Maxwell's demon is a thought experiment A thought experiment is a proposal for an experiment that would test or illuminate a hypothesis, theory, or principle formulated by the Scottish Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the southwest. In addition to the mainland, Scotland physicist A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole (cosmology). One of the world's best known physicists is Albert James Clerk Maxwell James Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most important achievement was classical electromagnetic theory, synthesizing all previously unrelated observations, experiments and equations of electricity, magnetism and even optics into a consistent theory. His set of equations—Maxwell's equations—demonstrated intended to "show that the 2nd Law The second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium; and that the entropy change dS of a system undergoing any infinitesimal reversible process is given by δq / of Thermodynamics In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure has only a statistical certainty," and is used as a tool to present the possibility of its violation. The concept first appeared in a letter Maxwell wrote to Peter Guthrie Tait on 11 December 1867, though it appeared again in a letter to John William Strutt in 1870 before it was presented to the public in Maxwell's 1871 book on thermodynamics titled Theory of Heat.[1] The experiment involves a theoretical container divided into two parts by a door that can be opened and closed by a single entity. The entity was later named "Maxwell's Demon" by Lord Kelvin William Thomson, 1st Baron Kelvin , OM, GCVO, PC, PRS, PRSE, (26 June 1824 – 17 December 1907) was a Belfast-born mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second Laws of Thermodynamics, and did much to unify the emerging, who elaborated on Maxwell's experiment.[2]
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Original thought experiment
The second law of thermodynamics ensures (through statistical improbability) that two bodies of different temperature Historically, two equivalent concepts of temperature have developed, the thermodynamic description and a microscopic explanation based on statistical physics. Since thermodynamics deals entirely with macroscopic measurements, the thermodynamic definition of temperature, first stated by Lord Kelvin, is stated entirely in empirical, measurable, when brought into contact with each other and isolated from the rest of the Universe, will evolve to a thermodynamic equilibrium in which both bodies have approximately the same temperature. The second law is also expressed as the assertion that in an isolated system In the natural sciences an isolated system, as contrasted with an open system, is a physical system that does not interact with its surroundings. It obeys a number of conservation laws: its total energy and mass stay constant. They cannot enter or exit, but can only move around inside. An example is in the study of spacetime, where it is assumed, entropy Entropy is a macroscopic property of a system that is a measure of the microscopic disorder within the system. It is an important part of the second law of thermodynamics. Thermodynamic systems are made up of microscopic objects, e.g. atoms or molecules, which "carry" energy. According to the second law of thermodynamics, the never decreases.
Maxwell conceived a thought experiment as a way of furthering understanding of the second law. He described the experiment as follows:[3]
Schematic figure of Maxwell's demon... if we conceive of a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are as essentially finite as our own, would be able to do what is impossible to us. For we have seen that molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the slower molecules to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics....
In other words, Maxwell imagines one container divided into two parts, A and B. Both parts are filled with the same gas Gas is one of four classical states of matter. Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms at equal temperatures and placed next to each other. Observing the molecules A molecule is defined as an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense. In organic chemistry and biochemistry, the term molecule is used less strictly and also is applied to charged organic molecules on both sides, an imaginary demon In religion and mythology, occultism and folklore, a demon is a supernatural being that is generally described as a malevolent spirit; however, the original neutral connotation of the Greek word daimon does not carry the negative one that was later projected onto it, as Christianity spread guards a trapdoor between the two parts. When a faster-than-average molecule from A flies towards the trapdoor, the demon opens it, and the molecule will fly from A to B. The average speed In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero of the molecules in B will have increased while in A they will have slowed down on average. Since average molecular speed corresponds to temperature, the temperature decreases in A and increases in B, contrary to the second law of thermodynamics.
Origin of the term
When Maxwell introduced the concept, in his letters to colleagues, and in his book, Theory of Heat, he described it as a "finite being." William Thompson (Lord Kelvin) William Thomson, 1st Baron Kelvin , OM, GCVO, PC, PRS, PRSE, (26 June 1824 – 17 December 1907) was a Belfast-born mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second Laws of Thermodynamics, and did much to unify the emerging was the first to use the word "demon" for Maxwell's concept, in the journal Nature, in 1874, and implied that he intended the mediating, rather than malevolent, meaning of the word.[4]
Criticism and development
Several physicists have presented calculations that show that the second law of thermodynamics The second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium; and that the entropy change dS of a system undergoing any infinitesimal reversible process is given by δq / will not actually be violated, if a more complete analysis is made of the whole system including the demon. The essence of the physical argument is to show by calculation that any demon must "generate" more entropy segregating the molecules than it could ever eliminate by the method described. That is, it would take more effort to gauge the speed of the molecules and allow them to selectively pass through the opening between A and B than the amount of energy saved by the difference of temperature caused by this.
