What " maxwell's demon"And why has it been worrying the minds of great scientists for a century and a half? It's simple. Scientists are looking for such processes that would allow heat to move from bodies that are less heated to bodies that are more heated. But, we know that heat can only pass from hot bodies to cold ones. This is called the second law of thermodynamics, which was challenged by "Maxwell's demon."
The great English scientist James Maxwell tried to solve such a problem in 1871. Some fantastic creature - "Maxwell's demon" had the functions of such a mechanism. "Maxwell's Demon" possesses such sophisticated abilities that he can follow each individual molecule in its movements and know its speed. If we take a vessel divided into two parts by a partition, and the "Maxwell's demon" sits at the door in the partition, we can force him to open the door only in front of fast or only in front of slow molecules. "Maxwell's demon" will let fast molecules pass into one part of the vessel, and slow ones - into another, then in one part of the vessel both the temperature and pressure will be higher than in the other, that is, we will get an unlimited supply of energy without the expenditure of work. however, for a system consisting of the right and left sides of the vessel, in the initial state there is more than in the final state, which contradicts the thermodynamic principle of non-decreasing entropy in closed systems.
The paradox is resolved if we consider a closed system that includes "Maxwell's demon" and a vessel. For the "demon of Maxwell" to function, it is necessary to transfer energy to it from an external source. Due to this energy, the separation of hot and cold molecules in the vessel is carried out. Due to this energy, the separation of hot and cold molecules in the vessel is carried out, that is, the transition to a state with lower entropy.
With the development of the theory, it was found that the measurement process may not lead to an increase in entropy, provided that it is thermodynamically reversible. However, in this case, the demon must memorize the speed measurements (deleting them from the demon's memory makes the process irreversible). Since it is finite, at a certain moment the "Maxwell's demon" is forced to erase the old results, which ultimately leads to an increase in the entropy of the entire system as a whole.
Scientists have convincingly proved many times that "Maxwell's demon" is just a joke of the great physicist. Indeed, the "Maxwell demon" in a vessel with two molecules is not effective; in half the cases they could be in any one part of the vessel. If there are many molecules, then the probability of such a case is extremely small.
However, passions are not appeased, "Maxwell's demon" is trying to find new arguments in his defense. In one of scientific journals, in an article devoted to this problem, it is seriously said that the "Maxwell's demon" exists only in the form of a quantum generator - which separates excited molecules with high energy from unexcited molecules.
However, there is still no strong evidence that the "Maxwell demon" exists, nor strong denials of this. "Maxwell's Demon" fuels interest in further searches.
Is it possible to violate the second law of thermodynamics?
In science, as in fiction, there are fantastic characters. Perhaps most of them were invented during the discussion of the second law of thermodynamics. The most popular of these was the Maxwell demon, which was invented by James Clerk Maxwell, the author of the famous Maxwell system of equations that completely describes electromagnetic fields. The second law (or law) of thermodynamics has many formulations, the physical meaning of which, however, is identical: an isolated system cannot spontaneously pass from a less ordered state to a more ordered one. So, a gas consisting of molecules moving at different speeds cannot spontaneously split into two parts, in one of which molecules moving, on average, faster than the average speed, and in the other, slower.
Many physical processes fall into the category reversible. Water, for example, can be frozen, and the resulting ice can be melted again, and we get water in the same volume and condition; iron can be magnetized and then demagnetized, etc. In this case, the entropy (degree of order) of the system at the initial and final points of the process remains unchanged. There are also processes that are irreversible in the thermodynamic understanding - combustion, chemical reactions and so on. That is, according to the second law of thermodynamics, any process ultimately leads either to preservation or to a decrease in the degree of ordering of the system. This disharmonious situation greatly puzzled physicists of the second half of XIX centuries, and then Maxwell proposed a paradoxical solution that would seemingly bypass the second law of thermodynamics and reverse the steady growth of chaos in a closed system. He suggested the following " thought experiment»: Imagine an airtight container, divided in two by a gas-tight partition, in which there is a single door the size of a gas atom. At the beginning of the experiment, the upper part of the container contains gas, and the lower part contains full vacuum.
