Where is the original "base" of human observation space?

Historical data show that China is one of the countries with early development of astronomy in the world and has a long history of astronomical observation. According to legend, there was an observatory in the Xia Dynasty, which was called "Qing Tai" at that time, the observatory in the Shang Dynasty was called "Shentai" and the Zhou Dynasty was renamed "Lingtai". Later, all the observatories in the past dynasties had names such as observatory, stargazing platform, four rooftops and stargazing platform.

Beijing ancient observatory

In fact, the early observatory was not only a place to watch stars, but also a place to worship. Ancient emperors sacrificed to heaven here, and at the same time appointed full-time staff to observe the astronomical phenomena, divine good and bad luck and compile almanac.

Later, with the development of society, the worship of heaven and the observation of heaven gradually separated, and the observatory specializing in astronomical observation began to be independent. Since the observation of astronomical phenomena is closely related to the production activities of ancient agriculture and animal husbandry, astronomical organizations have been highly valued in China since then. Except for special circumstances, the phenomenon stations and sky-watching equipment of past dynasties were built in Beijing.

Ancient stargazing platform in Dengfeng, Henan Province

Up to now, there are still many ancient observatory sites in China, among which Dengfeng Ancient Observatory in Henan and Beijing Ancient Observatory are well preserved. There is also Luoyang Lingtai, located in Yanshi County, Henan Province. It was a large observatory in the Eastern Han Dynasty. According to legend, the famous scientist Zhang Heng once worked in Lingtai. However, this ancient observatory is now in ruins. According to historical records, Lingtai in Luoyang once presented a busy scene in its heyday. The platform is about 20 meters high and the base is about 50 square meters. Taiwan Province has 43 staff members, with a fine division of labor and various observation projects. Therefore, China's astronomy was very developed in the Han Dynasty, and it was in a leading position in the world at that time.

Dengfeng Ancient Stargazing Observatory is located in Gaocheng Town, Dengfeng County, more than 80 kilometers east of Luoyang. It is the earliest existing observatory building in China. Founded in Yuan Shizu in the 16th year of Zhiyuan (1279), it has a history of more than 700 years. The towering platform and a long embankment under the stage just formed a special viewing. The high platform is a vertical watch with a height of 9.46 meters; The long dike is equivalent to Tugui, and it is called the measuring side. It is 3 1. 19 meters long, and it runs north and south.

Schematic diagram of planetarium

Located in the southwest of Jianguomen overpass, Beijing Ancient Observatory was built in the seventh to eleventh years of Ming Dynasty (1442~ 1446). After the Ming and Qing Dynasties, its appearance has not declined. After the Revolution of 1911, the ancient observatory was attached to the Ministry of Education and became the central observatory during the Beiyang government. From the Ming Dynasty to 1929, Beijing Ancient Observatory continuously observed for nearly 500 years, setting a world record for the longest continuous observation time.

On the other hand, Beijing Ancient Observatory is equipped with eight kinds of astronomical observation instruments in Qing Dynasty (celestial sphere, equatorial theodolite, ecliptic theodolite, horizon meridian, quadrant, horizon theodolite and Ji Chen instrument), which is famous for its beautiful shape and fine carving. April 1983 was officially opened to the public.

The gauge is an astronomical instrument for measuring the length of the sun shadow in ancient China, which consists of two parts: the gauge and the gauge. The benchmark and pillar for measuring the sun's shadow standing upright on the flat ground are called watches; The rigid plate used to measure the length of the surface shadow in the direction of due south and due north is called Gui.

A long time ago, people found that houses, trees and other things would produce shadows under the sunlight, and the changes of these shadows had certain rules. So he erected a pole or pillar on the flat ground and observed the change of the shadow. This pole or pillar is called a "watch"; You can know the time by measuring the length and direction of the shadow with a ruler. Later, I found that the shadow of the table was always cast to the north at noon, so I laid a ruler made of slate on the ground, perpendicular to the vertical table. One end of the ruler is connected to the foot of the table, and the other end extends to the true north direction. This ruler made of slate is called a reed. At noon, the shadow was cast on the slate, and the ancients could directly read the length of the shadow.

