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# History of thermodynamics

The history of thermodynamics is a fundamental strand in the history of physics, the history of chemistry, and the history of science in general. Owing to the relevance of thermodynamics in much of science and technology, its history is finely woven with the developments of classical mechanics, quantum mechanics, magnetism, and chemical kinetics, to more distant applied fields such as meteorology, information theory, and biology (physiology), and to technological developments such as the steam engine, internal combustion engine, cryogenics and electricity generation. The development of thermodynamics both drove and has been driven by atomic theory. It also, albeit in a subtle manner, motivated new directions in probability and statistics; see, for example, the timeline of thermodynamics, statistical mechanics, and random processes.

## Short history

The short history of thermodynamics, with focus on the essential stepping stones that inherently functioned to stimulate modern thermodynamics, began with the arguments of the 5th century Greek philosopher Parmenides. In his only known work, a poem conventionally titled 'On Nature', Parmenides uses verbal reasoning to postulate that a void, essentially what is now known as a vacuum, in nature could not occur. This statement was disproved conclusively, approximately two-thousand years later, when Otto von Guericke built a vacuum pump, which was used to affix together his famous “Magdeburg Hemispheres” that he so proudly displayed around Europe in the mid 17th century. Soon thereafter, stimulated into conception by von Guericke’s vacuum pump design, the steam engine was built. The rest is thermodynamic history:

• In c.485 BC, Parmenides makes the ontological argument against nothingness, essentially denying the possible existence of a void.
• In c.460 BC, Leucippus, in opposition to Parmenides' denial of the void, proposes the atomic theory, which supposes that everything in the universe is either atoms or voids; a theory which, according to Aristotle, was stimulated into conception so to purposely contradict Parmenides' argument.
• In c.350 BC, Aristotle proclaims, in opposition to Leucippus, the dictum horror vacui or “nature abhors a vacuum”. Aristotle reasoned that in a complete vacuum, infinite speed would be possible because motion would encounter no resistance. Since he did not accept the possibility of infinite speed, he decided that a vacuum was equally impossible.

• In 1643, Galileo Galilei, while generally accepting the horror vacui of Aristotle, believes that nature’s vacuum-abhorrence is limited. Pumps operating in mines had already proven that nature would only fill a vacuum with water up to a height of 30 feet. Knowing this curious fact, Galileo encourages his former pupil Evangelista Torricelli to investigate these supposed limitations. Torricelli did not believe that vacuum-abhorrence was responsible for raising the water. Rather, he reasoned, it was the result of the pressure exerted on the liquid by the surrounding air. To prove this theory, he filled a glass tube, sealed at one end, filled with mercury and upended it into a dish also containing mercury. Only a portion of the tube emptied (as shown adjacent); 30 inches of the liquid remained. As the mercury emptied, a vacuum was created at the top of the tube. This, the first man-made vacuum, effectively disproved Aristotle’s theory and affirmed the existence of vacuums in nature.
• In 1650, Otto von Guericke, stimulated by the work Galileo and Torricelli, to further disprove Aristotle's supposition that nature abhors a vacuum, constructs the world’s first-ever vacuum pump and uses it to unite the Magdeburg Hemispheres. In doing so, von Guericke shows that in a vacuum sound cannot travel, candles could not burn, and animals could not live.
• In 1656, Robert Boyle, having learned of von Guericke’s vacuum pump designs, works in coordination with Robert Hooke to build an air pump. Using this pump, Boyle and Hooke notice that vessels filled with air become warmer as their internal pressure is increased. In time, the ideal gas law is formulated.
• In 1679, Denis Papin, an associate of Boyle's, uses the pressure-temperature correlation to build a bone digester, which is a closed vessel with a tightly fitting lid that confines steam until a high pressure is generated. Later designs implemented a steam release valve to keep the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and cylinder engine. He did not however follow through with his design.
• In 1697, Thomas Savery, using Papin’s designs, builds the world’s first engine. In time, other engines were built as the Newcomen engine and the Watt engine. These early engines, however, were crude and inefficient, converting less than two percent of their input energy into useful work output. This efficiency problem soon began to attract the attention of the leading scientists of the day.
• In 1824, Nicolas Léonard Sadi Carnot, so as to put the engine-efficiency problem on a mathematical footing, publishes Reflections on the Motive Power of Fire, a discourse on heat, power, and engine efficiency. This marks the start of thermodynamics as a modern science.
• In 1842, Julius Robert von Mayer proposes that energy in a closed system is constant, being neither created or destroyed by internal processes.
• in 1843, James Prescott Joule publishes highly detailed results of experiments that supported Mayer's proposal that energy that be neither created or destroyed.
• In 1850-65, Rudolf Clausius, situated on the work of Carnot, develops the concept of entropy, or energy lost to dissipation.[1]
• In 1871, James Clerk Maxwell, published his famous Theory of Heat, in which he sets forth the fundamentals of thermodynamics clearly and simply enough to be understood by the beginning student.
• In 1874, first-year medical student Sigmund Freud began to develop the new science of psychodynamics under the influence of his mentor Ernst von Brucke who had just published Lectures on Physiology supposed that all living organisms are energy-systems governed by the first law of thermodynamics (conservation of energy) and Brucke's associate Hermann von Helmholtz, one of the founders of the first law of thermodynamics.
• In 1876, Willard Gibbs, building on the work of Clausius, Carnot and others, publishes On the Equilibrium of Heterogeneous Substances”, which marks the beginning of chemical thermodynamics and which integrates chemical, physical, electrical, and electromagnetic phenomena into a cohesive system, and introduces the phase rule, which forms the basis for modern physical chemistry and thermochemistry.
• In 1882, building on the work of Clausius and Gibbs, Hermann von Helmholtz pointed out that the ancient chemistry notion of chemical affinity is not the heat evolved in the formation of a compound but rather it is the largest quantity of work, i.e. free energy, that can be gained when the reaction is carried out in a reversible manner, e.g. electrical work in a reversible cell.
• In 1896, building on the work of Clausius and James Maxwell, Ludwig Boltzmann’s famous Lectures on Gas Theory was published, which usher in the new field of statistical thermodynamics
• In 1897, Max Planck, published his Treatise on Thermodynamics, in which he rejects earlier views of Helmholtz and Maxwell, i.e. he makes no assumptions regarding the nature of heat, but instead deduces new physical and chemical laws.
• In 1923, the influential textbook Thermodynamics and the Free Energy of Chemical Reactions by Gilbert N. Lewis and Merle Randall led to the replacement of the term “affinity” by the term “free energy” in much of the English-speaking world.
• In 1965, mechanical engineers George Hatsopoulos and Joseph Keenan published their famous textbook Principles in General Thermodynamics, in which they showed that the second law of thermodynamics could be stated in terms of the existence of stable equilibrium states.

