# kb

id: nuclear-fusion-20260505-8
file: data/en.wikipedia.org/wiki/Nuclear_fusion-8.md
category: reference
title: Nuclear fusion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_fusion
date_saved: 2026-05-05T10:55:43.941196+00:00
instance: kb-cron
parent: nuclear-fusion-20260505-0
summary:
The last column is the neutronicity of the reaction, the fraction of the fusion energy released as neutrons. This is an important indicator of the magnitude of the problems associated with neutrons like radiation damage, biological shielding, remote handling, and safety. For the first two reactions it is calculated as (Efus − Ech)/Efus. For the last two reactions, where this calculation would give zero, the values quoted are rough estimates based on side reactions that produce neutrons in a plasma in thermal equilibrium. Of course, the reactants should also be mixed in the optimal proportions. This is the case when each reactant ion plus its associated electrons accounts for half the pressure. Assuming that the total pressure is fixed, this means that particle density of the non-hydrogenic ion is smaller than that of the hydrogenic ion by a factor 2/(Z + 1). Therefore, the rate for these reactions is reduced by the same factor, on top of any differences in the values of ⟨σv⟩/T2. On the other hand, because the 21D–21D reaction has only one reactant, its rate is twice as high as when the fuel is divided between two different hydrogenic species, thus creating a more efficient reaction. Thus


id: nuclear-fusion-20260505-9
file: data/en.wikipedia.org/wiki/Nuclear_fusion-9.md
category: reference
title: Nuclear fusion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_fusion
date_saved: 2026-05-05T10:55:43.941196+00:00
instance: kb-cron
parent: nuclear-fusion-20260505-0
summary:
The actual ratios of fusion to Bremsstrahlung power will likely be significantly lower for several reasons. For one, the calculation assumes that the energy of the fusion products is transmitted completely to the fuel ions, which then lose energy to the electrons by collisions, which in turn lose energy by Bremsstrahlung. However, because the fusion products move much faster than the fuel ions, they will give up a significant fraction of their energy directly to the electrons. Secondly, the ions in the plasma are assumed to be purely fuel ions. In practice, there will be a significant proportion of impurity ions, which will then lower the ratio. In particular, the fusion products themselves must remain in the plasma until they have given up their energy, and will remain for some time after that in any proposed confinement scheme. Finally, all channels of energy loss other than Bremsstrahlung have been neglected. The last two factors are related. On theoretical and experimental grounds, particle and energy confinement seem to be closely related. In a confinement scheme that does a good job of retaining energy, fusion products will build up. If the fusion products are efficiently ejected, then energy confinement will be poor,


id: nuclear-fusion-20260505-10
file: data/en.wikipedia.org/wiki/Nuclear_fusion-10.md
category: reference
title: Nuclear fusion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_fusion
date_saved: 2026-05-05T10:55:43.941196+00:00
instance: kb-cron
parent: nuclear-fusion-20260505-0
summary:
Bosch-Hale also reports a R-matrix calculated cross sections fitting observation data with Padé rational approximating coefficients. With energy in units of keV and cross sections in units of millibarn, the factor has the form: S Bosch-Hale ( ϵ ) = A 1 + ϵ ( A 2 + ϵ ( A 3 + ϵ ( A 4 + ϵ A 5 ) ) ) 1 + ϵ ( B 1 + ϵ ( B 2 + ϵ ( B 3 + ϵ B 4 ) ) ) {\displaystyle S^{\text{Bosch-Hale}}(\epsilon )={\frac {A_{1}+\epsilon {\bigg (}A_{2}+\epsilon {\big (}A_{3}+\epsilon (A_{4}+\epsilon A_{5}){\big )}{\bigg )}}{1+\epsilon {\bigg (}B_{1}+\epsilon {\big (}B_{2}+\epsilon (B_{3}+\epsilon B_{4}){\big )}{\bigg )}}}} , with the coefficient values: where σ Bosch-Hale ( ϵ ) = S Bosch-Hale ( ϵ ) ϵ exp ⁡ ( ϵ G / ϵ ) {\displaystyle \sigma ^{\text{Bosch-Hale}}(\epsilon )={\frac {S^{\text{Bosch-Hale}}(\epsilon )}{\epsilon \exp(\epsilon _{G}/{\sqrt {\epsilon }})}}} === Maxwell-averaged nuclear cross sections === In fusion systems that are in thermal equilibrium, the particles are in a Maxwell–Boltzmann distribution, meaning the particles have a range of energies centered around the plasma temperature. The sun, magnetically confined plasmas and inertial confinement fusion systems are well modeled to be in thermal equilibrium. In these cases, the value


id: nuclear-reaction-20260505-0
file: data/en.wikipedia.org/wiki/Nuclear_reaction-0.md
category: reference
title: Nuclear reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_reaction
date_saved: 2026-05-05T10:55:45.173780+00:00
instance: kb-cron
parent: nuclear-reaction-20260505-0
summary:
In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle, and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction. In principle, a reaction can involve more than two particles colliding, but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare (see triple alpha process for an example very close to a three-body nuclear reaction). The term "nuclear reaction" may refer either to a change in a nuclide induced by collision with another particle or to a spontaneous change of a nuclide without collision. Natural nuclear reactions occur in the interaction between cosmic rays and matter, and nuclear reactions can be employed artificially to obtain nuclear energy, at an adjustable rate, on-demand. Nuclear chain


id: nuclear-reaction-20260505-1
file: data/en.wikipedia.org/wiki/Nuclear_reaction-1.md
category: reference
title: Nuclear reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_reaction
date_saved: 2026-05-05T10:55:45.173780+00:00
instance: kb-cron
parent: nuclear-reaction-20260505-0
summary:
kinetic energy of the product particles (fraction of the kinetic energy of the charged nuclear reaction products can be directly converted into electrostatic energy); emission of very high energy photons, called gamma rays; some energy may remain in the nucleus, as a metastable energy level. When the product nucleus is metastable, this is indicated by placing an asterisk ("*") next to its atomic number. This energy is eventually released through nuclear decay. A small amount of energy may also emerge in the form of X-rays. Generally, the product nucleus has a different atomic number, and thus the configuration of its electron shells is wrong. As the electrons rearrange themselves and drop to lower energy levels, internal transition X-rays (X-rays with precisely defined emission lines) may be emitted. == Q-value and energy balance == In writing down the reaction equation, in a way analogous to a chemical equation, one may, in addition, give the reaction energy on the right side: For the particular case discussed above, the reaction energy has already been calculated as Q = 22.2 MeV. Hence: The reaction energy (the "Q-value") is positive for exothermal reactions and negative for endothermal reactions, opposite to the similar expression in chemistry.


id: nuclear-reaction-20260505-2
file: data/en.wikipedia.org/wiki/Nuclear_reaction-2.md
category: reference
title: Nuclear reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_reaction
date_saved: 2026-05-05T10:55:45.173780+00:00
instance: kb-cron
parent: nuclear-reaction-20260505-0
summary:
(α,n) and (α,p) reactions. Some of the earliest nuclear reactions studied involved an alpha particle produced by alpha decay, knocking a nucleon from a target nucleus. (d,n) and (d,p) reactions. A deuteron beam impinges on a target; the target nuclei absorb either the neutron or proton from the deuteron. The deuteron is so loosely bound that this is almost the same as proton or neutron capture. A compound nucleus may be formed, leading to additional neutrons being emitted more slowly. (d,n) reactions are used to generate energetic neutrons. The strangeness exchange reaction (K, π) has been used to study hypernuclei. The reaction 14N(α,p)17O performed by Rutherford in 1917 (reported 1919), is generally regarded as the first nuclear transmutation experiment. ==== Reactions with neutrons ==== Reactions with neutrons are important in nuclear reactors and nuclear weapons. While the best-known neutron reactions are neutron scattering, neutron capture, and nuclear fission, for some light nuclei (especially odd-odd nuclei) the most probable reaction with a thermal neutron is a transfer reaction: Some reactions are only possible with fast neutrons: (n,2n) reactions produce small amounts of protactinium-231 and uranium-232 in the thorium cycle which is otherwise relatively free of highly radioactive actinide products. 9Be +


id: observer-effect-physics-20260505-0
file: data/en.wikipedia.org/wiki/Observer_effect_(physics)-0.md
category: reference
title: Observer effect (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Observer_effect_(physics)
date_saved: 2026-05-05T10:55:46.414538+00:00
instance: kb-cron
parent: observer-effect-physics-20260505-0
summary:
In physics, the observer effect is the disturbance of a system by the act of observation. This is often the result of utilising instruments that, by necessity, alter the state of what they measure in some manner. A common example is checking the pressure in an automobile tire, which causes some of the air to escape, thereby changing the amount of pressure one observes. Similarly, seeing non-luminous objects requires light hitting the object to cause it to reflect that light. While the effects of observation are often negligible, the object still experiences a change. This effect can be found in many domains of physics, but can usually be reduced to insignificance by using various instruments or observation techniques. A notable example of the observer effect occurs in quantum mechanics, as demonstrated by the double-slit experiment. Physicists have found that observation of quantum phenomena by a detector or an instrument can change the measured results of this experiment. Despite the "observer effect" in the double-slit experiment being caused by the presence of an electronic detector, the experiment's results have been interpreted by some to suggest that a conscious mind can directly affect reality. However, the need for the "observer" to be


id: optogalvanic-effect-20260505-0
file: data/en.wikipedia.org/wiki/Optogalvanic_effect-0.md
category: reference
title: Optogalvanic effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Optogalvanic_effect
date_saved: 2026-05-05T10:55:47.865472+00:00
instance: kb-cron
parent: optogalvanic-effect-20260505-0
summary:
The Optogalvanic effect is the change in the conductivity of a gas discharge induced by a light source (typically a laser). This effect has found many applications in atomic spectroscopy and laser stabilization. == Introduction == In general, neutral atoms/molecules are generated in a gas discharge, and some of these neutral particles will be subsequently ionized, thereby creating a plasma. Incoming light will excite electronic transitions if the energy difference between pairs of atomic/molecular levels is in resonance with a frequency component of this light. Now, the probability and the cross-section to ionize one neutral particle depends on its initial energetic state. This means that light can change the rate at which neutral particles are ionised. Since the medium contains charged particles, it is not surprising that also the electrical properties of the gas discharge can change. == References ==


id: paramagnetism-20260505-0
file: data/en.wikipedia.org/wiki/Paramagnetism-0.md
category: reference
title: Paramagnetism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paramagnetism
date_saved: 2026-05-05T10:55:49.100672+00:00
instance: kb-cron
parent: paramagnetism-20260505-0
summary:
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, diamagnetic materials are repelled by magnetic fields and form induced magnetic fields in the direction opposite to that of the applied magnetic field. Paramagnetic materials include most chemical elements and some compounds; they have a relative magnetic permeability slightly greater than 1 (i.e., a small positive magnetic susceptibility) and hence are attracted to magnetic fields. The magnetic moment induced by the applied field is linear in the field strength and rather weak. It typically requires a sensitive analytical balance to detect the effect and modern measurements on paramagnetic materials are often conducted with a SQUID magnetometer. Paramagnetism is due to the presence of unpaired electrons in the material, so most atoms with incompletely filled atomic orbitals are paramagnetic, although exceptions such as copper exist. Due to their spin, unpaired electrons have a magnetic dipole moment and act like tiny magnets. An external magnetic field causes the electrons' spins to align parallel to the field, causing a net attraction. Paramagnetic materials include aluminium, oxygen,


