Zhang Heng made outstanding contributions to the development of astronomy, mechanical technology and seismology in China, and invented the armillary sphere and seismograph, which was one of the representatives of the theory of armillary sphere in the middle Eastern Han Dynasty. Later generations praised it as "Musheng" [2] (Kesheng). Because of his outstanding contribution, the United Nations Astronomical Organization named a crater on the back of the moon as "Zhangheng Crater" and the asteroid 1802 in the solar system as "Zhangheng Star". Later, in memory of Zhang Heng, Zhang Heng Museum was built in Nanyang.
armillary sphere
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. [ 15]
The leaky astrolabe is a water-borne elephant. Use a copper ball with a diameter of more than four feet, which is engraved with 28 nights, Chinese and foreign officials, yellow equator, north and south poles, 24 solar terms, constant display circle and constant hidden circle to form an elephant, and then use a set of rotating machinery to combine the elephant with the clepsydra. The elephant is controlled by running water from a leaky kettle to make it rotate synchronously with the celestial sphere, thus showing the Sunday visual movement of the starry sky, such as the appearance of stars and the transit of the sun. It also has a subsidiary organization called Ruilun Cai Ming, which is a mechanical calendar, connected with elephants by transmission devices. From the beginning of each month, a leaf is born every day; Drop a leaf every day after half a month. Among them, the second-class clepsydra used is the earliest known record of the second-class clepsydra.
The armillary sphere in Zhangheng Museum, Nanyang, Henan Province (three pieces)
Zhang Heng wrote an article after he made the armillary sphere. The full text of this article has been lost. In the Liang Dynasty, Liu Zhao made a long citation when he annotated the Book of the Later Han Dynasty, which was handed down from generation to generation. In Liu Zhao's note, the title of this passage is Zhang Heng's Marriage Proposal. Calling it a "wedding ceremony" may be a simplification of Liu Zhao. In ancient times, the naming of musical instruments was not strict. Although the word "wedding instrument" was standardized as an observation instrument in later generations, it could also be used as a playing instrument before Sui and Tang Dynasties.
Calendar system
Zhang Heng once participated in a calendar discussion in the second year of Yan Guang (A.D. 123). According to the laws and calendar records of the later Han Dynasty, Zhang Heng was Shang Shulang at that time. The cause of this great discussion is that some people criticized the scientific quarter calendar used in the Eastern Han Dynasty at that time from the superstitious concepts such as divination and disasters, and proposed that it should be changed to Jiayin Yuan calendar, which is suitable for divination. Others, starting from Emperor Wu of the Han Dynasty's "expanding territory and enjoying the country for a long time", think that taichu calendar should be adopted. Zhang Heng and Zhou Xing, two other businessmen, refuted and heckled the above two viewpoints, which made the proponents of these two erroneous viewpoints speechless or answered incorrectly, thus contributing to preventing the calendar from going backwards. During the discussion, Zhang Heng and Zhou Xing also studied the astronomical observation records for many years, compared them with the theoretical calculations of various calendars, and put forward appraisal opinions. They think that the nine methods are the most accurate and recommend them. Indeed, the numerical values of the tropical year length and lunar month length in Nine Daofa are more accurate than those in taichu calendar and Jili of the Eastern Han Dynasty. [ 17]
Moreover, the Nine Laws admit that the speed of the moon is uneven, while other calendars at that time were only calculated according to the uniform speed of the moon. Therefore, the combination of nine methods is more in line with astronomical reality than other calendars at that time. However, if calculated according to the Nine Laws, there may be a phenomenon that three months are a 30-day big month or two 29-day small months are connected. According to the calendar arrangement that people have been used to for thousands of years, the big moon and the small moon have always been connected. At most, 17 months, two big moons are connected once, and there is no phenomenon that three big moons are connected, let alone two small moons are bright. Therefore, the phenomenon that three big months or two small months are connected brought by the Nine Laws is unacceptable to people who are used to being conservative. In this way, the proposal of Zhang Heng and Zhou Xing to adopt the Nine Methods was the most reasonable and progressive at that time, but it was not passed in this big discussion. This is a loss in the legal history of China. The adoption of the inconsistent lunar calendar was delayed for more than half a century, and it was not until Liu Hong's dry calendar was officially adopted for the first time.
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:
Zhang Heng believes that the universe is infinite and the motion of celestial bodies is regular. Moonlight is the reflection of the sun's light, and an eclipse is because the earth blocks the sun's light, and the moon goes around the earth and rises and falls. He realized some laws of the movement of the sun (which should be the revolution of the earth) and correctly explained the causes of the long nights in winter, short nights in summer, vernal equinox and autumnal equinox. He pointed out that there are 2,500 stars that can be seen in the Central Plains, which is slightly close to what is known today. After observing the movement of some celestial bodies, he came to the conclusion that the number of days in a week is 365 degrees and a quarter degrees, which is almost the same as the modern measured value that the earth orbits the sun for 365 days, 5 hours, 48 minutes and 46 seconds.
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