Thermodynamics Explained: Heat, Energy, Entropy, and the Laws of Physics
Heat, temperature, and energy transfer
Thermodynamics is the study of heat, energy, and how they relate to work. Its laws govern everything from the efficiency of car engines to the direction of time itself. The second law — that entropy (disorder) in a closed system always increases — is one of the most profound and far-reaching principles in all of science. It explains why ice melts and doesn't spontaneously re-freeze, why heat flows from hot to cold and never in reverse, and why the universe as a whole is moving from order toward chaos.
Physics: Joseph Fourier
Joseph Fourier (1768) Jean-Baptiste Joseph Fourier (; French: [ʒɑ̃ batist ʒozɛf fuʁje]; 21 March 1768 – 16 May 1830) was a French mathematician and physicist born in Auxerre, Burgundy and best known for initiating the investigation of Fourier series, which eventually developed into Fourier analysis and harmonic analysis, and their applications to problems of heat transfer and vibrations.
Read commentary →Physics: Carnot founds thermodynamic cycle analysis
1824: Carnot founds thermodynamic cycle analysis Nicolas Léonard Sadi Carnot (French: [nikɔla leɔnaʁ sadi kaʁno]; 1 June 1796 – 24 August 1832) was a French military engineer and physicist.
Read commentary →Physics: Wave equation
Wave equation Form: c = λν The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength.
Read commentary →Physics: Infrared
Infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves.
Read commentary →Physics: James Clerk Maxwell
James Clerk Maxwell (1831) James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish physicist and mathematician who was responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and light as different manifestations of the same phenomenon.
Read commentary →Physics: Gamma ray
Gamma ray A gamma ray, also known as gamma radiation (symbol γ), is a penetrating form of electromagnetic radiation arising from high-energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares.
Read commentary →Physics: X-ray
X-ray An X-ray is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays.
Read commentary →Physics: Becquerel discovers natural radioactivity
1896: Becquerel discovers natural radioactivity Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation.
Read commentary →Physics: James Prescott Joule
James Prescott Joule (1818) James Prescott Joule (; 24 December 1818 – 11 October 1889) was an English physicist.
Read commentary →Physics: Carl Anderson
Carl Anderson (1905) Carlton Earl "Carl" Anderson (February 27, 1945 – February 23, 2004) was an American singer, film and theater actor best known for his portrayal of Judas Iscariot in the Broadway and film versions of the rock opera Jesus Christ Superstar by Andrew Lloyd Webber and Tim Rice.
Read commentary →Physics: Pulsar
Pulsar A pulsar (pulsating star, on the model of quasar) is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles.
Read commentary →Physics: Joule's paddle wheel experiment
Joule's paddle wheel experiment By: James Joule (1843) James Prescott Joule (; 24 December 1818 – 11 October 1889) was an English physicist.
Read commentary →Physics: Impedance of free space
Impedance of free space Z₀ = 376.73 Ω In physics, electromagnetic radiation (EMR) or an electromagnetic wave (EMW) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space.
Read commentary →Physics: Absolute zero
Absolute zero Absolute zero is the lowest theoretically possible temperature, a state at which a system's internal energy, and in ideal cases entropy, reach their minimum values.
Read commentary →Physics: Electromagnetic spectrum
Electromagnetic spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength.
Read commentary →Physics: Ultraviolet
Ultraviolet Ultraviolet radiation (UV; sometimes called ultraviolet light) is electromagnetic radiation of wavelengths of 100–400 nanometers, shorter than that of visible light, but longer than X-rays.
Read commentary →Physics: Rontgen discovers X-rays
1895: Rontgen discovers X-rays An X-ray is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays.
Read commentary →Physics: 1903 Nobel Prize in Physics
1903 Nobel Prize in Physics Awarded to: Antoine Henri Becquerel, Pierre Curie, Marie Curie, née Skłodowska In recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity / in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel.
Read commentary →Physics: Power (electricity)
Power (electricity) Form: P = IV Electric power is the rate of transfer of electrical energy within a circuit.
Read commentary →Physics: Wu experiment
Wu experiment By: Chien-Shiung Wu (1956) The Wu experiment was a particle and nuclear physics experiment conducted in 1956 by the Chinese-American physicist Chien-Shiung Wu in collaboration with the Low Temperature Group of the US National Bureau of Standards.
