Encyclopedia of popular science knowledge: "Time Knowledge"

Chapter 1 All kinds of clocks (1)
ancient timekeeping method

When human beings first left the animal kingdom, it was difficult to have any sense of time.They can only gather and hunt during the day, following the arrangement of the sun. "Work at sunrise and rest at sunset", which gave them a hazy concept of "day" from the beginning.Common human activities require a longer time unit.To make a stone axe or a bone needle, primitive people often need quite a lot of time.So, how did they count the days?
In ancient times, we had a method of "carving wood to record the day", that is, to engrave bamboo or wooden boards to count the days.For example, if A and B have made an appointment to meet in a certain place 10 days later, how can they avoid making mistakes?When they agreed, they found a small piece of wood, carved 10 slits on it, and then cut it vertically into two pieces from the middle, just like the "letter of introduction" and the "stub", and A and B each hold one half.

Every day, they cut off one frame, and when the 10 frames are cut off, that is when they meet.This primitive method of keeping a diary was later adopted by prisoners in prisons. They often draw a mark on the wall or on the ground after a day to calculate the time spent.

The Ancients Carved Wood to Meet
There is also a primitive method of "knotting the day": people tie knots on a long rope to count the days.For example, if someone wants to go somewhere far away, he will put a rope around his waist, and after setting off, he will tie a knot before staying at night.

Tie a knot every day of walking, and when he reaches his destination, he can know how many days he has walked this time from the number of knots on the rope, and from this he can estimate the distance of this place.When he is ready to go home, he will walk for a day on the return road and untie a knot. When all the knots on the rope are untied, he should go home.

The method of "knotting the day with a knot" later evolved into a common saying: "Tie a knot in the belt of your trousers—and remember it."

For a longer period of time, the ancients counted the days by throwing stones into the earthen basin.For example, every time there are 10 knots in the rope, they throw a small stone (and untie the knot at the same time), so that in the end, it can be calculated from the number of stones and knots how many days have passed.

This method of throwing stones to remember the date was even used in some places in our country until the founding of New China. For example, in the Miao area on the southwestern border of our country, they counted the years in this way before liberation.When the moon is full, throw a pebble into a bamboo tube, and when there are 12 pebbles in it, pour them out and replace them with a big pebble—meaning it has been a year.

Later, people not only noticed the rising and setting of the sun in the east, but also gradually discovered the law of the coming and going of cold and summer.The wind and snow in winter and the scorching sun in summer not only make them feel the changes in the environment, but also have a major impact on their gathering and hunting activities.After entering the agricultural society, people finally gradually realized the concept of "year".my country has carefully observed phenology for a long time, such as when willows vomit green, when voles come out of their holes... In the Wusuli River Basin in our north, the ancients couldn't figure out their own age, but they had eaten marijuana several times. Harmony came to "discuss seniority".Because this delicious sea fish only returns to the Ussuri River to lay eggs in September and October every year, people who have eaten fish 40 times must be older than those who have eaten 20 times, and should be respected more.

The ancients in northern my country calculated their age by dividing the number of times they ate fish. The ancestors of the Mongolian people in our country lived on the prairie and lived on animal husbandry, so they often used the dry and prosperous prairie as their year.They call a few years old "Jiqing" or "Qingcaojidu".The customs of the Qiang people in Yanchang are described in ancient Chinese books (Wei Shu): "There are no words in the vulgarity, but we can remember the age by waiting for the vegetation to grow and die."

The regular and menacing flooding of the Nile helped the ancient Egyptians to determine the length of the year for the first time.Around the 20th century BC, they discovered that the sun rose and fell an average of 365 times between the river's rising and falling.Therefore, ancient Egypt set a year as 365 days very early.

But what is interesting is that the Egyptians used a fixed "calendar" with 12 months per year and 30 days per month.This calendar has only 360 days in a year.So at that time, the last five days had no "place" in the calendar.During those five days, the Egyptians closed their doors, did not contact with others, and sent it away in a daze or in a deep sleep... A day is longer, but how is the time of an hour determined? What about?It was found that it is more accurate to judge the time according to the length of the shadow cast by the sun on the ground objects.

Shadows such as trees, houses, and objects.In the morning, the shadows are longer; at noon, the shadows are the shortest; in the evening, the shadows grow again.

There is a letter written by an ancient Egyptian to Princess Bologna: "When your shadow grows 16 steps, Amasis is waiting for you in the olive grove..." In an ancient Greek comedy, there is An Athenian woman said to her husband: "When the shadow is 10 steps long, you can eat with sesame oil!"

