Quotes from thermodynamics

“We are to admit no more causes of natural things, than such as are both true and sufficient to explain their appearances.”

Original text“Causas rerum naturalium non plures admitti debere, quam quæ & veræ sint & earum phænomenis explicandis sufficiant.”

Philosophiæ Naturalis Principia Mathematica (1726), Liber III, Regula I, p. 387. 3rd ed., London, Innys, 1726. English translation: A. Motte (trans.), The Mathematical Principles of Natural Philosophy, London, 1729. View the source

“…Nature is pleas'd with simplicity, and affects not the pomp of superfluous causes.”

Original text“Natura enim simplex est & rerum causis superfluis non luxuriat.”

Philosophiæ Naturalis Principia Mathematica (1726), Liber III, Regula I, p. 387. 3rd ed., London, Innys, 1726. English translation: A. Motte (trans.), The Mathematical Principles of Natural Philosophy, London, 1729. View the source

“As in Mathematicks, so in Natural Philosophy, the Investigation of difficult Things by the Method of Analysis, ought ever to precede the Method of Composition.”

Opticks (1730), Query 31. 4th ed., London, Innys, 1730. View the source

“…every branch of physical science must consist of three things; the series of facts which are the objects of the science, the ideas which represent these facts, and the words by which these ideas are expressed.”

Original text“…toute science physique est nécessairement formée de trois choses: la série des faits qui constituent la science; les idées qui les rappellent; les mots qui les expriment.”

Traité élémentaire de chimie (1789), Discours préliminaire. Paris, Cuchet, 1789, vol. I. English translation: R. Kerr (trans.), Elements of Chemistry, Edinburgh, Creech, 1790. View the source

“Like three impressions of the same seal, the word ought to produce the idea, and the idea to be a picture of the fact.”

Original text“Le mot doit faire naître l'idée; l'idée doit peindre le fait: ce sont trois empreintes d'un même cachet…”

Traité élémentaire de chimie (1789), Discours préliminaire. Paris, Cuchet, 1789, vol. I. English translation: R. Kerr (trans.), Elements of Chemistry, Edinburgh, Creech, 1790. View the source

“…we cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science, without improving the language or nomenclature which belongs to it.”

Original text“…on ne peut perfectionner le langage sans perfectionner la science, ni la science sans le langage…”

Traité élémentaire de chimie (1789), Discours préliminaire. Paris, Cuchet, 1789, vol. I. English translation: R. Kerr (trans.), Elements of Chemistry, Edinburgh, Creech, 1790. View the source

“…I have imposed upon myself, as a law, never to advance but from what is known to what is unknown; never to form any conclusion which is not an immediate consequence necessarily flowing from observation and experiment…”

Original text“…je me suis imposé la loi de ne procéder jamais que du connu à l'inconnu, de ne déduire aucune conséquence qui ne dérive immédiatement des expériences & des observations…”

Traité élémentaire de chimie (1789), Discours préliminaire. Paris, Cuchet, 1789, vol. I. English translation: R. Kerr (trans.), Elements of Chemistry, Edinburgh, Creech, 1790. View the source

“Primary causes are unknown to us; but are subject to simple and constant laws, which may be discovered by observation, the study of them being the object of natural philosophy.”

Original text“Les causes primordiales ne nous sont point connues; mais elles sont assujetties à des lois simples et constantes, que l'on peut découvrir par l'observation, et dont l'étude est l'objet de la philosophie naturelle.”

Théorie analytique de la chaleur (1822), Discours préliminaire, p. i. Paris, Firmin Didot, 1822. English translation: A. Freeman (trans.), The Analytical Theory of Heat, Cambridge University Press, 1878. View the source

“Heat, like gravity, penetrates every substance of the universe, its rays occupy all parts of space.”

Original text“La chaleur pénètre, comme la gravité, toutes les substances de l'univers, ses rayons occupent toutes les parties de l'espace.”

