The most despairing physical law "the principle of increasing entropy": life feeds on negative entropy and eventually dies. In the 13th century, a man named Hennekau raised such a question: The center of the wheel There is a rotating shaft, and 12 movable short rods are installed on the edge of the wheel, and an iron ball is installed at one end of each short rod.

The ball on the right is farther from the axis than the ball on the left. Therefore, the ball on the right produces a greater rotational torque than the ball on the left. In this way, the wheel will rotate endlessly in the direction pointed by the arrow, and drive the machine to rotate. This wheel is called the "Henneco Magic Wheel". It makes scientists dream of a "perpetual motion machine". Scientists fantasize about it.

Once the perpetual motion machine is born, human beings will produce a steady stream of energy. Therefore, many scientists have been trying to reproduce the "Henneker's Magic Wheel", but they have failed miserably. However, countless failures have not given up. The enthusiasm of scientists has only increased their enthusiasm for the exploration of perpetual motion machines. Later, Leonardo da Vinci in Renaissance Italy built a similar device.

When designing, he believed that the heavy ball on the right was farther from the center of the wheel than the heavy ball on the left. Under the influence of the imbalance on both sides, the wheel would continue to rotate in the direction of the arrow, but the experimental result was Negative. Leonardo da Vinci keenly concluded from this: perpetual motion is impossible to achieve. In fact, from the principle of lever balance, it can be seen that in the above two designs.

Although each weight on the right exerts a greater rotational effect on the wheel, the number of weights is smaller. Accurate calculations can prove that there will always be a proper position where the rotational effects (moments) exerted by the weights on the left and right sides on the wheel in opposite directions are exactly equal and cancel each other out, so that the wheel reaches balance and stops.

Despite this, scientists have never given up on this dream. People have also proposed various designs of perpetual motion machines that use the inertia of wheels, capillary action of thin tubes, electromagnetic force, etc. to obtain effective power, but none of them have. Exceptions failed. In 1847, the German scientist Helmholtz published his book "On the Conservation of Force."

He proposed that all natural phenomena should be explained by the motion of particles interacting with central forces. At this time, the first law of thermodynamics, which is the law of conservation of energy, already had a vague prototype. In 1850, Clausius published a paper "On the Power of Heat and the Laws of Heat Itself That Can Be Deduced From It."

He believes that the single principle is that "in all cases where work is produced by heat, an amount of heat proportional to the work produced is consumed, and conversely, by consuming the same amount of work, such an amount can be produced. Heat." plus the principle that "any amount of heat can be moved from a cold body to a hot body without any expenditure of force or other changes, which contradicts the behavior of heat." Think of heat as a state quantity.

From this, Clausius finally derived the analytical formula of the first law of thermodynamics: dQ=dU-dW. Since 1854, Clausius has done a lot of work and tried hard to find a method for people An easy way to prove this principle. After many efforts, in 1860, the principle of conservation of energy, also known as the first law of thermodynamics, began to be generally recognized.

The principle of conservation of energy is expressed as the change in the total energy of a system can only be equal to the amount of energy transferred into or out of the system. The total energy is the sum of the mechanical energy, thermal energy and any form of internal energy other than thermal energy of the system. The first law of thermodynamics declares the bankruptcy of a perpetual motion machine because it violates the conservation laws of energy and mass in any perpetual motion machine design.

We can always find an equilibrium position. In this position, the various forces cancel each other out and there is no longer any driving force to make it move. All perpetual motion machines will inevitably come to rest at this equilibrium position and become immobile. The first law of thermodynamics also contributed to the birth of the steam engine, which directly led to the birth of the first industrial revolution.

Humanity has thus entered the steam age, and the era of mechanized production has begun. The proposal of the law of conservation of energy still did not dissuade scientists from their dreams. They dreamed of creating another kind of perpetual motion machine, hoping that it would not violate the first law of thermodynamics and be both economical and convenient.

For example, this kind of heat engine can directly absorb heat from the ocean or atmosphere and turn it completely into mechanical work.

Since the energy of the ocean and atmosphere is inexhaustible, this heat engine can run continuously to perform work and is also a perpetual motion machine. To put it simply, people realize that energy cannot be created out of thin air, so they try to absorb thermal energy from the ocean, atmosphere and even the universe, and use this thermal energy as the source to drive the rotation and work output of perpetual motion machines.

A heat engine that absorbs heat from a single heat source and turns it completely into useful work without producing other effects is also called the second type of perpetual motion machine. Scientists believe that as long as there is only a single heat source, and all the heat it absorbs from this single heat source can be used to do work without causing other changes, the second type of perpetual motion machine can be successful.

At this time, with the development of science, some limitations of Newtonian classical mechanics have also been exposed. For example, Newtonian classical mechanics believes that the mechanical process is reversible, and reversibility refers to time reversal, that is, the process Proceed in reverse order. In the equations of motion of classical mechanics, replacing the time parameter t with -t means that the process goes through all the original states in reverse order and finally returns to the initial state.

In 1850, Clausius proposed a basic law in his paper: "It is impossible to transfer heat from low temperature to high temperature without the consumption of some kind of power or other changes." This law is called Second law of thermodynamics. The second law of thermodynamics contradicts the reversibility of mechanical processes.

So Clausius proposed a new physical quantity to explain this phenomenon in his 1854 essay "A Modified Form of the Second Fundamental Theorem of the Mechanical Theory of Heat", which was officially named in 1865. Entropy, represented by the symbol S. Clausius started from the efficiency of heat engines and realized that positive transformation (conversion of work into heat) can occur spontaneously.

