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History Of Thermodynamics

The history of thermodynamics is a crucial narrative thread within the broader tapestry of the history of physics, the history of chemistry, and indeed, the entirety of scientific history. Its significance isn't confined to a single discipline; thermodynamics is so deeply intertwined with countless scientific and technological advancements that its story is inseparable from the evolution of classical mechanics, the advent of quantum mechanics, the understanding of magnetism, and the intricacies of chemical kinetics. Its influence extends even to fields seemingly distant, such as meteorology, information theory, and biology, particularly in the realm of physiology. Moreover, its development was a direct catalyst for, and in turn was spurred by, the progress in atomic theory. It even, in ways both subtle and profound, nudged the development of probability and [statistics] in new directions, a journey meticulously documented in the timeline of thermodynamics.

Antiquity

The ancient world's understanding of heat was largely bound to the concept of fire. As early as 3000 BC, the ancient Egyptians wove narratives of heat into their origin myths. Similarly, ancient Indian philosophy, particularly Vedic thought, posited that the five classical elements, or pancha mahā bhūta, formed the bedrock of all cosmic creation. Within the Western philosophical tradition, after considerable debate among the early pre-Socratic philosophers regarding the fundamental element, Empedocles proposed a four-element theory: earth, water, air, and fire. This concept of fire, as an elemental substance, can be seen as a precursor to later notions like phlogiston and caloric. Around 500 BC, the Greek philosopher Heraclitus, known as the "flux and fire" philosopher, articulated his famous assertion: "All things are flowing." Heraclitus contended that the three primary elements shaping nature were fire, earth, and water.

Vacuum-abhorrence

The concept of a vacuum and its potential existence in nature was a subject of intense philosophical scrutiny from antiquity. The 5th-century BC Greek philosopher Parmenides, in his seminal work On Nature, employed rigorous verbal reasoning to argue against the possibility of a void. This perspective found support in the arguments of Aristotle, though it was notably challenged by thinkers like Leucippus and Hero of Alexandria. Throughout antiquity and into the Middle Ages, a persistent debate raged regarding the existence of a vacuum, accompanied by various attempts to create one, all of which ultimately proved unsuccessful.

The act of heating a body, such as the alpha helix segment of a protein depicted above, typically leads to increased atomic vibration and, often, expansion of the body itself. If heating continues, a change in phase may occur. This fundamental axiom of nature was observed by Herman Boerhaave in the early 1700s, long before the formal development of thermodynamics.

Atomism

The philosophical underpinnings of atomism are fundamental to the modern relationship between thermodynamics and statistical mechanics. Ancient thinkers, including Leucippus, Democritus, and later the Epicureans, laid the groundwork for the eventual atomic theory through their atomic postulates. However, it is crucial to note that for centuries, the atomic theory remained largely a product of philosophical speculation and scientific intuition, awaiting experimental validation in the 20th century.

17th Century

Early Thermometers

The early 17th century saw pioneering efforts in quantifying temperature. European scientists like Cornelius Drebbel, Robert Fludd, Galileo Galilei, and Santorio Santorio developed rudimentary air thermometers, or thermoscopes, capable of indicating relative degrees of "coldness" or "hotness". These early instruments may have been influenced by earlier devices described by Philo of Byzantium and Hero of Alexandria, which demonstrated the expansion and contraction of air.

"Heat is Motion" (Francis Bacon)

The notion that heat is intrinsically linked to motion can be traced back to antiquity, but it was the English philosopher and scientist Francis Bacon who, in his 1620 treatise Novum Organum, articulated this idea with remarkable prescience. Bacon surmised, "Heat itself, its essence and quiddity is motion and nothing else," elaborating further that this motion was not of the macroscopic body as a whole, but "of the small particles of the body." This insight foreshadowed the development of the kinetic theory of gases by centuries.

Precursor to Work (René Descartes)

The foundational concept of work in physics was subtly introduced by René Descartes. In a 1637 letter to Christiaan Huygens, Descartes wrote, "Lifting 100 lb one foot twice over is the same as lifting 200 lb one foot, or 100 lb two feet." This clearly articulated the idea that work is a product of force and distance. Similarly, in 1686, Gottfried Leibniz expressed a similar principle: "The same force [in modern terms, work] is necessary to raise body A of 1 pound (libra) to a height of 4 yards (ulnae), as is necessary to raise body B of 4 pounds to a height of 1 yard."