Théorie analytique de la chaleur (1822), Discours préliminaire, p. i. Paris, Firmin Didot, 1822. English translation: A. Freeman (trans.), The Analytical Theory of Heat, Cambridge University Press, 1878. View the source

“Profound study of nature is the most fertile source of mathematical discoveries.”

Original text“L'étude approfondie de la nature est la source la plus féconde des découvertes mathématiques.”

Théorie analytique de la chaleur (1822), Discours préliminaire, p. xiii. Paris, Firmin Didot, 1822. English translation: A. Freeman (trans.), The Analytical Theory of Heat, Cambridge University Press, 1878. View the source

“…mathematical analysis is as extensive as nature itself; it defines all perceptible relations, measures times, spaces, forces, temperatures…”

Original text“…l'analyse mathématique est aussi étendue que la nature elle-même; elle définit tous les rapports sensibles, mesure les temps, les espaces, les forces, les températures…”

Théorie analytique de la chaleur (1822), Discours préliminaire, p. xiv. Paris, Firmin Didot, 1822. English translation: A. Freeman (trans.), The Analytical Theory of Heat, Cambridge University Press, 1878. View the source

“The effects of heat are subject to constant laws which cannot be discovered without the aid of mathematical analysis.”

Original text“Les effets de la chaleur sont assujétis à des lois constantes que l'on ne peut découvrir sans le secours de l'analyse mathématique.”

Théorie analytique de la chaleur (1822), Chapitre I, section I, art. 1, p. 1. Paris, Firmin Didot, 1822. English translation: A. Freeman (trans.), The Analytical Theory of Heat, Cambridge University Press, 1878. View the source

“Every one knows that heat can produce motion. That it possesses vast motive power no one can doubt…”

Original text“Personne n'ignore que la chaleur peut être la cause du mouvement, qu'elle possède même une grande puissance motrice…”

Réflexions sur la puissance motrice du feu (1824), p. 1. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“Nature, in providing us with combustibles on all sides, has given us the power to produce, at all times and in all places, heat and the impelling power which is the result of it.”

Original text“…la nature, en nous offrant de toutes parts le combustible, nous a donné la faculté de faire naître en tous temps et en tous lieux la chaleur et la puissance motrice qui en est la suite.”

Réflexions sur la puissance motrice du feu (1824), p. 2. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“To develop this power, to appropriate it to our uses, is the object of heat-engines.”

Original text“Développer cette puissance, l'approprier à notre usage, tel est l'objet des machines à feu.”

Réflexions sur la puissance motrice du feu (1824), p. 2. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“The study of these engines is of the greatest interest, their importance is enormous, their use is continually increasing, and they seem destined to produce a great revolution in the civilized world.”

Original text“L'étude de ces machines est du plus haut intérêt, leur importance est immense, leur emploi s'accroît tous les jours. Elles paraissent destinées à produire une grande révolution dans le monde civilisé.”

Réflexions sur la puissance motrice du feu (1824), p. 2. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“Notwithstanding the work of all kinds undertaken on heat engines, notwithstanding the satisfactory state they have reached today, their theory is very little advanced, and the attempts to improve them are still directed almost by chance.”

Original text“Malgré les travaux de tous genres entrepris sur les machines à feu, malgré l'état satisfaisant où elles sont aujourd'hui parvenues, leur théorie est fort peu avancée, et les essais d'amélioration tentés sur elles sont encore dirigés presque au hasard.”

Réflexions sur la puissance motrice du feu (1824), p. 6. París, Bachelier, 1824. Translation by INGEBIR. View the source

“The phenomenon of the production of motion by heat has not been considered from a sufficiently general point of view.”

Original text“Le phénomène de la production du mouvement par la chaleur n'a pas été considéré sous un point de vue assez général.”

Réflexions sur la puissance motrice du feu (1824), p. 7. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“…the production of heat alone is not sufficient to give birth to the impelling power: it is necessary that there should also be cold; without it, the heat would be useless.”

Original text“…il ne suffit pas, pour donner naissance à la puissance motrice, de produire de la chaleur: il faut encore se procurer du froid; sans lui la chaleur serait inutile.”

