What is a "day"?
As early as the Han Dynasty more than 2,000 years ago, people have known our current "year, month and day", and the tool is the sundial, the most iconic image of the sundial is a round basin in the middle of the root pointer, the sun can leave a shadow on the dial, and this projection is like the hand of the clock on the dial, indicating the specific time, moving a circle is the sun haunting the day and night light and dark alternate once, so people know the "day".
Many ancient buildings in Beijing have sundials, such as the Beijing Ancient Observatory, which was built in the seventh year of the Ming Dynasty (1442) and was the national astronomical observatory of the Ming and Qing dynasties. The height of the ancient observatory is about 14 meters, the top of the platform is 20.4 meters long from north to south, and the length from east to west is 23.9 meters. There are 8 clean-made astronomical instruments on it.
In addition to the Chinese tradition in terms of shape, ornamentation, craftsmanship, etc., the 8 bronze instruments made in the Qing Dynasty also reflect the progress and achievements of large-scale astronomical instruments after the Renaissance era in Western Europe. They are historical testimonies to the cultural exchange between the East and the West. After the founding of New China, the ancient elephant platform was handed over to the Beijing Planetarium and is now a national key cultural relics protection unit.
Why is the day 24 hours?
Many people know that the twelve animal heads of the Yuanmingyuan are fountains, but few people know that it is a huge hydraulic timer, each animal is a fountain mechanism, every hour, that is, the current two hours, the corresponding animal mouth will spray water, when all the animals are sprayed with water, a day and a night will pass.
Why 24 hours? The so-called hour is the 12 phenomena that our ancestors summed up after observing the natural activities caused by the sun's haunting.
For example, from 23:00 p.m. to 1:00 p.m., rats are frequently infested, so the beginning of the day is named "sub-time" to "rats", forming the "sub-rats" in the zodiac. There is a corresponding natural phenomenon every two hours.
Which is faster, "immediately" or "suddenly"?
The engraving leak is the result of the ancient people being inspired by the leak of the container. "Carved" refers to this scaled floating arrow in the bucket. After the water flows out of the leaky pot, the floating arrow changes with the rise of the water surface of the receiving bucket, indicating the passage of time.
The ancients used 100 grids to divide day and night, and each grid was a quarter of an hour, that is, 14 minutes and 24 seconds.
And between the two moments there is also a symbol that is difficult to see with the naked eye, a line as thin as spider silk, that is, "suddenly", the water level changes slightly, and the "sudden" passes, which is shorter than the time of "seconds", so the word "suddenly" is derived from it.
What time is "three changes in the middle of the night"?
Since the Yuan Dynasty, Beijing has begun to use the "morning bell and twilight drum" to tell the time. In the past, when it came to hours, the night was called more, and one was equivalent to the current two hours, and every time there was a change, the bell had to be rung.
From 7 p.m. to 9 p.m. is a more day, and so on, the three more days refer to the period between 11 p.m. and 1 p.m., and the word three more in the middle of the night is also how it comes from.
The evolution of timers
The gui watch and sundial are one of the earliest timers used by ancient humans, both of which use the length and direction of the sun's projection to judge time.
The Gui table measures the number of seasons and days of the year according to the length of the shadow of the sun, and calculates the calendar.
Both sides of the sundial have scales, molecular, ugly, yin, 卯, 辰, 巳, noon, undo, Shen, 酉, 戌, 海 twelve hours, each hour is equally divided into "time beginning" and "time positive", which is exactly 24 hours a day.
What should I do if I encounter a cloudy day or night? - Missing engraving
The invention of leaky engraving is the result of the ancients being inspired by the phenomenon of water leakage in containers. In the early Neolithic period, mainland ancestors were able to make pottery. Pottery will inevitably have broken cracks when used, and some pottery containing water may leak due to damage, and the loss of water has a certain correspondence with the passage of time. Over time, the ancients developed the concept of measuring time in this way.
The leak uses the principle of water equalization and dripping to observe the data displayed on the engraved arrow in the pot to calculate the time. As a timer, the use of missed engravings is more common and longer than sundials. Before the introduction of mechanical clocks to China, the missing engraving was also the most common timer used in the mainland.
Of course, there were also very complex timers in ancient times, such as the one on the map.
The earliest appearance of the Western hourglass was in 1100 AD, and the specific principle is the same as that of the leaked engraving. The convenience of the hourglass is that it can be reversed to continue the timing, but it is not as accurate as the omission.
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