Quantity of Motion

In his 1644 work Principles of Philosophy (Principia Philosophiae), Descartes defined the "quantity of motion" as the product of size and speed. He further posited that this quantity is conserved, stating, "God created matter, along with its motion ... merely by letting things run their course, he preserves the same amount of motion ... as he put there in the beginning." This concept of conservation of motion predates the formal enunciation of the conservation of energy.

Boyle's Law

The Irish physicist and chemist Robert Boyle, in collaboration with the English scientist Robert Hooke, constructed an air pump in 1656. Through experiments with this apparatus, Boyle and Hooke observed the inverse relationship between the pressure and volume of a gas, famously known as Boyle's law (PV = constant). At this time, air was conceptualized as a collection of static particles, rather than the dynamic system of molecules envisioned by later kinetic theories. Consequently, Boyle's 1660 publication described this relationship as a mechanical property of the "air spring." The subsequent invention of the thermometer, which allowed for the quantification of temperature, paved the way for Gay-Lussac to formulate his law, ultimately leading to the ideal gas law.

Gas laws in brief:

Steam Digester

Denis Papin, a colleague of Boyle, constructed a "bone digester" in 1679. This device was a sealed vessel designed to generate high pressure by confining steam. Papin later incorporated a steam release valve to prevent explosions, and observing its rhythmic action, conceived of the piston and cylinder engine, though he never fully developed the design. It was Thomas Newcomen who, in 1697, significantly improved upon Thomas Savery's earlier "fire engine" by incorporating a piston mechanism based on Papin's ideas. This innovation transformed the steam engine into a practical device for mechanical work, beyond simple pumping, and is often considered the first true steam engine. The 1698 Savery Engine, built by Thomas Savery, was the world's first commercially important steam engine.

Heat Transfer (Halley and Newton)

The fundamental phenomenon of heat conduction is readily observable in everyday life. The principle that warm air rises, and its significance in meteorology, was first recognized by Edmond Halley in 1686. In 1701, Sir Isaac Newton published his law of cooling.

18th Century

Phlogiston Theory

Emerging in the 17th century during the era of alchemy, the phlogiston theory proposed that combustible materials contained a substance called "phlogiston," which was released during burning and metals during rusting. Its eventual replacement by the caloric theory in the 18th century marked a significant transition from alchemy to modern chemistry.

The world's first ice-calorimeter, utilized by Antoine Lavoisier and Pierre-Simon Laplace during the winter of 1782–83, was instrumental in determining the heat evolved during various chemical changes. These calculations were based on Joseph Black's prior discovery of latent heat, laying the foundation for thermochemistry.

Limit to the "Degree of Cold"

In 1702, Guillaume Amontons introduced the concept of absolute zero, a theoretical temperature at which molecular motion ceases, based on observations of gases.

Kinetic Theory (18th Century)

An early, prescient articulation of the microscopic and kinetic nature of matter and heat can be found in the work of Mikhail Lomonosov. He wrote, "Movement should not be denied based on the fact it is not seen. ... leaves of trees move when rustled by a wind, despite it being unobservable from large distances. Just as in this case motion ... remains hidden in warm bodies due to the extremely small sizes of the moving particles."

Around the same period, Daniel Bernoulli published his Hydrodynamics (1738), proposing an equation for gas pressure derived from the collisions of atoms with container walls. He demonstrated that this pressure is directly proportional to the average kinetic energy of the gas molecules per unit volume. Bernoulli's work, however, had limited impact on the prevailing caloric theory. His ideas did connect with Gottfried Leibniz's vis viva principle, an early precursor to the conservation of energy, and these two concepts would remain closely linked throughout the history of thermodynamics.

Thermochemistry and Steam Engines

The concept of heat capacity—the amount of heat required to raise the temperature of a substance—was first identified and investigated by the Scottish chemist Joseph Black in the 1750s. Although heat is now understood as the transfer of disordered thermal energy, and a manifestation of a system's internal energy, the term "heat capacity" persists.