id: paramagnetism-20260505-1
file: data/en.wikipedia.org/wiki/Paramagnetism-1.md
category: reference
title: Paramagnetism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paramagnetism
date_saved: 2026-05-05T10:55:49.100672+00:00
instance: kb-cron
parent: paramagnetism-20260505-0
summary:
==== d and f electrons ==== Stronger magnetic effects are typically only observed when d or f electrons are involved. Particularly the latter are usually strongly localized. Moreover, the size of the magnetic moment on a lanthanide atom can be quite large as it can carry up to 7 unpaired electrons in the case of gadolinium(III) (hence its use in MRI). The high magnetic moments associated with lanthanides is one reason why superstrong magnets are typically based on elements like neodymium or samarium. ==== Molecular localization ==== The above picture is a generalization as it pertains to materials with an extended lattice rather than a molecular structure. Molecular structure can also lead to localization of electrons. Although there are usually energetic reasons why a molecular structure results such that it does not exhibit partly filled orbitals (i.e. unpaired spins), some non-closed shell moieties do occur in nature. Molecular oxygen is a good example. Even in the frozen solid it contains di-radical molecules resulting in paramagnetic behavior. The unpaired spins reside in orbitals derived from oxygen p wave functions, but the overlap is limited to the one neighbor in the O2 molecules. The distances to other oxygen atoms in the lattice


id: paramagnetism-20260505-2
file: data/en.wikipedia.org/wiki/Paramagnetism-2.md
category: reference
title: Paramagnetism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paramagnetism
date_saved: 2026-05-05T10:55:49.100672+00:00
instance: kb-cron
parent: paramagnetism-20260505-0
summary:
n ↑ ≈ n e 2 − μ 0 μ B 2 g ( E F ) H ; ( n ↓ ≈ n e 2 + μ 0 μ B 2 g ( E F ) H ) , {\displaystyle n_{\uparrow }\approx {\frac {n_{\text{e}}}{2}}-{\frac {\mu _{0}\mu _{\mathrm {B} }}{2}}g(E_{\mathrm {F} })H\quad ;\quad \left(n_{\downarrow }\approx {\frac {n_{\text{e}}}{2}}+{\frac {\mu _{0}\mu _{\mathrm {B} }}{2}}g(E_{\mathrm {F} })H\right),} with n e {\displaystyle n_{\text{e}}} the total free-electron density and g ( E F ) {\displaystyle g(E_{\mathrm {F} })} the electronic density of states (number of states per energy per volume) at the Fermi energy E F {\displaystyle E_{\mathrm {F} }} . In this approximation the magnetization is given as the magnetic moment of one electron times the difference in densities: M = μ B ( n ↓ − n ↑ ) = μ 0 μ B 2 g ( E F ) H , {\displaystyle M=\mu _{\mathrm {B} }(n_{\downarrow }-n_{\uparrow })=\mu _{0}\mu _{\mathrm {B} }^{2}g(E_{\mathrm {F} })H,} which yields a positive paramagnetic susceptibility independent of temperature: χ P = μ 0 μ B 2 g ( E F ) . {\displaystyle \chi _{\mathrm {P} }=\mu _{0}\mu _{\mathrm {B} }^{2}g(E_{\mathrm {F} }).} The Pauli paramagnetic susceptibility


id: paramagnetism-20260505-3
file: data/en.wikipedia.org/wiki/Paramagnetism-3.md
category: reference
title: Paramagnetism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paramagnetism
date_saved: 2026-05-05T10:55:49.100672+00:00
instance: kb-cron
parent: paramagnetism-20260505-0
summary:
As stated above, many materials that contain d- or f-elements do retain unquenched spins. Salts of such elements often show paramagnetic behavior but at low enough temperatures the magnetic moments may order. It is not uncommon to call such materials 'paramagnets', when referring to their paramagnetic behavior above their Curie or Néel-points, particularly if such temperatures are very low or have never been properly measured. Even for iron it is not uncommon to say that iron becomes a paramagnet above its relatively high Curie-point. In that case the Curie-point is seen as a phase transition between a ferromagnet and a 'paramagnet'. The word paramagnet now merely refers to the linear response of the system to an applied field, the temperature dependence of which requires an amended version of Curie's law, known as the Curie–Weiss law: M = C T − θ H {\displaystyle \mathbf {M} ={\frac {C}{T-\theta }}\mathbf {H} } This amended law includes a term θ that describes the exchange interaction that is present albeit overcome by thermal motion. The sign of θ depends on whether ferro- or antiferromagnetic interactions dominate and it is seldom exactly zero, except in the dilute, isolated cases mentioned above. Obviously, the paramagnetic Curie–Weiss


id: phase-transition-20260505-0
file: data/en.wikipedia.org/wiki/Phase_transition-0.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
In physics, chemistry and biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of matter: solid, liquid, and gas, and in rare cases, plasma. A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change as a result of the change of external conditions, such as temperature or pressure. This can be a discontinuous change; for example, a liquid may become gas upon heating to its boiling point, resulting in an abrupt change in volume. The identification of the external conditions at which a transformation occurs defines the phase transition point. == Types == === States of matter === Phase transitions commonly refer to when a substance transforms between one of the four states of matter to another. At the phase transition point for a substance, for instance the boiling point, the two phases involved - liquid and vapor, have identical free energies and therefore are equally likely to exist. Below the boiling point, the liquid is


id: phase-transition-20260505-1
file: data/en.wikipedia.org/wiki/Phase_transition-1.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
Transition to a mesophase between solid and liquid, such as one of the "liquid crystal" phases. The dependence of the adsorption geometry on coverage and temperature, such as for hydrogen on iron (110). The emergence of superconductivity in certain metals and ceramics when cooled below a critical temperature. The emergence of metamaterial properties in artificial photonic media as their parameters are varied. Quantum condensation of bosonic fluids (Bose–Einstein condensation). The superfluid transition in liquid helium is an example of this. The breaking of symmetries in the laws of physics during the early history of the universe as its temperature cooled. Isotope fractionation occurs during a phase transition, the ratio of light to heavy isotopes in the involved molecules changes. When water vapor condenses (an equilibrium fractionation), the heavier water isotopes (18O and 2H) become enriched in the liquid phase while the lighter isotopes (16O and 1H) tend toward the vapor phase. Phase transitions occur when the thermodynamic free energy of a system is non-analytic for some choice of thermodynamic variables (cf. phases). This condition generally stems from the interactions of a large number of particles in a system, and does not appear in systems that are small. Phase transitions can


id: phase-transition-20260505-2
file: data/en.wikipedia.org/wiki/Phase_transition-2.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
In the modern classification scheme, phase transitions are divided into two broad categories, named similarly to the Ehrenfest classes: First-order phase transitions are those that involve a latent heat. During such a transition, a system either absorbs or releases a fixed (and typically large) amount of energy per volume. During this process, the temperature of the system will stay constant as heat is added: the system is in a "mixed-phase regime" in which some parts of the system have completed the transition and others have not. Familiar examples are the melting of ice or the boiling of water. (Water does not instantly turn into vapor, but forms a turbulent mixture of liquid water and vapor bubbles.) Related primary research reports have suggested that quenched disorder can broaden a first-order transition: that while transformation is completed over a finite range of temperatures, phenomena like supercooling and superheating survive, and hysteresis is observed on thermal cycling. Second-order phase transitions, also called "continuous phase transitions", are characterized by a divergent susceptibility—the change of an extensive property under variation of an intensive property), an infinite correlation length, and a power law decay of correlations near criticality. Examples of second-order phase transitions are the ferromagnetic


id: phase-transition-20260505-3
file: data/en.wikipedia.org/wiki/Phase_transition-3.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
=== Order parameters === An order parameter is a measure of the degree of order across the boundaries in a phase transition system; it normally takes on the value of zero in one phase (usually above the critical point) and nonzero in the other. At the critical point, the order parameter susceptibility (the change of an extensive property under variation of an intensive property) will usually diverge. An example of an order parameter is the net magnetization in a ferromagnetic system undergoing a phase transition. For liquid/gas transitions, the order parameter is the difference of the densities. From a theoretical perspective, order parameters arise from symmetry breaking. When this happens, one needs to introduce one or more extra variables to describe the state of the system. For example, in the ferromagnetic phase, one must provide the net magnetization, whose direction was spontaneously chosen when the system cooled below the Curie point. However, note that order parameters can also be defined for non-symmetry-breaking transitions. Some phase transitions, such as superconducting and ferromagnetic, can have order parameters for more than one degree of freedom. In such phases, the order parameter may take the form of a complex number, a vector, or even


id: phase-transition-20260505-4
file: data/en.wikipedia.org/wiki/Phase_transition-4.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
It can be shown that there are only two independent exponents, e.g. ν and η. It is a remarkable fact that phase transitions arising in different systems often possess the same set of critical exponents. This phenomenon is known as universality. For example, the critical exponents at the liquid–gas critical point have been found to be independent of the chemical composition of the fluid. More impressively, but understandably from above, they are an exact match for the critical exponents of the ferromagnetic phase transition in uniaxial magnets. Such systems are said to be in the same universality class. Universality is a prediction of the renormalization group theory of phase transitions, which states that the thermodynamic properties of a system near a phase transition depend only on a small number of features, such as dimensionality and symmetry, and are insensitive to the underlying microscopic properties of the system. Again, the divergence of the correlation length is the essential point. === Critical phenomena === There are also other critical phenomena; e.g., besides static functions there is also critical dynamics. As a consequence, at a phase transition one may observe critical slowing down or speeding up. Connected to the previous phenomenon is also


id: phase-transition-20260505-5
file: data/en.wikipedia.org/wiki/Phase_transition-5.md
category: reference
title: Phase transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_transition
date_saved: 2026-05-05T10:55:50.323304+00:00
instance: kb-cron
parent: phase-transition-20260505-0
summary:
== Further reading == Nishimori, Hidetoshi; Ortiz, Gerardo (2010). Elements of Phase Transitions and Critical Phenomena. Oxford University Press. ISBN 9780191722943. Faghri, A., and Zhang, Y., Fundamentals of Multiphase Heat Transfer and Flow Archived 14 June 2021 at the Wayback Machine, Springer Nature Switzerland AG, 2020. Fisher, M.E. (1974). "The renormalization group in the theory of critical behavior". Rev. Mod. Phys. 46 (4): 597–616. Bibcode:1974RvMP...46..597F. doi:10.1103/revmodphys.46.597. Goldenfeld, N., Lectures on Phase Transitions and the Renormalization Group, Perseus Publishing (1992). Ivancevic, Vladimir G; Ivancevic, Tijana T (2008), Chaos, Phase Transitions, Topology Change and Path Integrals, Berlin: Springer, ISBN 978-3-540-79356-4, retrieved 14 March 2013 M.R. Khoshbin-e-Khoshnazar, Ice Phase Transition as a sample of finite system phase transition, (Physics Education (India) Volume 32. No. 2, Apr - Jun 2016) Archived 29 April 2025 at the Wayback Machine Kleinert, H., Gauge Fields in Condensed Matter, Vol. I, "Superfluidity and Vortex lines; Disorder Fields, Phase Transitions", pp. 1–742, World Scientific (Singapore, 1989); Paperback ISBN 9971-5-0210-0 (physik.fu-berlin.de readable online Archived 27 May 2008 at the Wayback Machine) Kleinert, Hagen; Verena Schulte-Frohlinde (2001). Critical Properties of φ4-Theories. World Scientific. ISBN 981-02-4659-5. Archived from the original on 26 February 2008. (readable online Archived 29 June 2008 at the


id: photon-polarization-20260505-0
file: data/en.wikipedia.org/wiki/Photon_polarization-0.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. An individual photon can be described as having right or left circular polarization, or a superposition of the two. Equivalently, a photon can be described as having horizontal or vertical linear polarization, or a superposition of the two. The description of photon polarization contains many of the physical concepts and much of the mathematical machinery of more involved quantum descriptions, such as the quantum mechanics of an electron in a potential well. Polarization is an example of a qubit degree of freedom, which forms a fundamental basis for an understanding of more complicated quantum phenomena. Much of the mathematical machinery of quantum mechanics, such as state vectors, probability amplitudes, unitary operators, and Hermitian operators, emerge naturally from the classical Maxwell's equations in the description. The quantum polarization state vector for the photon, for instance, is identical with the Jones vector, usually used to describe the polarization of a classical wave. Unitary operators emerge from the classical requirement of the conservation of energy of a classical wave propagating through lossless media that alter the polarization state of the wave. Hermitian operators then follow for infinitesimal transformations


