1840Indian rebirth

"Why?" Many people can't help but ask, "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." Ma Shao paused, "This law that has not yet been clarified is the topic of my speech today - thermodynamics

Second Law."

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

Compared with other disciplines, the development of thermodynamics is closer to a gradual process, such as the law of conservation of energy. Some scientists have been vaguely aware of it for a long time, but it has only been made clear in recent years.

The same goes for 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 revisiting 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. Ma Shao will explain the second law of thermodynamics thoroughly.

"Second law?" Faraday couldn't help but said, "It sounds very interesting."

Ma Shao said: "The first law tells us that energy is neither created 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.

"About this rule, to put it bluntly, it is impossible to transfer heat from a low-temperature object to a high-temperature object 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 if 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. However, 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 the law of conservation of energy and Carnot's theorem are correct, then obviously another law is needed to support this system, which is the second law of thermodynamics - although energy can be converted into each other, it has direction limitations.

This principle is not complicated, and many physicists understand it after Jing Mashao said it.

"I see!"

"That's absolutely correct. Without this law, Carnot's theorem would not be true."

"This is indeed of critical significance and can definitely be regarded as 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, I missed something!"

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

Apparently, they believed that discovering the second law of thermodynamics was a matter of luck.

This is true. The physical laws described in such a rough manner have little technical content and are difficult to convince people.

So Mashao continued: "Of course, this is just a rough description. It doesn't look like a law of physics, but like a philosophical motto."

"Like Newton's work, physics is a combination of philosophy and mathematics... Therefore, in order to make it a true physical law, we need to explain it in mathematical language, and we need to introduce a concept that can be calculated - entropy."

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

Ma Shao did not use the English name of entropy that he knew in his previous life. Instead, he used the Apache word "original calamity", a religious terminology from the Spiritual Enlightenment Sect, which the British would naturally find difficult to pronounce.

"This is an Apache word, which means 'original catastrophe', similar to original sin." He explained, "In fact, it is indeed a religious word, and my people have given this word some religious concepts."

"What religion do the Apaches believe in?" People are inevitably curious.

So Ma Shao first introduced the Spiritual Enlightenment Sect in general, and then changed the subject: "Of course, I don't advocate religion very much. I have been suggesting that people follow a more rational way of thinking... Anyway, at least here, a

Let’s talk less about religious topics at physics conferences.”

There is no doubt that the religion described by Mashao aroused people's curiosity, which is what he wanted.

But he didn't say much. After all, he couldn't be a missionary, and it wasn't the right time to do so.

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

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

With that said, Ma Shao 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, based on Carnot's conclusion, we get this result..."

For many physicists here, these are familiar contents and are not difficult to understand.

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

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

Faraday was born in poverty and did not receive much formal education. Far from being a physicist proficient in mathematics, his work was basically in the experimental field. It was his excellent hands-on ability and physical intuition that made him a first-class physicist.

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

His shortcomings in mathematics were also the reason why he failed to advance his research on electromagnetism. Fortunately, soon, the young and talented Maxwell would complete this mission for him.

After a while, Ma Shao circled a variable in the formula and said: "This variable, or 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 an irreducible value, and the entropy change must be greater than or equal to zero. The inability to reduce entropy 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 we say that discovering the second law of thermodynamics can rely on luck, but extracting mathematical expressions from this law is absolutely impossible without a solid foundation of skills.

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

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

"Bah bang bang—" As he applauded, other physicists also applauded.

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

But then he stopped smiling and changed the subject: "However, this is not the final result of my thinking, and it is far from the true face of the second law of thermodynamics."

The applause quickly died down, 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 was not the result?

Facing everyone's puzzled looks, Ma Shao looked calm and said slowly: "We have used mathematics to express the second law of thermodynamics, but I think you have all noticed that the concept of 'entropy' does not seem to have actual physical meaning.

correspond."

"This question has troubled me for a long time. After long-term thinking, I got a relatively satisfactory answer. It is precisely because of this answer that I named the variable 'entropy' - 'original calamity' in Apache language.

'."

After a pause, Mashao added: "Next, let's discuss the nature of 'entropy'."