China has a long history of astronomy. By the Han dynasty, there had been schools of thought such as covering the sky, announcing the night and turbid the sky. Gaitian said that the sky is like a lid, the center of the lid is the North Pole, the lid turns left, and the sun, moon and stars turn right. Michelle Ye said that the sky is amorphous, and the sun, moon and stars "naturally float in the void" and are not attached to "celestial bodies". Huntian said that the sky is like an eggshell and the ground is like an egg yolk. Heaven and earth stand by and watch, carrying water and moving.
Michelle Ye's theory was unfortunately lost, and the two theories, Another Day and Huntian, competed with each other, and the more scientific Huntian theory gradually gained the upper hand. At the same time, instruments for observing astronomical phenomena are constantly appearing. For example, Luo made an armillary sphere in the period of Emperor Wu of Han Dynasty, Geng Shouchang made an armillary sphere in the period of Emperor Wu of Han Dynasty, and Jia Kui, a teacher of Cui Yuan in the period of Emperor Wu of Han Dynasty, made ecliptic bronzes. ?
Zhang Heng inherited and developed the achievements of predecessors. After Ren Taishi ordered, he worked harder to "study Yin and Yang" and finally "perfected the meaning of Xuan Ji". In the fourth year of Yuan Dynasty (A.D. 1 17), Zhang Heng made a bronze armillary sphere with unprecedented achievements.
The main body of the armillary sphere is a circle, and there are several layers that can run. The circumference of the outermost layer is 10 foot, 4 feet and 6 inches. Each floor is engraved with internal and external rules, such as south, north, yellow, equator, 24 solar terms and 28 solar terms, as well as "middle" and "outer" stars, the sun, the moon and the five latitudes. There are two leaking pots attached to the instrument, and there are holes in the bottom of the pot. The water drops push the circle and the circle rotates slowly according to the scale. As a result, all kinds of celestial phenomena are displayed in front of people. This instrument is placed in the secret room of the hall of GV. At night, the indoor observers report the sky phenomena at a certain moment to the sky observers on the platform in time, and the result is that the instruments are completely consistent with those in the sky.
There is a jade shovel (dragon) on each side of the bronze musical instrument, which spits water into the pot, with night on the left and sun on the right. There are gold and bronze immortals and Xu disciples on the pot respectively. "They all hold arrows in their left hands and carve arrows in their right hands, so different days will be sooner or later." Even more amazing: there are Swiss wheels and two pots with built-in mechanical devices under the steps. Driven by dripping water, the pod keeps rotating and opening and closing according to the coming and going changes of the moon, indicating the new moon, the moon, strings and signals, just like an activity calendar. It can be seen that this armillary sphere and its accessories have many similarities with modern fake celestial spheres. In the year before the birth of this instrument, Zhang Heng? First, a model named "Little Soul" was made with bamboo sticks. After a series of tests and corrections, it was cast into a big musical instrument. Who is the armillary sphere? Rolling? The crystallization of blood and sweat. He went on to write two explanations, namely "Illustration of the Amazonian Instrument" and "Annotation of the Water Leakage Turning to the Amazonian Instrument", and then wrote a book "Lingxian County" and a book "Lingxian County Map". In these works? Zhang Heng systematically expounded his astronomical theory, which reflected his simple materialistic view of nature. He believes that the universe is infinite and the movement 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.
Because of studying astronomy, calendars and making instruments, Zhang Heng's research on mathematics has also been strengthened accordingly. After making the armillary sphere, he wrote The Theory of Computing to "calculate it in the network world". He used the method of "progressive fraction" to calculate that the square root of pi is ten, which is 3. 16. This is a big step forward than the value of π=3 recorded in Zhou Xie. It was not until five or seven centuries later that Indian and Arab mathematicians put forward this value. ?
In the first year of Jianguang (A.D. 12 1), Zhang Heng was transferred to be a coach and always took charge of the imperial edict. He was not overwhelmed by complicated official duties, but stepped into the fields of physics, machinery manufacturing and so on, and made many amazing achievements. He became the leading mechanical manufacturing expert at that time, known as the "Wood Sage", and his exquisite artifacts were unparalleled. He used the principle of differential gear to build the south guide car and the drum car in his mind. He also carefully built a wooden bird, "fake feather purlin, belly machine, can fly for miles", which was simply a unique wooden "plane" in the world at that time! Unfortunately, like many of his masterpieces, most of the objects and detailed methods have been lost. ?
Zhang Heng also made a surveying instrument, the Earth Gauge, to study astronomical geography. He drew a topographic map, which has been passed down to the Tang Dynasty. He is good at painting landscapes and animals, and he is known as one of the four great painters in the Eastern Han Dynasty with Zhao Qi, Liu Bao and Cai Yong (the father of Wenxi). I also have a deep research on music and dance. For example, in "Ode to Watching Dance", he once described the dancer's dancing skills so skillfully: "Continuous flow, sudden continuation, fluttering like a phoenix, sleeves like snow."
(2) Guo Shoujing (1231-1316), born in Xingtai, Shunde (now Xingtai, Hebei), was an astronomer, water conservancy scientist, mathematician and instrument manufacturer in Yuan Dynasty.
Guo Shoujing, Wang Xun, Xu Heng and others jointly compiled the most advanced and longest-circulating calendar in ancient China-Shoushi Calendar. 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.
There are 14 kinds of astronomical calendar works compiled by Guo Shoujing, including Tuibu, Licheng, Yi Li Zhuan, Yi Xiang Fa, and Liu, with a total volume of 65,438+005.
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".