1840 Indian Rebirth

Chapter 192 [Entropy]

"Why?" Many people couldn't help asking, "This does not violate the law of conservation of energy."

"Yes, the second type of perpetual motion machine does not violate the law of conservation of energy, but it violates another law." The horse whistle paused, "This law that has not been clarified is the topic of my speech today - thermodynamics Second law."

He said "not yet identified", not "not yet discovered".

The development of thermodynamics seems to have been more incremental than that of other disciplines.For example, the law of conservation of energy has long been vaguely realized by some scientists, but it has only been clarified in recent years.

The same is true of the second law of thermodynamics. Some keen physicists have also been vaguely aware of the existence of this law, but they can't explain it clearly, separated by a thin layer of window paper.

At this time, as long as physicists look back at Carnot's theorem carefully, it is not difficult to realize the existence of the second law of thermodynamics.

In fact, in the original history, two or three years later, after re-examining Carnot's theorem, Clausius and Kelvin would respectively give their understanding of this law.

But now, Clausius and Kelvin obviously don't have this opportunity, and the horse whistle will explain the second law of thermodynamics thoroughly.

"The second law?" Faraday couldn't help but say, "Sounds very interesting."

Ma Shao said: "The first law tells us that energy is neither born nor destroyed, but can only be transferred, while the second law talks about the rules of energy transfer—energy cannot be transferred at will."

"Nature always limits us more than we think," he interjected.

"The rule of this kind, stated bluntly, is that it is impossible to transfer heat from a low-temperature body to a high-temperature body without causing other changes."

"After knowing the first law of thermodynamics, we look back at Carnot's theorem. It is not difficult to find that the second law of thermodynamics is actually the premise of Carnot's theorem. Only when it is established can Carnot's theorem be established..."

There was a lot of discussion in the audience.

The law of conservation of energy tells people that heat and work are equivalent and can be converted into each other, but the heat and work described by Carnot's theorem are not exactly the same. Work can be completely converted into heat, but not vice versa.

If both the law of conservation of energy and Carnot's theorem are correct, then obviously, another law is needed to support this system, that is, the second law of thermodynamics-although energy can be transformed into each other, there is a limit to the direction.

This reason is not complicated, and many physicists have understood it after the horse whistle said.

"I see!"

"That's right, without this law, Carnot's theorem cannot be established."

"It's really critical, and definitely the second most important law of thermodynamics."

"Damn, I noticed this problem not long ago, but I didn't think about it!" Several physicists were annoyed, "God, what did I miss!"

"He is such a lucky guy!" Some people looked at the horse whistle on the stage and couldn't help saying sourly.

Apparently, they thought the discovery of the second law of thermodynamics was luck.

That's right, such a rough description of the laws of physics is really not technical, and it's hard to convince people.

So Horse Whistle continued: "Of course, this is just a rough description. It doesn't look like a law of physics, but a maxim of philosophy."

"Just like Newton's writings, physics is a combination of philosophy and mathematics... Therefore, in order to make it a real physical law, we need to express it in mathematical language, and we need to introduce a concept that can be calculated-entropy."

"Entropy?" The people in the audience were confused and tried to repeat this awkward name.

Horse Whistle did not use the English name of entropy that he knew in his previous life, but used the Apache language "Original Calamity", a religious term of the Spiritual Sect, which the British would naturally find awkward.

"It's an Apache word, meaning 'primordial catastrophe', similar to original sin." He explained, "In fact, this is indeed a religious word, and my people have given this word some religious concepts."

"What religion do the Apache people believe in?" one can't help but wonder.

So Ma Shao first gave a general introduction to the Spiritual Spell, and then changed the topic: "Of course, I am not advocating religion very much. I have always suggested that people follow a more rational way of thinking... Anyway, at least here, a Let's talk less about religion at physics conferences."

There is no doubt that the religion described by Horse Whistle arouses people's curiosity, which is what he wants.

But he didn't say much, after all, he can't be a missionary, and it's not an occasion for missionary right now.

"Here, original calamity or entropy is a purely physical concept. The connotation of entropy is very complicated. Since I thought of it a few years ago, until now, my understanding of it has been constantly revised."

"First, let's review Kano's work."

With that said, the horse whistle turned around again and wrote some formulas on the blackboard behind the podium.

"We can differentiate any thermal cycle process and reduce it to a thermal cycle process superimposed by a large number of Carnot heat engines. Next, according to Carnot's conclusion, we get this result..."

For many of the physicists here, these are all familiar and easy to understand.

Except, of course, for those physicists who don't know calculus - and there are such physicists.

For example, Faraday's calculus level is very doubtful, and there is a high probability that he does not understand it.

Faraday was born in a poor family without much formal education. Far from being a physicist proficient in mathematics, his work is basically in the field of experiments. It is his excellent hands-on ability and physical intuition that make him a first-class physicist.

It can be said that among physicists of the same rank, Faraday's mathematics level may be the worst one.

The short board in mathematics is also the reason why he failed to further the research of electromagnetism. Fortunately, the young and talented Maxwell will complete this mission for him in the near future.

After a while, Ma Shao circled a variable in the formula and said, "This variable, or the state function, is what I call 'entropy'."

The variable he circled is naturally Clausius entropy, which is also the earliest definition of "entropy".

"... Now, it is not difficult for us to find that for an isolated system, its entropy is a value that cannot be reduced, and the entropy change must be greater than or equal to zero. The entropy cannot be reduced, which reflects the directionality of energy transformation."

"The inequality here is the mathematical expression of the second law of thermodynamics." He pointed to the Clausius inequality on the blackboard.

After this operation, the physicists present had to be convinced.

If it is said that discovering the second law of thermodynamics can rely on luck, but it is absolutely impossible to extract a mathematical expression from this law without a solid foundation.

"Entropy...I don't think it will be long before this word will appear in all textbooks." Thomson said with emotion.

"A great discovery!" Faraday couldn't help applauding. Although he couldn't understand the process of mathematical derivation, he undoubtedly felt the wonder of entropy with his extraordinary physical intuition.

"Papapa——" With his applause, other physicists also applauded.

"Thank you." Ma Shao smiled and responded politely.

But then he restrained his smile and changed the topic: "However, this is not the final result of my thinking, and it is far from the true appearance of the second law of thermodynamics."

The applause quickly subsided, and people looked at him quietly and in surprise.

In their opinion, the speech just now can be regarded as a model of physics, but the horse whistle told them that this is not the result?
Facing everyone's suspicious eyes, Ma Shao looked calm and said slowly: "We have expressed the second law of thermodynamics in mathematics, but I think you have all noticed that the concept of 'entropy' seems to have no actual physical meaning to it. correspond."

"This question has troubled me for a long time. After long-term thinking, I got a satisfactory answer. It is because of this answer that I named the variable 'entropy' - the original robbery in Apache ’, a concept that symbolizes endless catastrophe and trials.”

After a pause, the horse whistle said again: "Next, let's discuss the nature of 'entropy'."

(End of this chapter)