Chapter 42 Section 8 Armillary Sphere, Armillary Sphere, Leu Ke and Gui Biao

During this period, my country's traditional astronomy reached its peak.The level of all aspects of astronomy has been greatly improved. Here we only take a few astronomical constants as examples to see it. Regarding the length of the return year, the "Tongtian Calendar" of the Southern Song Dynasty (compiled in 1199 AD) and the "Shoushi Calendar" of the Yuan Dynasty (compiled in 1281 AD) both take 365.2425 days, with an error of about 22 seconds.The Gregorian calendar we use now is this value, which was promulgated by Pope Gregory in 1582. "Tong Tian Li" also clearly puts forward the new concept that the length of regression year is larger than the past and the present is small, and gives the mathematical expression of the changing law of the past and the present, which is of great significance in the history of astronomy.

Regarding the determination of the time of the winter solstice, the error of the results of Guo Shoujing and others is less than 0.5 ticks (1 tick is equal to 14.4 minutes). Regarding the calculation of the equatorial precession value, the Southern Song Dynasty achieved a result of 77.57 years difference, which was very close to the theoretical value of 77.37 years difference, and was in the leading position in the world at that time. In terms of eclipse cycle research, the Southern Song Dynasty obtained the result that 4127 node months are equivalent to the length of 324 eclipse years, and it can be estimated that the length of an eclipse year is 346.6199 days, which is only about seven seconds away from the theoretical value.However, the length of the eclipse year determined in Tang Dynasty is 346.6212 days, which is 137 seconds different from the theoretical value. In the 19th century, the American astronomer Newcomb proposed an equivalent result, which was highly praised by the astronomical community and was called the Newcomb cycle, but it was more than 1,000 years later than our country.

... The new achievements in astronomy and the progress of the calendar are inseparable from the progress of observation instruments.During this period, the observation instruments in ancient my country have made great progress. Armillary sphere We mentioned earlier that Zhang Heng improved the armillary sphere, and after Zhang Heng, all dynasties have made improvements.Especially during the Tang and Song Dynasties, many people created new armillary spheres. With the improvement of the armillary sphere, the rings also continue to grow, so that there are as many as eight or nine, covering a large sky area, and it is very inconvenient to correct, install, and operate.Therefore, after the Song Dynasty, the armillary sphere has undergone two changes. One is to reduce the number of rings, and the other is to change the installation position of some rings to expand the field of vision.

Shen Kuo in the Song Dynasty proposed to change the position of the ring and cancel Bai Daoyi.Guo Shoujing further canceled the zodiac ring and created Jianyi.Jianyi is novel in design and unique in structure, which is a revolution in the history of armillary spheres.Its equatorial device is the prototype of the modern large telescope equatorial device, the horizon device is the forerunner of the modern horizon theodolite, and the reticle used in the balance is the ancestor of the reticle in the current astronomical telescope. On the basis of Zhang Heng's water transport muddy image, the water transport instrument platform and his party designed and manufactured a "water transport muddy sky".Its structure, in addition to the automatic movement, is also equipped with an automatic timer, which is the origin of modern astronomical clocks.In the Northern Song Dynasty, Su Song, an astronomer and medical scientist, presided over the manufacture of the "Water Transport Astronomical Platform".It is 12 meters high and about seven meters wide. It integrates the armillary sphere, armillary image, timekeeper and standard into one.The observatory is powered by water power and driven by a complex gear train, which can coincide with the day and night rotation of the celestial sphere. It is also equipped with wooden figures who can beat bells, drums, and gongs to report the ebb and flow of time.Among them, a device similar to the anchor escapement in modern mechanical clocks has been created, which is the originator of modern astronomical clocks.There is a movable roof panel on the top of the platform, which is the first of its kind in modern observatories that can open the roof.

There are two kinds of water leaks (floating leaks) and hourglasses, and floating leaks are the main ones.In 1031 AD, Yan Su of the Northern Song Dynasty made major improvements to Fulou.He adopted the flooding system for the first time, that is to keep the water in the floating drain in a flooding state all the time, so that the excess water flows out from the small hole on the upper part of the floating drain, ensuring a constant water level in the floating drain and improving the accuracy of timing. Guibiao is an instrument used in ancient my country to measure the length of the shadow of the sun.Before the Yuan Dynasty, eight-foot-high tables were used, but Guo Shoujing made bold innovations and established a four-foot-high table and the method of measuring shadows with scene symbols.That is, a copper beam with a diameter of three inches is installed on the top of the high table, and the scene symbol is a thin copper sheet that can be rotated on a small frame, with a small hole in the middle.When the sun passes through the meridian, put the Jingfu on the horizontal surface and move it from north to south, and turn the copper piece so that the light passing through the top of the surface passes through the small hole, forming a rice-grain-sized horizontal shadow with a copper beam in the center on the surface. of the image.In this way, it overcomes the defect that shadows are unclear due to sunlight scattering during shadow measurement in the past, and improves the measurement accuracy.In the history of the development of optical measuring instruments, this is a significant achievement.Today, the former site of Dengfeng Observatory in Henan Province still preserves the ruins of Guo Shoujing's high-level achievements.