Réflexions sur la puissance motrice du feu (1824), p. 11. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“Wherever there exists a difference of temperature, wherever it has been possible for the equilibrium of the caloric to be re-established, it is possible to have also the production of impelling power.”

Original text“Partout où il existe une différence de température, partout où il peut y avoir rétablissement d'équilibre du calorique, il peut y avoir aussi production de puissance motrice.”

Réflexions sur la puissance motrice du feu (1824), p. 12. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“Heat can evidently be a cause of motion only by virtue of the changes of volume or of form which it produces in bodies.”

Original text“La chaleur ne peut évidemment être une cause de mouvement qu'en vertu des changemens de volume ou de forme qu'elle fait subir aux corps…”

Réflexions sur la puissance motrice du feu (1824), p. 14. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“The motive power of heat is independent of the agents employed to realize it; its quantity is fixed solely by the temperatures of the bodies between which is effected, finally, the transfer of the caloric.”

Original text“La puissance motrice de la chaleur est indépendante des agens mis en œuvre pour la réaliser; sa quantité est fixée uniquement par les températures des corps entre lesquels se fait en dernier résultat le transport du calorique.”

Réflexions sur la puissance motrice du feu (1824), p. 38. París, Bachelier, 1824. English translation: R. H. Thurston (trans.), Reflections on the Motive Power of Heat, New York, Wiley, 1897. View the source

“Heat is nothing other than motive power, or rather motion which has changed its form. It is a motion in the particles of bodies.”

Original text“La chaleur n'est autre chose que la puissance motrice, ou plutôt que le mouvement qui a changé de forme. C'est un mouvement dans les particules des corps.”

Extrait de notes inédites de Sadi Carnot (1878), p. 94. In Réflexions sur la puissance motrice du feu, new edition, Paris, Gauthier-Villars, 1878. Translation by INGEBIR. View the source

“We may therefore lay down as a general thesis that motive power exists in nature in an invariable quantity, that it is never, properly speaking, either produced or destroyed.”

Original text“On peut donc poser en thèse générale que la puissance motrice est en quantité invariable dans la nature, qu'elle n'est jamais, à proprement parler, ni produite, ni détruite.”

Extrait de notes inédites de Sadi Carnot (1878), p. 95. In Réflexions sur la puissance motrice du feu, new edition, Paris, Gauthier-Villars, 1878. Translation by INGEBIR. View the source

“Experiment has shown that wherever living force is apparently destroyed or absorbed, heat is produced.”

On Matter, Living Force, and Heat (1847), p. 269. The Scientific Papers of James Prescott Joule, vol. 1, London, 1884. View the source

“…wherever mechanical force is expended, an exact equivalent of heat is always obtained.”

On the Calorific Effects of Magneto-Electricity, and on the Mechanical Value of Heat (1843), p. 158. The Scientific Papers of James Prescott Joule, vol. 1, London, 1884. View the source

“Indeed the phenomena of nature, whether mechanical, chemical, or vital, consist almost entirely in a continual conversion of attraction through space, living force, and heat into one another.”

On Matter, Living Force, and Heat (1847), p. 273. The Scientific Papers of James Prescott Joule, vol. 1, London, 1884. View the source

“Any of your readers who are so fortunate as to reside amid the romantic scenery of Wales or Scotland could, I doubt not, confirm my experiments by trying the temperature of the water at the top and at the bottom of a cascade.”

On the Existence of an Equivalent Relation between Heat and the ordinary Forms of Mechanical Power (1845), p. 204. The Scientific Papers of James Prescott Joule, vol. 1, London, 1884. View the source

“…the quantity of heat produced by the friction of bodies, whether solid or liquid, is always proportional to the quantity of force expended.”

On the Mechanical Equivalent of Heat (1850), p. 328. The Scientific Papers of James Prescott Joule, vol. 1, London, 1884. View the source

“Energy, or the capacity to effect changes, is the common characteristic of the various states of matter to which the several branches of physics relate…”

Outlines of the Science of Energetics (1855), p. 213. Miscellaneous Scientific Papers, London, Griffin, 1881. View the source

“The law of the Conservation of Energy is already known—viz., that the sum of all the energies of the universe, actual and potential, is unchangeable.”