Now imagine that a certain microscopic watchman is attached to the door, vigilantly watching the molecules. He opens the door for fast molecules and lets them pass through the partition, into the lower half of the container, and leaves the slow ones in the upper half. It is clear that if such a mini-watchman is on duty at the door long enough, the gas will split into two halves: in the upper part there will be cold gas, consisting of slow molecules, and in the lower part, hot gas from fast molecules will accumulate. Thus, the system will be ordered in comparison with the initial state, and the second law of thermodynamics will be violated. Moreover, the temperature difference can be used to obtain work ( cm. The cycle and Carnot's theorem). If such a watchman is left on duty forever (or organized shift duty), we will get a perpetual motion machine.
This funny watchman, nicknamed "Maxwell's demon" by his witty colleagues, still lives in scientific folklore and excites the minds of scientists. Indeed, a perpetual motion machine would not harm humanity, but here's the problem: apparently, in order for Maxwell's demon to work, he himself will need energy supply in the form of an influx of photons necessary to illuminate the approaching molecules and sift them. In addition, sifting molecules, the demon and the door cannot but interact with them, as a result of which they themselves will steadily receive thermal energy from them and increase their entropy, as a result of which the total entropy of the system will still not decrease. That is, with such an explanation, the theoretical threat to the second law of thermodynamics was assigned, but not unconditionally.
The first truly convincing counter-argument came shortly after the birth of quantum mechanics. To sort the flying molecules, the demon needs to measure their speed, but he cannot do this with sufficient accuracy due to the Heisenberg uncertainty principle. In addition, by virtue of the same principle, he cannot accurately determine the location of the molecule in space, and some of the molecules in front of which he opens the microscopic door will miss this door. In other words, Maxwell's demon turns out to be a macroscopic elephant in the china shop of the microcosm, which lives by its own laws. Bring the demon in line with the laws of quantum mechanics, and he will be unable to sort gas molecules and simply cease to pose any threat to the second law of thermodynamics.
Another compelling argument against the existence of a watchman demon appeared in the computer age. Suppose Maxwell's demon is a computer automated door opening control system. The system performs bitwise processing of the incoming information about the velocity and coordinates of the approaching molecules. Having passed or rejected a molecule, the system must reset the previously ordered information - and this is tantamount to an increase in entropy by an amount equal to the decrease in entropy as a result of gas ordering when a molecule passes or rejects, information about which has been erased from the RAM of the computer daemon. The computer itself, moreover, is also heated, so that in such a model in a closed system consisting of a gas chamber and an automated throughput system, the entropy does not decrease, and the second law of thermodynamics is fulfilled.
Sorry for the demon - he was a cute character.
Show comments (41)
Collapse comments (41)
An amazingly helpless explanation for the impossibility of the Demon Maxwell!
The argument is about the quantum uncertainty of the world! Consequently, the author has no arguments against the impossibility of the existence of a demon in a model thermodynamic world, consisting only of mechanical particles. After all, if the world consists of mechanical particles, it makes no sense to say that the demon will "heat up", that he needs to "illuminate" the particles in order to determine whether to open the partition, etc.
The simple notion that the mechanical demon does not need to light or otherwise interact with particles did not occur to the professor. The demon can, knowing the initial impulses and coordinates of all the particles in the vessel, simply calculate the moments when a fast particle flies up to the partition and open it. Moreover, no heating occurs during elastic collisions, and accordingly, the entropy of the demon does not increase.
In general, the root of the professor's difficulties and all modern physics - unclear ideas about entropy. Physicists insist that this is an objective category, while its definition includes the subjective concept of "disorder", "measure of disorder". There is no objective measure of disorder.
To answer
\u003e A startling explanation for its helplessness ... the argument about the quantum uncertainty of the world is involved!
The explanation may be helpless in your opinion, but that does not change the fact that it is correct. The impossibility of the Maxwell demon is directly related to quantum uncertainty.
\u003e The demon can, knowing the initial impulses and coordinates of all particles in the vessel, simply calculate the moments when a fast particle flies to the partition and open it.
