The invention of pendulum clock
We know that it was the great Italian scientist Galileo Galilei who made a great contribution to the improvement of early mechanical clocks. He discovered the isochronous principle of pendulum, and the isochronous principle can be explained simply as follows:
When the pendulum (simple pendulum) obtains a certain kinetic energy, it moves from the static position "0" to the position "1", and the pendulum keeps rising. After reaching the highest point "1", the speed is zero; Then it moves downward under the action of gravity. When it passes through "0", its speed is the maximum, and then it swings to position "2". When it reaches the highest position "2", its speed is zero, and then it swings back under the action of gravity. Experiments have proved that every time it swings, the time it goes through is equal, which is called the isochronous principle of pendulum.
The uniform swing of pendulum is a real man-made periodic motion found after dripping. Since the early 17th century, Western craftsmen have applied it to the clock as a stable "timer", so that the mechanical clock can indicate "seconds", thus improving the timing accuracy by nearly 100 times.
With the development of social productive forces, timers that use gear machinery in the world were born. The earliest one is the "water transport platform" invented by Su Song and others in the Song Dynasty. Internationally, it is called "Su Song clock", and the timing is very exquisite. In 1955, Professor Derek Ding desola putons and Joseph Needham of the University of Cambridge, England, when tracing the family history of the clock, believed that Su Song clock was the ancestor of modern astronomical clock.
The pendulum clock was invented in the 17th century. It is said that when Galileo, an Italian astronomer, was young, he once went to the church to recite scriptures and saw the pendulum clock on the Bishop's platform swinging. He counted the number of times his pulse beat to measure the period of the pendulum swing back and forth. He found that the time of the pendulum swing back and forth is the same, that is, the swing period is unchanged. This law is called the isochronity of the pendulum. Later, Galileo designed the pendulum clock in 1640 according to the isochronous principle of the pendulum. Although its structure is simple, the pendulum clock developed from it.
The first person in history to make a practical pendulum clock was Christiaan Huygens of the Netherlands. The first pendulum clock he made in 1656 was more accurate than any clock at that time. Two years later, in 1658, British scientist hook made a pocket watch with a balance wheel. The pocket watch made by British deniso lecon in 1670 has two needles (hour hand and minute hand), and the surface diameter is about 6cm, which is easy to carry.
The original clock had only one hour hand. The minute hand was added around 1550 A.D., and the second hand appeared only in 1760. The appearance of three pointers indicates that the clock manufacturing 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 of which are the riverrier clock and the Schott clock. Ordinary pendulum clocks are placed in the air. Due to the changes of air temperature, air pressure, humidity, etc., the swing cycle of the pendulum will be affected, making the clock walk less evenly and accurately. The riverrier clock is placed in a glass tank. Most of the air in the tank has been evacuated (vacuum), reducing the impact of pressure changes. Then put the clock in a deep basement, where the temperature changes no more than 1 degree in a year, which can make the clock run very evenly. The change of riverriel clock in a day and night is about 1/100 second.
The more accurate astronomical clock is the clock (called Shaote clock) invented by Shaote in 1920. It is characterized by two pendulums, one is a free pendulum, which controls the pendulum of the sub clock and forces it to swing with its own beat. The pendulum of the sub clock is connected with the clock machinery to indicate the time. The error of the Shaote clock walking day and night is about 1/1000 second, which is considered to be the best kind of mechanical clocks.
The accuracy of the Shaote clock is very high. People have used it to discover the non-uniformity of the earth's rotation. But it is not the highest, and it is also afraid of vibration. A small earthquake will make the pendulum stop or walk inaccurately.
Astronomical clocks are stored in the basement with constant temperature and pressure, and people don't go there easily (because people's body temperature and breathing will change the temperature in the basement). Then, how do you know the time? Originally, astronomical clocks have another clock face, which is connected with the master clock working in the basement by wires. The time of the clock on the ground (called work clock or sub clock) is the same as that of the master clock. As long as people look at the work clock on the ground, they can know the time, which is really "one heart from top to bottom".