This doctor, who is called "crazy", is named Meyer (18 14~ 1878), a German. 1840 began to practice medicine independently in Hamburg. He always asks why, and must observe, study and experiment in person. 1840 came to Indonesia with the fleet on February 22, with doctors on board. One day, the fleet landed in Calcutta, and the crew got sick because of acclimatization, so Mayer bled the crew according to the old method. In Germany, you only need to insert a needle into the patient's vein to treat this disease, and you can release a stream of dark red blood, but here, it is still bright red blood flowing out of the vein. Therefore, Meyer began to think: human blood is red because it contains oxygen, which burns in the human body to generate heat and maintain the body temperature. It's very hot here, and people don't need to burn so much oxygen to maintain their body temperature, so the blood in the blood vessels is still bright red. So, where does the heat come from? A heart with a maximum of 500 grams can't generate so much heat by its movement, and it can't maintain a person's body temperature alone. That body temperature is maintained by the whole body's flesh and blood, which comes from the food people eat. Whether they eat meat or vegetables, they must come from plants, and plants grow by the light and heat of the sun. What about the heat of the sun? If the sun is a piece of coal, it can burn for 4600 years, which is of course impossible. It must be something else, energy we don't know. He boldly introduced that the center of the sun is about 27.5 million degrees (now we know it is150,000 degrees). The more Meyer thinks about it, the more it boils down to one point: how is energy transformed (transferred)?
On his return to Hamburg, he wrote an article "On the Force of Inorganic Boundary" and measured the thermal mechanical equivalent of 365 kg m/kcal by his own method. He submitted a paper to the Yearbook of Physics, but it was not published, so he had to publish it in a little-known medical journal. He gave speeches everywhere: "Look, the sun gives off light and heat, and plants on the earth absorb them and produce chemicals ..." But even physicists couldn't believe his words and called him "crazy" disrespectfully. Meyer's family also suspected that he was crazy and asked a doctor to treat him. Not being understood, he finally committed suicide by jumping off a building.
Meyer was accompanied by an Englishman, Joule (18 18~ 1889), who studied chemistry, mathematics and physics under Dalton's door since childhood. He manages the brewery left by his father while doing scientific research. In 1840, he found that when live wires were put into water, the water would heat up. Through precise experiments, he found that the heat generated by electrified conductor is directly proportional to the square of current intensity, and the resistance of conductor is directly proportional to the electrified time. This is Joule's law. 184 1 year1October, and his paper was published in the Journal of Philosophy. Later, he found that regardless of chemical energy, the heat generated by electric energy is equivalent to a certain work, that is, 460 kg m/kcal. From 65438 to 0845, he took his experimental instruments and reports to attend the academic conference held in Cambridge. He finished the experiment on the spot and declared that the force (energy) of nature is indestructible. Where mechanical power (energy) is consumed, considerable heat will always be obtained. But the famous scientists in the audience shook their heads at this new theory, and even Faraday said, "This is impossible." There is also a math professor named William Thomson (1824~ 1907). He went to college with his father at the age of 8 and was admitted to college at the age of 10. He is a wizard. Today, when he heard a brewer shouting some strange theories here, he left the meeting on the spot very rudely.
Joule paid no attention to people's incomprehension. He went home to continue his experiment. He has been doing it for 40 years. He refined the mechanical equivalent of heat to 423.9 kg m/kcal. 1847, he came to the meeting place of British Science Association with his newly designed experiment. Under his strong pleading, the chairman of the meeting gave him little time to do experiments without giving a report. When demonstrating his new experiment in public, Joule explained: "You see, mechanical energy can be converted into heat quantitatively, and conversely, the heat of 1000 kcal can also be converted into work of 423.9 kg m …" Suddenly, someone in the audience shouted: "Nonsense, heat is a substance, a pyrogen, and has nothing to do with work." It's Tang Musun. Joule calmly replied, "heat can't do work, so why does the piston of a steam engine move?" If energy is not conserved, why can a perpetual motion machine never be built? "Joule insipid words suddenly let the audience was silent. The professors in the audience couldn't help thinking seriously. Some people looked around in front of Joule's instrument, and some people began to argue.
