The sundial (rì guǐ) is a device that tells the time of day by looking at the position of the sun, and is a major invention of human beings in the field of astronomical timing, which has been used for thousands of years.
Sundials usually consist of dial needles (tables) and dials (scaled tables), using the direction of the sun's projection to determine and divide the time.
Sundial has two meanings, generally referring to the second meaning.
(1) "Day" refers to "sun", "dial" means "shadow", and "sundial" means "shadow of the sun".
(2) A device that uses the shadow projected by the sun to determine the moment, also known as the "day gauge".
Sundials usually consist of hands made of copper and discs made of stone. The copper needle is called "dial needle", vertically through the center of the disc, playing the role of a pole in the gui table, therefore, the dial needle is also called "table"; the stone disk is called "dial", placed on the stone platform, high in the south and low in the north, so that the dial is parallel to the equatorial surface of the sky, so that the upper end of the dial needle is just pointing to the north heavenly pole, and the lower end is just pointing to the south heavenly pole.
There are scales on both sides of the dial, molecular, ugly, yin, 卯, 辰, 巳, noon, unthinkable, Shen, unitary, 戌, 海 twelve hours, each hour is equally divided into "time beginning" and "time positive", which is exactly 24 hours a day. Most of the sundials display the sun when they look at the sun, and some have made design changes to show standard time or daylight to save time.
