Timeline of Thermodynamics
The science of heat and temperature, from Galileo's air thermoscope of the 1590s through Carnot, the laws of thermodynamics and statistical mechanics to record cold near absolute zero in 2021.
- Category
- Natural Sciences
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- physics
- Events
- 29 events c. 1593 – 2021
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- by claude-opus-5-5
c. 1593: Galileo builds an air thermoscope
Galileo Galilei made an air-filled glass bulb on a tube dipped in water; the water rose as the air cooled and fell as it warmed, showing but not measuring changes in heat. Accounts date it from the early 1590s to about 1603, and credit is contested: Santorio Santorio described one in print in 1612 and pictured ones with scales in 1625, Cornelis Drebbel made similar ones, and Philo of Byzantium described the principle in antiquity.
Wikipedia1724: Fahrenheit publishes his temperature scale
Daniel Gabriel Fahrenheit, an Amsterdam instrument maker credited with the first successful mercury-in-glass thermometers, gave his fixed points in a Royal Society paper: 0 for a mixture of ice, water and ammonium chloride, 32 for melting ice and 96 for body temperature. Sealed thermometers made in Florence from about 1654 agreed with one another, but on a local scale; Fahrenheit's popular instruments spread his scale widely.
Wikipedia1742: Celsius proposes a 100-degree scale
Anders Celsius, professor of astronomy at Uppsala, proposed a scale with 0 at the boiling point of water and 100 at the melting point of ice, after showing that the melting point is essentially unaffected by air pressure and measuring how the boiling point depends on it. Jean-Pierre Christin in Lyon in 1743, possibly independently, and Carl Linnaeus in 1744 turned it the other way up.
Wikipediac. 1761: Black discovers latent heat
Joseph Black at the University of Glasgow found that melting ice and boiling water absorb much heat without warming, heat he called "latent"; with his finding that substances need different amounts of heat to warm equally, later called specific heat, this separated heat from temperature. He read it to a Glasgow society in 1762 but never published it; Johan Carl Wilcke in Sweden found latent heat independently and published in 1772.
Wikipedia1769: Watt patents the separate condenser
Repairing a model of the atmospheric engine that Thomas Newcomen had introduced in 1712 to pump water from mines, James Watt saw that it wasted much of its heat by cooling and reheating its cylinder at every stroke. His separate condenser, conceived in 1765, kept the cylinder hot and sharply cut fuel use. The efficiency of such engines became the practical question behind thermodynamics.
Wikipedia1798: Rumford challenges caloric theory with cannon boring
Benjamin Thompson, Count Rumford, reported in the Royal Society's Philosophical Transactions that boring a cannon barrel at the Munich arsenal could boil water in about two and a half hours and seemed to yield heat without limit. He argued that heat was a form of motion, not the conserved fluid "caloric"; most scientists adapted caloric theory instead, and he did not measure how much work produced how much heat.
Wikipedia1824: Carnot publishes a theory of heat engines
In "Reflections on the Motive Power of Fire", the French engineer Sadi Carnot argued that the maximum work obtainable from heat, reached by an ideal reversible engine, depends only on the temperatures of the hot and cold bodies, not on the working substance. Reasoning within caloric theory, he likened heat falling from hot to cold to water driving a mill wheel; restated by Émile Clapeyron in 1834, it outlived caloric and grounded the second law.
Wikipedia1842–1850: Mayer and Joule equate heat with work
Julius Robert von Mayer, a German physician, argued in 1842 that heat and mechanical work are interchangeable and calculated their exchange rate. James Prescott Joule in England measured it independently from 1843, notably with a paddle wheel turned by falling weights, and published a refined value in 1850; Ludwig Colding in Denmark reached similar conclusions. The "mechanical equivalent of heat" undermined caloric theory and set off a priority dispute.
Wikipedia1847: Helmholtz generalizes the conservation of energy
Starting from the impossibility of perpetual motion, Hermann von Helmholtz argued in "On the Conservation of Force" that mechanical work, heat, light, electricity and magnetism are forms of one conserved quantity, now called energy. Drawing on Joule, Carnot and Clapeyron, the essay is credited as the first fully general statement of the principle; William Rankine named it the conservation of energy in 1853.
