"Heat can evidently be a cause of motion only by virtue of the changes of volume or of form which it produces in bodies. These changes are not caused by uniform temperature but rather by alternations of heat and cold." (Nicolas L S Carnot, "Reflections on the Motive Power of Heat and on Machines Fitted to Develop Power", 1824)
"In order to consider in the most general way the principle of the production of motion by heat, it must be considered independently of any mechanism or any particular agent. It is necessary to establish principles applicable not only to steam engines but to all imaginable heat-engines, whatever the working substance and whatever the method by which it is operated." (Nicolas L S Carnot, "Reflections on the Motive Power of Heat and on Machines Fitted to Develop Power", 1824)
"Machines which do not receive their motion from heat [...] can
be studied even to their smallest details by the mechanical theory. [...] A
similar theory is evidently needed for heat-engines. We shall have it only when
the laws of Physics shall be extended enough, generalized enough, to make known
beforehand all of the effects of heat acting in a determined manner on any
body."
"The production of heat alone is not sufficient to give birth to the impelling powerː it is necessary that there should also be cold; without it the heat would be useless. And in fact, if we should find about us only bodies as hot as our furnaces. [...] What should we do with it if once produced? We should not presume that we might discharge it into the atmosphere [...] the atmosphere would not receive it. It does receive it under the actual condition of things only because.. it is at a lower temperature, otherwise it [...] would be already saturated."(Nicolas L S Carnot, "Reflections on the Motive Power of Heat and on Machines Fitted to Develop Power", 1824)
"It is impossible by means of inanimate material agency, to
derive mechanical effect from any portion of matter by cooling it below the
temperature of the coldest of the surrounding objects. [Footnote: ] If this
axiom be denied for all temperatures, it would have to be admitted that a
self-acting machine might be set to work and produce mechanical effect by
cooling the sea or earth, with no limit but the total loss of heat from the
earth and sea, or in reality, from the whole material world." (William Thomson, "On
the Dynamical Theory of Heat with Numerical Results Deduced from Mr Joule's
Equivalent of a Thermal Unit and M. Regnault's Observations on Steam",
Transactions of the Royal Society of Edinburgh, 1851)
"It is possible to express the laws of thermodynamics in the
form of independent principles, deduced by induction from the facts of
observation and experiment, without reference to any hypothesis as to the
occult molecular operations with which the sensible phenomena may be conceived
to be connected; and that course will be followed in the body of the present
treatise. But, in giving a brief historical sketch of the progress of
thermodynamics, the progress of the hypothesis of thermic molecular motions
cannot be wholly separated from that of the purely inductive theory." (William J
M Rankine, "A Manual of the Steam Engine and Other Prime Movers", 1859)
"The second fundamental theorem [the second law of thermodynamics], in the form which I have given to it, asserts that all transformations occurring in nature may take place in a certain direction, which I have assumed as positive, by themselves, that is, without compensation […] the entire condition of the universe must always continue to change in that first direction, and the universe must consequently approach incessantly a limiting condition. […] For every body two magnitudes have thereby presented themselves - the transformation value of its thermal content [the amount of inputted energy that is converted to 'work'], and its disgregation [separation or disintegration]; the sum of which constitutes its entropy." (Rudolf Clausius, "The Mechanical Theory of Heat", 1867)
"Heat may be generated and destroyed by certain processes, and this shows that heat is not a substance." (James C Maxwell, "Theory of Heat", 1871)
"The whole science of heat is founded Thermometry and
Calorimetry, and when these operations are understood we may proceed to the
third step, which is the investigation of those relations between the thermal
and the mechanical properties of substances which form the subject of
Thermodynamics. The whole of this part of the subject depends on the
consideration of the Intrinsic Energy of a system of bodies, as depending on
the temperature and physical state, as well as the form, motion, and relative
position of these bodies. Of this energy, however, only a part is available for
the purpose of producing mechanical work, and though the energy itself is
indestructible, the available part is liable to diminution by the action of
certain natural processes, such as conduction and radiation of heat, friction,
and viscosity. These processes, by which energy is rendered unavailable as a
source of work, are classed together under the name of the Dissipation of
Energy."
