What was the earliest timing tool?

The earliest timekeeping instrument used by human beings is to judge time by the projection length and direction of the sun. The former is called a standard watch, which is used to measure the time between Japan and China, determine the season and identify the direction; The latter is called a sundial and is used to measure time. Both are collectively referred to as sun clock.

From BC 1300 to BC 1027, the use of standard meters was recorded in Oracle Bone Inscriptions during the Shang Dynasty in China. There is an article in the Book of Songs, National Style and Prescriptions, "Prescriptions were written in the Chu Palace. Slap in the sun and do it in the Chu room ... ". The exact record of using standard watches is 659 BC.

Sun clock, such as standard watches, will fail on cloudy days or at night. To this end, people have invented time-measuring instruments such as clepsydra, hourglass, oil lamp clock and candle clock. A sundial, a sundial. The "table" in the standard table is a pole or stone pillar standing vertically on the ground; "Gui" is a slate extending horizontally from the heel of the watch to the north. Whenever the sun turns due south, the shadow falls on the water of Guiyu. By measuring the length of the shadow, we can calculate the time of each solar term, such as winter solstice and summer solstice. When the shadow is the longest, the solstice of winter comes; In the shortest time, the summer solstice came. It is the oldest and most common astronomical instrument in China.