The demon cannot know anything like that. And the main reason here is precisely quantum uncertainty. But even without it, in a purely mechanical world, accurate prediction of the trajectories of molecular motion turns out to be impossible due to the effect of exponential divergence of trajectories, which is studied in the theory of mathematical billiards. An arbitrarily small error in the knowledge of the initial positions in a short time exceeds any given value.
There is one more reason. For a demon to be able to track all the positions of molecules, he must have sufficient memory and be able to change its contents as a result of influencing the molecules. Memory is a physical device and has entropy. Calculations show that the entropy that accumulates in this memory just compensates (or exceeds) its decrease in the gas. (All calculations were given in one of the articles of the journal "In the world of science" back in the 1980s, but I cannot give a link now.)
\u003e In general, the root of the difficulties of the professor and of all modern physics is unclear ideas about entropy.
Entropy is indeed a difficult concept, but in this particular issue everything is clear with it.
\u003e Physicists insist that this is an objective category, while its definition includes the subjective concept of "disorder", "measure of disorder".
You are wrong. The concept of "disorder" is not included in the definition of entropy. It is used only with a popular, and, therefore, a figurative and inaccurate explanation of this concept. Formal definitions of entropy (by the way, there are many of them) do not contain anything like this. For example, here are the two most common definitions and physics:
Entropy is a quantity proportional to the logarithm of the number of microstates realizing one macrostate in which the system under study is located (S \u003d k * ln (W)).
The increase in entropy is the energy received by the system, referred to the temperature of the system (dS \u003d qQ / T).
You can read more about this, for example, here: http://www.cultinfo.ru/fulltext/1/001/008/126/734.htm. In this rather large encyclopedic article about the "measure of disorder" is mentioned only once, and that one as an explanation to the equation S \u003d k * ln (W).
To answer
\u003e\u003e The impossibility of Maxwell's demon is directly related to quantum uncertainty .... The demon cannot know anything like that. And the main reason here is precisely quantum uncertainty ... In order for a demon to track all the positions of molecules, he must have sufficient memory and be able to change its contents as a result of influencing the molecules. Memory is a physical device and has entropy.
HaHa. HaHaHA. The demon also needs handles and legs to open and close this door. And you need to eat ... Is this riddle still being solved with such vulgar excuses using smart words such as entropy, quantum uncertainty ... the memory of the demon (!!!) It's funny by God.
There is no demon. Imagine a room filled with bouncing balls - perfectly elastic and not subject to friction (a permissible mechanical analogy of gas molecules). On one side, there is an opening in the room, enclosed by a barrier of some height. Balls jumping above this barrier will eventually fly out of the room into the next room, and in the first there will only be sluggishly jumping balls. Does a barrier need memory or energy, photons, muons, bosons or synchrophasotorons? Does he need to calculate any enropy or attract astral forces? In order to immediately suppress the inclinations on the topic "from the next room the fast balls will return back", we will make a funnel in the second room through which the balls fly into the third room, and it is difficult for them to fly back.
In electronics, the barrier effect (electrons with energies above a certain value without loss (!) Pass the barrier, those that do not - do not pass, but they do not lose energy either) has long been known and is being used with might and main. Look on Google - for general development.
The "paradox" of these balls and, accordingly, Maxwellian vessels can be solved very simply - the very fact of sorting the balls is not work. Work is using (taking away) the energy of fast balls. And once we use (take away) the energy from the ball, we turn it into a slow one - which will not jump over the barrier. To continue the cycle, you need fresh balls from the outside.
\u003e\u003e With that said, I recommend when discussing scientific issues... trust your fantasies a little less.
And I would recommend you not to refer to stupid superstitions just because smart and fashionable words appear there ...To answer
Generally speaking, there are no completely closed systems in nature; this is an abstraction for deriving thermodynamic formulas. And in our reasoning, we don't even notice how we inadvertently move to open systems. And in open systems, entropy must be treated as follows from the work of Ilya Prigogine. But that is not the point now.
Maxwell's demon breaks the closure of the system, even if it sits inside the vessel.