After Tang Musun touched the nail, he began to think. He began to do his own experiments and find his own information. Unexpectedly, he found an article published by Meyer a few years ago, with the same idea as Joule! He took his experimental results and Meyer's paper to find Joule. He decided to humbly apologize and asked Joule to discuss the discovery with him.
Tang Musun met Joule in the brewery and looked at all kinds of homemade instruments in Joule's laboratory. He was deeply moved by Joule's perseverance. Tang Musun took out Meyer's paper and said, "Mr. Joule, it seems that you are right. I came to apologize today. You see, I didn't think you were right until I read this paper. " Joule's face lit up when he saw the newspaper. "Professor Tang Musun, it's a pity that you can't discuss this problem with him anymore. Such a genius committed suicide by jumping off a building because he was not understood. Although he didn't fall to death, he was already insane. "
Tang Musun bowed his head and remained silent for a long time. After a while, he looked up and said, "I'm sorry, I didn't know my sin until now." In the past, how much pressure did we people give you? Please forgive me, a scientist sometimes behaves very ignorant in front of new ideas. "Everything became clear, two people sit side by side, began to study the experiment.
1853, they finally completed the accurate expression of the law of energy conservation and transformation.
There are three expressions of the law of conservation of energy transformation: perpetual motion machine cannot cause, the law of conservation of energy transformation and the first law of thermodynamics. These three expressions are described in the literature as follows: "The first law of thermodynamics is the law of conservation of energy." According to the law of conservation of energy, ... the so-called perpetual motion machine must be built. Conversely, the law of conservation of energy can also be deduced from the failure of perpetual motion machine. "It is not difficult to see here that the three expressions are completely equivalent. But the author believes that this kind of equivalence is the modern value given to them by modern people. From the perspective of historical development, we will find that the three expressions have their own continuity, but there are also differences. This difference reflects the different stages of human cognition.
Empirical expression of 1 law-perpetual motion machine can't cause it (1475 ~ 1824)
A long time ago, human beings began to use natural forces to serve themselves. In the thirteenth century, the desire to make perpetual motion machines began to sprout. /kloc-in the 5th century, the great artist, scientist and engineer Leonardo da Vinci (1452 ~ 1519) also devoted himself to the study of perpetual motion machines. He once designed a very clever hydrodynamic machine, but it didn't last forever after it was built. 1475, Leonardo da Vinci summed up the lessons of his own failure in history and came to an important conclusion: "perpetual motion machine is impossible." At work, he also realized that the reason why the machine can never move should be related to friction. Therefore, he made an in-depth and effective study of friction. However, Leonardo da Vinci never gave a scientific explanation for why friction hindered the movement of machines, that is, he could not recognize the essential relationship between friction (mechanical movement) and thermal phenomena.
Since then, although people are still committed to the development of perpetual motion machines, some scientific workers have come to the conclusion that perpetual motion machines cannot be caused, and regard it as an important principle in scientific research. Stevin (1548 ~ 1620), a Dutch mathematical mechanic, applied this principle in 1586 and deduced the parallelogram rule of output for the first time through the analysis of "Stevin chain". Galileo also applied this principle in proving the law of inertia.
Although the application of this principle has made such remarkable achievements, people's enthusiasm for developing perpetual motion machines has not diminished. Huygens (c Huygens 1629 ~ 1695)
This view is reflected in the book Pendulum Clock published by him 1673. In the book, he applied Galileo's research results on inclined plane motion to curved motion, and concluded that when an object rotates around the horizontal axis under the action of gravity, its center of mass will not rise above the height when it falls. So he came to the conclusion that it is impossible to make a perpetual motion machine by mechanical means; But he thinks perpetual motion machines can still be made of magnets. In view of this situation, 1775, the Paris Academy of Sciences had to announce that it would no longer accept the invention of perpetual motion machines.
