Does the legendary "perpetual motion machine" really exist?

Nebula Science

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I saw this little toy a few days ago and I was obsessed with it.

▲Source: Teacher Li Yongle's official website, BV1hT4y1u75e

This little toy is called a drinking bird. It is said to be a toy in ancient China. It last appeared in a foreign popular science book in the 1930s, and then disappeared. According to the "Fun Physics Continued" compiled by the famous Soviet popular science writer Beleliman, someone once gave this little toy to Einstein, and even Einstein was amazed. From then on, it had a domineering title - "The Toy That Shocked Einstein". The physics teacher once said: "It is impossible to invent a perpetual motion machine!", so what is this "perpetual motion" drinking bird?

Out of curiosity, I went to Taobao to search for other perpetual motion toys.

▲Such "perpetual motion" can last for about 30 seconds

▲After looking at the buyer's show, I found that I had to install batteries...

▲Balance pendulum, can continue to rotate for a long time

▲Magnetic gyroscope, which is said to be able to keep spinning as long as it is not demagnetized

There are even such

▲Just kidding

We simply classify several typical perpetual motion machine models into categories: magic wheel type, self-circulating kettle, magnetic type, and our drinking bird.

Magic Wheel

As early as around 1159 AD, an Indian mathematical master named Bhaskara designed a wheel with curved grooves filled with mercury. When the wheel rotates, the mercury will flow to the bottom of each groove, so that one end of the wheel is always heavier than the other end, and this imbalance will make the wheel keep turning. This is one of the earliest ideas for perpetual motion machines.

▲Schematic diagram of the perpetual motion machine designed by Bhaskara

In the 13th century, the Frenchman Henckel designed a "magic wheel" that achieved perpetual motion through a series of cantilevers installed on the wheel. Later, some people replaced the mercury with steel balls, the cantilevers with pendulums, and the fan blades, which are actually variations of this unbalanced structure.

▲The magic wheel perpetual motion machine copied from Henkel's design

In the 15th century, our versatile Leonardo da Vinci also designed a magic wheel perpetual motion machine. He left a large number of ingenious mechanical design drawings in his manuscripts, but they all failed. Leonardo da Vinci finally gave up the idea of ​​perpetual motion machine and called it "an empty fantasy."

▲Leonardo da Vinci's design manuscript for the magic wheel perpetual motion machine

Self-circulating kettle

In the 17th century, Boyle, the boy who proposed "Boyle's Law", proposed the idea of ​​a "self-circulating kettle". He designed a kettle with a thin long tube connected to the top of the kettle. Due to capillary action, the liquid will be attracted by the thin tube, overcome gravity and climb up the tube wall, and finally flow back into the kettle, forming perpetual motion. However, due to capillary action, the liquid in the thin tube could not flow out of the tube in the end. The perpetual motion model of the self-circulating kettle also failed.

▲Sketch of a self-circulating kettle

▲The water eventually stops flowing out

Magnetic perpetual motion machine

In the 18th century, the study of magnetism became popular. Magnets have the "mysterious power" to attract or push objects through the air, which gave new inspiration to scientists at the time, so a perpetual motion machine model using magnets was designed. The magnet version of the "magic wheel" came out. This device, which used magnets to attract small iron balls, and the small iron balls rolled down and were then attracted by the magnets, looked pretty good. However, magnets gradually demagnetized and lost their magnetic force, and the magnetic perpetual motion machine also failed.

▲Design drawing of the magnetic version of the "magic wheel"

▲Schematic diagram of magnetic perpetual motion machine

The designs of these perpetual motion machines are very ingenious, but they violate the first law of thermodynamics and are called first-class perpetual motion machines. The law of conservation of energy, which is well known today, was not proposed until 1842 by Dutch scientist Mayer.

In 1843, British scientist Joule summarized and proposed the first law of thermodynamics: the increase in the internal energy of an object is equal to the sum of the heat absorbed by the object and the work done on the object, that is, heat can be transferred from one object to another, and can also be converted into mechanical energy or other energy, but in the process of conversion, the total value of energy remains unchanged. Its generalization and essence is the law of conservation of energy.

The first perpetual motion machine

During the movement, there will be resistance and heat generated. Even if the loss is small, the device will eventually stop.

The second kind of perpetual motion machine

The advent of the first law of thermodynamics made it clear that the invention of the first type of perpetual motion machine was impossible, so some people proposed the idea of ​​the second type of perpetual motion machine: Can we absorb heat energy from the outside world and use this heat energy as the source of driving the perpetual motion machine to rotate and output work?

In 1881, Grumgy designed the "Zeromotor" for the U.S. Navy. It was envisioned that liquid ammonia would absorb heat from seawater, vaporize to generate steam, and push the piston to gain kinetic energy. The ammonia would then be cooled by seawater and condensed into liquid ammonia, and the cycle would repeat over and over again.

▲Schematic diagram of Gumji's "zero-consumption engine"

However, as early as the 1850s, Clausius of Germany and Kelvin of Britain gave two statements of the second law of thermodynamics. Clausius stated that "heat cannot be transferred spontaneously from a low-temperature object to a high-temperature object." Ammonia cannot return heat to seawater and then become liquid nitrogen. Changing from vapor to liquid requires a cold source and consumes more energy. We call perpetual motion machines that violate the second law of thermodynamics second-class perpetual motion machines.

Drinking Bird

——It’s not a perpetual motion machine

What about the drinking bird mentioned at the beginning? As long as there is water in the cup, the bird will keep drinking water.

The drinking bird can keep drinking water because it cleverly uses the ambient temperature, water temperature and liquid evaporation. The specific principle has been explained in the video of Teacher Li Yongle. If you are interested, you can go and watch it yourself. While other perpetual motion machines need to absorb energy to maintain operation, the drinking bird releases heat, so the drinking bird is not a "perpetual motion machine" but a "heat machine". The ancients were really smart.

▲Source: Teacher Li Yongle's official website, BV1hT4y1u75e

Life never stops, exploration never ends

Why have scientists been so keen on inventing perpetual motion machines for thousands of years? Why are there so many people who are still keen on inventing and researching perpetual motion machines even though the concept of "perpetual motion machines are impossible to realize" is deeply rooted in people's minds?

Imagine if there is a system in the world that can be maintained forever without taking any energy from the outside world, or if we lower the requirements and there is an energy-saving device that can continue to operate for a long time with only a small amount of starting energy, can this system also include humans, and can this device be humans themselves? If so, can life continue forever, and can the immortality that people have dreamed of since ancient times be realized?

We cannot answer these questions at present. Perhaps one day, when humans stand high enough and see far enough, we will discover some magical substances that will allow us to modify or even overturn the existing laws. What scientists once said was impossible will become possible in the future. People's exploration of the universe and research on science are essentially breakthroughs in the boundaries of human beings' own world and perception. The development of science is accompanied by these breakthroughs.

Life goes on, exploration never stops, this is Nebula Science, we look forward to exploring the mysteries of the world with you.

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The pictures in the article are mainly from the Internet and video materials.