Firstly, he needs an inflow of energy to do his job (the batteries must be charged), and secondly, the information that is embedded in this robot (demon) is also given FROM OUTSIDE, that is, there is an exchange of energy and information with the external environment.
And under these conditions, the work of the demon may well provide a solution to the Maxwell problem: the molecules will be distributed in speed. BUT! Thanks to the governing influence of the external rational principle.
To answer
You can think of a mechanical Maxwell demon that will let through not molecules, but faster small particles in Brownian motion. Then quantum mechanics and thermodynamics do not work, only mechanics, and everything depends on the energy consumption by the demon to fix the particle, close the door, and the speed of the particles themselves, which depends on the temperature of the environment.
To answer
The law of thermodynamics in this thought experiment of Maxwell is really violated (SELF-TRANSITION INTO A MORE ORDERED STATE!), But there is no need to fool your head because of the costs of opening-closing and heating the "valve" (let's say there is a membrane-diode - this is a technology problem, and not theoretical physics).
So, having sorted the molecules in the way described above, we get: the temperature of the fast molecules is higher than the initial one, BUT THE TEMPERATURE OF THE SLOW ones is PROPORTIONALLY BELOW. Consequently, the overall ordering of the system has not yet changed here (not counting the costs of the "sorter"). Let's say they are negligible.
Further, using the energy of fast molecules, for example, to perform work, we thereby lower their temperature, and, consequently, the overall temperature of the entire system. Having performed these manipulations with the gas a number of times, as a result, we will approach absolute zero, and then the process of extracting energy by this method will become impossible. (So \u200b\u200bit’s not clear to me which perpetual motion machine the article is talking about). So we extracted energy, lowered the temperature, and increased the orderliness too much? molecules in this system. (they also increased the volume of gas - what about the order?).
This means that a closed system can self-cool down to 0 (in exchange for the release of an equivalent amount of energy minus the efficiency of the "sorter"), i.e. moving to a more orderly one? (and volume?) state, and SELF-TRANSITION INTO A MORE ORDERED STATE is not allowed by the 2 law of thermodynamics.
It seems to me that the amount of energy that was needed to create initial conditions, equally released as a result of cooling. But the ordering (in a foreign way, entropy) has not changed - it just seems to be in different units and volumes.
To answer
\u003e\u003e In fairness it is worth saying that first it was necessary to spend (energetically) on creating clearly separated vacuum and gas, i.e. the system initially had potential energy and orderliness: (a clear region with gas and with vacuum), and as a result, gas is everywhere, but cold and of a larger volume. And how is this orderly measured?
Everything is much simpler. Where there is gas, the pressure is above zero. Where there is a vacuum, there is pressure \u003d 0. The pressure difference is potential energy. The temperature difference is also potential energy. We extract them. And don't worry about the disorder - we're doing some work using cooled molecules - this work of entropy will induce enough to calm our fans.
\u003e\u003e It seems to me that the amount of energy that was needed to create the initial conditions is equally released as a result of cooling.
Yes, but the nice thing is that we didn't spend this energy :) If, say, we just take atmospheric air containing a mass of sufficiently energetic molecules, divide it with a barrier membrane, use the temperature difference and release cold air back - it will be free (free does not mean "eternal"!) engine. And along the way, the cooling of the climate is a hit for the countries of Central Africa.To answer
Yes, I do not argue. Molecules can be divided according to some principle. But this does not mean that their ensemble (fast or slow) under equilibrium conditions (when we can talk about the temperature of the system) will not redistribute the velocities among the particles according to the distribution function. And again there will be fast and there will be slow. Otherwise, we need to talk about another model of the state of matter.
The funnel is interesting, no doubt. But we should talk, in my opinion, about the energy funnel - the heat one. A mechanical funnel is unlikely to "pull in" the particles, except perhaps the substance itself. Those. one should not forget that we are talking about some "representatives" of the ensemble, and not about its deterministic distribution, as, for example, at the interfaces. For an individual particle to have velocity is not a characteristic, since you must immediately answer - what is this speed measured in relation to?