In history, the young French scientist sadi carnot (1796 ~ 1832) made the most brilliant scientific achievements by applying the principle that perpetual motion machines cannot be made. 1824, he combined this principle with heat theory and deduced the famous Carnot theorem. This theorem points out the direction for improving the efficiency of heat engine and lays the foundation for the second law of thermodynamics. But what needs to be emphasized here is that although Cano applied the principle that a perpetual motion machine cannot lead to a heat engine to a heat engine, his thinking method is still "mechanical". In his argument, he compared the flow of heat from a high-temperature heat source to a low-temperature heat source with the flow of water from a high place to a low place, and thought that heat pushes a heat engine to do work just like water pushes a turbine to do work, and there is no loss of water and heat in the flow.
It can be seen that from 1475, when Leonardo da Vinci put forward "water motive can't cause it" to 1824, Carnot introduced "Carnot theorem", which can only be applied to mechanical motion and "heat and mass" flow. It is far from the law of energy transformation and conservation in the modern sense, it can only be the experience summary of energy conservation in mechanical movement and the original form of the law.
189 1 year, Helmholtz (H. Helmholtz1821~1894) 400)
Looking back on his research on the causes of the conservation law of force, he said, "If perpetual motion machine is impossible, what kind of relationship should exist between different forces under natural conditions?" Moreover, do these relationships actually exist? "It can be seen that' perpetual motion machine can't cause' is still superficial, and people still have to work hard to understand its profound connotation.
The Original Expression of Law 2-Conservation of Force (1824 ~ 1850)
The law of energy conversion and conservation must be put forward on the basis of 134: correctly understand the essence of heat; Discover the transformation between various forms of material movement; Corresponding scientific ideas. In the19th century, all three conditions were met.
1798, Rumford (cromford1753 ~1814) submitted an experimental report on the thermal motion theory obtained from the gun barrel experiment to the Royal Society. 1800, David (D·H· David 1778 ~ 1829)
The experiment of melting ice cubes by rubbing them in vacuum supports Renford's report. 180 1 year, Thomas Young (1773 ~ 1829) said that light and heat have the same properties, and emphasized that heat is a kind of movement. From then on, the theory of thermal motion gradually replaced the theory of heat.
At the turn of 18 and 19 centuries, the mutual transformation between various natural phenomena was discovered one after another: after the chemical effect of heat transforming into work and light was discovered, the thermal effect of infrared rays was discovered in 1800. As soon as the battery was invented, the thermal effect and electrolysis of current were discovered. 1820 discovered the magnetic effect of current, and183/kloc-0 discovered the electromagnetic induction phenomenon. Thermoelectric phenomenon was discovered in 182 1 year, and its inverse phenomenon was discovered in 1834. Wait a minute.
At the turn of the century, the idea of taking nature as "vitality" developed into "natural philosophy" in Germany. This philosophy regards the whole universe as the product of historical development caused by the discovery of some fundamental force. From this perspective, all natural forces can be regarded as one thing. At that time, this philosophy was dominant in Germany and some western European countries.
At this time, it is imperative to put forward the principle of conservation of force.
In history, Kano was the first person to put forward the idea of converting thermal energy into work. He thinks: "heat is just a kind of power, or just a kind of movement in different forms." Heat is a kind of exercise. For a small part of an object, if the force is destroyed, at the same time, it will inevitably produce heat that is strictly proportional to the destructive force. On the contrary, where heat disappears, there must be electricity. Therefore, it can be established that the size of power is essentially unchanged. More precisely, the size of power can neither be produced nor destroyed. "At the same time, he gave a rough numerical value of the mechanical equivalent of heat.
Unfortunately, Kano's idea was discovered in 1878, 46 years after his death. Prior to this, 1842, Mayer, Germany (J R Mayer1814 ~1878) 400).
He was the first person to publish a comprehensive paper on the conservation of force and inorganic boundary force. In this paper, starting from "natural philosophy", he released 25 forms of force transformation from the causal chain of "cause equals effect" in a speculative way. In 1845, he also used the difference between constant pressure specific heat capacity and constant volume specific heat capacity: Cp-Cv=R, and calculated the equivalent value of thermal work as 1 card, which is equal to 365 g m.