"Since a given system can never of its own accord go over into another equally probable state but into a more probable one, it is likewise impossible to construct a system of bodies that after traversing various states returns periodically to its original state, that is a perpetual motion machine." (Ludwig E Boltzmann, "The Second Law of Thermodynamics", [Address to a Formal meeting of the Imperial Academy of Science], 1886)
"Though the ultimate state of the universe may be its vital and psychical extinction, there is nothing in physics to interfere with the hypothesis that the penultimate state might be the millennium - in other words a state in which a minimum of difference of energy - level might have its exchanges so skillfully canalises that a maximum of happy and virtuous consciousness would be the only result." (William James, [Letter to Henry Adams] 1910)" (William James, [Letter to Henry Adams] 1910)
"Organic evolution has its physical analogue in the universal
law that the world tends, in all its parts and particles, to pass from certain
less probable to certain more probable configurations or states. This is the
second law of thermodynamics." (D'Arcy Wentworth Thompson, "On Growth and Form", 1917)
"The second law of thermodynamics appears solely as a law of probability, entropy as a measure of the probability, and the increase of entropy is equivalent to a statement that more probable events follow less probable ones." (Max Planck, "A Survey of Physics", 1923)
"It was not easy for a person brought up in the ways of classical thermodynamics to come around to the idea that gain of entropy eventually is nothing more nor less than loss of information." (Gilbert N Lewis, [Letter to Irving Langmuir] 1930)
"True equilibria can occur only in closed systems and that, in open systems, disequilibria called ‘steady states’, or ‘flow equilibria’ are the predominant and characteristic feature. According to the second law of thermodynamics a closed system must eventually attain a time-independent equilibrium state, with maximum entropy and minimum free energy. An open system may, under certain conditions, attain a time-independent state where the system remains constant as a whole and in its phases, though there is a continuous flow of component materials. This is called a steady state. Steady states are irreversible as a whole. […] A closed system in equilibrium does not need energy for its preservation, nor can energy be obtained from it. In order to perform work, a system must be in disequilibrium, tending toward equilibrium and maintaining a steady state, Therefore the character of an open system is the necessary condition for the continuous working capacity of the organism." (Ludwig on Bertalanffy, "Theoretische Biologie: Band 1: Allgemeine Theorie, Physikochemie, Aufbau und Entwicklung des Organismus", 1932)
"When a transfer of matter to or from a system is also possible, the system may be called an open system." (Frank H MacDougall, "Thermodynamics and chemistry", ?1939)
"A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended is its area of applicability. Therefore the deep impression which classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that, within the framework of the applicability of its basic concepts, it will never be overthrown (for the special attention of those who are skeptics on principle)." (Albert Einstein, "Autobiographical Notes", 1949)
"In classical physics, most of the fundamental laws of nature
were concerned either with the stability of certain configurations of bodies,
e.g. the solar system, or else with the conservation of certain properties of
matter, e.g. mass, energy, angular momentum or spin. The outstanding exception
was the famous Second Law of Thermodynamics, discovered by Clausius in 1850.