Once again I want to express my delight at the beauty of the task. And why does she hesitate? I think my decision is fine, although not necessarily true.
To answer
But the question is formulated somewhat differently. The "molecular" engine is powered by temperature.
1. Where is the engine of the molecule?
2. Why should there be fast and slow molecules if the temperature is the same?
Due to collisions. Impact - speed dropped. Warming up - the speed has increased.
Well, the Demon has collected fast molecules. So the remaining slow ones will accelerate to the speed of the fast ones and the gradient will disappear!
2. Can a person orient the molecular "motors" to move in one direction?
Yes, by ionizing the gas and applying a field to it.
3. Is there any other possibility besides electromagnetic field "orient" molecular motors?
The movement of molecules when irradiated with infrared light is likely caused by the expansion of electron clouds. And molecules in the mass of gas begin to "push" by the electron clouds. These "jolts" are probably the reason for the movement of molecules.
If there are few molecules or there is only one molecule at all, then under infrared irradiation, its electron clouds begin to repel from the walls of the vessel.
Are there any other considerations?
To answer
There is a problem in physics that can be conventionally called the "reversibility-irreversibility" problem, and the thought experiment with Maxwell's demon is only one of the most striking illustrations of it. All physical laws, with one exception, are reversible in time, and the possibility of realizing Maxwell's demon does not contradict them! The exception is the second law of thermodynamics, which has many different formulations. The simplest of them is that heat cannot spontaneously pass from a body with a higher temperature to a body with a lower temperature. The possibility of the existence of the demon Maxwell contradicts exclusively this law. Thus, any attempts to prove the impossibility of Maxwell's demon, in which the second principle is not explicitly or implicitly used, are doomed to failure. It should be noted that all physical laws, including the second law, are a generalization of experimental data.
All these problems can be seriously discussed only by having a professional understanding of thermodynamics, statistical physics, quantum statistics, physical kinetics; future theoretical physicists study this mainly in their senior years for about six semesters. Non-professionals should not tackle this problem - no one is trying to independently calculate the orbits of asteroids or calculate the electronic structure of semiconductors, and this is much easier.
Some notes for professionals. 1) In a consistent way, entropy can be introduced only for an equilibrium system, while the second principle speaks in principle about nonequilibrium processes. 2) Statistical (through statistical weight) and thermodynamic (through heat and temperature) definitions of entropy do not always coincide. 3) From the quantum-mechanical (through the density matrix) definition of entropy it strictly follows that the entropy of a closed-loop system remains unchanged. In general, there are many questions here.
To answer
The author is wrong. History tells us that the truly worthwhile discoveries and inventions were made by “non-professionals”. Your so-called professionals are a bunch of boobies and sycophants. The Maxwell demon has been around for a long time. This device, invented in 1931, is called the Ranke-Hilsch tube. It allows you to separate a gas or liquid into hot and cold streams using a vortex. Moreover, much more heat is obtained than the energy expended to create a vortex.
To answer
\u003e\u003e heat cannot spontaneously transfer from a body with a higher temperature to a body with a lower temperature. The possibility of the existence of Maxwell's demon contradicts only this law .... Non-professionals should not tackle this problem - no one is trying to independently calculate the orbits of asteroids or calculate the electronic structure of semiconductors, and this is much easier.
Non-professionals should not undertake anything at all - if something requires a professional decision, it is paid for and affects something. But what's wrong with _ just chatting on the free forum_ about something unrelated to your professional competence? Hardly anyone here seriously thinks that he "solves" something (except, perhaps, the author of the article ;-) And the orbits of asteroids, I think, are also calculated by someone - only in another branch :)))
Regarding the second law - such a point: how correct is it in general to identify "the transition of heat from one body to another" with "the division of one body into components (well, or two bodies)"?To answer
I completely agree with you. By the way, it will be right - heat cannot spontaneously pass from a body with a low temperature to a body with a higher temperature. The exact formulation of the second law belongs to W. Thomson and M. Planck: "In nature, a process is impossible, the full effect of which would consist only in the cooling of the heat reservoir and in the equivalent lifting of the load." But: in nature, Maxwell's demon exists if there is a possibility of creating a diode of molecular dimensions, a molecular diode. Such a diode is capable of converting the thermal motion of electrons into an ordered one, that is, into electricity... There is also a patent for a gradient tunneling diode with operating frequencies up to the ultraviolet range, which, according to the authors, is capable of converting even thermal fluctuations of electrons into electric current. This is our demon.