1843, British experimental physicist Joule (J P Joule1818 ~1889) 400) style. width = 400; " & gt
In the Journal of Philosophy, he published an experimental report on measuring the mechanical equivalent of heat. Since then, he has done more and more detailed work and determined more accurate equivalent values. In 1850, he published the result: "To produce one pound of water (weighed in vacuum at a temperature of 55-60℃) and increase the heat of 1 Fahrenheit, it takes 772 pounds of mechanical work represented by falling one foot." Joule's work laid a solid experimental foundation for the principle of "conservation of force".
Helmholtz, a German scientist, published his book The Conservation of Force in 1847. In this paper, he proposed that all natural phenomena should be explained by the motion of particles interacting with the central force.
This proves that the sum of vitality and tension is conservative to the central force. In the introduction, he also discussed the relationship between thermal phenomenon, electrical phenomenon, chemical phenomenon and mechanical force, and pointed out the possibility of applying the principle of "conservation of force" to living things. Because Helmholtz's way of discussion is very physical, his influence is greater than that of Meyer and Joule.
Although, so far, the discoverer of this law still calls energy "force"; Moreover, the expression of the law is not accurate enough, but in essence they discovered the law of energy transformation and conservation. Comparing the two expressions, we can see that "conservation of force" is much more profound than "perpetual motion machine cannot cause". "Conservation of force" refers to all forms of material motion when it is recognized; At the same time, it is a theory established by axiomatic structure (Helmholtz) under the guidance of certain philosophical thought (Meyer) and on the basis of experiment (Joule). If we still use "perpetual motion machine can not be caused" to express this law, it has given it a new connotation, that is, the present machine can be mechanical, thermal, electromagnetic, chemical and even biological; At the same time, it also reveals the reason why perpetual motion machine can't move forever.
In addition, we should also see that although the principle of "conservation of force" has the relationship between Joule's thermal mechanical equivalent and electrothermal equivalent, as well as various relationships deduced by Helmholtz, they are independent and cannot be expressed by a unified analytical formula. So "conservation of force" is not mature enough.
Law 3- Analytical expression of the first law of thermodynamics (1850 ~ 1875)
To express the law analytically, only the concepts of heat, work, energy and internal energy can be accurately defined.
As early as the eighteenth century, the concept of "heat" was given, that is, the quantity of heat and mass. 1829, Poncelet (J V Poncelet 1788 ~ 1867) clearly defined work as the product of force and distance in the process of studying steam engines. The concept of "energy" is 17 17, which was adopted by J. Bernoulli (J. Bernoulli 1667 ~ 1748) when discussing virtual displacement. Thomas Yan called the Force energy in 1805 and was used. Thomas Yan called force energy in 1805, and thus defined Young's modulus. However, their definition has never been accepted by people. No wonder Meyer, Joule and Helmholtz also used "force" as energy. This is extremely unfavorable to the expression of the law, and the influence of the theory of heat is far from being eliminated, so the principle of "conservation of force" has not been accepted by most people. Of course, there are also a group of people of insight who realize the great significance of this law and have done fruitful work for its perfection. The most famous of them are W. Thomson (W. Thomson 1824 ~ 1907) in Britain and Clausius (R. Clausius 1822 ~ 1888) in Germany, who put forward the first and second laws of thermodynamics on the basis of predecessors.
1850, clausius published a paper on the power of heat and the laws of heat itself that can be deduced from it in the 79th volume of the German Annual Report of Physical Chemistry. It is pointed out that Carnot theorem is correct, but it must be proved by thermal motion theory and other methods. In his view, the only principle is that "in all cases where work is generated by heat, there is a heat that is directly proportional to the work generated, and conversely, this heat can be generated by consuming the same amount of work." Is not enough; Another principle is that "any amount of heat can be transferred from a cold object to a hot object without any force consumption or other changes, which is contrary to the behavior of pyrogen." To prove it. He said that only this paradox can heat be regarded as a state quantity. Then he did the following very important work:
For permanent gases, the following equation holds:
pV=R(273+t) ( 1)
P is the pressure, V is the volume per unit mass, and T is the temperature in degrees Celsius. Considering the tiny Carnot cycle, the work done by this process can be obtained from (1):
At the same time, the heat consumed in this process can also be calculated:
Let the mechanical equivalent of thermal coefficient be a, and apply Joule principle to obtain from (2) and (3):
At this time, Clausius introduced a new state function U, and Formula (4) became:
For this new state function, he pointed out that "its nature is like what people usually say, assuming that it is total heat, a function of V and T, and it is completely determined by the initial state and final state of the change process."