## Long history

The long history of thermodynamics, may very well rightly include contributions from nearly all branches of science:

### Contributions from antiquity

In the western philosophical tradition, after much debate about the primal element among earlier pre-Socratic philosophers, Empedocles proposed a four-element theory, in which all substances derive from earth, water, air, and fire. The Empedoclean element of fire is perhaps the principal ancestor of later concepts such as phlogiston and caloric.

Atomism is a central part of today's relationship between thermodynamics and statistical mechanics. Ancient thinkers such as Leucippus and Democritus, and later the Epicureans, by advancing atomism, laid the foundations for the later atomic theory. Until experimental proof of atoms was later provided in the 20th century, the atomic theory was driven largely by philosophical considerations and scientific intuition. Consequently, ancient philosophers used atomic theory to reach conclusions that today may be viewed as immature: for example, Democritus gives a vague atomistic description of the soul, namely that it is "built from thin, smooth, and round atoms, similar to those of fire".

### Transition from alchemy to chemistry

The theory of phlogiston arose in the 17th century, late in the period of alchemy. Its replacement by caloric theory in the 18th century is one of the historical markers of the transition from alchemy to chemistry. Phlogiston was supposed to be liberated from combustible substances during burning, and from metals during the process of rusting.

The first substantial experimental challenges to caloric theory arose in Rumford's 1798 work, though his experiments were poorly controlled, and most of the scientific establishment had enough confidence in caloric theory to believe that it could account for the results. More quantitative studies by James Prescott Joule in 1843 onwards provided soundly reproducible phenomena, but still met with scant enthusiasm. William Thomson, for example, was still trying to explain Joule's observations within a caloric framework as late as 1850. The utility and explanatory power of kinetic theory, however, soon started to displace caloric and it was largely obsolete by the end of the 19th century.

### Modern Theory

At its origins, thermodynamics was the study of engines. A precursor of the engine was designed by the German scientist Otto von Guericke who in 1650 built and designed the world's first vacuum pump and created the world's first ever vacuum known as the Magdeburg hemispheres. He was driven to make a vacuum in order to disprove Aristotle's long-held supposition that 'Nature abhors a vacuum'.