On the General Law of the Transformation of Energy (1853), p. 203. Miscellaneous Scientific Papers, London, Griffin, 1881. View the source

“…the science of thermodynamics is by no means dependent for its certainty on that or any other hypothesis, having been now reduced to a system of principles, or general facts, expressing strictly the results of experiment as to the relations between heat and motive power.”

A Manual of the Steam Engine and Other Prime Movers (1859), Introducción, p. xxxii. London and Glasgow, Griffin, 1859. View the source

“…in almost every branch of molecular physics it may be held, that a hypothetical theory is necessary, as a preliminary step, to reduce the expression of the phenomena to simplicity and order, before it is possible to make any progress in framing an abstractive theory.”

Outlines of the Science of Energetics (1855), p. 213. Miscellaneous Scientific Papers, London, Griffin, 1881. View the source

“Actual, or Sensible Energy, is a measurable, transmissible, and transformable condition, whose presence causes a substance to tend to change its state in one or more respects.”

On the General Law of the Transformation of Energy (1853), p. 203. Miscellaneous Scientific Papers, London, Griffin, 1881. View the source

“Whoever, in the pursuit of science, seeks after immediate practical utility, may generally rest assured that he will seek in vain.”

Original text“Wer bei der Verfolgung der Wissenschaften nach unmittelbarem praktischen Nutzen jagt, kann ziemlich sicher sein, dass er vergebens jagen wird.”

Ueber das Verhältniss der Naturwissenschaften zur Gesammtheit der Wissenschaft (1862). Academic address, Heidelberg, 1862. English translation: E. Atkinson (trans.), Popular Lectures on Scientific Subjects, London, Longmans, 1873. View the source

“But knowledge is not the sole object of man upon earth.”

Original text“Das Wissen allein ist aber nicht Zweck des Menschen auf der Erde.”

Ueber das Verhältniss der Naturwissenschaften zur Gesammtheit der Wissenschaft (1862). Academic address, Heidelberg, 1862. English translation: E. Atkinson (trans.), Popular Lectures on Scientific Subjects, London, Longmans, 1873. View the source

“…Nature as a whole possesses a store of force which cannot in any way be either increased or diminished…”

Original text“…dass das Naturganze einen Vorrath wirkungsfähiger Kraft besitzt, welcher in keiner Weise weder vermehrt, noch vermindert werden kann…”

Ueber die Wechselwirkung der Naturkräfte (1854). Königsberg, Gräfe & Unzer, 1854. English translation: E. Atkinson (trans.), Popular Lectures on Scientific Subjects, London, Longmans, 1873. View the source

“We start from the assumption that it is impossible, by any combination of natural bodies, to create motive force continually out of nothing.”

Original text“Wir gehen aus von der Annahme, dass es unmöglich sei, durch irgend eine Combination von Naturkörpern bewegende Kraft fortdauernd aus nichts zu erschaffen.”

Über die Erhaltung der Kraft (1847), p. 7. Berlin, G. Reimer, 1847. Translation by INGEBIR. View the source

“…science, whose purpose is to comprehend nature, must start from the presupposition that nature is comprehensible…”

Original text“…die Wissenschaft, deren Zweck es ist, die Natur zu begreifen, von der Voraussetzung ihrer Begreiflichkeit ausgehen müsse…”

Über die Erhaltung der Kraft (1847), Einleitung. Berlin, G. Reimer, 1847. Translation by INGEBIR. View the source

“The energy of the universe is constant. The entropy of the universe tends to a maximum.”

Original text“Die Energie der Welt ist constant. Die Entropie der Welt strebt einem Maximum zu.”

