shortcomings, its significance in the history of astronomy is not inferior.

Make an armillary sphere

Another outstanding contribution of Zhang Heng to the development of astronomy in China is that he created the armillary sphere. Zhang Heng's armillary sphere is to supplement his astronomical theory-the theory of armillary sphere.

Zhang Heng's "armillary sphere" is used to demonstrate the movement of celestial bodies. It consists of a bracket and a hollow copper ball with a diameter of more than four feet, which is similar to the modern celestial sphere. The ball is engraved with 28 stars and Chinese and foreign officials. After Zhang Heng finished the design, he first made a small musical instrument out of bamboo. He picked out some bamboo pieces, carved degrees on the outward side, woven them into rings, and then connected several bamboo rings into a musical instrument model. After inspection, he enlarged and copied the model, and then cast it in copper. As mentioned above, the main body of the armillary sphere is a hollow copper ball with a diameter of four feet six inches and a circumference of one foot four feet six inches. The ball is supported by an iron shaft which passes through the center of the ball along the celestial axis. The two intersections with the sphere represent the north and south poles of the celestial sphere, so this iron axis is called the polar axis and can rotate. In the center of the periphery of the celestial sphere, there is a horizontal ring representing the horizon, and a pair of meridian double rings perpendicular to the horizontal ring, with the north and south poles in the middle. The polar axis is supported on the meridian ring. The center of the meridian double ring is the meridian of the observation point. The outer surface of the ball is engraved with 28 huts and Chinese and foreign officials. When the celestial sphere rotates, some stars on the sphere are above the horizon, which means that the stars come out; Some pass through the meridian, meaning in the stars; Others are not below the horizon, which means there are no stars. The bronze ball is also engraved with the ecliptic circle and the equatorial circle, which intersect at an angle of 24 degrees. There are 24 solar terms scales on it, which are 365 and a quarter degrees from the winter solstice, each four minutes long and divided into four squares, indicating that the sun runs once a day on the ecliptic.

The operation of Zhang Heng's armillary sphere is vividly described in Jin Zhi: "Zhang made a bronze armillary sphere in the secret room, turned it around by leaking water, and asked the waiter to close the door and wait. Waiting for people to tell the sky watchers at the funeral platform that' a star begins to see, a star reaches the middle, and a star dies today'. They are all like a combination. " Zhang Heng put the armillary sphere in a secret room with closed doors and windows, and used hydraulic power to drive the armillary sphere to rotate. The observer in the room looked at the changes of the sky on the armillary sphere and told the people who were observing the sky on the platform outside: "So-and-so star has appeared on the horizon, so-and-so star has moved to the center of the sky, and so-and-so star has fallen on the horizon. One is inside, the other is outside, and the observation results of the two people are completely consistent.

Zhang Heng connected the armillary sphere, gear system and timing clepsydra. Unfortunately, the details of this device are not recorded in the history books. However, it is speculated that on the one hand, the time should be recorded by the clepsydra, on the other hand, the float in the clepsydra should be bypassed by one end of the rope, and the other end is connected with a counterweight. When receiving water, the amount of water in the pot increases, the float rises and the counterweight at the other end drops. Up and down, the rope drives the polar axis to rotate, making the celestial sphere rotate. Whether this speculation is true or not, it is generally acknowledged that Zhang Heng used mechanical devices to drive armillary sphere to simulate the movement of stars in real astronomical phenomena, and it can achieve high accuracy, which is in line with the actual situation, which is unprecedented in the history of astronomy and mechanics in China. This leaky armillary sphere is actually an astronomical clock and almanac. It can be said that it is the beginning of later mechanical clocks and watches, which has a great influence on the development of later mechanical clocks and watches. Its creator, Zhang Heng, is also the originator of clock making, which is also the pride of our Chinese nation.

Zhang Heng also created an unprecedented water transport mechanical device "Ruilun Pod". Pod is a plant in myths and legends. It is said that it grows a pod every day from the new moon until the full moon reaches 15. Then drop a pod every day until the end of the month and start at the beginning of next month. According to this mythical plant, which is completely derived from man's ideal, Zhang Heng turned this ideal into reality with mechanical devices. "Swiss wheel pod" is a kind of wheel, which uses hydraulic rotation to turn out a pod every day from the beginning; Since the sixteenth, I have been transferred to another place every day. The so-called "ups and downs with the month, ups and downs with the calendar" is equivalent to the date display of today's clocks and watches.

The world's first instrument for predicting earthquakes-seismograph.