Read commentary →Physics: Charles-Augustin de Coulomb
Charles-Augustin de Coulomb (1736) Charles-Augustin de Coulomb ( KOO-lom, -lohm, koo-LOM, -LOHM; French: [kulɔ̃]; 14 June 1736 – 23 August 1806) was a French officer, engineer, and physicist.
Read commentary →Physics: Planck temperature
Planck temperature Tp = 1.417×10³² K In particle physics and physical cosmology, Planck units are a system of units of measurement defined exclusively in terms of four universal physical constants: c, G, ħ, and kB.
Read commentary →Physics: Radioactivity
Radioactivity Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation.
Read commentary →Physics: 1948 Nobel Prize in Physics
1948 Nobel Prize in Physics Awarded to: Patrick Maynard Stuart Blackett His development of the Wilson cloud chamber method, and his discoveries therewith in the fields of nuclear physics and cosmic radiation.
Read commentary →Physics: Microwave
Microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves.
Read commentary →Physics: Frequency-wavelength relation
Frequency-wavelength relation Form: ν = c/λ The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength.
Read commentary →Physics: Avogadro constant
Avogadro constant Nₐ = 6.022×10²³ mol⁻¹ In chemistry, the Avogadro constant, commonly denoted NA, is a conversion constant or ratio between an amount of substance and the number of particles that it contains.
Read commentary →Physics: Root mean square speed
Root mean square speed Form: v = √(kT/m) In physics (in particular in statistical mechanics), the Maxwell–Boltzmann distribution, or Maxwell(ian) distribution, is a particular probability distribution named after James Clerk Maxwell and Ludwig Boltzmann.
Read commentary →Physics: Boltzmann constant
Boltzmann constant k = 1.381×10⁻²³ J/K The Boltzmann constant (kB or k) is the proportionality factor that relates the average relative thermal energy of particles in a gas with the thermodynamic temperature of the gas.
Read commentary →Physics: Boyle's law
Boyle's law Boyle's law, also referred to as the Boyle–Mariotte law or Mariotte's law (especially in France), is an empirical gas law that describes the relationship between pressure and volume of a confined gas.
Read commentary →Physics: Charles Townes
Charles Townes (1915) Charles Hard Townes (July 28, 1915 – January 27, 2015) was an American physicist.
Read commentary →Physics: Fourier's law of heat conduction
Fourier's law of heat conduction Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact.
Read commentary →Physics: Second law of thermodynamics
Second law of thermodynamics The second law of thermodynamics is a physical law based on universal empirical observation concerning heat and energy interconversions.
Read commentary →Physics: Boyle's law
Boyle's law Form: pV = constant Boyle's law, also referred to as the Boyle–Mariotte law or Mariotte's law (especially in France), is an empirical gas law that describes the relationship between pressure and volume of a confined gas.
Read commentary →Physics: Gay-Lussac's law
Gay-Lussac's law Gay-Lussac's law usually refers to Joseph-Louis Gay-Lussac's law of combining volumes of gases, discovered in 1808 and published in 1809.
Read commentary →Physics: Gas constant
Gas constant R = 8.314 J/(mol·K) The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol R or R.
Read commentary →Physics: Third law of thermodynamics
Third law of thermodynamics The third law of thermodynamics states that the entropy of a closed system at thermodynamic equilibrium approaches a constant value when its temperature approaches absolute zero.
Read commentary →Physics: 1917 Nobel Prize in Physics
1917 Nobel Prize in Physics Awarded to: Charles Glover Barkla His discovery of the characteristic Röntgen radiation of the elements.
Read commentary →Physics: Wien's displacement law
Wien's displacement law In physics, Wien's displacement law states that the black-body radiation curve for different temperatures will peak at different wavelengths that are inversely proportional to the temperature.
Read commentary →Physics: 1902 Nobel Prize in Physics
1902 Nobel Prize in Physics Awarded to: Hendrik Antoon Lorentz, Pieter Zeeman In recognition of the extraordinary service they rendered by their researches into the influence of magnetism upon radiation phenomena.