After long-term observation, the ancients not only learned that the shadow at noon in a day was the shortest, but also concluded that the shadow from summer to the sun was the shortest at noon in a year. At noon from winter solstice, the sun shines obliquely and the shadow is the longest. So the ancients used the length of the noon shadow to determine the solar terms and the length of a year. For example, the longest value of surface shadow is measured twice in a row, and the number of days between the two longest values is the length of time of 1 year. No wonder the ancients in China knew that 1 year was more than 365 days.

sundial

Yizheng copper standard is the earliest existing standard in China. 1965 Unearthed from the Eastern Han Tomb,No. 1 Shibei Village, Yizheng City, Jiangsu Province. Yizheng copper standard is 34.5 cm long, and the standard is 1.5 feet in Chinese, and the size unit is engraved on the side; The height of the watch is 19.2 cm, which is 8 inches in Chinese. Guiyu and the watch are connected by a pivot, which makes them integrated. When in use, the watch stands vertically on the turtle tail; Usually, the watch can be folded into the space left in the GUI body, which is convenient to carry. According to tradition, the height of a watch is 8 feet, which has been used for a long time. The height of the meter is just 8 feet110, which shows that it is a portable measuring instrument, which can prove that the observation by the permanent observatory with 8 feet at that time is credible.

In many cases, the accuracy of standard time measurement is directly proportional to the length of the watch. Guo Shoujing, an outstanding astronomer in Yuan Dynasty, designed and built a landscape observatory in the place where he visited Duke Zhou. It consists of a 9.46-meter-high platform and a long building tiled northward from the groove in the north wall of the platform. This platform is equivalent to a solid watch, and there is a "protractor" on the ground of Taipei, that is, Shi Gui. This huge "standard" greatly improves the measurement accuracy.

According to historical records, until the Ming and Qing Dynasties, time was measured by standard tables. At present, a standard watch at Nanjing Purple Mountain Observatory was made during the Ming Dynasty (1437~ 1442).

In ancient times, people worked at sunrise and rested at sunset. From the day when the sun rises and sets regularly, they intuitively felt the relationship between the sun and time, and began to determine the time through the position of the sun in the sky. But it's hard to be precise. According to records, 3000 years ago, Zhou Gongdan, the prime minister of the Western Zhou Dynasty, set up an instrument in Dengfeng County, Henan Province to determine the time by measuring the length of the sun shadow, which was called a standard watch. This should be the earliest timer in the world.

In addition, standard watches can be used for many purposes. During the Zhou and Qin Dynasties, people thought that if the length of the sun shadow between the north and the south on the same day was 1 inch, the distance between them was about 1 0,000 Li. It is said that this is the way the Zhou royal family used to seal Hou. The instrument can also determine the direction. Draw many concentric circles on the ground, and erect a watch rod at the center. When the vertex of the shadow falls on the same circle in the morning and afternoon, connect these corresponding points, and the connecting line between their midpoint trajectory and the center of the circle is the north-south direction. When you look at the North Pole through the top of the watch at night, this direction is also the north-south direction. When building houses, roads and palaces, the ancients should carefully determine the north-south direction (that is, the meridian direction). The Book of Songs says, "Take Sun as a slap and walk in the Chu room." Slap, guess the meaning. The whole sentence can be interpreted as: determine the direction of building Chu Palace by observing the shadow of the sun.

A sundial is a device that uses the shadow of the sun to measure time, also known as a sundial. It is an ancient timekeeping instrument in China that uses the shadow of the sun to measure time.

solar corona

The earliest sundial in the world was born in the kingdom of Babylon 6000 years ago. The earliest documentary record in China is the short shadow level invented by Yuan Chong in the 14th year of Sui Dynasty (574) mentioned in Sui Shu Tianwenzhi, that is, the horizon sundial. The clear record of the equatorial sundial was first seen in the shadow picture described in Volume 2 of Zeng Minxing's "Lonely Wake Magazine" in the Southern Song Dynasty.