What does the shadow 16 steps and 10 steps mean?It turns out that in ancient Egypt and Greece, there were stone tablets or monuments built in many places.During the day, when the sun rises in the east and sets in the west, the monument casts shadows one by one.People only need to measure the shadow with their feet to know what time it is.

old sun clock

In the 7th century BC, our ancestors invented the gui watch, which is an instrument that uses the shadow of the sun to measure time.A gui watch of the Han Dynasty unearthed in Yizheng, Jiangsu, is composed of a 19.2 cm long vertical "table" and a 34.39 cm long "gui".

There are scales on the gui, marking the size.When Biao and Gui are put together, they are like a ruler.When in use, stand the watch upright, put it in the sun, and let the shadow of the watch cast on the flat Gui, and you can know the length of the shadow.Guibiao can not only measure the time, but also calculate which season it is at that time.

There is an ancient sun clock in the Hall of Supreme Harmony in the Forbidden City in Beijing.It is called sundial (guǐ), which is another instrument that uses the shadow of the sun to measure time.This kind of instrument is to erect an iron needle in the middle of a circular stone slab, with 12 hour marks engraved on the surroundings. As the sun rises in the east and sets in the west, the time can be known according to the position of the needle shadow.

The sun emits light and heat, all things grow, and the earth is full of vitality.People worship the sun and regard it as a god.The emperor's sacrifices and human life are all based on the position of the sun.The sun naturally became the ancient clock.

No wonder all countries have invented the "sun clock" in unison.The Greeks made many different sundials, some with the shadow of a rod resting on a vertical wall, others on a spherical, conical, or cylindrical surface.As the sun moves in the sky, the shadow of the pole also moves accordingly, and the end of the shadow points to the scale on the dial, so you know what time it is.There are some ancient milestones in Russia. In the center of a stone slab, there is a triangular iron plate, with Roman characters engraved around it, marking the time.As the sun moves across the sky, the shadow of the iron sheet moves like a clock hand, indicating what time it is.

Most of the sundials are fixed, and it is not very convenient to use, and it is impossible to take it on a trip.The monk Huazhai in India made a multi-ribbed walking stick to solve this problem.It is octagonal and each side represents a season.Each side of the top is pierced with a hole into which a small wooden peg can be inserted, and a mark is engraved on the plane in advance according to the length of the shadow of the wooden peg—time.It is both a cane and a clock.During the day, if you want to know what time it is, just pick up the rope on the top, insert a small wooden peg into the small hole (the surface of the hole should be suitable for the season at that time), and look at the projection of the wooden peg to know what time it is up.

Not only the "sun clock", but also the wonderful "sun alarm clock"!An earthen cannon ignited with gunpowder wire, a convex lens is placed on the fuse, and when the sun's rays pass through the lens and focus on the fuse, the gunpowder wire is ignited, causing the cannon to roar, and it reports the time to people. "Sun alarm clock" is a step further than "sun clock". In addition to measuring time, it is also an ancient method of telling time.

clepsydra
Before the Spring and Autumn Period, my country invented the clepsydra (also known as the pot leak, engraved leak and copper pot drip).A clepsydra is a water timekeeping instrument.Its structure is different in different dynasties, but the basic principle is the same.

For example, a kind of clepsydra in the Qing Dynasty: the top three pots have water leakage holes at the bottom, and the pots are filled with water during the day, which leaks into the kettle one by one.The depth of the above two pots is reduced by one inch, so that the water volume of the flat pot can be always full.There is a hole above the rear wall of the flat kettle. If there is too much water, it can leak from here to the receiving kettle below, so that the flat kettle can keep a certain amount of water in a certain period of time and leak into the kettle.There is a bronze figure in the kettle, holding a leaky arrow that can move up and down, and the time measured by a ruler is engraved on it.A floating boat is installed on the lower end of the missing arrow to float on the water.The water in the kettle gradually fills up, and the time can be known from the rising position of the leaking arrow.

After the Han Dynasty, Liang Lingzan and a group of monks in the Tang Dynasty of our country used water power and gears to create ingenious timing tools: waterborne armillary spheres and timers.Another kind of water instrument platform was made by Song Dynasty astronomer Su Song. It is about 3 feet high and has 7 floors up and down.The second layer is equipped with a kind of celestial globe, with a hemisphere exposed, indicating that half is on the ground.The other hemisphere is hidden below the horizon, and it operates automatically day and night.

