The principle of entropy increase refers to isolationThermodynamic systemOfentropyNot decreasing, always increasing or unchanged.Used to give aIsolated systemThe evolution direction of.
The law of entropy increase is the most scientific law, which is Einstein's view.Energy, like materials and information, is one of the three basic elements of the material world. Among the laws of physics, the law of conservation of energy is the most important law, which shows that various forms of energy are always in balance when they are transformed into each other.The concept of entropy originated from physics and was used to measure the degree of disorder of a thermodynamic system.The second law of thermodynamics, also known as the "law of entropy increase", indicates that in natural processes, the total degree of chaos (i.e., "entropy") of an isolated system will not decrease.
yesAdiabatic process, Q=0, there is Δ S (adiabatic) ≥ 0 (irreversible when greater than, reversible when equal to) or dS (adiabatic) ≥ 0 (irreversible when greater than 0;=0 reversible)
The principle of entropy increase shows that under adiabatic conditions, only processes with dS ≥ 0 can occur, where dS=0 represents a reversible process;DS ＞ 0 indicates irreversible process, and dS ＜ 0 process is impossible to occur.butReversible processAfter all, it is an ideal process.Therefore, under adiabatic conditions, all possible actual processes will increase the entropy of the system untilEquilibrium state。
BoltzmannIt has been claimed that the entropy before collision is less than that after collision, so the entropy is increasing.But his proof is wrong, because if so, the same demonstration process can be applied in the opposite direction of time, then it should also be entropy increase, and entropy increase in the opposite direction of time, which means entropy decrease in the positive direction[1]。
What's right? Basically, entropy tends to run towards the maximum value in terms of positive time or negative time.In other words, it can only be said that in the long run, entropy is more likely to be at the maximum entropy.And entropy increase or entropy decrease is not a physical principle that can be deduced from physics.
The question is: why is the universe in a process of entropy increase.The explanation of the physical world is that the initial condition of the world is the point before the big bang with minimal entropy, which determines that the world willexperienceA very long process of entropy increase.(Refer to the Road to the Reality by Rogers Penrose.)[2]）
Important position
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The principle of entropy increase is a physical principle with the same status as the conservation of energy.
The principle of entropy increase is suitable for thermodynamic isolated systems, and the law of conservation of energy is a universally applicable law describing nature.Law of entropy increaseIt is only suitable for isolated systems, which is the key to the problem.In fact, absolute connection and relatively isolated synthesis are the essence of the movement of things.Although in terms of processing methods, it is possible to assume that there are isolated processes in nature.But in essence, it is subjective to isolate something from the nature.When the system is no longer artificially isolated, it is no longer only entropy increase, but both entropy increase and entropy decrease.So we can see that the law of conservation of energy is still valid.
Theorem description and generalization
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The principle of entropy increase is expressed as: the entropy of an isolated thermodynamic system does not decrease.For the reversible process of the system, the entropy does not change, but for the irreversible process, the entropy increases.AndThe second law of thermodynamicsIt is equivalent to and can be expressed as the maximum entropy of an isolated system after reaching the equilibrium state.There are many equivalent descriptions, and the commonly used ones are: the equilibrium internal energy of the adiabatic system is the lowest;The equilibrium enthalpy of isobaric system is the lowest;IsothermalHelmholtz free energyMinimum;Isothermal isobaric systemGibbs free energyMinimum.
Three basic laws
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We know that there are three basic laws in science, namely, the law of conservation of mass, the law of conservation of energy and the law of conservation of charge.The law of conservation of mass and energy has been extended to the law of correlation of mass and energy in the micro field.The law of conservation of mass, the law of conservation of energy and the law of correlation between mass and energy are mathematically expressed as equations.The law of entropy increase is an inequality, that is, in an isolated system, entropy increase is always greater than or equal to zero (△ S ≥ 0).The difference between equality and inequality implies profound significance.
From the basic point of the system's three images, the problem is as follows: the materiality, energy and information of any system state (point) cannot be separated from each other, but matter (mass) and energy are conserved, while information (information is negative entropy) is not.