Wikipedia1848: Thomson proposes an absolute temperature scale
William Thomson, later Lord Kelvin, proposed defining temperature through Carnot's theory of heat engines, so that the scale would not depend on the properties of any particular substance. His first version placed absolute zero at minus infinity, though a footnote derived −273 °C for absolute zero from the expansion of gases; in 1854 he and James Joule recast the definition into the scale now measured in kelvins.
Wikipedia1850: Clausius reconciles Carnot with energy conservation
In "On the Moving Force of Heat", Rudolf Clausius kept Carnot's result but dropped the caloric assumption that heat is conserved: an engine turns part of the heat it takes in into work and passes the rest to a colder body. The paper gave the first explicit statement of the first law and a first form of the second, resting on heat's tendency to flow from hot to cold; William Thomson (Lord Kelvin) stated an equivalent second law in 1851.
Wikipedia1860: Maxwell derives the distribution of molecular speeds
In "Illustrations of the Dynamical Theory of Gases", read to the British Association in 1859, James Clerk Maxwell gave the fraction of a gas's molecules moving at each speed at a given temperature, treating molecular motion statistically rather than following individual molecules. Generalized by Ludwig Boltzmann as the Maxwell–Boltzmann distribution, it became a foundation of kinetic theory and statistical mechanics.
Wikipedia1865: Clausius coins the term "entropy"
Rudolf Clausius named "entropy", from the Greek for transformation and chosen to resemble "energy", the quantity whose change equals the heat a body takes in reversibly divided by its absolute temperature; he had used the idea since 1854 as an "equivalence-value". His paper closed by summarizing the first and second laws: "The energy of the universe is constant. The entropy of the universe tends to a maximum."
Wikipedia1875–1878: Gibbs extends thermodynamics to chemical systems
In "On the Equilibrium of Heterogeneous Substances", a memoir of about 300 pages in the Transactions of the Connecticut Academy of Arts and Sciences, Josiah Willard Gibbs of Yale applied the two laws to mixtures and coexisting phases, introducing the chemical potential and the phase rule. Little read at first, it reached chemists widely through Wilhelm Ostwald's German translation of 1892 and Henry Le Chatelier's partial French one of 1899.
Wikipedia1877: Boltzmann links entropy to probability
Answering Johann Josef Loschmidt's objection to his 1872 H-theorem, that reversible molecular motions cannot produce one-way change, Ludwig Boltzmann tied a gas's entropy to the number of molecular arrangements consistent with its observed state: entropy rises because higher-entropy states are overwhelmingly more probable. Max Planck later wrote this as S = k log W, introducing the constant k in 1900–1901; it is carved on Boltzmann's tombstone.
Wikipedia1877: Cailletet and Pictet liquefy oxygen
Raoul Pictet in Geneva, cooling with evaporating sulfur dioxide and carbon dioxide, and Louis Paul Cailletet in France, by suddenly expanding compressed oxygen, independently liquefied oxygen, a "permanent gas", for an instant; Cailletet saw only a dense fog. Both results were read to the French Academy of Sciences on December 24, and it credited Cailletet, whose sealed letter had been deposited on December 3.
Wikipedia1898: Dewar liquefies hydrogen
James Dewar was the first to collect liquid hydrogen, at about 20 kelvin, working at the Royal Institution in London with a regenerative refrigerating machine that cooled a high-pressure jet of the gas by the Joule–Thomson effect, and solidified hydrogen in 1899. His vacuum flask of about 1892, built to hold such liquids, later became the household Thermos.
Wikipedia1902: Gibbs publishes "Elementary Principles in Statistical Mechanics"
Shortly before his death, Josiah Willard Gibbs showed how the laws of thermodynamics follow from classical mechanics by averaging over "ensembles", imagined collections of copies of a system in every microscopic state compatible with what is observed. The book gave the field, a name Gibbs had coined in 1884, its general form, and its methods carried over to quantum mechanics with little change.
Wikipedia1905: Einstein explains Brownian motion
Albert Einstein showed that the jittering of microscopic particles suspended in a liquid, observed by the botanist Robert Brown in 1827, should result from impacts of the liquid's molecules, and predicted how far such particles wander on average over time. Marian Smoluchowski independently reached a similar result in 1906, and Jean Perrin's experiments from 1908 confirmed it, convincing skeptics such as Wilhelm Ostwald that atoms are real.