Ueber verschiedene für die Anwendung bequeme Formen der Hauptgleichungen der mechanischen Wärmetheorie (1865), p. 400. Annalen der Physik und Chemie, 125, 1865. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“I have intentionally formed the word entropy so as to be as similar as possible to the word energy; for the two magnitudes to be denoted by these words are so nearly allied in their physical meanings, that a certain similarity in designation appears to be desirable.”

Original text“Das Wort Entropie habe ich absichtlich dem Worte Energie möglichst ähnlich gebildet, denn die beiden Gröſsen, welche durch diese Worte benannt werden sollen, sind ihren physikalischen Bedeutungen nach einander so nahe verwandt, daſs eine gewisse Gleichartigkeit in der Benennung mir zweckmäſsig zu seyn scheint.”

Ueber verschiedene für die Anwendung bequeme Formen der Hauptgleichungen der mechanischen Wärmetheorie (1865), § 14, p. 390. Annalen der Physik und Chemie, 125, 1865. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“Heat cannot by itself pass from a colder to a warmer body…”

Original text“…die Wärme kann nicht von selbst aus einem kälteren in einen wärmeren Körper übergehen…”

Abhandlungen über die mechanische Wärmetheorie (1864), Abh. IV, nota de 1864, p. 134. Braunschweig, Vieweg, 1864, part one. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“In all cases where work is produced by heat, a quantity of heat proportional to the work done is consumed; and inversely, by the expenditure of a like quantity of work, the same amount of heat may be produced.”

Original text“…daſs in allen Fällen, wo durch Wärme Arbeit entstehe, eine der erzeugten Arbeit proportionale Wärmemenge verbraucht werde, und daſs umgekehrt durch Verbrauch einer ebenso groſsen Arbeit dieselbe Wärmemenge erzeugt werden könne.”

Ueber die bewegende Kraft der Wärme (1850), p. 373. Annalen der Physik und Chemie, 79, 1850. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“It may be remarked further, that many facts have lately transpired which tend to overthrow the hypothesis that heat is itself a body, and to prove that it consists in a motion of the ultimate particles of bodies.”

Original text“Dazu kommt noch, daſs in neuerer Zeit immer noch mehr Thatsachen bekannt werden, welche dafür sprechen, daſs die Wärme nicht ein Stoff sey, sondern in einer Bewegung der kleinsten Theile der Körper bestehe.”

Ueber die bewegende Kraft der Wärme (1850), pp. 369–370. Annalen der Physik und Chemie, 79, 1850. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“I believe, nevertheless, that we ought not to suffer ourselves to be daunted by these difficulties; but that, on the contrary, we must look steadfastly into this theory which calls heat a motion, as in this way alone can we arrive at the means of establishing it or refuting it.”

Original text“Ich glaube aber, daſs man vor diesen Schwierigkeiten nicht zurückschrecken darf, und sich vielmehr mit den Folgen der Idee, daſs die Wärme eine Bewegung sey, möglichst vertraut machen muſs, indem man nur dadurch die Mittel gewinnen kann, dieselbe zu bestätigen oder zu widerlegen.”

Ueber die bewegende Kraft der Wärme (1850), p. 372. Annalen der Physik und Chemie, 79, 1850. English translation: T. A. Hirst (ed.), The Mechanical Theory of Heat, London, Van Voorst, 1867. View the source

“In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and methods for practicably measuring some quality connected with it.”

Electrical Units of Measurement (1883), p. 73. Popular Lectures and Addresses, vol. 1, London, Macmillan, 1889. View the source

“I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind…”

Electrical Units of Measurement (1883), p. 73. Popular Lectures and Addresses, vol. 1, London, Macmillan, 1889. View the source

“There cannot be a greater mistake than that of looking superciliously upon practical applications of science. The life and soul of science is its practical application…”

Electrical Units of Measurement (1883), p. 79. Popular Lectures and Addresses, vol. 1, London, Macmillan, 1889. View the source

“Considering it as thus established, that heat is not a substance, but a dynamical form of mechanical effect, we perceive that there must be an equivalence between mechanical work and heat, as between cause and effect.”