This law, as usually stated, refers to an abstract concept called entropy,
which for any enclosed or thermally isolated system tends to increase
continually with lapse of time. In practice, the most familiar example of this
law occurs when two bodies are in contact: in general, heat tends to flow from
the hotter body to the cooler. Thus, while the First Law of Thermodynamics,
viz. the conservation of energy, is concerned only with time as mere duration,
the Second Law involves the idea of trend." (Gerald J Whitrow, "The Structure of
the Universe: An Introduction to Cosmology", 1949)
"Reversible processes are not, in fact, processes at all, they are sequences of states of equilibrium. The processes which we encounter in real life are always irreversible processes." (Arnold Sommerfeld, "Thermodynamics and Statistical Mechanics", Lectures on Theoretical - Physics Vol. V, 1956)
"My analysis of living systems uses concepts of thermodynamics, information theory, cybernetics, and systems engineering, as well as the classical concepts appropriate to each level. The purpose is to produce a description of living structure and process in terms of input and output, flows through systems, steady states, and feedbacks, which will clarify and unify the facts of life." (James G Miller, "Living Systems: Basic Concepts", 1969)
"In an isolated system, which cannot exchange energy and matter with the surroundings, this tendency is expressed in terms of a function of the macroscopic state of the system: the entropy." (Ilya Prigogine, "Thermodynamics of Evolution", 1972)
"[The] system may evolve through a whole succession of transitions leading to a hierarchy of more and more complex and organized states. Such transitions can arise in nonlinear systems that are maintained far from equilibrium: that is, beyond a certain critical threshold the steady-state regime become unstable and the system evolves into a new configuration." (Ilya Prigogine, Gregoire Micolis & Agnes Babloyantz, "Thermodynamics of Evolution", Physics Today 25 (11), 1972)
"The evolution of a physicochemical system leads to an equilibrium state of maximum disorder." (Ilya Prigogine, "Thermodynamics of Evolution", 1972)
"The functional order maintained within living systems seems to defy the Second Law; nonequilibrium thermodynamics describes how such systems come to terms with entropy." (Ilya Prigogine, "Thermodynamics of Evolution", 1972)
"When matter is becoming disturbed by non-equilibrium conditions it organizes itself, it wakes up. It happens that our world is a non-equilibrium system." (Ilya Prigogine, "Thermodynamics of Evolution", 1972)
"There is nothing supernatural about the process of self-organization to states of higher entropy; it is a general property of systems, regardless of their materials and origin. It does not violate the Second Law of thermodynamics since the decrease in entropy within an open system is always offset by the increase of entropy in its surroundings." (Ervin László, "Introduction to Systems Philosophy", 1972)
"Concepts form the basis for any science. These are ideas, usually somewhat vague (especially when first encountered), which often defy really adequate definition. The meaning of a new concept can seldom be grasped from reading a one-paragraph discussion. There must be time to become accustomed to the concept, to investigate it with prior knowledge, and to associate it with personal experience. Inability to work with details of a new subject can often be traced to inadequate understanding of its basic concepts." (William C Reynolds & Harry C Perkins, "Engineering Thermodynamics", 1977)
"Just like a computer, we must remember things in the order in which entropy increases. This makes the second law of thermodynamics almost trivial. Disorder increases with time because we measure time in the direction in which disorder increases." (Stephen Hawking, "A Brief History of Time", 1988)
"Life is nature's solution to the problem of preserving
information despite the second law of thermodynamics." (Howard L Resnikoff, "The
Illusion of Reality", 1989)
"Everywhere […] in the Universe, we discern that closed
physical systems evolve in the same sense from ordered states towards a state
of complete disorder called thermal equilibrium. This cannot be a consequence
of known laws of change, since […] these laws are time symmetric- they permit […]
time-reverse. […] The initial conditions play a decisive role in endowing the
world with its sense of temporal direction. […] some prescription for initial
conditions is crucial if we are to understand […]" (John D Barrow, "Theories of
Everything: The Quest for Ultimate Explanation", 1991)
"Three laws governing black hole changes were thus found, but it was soon noticed that something unusual was going on. If one merely replaced the words 'surface area' by 'entropy' and 'gravitational field' by 'temperature', then the laws of black hole changes became merely statements of the laws of thermodynamics. The rule that the horizon surface areas can never decrease in physical processes becomes the second law of thermodynamics that the entropy can never decrease; the constancy of the gravitational field around the horizon is the so-called zeroth law of thermodynamics that the temperature must be the same everywhere in a state of thermal equilibrium. The rule linking allowed changes in the defining quantities of the black hole just becomes the first law of thermodynamics, which is more commonly known as the conservation of energy." (John D Barrow, "Theories of Everything: The Quest for Ultimate Explanation", 1991)