id: photon-polarization-20260505-1
file: data/en.wikipedia.org/wiki/Photon_polarization-1.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
| ψ ⟩ = d e f ( ψ x ψ y ) = ( cos ⁡ θ exp ⁡ ( i α x ) sin ⁡ θ exp ⁡ ( i α y ) ) . {\displaystyle |\psi \rangle \ {\stackrel {\mathrm {def} }{=}}\ {\begin{pmatrix}\psi _{x}\\\psi _{y}\end{pmatrix}}={\begin{pmatrix}\cos \theta \exp \left(i\alpha _{x}\right)\\\sin \theta \exp \left(i\alpha _{y}\right)\end{pmatrix}}.} ==== Geometric visualization of an arbitrary polarization state ==== To get an understanding of what a polarization state looks like, one can observe the orbit that is made if the polarization state is multiplied by a phase factor of e i ω t {\displaystyle e^{i\omega t}} and then having the real parts of its components interpreted as x and y coordinates respectively. That is: ( x ( t ) y ( t ) ) = ( ℜ ( e i ω t ψ x ) ℜ ( e i ω t ψ y ) ) = ℜ [ e i ω t ( ψ x ψ y ) ] = ℜ ( e i ω t | ψ ⟩ ) . {\displaystyle {\begin{pmatrix}x(t)\\y(t)\end{pmatrix}}={\begin{pmatrix}\Re (e^{i\omega t}\psi _{x})\\\Re (e^{i\omega t}\psi _{y})\end{pmatrix}}=\Re \left[e^{i\omega t}{\begin{pmatrix}\psi _{x}\\\psi _{y}\end{pmatrix}}\right]=\Re \left(e^{i\omega t}|\psi \rangle \right).} If only the traced out shape and


id: photon-polarization-20260505-2
file: data/en.wikipedia.org/wiki/Photon_polarization-2.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
A linear filter transmits one component of a plane wave and absorbs the perpendicular component. In that case, if the filter is polarized in the x direction, the fraction of energy passing through the filter is f x = ψ x ∗ ψ x = cos 2 ⁡ θ . {\displaystyle f_{x}=\psi _{x}^{*}\psi _{x}=\cos ^{2}\theta .\,} === Example of energy conservation: Passage of a classical wave through a birefringent crystal === An ideal birefringent crystal transforms the polarization state of an electromagnetic wave without loss of wave energy. Birefringent crystals therefore provide an ideal test bed for examining the conservative transformation of polarization states. Even though this treatment is still purely classical, standard quantum tools such as unitary and Hermitian operators that evolve the state in time naturally emerge. ==== Initial and final states ==== A birefringent crystal is a material that has an optic axis with the property that the light has a different index of refraction for light polarized parallel to the axis than it has for light polarized perpendicular to the axis. Light polarized parallel to the axis are called "extraordinary rays" or "extraordinary photons", while light polarized perpendicular to the axis are called "ordinary rays" or


id: photon-polarization-20260505-3
file: data/en.wikipedia.org/wiki/Photon_polarization-3.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
The photon energy can be related to classical fields through the correspondence principle that states that for a large number of photons, the quantum and classical treatments must agree. Thus, for very large N {\displaystyle N} , the quantum energy density must be the same as the classical energy density N ℏ ω V = E c = | E | 2 8 π . {\displaystyle {N\hbar \omega \over V}={\mathcal {E}}_{c}={\frac {\vert \mathbf {E} \vert ^{2}}{8\pi }}.} The number of photons in the box is then N = V 8 π ℏ ω | E | 2 . {\displaystyle N={\frac {V}{8\pi \hbar \omega }}\vert \mathbf {E} \vert ^{2}.} ==== Momentum ==== The correspondence principle also determines the momentum and angular momentum of the photon. For momentum P z = N ℏ ω c V = N ℏ k z V {\displaystyle {\mathcal {P}}_{z}={N\hbar \omega \over cV}={N\hbar k_{z} \over V}} where k z {\displaystyle k_{z}} is the wave number. This implies that the momentum of a photon is p z = ℏ k z . {\displaystyle p_{z}=\hbar k_{z}.\,} ==== Angular momentum and spin ==== Similarly for the spin angular momentum L = 1 ω E c ( | ψ R |


id: photon-polarization-20260505-4
file: data/en.wikipedia.org/wiki/Photon_polarization-4.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
To see this, note S ^ d exp ⁡ ( i α x − i s θ ) | s ⟩ → i ∂ ∂ θ exp ⁡ ( i α x − i s θ ) | s ⟩ = s [ exp ⁡ ( i α x − i s θ ) | s ⟩ ] . {\displaystyle {\hat {S}}_{d}\exp \left(i\alpha _{x}-is\theta \right)|s\rangle \rightarrow i{\partial \over \partial \theta }\exp \left(i\alpha _{x}-is\theta \right)|s\rangle =s\left[\exp \left(i\alpha _{x}-is\theta \right)|s\rangle \right].} The spin angular momentum operator is l ^ z = ℏ S ^ d . {\displaystyle {\hat {l}}_{z}=\hbar {\hat {S}}_{d}.} === Nature of probability in quantum mechanics === ==== Probability for a single photon ==== There are two ways in which probability can be applied to the behavior of photons; probability can be used to calculate the probable number of photons in a particular state, or probability can be used to calculate the likelihood of a single photon to be in a particular state. The former interpretation violates energy conservation. The latter interpretation is the viable, if nonintuitive, option. Dirac explains this in the context of the double-slit experiment: Some time before the discovery of quantum mechanics people realized that the


id: photon-polarization-20260505-5
file: data/en.wikipedia.org/wiki/Photon_polarization-5.md
category: reference
title: Photon polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon_polarization
date_saved: 2026-05-05T10:55:51.584316+00:00
instance: kb-cron
parent: photon-polarization-20260505-0
summary:
==== Application to angular momentum ==== The connection to physics can be made if we identify the operators with physical operators such as the angular momentum and the polarization angle. We have then Δ ψ L ^ z Δ ψ θ ≥ ℏ 2 , {\displaystyle \Delta _{\psi }{\hat {L}}_{z}\,\Delta _{\psi }{\theta }\geq {\frac {\hbar }{2}},} which means that angular momentum and the polarization angle cannot be measured simultaneously with infinite accuracy. (The polarization angle can be measured by checking whether the photon can pass through a polarizing filter oriented at a particular angle, or a polarizing beam splitter. This results in a yes/no answer that, if the photon was plane-polarized at some other angle, depends on the difference between the two angles.) === States, probability amplitudes, unitary and Hermitian operators, and eigenvectors === Much of the mathematical apparatus of quantum mechanics appears in the classical description of a polarized sinusoidal electromagnetic wave. The Jones vector for a classical wave, for instance, is identical with the quantum polarization state vector for a photon. The right and left circular components of the Jones vector can be interpreted as probability amplitudes of spin states of the photon. Energy conservation requires that the


id: photophoresis-20260505-0
file: data/en.wikipedia.org/wiki/Photophoresis-0.md
category: reference
title: Photophoresis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photophoresis
date_saved: 2026-05-05T10:55:52.870083+00:00
instance: kb-cron
parent: photophoresis-20260505-0
summary:
Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform distribution of temperature of an illuminated particle in a fluid medium. Separately from photophoresis, in a fluid mixture of different kinds of particles, the migration of some kinds of particles may be due to differences in their absorptions of thermal radiation and other thermal effects collectively known as thermophoresis. In laser photophoresis, particles migrate once they have a refractive index different from their surrounding medium. The migration of particles is usually possible when the laser is slightly or not focused. A particle with a higher refractive index compared to its surrounding molecule moves away from the light source due to momentum transfer from absorbed and scattered light photons. This is referred to as a radiation pressure force. This force depends on light intensity and particle size but has nothing to do with the surrounding medium. Just like in Crookes radiometer, light can heat up one side and gas molecules bounce from that surface with greater velocity, hence push the particle to the other side.


id: physical-change-20260505-0
file: data/en.wikipedia.org/wiki/Physical_change-0.md
category: reference
title: Physical change
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_change
date_saved: 2026-05-05T10:55:54.160341+00:00
instance: kb-cron
parent: physical-change-20260505-0
summary:
Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds. Physical changes occur when objects or substances undergo a change that does not change their chemical composition. This contrasts with the concept of chemical change in which the composition of a substance changes or one or more substances combine or break up to form new substances. In general a physical change is reversible using physical means. For example, salt dissolved in water can be recovered by allowing the water to evaporate. A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density. An example of a physical change is the process of tempering steel to form a knife blade. A steel blank is repeatedly heated and hammered which changes the hardness of the steel, its flexibility and its ability to maintain a sharp edge. Many physical changes also involve the rearrangement of


id: physical-property-20260505-0
file: data/en.wikipedia.org/wiki/Physical_property-0.md
category: reference
title: Physical property
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Physical_property
date_saved: 2026-05-05T10:55:55.382806+00:00
instance: kb-cron
parent: physical-property-20260505-0
summary:
A physical property is any property of a physical system that is measurable. The changes in the physical properties of a system can be used to describe its changes between momentary states. A quantifiable physical property is called physical quantity. Measurable physical quantities are often referred to as observables. Some physical properties are qualitative, such as shininess, brittleness, etc.; some general qualitative properties admit more specific related quantitative properties, such as in opacity, hardness, ductility, viscosity, etc. Physical properties are often characterized as intensive and extensive properties. An intensive property does not depend on the size or extent of the system, nor on the amount of matter in the object, while an extensive property shows an additive relationship. These classifications are in general only valid in cases when smaller subdivisions of the sample do not interact in some physical or chemical process when combined. Properties may also be classified with respect to the directionality of their nature. For example, isotropic properties do not change with the direction of observation, and anisotropic properties do have directional variance. It may be difficult to determine whether a given property is a material property or not. Color, for example, can be seen and measured;


id: piston-effect-20260505-0
file: data/en.wikipedia.org/wiki/Piston_effect-0.md
category: reference
title: Piston effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Piston_effect
date_saved: 2026-05-05T10:55:56.703725+00:00
instance: kb-cron
parent: piston-effect-20260505-0
summary:
Piston effect refers to the forced-air flow inside a tunnel or shaft caused by moving vehicles. It is one of numerous phenomena that engineers and designers must consider when developing a range of structures. == Cause == In open air, when a vehicle travels along, air pushed aside can move in any direction except into the ground. Inside a tunnel, air is confined by the tunnel walls to move along the tunnel. Behind the moving vehicle, as air has been pushed away, suction is created, and air is pulled to flow into the tunnel. In addition, because of fluid viscosity, the surface of the vehicle drags the air to flow with vehicle, a force experienced as skin drag by the vehicle. This movement of air by the vehicle is analogous to the operation of a mechanical piston as inside a reciprocating compressor gas pump, hence the name "piston effect". The effect is also similar to the pressure fluctuations inside drainage pipes as waste water pushes air in front of it. The piston effect is very pronounced in railway tunnels, because the cross sectional area of trains is large and in many cases almost completely fills the tunnel cross section. The