Read commentary →Physics: 1961 Nobel Prize in Physics
1961 Nobel Prize in Physics Awarded to: Robert Hofstadter, Rudolf Ludwig Mössbauer His pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons / for his researches concerning the resonance absorption of gamma radiation and his discovery in this connection of the effect which bears his name.
Read commentary →Physics: Ludwig Boltzmann
Ludwig Boltzmann (1844) Ludwig Eduard Boltzmann ( BAWLTS-mahn or BOHLTS-muhn; German: [ˈluːtvɪç ˈeːduaʁt ˈbɔltsman]; 20 February 1844 – 5 September 1906) was an Austrian mathematician and theoretical physicist.
Read commentary →Physics: Radio wave
Radio wave Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths greater than 1 millimeter (3⁄64 inch), about the diameter of a grain of rice.
Read commentary →Physics: Big Bang
Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature.
Read commentary →Physics: Charles's law
Charles's law Charles's law (also known as the law of volumes) is an experimental gas law that describes how gases tend to expand when heated.
Read commentary →Physics: 1922 Nobel Prize in Physics
1922 Nobel Prize in Physics Awarded to: Niels Henrik David Bohr His services in the investigation of the structure of atoms and of the radiation emanating from them.
Read commentary →Physics: 1936 Nobel Prize in Physics
1936 Nobel Prize in Physics Awarded to: Victor Franz Hess, Carl David Anderson His discovery of cosmic radiation / for his discovery of the positron.
Read commentary →Physics: Telescope
Telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.
Read commentary →Physics: Power (physics)
Power (physics) Power is the amount of energy transferred or converted per unit time.
Read commentary →Physics: 2006 Nobel Prize in Physics
2006 Nobel Prize in Physics Awarded to: John C. Mather, George F. Smoot Their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.
Read commentary →Physics: Power
Power Form: dE/dt = P Power is the amount of energy transferred or converted per unit time.
Read commentary →Physics: Photon
Photon A photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light') is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.
Read commentary →Physics: Cosmic microwave background discovered
1964: Cosmic microwave background discovered The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe.
Read commentary →Physics: Boyle's law formalizes pressure-volume relationship
1662: Boyle's law formalizes pressure-volume relationship Boyle's law, also referred to as the Boyle–Mariotte law or Mariotte's law (especially in France), is an empirical gas law that describes the relationship between pressure and volume of a confined gas.
Read commentary →Physics: 1913 Nobel Prize in Physics
1913 Nobel Prize in Physics Awarded to: Heike Kamerlingh Onnes His investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium.
Read commentary →Physics: Photoelectric effect
Photoelectric effect The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light.
Read commentary →Physics: Temperature
Temperature In classical thermodynamics and kinetic theory, temperature reflects the average kinetic energy of the particles in a system, providing a quantitative measure of how energy is distributed among microscopic degrees of freedom.
Read commentary →Physics: 1938 Nobel Prize in Physics
1938 Nobel Prize in Physics Awarded to: Enrico Fermi His demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons.
Read commentary →Physics: Bose–Einstein condensate
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter that is typically formed when a gas of bosons at very low densities is cooled to temperatures very close to absolute zero, i.
Read commentary →Physics: Bremsstrahlung
Bremsstrahlung In particle physics, bremsstrahlung (; German: [ˈbʁɛms.
Read commentary →Physics: Heat
Heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary.
Read commentary →Physics: Amedeo Avogadro
Amedeo Avogadro (1776) Lorenzo Romano Amedeo Carlo Avogadro, Count of Quaregna and Cerreto (, also US: , Italian: [ameˈdɛːo avoˈɡaːdro]; 9 August 1776 – 9 July 1856) was an Italian scientist, most noted for his contribution to molecular theory now known as Avogadro's law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of m
Read commentary →Physics: Dark matter
Dark matter In astronomy and cosmology, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation.
Read commentary →Physics: Heat capacity
Heat capacity Form: Q = mcΔT Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat that must be supplied to an object to produce a unit change in its temperature.
Read commentary →Physics: Conductance quantum
Conductance quantum G₀ = 7.748×10⁻⁵ S The quantum Hall effect (or integer quantum Hall effect) is a quantized version of the Hall effect which is observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall resistance Rxy exhibits steps that take on the quantized values R x
Read commentary →Physics: Photoelectric effect
Photoelectric effect The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light.