Let's do a thought experiment (like Grandpa Maxwell). We will not divide one body into components, but take an isolated container, divided by an impenetrable partition into two reservoirs. In a colder tank we place a lattice of nanorectennas (a rectenna is an antenna with a rectifier) \u200b\u200btuned to resonance with the radiation of fast, hot molecules of this reservoir, we connect the lattice with a bridge circuit of demons and - go ahead! We accumulate the resulting constant electric current and send it to the load (resistance) in a hotter tank and drown it to a victorious one (or we raise some kind of load). The second law rests. Of course, you cannot make a perpetual motion machine of the second kind in this way, since it is impossible to cool the first reservoir to infinity, but a clear violation of the second law is visible, right?To answer
Of course, this is not exactly Maxwell's demon, although the principle "take from the poor and give it to the rich" (let's call it "the inverse principle of Robin Hood") is ideologically close to our demon :)
And then I did not quite understand something: these "nanorectile" - do they still allow molecules or electrons to pass through? If molecules - then what kind of electronic current are we talking about? And if electrons (or ions in general), then what's the point of filtering them by speed? a slow electron is also an electron and the electric current will give as much as a fast one. True, this already turns out to be something like an ordinary electrolyte battery, only instead of electrolyte - gas (why?). The meaning of the second (hot) reservoir is not clear to me at all.Further (we proceed from the fact that we still filter molecules and try to transfer heat and not an electric charge). "connecting the lattice [nanorecten] to the demon bridge" - so who is rectifying here? rectennas or demons? if they are rectenna, then why are demons needed - and vice versa. If the rectennas are straightened, then the demon must sit IN EACH of them, and no additional bridges are needed to straighten the flow from the entire lattice, therefore, consolidation of flows from individual rectennas is not needed - that is, we return to the membrane (in which there is simply a "barrier" and "funnel" are united by the word "rectenna"). If rectennas only filter molecules by velocity (in both directions), then this is no longer a “rectenna”, but simply barriers, and all the most difficult (“funnel”) is done centrally. That is, this is just a constructive difference, not a fundamental one.
Filtering molecules by velocity is not a very difficult task. For example, we take an ionized (say +) gas and a monomolecular membrane of the same name (for structural rigidity, it can be attached to an easily permeable neutral frame). Only those gas molecules whose kinetic energy will be sufficient to overcome the Coulomb reaction will be able to slip through this membrane. It is important - the breakthrough (or rebound) of the molecule will be absolutely elastic - how much the molecule slows down on its way to the membrane - the same way it will accelerate when it rebounds (from the same or the other side). The required kin.energy threshold can be adjusted by selecting the size of the membrane cell and the charge on it.
The most difficult thing that may be required of a demon is to let the molecules go only in one direction. I don’t know how to teach a demon to do this, but you can make a knight's move and save him from this work. In principle, it is already enough that we have on one side of the membrane only fast molecules from the original body are guaranteed. Some of them will fly back, but some will remain. Already good. How to use it?
"Maxwell's Demon" is a thought experiment invented by James Maxwell in 1867 to illustrate the seeming paradox of the Second Law of Thermodynamics. The main character of this experiment is a hypothetical intelligent microscopic creature, later named "Maxwell's demon".
Suppose that a vessel with gas is divided by an impermeable partition into right and left parts. There is a hole in the partition with a device, the so-called Maxwell's demon, which allows fast, hot gas molecules to fly only from the left side of the vessel to the right, and slow, cold molecules only from the right side of the vessel to the left.
Then, after some rather long period of time, all hot molecules will be on the right, and cold ones - on the left. Thus, it turns out that the demon of Maxwell, without additional energy supply, can heat one part of the vessel and cool another.