Entropy always increases in an isolated thermodynamic system.But this conclusion is an empirical rule obtained without considering the gravitational force inside the thermodynamic system.At the interstellar scale, due to the action of gravity, the system tends to be in the order of convergence rather than the uniform disorder.Structures formed due to gravity at the interstellar scale:fixed starIt can output negative entropy flow outward.This can explain why there is such an ordered structure of living things on the earth.The life on the earth is an open system, which maintains itself in a low entropy ordered state by absorbing low entropy substances (ordered polymers) from the environment and releasing high entropy substances (disordered small molecules) to the environment.The negative entropy flow of the whole earth comes from the light flow (negative entropy flow) of plants absorbing the sun to produce low entropy matter.
For thermodynamic systems that do not consider gravity, because entropy always increases, the process appears a single vector of time, which is irreversibleNewtonian mechanicsThe reversible time of Newton, Einstein andPrigokinThe split of Haken.The general explanation of modern science is that the process of entropy increase represents the statistical property of the system, that is, the long-term behavior of huge units.The configuration with the largest entropy on this scale is the most likely state.
The law of conservation of mass and the law of conservation of energy are universal laws in nature, while the law of entropy increase is suitable for thermodynamic isolated systems.Any particle or any particle system is suitable for the law of conservation of mass and the law of conservation of energy, but a particle does not talk about entropy increase, and the entropy of non isolated systems does not necessarily increase.
(1) Overview
① It is impossible for heat to transfer from low-temperature objects to high-temperature objects spontaneously and without cost (it is impossible to transfer heat from low-temperature objects to high-temperature objects without causing other changes, which is expressed in the direction of heat conduction).
② It is impossible to take heat from a single heat source and turn it all into work without any other impact (this is from the perspective of energy consumption, which means that the second type of perpetual motion machine is impossible to achieve).It comes from the second law of thermodynamics, the most basic law in physics.This most heartbreaking and despairing law in the history of science seems to have already stipulated the fate of the universe.
(2) Description
①The second law of thermodynamicsIt is one of the basic laws of thermodynamics.It is about all physical and chemical processes related to thermal movement in limited space and timeIrreversibilityExperience summary.
The statement ① in (1) above was put forward by Clausius in 1850. ②Kelvin put forward the theory of.These statements are equivalent.
In ①, it is pointed out that under natural conditions, heat can only be transferred from high temperature objects to low temperature objects, and cannot be automatically transferred from low temperature objects to high temperature objects, that is, under natural conditions, this transformation process is irreversible.To reverse the direction of heat transfer, it is only achieved by consuming work.
In the statement of ②, it is pointed out that any form of energy in nature can easily become heat, and in turn, heat cannot completely become other forms of energy without producing other effects, which shows that this transformation is irreversible under natural conditions.Heat engine can continuously change heat into mechanical work, which must be accompanied by heat loss.The second law is different from the first law. The first law denies the possibility of creating and eliminating energy. The second law clarifies the direction of the process and denies the possibility of using energy in a special way.
② It was once envisaged to build a machine that can take heat from a single heat source and make it completely useful without any other impact. This kind of imaginary heat engine is called the second type of perpetual motion machine.It does not violate the first law of thermodynamics, but it violates the second law of thermodynamics.Someone once calculated that there is 1 billion cubic kilometers of sea water on the surface of the earth. With sea water as a single heat source, if the temperature of sea water is only lowered by 0.25 degrees, and the heat is released, it will be able to turn into 10 billion degrees of electricity, enough for the world to use for a thousand years.However, a heat engine using only the ocean as a single heat source violates the second statement above, so it is absolutely impossible to produce a heat engine with 100% thermal efficiency.
③ From the point of view of molecular motion theory, work is the regular motion of a large number of molecules, while thermal motion is the irregular motion of a large number of molecules.Obviously, the probability of irregular motion changing into regular motion is very small, while the probability of regular motion changing into irregular motion is large.An isolated system that is not affected by the outside world, its internal spontaneous process is always going from a state with low probability to a state with high probability, from which it can be seen that heat cannot become successful spontaneously.
④ The second law of thermodynamics can only be applied to a system composed of a large number of molecules and a limited range of macro processes.It does not apply to a small number of microscopic systems, nor can it be extended to the infinite universe.
