# The mystery of the Huygens pendulum clock

Da Vinci spent several years painting an egg story, and I believe everyone is familiar with it. In fact, in the field of science, there are quite a few scientists who are “real” with a small thing. For example, at Harvard University in the United States, there are professors who will teach a semester for a banana, and some people spend a few years studying an egg. The birth process is really eye-opening. Now, there is a small problem that has puzzled scientists for hundreds of years. This problem is the pendulum clock problem.
The invention of the pendulum clock In
1582, in the cathedral of Pisa, Italy, the pastor was preaching to people. Among these people was a poor university student. He was not very interested in preaching, but was attracted by a chandelier on the ceiling of the church. This chandelier has existed in this church for many years and will swing back and forth when the wind blows. This is an ordinary thing, but the student is very keen. He is thinking about a problem: Although the swing distance of the chandelier is getting smaller and smaller, the time required for a round trip seems to be the same. The pulse beating is a regular vibration, will the swing of the chandelier follow this principle?
In order to verify this idea, he held the pulse of his left wrist with his right hand, and silently counted the number of swings of the chandelier, and found that there was indeed a certain connection between them. Before the pastor finished his preaching, he hurried home and hung an object with a rope to study its swinging laws. As a result, he found that the swing cycle of the hanging object was changed as soon as the length of the rope was changed. However, the weight of the hanging object and the swing angle have nothing to do with the swing period. This is the famous principle of “pendulum isochronism”, and the discoverer is less than 20 years old, he is Galileo.
In the past, people always used the uniform flow of flowing materials to time the clock, such as hourglasses and water leaks. At that time, many people, including Galileo, realized that if the pendulum could make a uniform periodic movement, it might improve the accuracy of the timing device. However, in fact, Galileo’s principle of “pendulum isochronism” is problematic. For example, the swing angle of the pendulum actually affects the period of the pendulum, rather than having no effect as Galileo said. If the pendulum is designed according to Galileo’s principle Clock, it is impossible to be on time. Therefore, the real invention of the first pendulum clock had to wait until the 17th century. The inventor was the Dutch scientist Huygens.
Huygens is one of the most famous physicists in history. He established the law of centripetal force and proposed the principle of conservation of momentum. He was also one of the founders of probability theory. At that time, he noticed this problem. He found that the isochronism of Galileo’s pendulum is only valid when the swing angle is relatively small. However, when the swing angle is relatively large, such as when the swing angle is 60 degrees, it is not strict. Timeliness is obvious. Huygens carefully studied and solved these problems, and then studied its application in machinery, and designed a strictly isochronous pendulum clock structure.
In 1657, at the age of 28, Huygens introduced a gravity pendulum into a mechanical clock and invented the pendulum clock. The accuracy of the pendulum clock is 100 times that of previous European timepieces, and the error of an average of 15 minutes per day has been improved to approximately one minute per week. Huygens solved Galileo’s confusion, but there was one problem he could not solve, and left a 350-year unsolved historical mystery for modern science-the mystery of the Huygens pendulum clock.
The mystery of the Huygens pendulum clock In
1665, Huygens was ill in bed, looking at the two clocks hanging on the wall, he also noticed a strange phenomenon: no matter where or when the two pendulums started Swing, in about half an hour, they will eventually swing opposite each other at the same frequency. Later, Huygens personally released two pendulums at different times, and the result was the same.
Why can pendulums hung on the same wall affect each other and gradually become synchronized over time? At that time, Huygens believed that there must be a mysterious “communication” between the pendulums.
For centuries, due to the lack of precise tools for measuring the interaction between pendulums, no one knew the mystery. In 2002, the researcher Kurt Vaijfeld in Atlanta, USA, conducted an experiment on this problem. He found that the isochronism similar to Huygens pendulum clock, but this situation is only in the pendulum weight ratio This happens when the entire pendulum clock structure is much lighter. If the ratio of the mass of each pendulum to the mass of the entire clock is less than 1:120, the pendulums of the two clocks will start to swing in opposite directions. If this ratio is greater than 1:80, one or both of the pendulums will gradually stop swinging.
Although Vajfrid’s experiment replicated the strange phenomenon that Huygens saw at the time, some scientists did not buy it. They believed that the experiment did not explain why the weight of the pendulum affects the direction of the pendulum’s vibration, and more importantly. One point is that, judging from the manuscript left by Huygens, the pendulum clock designed by Huygens at that time did not follow this principle of specific gravity, and the experiment of Vajfrid did not explain why Huygens’ pendulum Sync within half an hour.