Read commentary →Physics: 1911 Nobel Prize in Physics
1911 Nobel Prize in Physics Awarded to: Wilhelm Wien His discoveries regarding the laws governing the radiation of heat.
Read commentary →Physics: Discovery of cosmic microwave background radiation
Discovery of cosmic microwave background radiation By: Penzias and Wilson (1964) The discovery of cosmic microwave background radiation constitutes a major development in modern physical cosmology.
Read commentary →Physics: Einstein explains photoelectric effect
1905: Einstein explains photoelectric effect The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light.
Read commentary →Physics: Laws of thermodynamics
Laws of thermodynamics The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium.
Read commentary →Physics: First law of thermodynamics
First law of thermodynamics The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes.
Read commentary →Physics: Stefan-Boltzmann constant
Stefan-Boltzmann constant σ = 5.670×10⁻⁸ W/(m²·K⁴) The Stefan–Boltzmann law, also known as Stefan's law, describes the intensity of the thermal radiation emitted by matter in terms of that matter's temperature.
Read commentary →Physics: Wilhelm Conrad Rontgen
Wilhelm Conrad Rontgen (1845) Wilhelm Conrad Röntgen (27 March 1845 – 10 February 1923) was a German experimental physicist who produced and detected electromagnetic radiation in a wavelength range known as X-rays (known as "Röntgen rays" in many languages).
Read commentary →Physics: Entropy
Entropy Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty.
Read commentary →Physics: 1978 Nobel Prize in Physics
1978 Nobel Prize in Physics Awarded to: Pyotr Leonidovich Kapitsa, Arno Allan Penzias, Robert Woodrow Wilson His basic inventions and discoveries in the area of low-temperature physics / for their discovery of cosmic microwave background radiation.
Read commentary →Physics: Synchrotron radiation
Synchrotron radiation Synchrotron radiation (also known as magnetobremsstrahlung) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (a ⊥ v).
Read commentary →Physics: Stefan–Boltzmann law
Stefan–Boltzmann law The Stefan–Boltzmann law, also known as Stefan's law, describes the intensity of the thermal radiation emitted by matter in terms of that matter's temperature.
Read commentary →Physics: Laser
Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
Read commentary →Physics: Arthur Schawlow
Arthur Schawlow (1921) Arthur Leonard Schawlow (May 5, 1921 – April 28, 1999) was an American physicist who, along with Charles Townes, developed the theoretical basis for laser science.
Read commentary →Physics: Robert Brown
Robert Brown (1773) Jason Robert Brown (born June 20, 1970) is an American musical theatre composer, lyricist, and playwright.
Read commentary →Physics: Radioactive decay
Radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation.
Read commentary →Physics: Zeroth law of thermodynamics
Zeroth law of thermodynamics The zeroth law of thermodynamics is one of the four principal laws of thermodynamics.
Read commentary →Physics: Sadi Carnot
Sadi Carnot (1796) Nicolas Léonard Sadi Carnot (French: [nikɔla leɔnaʁ sadi kaʁno]; 1 June 1796 – 24 August 1832) was a French military engineer and physicist.
Read commentary →Physics: William Thomson (Lord Kelvin)
William Thomson (Lord Kelvin) (1824) William Thomson, 1st Baron Kelvin (26 June 1824 – 17 December 1907), was a British mathematician, mathematical physicist and engineer.
Read commentary →Physics: Avogadro's law
Avogadro's law Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) or Avogadro-Ampère's hypothesis is an experimental gas law relating the volume of a gas to the amount of substance of gas present.
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What is entropy explained simply?
Entropy is a measure of disorder or randomness in a system. The second law of thermodynamics says that entropy in a closed system always increases or stays the same — it never decreases on its own. A simple illustration: if you drop a glass, it shatters into many pieces (high entropy). The pieces never spontaneously reassemble into a glass (low entropy) because there are vastly more ways to be shattered than to be whole.
What are the 4 laws of thermodynamics?
The Zeroth Law establishes thermal equilibrium. The First Law states energy cannot be created or destroyed, only converted. The Second Law states entropy always increases in a closed system. The Third Law states that as temperature approaches absolute zero, entropy approaches a constant minimum. The Second Law is the most philosophically significant — it gives time its direction (the 'arrow of time').