Among the five-storey wooden buildings below, there are three doors on the first floor. At the beginning of each hour, a wooden man in red will ring the bell on the left door; Bell; every time, the wooden man in green is beating the drum in the middle.On the second floor, at the beginning of the hour, the wooden man holding the time telling card will appear at the middle gate.When the special report was engraved on the third floor, a wooden figure holding a sign would also appear at that time.

The wooden man on the fourth floor rings the bell to announce the time of night, and rings the watch.The wooden man on the fifth floor reported the sunrise and sunset.

Guo Shoujing in the Yuan Dynasty specially made a time-telling instrument, which is similar to the time-telling device in the Song Dynasty. The difference is that it is equipped with four spirit animal models such as dragon, tiger, red bird, and turtle, which will jump when the time comes.

It can be seen that the ancients already knew how to use a ruler to measure continuous time. No wonder there is a folk saying: "An inch of time is an inch of gold." That is to say, time can be measured by "inch".

The clepsydra has a shortcoming. Whenever it is cold, the water freezes and cannot operate. People use sand instead of water and become a "sand clock".It is a cylindrical wooden vessel made of three pillars, with two flask-like glass bottles placed in the middle.The bottom is big and the mouth is thin, and the mouths of the two bottles are opposite to each other, connected by fixed objects, and one bottle is filled with clean sand.To start the "clock," just turn it upside down.The sand in the upper bottle leaks down. When all the sand grains leak into the lower bottle, a shorter time can be measured: 3 minutes or 10 minutes. Every 30 minutes, people only need to turn the "sand clock" bottle upside down. , The clock "goes" again!

Schematic Diagram of Hourglass in Yuan Dynasty Copper Pot

In the Ming Dynasty, Zhan Xiyuan created a "five-wheel hourglass", which is a mechanical clock specially for telling time.There are 16 sand buckets on the primary wheel. When the sand in the sand pool is continuously leaked into the bucket, the primary wheel is pressed to rotate, and the second, third, and fourth wheels are respectively driven by the pinion, and finally transmitted to the horizontally rotating middle wheel.The long axis of the middle wheel passes through a viewing disk, and a pointer is installed on the top of the long axis, which rotates with the long axis. The time is engraved on the viewing disk, and the place where the pointer turns is the time at that time.The special device on the middle wheel drives the two wooden figures on both sides of the viewfinder to ring the bell on time to report the time.

Fantastic book clock and fire clock
In the Middle Ages, churches had to ring the bell regularly every day to summon the priests to pray.There was a black priest named Augustine who was in charge of ringing the bell in the church.The days were especially sad because there was no clock.Every night, at three o'clock after midnight, he would ring the bell to wake the priests up for morning prayers.He came up with a simple solution: he began to read the "Bible Old Testament" from the evening, and when he read the sentence "Asaph's friend and actor Ijii Moff", he ran to the clock tower Go up and ring the bell.

Once, when Augustine was studying, because he was very tired during the day, he fell asleep in a short while.When he woke up, the sun had already risen high in the sky.Of course, he could only be reprimanded by the head of the church, Dezidry!
"Book clock" is not an accurate time, because when reading, some people read faster, while others read slowly.This will result in unequal time, you have your time, he has his time.However, people require that any time unit should be the same!
"Book Clock" was wrong.Because the residents of the town near the church did not hear the bell, when they woke up, it was already high in the sun.Therefore, the "book clock" is also unreliable.

People thought of another "fire clock".The candle is marked with a size mark, that is, the time is determined by the amount of the burned candle. The "fire clock" is very convenient and common to use.people ask:

"What time is it?" The answer is: "One candle", or "Two candles".One night is divided into 3 candles. If it is now "two candles", it means that 2/3 of the night has passed.You can measure the time a little more precisely by marking the ruler on the candle.Another kind of oil lamp, the time can also be measured according to the amount of oil consumed in the lamp.

This kind of fire clock, due to the thickness of the candle, the height of the burning point, the size of the flame, etc., the measurement time is not very accurate.

In ancient my country, there was a kind of "fire alarm clock".There is a dragon boat-shaped boat, the hull of which is hollowed out with long wooden blocks, carved with dragon head and tail patterns, and a thin long incense stick is placed in the middle.A thread is hung horizontally in the middle of the boat, and a small steel ball is tied to each end of the thread. People light one end of the long incense.When the long incense burned to the thread, the thread was cut by the fire, and two small steel balls fell into the metal basin under the side of the boat, making a jingling sound.

