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The mystery of irreversibility: why natural processes can never return to their initial state?
In science, a process that cannot be reversed is called an "irreversible process", and this concept appears frequently in thermodynamics. Many complex natural processes in life are irreversible, meaning they cannot simply be restored to their original state. This article will explore the root causes of irreversible processes and their practical impacts in nature.
In nature, heat dissipation and increase in entropy are signs of irreversible processes.
In thermodynamics, the thermodynamic state of a system and all its surroundings cannot be restored exactly to its initial state, which requires energy consumption. Even if the changes in an ozone layer were independent of time, the irreversibility of the process would still be obvious. Once an irreversible change occurs, such as the transition of heat from a heat source to a cold source, the reverse of this process requires additional energy input, which is the fundamental reason for the increase in entropy.
Entropy, an important concept in thermodynamics, is usually interpreted as the degree of disorder. In an irreversible process, the entropy of the system and its surroundings always increases. According to the second law of thermodynamics, the total entropy of any isolated system cannot decrease over time, making the irreversibility of natural processes a fundamental fact.
In thermodynamics, a process is irreversible because energy is dissipated and heat cannot be recovered.
From an experimental point of view, the perturbation of a system undergoes a small change in state, that is, from one thermodynamic state to another, and the intermolecular interactions, collisions, and loss of heat involved in the process lead to irreversibility. For example, in a diesel engine, the more uniform the combustion process is, the higher its efficiency is, the less energy is lost, and therefore the closer it is to a reversible process.
History of Irreversible Processes
German physicist Rudolf Clausius first mathematized irreversibility in the 1850s and introduced the concept of entropy. His 1854 work showed that heat within a system cannot spontaneously transfer from a colder to a hotter body, which became an important basis for irreversible processes. This phenomenon is very easy to observe. For example, if a cup of hot coffee is placed in a room temperature environment, it will continue to lose heat to the outside and cool down.
The flow of heat from a hot source to a cold source is irreversible; this is one of the fundamental laws of nature.
Due to the contradiction between microscopic analysis and macroscopic observation, this has led to the theoretical exploration of many irreversible processes. Many processes that appear to be reversible in daily human life are actually constrained by increasing entropy. For example, a local equilibrium state will break down on its own over time and further enter a higher entropy state.
Examples of Irreversible Processes
In the field of physics, many processes are considered to be irreversible, and the reality of these processes has been confirmed experimentally. Here are some examples of spontaneous events:
- Aging
- Death
- Heat conduction of temperature difference Friction
- Current flowing through a resistor
- Instantaneous chemical reaction
- Randomly mix substances of different ingredients
For example, the Joel expansion is a classic example of thermodynamics that shows how entropy increases by opening up a gas, releasing it from one bubble into another. During this process, the gas is evenly distributed throughout the container, and when attempts are made to compress the gas back to its original state, the change in internal energy leads to a loss of stability and creates irreversibility in the system.
Irreversibility in Complex SystemsThe irreversibility of events is particularly evident in complex systems, such as organisms or ecosystems. According to biologists Timmawa and Francis Varela, the continued existence of living organisms, self-organizing systems, depends on their own ability to self-generate. At the same time, physicist Ilya Prigogine points out that the occurrence of irreversible events in such complex systems (such as death or species extinction) indicates the end of the self-organization process, which cannot be recovered at either the microscopic or macroscopic level.
In general, although the approximate reversibility of some processes can be achieved under certain conditions, the vast majority of natural processes are irreversible, which makes us think: In such an irreversible universe, how can we How can we understand the meaning of time and its passage?
