Analysis:

Guo Shoujing,

Zhang heng,

Zu Chongzhi Zhang Heng (78- 139) was born in Xi 'e, Nanyang (now Shiqiao, Nanyang County, Henan Province). He was a great astronomer in the Eastern Han Dynasty and made an indelible contribution to the development of astronomy in China. In mathematics, geography, painting and literature, Zhang Heng also showed extraordinary talent and extensive knowledge.

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 the 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."

Zu Chongzhi (429-500), a native of Wen Yuan, was an outstanding mathematician, astronomer and mechanical manufacturer in the Southern and Northern Dynasties.

In astronomy, Zu Chongzhi created a famous new calendar in the history of China-Daming Calendar. In Da Liming, he quoted precession for the first time, which was a major reform in the calendar history of our country. He also adopted the new leap week of 39 1 144 leap month, which is more accurate than the leap week of 7 leap months invented in ancient times. The regression year and intersection days calculated by Zu Chongzhi are very close to the observed values.

Mathematically speaking, the true value of pi calculated by Zu Chongzhi should be between 3. 14 15926 and 3. 14 15927, which is more than a thousand years earlier than that in Europe.

In terms of machinery manufacturing, we have made a copper compass car, which is ground by water hammer with hydraulic rice milling, and can walk hundreds of miles a day, such as a "thousand-mile boat", a leaky kettle, scorpions and other timing instruments.

To commemorate Zu Chongzhi's achievements, people named the crater on the back of the moon "Zu Chongzhi Crater" and the asteroid 1888 "Zu Chongzhi Asteroid".

Guo Shoujing (1231-1316), a native of Xingtai, Shunde (now Xingtai, Hebei), was an astronomer, hydraulic scientist, mathematician and instrument manufacturer in Yuan Dynasty.

Guo Shoujing, Wang Xun, Xu Heng and others worked out the most advanced and longest-lasting calendar in ancient China. In order to compile the calendar, he created and improved more than a dozen astronomical instruments, such as simple instrument, altimeter, climatologist, armillary sphere, upright instrument, landscape instrument and peep instrument. Twenty-seven observation stations have been set up all over the country, and a large-scale "four seas survey" has been carried out. The average error of the measured Arctic height is only 0.35; The average error of the newly measured 28-night distance is less than 5'; The new value of yellow-red intersection angle is measured, and the error is only 1'. The tropical year is 365.2425 days, which is completely consistent with the current Gregorian calendar.

Guo Shoujing's astronomical calendar works include Tuibu, Licheng, Yi Li Zhuan, Yi Xiang Fa, He Liu et al. 14, with the volume of *** 105.

To commemorate Guo Shoujing's achievements, people named the crater on the back of the moon "Guo Shoujing Crater" and the asteroid 20 12 "Guo Shoujing Asteroid".