欧洲人向来是按照教堂的钟声来安排他们一天的工作。一天敲钟8次，每隔3小时一次。晨祷以后，就是教堂第1时（相当于上午7～9时），以后第2时、第3时……每隔3小时敲一次钟。

It is conceivable that water clocks, fire clocks, book clocks, etc. have difficulties and errors in measuring time, and if there is a mistake in one link, many things will be messed up.Some churches simply stipulate that the bell for the first morning service should be rung according to the rooster crowing in the middle of the night.

The advent of the mechanical clock
Clocks and watches can keep the results of time measurement, which is called "punctuality".The instrument of punctuality is usually a clock.

After the water clock and the sand clock, people invented the mechanical clock.There is a pendulum for everything from vintage wall clocks to tiny, quick-swing watches.Only a pendulum that keeps moving can indicate the time and make the clock go accurately.

Who invented the pendulum?How was the world's first clock that used the vibration of a pendulum to keep time made?

In 1583, in the city of Pisa, Italy, a young man named Galileo went to church to worship.He saw a copper lamp hanging from the roof by ropes was blown by the wind, and the lamp was slowly swinging back and forth.This wobble is a natural phenomenon that exists commonly.It has not attracted people's attention for a long time, but Galileo has grasped this phenomenon: the swing is smooth and uniform, is the time of each swing the same?There were no clocks at that time, so there was no comparison.

Later, in class, the teacher said: "Generally speaking, the number of people's pulse is stable."

This gave Galileo a revelation: Can the pulse be used to measure the swing period of that chandelier?
When he prayed again, he counted the number of times silently by pressing his own pulse with his fingers, and at the same time carefully observed the swinging of the chandelier back and forth.He found that with the swing of the lamp, the time was always the same every time it was experienced.Although the amplitude of the swing will become smaller and smaller until it is completely stationary, the time it takes to swing once does not decrease.The experiment also found that the shorter the rope, the shorter the time for each swing.He finally discovered that the swing period and amplitude of the pendulum have nothing to do with the isochronous law of the swing of the single pendulum.

Galileo wanted to use a pendulum to indicate time. Due to the prevalence of religion, the spread of scientific truth was imprisoned.Galileo failed to do so.

In 1656, the Dutch scientist Huygens made further research on the isochronism law of the simple pendulum discovered by Galileo, and made the world's first clock that uses the vibration of the pendulum to keep time.

This pendulum clock is roughly divided into two structures: a swing part and a count part.The counting part usually adopts pointer and dial digital display.The mechanical clocks manufactured using this principle have been used in the world for more than 300 years.

Why does the pendulum swing?This has something to do with the attraction of the earth.When the pendulum is out of balance in position, gravity and the pull of the string are not in line, creating a force that returns the pendulum to its equilibrium position, causing the swing.The cycle of simple pendulum movement is related to the gravitational force of the earth, therefore, the pendulum must be in the same place with the same gravitational gravitational force, so that the pendulum can have isochronism.

Early mechanical clocks were made larger.There is a huge clock in the Houses of Parliament in London, England - Big Ben.Big Ben has four clock faces, one on each side of the quadrangular tower, each 8 meters in diameter.Its minute hand is 3.5 meters long, the numbers on the clock face are 75 centimeters high, and the pendulum weighs 200 kilograms.

In order to improve the clock and make it more delicate, people thought of an elastic object, because the swing of a simple pendulum is a kind of vibration, and the spring can vibrate freely.It has been found that the frequency of a spring with a certain structure is always constant. According to this principle, a balance spring is produced.The balance spring is a helical spring that rests on the balance shaft at one end and a fixed metal plate at the other end.Pushing the balance wheel to the left or right, the hairspring is sometimes tightened and sometimes unwound.With the balance spring, people made pocket watches and wristwatches.

In order to make the watch go accurately, people continue to improve it.Diamonds are installed on the rotating shaft of the watch to reduce wear and tear and make the life longer. Watch manufacturers have paid attention to shockproof, waterproof, and antimagnetic performances, and invented automatic watches, calendar watches, and quick-swing watches.Whether the watch runs accurately or not is related to the period of the balance spring. The shorter the period of the balance wheel, the faster the movement and the more accurate the movement.People make fast-swing watches, the balance wheel swings back and forth 6 times per second, which is twice as fast as ordinary watches. It goes on for a day, and the error is only about 6 seconds.

Electric Clocks and Electronic Watches
(End of this chapter)