id: pouillet-effect-20260505-0
file: data/en.wikipedia.org/wiki/Pouillet_effect-0.md
category: reference
title: Pouillet effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pouillet_effect
date_saved: 2026-05-05T10:55:57.966508+00:00
instance: kb-cron
parent: pouillet-effect-20260505-0
summary:
In physics and chemical engineering, the term Pouillet effect refers to an exothermic reaction that takes place when a liquid is added to a powder. Strictly speaking, the heat generated is caused by adhesion of the liquid to the surface of the particles rather than by a chemical reaction. It was first observed in 1802 by physicist John Leslie, who noted that heat was evolved when dry sawdust was wetted with water. Claude Pouillet later described this phenomenon in 1822, and it subsequently became known as the Pouillet effect in France, and then elsewhere. == Negative Pouillet effect == Under certain conditions, a negative Pouillet effect is possible, i.e., heat can be absorbed instead of being released. G. Schwalbe showed that in the case of water below 4 degrees Celsius, the temperature of the system decreases. Joseph Mellor argued that this is due to the negative thermal expansion coefficient of water between 0 and 4 degrees Celsius, with the temperature change Δ T {\displaystyle \Delta T} given by Δ T = α T C p D Δ P {\displaystyle \Delta T={{\alpha T} \over {C_{p}D}}\Delta P} where α {\displaystyle \alpha } is the thermal expansion coefficient, C P {\displaystyle C_{P}} is


id: prandtl-glauert-singularity-20260505-0
file: data/en.wikipedia.org/wiki/Prandtl–Glauert_singularity-0.md
category: reference
title: Prandtl–Glauert singularity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Prandtl–Glauert_singularity
date_saved: 2026-05-05T10:55:59.299675+00:00
instance: kb-cron
parent: prandtl-glauert-singularity-20260505-0
summary:
The Prandtl–Glauert singularity is a theoretical construct in flow physics, often incorrectly used to explain vapor cones in transonic flows. It is the prediction by the Prandtl–Glauert transformation that infinite pressures would be experienced by an aircraft as it approaches the speed of sound. Because it is invalid to apply the transformation at these speeds, the predicted singularity does not emerge. The incorrect association is related to the early-20th-century misconception of the impenetrability of the sound barrier. == Reasons of invalidity around Mach 1 == The Prandtl–Glauert transformation assumes linearity (i.e. a small change will have a small effect that is proportional to its size). This assumption becomes inaccurate toward Mach 1 and is entirely invalid in places where the flow reaches supersonic speeds, since sonic shock waves are instantaneous (and thus manifestly non-linear) changes in the flow. Indeed, one assumption in the Prandtl–Glauert transformation is approximately constant Mach number throughout the flow, and the increasing slope in the transformation indicates that very small changes will have a very strong effect at higher Mach numbers, thus violating the assumption, which breaks down entirely at the speed of sound. This means that the singularity featured by the transformation near the sonic


id: pulse-physics-20260505-0
file: data/en.wikipedia.org/wiki/Pulse_(physics)-0.md
category: reference
title: Pulse (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pulse_(physics)
date_saved: 2026-05-05T10:56:00.562549+00:00
instance: kb-cron
parent: pulse-physics-20260505-0
summary:
In physics, a pulse is an individual disturbance that propagates through a transmission medium. This medium may be vacuum (in the case of electromagnetic radiation) or matter, and may be indefinitely large or finite. Pulse movement and changes can often be described by a partial differential equation (PDE), such as a hyperbolic PDE or a parabolic PDE, which corresponds to the specific type of disturbance. == Reflection of a wave-like pulse == Consider a deformation pulse moving through an elastic medium - perhaps through a rope or a slinky. When the pulse reaches the end of that medium, what happens to it depends on whether the medium is fixed in space or free to move at its end. For example, if the pulse is moving through a rope and the end of the rope is held firmly by a person, then it is said that the pulse is approaching a fixed end. On the other hand, if the end of the rope is fixed to a stick such that it is free to move up or down along the stick when the pulse reaches its end, then it is said that the pulse is approaching a free end. === Free


id: quantization-physics-20260505-0
file: data/en.wikipedia.org/wiki/Quantization_(physics)-0.md
category: reference
title: Quantization (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quantization_(physics)
date_saved: 2026-05-05T10:56:01.873549+00:00
instance: kb-cron
parent: quantization-physics-20260505-0
summary:
Quantization (in British English quantisation) is the systematic transition procedure from a classical understanding of physical phenomena to a newer understanding known as quantum mechanics. It is a procedure for constructing quantum mechanics from classical mechanics. A generalization involving infinite degrees of freedom is field quantization, as in the "quantization of the electromagnetic field", referring to photons as field "quanta" (for instance as light quanta). This procedure is basic to theories of atomic physics, chemistry, particle physics, nuclear physics, condensed matter physics, and quantum optics. == Historical overview == In 1901, when Max Planck was developing the distribution function of statistical mechanics to solve the ultraviolet catastrophe problem, he realized that the properties of blackbody radiation can be explained by the assumption that the amount of energy must be in countable fundamental units, i.e. amount of energy is not continuous but discrete. That is, a minimum unit of energy exists and the following relationship holds E = h ν {\displaystyle E=h\nu } for the frequency ν {\displaystyle \nu } . Here, h {\displaystyle h} is called the Planck constant, which represents the amount of the quantum mechanical effect. It means a fundamental change of mathematical model of physical quantities. In


id: quantization-physics-20260505-1
file: data/en.wikipedia.org/wiki/Quantization_(physics)-1.md
category: reference
title: Quantization (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quantization_(physics)
date_saved: 2026-05-05T10:56:01.873549+00:00
instance: kb-cron
parent: quantization-physics-20260505-0
summary:
In mathematical physics, geometric quantization is a mathematical approach to defining a quantum theory corresponding to a given classical theory. It attempts to carry out quantization, for which there is in general no exact recipe, in such a way that certain analogies between the classical theory and the quantum theory remain manifest. For example, the similarity between the Heisenberg equation in the Heisenberg picture of quantum mechanics and the Hamilton equation in classical physics should be built in. A more geometric approach to quantization, in which the classical phase space can be a general symplectic manifold, was developed in the 1970s by Bertram Kostant and Jean-Marie Souriau. The method proceeds in two stages. First, once constructs a "prequantum Hilbert space" consisting of square-integrable functions (or, more properly, sections of a line bundle) over the phase space. Here one can construct operators satisfying commutation relations corresponding exactly to the classical Poisson-bracket relations. On the other hand, this prequantum Hilbert space is too big to be physically meaningful. One then restricts to functions (or sections) depending on half the variables on the phase space, yielding the quantum Hilbert space. == Path integral quantization == A classical mechanical theory is given by an


id: quasiparticle-20260505-0
file: data/en.wikipedia.org/wiki/Quasiparticle-0.md
category: reference
title: Quasiparticle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quasiparticle
date_saved: 2026-05-05T10:56:03.122412+00:00
instance: kb-cron
parent: quasiparticle-20260505-0
summary:
In condensed matter physics, a quasiparticle is a concept used to describe a collective behavior of a group of particles that can be treated as if they were a single particle. Formally, quasiparticles and collective excitations are closely related phenomena that arise when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in vacuum. For example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with other electrons and with atomic nuclei. The electron behaves as though it has a different effective mass travelling unperturbed in vacuum. Such an electron is called an electron quasiparticle. In another example, the aggregate motion of electrons in the valence band of a semiconductor or a hole band in a metal behave as though the material instead contained positively charged quasiparticles called electron holes. Other quasiparticles or collective excitations include the phonon, a quasiparticle derived from the vibrations of atoms in a solid, and the plasmon, a particle derived from plasma oscillation. These phenomena are typically called quasiparticles if they are related to fermions, and called collective excitations if they are related to bosons, although the precise


id: quasiparticle-20260505-1
file: data/en.wikipedia.org/wiki/Quasiparticle-1.md
category: reference
title: Quasiparticle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quasiparticle
date_saved: 2026-05-05T10:56:03.122412+00:00
instance: kb-cron
parent: quasiparticle-20260505-0
summary:
=== Distinction between quasiparticles and collective excitations === Usually, an elementary excitation is called a "quasiparticle" if it is a fermion and a "collective excitation" if it is a boson. However, the precise distinction is not universally agreed upon. There is a difference in the way that quasiparticles and collective excitations are intuitively envisioned. A quasiparticle is usually thought of as being like a dressed particle: it is built around a real particle at its "core", but the behavior of the particle is affected by the environment. A standard example is the "electron quasiparticle": an electron in a crystal behaves as if it had an effective mass which differs from its real mass. On the other hand, a collective excitation is usually imagined to be a reflection of the aggregate behavior of the system, with no single real particle at its "core". A standard example is the phonon, which characterizes the vibrational motion of every atom in the crystal. However, these two visualizations leave some ambiguity. For example, a magnon in a ferromagnet can be considered in one of two perfectly equivalent ways: (a) as a mobile defect (a misdirected spin) in a perfect alignment of magnetic moments or (b)


id: radiation-20260505-0
file: data/en.wikipedia.org/wiki/Radiation-0.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: electromagnetic radiation consisting of photons, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ) particle radiation consisting of particles of non-zero rest energy, such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation acoustic radiation, such as ultrasound, sound, and seismic waves, all dependent on a physical transmission medium gravitational radiation, in the form of gravitational waves, ripples in spacetime Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 electron volts (eV), which is enough to ionize atoms and molecules and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic


id: radiation-20260505-1
file: data/en.wikipedia.org/wiki/Radiation-1.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
Ionizing radiation has many practical uses in medicine, research, and construction, but presents a health hazard if used improperly. Exposure to radiation causes damage to living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair loss, internal organ failure, and death, while any dose may result in an increased chance of cancer and genetic damage; a particular form of cancer, thyroid cancer, often occurs when nuclear weapons and reactors are the radiation source because of the biological proclivities of the radioactive iodine fission product, iodine-131. However, calculating the exact risk and chance of cancer forming in cells caused by ionizing radiation is still not well understood, and currently estimates are loosely determined by population-based data from the atomic bombings of Hiroshima and Nagasaki and from follow-up of reactor accidents, such as the Chernobyl disaster. The International Commission on Radiological Protection states that "The Commission is aware of uncertainties and lack of precision of the models and parameter values", "Collective effective dose is not intended as a tool for epidemiological risk assessment, and it is inappropriate to use it in risk projections" and "in particular, the calculation of the number of cancer deaths based on collective effective


id: radiation-20260505-2
file: data/en.wikipedia.org/wiki/Radiation-2.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
Alpha particles are helium-4 nuclei (two protons and two neutrons). They interact with matter strongly due to their charges and combined mass, and at their usual velocities only penetrate a few centimetres of air, or a few millimetres of low density material (such as the thin mica material which is specially placed in some Geiger counter tubes to allow alpha particles in). This means that alpha particles from ordinary alpha decay do not penetrate the outer layers of dead skin cells and cause no damage to the live tissues below. Some very high energy alpha particles compose about 10% of cosmic rays, and these are capable of penetrating the body and even thin metal plates. However, they are of danger only to astronauts, since they are deflected by the Earth's magnetic field and then stopped by its atmosphere. Alpha radiation is dangerous when alpha-emitting radioisotopes are inhaled or ingested (breathed or swallowed). This brings the radioisotope close enough to sensitive live tissue for the alpha radiation to damage cells. Per unit of energy, alpha particles are at least 20 times more effective at cell-damage than gamma rays and X-rays. See relative biological effectiveness for a discussion of this. Examples of


id: radiation-20260505-3
file: data/en.wikipedia.org/wiki/Radiation-3.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
There are two sources of high energy particles entering the Earth's atmosphere from outer space: the sun and deep space. The sun continuously emits particles, primarily free protons, in the solar wind, and occasionally augments the flow hugely with coronal mass ejections (CME). The particles from deep space (inter- and extra-galactic) are much less frequent, but of much higher energies. These particles are also mostly protons, with much of the remainder consisting of helions (alpha particles). A few completely ionized nuclei of heavier elements are present. The origin of these galactic cosmic rays is not yet well understood, but they seem to be remnants of supernovae and especially gamma-ray bursts (GRB), which feature magnetic fields capable of the huge accelerations measured from these particles. They may also be generated by quasars, which are galaxy-wide jet phenomena similar to GRBs but known for their much larger size, and which seem to be a violent part of the universe's early history. == Non-ionizing radiation == The kinetic energy of particles of non-ionizing radiation is too small to produce charged ions when passing through matter. For non-ionizing electromagnetic radiation (see types below), the associated particles (photons) have only sufficient energy to change the