(3) Detailed
In short, the second law says that heat flows from hot places to cold places, and scientists would rather not find it.For any physical system, this is an obvious characteristic without mystery: boiling water cools, and ice cream turns into sugared water.To reverse these processes, extra energy must be consumed.In the broadest sense, the second law holds that the "entropy" (degree of disorder) of the universe is increasing day by day.For example, the spring of a mechanical watch is always looser and looser;You can tighten it, but it will consume a little energy;This energy comes from a piece of bread you eat;Bread making wheat needs to absorb the energy of sunlight during its growth;In order to provide this energy, the sun needs to consume its hydrogen for nuclear reaction.In short, the decrease of entropy in each part of the universe must be at the expense of the increase of entropy in other places.
In a closed system, the entropy always increases to the extent that it can not be greater.At this time, the system interior reaches a completely uniform state of thermal dynamic balance, and no change will occur unless the outside world provides new energy to the system.For the universe, there is no "outside", so once the universe reaches the thermodynamic equilibrium, it will die completely.This scenario is called "heat silence".
Realistic examples
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Refrigerator cannot reduce entropy
Clausius expressed the principle of entropy increase as: "heat cannot be automatically transferred from low temperature objects to high temperature objects", which gives people an illusion that the work done by the outside world to transfer heat from low temperature objects to high temperature objects, or to change an isothermal body into a non isothermal body, means entropy reduction.This kind of understanding is one-sided. Take the refrigerator with a job in an insulated room as an example. The temperature inside the refrigerator becomes lower and the temperature outside the refrigerator becomes higher. Many people call this phenomenon of temperature difference caused by external work entropy reduction.This view is wrong. Only for the inside and outside of an indoor refrigerator, if the thermal effect of current is taken into account, the total entropy change in this room will only increase (if you don't believe it, you can calculate it).The entropy in the insulation system cannot be reduced by the work done by the outside world, and the entropy in the insulation system cannot be reduced by the work done by non thermal energy such as electrical energy and mechanical energy (thermal effect cannot be avoided in general). Therefore, we believe that the accurate expression of the entropy increase principle should be: "On the equipotential surface, the entropy in the adiabatic system will never decrease".
Geothermal source
Underground thermal energy reserves are huge, equivalent to 170 million times of global coal reserves.It is estimated that, based on the total energy consumption of the world today, even if all geothermal energy is used, it will take 41 million years to reduce the temperature of the earth's interior by 1 ℃.Geotherm is characterized by high distribution inside and low distribution outside. We believe (another paper) that it follows the "statics equation of compressible fluid", that is, the balance law of potential enthalpy (potential energy+enthalpy). When the local internal potential enthalpy is lower than the surface potential enthalpy, gravity has the mechanism of gathering surface low-temperature heat energy to transfer to the earth center, and geothermal is an eternal energy.There are two main explanations for the problem of geothermal source, for which there is no accurate conclusion:
1. The radioactive elements inside the earth transmute and release heat, that is, atomic energy;
2. The heat brought by the earth in its early formation.Our view on the above explanation is that if it is the first one, there are three situations:
① Geothermal temperature is low outside and high inside. It is distributed according to a certain gradient. The heat source must be in the center of the earth. Isn't that the atomic bomb?The consequences are unimaginable;
② Mineral distribution usually follows the principle of "birds of a feather flock together", so the distribution of radioactive elements (heat source) in the earth's interior will be consistent with the distribution of geothermal energy, which is obviously unreasonable;
③ Underground hot springs or magma (rocks) should contain very strong radioactive materials, but in fact there is no radioactive material. Therefore, the main source of geothermal energy cannot be the transformation of radioactive elements.If it is the second type, the first is volume shrinkage extrusion;Second, there is the possibility that the originally high-temperature body will form a heat gradient distribution after cooling.We think there is also a third possibility, that is, the temperature of the earth is uniform but not very high. Since 4.5 billion years ago, gravity has transferred the heat energy from the low temperature area of the surface to the center of the earth, making the heat form a gradient distribution (about 5000 ℃ in the center), and gradually realizing the potential enthalpy balance.
