Who invented the sundial?

The inventor of the sundial can't make a detailed textual research, but the sundial is rarely recorded in historical records. At present, the earliest record in historical materials is the section of History of Han, Records of Law and Records of Han: In Taishiling, Sima Qian suggested * * * that "the instrument of the sundial should be fixed, and the next moment will be delayed", while History of Han, Records of Arts and Literature.

Sui Shutian recorded the achievements of Geng Xu, saying that "observing the leakage of the sundial is the foundation of measuring the image of heaven and earth". Shi Ming Tian Wenzhi recorded the shape and timing of the sundial in detail. Compared with the standard watch, it is much more complicated and can be said to be a real instrument. By the Qing Dynasty, it could not only be used for timing, but also the sundial itself became a decorative work of art. ..

Extended data

Sundial principle: The principle of sundial timing is as follows. During the day, the shadows cast by objects illuminated by the sun are constantly changing. First, the length of the shadow is changing. The shadow is the longest in the morning. As time goes on, the shadow becomes shorter and longer after noon. The second is that the direction of the shadow is changing, because we are in the northern hemisphere, the shadow in the morning is in the west, the shadow at noon is in the north, and the shadow at night is in the east.

In principle, it can be timed according to the length or direction of the shadow, but it is more convenient to time according to the direction of the shadow. Therefore, the timing is usually based on the position of the shadow. Because the sundial must rely on sunlight, it can't be used on cloudy days and nights. Therefore, it is not enough to use the sundial to time, and other kinds of timers, such as water clocks, are needed to cooperate.

Placement of sundials: According to Ma Liping, an associate researcher at the National Time Service Center of the Chinese Academy of Sciences, there are many kinds of sundials, such as horizontal, equatorial and vertical. The equatorial sundial is the most important and common one in China, and also the most classic timekeeping instrument in ancient China. Dials made of sundial stone are called "dials" and should be tilted at a certain inclination according to the local latitude, so that the dials are parallel to the equatorial plane.

In Xi 'an, you should make the coffin face north, with the upper end of the coffin needle pointing to the north celestial pole and the lower end pointing to the south celestial pole. "That is to say, if you put it in the city wall and the moon city, you should not sit with your back against the watchtower facing south, but should sit facing north, with the coffin needle pointing north, at an altitude of 34.3 degrees (Xi 'an latitude).

Baidu encyclopedia-sundial instrument

People's Network-Nanmen Yuecheng sundial has not been adjusted for one year? Staff: It may have to be redone.