id: radiation-20260505-4
file: data/en.wikipedia.org/wiki/Radiation-4.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
=== Very low frequency === Very low frequency (VLF) refers to a frequency range of 30 Hz to 3 kHz which corresponds to wavelengths of 100000 to 10000 m respectively. Since there is not much bandwidth in this range of the radio spectrum, only the very simplest signals can be transmitted, such as for radio navigation. Also known as the myriametre band or myriametre wave as the wavelengths range from 100 km to 10 km (an obsolete metric unit equal to 10 km). === Extremely low frequency === Extremely low frequency (ELF) is radiation frequencies from 3 to 30 Hz (108 to 107 m respectively). In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU Radio Bands. A massive military ELF antenna in Michigan radiates very slow messages to otherwise unreachable receivers, such as submerged submarines. === Thermal radiation (heat) === Thermal radiation is a common synonym for infrared radiation emitted by objects at temperatures often encountered on Earth. Thermal radiation refers not


id: radiation-20260505-5
file: data/en.wikipedia.org/wiki/Radiation-5.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
Electromagnetic radiation of wavelengths other than visible light were discovered in the early 19th century. The discovery of infrared radiation is ascribed to William Herschel, the astronomer. Herschel published his results in 1800 before the Royal Society of London. Herschel, like Ritter, used a prism to refract light from the Sun and detected the infrared (beyond the red part of the spectrum), through an increase in the temperature recorded by a thermometer. In 1801, the German physicist Johann Wilhelm Ritter made the discovery of ultraviolet by noting that the rays from a prism darkened silver chloride preparations more quickly than violet light. Ritter's experiments were an early precursor to what would become photography. Ritter noted that the UV rays were capable of causing chemical reactions. The first radio waves detected were not from a natural source, but were produced deliberately and artificially by the German scientist Heinrich Hertz in 1887, using electrical circuits calculated to produce oscillations in the radio frequency range, following formulas suggested by the equations of James Clerk Maxwell. Wilhelm Röntgen discovered and named X-rays. While experimenting with high voltages applied to an evacuated tube on 8 November 1895, he noticed a fluorescence on a nearby plate


id: radiation-20260505-6
file: data/en.wikipedia.org/wiki/Radiation-6.md
category: reference
title: Radiation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Radiation
date_saved: 2026-05-05T10:56:04.366371+00:00
instance: kb-cron
parent: radiation-20260505-0
summary:
Radiation is not always dangerous, and not all types of radiation are equally dangerous, contrary to several common medical myths. For example, although bananas contain naturally occurring radioactive isotopes, particularly potassium-40 (40K), which emit ionizing radiation when undergoing radioactive decay, the levels of such radiation are far too low to induce radiation poisoning, and bananas are not a radiation hazard. It would not be physically possible to eat enough bananas to cause radiation poisoning, as the radiation dose from bananas is non-cumulative. Radiation is ubiquitous on Earth, and humans are adapted to survive at the normal low-to-moderate levels of radiation found on Earth's surface. The relationship between dose and toxicity is often non-linear, and many substances that are toxic at very high doses actually have neutral or positive health effects, or are biologically essential, at moderate or low doses. There is some evidence to suggest that this is true for ionizing radiation: normal levels of ionizing radiation may serve to stimulate and regulate the activity of DNA repair mechanisms. High enough levels of any kind of radiation will eventually become lethal, however. Ionizing radiation in certain conditions can damage living organisms, causing cancer or genetic damage. Non-ionizing radiation in certain


id: ramsauer-townsend-effect-20260505-0
file: data/en.wikipedia.org/wiki/Ramsauer–Townsend_effect-0.md
category: reference
title: Ramsauer–Townsend effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ramsauer–Townsend_effect
date_saved: 2026-05-05T10:56:05.733364+00:00
instance: kb-cron
parent: ramsauer-townsend-effect-20260505-0
summary:
The Ramsauer–Townsend effect, also sometimes called the Ramsauer effect or the Townsend effect, is a physical phenomenon involving the scattering of low-energy electrons by atoms of a noble gas. This effect is a result of quantum mechanics. The effect is named for Carl Ramsauer and John Sealy Townsend, who each independently studied the collisions between atoms and low-energy electrons in 1921. == Definitions == When an electron moves through a gas, its interactions with the gas atoms cause scattering to occur. These interactions are classified as inelastic if they cause excitation or ionization of the atom to occur or elastic if they do not. The probability of scattering in such a system is defined as the number of electrons scattered, per unit electron current, per unit path length, per unit pressure at 0 °C, per unit solid angle. The number of collisions equals the total number of electrons scattered elastically and inelastically in all angles, and the probability of collision is the total number of collisions, per unit electron current, per unit path length, per unit pressure at 0 °C. Because noble gas atoms have a relatively high first ionization energy and the electrons do not carry enough energy to


id: rayleigh-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Rayleigh_scattering-0.md
category: reference
title: Rayleigh scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rayleigh_scattering
date_saved: 2026-05-05T10:56:07.297744+00:00
instance: kb-cron
parent: rayleigh-scattering-20260505-0
summary:
Rayleigh scattering ( RAY-lee) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering medium (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength (e.g., a blue color is scattered much more than a red color as light propagates through air). The phenomenon is named after the 19th-century British physicist Lord Rayleigh (John William Strutt). Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering of sunlight in Earth's atmosphere causes diffuse sky radiation. Since blue light wavelengths scatter more, the diffuse sky seen in daytime is blue. At twilight the sunlight on the horizon is missing the scattered blue light


id: rayleigh-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Rayleigh_scattering-1.md
category: reference
title: Rayleigh scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rayleigh_scattering
date_saved: 2026-05-05T10:56:07.297744+00:00
instance: kb-cron
parent: rayleigh-scattering-20260505-0
summary:
I s = I 0 π 2 α 2 ε 0 2 λ 4 R 2 1 + cos 2 ⁡ θ 2 . {\displaystyle I_{s}=I_{0}{\frac {\pi ^{2}\alpha ^{2}}{{\varepsilon _{0}}^{2}\lambda ^{4}R^{2}}}{\frac {1+\cos ^{2}\theta }{2}}.} == Effect of fluctuations == When the dielectric constant ϵ {\displaystyle \epsilon } of a certain region of volume V {\displaystyle V} is different from the average dielectric constant of the medium ϵ ¯ {\displaystyle {\bar {\epsilon }}} , then any incident light will be scattered according to the following equation I = I 0 π 2 V 2 σ ϵ 2 2 λ 4 R 2 ( 1 + cos 2 ⁡ θ ) {\displaystyle I=I_{0}{\frac {\pi ^{2}V^{2}\sigma _{\epsilon }^{2}}{2\lambda ^{4}R^{2}}}{\left(1+\cos ^{2}\theta \right)}} where σ ϵ 2 {\displaystyle \sigma _{\epsilon }^{2}} represents the variance of the fluctuation in the dielectric constant ϵ {\displaystyle \epsilon } . == Cause of the blue color of the sky == The blue color of the sky is a consequence of three factors: the blackbody spectrum of sunlight coming into the Earth's atmosphere, Rayleigh scattering of that light off oxygen and nitrogen molecules, and the response of the human visual system. The strong wavelength dependence of the Rayleigh scattering (~λ−4)


id: recovery-effect-20260505-0
file: data/en.wikipedia.org/wiki/Recovery_effect-0.md
category: reference
title: Recovery effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Recovery_effect
date_saved: 2026-05-05T10:56:08.762744+00:00
instance: kb-cron
parent: recovery-effect-20260505-0
summary:
The recovery effect is a phenomenon observed in battery usage where the available energy is less than the difference between energy charged and energy consumed. == Mechanism == Intuitively, this is because the energy has been consumed from the edge of the battery and the charge has not yet diffused evenly around the battery. When power is extracted continuously voltage decreases in a smooth curve, but the recovery effect can result in the voltage partially increasing if the current is interrupted. == In non-lead-acid batteries == The KiBaM battery model describes the recovery effect for lead-acid batteries and is also a good approximation to the observed effects in Li-ion batteries. In some batteries, the gains from the recovery life can extend battery life by up to 45% by alternating discharging and inactive periods rather than constantly discharging. The size of the recovery effect depends on the battery load, recovery time and depth of discharge. Even though the recovery effect phenomenon is prominent in the lead acid battery chemistry, its existence in alkaline, Ni-MH and Li-Ion batteries is still questionable. For instance, a systematic experimental case study shows that an intermittent discharge current in case of alkaline, Ni-MH and Li-ion batteries


id: reflection-physics-20260505-0
file: data/en.wikipedia.org/wiki/Reflection_(physics)-0.md
category: reference
title: Reflection (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reflection_(physics)
date_saved: 2026-05-05T10:56:09.994224+00:00
instance: kb-cron
parent: reflection-physics-20260505-0
summary:
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. == Reflection of light == Reflection of light is either specular (mirror-like) or diffuse (retaining the energy, but losing the image) depending on the nature of the interface. In specular reflection the phase of the reflected waves depends on the choice of the origin of coordinates, but the relative phase between s and p (TE


id: reflection-physics-20260505-1
file: data/en.wikipedia.org/wiki/Reflection_(physics)-1.md
category: reference
title: Reflection (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reflection_(physics)
date_saved: 2026-05-05T10:56:09.994224+00:00
instance: kb-cron
parent: reflection-physics-20260505-0
summary:
In classical electrodynamics, light is considered as an electromagnetic wave, which is described by Maxwell's equations. Light waves incident on a material induce small oscillations of polarisation in the individual atoms (or oscillation of electrons, in metals), causing each particle to radiate a small secondary wave in all directions, like a dipole antenna. All these waves add up to give specular reflection and refraction, according to the Huygens–Fresnel principle. In the case of dielectrics such as glass, the electric field of the light acts on the electrons in the material, and the moving electrons generate fields and become new radiators. The refracted light in the glass is the combination of the forward radiation of the electrons and the incident light. The reflected light is the combination of the backward radiation of all of the electrons. In metals, electrons with no binding energy are called free electrons. When these electrons oscillate with the incident light, the phase difference between their radiation field and the incident field is π radians (180°), so the forward radiation cancels the incident light, and backward radiation is just the reflected light. Light–matter interaction in terms of photons is a topic of quantum electrodynamics, and is described


id: reflection-physics-20260505-2
file: data/en.wikipedia.org/wiki/Reflection_(physics)-2.md
category: reference
title: Reflection (physics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reflection_(physics)
date_saved: 2026-05-05T10:56:09.994224+00:00
instance: kb-cron
parent: reflection-physics-20260505-0
summary:
When a longitudinal sound wave strikes a flat surface, sound is reflected in a coherent manner provided that the dimension of the reflective surface is large compared to the wavelength of the sound. Note that audible sound has a very wide frequency range (from 20 to about 17000 Hz), and thus a very wide range of wavelengths (from about 20 mm to 17 m). As a result, the overall nature of the reflection varies according to the texture and structure of the surface. For example, porous materials will absorb some energy, and rough materials (where rough is relative to the wavelength) tend to reflect in many directions—to scatter the energy, rather than to reflect it coherently. This leads into the field of architectural acoustics, because the nature of these reflections is critical to the auditory feel of a space. In the theory of exterior noise mitigation, reflective surface size mildly detracts from the concept of a noise barrier by reflecting some of the sound into the opposite direction. Sound reflection can affect the acoustic space. === Seismic reflection === Seismic waves produced by earthquakes or other sources (such as explosions) may be reflected by layers within the Earth. Study of