The steam engine, a pivotal invention of the Industrial Revolution, drove significant advancements in understanding energy. Prior to the Savery engine in 1698, horses were the primary power source for mine drainage. The subsequent development of engines by Newcomen and later Watt revolutionized industry. However, these early engines were notoriously inefficient, converting less than 2% of fuel into useful work, highlighting the urgent need for a deeper scientific understanding of engine dynamics.

Caloric Theory

During the mid-to-late 18th century, heat was conceptualized as a fluid called caloric. This theory, much like phlogiston, posited that caloric flowed from hotter to cooler bodies. However, the growing explanatory power of the kinetic theory gradually undermined the caloric theory. Even by 1850, William Thomson was still attempting to reconcile James Joule's findings within a caloric framework. By the close of the 19th century, the caloric theory was largely defunct.

Calorimetry

Joseph Black and Antoine Lavoisier made crucial contributions to the precise measurement of heat changes, establishing the field of thermochemistry. The practical demands of improving steam engines spurred research into calorimetry and the efficient use of coal. Lavoisier's pioneering quantitative studies of heat changes in chemical reactions, using an ice calorimeter inspired by Black's work on latent heat, marked a significant step forward.

Thermal Conduction and Thermal Radiation

In 1777, Carl Wilhelm Scheele differentiated between heat transfer via thermal radiation and that occurring through convection and conduction. Early in the 19th century, it was widely believed that all materials possessed similar thermal conductivity, with perceived differences attributed to variations in heat capacity. However, observations in the nascent field of electricity, which clearly distinguished conductors from insulators, suggested otherwise. Jan Ingen-Housz and Benjamin Thompson conducted early measurements in the 1780s and 1790s.

In 1791, Pierre Prévost proposed that all objects, regardless of temperature, emit heat radiation. This was followed by Sir John Leslie's 1804 observation that matte black surfaces radiate heat more effectively than polished ones, underscoring the importance of black-body radiation.

Heat and Friction (Rumford)

The caloric theory faced its first significant experimental challenge in 1798 with the work of Benjamin Thompson, later known as Count Rumford. While overseeing the boring of cast iron cannons, Thompson observed the continuous generation of heat, which he attributed to friction, not to a stored substance. This groundbreaking research was among the first to cast serious doubt on the caloric theory, suggesting that heat might be a manifestation of motion, though a direct link to the vis viva principle was not yet established.

Early 19th Century

Modern Thermodynamics (Carnot)

Despite the inefficiencies of early steam engines, they captivated the attention of leading scientists. Among them was Sadi Carnot, often hailed as the "father of thermodynamics." In 1824, he published Reflections on the Motive Power of Fire (Réflexions sur la puissance motrice du feu), a seminal work that explored the relationship between heat, power, and engine efficiency. This publication is widely regarded as the genesis of thermodynamics as a modern scientific discipline. The term "thermodynamics" itself was coined later, in 1854, by William Thomson (Lord Kelvin).

Carnot defined "motive power" as the useful effect a motor can produce, introducing a concept of "work" as a weight lifted through a height. His desire to quantify this useful effect in relation to work became a central theme in thermodynamics. Although still operating within the framework of the caloric theory, Carnot astutely suggested that some caloric is inevitably lost in any real process, hinting at the concept of irreversibility.

Reflection, Refraction, and Polarization of Radiant Heat

In 1831, Macedonio Melloni provided experimental evidence that radiant heat exhibits properties of reflection, refraction, and polarisation, akin to light. This further solidified the wave-like nature of heat radiation.

Kinetic Theory (Early 19th Century)

Independent contributions to the kinetic theory emerged in the early 19th century. In 1820, John Herapath formulated a kinetic theory, incorrectly linking temperature to momentum rather than kinetic energy. His work failed to gain acceptance, even from sympathetic scientists like Humphry Davy. Later, in 1843, John James Waterston presented a more accurate, yet equally overlooked, account of the kinetic theory, which also failed to pass peer review. Significant progress in this field would only resume in the mid-19th century with the work of Rudolf Clausius, James Clerk Maxwell, and Ludwig Boltzmann.