A sundial usually consists of a copper pointer and a stone disk. The copper pointer is called "pointer", which passes through the center of the disk vertically and acts as a neutral rod in the standard table. Therefore, the coffin needle is also called "table" and the stone plate is called "coffin surface". It is placed on the stone platform so that the coffin surface is parallel to the equatorial plane, and the upper end of the coffin needle points to the north celestial pole and the lower end points to the south celestial pole. 12 cubes are engraved on the front and back of the brick surface, each representing 2 hours. When the sun shines on the sundial, the shadow of the sundial needle will be cast on the surface of the sundial, and the sun will move from east to west, and the shadow cast by the sundial needle on the surface will slowly move from west to east. The proportion of brick surface is uneven. Therefore, the moving shadow of the coffin needle seems to be the pointer of modern clocks and watches, and the coffin surface is the surface of clocks and watches to show the time. In the morning, shadows are cast near Shi Mao at the western end of the disc. Then, the shadow gradually becomes shorter and moves northward (below). When the sun reaches the highest position due south (upper meridian), the needle shadow is located due north (lower), indicating the local noon time. In the afternoon, the sun moves west and the shadow leans east, pointing to each hour in turn. From the vernal equinox to the autumnal equinox, the sun always runs on the north side of the celestial equator, so the shadow of the ray needle is cast above the ray plane; From the autumnal equinox to the vernal equinox, the sun runs on the south side of the celestial equator, so the shadow of the needle is cast below the surface of vernal equinox. Therefore, when observing the sundial, we must first understand the projection position of the sundial needle in two different periods.

This method of timing by sunlight projection is an important invention of human beings in the field of astronomical timing. This invention has been used by human beings for thousands of years. But the sundial has a fatal weakness, that is, it can't be used in rainy days and at night. It was not until 1270 that early mechanical clocks appeared in Italy and Germany, while China got two foreign clocks in 160 1. Therefore, it is still a modern thing to completely abandon the sundial and get to know Guang Chen by looking at the clock.

The sundial measured by the shadow of the sun has any form of hour hand. The angle between the hour hand and the ground plane must be the same as the local geographical latitude and point to the North Pole correctly, that is, there is a pointer parallel to the earth's rotation axis. By observing the projection of this pointer on the designated area, the time can be determined. Now the common sundial has the following different forms:

(1) horizontal sundial. It is the most commonly used sundial. It uses a horizontal scale. The inclination of the sundial axis is set according to the latitude of the place of use, and the scale needs to be calculated by trigonometric function. Suitable for low latitudes.

② Equatorial sundial. The equatorial sundial is a device that fixes the axis (hour hand) toward the north pole according to the latitude of the place of use, and judges the time by observing the scale of the axis projected on the disk perpendicular to the axis. The scales on the disk are equally divided, and the shadows of the summer and winter axes projected on the disk will be divided into the north and south parts of the disk, which is suitable for middle and low latitudes. If the disc is changed into a ring, it is called the equatorial compass sundial.

(3) polar caves. The plane projected by the pointer is parallel to the pointer, that is, the angle with the ground plane is the same as the geographical latitude and faces due north. The depiction of time can be handled by a simple geometric diagram, and the time axis of projection is a parallel line. Suitable for different latitudes.

(4) Southward vertical sundial. A sundial with a dial facing south and perpendicular to the ground. This sundial is suitable for mid-latitude (30 ~ 60) areas.

(5) East or west vertical. A sundial with the dial facing due east or west and perpendicular to the ground. This sundial can only be used in the first half (east) or the second half (west), but it is suitable for all latitudes in the world.

(6) Horizontal vertical type. The dial adopts a vertical sundial. This kind of sundial needs to be calibrated according to the direction of the building wall, so it is not easy to make. Depending on the season and time, sometimes there is no shadow. The sundials in the south and perpendicular to the east and west can be regarded as special cases of this shape.

(7) Projecting the sundial. Instead of setting an hour hand, just draw an ellipse with different flatness on the ground plane according to different geographical latitudes, depict the time line on it, point the long axis in the positive east-west direction, and engrave the date on the short axis in the north-south direction to indicate the correct position of the vertical rod to measure the time.

At the opening ceremony of the Beijing Olympic Games, an exciting scene of fireworks lighting the sundial was staged. As the clock approaches 20: 00, fireworks bloom over the "Bird's Nest". Suddenly, a dazzling fireworks rolled across the stadium, activating the ancient sundial. The sundial reflects the light onto the array in 2008, and the square array displays the countdown seconds with the sound of hitting. The huge scenes of 9, 8, 7, 6, 5, 4, 3, 2, 1 flashed on the surface, which was unforgettable.