As a result, it turns out that the entropy of a system consisting of two halves is greater in the initial state than in the final state, and this contradicts the thermodynamic principle of non-decreasing entropy in closed systems, i.e. the second law of thermodynamics.
Indeed, it follows from the second law of thermodynamics that it is impossible to transfer heat from a body with a lower temperature to a body with a higher temperature without performing work.
The paradox is resolved if we consider a closed system that includes the demon Maxwell and the vessel. For the functioning of the demon Maxwell itself, it is necessary to transfer energy to him from an external source. Due to this energy, the separation of hot and cold molecules would be produced.
Such a memorable bas-relief appeared in honor of James Maxwell and his elusive demon on the wall of one of the US universities.
And if such a demon could exist in reality, then it would be possible to create a heat engine that would work without consuming energy.
With the development of information theory, it was found that the measurement process may not lead to an increase in entropy, provided that it is thermodynamically reversible.
However, in this case, the demon must memorize the speed measurements (deleting them from the demon's memory makes the process irreversible).
Since memory is finite, at a certain moment the demon is forced to erase the old results, which ultimately leads to an increase in the entropy of the entire system as a whole.
In 2010, physicists from the University of Tokyo managed to implement the thought experiment in reality. Scientists noted that they were inspired to create this experiment by the famous demon Maxwell. For the first time, Japanese physicists have succeeded in converting information into energy.
They have created a working nanoscale system that converts information into energy with an efficiency of about 28 percent (for comparison, the efficiency of the most modern internal combustion engines is slightly over 40 percent). Scientists do not exclude that in the future the principle they have developed will make it possible to create systems in which the dimensions of both the controlled object and the “demon” will not exceed hundreds of nanometers.
And in 2015, physicists from Finland, Russia and the United States created an autonomous artificial Maxwell demon, which was implemented in the form of a single-electron transistor with superconducting aluminum leads. Maxwell's demon controls the movement of electrons through the transistor.
The installation will help to study microscopic phenomena in thermodynamics and can find application in qubits for quantum computers.
How can you get energy from information? Until recently, only a demon was capable of this - a fantastic creature invented in 1867 by the great physicist James Maxwell to illustrate the paradox of the second law of thermodynamics. Now Japanese scientists are close to developing such an experimental model. In the future, they hope to create nanomachines that feed on information. The work of scientists is published Nature physics.
the demon "is able to follow the trajectory of each molecule and perform actions completely inaccessible to us."
In other words, the demon is capable of distinguishing and sorting individual molecules. How to extract energy from this ability? Imagine a vessel divided into two parts by a septum (in the figure). The vessel is filled with molecules of two types: “hot” (dark in the figure) particles move faster, and “cold” (light ones in the figure) move more slowly. In a state of equilibrium (upper part of the figure), the molecules are mixed, as required by the second law of thermodynamics: any system in an isolated state tends to the maximum entropy, that is, the maximum disorder.
Illustration of the work of "Maxwell's demon" // nanometr.ru
However, there is a hole in the partition that the same demon can open and close. It possesses the ability described above, that is, it distinguishes “hot” particles from “cold” ones. Therefore, he can “work” so that all the “hot” particles are to the right of the partition, and the “cold” ones to the left. To do this, he will allow Brownian (randomly) moving "hot" particles from the left side to overcome the partition, but not from the right (and do the opposite with the "cold" particles). As a result, an ordered state will arise from a disordered state, which contradicts the second law of thermodynamics. Maxwell's demon, using only information about the quality of the particles, will create energy due to the temperature difference in the two parts of the vessel, which can then be used.
In this way,
initially it seemed that the demon receives energy "from nothing" and creates a perpetual motion machine.
However, the paradox was resolved, because the demon himself must spend a certain energy in order to obtain information about chaotically moving particles. Therefore, there is no violation of the laws of thermodynamics: energy arises from the work done by the demon.
One way or another, nobody succeeded in creating a physical working model of the demon and showing how it works.