One of the most famous responses to this question was suggested in 1929 by Leó Szilárd Leó Szilárd was a Hungarian physicist who conceived the nuclear chain reaction and worked on the Manhattan Project. He was born in Budapest in the Austro-Hungarian Empire, and died in La Jolla, California and later by Léon Brillouin. Szilárd pointed out that a real-life Maxwell's demon would need to have some means of measuring molecular speed, and that the act of acquiring information would require an expenditure of energy. The second law The second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium; and that the entropy change dS of a system undergoing any infinitesimal reversible process is given by δq / states that the total entropy of an isolated system must increase. Since the demon and the gas are interacting, we must consider the total entropy of the gas and the demon combined. The expenditure of energy by the demon will cause an increase in the entropy of the demon, which will be larger than the lowering of the entropy of the gas. For example, if the demon is checking molecular positions using a flashlight, the flashlight battery is a low-entropy device, a chemical reaction waiting to happen. As its energy is used up emitting photons (whose entropy must now be counted as well), the battery's chemical reaction will proceed and its entropy will increase, more than offsetting the decrease in the entropy of the gas.
In 1960, Rolf Landauer Rolf William Landauer was an IBM physicist who in 1961 argued that when information is lost in an irreversible circuit, the information becomes entropy and an associated amount of energy is dissipated as heat. This principle is relevant to reversible computing, quantum information and quantum computing raised an exception to this argument. He realized that some measuring processes need not increase thermodynamic entropy as long as they were thermodynamically reversible. He suggested these "reversible" measurements could be used to sort the molecules, violating the Second Law. However, due to the connection between thermodynamic entropy and information entropy In information theory, entropy is a measure of the uncertainty associated with a random variable. The term by itself in this context usually refers to the Shannon entropy, which quantifies, in the sense of an expected value, the information contained in a message, usually in units such as bits. Equivalently, the Shannon entropy is a measure of the, this also meant that the recorded measurement must not be erased. In other words, to determine what side of the gate a molecule must be on, the demon must acquire information about the state of the molecule and either discard it or store it. Discarding it leads to immediate increase in entropy but the demon cannot store it indefinitely: In 1982, Bennett showed that, however well prepared, eventually the demon will run out of information storage space and must begin to erase the information it has previously gathered. Erasing information is a thermodynamically irreversible process that increases the entropy of a system.[5]
However, John Earman and John Norton have argued that Szilárd and Landauer's explanations of Maxwell's Demon begin by assuming that the second law of thermodynamics The second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium; and that the entropy change dS of a system undergoing any infinitesimal reversible process is given by δq / cannot be violated, thus rendering their proofs that Maxwell's Demon cannot violate the Second Law circular.
Applications
Real-life versions of Maxwellian demons occur, but all such "real demons" have their entropy-lowering effects duly balanced by increase of entropy elsewhere.
Single-atom traps used by particle physicists allow an experimenter to control the state of individual quanta in a way similar to Maxwell's demon.
Molecular-sized mechanisms are no longer found only in biology; they are also the subject of the emerging field of nanotechnology Nanotechnology, shortened to "nanotech", is the study of the controlling of matter on an atomic and molecular scale. Generally nanotechnology deals with structures sized between 1 to 100 nanometer in at least one dimension, and involves developing materials or devices within that size.
A large-scale, commercially-available pneumatic device, called a Ranque-Hilsch vortex tube The vortex tube, also known as the Ranque-Hilsch vortex tube, is a mechanical device that separates a compressed gas into hot and cold streams. It has no moving parts separates hot and cold air. It sorts molecules by exploiting the conservation of angular momentum: hotter molecules are spun to the outside of the tube while cooler molecules spin in a tighter whirl within the tube. Gas from the two different temperature whirls may be vented on opposite ends of the tube. Although this creates a temperature difference, the energy to do so is supplied by the pressure driving the gas through the tube.
If hypothetical mirror matter In physics, mirror matter, also called shadow matter or Alice matter, is a hypothetical counterpart to ordinary matter. Modern physics deals with three basic types of spatial symmetry: reflection, rotation and translation. The known elementary particles respect rotation and translation symmetry but do not respect mirror reflection symmetry . Of exists, Zurab Silagadze proposes that demons can be envisaged, "which can act like perpetuum mobiles of the second kind: extract heat energy from only one reservoir, use it to do work and be isolated from the rest of ordinary world. Yet the Second Law is not violated because the demons pay their entropy cost in the hidden (mirror) sector of the world by emitting mirror photons."