Mechanical Equivalent of Heat

The work of James Joule from 1843 onwards provided crucial experimental validation for the equivalence of heat and work, placing thermodynamics on a firm footing. In 1843, Joule experimentally determined the mechanical equivalent of heat. His most famous experiment, conducted in 1845, involved using a falling weight to agitate water, allowing him to estimate this equivalent. This research was pivotal in establishing the principle of conservation of energy and explaining how heat can perform work.

Absolute Zero and the Kelvin Scale

Lord Kelvin (William Thomson) generalized the concept of absolute zero in 1848, proposing a thermodynamic temperature scale independent of the properties of any specific substance.

Late 19th Century

Entropy and the Second Law of Thermodynamics

By March 1851, grappling with Joule's findings, Lord Kelvin began to theorize about an unavoidable loss of useful heat in all processes. Hermann von Helmholtz further amplified this concept in 1854, introducing the chilling notion of the heat death of the universe.

In 1854, William John Macquorn Rankine introduced a "thermodynamic function" into his calculations, which was later recognized as being equivalent to the concept of entropy formulated by Rudolf Clausius.

In 1865, Clausius coined the term "entropy" to describe the transformation of heat into waste. He used this concept to formulate his classic statement of the second law of thermodynamics that same year.

Statistical Thermodynamics

Temperature is Average Kinetic Energy of Molecules

In a groundbreaking 1857 paper, "On the nature of the motion called heat," Clausius clearly posited that heat is fundamentally the average kinetic energy of molecules.

Maxwell–Boltzmann Distribution

Clausius's insight sparked the interest of James Clerk Maxwell, who, in 1859, derived the distribution of molecular speeds, now known as the Maxwell–Boltzmann distribution. Ludwig Boltzmann later generalized this to include external fields. In collaboration with Clausius, Maxwell, in 1871, established statistical mechanics as a new branch of thermodynamics, focusing on the analysis of systems at thermodynamic equilibrium by examining their average properties like temperature, pressure, and volume.

Degrees of Freedom

Ludwig Boltzmann made profound contributions to kinetic theory, introducing concepts such as the association of kinetic energy with molecular degrees of freedom. His famous Boltzmann equation remains a critical tool for studying transport phenomena in gases and metals. Boltzmann also introduced the concept of thermodynamic probability, linking the logarithm of this probability (representing the number of microstates for a given macrostate) directly to entropy.

Definition of Entropy

In 1875, Boltzmann provided a precise mathematical definition of entropy (S) in relation to molecular motion: S=klog⁡WS = k \log W, where WW is the number of possible microstates and kk is the Boltzmann constant.

Gibbs Free Energy

In 1876, the American chemical engineer Willard Gibbs published his seminal paper, "On the Equilibrium of Heterogeneous Substances." Within this work, he introduced the concept of Gibbs free energy, providing a measure of the "useful work" obtainable from reacting systems.

Enthalpy

Gibbs also originated the concept of enthalpy, referring to it as "a heat function for constant pressure." The term "enthalpy" was coined later by Heike Kamerlingh Onnes, derived from the Greek word meaning "to warm."

Stefan–Boltzmann Law

James Clerk Maxwell's 1862 realization that light and radiant heat were both forms of electromagnetic wave initiated the quantitative study 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, formulating the Stefan–Boltzmann law. Ludwig Boltzmann later derived this law theoretically in 1884.

20th Century

Quantum Thermodynamics

In 1900, Max Planck developed a formula for black-body radiation that required the introduction of a new fundamental constant, the Planck constant. This formula suggested that energy is quantized, occurring in discrete multiples of frequency times the constant, a revolutionary concept that resolved a theoretical divergence and laid the foundation for quantum mechanics.

Third Law of Thermodynamics

Walther Nernst formally stated the third law of thermodynamics in 1906.

Building upon these foundational principles, scientists like Lars Onsager, Erwin Schrödinger, and Ilya Prigogine extended the concepts of thermodynamics into numerous branches of modern science.

Branches of Thermodynamics

Thermodynamics has evolved into a multifaceted field with numerous specialized branches, each arising at different historical junctures:

Furthermore, thermodynamic principles have been applied to other fields, such as thermoeconomics (c. 1970s).