Entropy Shā ng Physical term, the quotient obtained by dividing heat by temperature, indicating the degree to which heat is converted into work [Entropy] Physical meaning: the symbol of the degree of chaos when a substance is in microscopic thermal motion. One of the parameters that characterize the state of matter in thermodynamics is usually represented by the symbol S. In classical thermodynamics, the available increment can be defined as ds = (dq/t), where t is the thermodynamic temperature of matter; DQ is the heat added to matter in the process of entropy increase. The subscript "reversible" means that the change process caused by the heating process is reversible. If the process is irreversible, DS > (DQ/T) is irreversible. The entropy per unit mass of matter is called specific entropy, and it is recorded as S. Entropy is originally a state parameter of matter that reflects the irreversibility of spontaneous process according to the second law of thermodynamics. The second law of thermodynamics is a law summarized from a large number of observation results, which has the following statements: ① Heat is always transferred from a high-temperature object to a low-temperature object, and it is impossible to carry out the opposite transfer without causing other changes; (2) Work can be completely converted into heat, but no heat engine can completely and continuously convert the received heat into work (that is, it is impossible to make a perpetual motion machine of the second kind); ③ In an isolated system, the actual process always increases the entropy of the whole system, which is the principle of entropy increase. Friction irreversibly converts a part of mechanical energy into heat energy, which increases entropy. Heat dQ is transferred from a high-temperature (T 1) object to a low-temperature (T2) object. The entropy of high-temperature objects decreases dS 1=dQ/T 1, and the entropy of low-temperature objects increases dS2=dQ/T2. When these two objects are combined into a system, the change of entropy is DS = DS2-DS 1. ◎ Physically, it refers to the quotient obtained by dividing heat energy by temperature, indicating the degree to which heat is converted into work. ◎ In science and technology, it generally refers to a Liang degree of some material system states and the possible degree of some material system states. Social science also uses it to compare the degree of certain States of human society. In information theory, entropy is a measure of uncertainty. Only when the energy density in the specific system you use is uneven can energy be converted into work. At this point, energy tends to flow from higher density to lower density until everything becomes uniform. It is through this energy flow that you can get work from energy. The water level in Heyuan is relatively high, and the potential energy of the water there is also greater than that in the estuary. For this reason, water flows downstream into the ocean. If it hadn't rained, all the water on the mainland would have flowed into the ocean, and the sea level would have risen slightly. At this time, the total potential energy remains unchanged. But the distribution is relatively uniform. It is when the water flows downwards that the waterwheel can turn and the water can do work. Water on the same horizontal plane can't do work, even on a very high plateau, so the potential energy is extremely high and it can't do work. What is decisive here is the difference of energy density and the flow in the direction of homogenization. Entropy is a measure of chaos and disorder. The greater the entropy, the greater the disorder. Our universe is a universe with increasing entropy. The second law of thermodynamics embodies this characteristic. Life is highly orderly, and wisdom is highly orderly. Why does life appear in the universe with increasing entropy? Will evolve wisdom? (negative entropy). The second law of thermodynamics also reveals that local order is possible, but it must be at the expense of greater disorder elsewhere. People need energy and food to survive, at the cost of the death of animals and plants (entropy increase). Everything grows on the sun. The order of animals and plants is at the expense of the exhaustion of solar nuclear reaction (entropy increase) or other forms of entropy increase. People are locked in a completely closed lead box and cannot maintain their negative entropy with the increase of entropy in other places. In this relatively closed system, the law of entropy increase destroys the order of life. Entropy is the arrow head of time, which is irreversible in this universe. Entropy is closely related to time. If time stops "flowing", there is no way to increase entropy. Any "anything we know can be locked" is just "time". What is closed at low temperature is also "time". Life is an orderly "structure" of matter. "Structure" and concrete matter are not the same concept. Just like the building materials and the building style are not at the same level. Biology has proved that no atom in the elderly is born. However, you are still you, I am still me, and life goes on. On the contrary, a dead person can leave molecules in the body for a long time without metabolism. Consciousness is a higher order than life and can be transmitted between lives. Having said that, I think the hierarchical relationship between matter and consciousness should be clear. (Excerpted from People's Network BBS Forum) Any kind of energy is the same. In a steam engine, there is a hot storage to turn water into steam, and a cold storage to condense steam into water. It is this temperature difference that plays a decisive role. At any single and undifferentiated temperature, no matter how high, it is impossible to get any works. Entropy is a term coined by the German physicist Clausius (1822–1888) in 1850. He used it to express the uniformity of any energy distribution in space. The more uniform the energy distribution, the greater the entropy. If the energy distribution of the system we consider is completely uniform, then the entropy of this system will reach the maximum. According to Clausius, in a system, if it is allowed to develop naturally, the energy difference always tends to be eliminated. Let a hot object come into contact with a cold object, and the heat will flow in the following ways: the hot object will cool, and the cold object will get hot until the two objects reach the same temperature. If two reservoirs are connected, and the water level of one reservoir is higher than the other, gravity will lower the water level of one reservoir and raise the water level of the other reservoir until the water levels of the two reservoirs