id: refraction-20260505-0
file: data/en.wikipedia.org/wiki/Refraction-0.md
category: reference
title: Refraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refraction
date_saved: 2026-05-05T10:56:11.224500+00:00
instance: kb-cron
parent: refraction-20260505-0
summary:
In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed. Optical prisms and lenses use refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly. This is called dispersion and allows certain prisms and raindrops in rainbows to divide white light into its constituent spectral colors. == Law == For light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence θ 1 {\displaystyle {\theta _{1}}} and angle of refraction θ 2 {\displaystyle {\theta _{2}}} is equal to the ratio of phase velocities v 1 v 2 {\textstyle {\frac {v_{1}}{v_{2}}}} in


id: refraction-20260505-1
file: data/en.wikipedia.org/wiki/Refraction-1.md
category: reference
title: Refraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refraction
date_saved: 2026-05-05T10:56:11.224500+00:00
instance: kb-cron
parent: refraction-20260505-0
summary:
The phenomenon of refraction can in a more fundamental way be derived from the 2 or 3-dimensional wave equation. The boundary condition at the interface will then require the tangential component of the wave vector to be identical on the two sides of the interface. Since the magnitude of the wave vector depend on the wave speed this requires a change in direction of the wave vector. The relevant wave speed in the discussion above is the phase velocity of the wave. This is typically close to the group velocity which can be seen as the truer speed of a wave, but when they differ it is important to use the phase velocity in all calculations relating to refraction. A wave traveling perpendicular to a boundary, i.e. having its wavefronts parallel to the boundary, will not change direction even if the speed of the wave changes. === Dispersion of light === Refraction is also responsible for rainbows and for the splitting of white light into a rainbow-spectrum as it passes through a glass prism. Glass and water have higher refractive indexes than air. When a beam of white light passes from air into a material having an index of refraction


id: revolving-rivers-20260505-0
file: data/en.wikipedia.org/wiki/Revolving_rivers-0.md
category: reference
title: Revolving rivers
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Revolving_rivers
date_saved: 2026-05-05T10:56:12.432363+00:00
instance: kb-cron
parent: revolving-rivers-20260505-0
summary:
Revolving rivers are a surprising, uncommon way of sand pile growth that can be found in a few sands around the world, but has been studied in detail only for one Cuban sand from a place called Santa Teresa (Pinar del Rio province). == Description == When pouring "revolving" sand on a flat surface from a fixed position, the growth of a conical pile does not occur by the common avalanche mechanism, where sand slides down the pile in a more or less random fashion. What happens is that a relatively thin "river" of flowing sand travels from the pouring point at the apex of the pile to its base, while the rest of the sand at the surface is static. In addition, the river "revolves" around the pile either in clockwise or counter-clockwise directions (looking from top) depending on the initial conditions. Actually the river constitutes the "cutting edge" of a layer of sand that deposits as a helix on the conical pile, and makes it grow. For small sandpiles, rivers are continuous, but they become intermittent for larger piles. == History and state of the art == The phenomenon was observed first by E. Altshuler at the University


id: scattering-20260505-0
file: data/en.wikipedia.org/wiki/Scattering-0.md
category: reference
title: Scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scattering
date_saved: 2026-05-05T10:56:13.653453+00:00
instance: kb-cron
parent: scattering-20260505-0
summary:
In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections of radiation that undergo scattering are often called diffuse reflections and unscattered reflections are called specular (mirror-like) reflections. Originally, the term was confined to light scattering (going back at least as far as Isaac Newton in the 17th century). As more "ray"-like phenomena were discovered, the idea of scattering was extended to them, so that William Herschel could refer to the scattering of "heat rays" (not then recognized as electromagnetic in nature) in 1800. John Tyndall, a pioneer in light scattering research, noted the connection between light scattering and acoustic scattering in the 1870s. Near the end of the 19th century, the scattering of cathode rays (electron beams) and X-rays was observed and discussed. With the discovery of subatomic particles (e.g. Ernest Rutherford in 1911) and the development of quantum theory in the 20th century,


id: scattering-20260505-1
file: data/en.wikipedia.org/wiki/Scattering-1.md
category: reference
title: Scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scattering
date_saved: 2026-05-05T10:56:13.653453+00:00
instance: kb-cron
parent: scattering-20260505-0
summary:
Scattering theory is a framework for studying and understanding the scattering of waves and particles. Wave scattering corresponds to the collision and scattering of a wave with some material object, for instance sunlight scattered by rain drops to form a rainbow. Scattering also includes the interaction of billiard balls on a table, the Rutherford scattering (or angle change) of alpha particles by gold nuclei, the Bragg scattering (or diffraction) of electrons and X-rays by a cluster of atoms, and the inelastic scattering of a fission fragment as it traverses a thin foil. More precisely, scattering consists of the study of how solutions of partial differential equations, propagating freely "in the distant past", come together and interact with one another or with a boundary condition, and then propagate away "to the distant future". The direct scattering problem is the problem of determining the distribution of scattered radiation/particle flux basing on the characteristics of the scatterer. The inverse scattering problem is the problem of determining the characteristics of an object (e.g., its shape, internal constitution) from measurement data of radiation or particles scattered from the object. === Attenuation due to scattering === When the target is a set of many scattering centers


id: scattering-20260505-2
file: data/en.wikipedia.org/wiki/Scattering-2.md
category: reference
title: Scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scattering
date_saved: 2026-05-05T10:56:13.653453+00:00
instance: kb-cron
parent: scattering-20260505-0
summary:
In mathematical physics, scattering theory is a framework for studying and understanding the interaction or scattering of solutions to partial differential equations. In acoustics, the differential equation is the wave equation, and scattering studies how its solutions, the sound waves, scatter from solid objects or propagate through non-uniform media (such as sound waves, in sea water, coming from a submarine). In the case of classical electrodynamics, the differential equation is again the wave equation, and the scattering of light or radio waves is studied. In particle physics, the equations are those of Quantum electrodynamics, Quantum chromodynamics and the Standard Model, the solutions of which correspond to fundamental particles. In regular quantum mechanics, which includes quantum chemistry, the relevant equation is the Schrödinger equation, although equivalent formulations, such as the Lippmann-Schwinger equation and the Faddeev equations, are also largely used. The solutions of interest describe the long-term motion of free atoms, molecules, photons, electrons, and protons. The scenario is that several particles come together from an infinite distance away. These reagents then collide, optionally reacting, getting destroyed or creating new particles. The products and unused reagents then fly away to infinity again. (The atoms and molecules are effectively particles for our


id: scattering-20260505-3
file: data/en.wikipedia.org/wiki/Scattering-3.md
category: reference
title: Scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scattering
date_saved: 2026-05-05T10:56:13.653453+00:00
instance: kb-cron
parent: scattering-20260505-0
summary:
α ≪ 1: Rayleigh scattering (small particle compared to wavelength of light); α ≈ 1: Mie scattering (particle about the same size as wavelength of light, valid only for spheres); α ≫ 1: geometric scattering (particle much larger than wavelength of light). Rayleigh scattering is a process in which electromagnetic radiation (including light) is scattered by a small spherical volume of variant refractive indexes, such as a particle, bubble, droplet, or even a density fluctuation. This effect was first modeled successfully by Lord Rayleigh, from whom it gets its name. In order for Rayleigh's model to apply, the sphere must be much smaller in diameter than the wavelength (λ) of the scattered wave; typically the upper limit is taken to be about 1/10 the wavelength. In this size regime, the exact shape of the scattering center is usually not very significant and can often be treated as a sphere of equivalent volume. The inherent scattering that radiation undergoes passing through a pure gas is due to microscopic density fluctuations as the gas molecules move around, which are normally small enough in scale for Rayleigh's model to apply. This scattering mechanism is the primary cause of the blue color of the


id: self-oscillation-20260505-0
file: data/en.wikipedia.org/wiki/Self-oscillation-0.md
category: reference
title: Self-oscillation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Self-oscillation
date_saved: 2026-05-05T10:56:14.848602+00:00
instance: kb-cron
parent: self-oscillation-20260505-0
summary:
Self-oscillation is the generation and maintenance of a periodic motion by a source of power that lacks any corresponding periodicity. The oscillator itself controls the phase with which the external power acts on it. Self-oscillators are therefore distinct from forced and parametric resonators, in which the power that sustains the motion must be modulated externally. In linear systems, self-oscillation appears as an instability associated with a negative damping term, which causes small perturbations to grow exponentially in amplitude. This negative damping is due to a positive feedback between the oscillation and the modulation of the external source of power. The amplitude and waveform of steady self-oscillations are determined by the nonlinear characteristics of the system. Self-oscillations are important in physics, engineering, biology, and economics. == History of the subject == The study of self-oscillators dates back to the early 1830s, with the work of Robert Willis and George Biddell Airy on the mechanism by which the vocal cords produce the human voice. Another instance of self-oscillation, associated with the unstable operation of centrifugal governors, was studied mathematically by James Clerk Maxwell in 1867. In the second edition of his treatise on The Theory of Sound, published in 1896, Lord Rayleigh


id: shock-diamond-20260505-0
file: data/en.wikipedia.org/wiki/Shock_diamond-0.md
category: reference
title: Shock diamond
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shock_diamond
date_saved: 2026-05-05T10:56:16.046807+00:00
instance: kb-cron
parent: shock-diamond-20260505-0
summary:
Shock diamonds (also known as Mach diamonds or thrust diamonds, and less commonly Mach disks) are a formation of standing wave patterns that appear in the supersonic exhaust plume of an aerospace propulsion system, such as a supersonic jet engine, rocket, ramjet, or scramjet, when it is operated in an atmosphere. The "diamonds" are actually a complex flow field made visible by abrupt changes in local density and pressure as the exhaust passes through a series of standing shock waves and expansion fans. The physicist Ernst Mach was the first to describe a strong shock perpendicular to the direction of fluid flow, the presence of which causes the diamond pattern. == Mechanism == Shock diamonds form when the supersonic exhaust from a propelling nozzle is slightly over-expanded, meaning that the static pressure of the gases exiting the nozzle is less than the ambient air pressure. The higher ambient pressure compresses the flow, and since the resulting pressure increase in the exhaust gas stream is adiabatic, a reduction in velocity causes its static temperature to be substantially increased. The exhaust is typically over-expanded at low altitudes where air pressure is higher. As the flow exits the nozzle, ambient air pressure will


id: singing-sand-20260505-0
file: data/en.wikipedia.org/wiki/Singing_sand-0.md
category: reference
title: Singing sand
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Singing_sand
date_saved: 2026-05-05T10:56:18.398176+00:00
instance: kb-cron
parent: singing-sand-20260505-0
summary:
Singing sand, also called whistling sand, barking sand, booming sand or singing dune, is sand that produces sound. The sound emission may be caused by wind passing over dunes or by walking on the sand. Certain conditions have to come together to create singing sand: The sand grains have to be round and between 0.1 and 0.5 mm in diameter. The sand has to contain silica. The sand needs to be at a certain humidity. The most common frequency emitted seems to be close to 450 Hz. There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency of vibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer, creating a resonance that increases the sound's volume. The noise may be generated by friction between the grains or by the compression of air between them. Other sounds that can be emitted by sand have been described as "roaring" or "booming". == In dunes == Singing sand dunes, an example