The negative transformation (successful heat transformation), as the reverse process of the positive transformation, cannot proceed spontaneously. The occurrence of a negative transformation needs to be accompanied by a positive transformation at the same time, and the energy of the positive transformation is greater than the negative transformation. This actually means that the positive transformation in nature cannot be restored. From this Clausius proposed another expression of the second law of thermodynamics, also known as the principle of entropy increase.

That is: the slight increase in entropy in an irreversible thermodynamic process is always greater than zero. In natural processes, the total disorder (i.e., "entropy") of an isolated system does not decrease. In short, the entropy of an isolated system never decreases automatically. The entropy remains unchanged during the reversible process and increases during the irreversible process. It can be said that it clearly points out the direction of the irreversible process.

The principle of entropy increase is another expression of the second law of thermodynamics, but it has a deeper meaning. It created the concept of "entropy". This concept was later widely used. Shannon extended the concept of entropy to the process of channel communication, thus creating the discipline of "information theory" and announcing the arrival of the information age.

The principle of entropy increase shows that under adiabatic conditions, only the process of dS≥0 can occur, where dS = 0 represents a reversible process; dSgt; 0 represents an irreversible process, and dSlt; 0 process is impossible to occur. . But the reversible process is an ideal process after all. Therefore, under adiabatic conditions, all possible actual processes will increase the entropy of the system until an equilibrium state is reached.

The adiabatic process is the change process of an adiabatic system, that is, there is no heat exchange between the system and the environment. In the adiabatic process, Q = 0, there is ΔS (adiabatic) ≥ 0 (irreversible when greater than time, reversible when equal to time) or dS (adiabatic) ≥ 0 (gt; 0 irreversible; = 0 reversible). The greatest significance of the entropy increase principle is that from The perspective of energy quality stipulates the direction, conditions and limit issues in the energy conversion process.

The emergence of the principle of entropy increase means that the reversibility of classical mechanics does not apply to all situations. It is only accurate when guaranteed by universal mechanical principles. Thermal motion is an irreversible process. At the same time, it also completely announced the demise of eternal power. Because absorbing heat from seawater to do work means absorbing heat from a single heat source and turning it completely into useful work without producing other effects, which is impossible to achieve.

And Schr?dinger pointed out that the process of entropy increase must also be reflected in the living system. In other words, the entropy in the living system should also be constantly increasing, and it can only develop from order to disorder. But from a certain perspective, the meaning of life lies in the ability to resist the increase in entropy, that is, the ability to decrease entropy. The most typical manifestation is the behavior of eating.

We have absorbed "negative entropy" from food to maintain the order of life, that is, "the essence of metabolism is to eliminate all negative entropy produced by organisms all the time in a timely manner." Order and disorder here describe macroscopic states. Therefore, the body successfully absorbs negentropy from the surrounding environment during the metabolic process.

Release all the positive entropy that its life activities have to produce to the surrounding environment to maintain survival and evolution. In short, life is an open, irreversible, non-thermodynamic equilibrium system. The equilibrium state is disordered, while the non-equilibrium state is the source of order. This is consistent with the second law of thermodynamics and the principle of entropy increase. Schr?dinger vividly summed it up with the famous saying "Life depends on negative entropy".

Despite this, the entropy reduction behavior of life has no effect. After all, in the vast universe, life such as humans is simply so small that it can be ignored. The inevitability and irreversibility of entropy increase dictate that life can only develop from order to disorder, and eventually to aging and death. Therefore, the principle of entropy increase is also called by many people: the most desperate physical law.

The principle of entropy increase applies to many fields, including whether it is inconsistent with Darwin's theory of evolution. The biggest debate among scientists about the principle of entropy increase is whether the universe is a closed system, because the conditions for entropy increase to work must be in an isolated system, and then the equilibrium entropy is maximized. Isolated systems are in thermodynamics.

A system that does not exchange matter or energy with other objects is called an isolated system. No energy or mass can enter or leave an isolated system, it can only move within the system. The earth is an open system. The principle of entropy increase can be applied to life, and naturally it can also be applied to the earth.

So organisms on earth maintain themselves in a low-entropy ordered state by taking in low-entropy substances (ordered macromolecules) from the environment and releasing high-entropy substances (disordered small molecules) into the environment. The overall negative entropy flow of the earth comes from plants absorbing the sun's light flow (negative entropy flow) to produce low-entropy matter. This led to the emergence of such an orderly structure of living things on the earth.

It will not keep entropy in a state of increasing, so scientists think about whether the universe is an isolated system, because there is no "outside world" in the universe, and we are constantly consuming energy, and it is irreversible. Entropy continues to increase towards its maximum value, so once the universe reaches thermal equilibrium, it is completely dead.

This scenario is called "heat death". In such a universe, there is no longer any energy to maintain motion or life. This has attracted opposition from some scientists, who claim that the principle of entropy increase can only be applied to systems composed of a large number of molecules and macroscopic processes within a limited range. It is not applicable to a small number of microscopic systems, nor can it be extended to the infinite universe.

Because it involves major issues such as the future of the universe and the fate of mankind, its scope of influence and influence has far exceeded the scientific and philosophical circles, and it has become one of the most vexing mysteries in modern history. . But no matter what, the principle of entropy increase, as one of the four laws of thermodynamics, guides the research of thermodynamics and plays an important role in physics.