On the Dynamical Theory of Heat (1851), § 4, p. 175. Mathematical and Physical Papers, vol. 1, Cambridge, 1882. View the source

“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.”

On the Dynamical Theory of Heat (1851), § 12, p. 179. Mathematical and Physical Papers, vol. 1, Cambridge, 1882. View the source

“There is at present in the material world a universal tendency to the dissipation of mechanical energy.”

On a Universal Tendency in Nature to the Dissipation of Mechanical Energy (1852), p. 514. Mathematical and Physical Papers, vol. 1, Cambridge, 1882. View the source

“The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds.”

Nineteenth Century Clouds over the Dynamical Theory of Heat and Light (1900), § 1, p. 486. Baltimore Lectures, Appendix B, London, C. J. Clay, 1904. View the source

“But if we conceive a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are still as essentially finite as our own, would be able to do what is at present impossible to us.”

Theory of Heat (1871), p. 308. London, Longmans, Green, and Co., 1871. View the source

“…the idea of dissipation of energy depends on the extent of our knowledge.”

Diffusion (1877), p. 646. Encyclopaedia Britannica, 9th ed.; The Scientific Papers of James Clerk Maxwell, vol. 2, Cambridge, 1890. View the source

“Available energy is energy which we can direct into any desired channel. Dissipated energy is energy which we cannot lay hold of and direct at pleasure, such as the energy of the confused agitation of molecules which we call heat.”

Diffusion (1877), p. 646. Encyclopaedia Britannica, 9th ed.; The Scientific Papers of James Clerk Maxwell, vol. 2, Cambridge, 1890. View the source

“Now, confusion, like the correlative term order, is not a property of material things in themselves, but only in relation to the mind which perceives them.”

Diffusion (1877), p. 646. Encyclopaedia Britannica, 9th ed.; The Scientific Papers of James Clerk Maxwell, vol. 2, Cambridge, 1890. View the source

“…the history of science shews that even during that phase of her progress in which she devotes herself to improving the accuracy of the numerical measurement of quantities with which she has long been familiar, she is preparing the materials for the subjugation of new regions…”

Introductory Lecture on Experimental Physics (1871), p. 244. The Scientific Papers of James Clerk Maxwell, vol. 2, Cambridge, 1890. View the source

“An atom is a body which cannot be cut in two. A molecule is the smallest possible portion of a particular substance.”

Molecules (1873), p. 437. Nature, 8, 1873. View the source

“One of the principal objects of theoretical research in any department of knowledge is to find the point of view from which the subject appears in its greatest simplicity.”

Letter accepting the Rumford Medal (1881), p. 420. Proceedings of the American Academy of Arts and Sciences, 16, 1881. View the source

“The comprehension of the laws which govern any material system is greatly facilitated by considering the energy and entropy of the system in the various states of which it is capable.”

On the Equilibrium of Heterogeneous Substances (1876), p. 55. The Scientific Papers of J. Willard Gibbs, vol. 1, New York, Longmans, 1906. View the source

“For the equilibrium of any isolated system it is necessary and sufficient that in all possible variations of the state of the system which do not alter its energy, the variation of its entropy shall either vanish or be negative.”

On the Equilibrium of Heterogeneous Substances (1876), p. 56. The Scientific Papers of J. Willard Gibbs, vol. 1, New York, Longmans, 1906. View the source

“…the impossibility of an uncompensated decrease of entropy seems to be reduced to improbability.”

On the Equilibrium of Heterogeneous Substances (1876), p. 167. The Scientific Papers of J. Willard Gibbs, vol. 1, New York, Longmans, 1906. View the source

“The laws of thermodynamics, as empirically determined, express the approximate and probable behavior of systems of a great number of particles…”

Elementary Principles in Statistical Mechanics (1902), Preface, p. viii. New York, Scribner's, 1902. View the source

“The general struggle for existence of animate beings is therefore not a struggle for raw materials … nor for energy … but a struggle for entropy, which becomes available through the transition of energy from the hot sun to the cold earth.”