U=U(V，t) (6)
In this way, he came to the analytical formula of the first law of thermodynamics:
dQ=dU=dW (7)
As we know, a knowledge field only becomes a science when it develops to reveal and grasp the relationship between the regulation and quantity of the object, that is, when mathematical tools are used. Therefore, only at this time, the laws of energy transformation and conservation, together with the expression of entropy of the second law of thermodynamics, constitute the basis of the theoretical system of thermodynamics.
1853, w Tang Musun redefined the definition of energy. He put it this way: "We express the energy of a material system in a given state as the sum of various actions produced outside the system and measured by mechanical work units when it transitions from this given state to any fixed zero state in any way." He also called the state function internal energy. Until then, people began to distinguish Newton's "force" from "energy" which represents the movement of matter, and it was widely used. On this basis, Scottish physicist Rankin * (W J M Rankin 1820 ~ 1872) changed the principle of "conservation of force" to "conservation of energy".
After the establishment of thermodynamic theory, many people still find it difficult to understand, especially the second law. Therefore, since 1854, Clausius has done a lot of work, trying to find an acceptable proof method to explain these two principles (then called principles), and preached them in popular language many times. In this way, it was not until about 1860 that the energy principle was generally recognized.
Accurate expression of the law-the law of energy transformation and conservation (1875 ~ 1909)
1860 years later, the law of energy "soon became the cornerstone of all natural sciences. Especially in physics, every new theory must first test whether it conforms to the principle of conservation of energy. " However, before this, the discoverer of this principle only focused on summarizing the name of the law from the conservation of quantity, without emphasizing the transformation ratio of motion. When was the principle summed up as "the law of energy conversion and conservation"? The answer to the question can be obtained from Engels' exposition in Anti-Turin.
Engels said: "If the great basic law of motion newly discovered ten years ago is only summarized as the law of conservation of energy, only as the expression that motion is immortal, that is, only from the quantitative aspect, then this narrow and negative expression is increasingly replaced by the positive expression about energy transformation, in which the qualitative content of the process has gained its own rights for the first time. ..... "Engels published this passage in 1885. He said that negative expressions ten years ago were increasingly replaced by positive expressions. Judging from this, the accurate and perfect expression of the Law of Energy Transformation and Conservation should be formed at 1875 or later.
So far, it seems that all the legal problems have been solved. Actually, it is not.
We know that heat, an important basic concept in thermodynamics, was still defined in18th century until the beginning of 20th century, and this definition was based on the theory of heat. In other words, one of the cornerstones of the building of thermodynamics is still unstable. Therefore, in 1909, C. Carathieodory redefined internal energy: "Any object or system of objects has a state function U in equilibrium, which is called its internal energy. When this object undergoes an adiabatic process from the first state to the second state, its internal energy increase is equal to the work W done by the outside world in this process. "
U2-U 1=W (8)
The internal energy defined in this way has nothing to do with heat, but only with mechanical energy and electromagnetic energy. On this basis, heat can be defined in reverse:
Q=U2-U 1-W (9)
Until this time, the first law of thermodynamics (the law of energy transformation and conservation), the second law and the whole thermodynamic theory completely broke away from the theory of heat.
Throughout the whole paper, we can see that the three expressions of the law of energy transformation and conservation reflect the course of human understanding of this natural law. Each of these three expressions is more profound and closer to the objective truth than the other. This is how human beings understand the material world step by step.