are equal and the potential energy is uniform. Therefore, Clausius said, a universal law of nature is that the differences in energy density tend to be equal. In other words, "entropy will increase with time". In the past, the research on the flow of energy from a higher density place to a lower density place was mainly carried out in the form of heat energy. Therefore, the science of energy flow and work-energy conversion is called "thermodynamics", which comes from the Greek word "thermal motion". People have long drawn the conclusion that energy can neither be created nor destroyed. This is the most basic law; So people call it "the first law of thermodynamics". Clausius's theory that entropy increases with time seems to be almost a very basic universal law, so it is called "the second law of thermodynamics". Describe one of the important state functions of thermodynamic system. The size of entropy reflects the stability of the system, the change of entropy indicates the direction of thermodynamic process, and entropy provides a quantitative expression for the second law of thermodynamics. In order to quantitatively express the second law of thermodynamics, we should look for a state function that is constant in reversible process and monotonically changes in irreversible process. When studying Carnot heat engine, Clausius obtained a formula suitable for any cycle process according to Carnot theorem, where q is the tiny heat absorbed by the system from a heat source with a temperature of t, and the equal sign and the unequal sign correspond to reversible and irreversible processes respectively. Reversible cycle indicates the existence of a state function entropy, which can be defined as another formula (see related works). For adiabatic process q = 0, so S≥0, that is, the entropy of the system remains unchanged in reversible adiabatic process and monotonously increases in irreversible adiabatic process. This is the principle of entropy increase. Since all changes in an isolated system have nothing to do with the outside world, it is an adiabatic process, so the principle of entropy increase can also be expressed as: the entropy of an isolated system will never decrease. It shows that the entropy of isolated system increases monotonously with the movement from non-equilibrium state to equilibrium state, and reaches the maximum when the system reaches equilibrium state. The change and maximum of entropy determine the direction and limit of isolated system process, and the principle of entropy increase is the second law of thermodynamics. Energy is a measure of material movement, which has many forms and can be converted to each other. The more energy in a certain form, such as internal energy, indicates the greater potential for transformation. The original word of entropy means transformation, which describes the direction and degree of spontaneous transformation between internal energy and other forms of energy. With the transformation, the system tends to be balanced, and the entropy value is getting bigger and bigger, which shows that although the total energy value remains unchanged in this process, the energy available for utilization or transformation is getting less and less. The first and second laws of internal energy, entropy and thermodynamics make people have a comprehensive and complete understanding of the basic characteristics of energy conversion process related to thermal motion. Microscopically, entropy is a measure of the disorder degree of a large number of microscopic particles that make up a system. The more disordered and chaotic the system is, the greater the entropy is. The microscopic essence and statistical significance of irreversibility of thermodynamic process is that the system moves from order to disorder, and from a state with less probability to a state with greater probability. The reason for this phenomenon is also very simple, that is, there are far more ways to lead to disorder in nature than to order. For example, it takes some means to make a group of students stand in a row on the playground, but it is very simple to make them run around on the playground. Entropy in information theory: the unit of measurement of information. Shannon, the founder of information theory, put forward information measure based on probability and statistics model in his book Mathematical Theory of Communication. He defined information as "something used to eliminate uncertainty". Shannon formula: I(A)=-logP(A) I(A) measures the information provided by the occurrence of event A, which is called the self-information of event A, and P(A) is the probability of the occurrence of event A. If a random experiment has n possible results or a random message has n possible values, if their probabilities are p 1, p2, ... The greater the amount of information, the more regular the structure, the more perfect the function and the smaller the entropy. Using the concept of entropy, we can theoretically study the measurement, transmission, transformation and storage of information. In addition, entropy has some applications in cybernetics, probability theory, number theory, astrophysics, life science and other fields. In physics, Boltzmann said, "When energy decreases, atoms are in a more disordered state." Entropy is a measure of disorder: this is a far-reaching concept, which comes from Boltzmann's new explanation. Surprisingly, we can make a method to measure disorder, that is, the probability of a special state-defined as the number of atomic aggregation. He expressed it very accurately: S=KlogW S is entropy, which is directly proportional to the logarithmic value of the probability w of a given state, and k is a proportional constant, which is now called Boltzmann constant. Without Boltzmann, our progress would go backwards for decades, maybe a hundred years. His immortal formula S=KlogW is engraved on his tombstone. Entropy is the earliest symbol of thermodynamics, which indicates the average heating degree of a system. Then, this concept was used for reference by many other disciplines, resulting in more concepts. However, no matter how it changes between disciplines, the concept it expresses is always the same, that is, the average degree of material distribution in the system. Entropy has now become a broad concept, not unique to physics. Entropy is a physical concept, which often appears out of order in daily language. However, entropy is very different from disorder in common sense. The second law of thermodynamics says that the entropy of a closed system cannot be reduced. The so-called closed system is a system in which neither mass nor energy can freely enter or leave.