Maxwell's demon: fighting entropy and the second law of thermodynamics and finally coming down to business as usual!

It is instinctive for human beings to explore the unknown. Because I do not know, I am curious; because I am curious, I explore; because I explore, I discover my ignorance. People imagine all sorts of possibilities for things they can't find results for. Until the idea is confirmed or disproved. Imagining doesn't take much, only brain work. What takes effort is the process of confirming or disproving the hypothesis.

The Maxwell demon we are talking about today is an idea, but as is customary, let's introduce Maxwell first. Maxwell, full name James Clerk Maxwell. British physicist and mathematician. Founder of classical electrodynamics and one of the founders of statistical physics. 1873's On Electricity and Magnetism is also considered the most important classic of physics after Newton's Mathematical Principles of Natural Philosophy. Without electromagnetism, there would be no modern electrical technology and no modern civilization. Maxwell is therefore considered to be one of the most influential physicists in physics.

Before I talk about Maxwell's demons, I need to mention what I have said before. The second law of thermodynamics. For those of you who haven't read my previous article, that's okay. I will briefly explain it here. Entropy is a measure of the degree of chaos in a system. Entropy increase principle: Entropy in an isolated thermodynamic system does not decrease, but always increases or remains constant. The second law of thermodynamics (two expressions): Heat cannot be transferred spontaneously from a low-temperature object to a high-temperature object. / It is impossible to obtain heat from a single heat source and convert it completely into useful work in the absence of other influences.

The reason why entropy and the second law of thermodynamics are mentioned is to stand in opposition to them and present Maxwell's demon. I wonder if people had the same reaction as I did, a physicist imagining a monster. After understanding it, I realized that it was not really like that, it was just turned into a monster to help me understand it.

It is a mechanism that detects and controls the movement of individual molecules. Imagine an insulated container with a partition in the middle that is a 'gate', controlled by a Maxwell demon. This gate guides the faster-moving molecules through and the slower-moving molecules through. The space on the left is for the faster-moving molecules, which can only pass to the right, not to the right. The space on the right is for the slower-moving molecules. They can only pass from the left, but cannot go to the left. In this way, the otherwise chaotic molecules become relatively orderly, with the heat concentrated on one side, thus becoming the second kind of perpetual motion machine we imagine.

In fact, in simple terms, if the Maxwell demon exists, it is the equivalent of a second perpetual motion machine. One could say that the two are hardly comparable. Humans are constantly pursuing the Maxwell Demon, which they think is possible, but if they are pursuing the second kind of perpetual motion machine, we can know that it is not possible. (It has to be said that even when it is clear that perpetual motion is impossible, someone will still want to make it.)

I want to spit out one thing here. We have actually discussed many hypotheses. Often the people who come up with these hypotheses are high up in powerful fields or founders, and they are all celebrities. Their hypotheses are often unrealized or unproven, but they are not "attacked" for them. On the contrary, their hypotheses are competing for confirmation. The reason for this is simple. These people are famous, and they are justifiable, but they are not. So one can imagine that only reasonable and original hypotheses can be believed and confirmed, and only fame can make one's imagination known to a wider audience.

In 1961, the American physicist Ralph Landauer introduced Landauer's Principle, linking physics to information theory. The content was that erasing one bit of information leads to kB ln 2 heat dissipation. This principle explains why information processed by machines generates heat, i.e. energy is consumed and converted. There is no need to delve into the meaning.

Randall's colleague Bennett discovered that this principle could be applied to Maxwell's demon. After studying it, he said that Maxwell's demon consumes energy and that this energy consumption occurs when it needs to "forget" its judgment of the previous molecule and then judge the next one. In 2003, Bennett further updated Landauer's principle, arguing that any logically irreversible process of information manipulation, such as erasing a piece of information or merging two computational paths, must be accompanied by an entropy increase in degrees of freedom outside the external environment or information storage vehicle.

In this way, Maxwell's demon differs from the second perpetual motion machine. With the depletion of energy, the Maxwell demon may exist, but it also loses the magic of the second type of perpetual motion machine. However, there is another argument that Maxwell's demon holds and does not violate the second law of thermodynamics. The reason is that Maxwell's demon belongs to the microscopic world, while the second law of thermodynamics belongs to the macroscopic world, so there is no conflict between the two. Personally, however, I do not take a position on this.

Finally, I must once again praise the human mind, both in its rational reasoning and its wild imagination. We can let our ideas soar freely, unencumbered by ourselves and our circumstances. What you think may well become an important part of history. Don't limit your thinking, and don't be stuck in your ways. It is possible that thinking is what we are!

I think it is a summary of the main points :

1. Maxwell, full name James Clerk Maxwell. British physicist and mathematician. He was the founder of classical electrodynamics and one of the founders of statistical physics. 1873's On Electricity and Magnetism is also considered to be the most important physics classic after Newton's Mathematical Principles of Natural Philosophy. Without electromagnetism, there would be no modern electrical technology and no modern civilization. Maxwell is therefore considered to be one of the most influential physicists in physics.

2. Maxwell's demon was proposed in opposition to the increase in entropy and the second law of thermodynamics. It is supposed to be a mechanism that can detect and control the motion of individual molecules. Imagine an insulated container with a partition in the middle as a 'gate', controlled by the Maxwell demon. This gate guides the faster-moving molecules and the slower-moving molecules through respectively. The space on the left is for the faster-moving molecules, which can only pass to the right, not to the right. The space on the right is for the slower-moving molecules. They can only pass from the left but cannot go to the left.

3. It is found that Maxwell's demon consumes energy, which occurs when it needs to "forget" its judgment of the previous molecule and then judge the next one. This process is logically irreversible. As the energy is consumed, Maxwell's demon may exist.

4. There is another view that Maxwell's demon holds and does not violate the second law of thermodynamics. The reason is that Maxwell's demon belongs to the microscopic world, while the second law of thermodynamics belongs to the macroscopic world, so the two do not conflict.