id: singing-sand-20260505-1
file: data/en.wikipedia.org/wiki/Singing_sand-1.md
category: reference
title: Singing sand
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Singing_sand
date_saved: 2026-05-05T10:56:18.398176+00:00
instance: kb-cron
parent: singing-sand-20260505-0
summary:
== Literature == Nori, Franco; Sholtz, Paul; Bretz, Michael (1997). "Booming Sand". Scientific American. 277 (3): 84–89. Bibcode:1997SciAm.277c..84N. doi:10.1038/scientificamerican0997-84. JSTOR 24995915. Sholtz, Paul; Bretz, Michael; Nori, Franco (1997). "Sound-producing sand avalanches" (PDF). Contemporary Physics. 38 (5): 329–342. Bibcode:1997ConPh..38..329S. doi:10.1080/001075197182306. Ridgeway, K.; Scotton, J. B. (1973). "Whistling sand beaches in the British Isles". Sedimentology. 20 (2). Wiley: 263–279. Bibcode:1973Sedim..20..263R. doi:10.1111/j.1365-3091.1973.tb02049.x. ISSN 0037-0746. Andreotti, B. (2004-12-01). "The Song of Dunes as a Wave-Particle Mode Locking". Physical Review Letters. 93 (23) 238001. American Physical Society (APS). Bibcode:2004PhRvL..93w8001A. doi:10.1103/physrevlett.93.238001. ISSN 0031-9007. PMID 15601204. Douady, S.; Manning, A.; Hersen, P.; Elbelrhiti, H.; Protière, S.; Daerr, A.; Kabbachi, B. (2006-07-07). "Song of the Dunes as a Self-Synchronized Instrument". Physical Review Letters. 97 (1) 018002. American Physical Society (APS). arXiv:nlin/0412047. Bibcode:2006PhRvL..97a8002D. doi:10.1103/physrevlett.97.018002. ISSN 0031-9007. PMID 16907409. S2CID 19628505. Bonneau, L.; Andreotti, B.; Clément, E. (2007-01-08). "Surface elastic waves in granular media under gravity and their relation to booming avalanches". Physical Review E. 75 (1) 016602. American Physical Society (APS). Bibcode:2007PhRvE..75a6602B. doi:10.1103/physreve.75.016602. ISSN 1539-3755. PMID 17358270. Vriend, Nathalie M.; Hunt, Melany L.; Clayton, Robert W.; Brennen, Christopher Earls; Brantley, Katherine S.; Ruiz-Angulo, Angel (2007-08-23). "Solving the mystery of booming sand dunes". Geophysical Research Letters. 34 (16). American Geophysical


id: singing-sand-dunes-dunhuang-20260505-0
file: data/en.wikipedia.org/wiki/Singing_Sand_Dunes_(Dunhuang)-0.md
category: reference
title: Singing Sand Dunes (Dunhuang)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Singing_Sand_Dunes_(Dunhuang)
date_saved: 2026-05-05T10:56:19.612042+00:00
instance: kb-cron
parent: singing-sand-dunes-dunhuang-20260505-0
summary:
The Singing Sand Dunes (Chinese: 鳴沙山 Pinyin: míng shā shān) in Dunhuang, China, are the sand dunes that, when the wind blows, give out a singing or drumming sound. They are part of the Kumtag Desert. The Singing Sand Dunes were originally known as the "Gods' Sand Dunes" (Chinese: 神沙山). In the Records of the Grand Historian, Sima Qian described the sound "as if listening to music when the weather is fine." During the Ming Dynasty, they came to be called by the current name. The dunes are also where a crescent-shaped lake called Yueyaquan or Crescent Lake is located. There are four better-known singing sand dunes in China, that include those of Hami, which are usually said to give the best sound among the four, and those of Dunhuang. The tourist area at the site offers various facilities and activities such as ATV riding, paragliding, camel rides and sandboarding. == See also == Singing sand Mogao Caves: nearby == References ==


id: sommerfeld-effect-20260505-0
file: data/en.wikipedia.org/wiki/Sommerfeld_effect-0.md
category: reference
title: Sommerfeld effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sommerfeld_effect
date_saved: 2026-05-05T10:56:20.820359+00:00
instance: kb-cron
parent: sommerfeld-effect-20260505-0
summary:
In mechanics, Sommerfeld effect is a phenomenon arising from feedback in the energy exchange between vibrating systems: for example, when for the rocking table, under given conditions, energy transmitted to the motor resulted not in higher revolutions but in stronger vibrations of the table. It is named after Arnold Sommerfeld. In 1902, A. Sommerfeld analyzed the vibrations caused by a motor driving an unbalanced weight and wrote that "This experiment corresponds roughly to the case in which a factory owner has a machine set on a poor foundation running at 30 horsepower. He achieves an effective level of just 1/3, however, because only 10 horsepower are doing useful work, while 20 horsepower are transferred to the foundational masonry". First mathematical descriptions of Sommerfeld effect were suggested by I. Blekhman and V. Kononenko. == Hidden attractors in Sommerfeld effect == In the theory of hidden oscillations, Sommerfeld effect is explained by the multistability and presence in the phase space of dynamical model without stationary states of two coexisting hidden attractors, one of which attracts trajectories from vicinity of zero initial data (which correspond to the typical start up of the motor), and the other attractor corresponds to the desired mode of


id: sonochemical-synthesis-20260505-0
file: data/en.wikipedia.org/wiki/Sonochemical_synthesis-0.md
category: reference
title: Sonochemical synthesis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sonochemical_synthesis
date_saved: 2026-05-05T10:56:22.002477+00:00
instance: kb-cron
parent: sonochemical-synthesis-20260505-0
summary:
Sonochemical synthesis is the process which utilizes the principles of sonochemistry to make molecules undergo a chemical reaction with the application of powerful ultrasound radiation (20 kHz–10 MHz). Sonochemistry generates hot spots that can achieve very high temperatures (5000–25.000 K), pressures of more than 1000 atmospheres, and rates of heating and cooling that can exceed 10^11 K/s. High intensity ultrasound produces chemical and physical effects that can be used for the production or modification of a wide range of nanostructured materials. The principle that causes the modification of nanostructures in the sonochemical process is acoustic cavitation. == References ==


id: sonochemistry-20260505-0
file: data/en.wikipedia.org/wiki/Sonochemistry-0.md
category: reference
title: Sonochemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sonochemistry
date_saved: 2026-05-05T10:56:23.217039+00:00
instance: kb-cron
parent: sonochemistry-20260505-0
summary:
In chemistry, the study of sonochemistry is concerned with understanding the effect of ultrasound in forming acoustic cavitation in liquids, resulting in the initiation or enhancement of the chemical activity in the solution. Therefore, the chemical effects of ultrasound do not come from a direct interaction of the ultrasonic sound wave with the molecules in the solution. == History == The influence of sonic waves travelling through liquids was first reported by Robert Williams Wood (1868–1955) and Alfred Lee Loomis (1887–1975) in 1927. The experiment was about the frequency of the energy that it took for sonic waves to "penetrate" the barrier of water. He came to the conclusion that sound does travel faster in water, but because of the water's density compared to Earth's atmosphere it was incredibly hard to get the sonic waves to couple their energy into the water. Due to the sudden density change, much of the energy is lost, similar to shining a flashlight towards a piece of glass; some of the light is transmitted into the glass, but much of it is lost to reflection outwards. Similarly with an air-water interface, almost all of the sound is reflected off the water, instead of being


id: spatial-dispersion-20260505-0
file: data/en.wikipedia.org/wiki/Spatial_dispersion-0.md
category: reference
title: Spatial dispersion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spatial_dispersion
date_saved: 2026-05-05T10:56:25.759895+00:00
instance: kb-cron
parent: spatial-dispersion-20260505-0
summary:
In the physics of continuous media, spatial dispersion is a phenomenon where material parameters such as the permittivity or conductivity have dependence on wavevector. Normally such a dependence is assumed to be absent for simplicity, however spatial dispersion exists to varying degrees in all materials. The underlying physical reason for the wavevector dependence is often that the material has some spatial structure smaller than the wavelength of any signals (such as light or sound) being considered. Since these small spatial structures cannot be resolved by the waves, only indirect effects (e.g. wavevector dependence) remain detectable. In such a case, although the light cannot resolve the individual atoms, they nevertheless can as an aggregate affect how the light propagates. Another common mechanism is that the (e.g.) light is coupled to an excitation of the material, such as a plasmon. Spatial dispersion can be compared to temporal dispersion, the latter often just called dispersion. Temporal dispersion represents memory effects in systems, commonly seen in optics and electronics. Spatial dispersion on the other hand represents spreading effects and is usually significant only at microscopic length scales. Spatial dispersion contributes relatively small perturbations to optics, providing weak effects such as optical activity. Spatial dispersion


id: spatial-dispersion-20260505-1
file: data/en.wikipedia.org/wiki/Spatial_dispersion-1.md
category: reference
title: Spatial dispersion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spatial_dispersion
date_saved: 2026-05-05T10:56:25.759895+00:00
instance: kb-cron
parent: spatial-dispersion-20260505-0
summary:
ω 2 μ 0 ϵ ( k → , ω ) E → − ( k → ⋅ k → ) E → + ( k → ⋅ E → ) k → = 0. {\displaystyle \omega ^{2}\mu _{0}\epsilon ({\vec {k}},\omega ){\vec {E}}-({\vec {k}}\cdot {\vec {k}}){\vec {E}}+({\vec {k}}\cdot {\vec {E}}){\vec {k}}=0.} Spatial dispersion in ϵ ( k → , ω ) {\displaystyle \epsilon ({\vec {k}},\omega )} can lead to strange phenomena, such as the existence of multiple modes at the same frequency and wavevector direction, but with different wavevector magnitudes. Nearby crystal surfaces and boundaries, it is no longer valid to describe system response in terms of wavevectors. For a full description it is necessary to return to a full nonlocal response function (without translational symmetry), however the end effect can sometimes be described by "additional boundary conditions" (ABC's). === In isotropic media === In materials that have no relevant crystalline structure, spatial dispersion can be important. Although symmetry demands that the permittivity is isotropic for zero wavevector, this restriction does not apply for nonzero wavevector. The non-isotropic permittivity for nonzero wavevector leads to effects such as optical activity in solutions of chiral molecules. In isotropic materials without optical activity,


id: spontaneous-emission-20260505-0
file: data/en.wikipedia.org/wiki/Spontaneous_emission-0.md
category: reference
title: Spontaneous emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spontaneous_emission
date_saved: 2026-05-05T10:56:26.913707+00:00
instance: kb-cron
parent: spontaneous-emission-20260505-0
summary:
Spontaneous emission is the process in which a quantum mechanical system (such as a molecule, an atom or a subatomic particle) transitions from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon. If the system in question is excited by some means other than heating, the spontaneous emission is called luminescence. There are different sub-categories of luminescence depending on how excited atoms are produced (electroluminescence, chemiluminescence etc.). If the excitation is affected by the absorption of radiation the spontaneous emission is called fluorescence. Some systems have a metastable level and continue to fluoresce long after the exciting radiation is turned off; this is called phosphorescence. Lasers start via spontaneous emission, then during continuous operation work by stimulated emission. Spontaneous emission cannot be explained by classical electromagnetic theory and is fundamentally a quantum process. Albert Einstein first predicted the phenomenon of spontaneous emission in a series of papers starting in 1916, culminating in what is now called the Einstein A Coefficient. Einstein's quantum theory of radiation anticipated ideas later expressed in quantum electrodynamics and quantum optics by several decades. Later, after the formal discovery


id: spontaneous-emission-20260505-1
file: data/en.wikipedia.org/wiki/Spontaneous_emission-1.md
category: reference
title: Spontaneous emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spontaneous_emission
date_saved: 2026-05-05T10:56:26.913707+00:00
instance: kb-cron
parent: spontaneous-emission-20260505-0
summary:
== Theory == Spontaneous transitions cannot be modeled with a classical electromagnetic field, even with quantum-mechanical treatment of the atom. The stationary quantum states of an atom are orthogonal: the overlap of the wavefunctions between an excited state and the ground state of the atom is zero. Thus, in the absence of a quantized electromagnetic field operator, the excited state atom cannot decay to the ground state. In order to explain spontaneous transitions, quantum mechanics must be extended to a quantum field theory, wherein the electromagnetic field is quantized at every point in space. The quantum field theory of electrons and electromagnetic fields is known as quantum electrodynamics. In quantum electrodynamics (or QED), the electromagnetic field has a ground state, the QED vacuum, which can mix with the excited stationary states of the atom. As a result of this interaction, the stationary state of the atom is no longer a eigenstate of the combined system of the atom plus electromagnetic field. The transition from the electronic excited state to the electronic ground state mixes with the transition of the electromagnetic field from the ground state to an excited state, a field state with one photon in it. Spontaneous emission in