Zhang Heng has also made great achievements in the field of seismology, and his masterpiece is the invention of the seismograph. Hou Feng seismograph, also known as seismograph, was made in the first year of Yangjia (A.D. 132). It is the earliest instrument for observing and reporting earthquakes in the world. According to the Book of the Later Han Dynasty, the seismograph is made of pure copper, like an oval wine bottle with a diameter of 8 feet. There are "mountain turtles, birds and beasts" cast outside the vessel, symbolizing the mountains and rivers on the ground and the blue dragon, white tiger, suzaku and Xuanwu in the sky for 28 nights. In vitro, the eight diagrams are engraved with seal characters, indicating the qi in all directions. Attached to the eight dragons, the dragon heads in all directions, symbolizing Yang; Eight toads hold their heads under the dragon's head, symbolizing yin. This constitutes a dialectical relationship between yin and yang, up and down, and movement. There is a tall and thin copper column in the musical instrument, which is called a "single column". Stigma occupies an indomitable position in the body, which is designed according to the ancient Tianzhu theory. There are eight groups of slideways beside the stigma, which are connected with the faucet through levers, and the faucet mouth is equipped with copper balls. During the earthquake, the inclined column fell to the slide in the direction of the earthquake, pushing the lever to the end and triggering the tooth machine like an engine through the leverage. The faucet opened, and the copper ball fell into the mouth of the toad below, making a "clang". The host can report the direction of the earthquake according to the direction of the ball. This instrument is ingenious in conception and precise in manufacture. According to historical records, "taking the test as truth is about being like a god." It can not only detect earthquakes that people can feel at close range, but also detect earthquakes that occur thousands of miles away!

Zhang Heng is also fruitful in mechanical production. The manufacture of the above-mentioned armillary sphere and seismograph requires superb mechanical manufacturing technology. In addition, he also made guide cars, drum cars and wood carvings. The compass adopts automatic and flexible gear system. No matter how the car turns, Woodenhead standing on the car always points to the south. It acts like a compass, which is used by the emperor to point the way when he goes on patrol. The drum car in memory is also a gear device, which transmits the rotation of the axle when the wooden car is running to the arm of the wooden man holding the drum, so that the wooden man on the car drums once every time the wooden car walks, which can be used to record the mileage. According to historical records, Zhang Heng "tastes like a wooden bird, pretending to have feathers, and his belly can fly for miles" (1: the wings of a bird; Machine: mechanical device). This is a kind of wooden bird that can fly for a long time by itself. What are the specific structures of these ingenious systems? There is no conclusive research, but Zhang Heng is indeed a skilled master of mechanical manufacturing. Together with Ma Jun, he was honored as a "wood saint" by later generations.

Cui Yuan praised Zhang Heng for being "poor in mathematics and natural in nature" (you are equal). The premise of "nature plays tricks on people" is "counting the poor in the world" This sentence not only praised Zhang Heng's profound astronomical knowledge and the magic of making utensils, but also greatly praised Zhang Heng's achievements in mathematics. It is mentioned in "The History of the Later Han Dynasty" that Zhang Heng wrote a mathematical monograph "Calculation Theory". Unfortunately, this book has been lost and its content is unknown. However, there is still pi determined by Zhang Heng, which is 10. Although it is not very accurate, it has made great progress compared with the previous theory of "three diameters per week".

Only if you are talented can you stop at the top of the mountain.

In A.D. 123, Zhang Heng participated in the deliberation that shook the ruling and opposition parties at that time. This calendar discussion originated from divination advocated by the world at that time. Digital divination, also known as divination, prevailed in the Eastern Han Dynasty. "divination" is a kind of prophecy that decides good or bad with deceit as its argot, and "latitude" is a divination superstition attached to Confucian classics, which combines with Confucian classics to form divination theology and is in an absolute authoritative position in ideology. At that time, some people criticized the scientific four-year calendar on the grounds that "Yuan corresponds to heaven, which is divination", and suggested that it should be changed to Jia calendar that conforms to divination, while Liang Feng advocated going back and restoring the calendar based on divination, which was supported by many courtiers. Those who oppose changing the calendar are also divided into two factions. One school thinks that "the quarterly calendar is the most correct and should not be changed". Zhang Heng and another Shang Zhouxing thought that the calendar should not be associated with divination. He pointed out that the formulation of the calendar should be based on the actual operation of the sun, moon and stars, rather than judging the quality of the calendar by subjective assumptions and accidental events. This shows that Zhang Heng, as a scientific worker, is not afraid of power and is noble in seeking truth from facts.

Zhang Heng is a rare all-round development figure. Besides brilliant achievements in astronomy, seismology, mechanical technology and mathematics, he also has profound attainments in philosophy, literature and painting.

In philosophy, he made an in-depth study of Yang Xiong's Taixuan Jing. In the history of literature, Zhang Heng is a great writer and occupies an important position. Such as gorgeous rhetoric, magnificent, the Han Dynasty Ci Fu to a new peak. And also put forward the eternal philosophy of "a husband's water can carry a boat or overturn it" Fantastic writing is highly respected by future generations. Besides, he was the first person to write lyric poems. The masterpiece Wenquan Fu has a fresh style and elegant dictionary, which makes people forget the customs. This is an important turning point in the development of Ci and Fu in Han Dynasty. Zhang Heng's third great achievement in literature is the creation of a new seven-character poem represented by Four Sorrow Poems, which laid the foundation for the later seven-character poems and has far-reaching significance and influence. Zhang Heng was also a great painter in the Eastern Han Dynasty. His topographic map spread to the Tang Dynasty and was listed as one of the six great painters in the Eastern Han Dynasty by Zhang Yanyuan in the Tang Dynasty.

Zhang Heng's requirements for himself are "knowledgeable and indomitable". This spirit of perseverance and perseverance is a brilliant portrayal of his life.