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.
Zu Chongzhi:
Most of his achievements in astronomical calendar are contained in his Da Ming Calendar and Refutation for Da Ming Calendar.
Before Zu Chongzhi, the calendar used by people was Li Yuanjia compiled by astronomer He Chengtian. After years of observation and calculation, Zu Chongzhi found that Li Yuanjia had great errors. So Zu Chongzhi set out to make a new calendar. In the sixth year of Song Xiaowu (AD 462), Da Ming Li was compiled. Daming Calendar was never adopted before Zu Chongzhi's death, and it was not officially promulgated until the 9th year of Tian Jian, Liang Wudi (AD 5 10). The main achievements of Daming Calendar are as follows:
The tropic year and sidereal year are distinguished, and precession is introduced into the calendar for the first time. The precession measurement is 45 years 1 1 monthly difference 1 degree (about 70.7 years difference today). The introduction of precession is a great progress in the legal history of China.
A tropical year is set at 365.24 148 1 (today's measurement is 365.2425438+09878), which is the most accurate data until Yang Zhongfu made a unified calendar in the fifth year of Qingyuan, Ningzong, Southern Song Dynasty (A.D. 1 199).
The new leap week of 39 1 year (144 leap) is more accurate than the leap week of 19 year (7 leap) adopted in the previous calendar.
The fixed intersection days are 27.2 1223 days (currently estimated as 27.2 1222 days). Accurate measurement of the number of months and days at the intersection makes it possible to accurately predict solar and lunar eclipses. Zu Chongzhi calculated the time of the four eclipses in the 23 years from the 13th year of Yuanjia (AD 436) to the 3rd year of Daming (AD 459) with Da Ming Li, and the results were completely in line with the reality.
It is concluded that Jupiter overtakes the sun once every 84 years, that is, the period of revolution of Jupiter is 1 1.858 years (currently measured as 1 1.862 years).
A more accurate five-star rendezvous period is given, in which the rendezvous period of mercury and Jupiter is also close to the modern value.
A method of determining the winter solstice time by measuring the length of the noon sun shadow with a standard table is put forward.
Zhang Sui (Monk and his party, 673-727 AD),
In Tang Dynasty, he was born in Changle, Weizhou (now Nanle County, Puyang City, Henan Province). Zhang Sui was gifted, studious and well-read since childhood. When I was young, I went to Chang 'an to study astronomy and mathematics. I made great achievements and became a famous scholar.
After Wu Zetian became emperor, his nephew Wu Sansi was prominent. In order to seek fame, he wooed scholars and celebrities everywhere to raise himself and tried to make friends with him several times. However, Zhang Sui didn't want to associate with him, so he left Beijing angrily and became a monk in Songshan in the East. He was named a monk, so he was called a monk.
In 7 12 AD, Emperor Xuanzong of the Tang Dynasty ascended the throne. Knowing that a group of monks were proficient in astronomy and mathematics, they were called to Chang 'an, Kyoto, to become astronomical advisers to the imperial court. Zhang Sui lived in Chang 'an for 10 years, which gave him the opportunity to engage in astronomical observation and calendar reform.
During the Kaiyuan period, Emperor Xuanzong of the Tang Dynasty ordered Zhang Sui to preside over the revision of the calendar. In the practice of revising the calendar, in order to measure the positions of the sun, the moon and the stars in their respective orbits and master their laws of motion, Liang Lingzan and * * made "Huntian Bronze Instrument" and "Zodiac Sky Patrol Instrument" to observe the celestial phenomena. The armillary sphere was made on the basis of Zhang Heng's armillary sphere in the Han Dynasty, with stars painted on it. The instrument runs by water day and night, which is consistent with the sky. There are also two wooden statues, one beating the drum at all times and the other ringing the bell every morning, which are more accurate than Zhang Heng's "The Armageddon". The purpose of "Zodiac Navigator" is to directly measure the coordinate positions of the sun, moon and stars in orbit when observing celestial phenomena. Zhang Sui used these two instruments to study astronomy effectively.
Before Zhang Sui, astronomers, including great astronomers like Zhang Heng, thought that stars were stationary. However, Zhang Sui re-measured the positions of 150 stars with instruments such as "Huntian Bronze" and "Zodiac Sky Patrol Instrument", and repeatedly measured the degrees for 28 nights from the celestial north pole. So as to find the stars moving. According to this fact, Zhang Sui deduced that the stars on the celestial body must be moving. So he overthrew the previous conclusion that stars were motionless, and Zhang Sui became the first person to discover the movement of stars in China. Harley, a British astronomer (A.D. 1656―― 1742) also put forward the idea that stars move by themselves, but it was more than a thousand years later than Zhang Sui's discovery.
Zhang Sui is a scientist who attaches importance to practice, and the scientific method he adopted has a decisive role in his achievements. Zhang Sui and Nangong said that together with others, they measured the solar shadow with a benchmark and calculated the relationship between the position of the sun and the solar terms. Zhang Sui has designed and manufactured a "complex moment diagram" astronomical instrument, which is used to measure the height of the North Pole all over the country. He used the data calculated by field measurement to overturn the inaccurate conclusion that "Wang Ji is a thousand miles away, but his shadow is an inch".
Zhang Sui's revised Dayan Calendar is an innovative calendar, which inherits the advantages and disadvantages of ancient astronomy in China and corrects its shortcomings and deficiencies. Therefore, great achievements have been made. The most outstanding performance is to correctly grasp the speed and changing law of the sun's movement on the ecliptic. Since the Han Dynasty, astronomers of all ages have believed that the speed of the sun running on the ecliptic is uniform and constant. Zhang Sui used unequal interval quadratic interpolation method to calculate the longitude difference between every two solar terms is the same, but the time interval is different. This algorithm basically conforms to astronomical practice and is a great progress in astronomy. Moreover, Zhang Sui's "Da Yan Li" calculates the degree of the ecliptic with the cubic difference of interpolation method, and also puts forward the scientific conclusion that the ecliptic will not return to its original place once a month, but will return once more than its original place. Dayan Calendar had a great influence on astronomy in China. Until the end of Ming Dynasty, historians adopted this calculation method and achieved good results.
In 724-725, a group organized astronomical geodesy at China 13. Astronomer Nangong said that the work of others in Henan is the most important in this measurement. From the data measured by Nangong Shuo and others, a group of people came to the conclusion that the height of the North Pole is one degree different, and the distance between the north and the south is 3565438+80 steps 0 (modern 13 1.3 km). This data is the arc length of the earth meridian at one degree. This is only 20.7km different from the local meridian arc length110.6km currently calculated at 34 5 north latitude. The length of meridian was measured for the first time in the world in the Tang Dynasty. A group began to compile calendars in 725, and completed the draft before his death, that is, Dayan Calendar, which was promulgated in 728. Da Yan Li has a rigorous structure and strict calculation logic. In the calculation of solar eclipse, the food situation in all parts of China was considered for the first time. Dayan calendar is more accurate than previous calendars, and it was taught by later calendars. In 733, this calendar was introduced to Japan.
Zhang Sui's achievements in astronomy are not only famous at home, but also have great influence in the world. His revised Dayan Calendar was a relatively advanced calendar in the world at that time. Japanese student Kibi No Asomi Makibi was sent to China to study astronomy. When he returned home, he took away one volume of Da Li Yan Jing and twelve volumes of Da Yan Li Zhucheng. So "Great Yan Li" was widely circulated in Japan and had a great influence. In addition, some of Zhang Sui's astronomical views are more than 1000 years earlier than those of world famous astronomers. It is not an exaggeration to call Zhang Sui a great astronomer in ancient China.