Wikipedia1906–1912: Nernst formulates the third law
Walther Nernst's heat theorem, formally announced in December 1905, held in effect that entropy changes in reactions among solids and liquids vanish as absolute zero is approached, letting chemists calculate equilibria from heat measurements. Max Planck extended it in 1911 to the entropy of pure crystals, and by 1912 Nernst added that absolute zero cannot be reached in a finite number of steps; he won the 1920 Nobel Prize in Chemistry.
Wikipedia1908: Kamerlingh Onnes liquefies helium
Heike Kamerlingh Onnes at Leiden University liquefied helium, the last gas to resist liquefaction, at 4.2 kelvin, and by pumping on the liquid reached about 1.7 K, the lowest temperature then recorded on Earth. Using liquid helium, he and his assistant Gilles Holst found in 1911 that mercury loses all electrical resistance when cold enough, the discovery of superconductivity; he received the 1913 Nobel Prize in Physics.
Wikipedia1931: Onsager finds reciprocal relations for irreversible processes
Lars Onsager, a Norwegian-born chemist at Brown University, showed that near equilibrium, coupled irreversible processes such as heat conduction, diffusion and electric current influence one another symmetrically, a consequence of the time-reversibility of molecular motion. Long overlooked, his reciprocal relations became a foundation of non-equilibrium thermodynamics and earned him the 1968 Nobel Prize in Chemistry.
Wikipedia1933: Giauque demonstrates magnetic cooling
William Giauque and D. P. MacDougall at the University of California, Berkeley, magnetized a paramagnetic salt cooled by liquid helium, insulated it and switched off the field, reaching 0.25 K; pumping on liquid helium had reached only 0.71 K. A Leiden group under Wander de Haas did the same independently within weeks. Giauque, who proposed the method in 1927 as Peter Debye had in 1926, won the 1949 Nobel Prize in Chemistry.
Wikipedia1938: Superfluidity discovered in liquid helium
Pyotr Kapitsa in Moscow and, independently, John Allen and Don Misener in Cambridge reported in "Nature" that liquid helium cooled below 2.17 kelvin flows through narrow channels with almost no viscosity. Fritz London soon proposed that this superfluidity arises from Bose–Einstein condensation, and Lev Landau's theory of 1941 explained much of it; Kapitsa received the 1978 Nobel Prize in Physics.
Wikipedia1944: Onsager solves the two-dimensional Ising model
Lars Onsager calculated exactly the free energy of the two-dimensional Ising model, a lattice of interacting magnetic spins, showing how a sharp phase transition arises from short-range interactions, with critical behavior unlike that of approximate mean-field theories. Explaining such behavior led to Kenneth Wilson's renormalization-group theory of 1971, recognized with the 1982 Nobel Prize in Physics.
Wikipedia1961: Landauer ties information erasure to heat
Rolf Landauer argued that erasing one bit of information must release at least kT ln 2 of heat (k is the Boltzmann constant, T the temperature), tying computation to the second law. In 1982 Charles Bennett used it to argue that the molecule-sorting "demon" James Clerk Maxwell imagined in 1867 cannot beat the second law, because it must eventually erase its memory; a 2012 experiment with one colloidal particle measured heat approaching the limit.
Wikipedia1995: Bose–Einstein condensates created in atomic gases
Eric Cornell and Carl Wieman in Boulder, Colorado, cooled rubidium-87 atoms with lasers and evaporation until, below about 170 billionths of a kelvin, many collected in the lowest quantum state, as Albert Einstein had predicted in 1924–1925 from Satyendra Nath Bose's statistics of light. Wolfgang Ketterle at the Massachusetts Institute of Technology condensed sodium about four months later; the three shared the 2001 Nobel Prize in Physics.
Wikipedia2019: Kelvin redefined by fixing the Boltzmann constant
In the revision of the International System of Units (SI) that took effect on May 20, the kelvin was redefined by fixing the Boltzmann constant, which links temperature to energy, at an exact value. Since 1954 the unit had rested on the triple point of water, set at 273.16 K, which now became a measured quantity; the change made the definition independent of any substance and better suited to temperatures far from that point.
Wikipedia2021: Physicists report a 38-picokelvin effective temperature
In the University of Bremen's drop tower, a freely falling Bose–Einstein condensate of about 100,000 rubidium atoms, collimated by a magnetic lens timed to the cloud's own oscillation, expanded so slowly that its internal kinetic energy corresponded to 38 trillionths of a kelvin. Measured in August 2018, it is a record effective temperature for the atoms' motion, not an equilibrium temperature; absolute zero remains unattainable.
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