Encyclopedia of popular science knowledge: "Time Knowledge"

Chapter 3 All kinds of clocks (3)
Ancient my country made outstanding contributions to the development of water clocks.The most famous example is the "Water Transport Observatory" designed and manufactured by Su Song in the early Northern Song Dynasty (about 1 AD).

The water transport instrument platform is 3 feet 5 feet 6 inches 5 minutes high (about 12 meters) and 2 feet 1 foot wide (about 0.33 meters). It is a 3-story wooden structure building with a narrow top and a wide bottom.The whole station is composed of water bucket, wooden wheel, hook-shaped iron dial, etc. to form a transmission system.It is powered by water and is a complex astronomical instrument.Its timing part, formerly known as "day and night machine wheel", is an exquisite water clock.Here, Su Song used a row of clips and a pivot lever device, which is equivalent to the escapement in modern clocks, to control the running speed of the pivot wheel that rotates the bucket through the meshing of large and small gears.There are 5 floors of wooden pavilions in the whole timing part.The first layer is the drum wheel of the day and night clock. There are three small wooden pillars of different heights on the wheel (acting as a cam), which can be used to toggle the dials of the three wooden figures on time, pull the arms of the wooden figures, beat the drum at one moment, and ring the bell at the beginning of the day. It was time to ring the bell.The second layer is the wheel for the beginning of the day and night, and there are 3 wooden figures beside the wheel, which represent the beginning and the right time of 3 hours, which is equivalent to 34 hours.The 12 wooden men on the wheel appear in front of the wooden pavilion door on time as the wheel turns.The third layer is the engraved Sichen wheel, and there are % Sichen wooden figures beside the wheel, and one person appears every moment.The fourth layer is the Yeleu golden gong wheel, which can pull the wooden man to hit the gong in sequence and report the number, and it can be adjusted according to the season to adapt to the change of day length and night length.The fifth floor is the Yelou Sichen wheel. There are 24 Sichen wooden figures beside the wheel. The positions of the wooden figures can be changed according to the seasons, and they are arranged in order from sunset to sunrise.

Su Song presided over the manufacture of this astronomical observatory, which not only inherited the achievements in astronomy and mechanics since the Han and Tang Dynasties in my country, but also innovated.The day and night machine wheel is the earliest astronomical clock in the world, and the escapement it uses is also recognized as the ancestor of the world's mechanical clocks.

However, the invention of Su Song and others did not receive the support and encouragement of the feudal dynasty.At that time, a Hanlin used the theory of Yin-Yang and Five Elements to criticize and obstruct the manufacture and installation of ritual images.He said nonsense that the Song Dynasty ruled the world based on the virtue of fire, and the name of this ceremonial platform is Water Transport, which is not an auspicious omen for the country, because water can overcome fire.His memorial was sent to the emperor, and the emperor listened to the slander and ordered to cancel the word "water transport" and change the name to "Yuanku armillary sphere image".

, and let it be placed in the southwest corner of the capital (now Kaifeng, Henan), because according to them, the west belongs to gold and the south belongs to fire, and the attack of gold and fire can calm water.This is really ignorant and absurd!
Later, the Jin soldiers captured Kaifeng, and the Northern Song Dynasty perished.This outstanding astronomical clock was captured by Jin Bing and moved to Beijing.However, due to continuous wars and disordered order, this great invention has not been popularized and applied, and has been stagnant for a hundred years.

Su Song's water clock can be said to be the earliest mechanical balance wheel, and it is the earliest known attempt to use the period of mechanical motion as a timekeeping standard.Since it is timed by running water rather than by the movement of the mechanical device itself, it can also be regarded as a transition from steady running water to mechanical vibration.

With the Crusades, Chinese clock-making technology spread to Europe, stimulating Europeans to create similar devices.Of course, a wise man, once he knows how something is made, can often find his own way of making it.In a strictly technical sense, a water clock differs fundamentally from a mechanical clock only in that the former involves a continuous process (water flowing through an orifice), while the latter is controlled by a constantly repeating mechanical movement.We are not saying that the mechanical clock, especially the escapement, invented by Europeans around the 13th century was completely copied from China.There are differences between them, for example, Europeans do not use pivots and timing levers, but arbors and crown gears to control the movement of clock mechanisms.But the principle they are based on comes from China, which is a fact that most Chinese and foreign scientists admit.