Original text“Der allgemeine Daseinskampf der Lebenswesen ist daher nicht ein Kampf um die Grundstoffe … auch nicht um Energie … sondern ein Kampf um die Entropie, welche durch den Übergang der Energie von der heißen Sonne zur kalten Erde disponibel wird.”

Der zweite Hauptsatz der mechanischen Wärmetheorie (1886), p. 40. Populäre Schriften, Leipzig, Barth, 1905. English translation: B. McGuinness (ed.), Theoretical Physics and Philosophical Problems, Dordrecht, Reidel, 1974. View the source

“Nowhere less than in natural science does the proposition that the straight path is the shortest turn out to be true.”

Original text“Nirgends weniger als in der Naturwissenschaft bewahrheitet sich der Satz, daß der gerade Weg der kürzeste ist.”

Der zweite Hauptsatz der mechanischen Wärmetheorie (1886), p. 26. Populäre Schriften, Leipzig, Barth, 1905. English translation: B. McGuinness (ed.), Theoretical Physics and Philosophical Problems, Dordrecht, Reidel, 1974. View the source

“The form of energy we need for our purposes is always that of work or of visible motion.”

Original text“Die Energieform, welche wir für unsere Zwecke benötigen, ist immer die der Arbeit oder sichtbaren Bewegung.”

Der zweite Hauptsatz der mechanischen Wärmetheorie (1886), p. 33. Populäre Schriften, Leipzig, Barth, 1905. Translation by INGEBIR. View the source

“Who sees the future? Let us have free scope for all directions of research; away with all dogmatism, either atomistic or antiatomistic!”

Original text“Wer sieht in die Zukunft? Darum freie Bahn für jede Richtung, weg mit jeder Dogmatik in atomistischem und antiatomistischem Sinne!”

Vorlesungen über Gastheorie (1896), § 1, p. 4. Leipzig, Barth, 1896, part one. English translation: S. G. Brush (trans.), Lectures on Gas Theory, Berkeley, University of California Press, 1964. View the source

“We infer the existence of all things solely from the impressions they make on our senses.”

Original text“Wir erschließen die Existenz aller Dinge bloß aus den Eindrücken, welche sie auf unsere Sinne machen.”

Der zweite Hauptsatz der mechanischen Wärmetheorie (1886), p. 29. Populäre Schriften, Leipzig, Barth, 1905. Translation by INGEBIR. View the source

“A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”

Original text“Eine neue wissenschaftliche Wahrheit pflegt sich nicht in der Weise durchzusetzen, daß ihre Gegner überzeugt werden und sich als belehrt erklären, sondern vielmehr dadurch, daß die Gegner allmählich aussterben und daß die heranwachsende Generation von vornherein mit der Wahrheit vertraut gemacht ist.”

Wissenschaftliche Selbstbiographie (1948). Leipzig, Barth, 1948. English translation: F. Gaynor (trans.), Scientific Autobiography and Other Papers, New York, Philosophical Library, 1949.

“In this connection, it is of paramount importance that the outside world is something independent from man, something absolute, and the quest for the laws which apply to this absolute appeared to me as the most sublime scientific pursuit in life.”

Original text“Dabei ist von wesentlicher Bedeutung, daß die Außenwelt etwas von uns Unabhängiges, Absolutes darstellt, dem wir gegenüberstehen, und das Suchen nach den Gesetzen, die für dieses Absolute gelten, erschien mir als die schönste wissenschaftliche Lebensaufgabe.”

Wissenschaftliche Selbstbiographie (1948). Leipzig, Barth, 1948. English translation: F. Gaynor (trans.), Scientific Autobiography and Other Papers, New York, Philosophical Library, 1949.

“One day, I happened to come across the treatises of Rudolf Clausius, whose lucid style and enlightening clarity of reasoning made an enormous impression on me, and I became deeply absorbed in his articles, with an ever increasing enthusiasm.”

Original text“So kam es, daß mir die Abhandlungen von Rudolph Clausius in die Hände fielen, deren wohlverständliche Sprache und einleuchtende Klarheit mir einen gewaltigen Eindruck machten und in die ich mich mit wachsender Begeisterung vertiefte.”