Japanese scientists, however, reported in the latest issue of Nature Physics the success of such an experiment. They created a miniature "demon" using a polymer ball and an electric field.
In the experiment, we used two balls made of polystyrene, ordinary plastic, with a diameter of 0.3 μm (300 nm). One of them was fixed on a glass surface, and the second was located so that it could rotate freely around the first. The entire system was immersed in liquid. As a result of the chaotic motion of liquid molecules, the system rotated with equal frequency both clockwise and counterclockwise (due to its small size, the ball successfully “felt” fluid fluctuations).
Then an additional electric field was applied to the liquid, which imparted a rotational moment to the system of balls. The rotation pattern of the system has been preserved. Although in some cases the energy of the chaotic motion of liquid particles was sufficient to turn the ball against the direction of the electric field, nevertheless, more often the system followed the rotational moment imparted to it by the field.
the “demon” itself appeared on the “stage” in the form of a camera and a computer controlling the electric field.
The camera controlled the rotation of the system; as soon as the system was able to independently resist the applied electric field, the "demon" in the computer changed its mode, slightly "pushing" the system in the desired direction. Then she again followed him herself, using only the forces of Brownian motion.
Thus, the rotating system produced mechanical energy... Calculations have shown that the energy produced is slightly greater than the energy of the electric field applied to the system. The "demon" only needed information about the direction of rotation of the system in order to create it. It turned out that at room temperature, one bit of information is capable of creating a very small energy of 3x10 -21 joules.
“We have shown the ratio of information and energy obtained when the“ demon ”works, and confirmed the fundamental principle of its work,” said one of the authors of the work, Shoichi Toyabe, quoted by NewScientist.
He stressed that the energy produced by the system is negligible, but in the future it can be used to power nanodevices.
- a thought experiment encroaching on the second law of thermodynamics was put into reality by physicists from Chuo University and Tokyo (University of Tokyo).
The Japanese created two bonded polystyrene beads with a diameter of 0.3 micrometers each. One was on the surface of the glass, the second could rotate around the first. In this case, the installation was filled with liquid. Its molecules chaotically pushed the balls (Brownian motion), naturally, with equal probability both clockwise and counterclockwise.
Systems with feedback, say the Japanese physicists, may represent a new type of machine that converts information into energy. In theory, in the future, such devices could be powered by the Brownian motion of the micromachine.
The figure shows a schematic diagram of the experiment. The position of the spinning rotor is replaced here by a ball jumping randomly up the steps. When the ball jumps up, Maxwell's clever demon sets up a barrier that prevents the ball from rolling back. At the same time, the "demon" itself does not push the ball (illustration by Mabuchi Design Office / Yuki Akimoto).
Next, the authors added a weak electric field that generated the torque. It was analogous to a ladder, along which the ball could "climb", increasing the potential energy. Sometimes the molecules pushed the rotor against the action of the field (ascending), sometimes towards the field (jumping down the stairs). But in general, the rotor rotated where the external field pushed it.
But physicists have added a "demon" - a high-speed camera that observes the ball, and a computer that controls the field. Each time the rotor in Brownian motion took a step against the field, the computer moved the latter so that the ball could turn, but when the rotor tried to rotate back, the field blocked it.
So an analogue of the door opened and closed by Maxwell's demon was created: the rotor increased its energy due to the thermal motion of molecules.
However, the installation does not violate the laws of nature, since energy is needed for the “demon” (camera, voltage correction system) to work. But the Japanese emphasize: this experience for the first time in practice proved the reality of a heat pump - Maxwell's demon, theoretically substantiated by Leo Szilard in 1929. Such a machine extracts energy from an isothermal environment and transforms it into work.
General principle heat pump - demon Maxwell ("Szilard's engine"). A macroscopic system (computer) controls events in a microscopic system (in reality - a rotor and a field, and conventionally - a room with molecules and a partition) by obtaining information about it. The energy in a microscopic system grows (and can do useful work), but not completely free, since the "demon" consumes energy to obtain information and control actions (illustration Shoichi Toyabe, Eiro Muneyuki, Masaki Sano / Nature Physics).