The invention of the mechanical clock was the decisive step towards the universal acceptance of the 24-hour system, which divides day and night into equal lengths, in Europe.In Milan, Italy, a public clock was set up in 1335 to tell the time 1 hours a day.

The clock speed of early mechanical clocks depends on the driving wheel, and the driving wheel is affected by the change of friction in the power mechanism, so the accuracy is very low, with a difference of more than 1 quarter of an hour per day.

Dividing 1 hour into 60 minutes and 1 minute into 60 seconds was proposed around 1345 to represent the cycle of a lunar eclipse.But this is only limited to theoretical calculations, without actual measurement. As late as the middle of the 17th century, mechanical clocks had only one pointer, and there were only hour and quarter hour scales on the clock face.

Despite the advent of mechanical clocks, the development of the scientific concept of time was severely hampered by the lack of an accurate method of measuring short periods of time.

Invention of the pendulum clock

It was the great Italian scientist Galileo who made a major contribution to improving the early mechanical clocks.He discovered the isochronism principle of the pendulum.Regarding the principle of isochronism, we can simply explain it as follows:
When the pendulum (single pendulum) gains a certain amount of kinetic energy, it moves from the rest position "0" to the position "1", the pendulum continues to rise, and after reaching the highest point "1", the speed is zero; then it moves downward under the action of gravity. down exercise.When it passes through "0", its speed is the highest, and then it swings to position "2", and when it reaches the highest point position "2", its speed is zero, and then it swings back under the action of gravity.

Experiments have proved that every time it swings for a week, the time it takes is equal, which is called the isochronism principle of the pendulum.

The uniform swing of the pendulum is a real artificial periodic motion discovered after the hourglass.Since the early 17th century, Western craftsmen have applied it to clocks as a stable "timer", enabling mechanical clocks to indicate "seconds", thereby increasing the timing accuracy by nearly 100 times.

With the development of social productivity, the world's first timer using gear machinery was born.The earliest is the "Water Transport Instrument Platform" invented by Su Song and others in the Song Dynasty of our country. It is called "Su Song Bell" internationally, and its timing is very delicate. In 1955, Derek Ding Desola Putons and Joseph Needham, professors of the University of Cambridge, believed that Su Songzhong was the originator of modern astronomical clocks when they traced the clock's family history.

The pendulum clock was invented in the 17th century.According to legend, when the Italian astronomer Galileo was young, when he went to a church to read the Bible, he saw the chandelier on the cathedral swinging.He counted the number of beats of his own pulse to measure the swing time of the chandelier, and found that the time for the chandelier to swing back and forth is the same, that is, the swing period remains unchanged. This law is called the isochronism of the pendulum.Later, Galileo designed the pendulum clock in 1640 based on the isochronism principle of the pendulum.Although its structure is simple, the current pendulum clock is developed from it.

The first person in history to make a practical pendulum clock was Huygens in the Netherlands.A pendulum clock he made in 1656 was more accurate than any clock at the time.Two years later, in 1658, British scientist Hooke made a pocket watch with a balance wheel. In 167, the pocket watch made by the Englishman Denisole Lecan had two hands (hour hand and minute hand) with a surface diameter of about 6 cm, which was easy to carry.

The original clock had only one hour hand, the minute hand was added around 1550 A.D., and the second hand did not appear until 1760. The appearance of 3 needles shows that the watchmaking technology has been greatly improved.

The most accurate clock is the astronomical clock on the observatory.There are several kinds of astronomical clocks, the most famous ones are the Riverlier clock and the Sauter clock.Ordinary pendulum clocks are placed in the air. Due to changes in air temperature, air pressure, humidity, etc., the swing period of the pendulum will be affected, making the clock not so uniform and accurate.The Riverrell clock is housed in a glass jar from which most of the air has been evacuated (vacuum) to reduce the effects of changes in air pressure.Then put the clock in a deep basement, where the temperature change does not exceed 1 degree throughout the year, which can make the clock run very evenly.The Riverlier clock changes by about 1/100th of a second in a day and night.

