Sun clock's watch

According to records, in the Spring and Autumn Period, a kind of clock named "Gui" appeared in China.

It consists of a ruler "reed" placed horizontally in the north-south direction and a benchmark "table" erected on the plane.

By measuring the length of the shadow, we can determine the noon time and calculate 24 solar terms. From the periodic changes of the surface shadow length, such as the time interval between the longest or shortest shadows of two consecutive days, the length (including days) of a tropical year can be determined, and it can also be calculated that the shortest shadow day is the summer solstice and the longest shadow day is the winter solstice.

The disadvantage of standard watch is that its timing accuracy is not high and its application scope is limited, so it can't measure time at night and on cloudy days.

Dengfeng Observatory is the earliest existing observatory in China, which consists of the observatory itself and the Shi Gui. It has been more than 700 years since Guo Shoujing, an outstanding scientist in Yuan Dynasty, was built as the national observation center at that time. Guo Shoujing used this observatory to compile the most advanced calendar at that time? Timekeeping calendar has been running for 360 years. The calendar calculates the length of a tropical year, which is only 26 seconds shorter than the actual time for the earth to go around the sun. At present, the universal solar calendar was formulated in A.D. 1582, which is consistent with the time-service calendar, but 300 years later than the time-service calendar in China. Dengfeng Observatory has attracted worldwide attention. The Observatory, Calendar and Guo Shoujing are the pride of the Chinese nation!