In 1962 lectures, to illustrate thermodynamics, physicist Richard Feynman Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics (he proposed the parton model). For his contributions to the development of quantum analyzed a putative Maxwell's demon device, a tiny paddlewheel attached to a ratchet A ratchet is a device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. The term is also commonly used to refer to a socket wrench, which employs an internal ratchet mechanism, showing why it cannot extract energy from molecular motion of a fluid at equilibrium.[6] This brownian ratchet The Brownian ratchet, or Feynman-Smoluchowski ratchet is a thought experiment about an apparent perpetual motion machine first analysed in 1912 by Polish physicist Marian Smoluchowski and popularised by American Nobel laureate physicist Richard Feynman in a physics lecture at the California Institute of Technology on May 11, 1962, and his text The is a popular teaching tool.
Experimental work
In the 1 February 2007 issue of Nature Nature is a prominent British scientific journal, first published on 4 November 1869. It is the world's most highly cited interdisciplinary science journal. Most scientific journals are now highly specialized, and Nature is among the few journals that still publish original research articles across a wide range of scientific fields. There are many, David Leigh, a professor at the University of Edinburgh The University of Edinburgh, founded in 1582, is an internationally renowned centre for teaching and research in Edinburgh, the capital city of Scotland. It was the fourth university to be established in Scotland, making it one of the ancient universities of the United Kingdom, announced the creation of a nano-device based on this thought experiment. This device is able to drive a chemical system out of equilibrium In a chemical process, chemical equilibrium is the state in which the chemical activities or concentrations of the reactants and products have no net change over time. Usually, this would be the state that results when the forward chemical process proceeds at the same rate as their reverse reaction. The reaction rates of the forward and reverse, but it must be powered by an external source (light Light is electromagnetic radiation of a wavelength that is visible to the human eye . In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not in this case) and therefore does not violate thermodynamics.
Previously, other researchers created a ring-shaped molecule which could be placed on an axle connecting two sites (called A and B). Particles from either site would bump into the ring and move it from end to end. If a large collection of these devices were placed in a system, half of the devices had the ring at site A and half at B at any given moment in time.
Leigh made a minor change to the axle so that if a light is shone on the device, the center of the axle will thicken, thus restricting the motion of the ring. It only keeps the ring from moving, however, if it is at site A. Over time, therefore, the rings will be bumped from site B to site A and get stuck there, creating an imbalance in the system. In his experiments, Leigh was able to take a pot of "billions of these devices" from 50:50 equilibrium to a 70:30 imbalance within a few minutes.[7]
Adams and the demon as historical metaphor
Historian Henry Brooks Adams Henry Brooks Adams was an American journalist, historian, academic and novelist. He is best-known for his autobiographical book, The Education of Henry Adams. He was a member of the Adams political family in his manuscript The Rule of Phase Applied to History attempted to use Maxwell's demon as a historical metaphor A metaphor is an analogy between two objects or ideas; the analogy is conveyed by the use of a metaphorical word in place of some other word. For example: "Her eyes were glistening jewels", though he misunderstood and misapplied the original principle.[8] Adams interpreted history History is the study of the human past. Scholars who write about history are called historians. It is a field of research which uses a narrative to examine and analyse the sequence of events, and it sometimes attempts to investigate objectively the patterns of cause and effect that determine events. Historians debate the nature of history and its as a process moving towards "equilibrium", but he saw militaristic Militarism has been a significant principle in the imperialist or expansionist ideologies of several nations throughout history. Some prominent examples are the Greek city state of Sparta, the Roman Empire, the Aztec nation, the Kingdom of Prussia, the British Empire, the Empire of Japan, the Russian Soviet Federative Socialist Republic , the nations (he felt Germany A region named Germania, inhabited by several Germanic peoples, has been known and documented before AD 100. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire, which lasted until 1806. During the 16th century, northern Germany became the centre of the Protestant Reformation. As a modern nation-state, pre-eminent in this class) as tending to reverse this process, a Maxwell's Demon of history. Adams made many attempts to respond to the criticism of his formulation from his scientific colleagues, but the work remained incomplete at Adams' death in 1918. It was only published posthumously.[9]
Mon, 23 Aug 2010 15:03:08 GMT+00:00
Institute for Ethics and Emerging Technologies Think of Maxwell's Demon , Schroedinger's Cat, or Einstein's thought experiment of chasing a light beam, which allegedly led him to Special Relativity. ...
Christopher
Sat, 08 May 2010 13:52:00 GM
"It is these same technologies that are now being set off to pluck energy out of nothingness, or very close to it -- to do almost exactly what . Maxwell's demon. was supposed to do, but honestly." See my earlier comments on . Maxwell's demon. ...