Wissenschaftliche Selbstbiographie (1948). Leipzig, Barth, 1948. English translation: F. Gaynor (trans.), Scientific Autobiography and Other Papers, New York, Philosophical Library, 1949.

“The process of heat conduction cannot be completely reversed by any means.”

Original text“Der Prozeß der Wärmeleitung läßt sich auf keinerlei Weise vollständig rückgängig machen.”

Wissenschaftliche Selbstbiographie (1948). Leipzig, Barth, 1948. English translation: F. Gaynor (trans.), Scientific Autobiography and Other Papers, New York, Philosophical Library, 1949.

“The first law of thermodynamics is nothing more than the principle of the conservation of energy applied to phenomena involving the production or absorption of heat.”

Original text“Der erste Hauptsatz der Wärmetheorie ist nichts anderes, als das Princip der Erhaltung der Energie, angewendet auf die Erscheinungen, welche unter Wärme-Produktion oder -Absorption verlaufen.”

Vorlesungen über Thermodynamik (1897), § 55. Leipzig, Veit, 1897. English translation: A. Ogg (trans.), Treatise on Thermodynamics, 3rd English ed., translated from the 7th German ed., London, Longmans. View the source

“It is impossible to construct an engine which will work in a complete cycle, and produce no effect except the raising of a weight and the cooling of a heat-reservoir.”

Original text“Es ist unmöglich, eine periodisch funktionirende Maschine zu construiren, die weiter nichts bewirkt als Hebung einer Last und Abkühlung eines Wärmereservoirs.”

Vorlesungen über Thermodynamik (1897), § 116. Leipzig, Veit, 1897. English translation: A. Ogg (trans.), Treatise on Thermodynamics, 3rd English ed., translated from the 7th German ed., London, Longmans. View the source

“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.”

Original text“Eine Theorie ist desto eindrucksvoller, je grösser die Einfachheit ihrer Prämissen ist, je verschiedenartigere Dinge sie verknüpft, und je weiter ihr Anwendungsbereich ist.”

Autobiographisches (1949), p. 32. In P. A. Schilpp (ed.), Albert Einstein: Philosopher-Scientist, Evanston, 1949. English translation: P. A. Schilpp (trans.), Autobiographical Notes, 1949. View the source

“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).”

Original text“Deshalb der tiefe Eindruck, den die klassische Thermodynamik auf mich machte. Es ist die einzige physikalische Theorie allgemeinen Inhaltes, von der ich überzeugt bin, dass sie im Rahmen der Anwendbarkeit ihrer Grundbegriffe niemals umgestossen werden wird (zur besonderen Beachtung der grundsätzlichen Skeptiker).”

Autobiographisches (1949), p. 32. In P. A. Schilpp (ed.), Albert Einstein: Philosopher-Scientist, Evanston, 1949. English translation: P. A. Schilpp (trans.), Autobiographical Notes, 1949. View the source

“The example I saw before me was thermodynamics. The general principle was there given in the theorem: the laws of nature are such that it is impossible to construct a perpetuum mobile (of the first and second kind).”

Original text“Als Vorbild sah ich die Thermodynamik vor mir. Das allgemeine Prinzip war dort in dem Satze gegeben: die Naturgesetze sind so beschaffen, dass es unmöglich ist, ein perpetuum mobile (erster und zweiter Art) zu konstruieren.”

Autobiographisches (1949), p. 52. In P. A. Schilpp (ed.), Albert Einstein: Philosopher-Scientist, Evanston, 1949. English translation: P. A. Schilpp (trans.), Autobiographical Notes, 1949. View the source

“The mass of a body is a measure of its energy-content…”

Original text“Die Masse eines Körpers ist ein Maß für dessen Energieinhalt…”

Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig? (1905), p. 641. Annalen der Physik, 18, 1905. English translation: W. Perrett and G. B. Jeffery (trans.), The Principle of Relativity, London, Methuen, 1923. View the source