"The second law of thermodynamics, which requires average entropy (or disorder) to increase, does not in any way forbid local order from arising through various mechanisms of self-organization, which can turn accidents into frozen ones producing extensive regularities. Again, such mechanisms are not restricted to complex adaptive systems." (Murray Gell-Mann, "What is Complexity?", Complexity Vol 1 (1), 1995)
"No one has yet succeeded in deriving the second law from any
other law of nature. It stands on its own feet. It is the only law in our
everyday world that gives a direction to time, which tells us that the universe
is moving toward equilibrium and which gives us a criteria for that state,
namely, the point of maximum entropy, of maximum probability. The second law
involves no new forces. On the contrary, it says nothing about forces
whatsoever." (Brian L Silver, "The Ascent of Science", 1998)
"Emergent self-organization in multi-agent systems appears to contradict the second law of thermodynamics. This paradox has been explained in terms of a coupling between the macro level that hosts self-organization (and an apparent reduction in entropy), and the micro level (where random processes greatly increase entropy). Metaphorically, the micro level serves as an entropy 'sink', permitting overall system entropy to increase while sequestering this increase from the interactions where self-organization is desired." (H Van Dyke Parunak & Sven Brueckner, "Entropy and Self-Organization in Multi-Agent Systems", Proceedings of the International Conference on Autonomous Agents, 2001)
"The second law of thermodynamics states that in an isolated system, entropy can only increase, not decrease. Such systems evolve to their state of maximum entropy, or thermodynamic equilibrium. Therefore, physical self-organizing systems cannot be isolated: they require a constant input of matter or energy with low entropy, getting rid of the internally generated entropy through the output of heat ('dissipation'). This allows them to produce ‘dissipative structures’ which maintain far from thermodynamic equilibrium. Life is a clear example of order far from thermodynamic equilibrium." (Carlos Gershenson, "Design and Control of Self-organizing Systems", 2007)
"Thermodynamics is about those properties of systems that are true independent of their mechanism. This is why there is a fundamental asymmetry in the relationship between mechanistic descriptions of systems and thermodynamic descriptions of systems. From the mechanistic information we can deduce all the thermodynamic properties of that system. However, given only thermodynamic information we can deduce nothing about mechanism. This is in spite of the fact that thermodynamics makes it possible for us to reject classes of models such as perpetual motion machines." (Carlos Gershenson, “Design and Control of Self-organizing Systems”, 2007)
"Second Law of thermodynamics is not an equality, but an inequality, asserting merely that a certain quantity referred to as the entropy of an isolated system - which is a measure of the system’s disorder, or ‘randomness’ - is greater (or at least not smaller) at later times than it was at earlier times." (Roger Penrose, "Cycles of Time: An Extraordinary New View of the Universe", 2010)
"The laws of thermodynamics tell us something quite different. Economic activity is merely borrowing low-entropy energy inputs from the environment and transforming them into temporary products and services of value. In the transformation process, often more energy is expended and lost to the environment than is embedded in the particular good or service being produced." (Jeremy Rifkin, "The Third Industrial Revolution", 2011)
"The reactions that break down large molecules into small ones do not require an input of energy, but the reactions that build up large molecules require and input of energy. This is consistent with the laws of thermodynamics, which say that large, orderly molecules tend to break down into small, disorderly molecules." (Stanley A Rice, "Life of Earth: Portrait of a Beautiful, Middle-aged Stressed-out World", 2011)
"The Second Law of Thermodynamics states that in an isolated system (one that is not taking in energy), entropy never decreases. (The First Law is that energy is conserved; the Third, that a temperature of absolute zero is unreachable.) Closed systems inexorably become less structured, less organized, less able to accomplish interesting and useful outcomes, until they slide into an equilibrium of gray, tepid, homogeneous monotony and stay there." (Steven Pinker, "The Second Law of Thermodynamics", 2017)
"With thermodynamics, one can calculate almost everything crudely; with kinetic theory, one can calculate fewer things, but more accurately; and with statistical mechanics, one can calculate almost nothing exactly." (Eugene Wigner)
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