Shortly thereafter, Irish physicist and chemist Robert Boyle had learned of Guericke's designs and in 1656, in coordination with English scientist Robert Hooke, built an air pump. Using this pump, Boyle and Hooke noticed the pressure-temperature-volume correlation. In time, the ideal gas law was formulated. Then, in 1679, based on these concepts, an associate of Boyle's named Denis Papin built a bone digester, which is a closed vessel with a tightly fitting lid that confines steam until a high pressure is generated.

Later designs implemented a steam release valve to keep the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and cylinder engine. He did not however follow through with his design. Nevertheless, in 1697, based on Papin’s designs, engineer Thomas Savery built the first engine. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. One such scientist was Sadi Carnot, the “father of thermodynamics”, who in 1824 published “Reflections on the Motive Power of Fire”, a discourse on heat, power, and engine efficiency. This marks the start of thermodynamics as a modern science.

Hence, prior to 1698 and the invention of the Savery Engine, horses were used to power pulleys, attached to buckets, which lifted water out of flooded salt mines in England. In the years to follow, more variations of steam engines were built, such as the Newcomen Engine, and later the Watt Engine. In time, these early engines would eventually be utilized in place of horses. Thus, each engine began to be associated with a certain amount of "horse power" depending upon how many horses it had replaced! The main problem with these first engines was that they were slow and clumsy, converting less than 2% of the input fuel into useful work. In other words, large quantities of coal (or wood) had to be burned to yield only a small fraction of work output. Hence the need for a new science of engine dynamics was born.

Most cite Sadi Carnot’s 1824 paper Reflections on the Motive Power of Fire as the starting point for thermodynamics as a modern science. Carnot defined "motive power" to be the expression of the useful effect that a motor is capable of producing. Herein, Carnot introduced us to the first modern day definition of "work": weight lifted through a height. The desire to understand, via formulation, this useful effect in relation to "work" is at the core of all modern day thermodynamics.

The name "thermodynamics," however, did not arrive until some twenty-five years later when, in 1849, the British mathematician and physicist William Thomson (Lord Kelvin) coined the term thermodynamics in a paper on the efficiency of steam engines. In 1850, the famed mathematical physicist Rudolf Clausius originated and defined the term enthalpy H to be the total heat content of the system, stemming from the Greek word enthalpein meaning to warm, and defined the term entropy S to be the heat lost or turned into waste, stemming from the Greek word entrepein meaning to turn.

In association with Clausius, in 1871, a Scottish mathematician and physicist James Clerk Maxwell formulated a new branch of thermodynamics called Statistical Thermodynamics, which functions to analyze large numbers of particles at equilibrium, i.e., systems where no changes are occurring, such that only their average properties as temperature T, pressure P, and volume V become important.

Soon thereafter, in 1875, the Austrian physicist Ludwig Boltzmann formulated a precise connection between entropy S and molecular motion:

$S=k\log W \,$

being defined in terms of the number of possible states [W] such motion could occupy, where k is the Boltzmann's constant. The following year, 1876, was a seminal point in the development of human thought. During this essential period, chemical engineer Willard Gibbs, the first person in America to be awarded a PhD in engineering (Yale), published an obscure 300-page paper titled: On the Equilibrium of Heterogeneous Substances, wherein he formulated one grand equality, the Gibbs free energy equation, which gives a measure the amount of "useful work" attainable in reacting systems.

Building on these foundations, those as Lars Onsager, Erwin Schrodinger, and Ilya Prigogine, and others, functioned to bring these engine "concepts" into the thoroughfare of almost every modern-day branch of science.

### Kinetic theory

The idea that heat is a form of motion is perhaps an ancient one and is certainly discussed by Francis Bacon in 1620 in his Novum Organum. The first written scientific reflection on the microscopic nature of heat is probably to be found in a work by Mikhail Lomonosov, in which he wrote:

"(..) movement should not be denied based on the fact it is not seen. Who would deny that the leaves of trees move when rustled by a wind, despite it being unobservable from large distances? Just as in this case motion remains hidden due to perspective, it remains hidden in warm bodies due to the extremely small sizes of the moving particles. In both cases, the viewing angle is so small that neither the object nor their movement can be seen."

