Brief introduction of sundial

The sundial has two meanings, generally referring to the second meaning.

(1) The sun refers to the sun, the sundial refers to the shadow, and the sundial refers to the shadow of the sun.

(2) A device that uses the shadow cast by the sun to determine the time, also known as a heliograph.

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 needle is also called "table"; The stone disc is called "tile surface" and placed on the stone platform, with the south high and the north low, so that the tile surface is parallel to the equator of the celestial sphere. In this way, the upper end of the magnetic needle points to the north celestial pole and the lower end points to the south celestial pole.

There are scales on both sides of the coffin. Molecules, Ugliness, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai have twelve hours, and each hour is divided into "the beginning of the time" and "the right time", and a day is exactly 24 hours. Most sundials show apparent solar time, and the design of some of them has been changed to show standard time or daylight saving time.

The history of human use of sundials is very long. Babylonia was used 6000 years ago in ancient times, and China was used in the Zhou Dynasty more than 3000 years ago.

The sundial can display not only the time of day, but also the solar terms and months. Of course, its shortcomings are also obvious. It is huge and cannot be used when there is no sunshine, such as cloudy days and cloudy nights.

This invention has been used by human beings for thousands of years. It was not until 1270 that early mechanical clocks appeared in Italy and Germany, while in China, it was not until 160 1 year that Emperor Wanli of the Ming Dynasty got two foreign chimes. Although there were many imported and homemade clocks and watches in the Qing dynasty, they were all used by the palace, and ordinary people still watched the dawn.