A more accurate astronomical clock was that invented by Short in 1920 (called the Short clock).It is characterized by two pendulums.One is the free pendulum, which controls the pendulum of the secondary clock, forcing it to swing in time with itself.The pendulum of the secondary clock is connected to the watch mechanism to indicate the time.The error of the Shao Te clock for a day and night is about 1/1000 second.Sauter clocks are considered the best of mechanical timepieces.

Astronomical clocks are stored in basements with constant temperature and pressure, and people do not easily go there (because human body temperature and breathing will change the temperature in the basement), so how do you know the time?It turns out that the astronomical clock has another clock face, which is connected with the master clock working in the basement by wires. You only need to look at the working clock on the ground to know the time, which can be said to be "one mind at the same time".

The accuracy of the Sauter clock is very high, and people have used it to discover the inhomogeneity of the earth's rotation.But it is not the highest, and it is also afraid of shocks, and a small earthquake will stop the pendulum clock or go inaccurately.

electronic clock
After people mastered the oscillation characteristics of electricity, they began to use the oscillation of electricity to make clocks and watches.

The outstanding feature of electronic clocks and watches is that the vibration of electricity determines the accuracy of travel time, and even completely replaces the balance spring and balance wheel in mechanical watches.And replace the original mechanical clockwork with electric energy.Generally speaking, human timing tools can be divided into two categories, one is mechanical clocks and the other is electronic clocks. The crystal clocks and atomic clocks we will talk about later can be regarded as advanced electronic clocks.Here we first talk about electronic watches that have begun to be widely used in the world.

We are more familiar with ordinary watches, but electronic watches are a little strange.Electronic watches are a bright new flower in the watchmaking industry.A new type of electronic watch has 6 digits on the surface, which respectively display hours, minutes, and seconds. When a knob is pressed, the hours, minutes, and seconds on the surface immediately change to month, day, and week.It can also automatically determine 28 days, 30 days or 31 days according to the corresponding month.When looking at the watch at night, just press another knob, and the small light inside the watch will glow, illuminating the numbers on the surface, which is very delicate.

Among their "watch brothers", the electronic watch is the one with the shortest qualifications, but its development is very rapid. Since the first generation of electronic watches were made in Switzerland in the middle of the blade era, in just over 20 years, there have been After 4 generations of evolution.

The original electronic watch, that is, the first generation of electronic watch, is the product of the combination of electronic watch and mechanical watch, with balance spring and electric oscillation coexisting.However, the accuracy of travel time is no longer determined by the balance wheel of the hairspring, but by the oscillation of electricity.Because there are hairsprings and balance wheels, the first generation of electronic watches is called "hairspring balance wheel electronic watches".

The basic working principle of the first generation of electronic watches is this: a tiny battery powers a transistor oscillator, which generates and maintains oscillations.During the oscillation process, the magnetic field of the inductance coil changes periodically, acting on the permanent magnet on the balance wheel, pushing the balance wheel to make it swing back and forth according to the period of the magnetic field change (that is, the oscillation period), and then drive the pointer through the gear system Turn to indicate the time.

The first generation of electronic watches is still very rough, and its travel time error is about 15 seconds per day. Compared with mechanical watches, there is no great advantage, but it is a new thing with great vitality. Continuously develop and improve.

On the basis of the first generation of electronic watches, a second generation of electronic watches appeared, called "tuning fork electronic watches".

We know that in the first generation of electronic watches, the frequency of oscillation is mainly determined by the capacitance and inductance of the circuit, and their values ​​are still not stable enough. For example, like in mechanical watches, temperature is a very important factor.In order to improve the timing accuracy, it is necessary to stabilize the oscillation frequency as much as possible, so people try to find a way to stabilize the oscillation frequency. As a frequency stabilization component, the "tuning fork" is first used.

(End of this chapter)