During the same years, Daniel Bernoulli published his book Hydrodynamics (1738), in which he derived an equation for the pressure of a gas considering the collisions of its atoms with the walls of a container. He proves that this pressure is two thirds the average kinetic energy of tha gas in a unit volume. Bernoulli's ideas, however, made little impact on the dominant caloric culture. Bernoulli made a connection with Gottfried Leibniz's vis viva principle, an early formulation of the principle of conservation of energy, and the two theories became intimately entwined throughout their history. Though Benjamin Thompson suggested that heat was a form of motion as a result of his experiments in 1798, no attempt was made to reconcile theoretical and experimental approaches, and it is unlikely that he was thinking of the vis viva principle.

John Herapath later independently formulated a kinetic theory in 1820, but mistakenly associated temperature with momentum rather than vis viva or kinetic energy. His work ultimately failed peer review and was neglected. John James Waterston in 1843 provided a largely accurate account, again independently, but his work received the same reception, failing peer review even from someone as well-disposed to the kinetic principle as Davy.

Further progress in kinetic theory started only in the middle of the XIX century, with the works of Rudolf Clausius, James Clerk Maxwell, and Ludwig Boltzmann. In his 1857 work On the nature of the motion called heat, Clausius for the first time clearly states that heat is the average kinetic energy of molecules. This interested Maxwell, who in 1859 derived the momentum distribution later named after him. Boltzmann subsequently generalized his distribution for the case of gases in external fields.

Boltzmann is perhaps the most significant contributor to kinetic theory, as he introduced many of the fundamental concepts in the theory. Besides the Boltzmann distribution mentioned above, he also associated the kinetic energy of particles with their degrees of freedom. The Boltzmann equation for the distribution function of a gas in non-equilibrium states is still the most effective equation for studying transport phenomena in gases and metals. By introducing the concept of thermodynamic probability as the number of microstates corresponding to the current macrostate, he showed that its logarithm is proportional to entropy.

## Branches of

The following list gives a rough outline as to when the major branches of thermodynamics came into inception:

## Entropy and the second law

Main article: History of entropy

Even though he was working with the caloric theory, Sadi Carnot in 1824 suggested that some of the caloric available for generating useful work is lost in any real process. In March 1851, while grappling to come to terms with the work of James Prescott Joule, Lord Kelvin started to speculate that there was an inevitable loss of useful heat in all processes. The idea was framed even more dramatically by Hermann von Helmholtz in 1854, giving birth to the spectre of the heat death of the universe.

In 1854, William John Macquorn Rankine started to make use in calculation of what he called his thermodynamic function. This has subsequently been shown to be identical to the concept of entropy formulated by Rudolf Clausius in 1865. Clausius used the concept to develop his classic statement of the second law of thermodynamics the same year.

## Heat transfer

Main article: Heat transfer

The phenomenon of heat conduction is immediately grasped in everyday life. In 1701, Sir Isaac Newton published his law of cooling. However, in the 17th century, it came to be believed that all materials had an identical conductivity and that differences in sensation arose from their different heat capacities.

Suggestions that this might not be the case came from the new science of electricity in which it was easily apparent that some materials were good electrical conductors while others were effective insulators. Jan Ingen-Housz in 1785-9 made some of the earliest measurements, as did Benjamin Thompson during the same period.

The fact that warm air rises and the importance of the phenomenon to meteorology was first realised by Edmund Halley in 1686. Sir John Leslie observed that the cooling effect of a stream of air increased with its speed, in 1804.

Carl Wilhelm Scheele distinguished heat transfer by thermal radiation (radiant heat) from that by convection and conduction in 1777. In 1791, Pierre Prévost showed that all bodies radiate heat, no matter how hot or cold they are. In 1804, Leslie observed that a matt black surface radiates heat more effectively than a polished surface, suggesting the importance of black body radiation. Though it had become to be suspected even from Scheele's work, in 1831 Macedonio Melloni demonstrated that black body radiation could be reflected, refracted and polarised in the same way as light.

James Clerk Maxwell's 1862 insight that both light and radiant heat were forms of electromagnetic wave led to the start of the quantitative analysis of thermal radiation. In 1879, Jožef Stefan observed that the total radiant flux from a blackbody is proportional to the fourth power of its temperature and stated the Stefan-Boltzmann law. The law was derived theoretically by Ludwig Boltzmann in 1884.

## Cryogenics

In 1702 Guillaume Amontons introduced the concept of absolute zero based on observations of gases. In 1810, Sir John Leslie froze water to ice artificially. The idea of absolute zero was generalised in 1848 by Lord Kelvin. In 1906, Walther Nernst stated the third law of thermodynamics.