The secret hidden in the sound
In 2015, researchers at the University of Lisbon in Portugal decided to take a different approach. The pendulum clock used by the previous researchers was a reduced version of commercial and general-purpose watches. The materials used to support the pendulum clock were also very different from those used by Huygens. Similarly, they decided to restore Huygens’ observation conditions at that time.
The researchers commissioned a large memorial clock factory in Mexico to create two complex pendulum clocks, imitating the pendulum clocks used by Huygens at the time, and then hung them on aluminum beams and used high-precision optical sensors to measure the swing of the pendulum. cycle. Sure enough, after a period of time, the pendulum began to swing in the opposite direction with the same amplitude.
Subsequently, the researcher put the two clocks on a wooden table. As they expected, the movement of the pendulum is synchronized with time. However, a very strange phenomenon appeared. Unlike what Huygens observed, the clock did not swing in the opposite direction. On the contrary, they swing in exactly the same direction. Although the pendulums of the two clocks are kept in sync, they become slower and slower over time, and the time displayed on the two clocks is also very inaccurate. So why is this?
Through the digital model of the analog clock, the researchers found the answer.
It turns out that Huygens’ prediction more than 300 years ago was correct. The two clocks did have a “communication” phenomenon, and the “communication tool” turned out to be a support for connecting the clocks, such as a wooden table. The two clocks exchange energy through the wooden table. . The stiffness, thickness, and quality of the support material will affect the way the clock is synchronized and the accuracy of the clock.
So, what energy is transferred between these suspension materials?
The researchers used different suspension materials and tried many times, and finally found that only when the materials have very good sound conductivity, the time of the two clocks will get closer and closer, and the frequency of the pendulum swing will get closer and closer. Resonance will appear. This research also found a possible explanation for the mystery of Huygens pendulum clocks: the sound energy of the moving clocks shuttles between the materials connecting them, causing them to finally appear resonance with the same swing amplitude.
Although the pendulums designed by Huygens have various forms, they all follow a basic structure. Pendulums, gears and other devices rely on each other to generate thrust motion. The mechanical motion of each structure will generate a small amount of sound energy. When a bell ticking and swinging, these sound energy will spread between the two conductors and exchange energy , The swings of the two pendulums will be adjusted accordingly until they resonate and the pendulum of one clock is synchronized with the other. It turns out that the real driving force behind the scenes is “sound energy.”
So, why does this experiment take as long as 18 hours or even several days for synchronization to occur? Why is clock synchronization so slow?
The researcher also gave a good explanation. Huygens’ clock weighs 23 kilograms or 27 kilograms, and the two pendulum clocks are connected by a rigid wooden beam, while the pendulum clock in the researcher’s experiment is only 0.4 Kilograms or lighter, the clock suspension material is not as strong, more flexible materials tend to absorb most of the energy from the clock and prevent it from being transmitted, so Huygens clock transmission of sound energy is greater.
In life, there are many synchronization phenomena. For example, in the human body, there are several biological rhythms: breathing, heartbeat and arterial beating. Scientists have found that when some of these rhythms are synchronized with each other, energy consumption is minimal, so in this case, synchronization is beneficial to the body.
On the other hand, synchronization can also be dangerous or harmful. For example, the process of epileptic seizures is closely related to the abnormal synchronization of neurons. In architecture, engineers once ignored the phenomenon of resonance, which led to the collapse of the bridge. For example, the Tacoma Strait Suspension Bridge in Washington State, USA, because of its insufficient deck thickness, caused the Carmen Vortex Street when it was hit by strong winds, causing the bridge to swing. When the vibration frequency of the Karman vortex street is the same as the natural frequency of the suspension bridge itself, the suspension bridge will violently resonate and collapse. If the Huygens pendulum problem is clarified, it may help explain the widespread synchronization phenomenon in nature and solve some practical problems.
However, although the supporting material between the pendulums can transmit sound energy and synchronize the two clocks, the researchers are not satisfied with this answer. The researcher did another experiment and replaced the gear drive mechanism of the two clocks with a smoother mechanism. At this time, the clock did not generate such a large energy pulse. However, the pendulum clock still exhibited synchronization, which shows that in addition to the sound Yes, these two clocks must still be affected by other factors. For the researcher, this experiment just uncovered a veil of the mystery of Huygens’ pendulum. Behind this seemingly simple question, there must be other answers that have not been found.