id: spontaneous-emission-20260505-2
file: data/en.wikipedia.org/wiki/Spontaneous_emission-2.md
category: reference
title: Spontaneous emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spontaneous_emission
date_saved: 2026-05-05T10:56:26.913707+00:00
instance: kb-cron
parent: spontaneous-emission-20260505-0
summary:
where ω {\displaystyle \omega } is the emission frequency, n {\displaystyle n} is the index of refraction, μ 12 {\displaystyle \mu _{12}} is the transition dipole moment, ε 0 {\displaystyle \varepsilon _{0}} is the vacuum permittivity, ℏ {\displaystyle \hbar } is the reduced Planck constant, c {\displaystyle c} is the vacuum speed of light, and α {\displaystyle \alpha } is the fine-structure constant. The expression | ⟨ 1 | r | 2 ⟩ | {\displaystyle |\langle 1|\mathbf {r} |2\rangle |} stands for the definition of the transition dipole moment | μ 12 | = | ⟨ 1 | d | 2 ⟩ | {\displaystyle |\mu _{12}|=|\langle 1|\mathbf {d} |2\rangle |} for dipole moment operator d = q r {\displaystyle \mathbf {d} =q\mathbf {r} } , where q {\displaystyle q} is the elementary charge and r {\displaystyle \mathbf {r} } stands for position operator. (This approximation breaks down in the case of inner shell electrons in high-Z atoms.) The above equation clearly shows that the rate of spontaneous emission in free space increases proportionally to ω 3 {\displaystyle \omega ^{3}} . In contrast with atoms, which have a discrete emission spectrum, quantum dots can be tuned continuously by changing their size.


id: stark-effect-20260505-0
file: data/en.wikipedia.org/wiki/Stark_effect-0.md
category: reference
title: Stark effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stark_effect
date_saved: 2026-05-05T10:56:28.115020+00:00
instance: kb-cron
parent: stark-effect-20260505-0
summary:
The Stark effect is the shifting and splitting of spectral lines of atoms and molecules due to the presence of an external electric field. It is the electric-field analogue of the Zeeman effect, where a spectral line is split into several components due to the presence of the magnetic field. Although initially coined for the static case, it is also used in the wider context to describe the effect of time-dependent electric fields. In particular, the Stark effect is responsible for the pressure broadening (Stark broadening) of spectral lines by charged particles in plasmas. For most spectral lines, the Stark effect is either linear (proportional to the applied electric field) or quadratic with a high accuracy. The Stark effect can be observed both for emission and absorption lines. The latter was sometimes called the inverse Stark effect, but this term is no longer used in the modern literature. == History == The effect is named after the German physicist Johannes Stark, who discovered it in 1913. It was independently discovered in the same year by the Italian physicist Antonino Lo Surdo. The discovery of this effect contributed importantly to the development of quantum theory and Stark was awarded with the


id: stark-effect-20260505-1
file: data/en.wikipedia.org/wiki/Stark_effect-1.md
category: reference
title: Stark effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stark_effect
date_saved: 2026-05-05T10:56:28.115020+00:00
instance: kb-cron
parent: stark-effect-20260505-0
summary:
where q {\displaystyle q} and μ {\displaystyle {\boldsymbol {\mu }}} are, respectively, the total charge (zero moment) and the dipole moment of the charge distribution. Classical macroscopic objects are usually neutral or quasi-neutral ( q = 0 {\displaystyle q=0} ), so the first, monopole, term in the expression above is identically zero. This is also the case for a neutral atom or molecule. However, for an ion this is no longer true. Nevertheless, it is often justified to omit it in this case, too. Indeed, the Stark effect is observed in spectral lines, which are emitted when an electron "jumps" between two bound states. Since such a transition only alters the internal degrees of freedom of the radiator but not its charge, the effects of the monopole interaction on the initial and final states exactly cancel each other. === Perturbation theory === Turning now to quantum mechanics an atom or a molecule can be thought of as a collection of point charges (electrons and nuclei), so that the second definition of the dipole applies. The interaction of atom or molecule with a uniform external field is described by the operator V i n t = − F ⋅ μ .


id: stark-effect-20260505-2
file: data/en.wikipedia.org/wiki/Stark_effect-2.md
category: reference
title: Stark effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stark_effect
date_saved: 2026-05-05T10:56:28.115020+00:00
instance: kb-cron
parent: stark-effect-20260505-0
summary:
E k ( 2 ) = ∑ k ′ ≠ k ⟨ ψ k 0 | V i n t | ψ k ′ 0 ⟩ ⟨ ψ k ′ 0 | V i n t | ψ k 0 ⟩ E k ( 0 ) − E k ′ ( 0 ) ≡ − 1 2 ∑ i , j = 1 3 α i j F i F j {\displaystyle E_{k}^{(2)}=\sum _{k'\neq k}{\frac {\langle \psi _{k}^{0}|V_{\mathrm {int} }|\psi _{k^{\prime }}^{0}\rangle \langle \psi _{k'}^{0}|V_{\mathrm {int} }|\psi _{k}^{0}\rangle }{E_{k}^{(0)}-E_{k'}^{(0)}}}\equiv -{\frac {1}{2}}\sum _{i,j=1}^{3}\alpha _{ij}F_{i}F_{j}} with the components of the polarizability tensor α defined by α i j = − 2 ∑ k ′ ≠ k ⟨ ψ k 0 | μ i | ψ k ′ 0 ⟩ ⟨ ψ k ′ 0 | μ j | ψ k 0 ⟩ E k ( 0 ) − E k ′ ( 0 ) . {\displaystyle \alpha _{ij}=-2\sum _{k'\neq k}{\frac {\langle \psi _{k}^{0}|\mu _{i}|\psi _{k'}^{0}\rangle \langle \psi _{k'}^{0}|\mu _{j}|\psi _{k}^{0}\rangle }{E_{k}^{(0)}-E_{k'}^{(0)}}}.} The energy E(2) gives the quadratic Stark effect. Neglecting the hyperfine structure (which is often justified — unless extremely weak electric fields are considered), the polarizability tensor of atoms is isotropic,


id: stimulated-emission-20260505-0
file: data/en.wikipedia.org/wiki/Stimulated_emission-0.md
category: reference
title: Stimulated emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stimulated_emission
date_saved: 2026-05-05T10:56:29.293495+00:00
instance: kb-cron
parent: stimulated-emission-20260505-0
summary:
Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to the electromagnetic field, creating a new photon with a frequency, polarization, and direction of travel that are all identical to the photons of the incident wave. This is in contrast to spontaneous emission, which occurs at a characteristic rate for each of the atoms/oscillators in the upper energy state regardless of the external electromagnetic field. According to the American Physical Society, the first person to correctly predict the phenomenon of stimulated emission was Albert Einstein in a series of papers starting in 1916, culminating in what is now called the Einstein B Coefficient. Einstein's work became the theoretical foundation of the maser and the laser. The process is identical in form to atomic absorption in which the energy of an absorbed photon causes an identical but opposite atomic transition: from the lower level to a higher energy level. In normal media at thermal equilibrium, absorption exceeds stimulated emission because there are more electrons in the lower energy states than in


id: stimulated-emission-20260505-1
file: data/en.wikipedia.org/wiki/Stimulated_emission-1.md
category: reference
title: Stimulated emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stimulated_emission
date_saved: 2026-05-05T10:56:29.293495+00:00
instance: kb-cron
parent: stimulated-emission-20260505-0
summary:
where the proportionality constant B21 is known as the Einstein B coefficient for that particular transition, and ρ(ν) is the radiation density of the incident field at frequency ν. The rate of emission is thus proportional to the number of atoms in the excited state N2, and to the density of incident photons. At the same time, there will be a process of atomic absorption which removes energy from the field while raising electrons from the lower state to the upper state. Its rate is precisely the negative of the stimulated emission rate, ∂ N 2 ∂ t = − ∂ N 1 ∂ t = B 12 ρ ( ν ) N 1 . {\displaystyle {\frac {\partial N_{2}}{\partial t}}=-{\frac {\partial N_{1}}{\partial t}}=B_{12}\,\rho (\nu )\,N_{1}.} The rate of absorption is thus proportional to the number of atoms in the lower state, N1. The B coefficients can be calculated using dipole approximation and time dependent perturbation theory in quantum mechanics as: B a b = e 2 6 ϵ 0 ℏ 2 | ⟨ a | r → | b ⟩ | 2 {\displaystyle B_{ab}={\frac {e^{2}}{6\epsilon _{0}\hbar ^{2}}}|\langle a|{\vec {r}}|b\rangle |^{2}} where B corresponds to energy distribution in terms of frequency


id: stimulated-emission-20260505-2
file: data/en.wikipedia.org/wiki/Stimulated_emission-2.md
category: reference
title: Stimulated emission
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Stimulated_emission
date_saved: 2026-05-05T10:56:29.293495+00:00
instance: kb-cron
parent: stimulated-emission-20260505-0
summary:
== Optical amplification == Stimulated emission can provide a physical mechanism for optical amplification. If an external source of energy stimulates more than 50% of the atoms in the ground state to transition into the excited state, then what is called a population inversion is created. When light of the appropriate frequency passes through the inverted medium, the photons are either absorbed by the atoms that remain in the ground state or the photons stimulate the excited atoms to emit additional photons of the same frequency, phase, and direction. Since more atoms are in the excited state than in the ground state then an amplification of the input intensity results. The population inversion, in units of atoms per cubic metre, is Δ N 21 = N 2 − g 2 g 1 N 1 {\displaystyle \Delta N_{21}=N_{2}-{g_{2} \over g_{1}}N_{1}} where g1 and g2 are the degeneracies of energy levels 1 and 2, respectively. === Small signal gain equation === The intensity (in watts per square metre) of the stimulated emission is governed by the following differential equation: d I d z = σ 21 ( ν ) ⋅ Δ N 21 ⋅ I ( z ) {\displaystyle {dI \over dz}=\sigma


id: suction-20260505-0
file: data/en.wikipedia.org/wiki/Suction-0.md
category: reference
title: Suction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Suction
date_saved: 2026-05-05T10:56:30.451492+00:00
instance: kb-cron
parent: suction-20260505-0
summary:
Suction is the day-to-day term for the movement of gases or liquids along a pressure gradient with the implication that the movement occurs because the lower pressure pulls the gas or liquid. However, the forces acting in this case do not originate from just the lower pressure side, but instead from the side of the higher pressure, as a reaction to the pressure difference. When the pressure in one part of a physical system is reduced relative to another, the fluid or gas in the higher pressure region will exert a force relative to the region of lowered pressure, referred to as pressure-gradient force. If all gas or fluid is removed the result is a perfect vacuum in which the pressure is zero. Hence, no negative pressure forces can be generated. Accordingly, from a physics point of view, the objects are not pulled but pushed. == Examples == Pressure reduction may be static, as in a piston and cylinder arrangement, or dynamic, as in the case of a vacuum cleaner when air flow results in a reduced pressure region. When animals breathe, the diaphragm and muscles around the rib cage cause a change of volume in the lungs. With increasing


id: superfluidity-20260505-0
file: data/en.wikipedia.org/wiki/Superfluidity-0.md
category: reference
title: Superfluidity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Superfluidity
date_saved: 2026-05-05T10:56:32.870694+00:00
instance: kb-cron
parent: superfluidity-20260505-0
summary:
Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two isotopes of helium (helium-3 and helium-4) when they are liquefied by cooling to cryogenic temperatures. It is also a property of various other exotic states of matter theorized to exist in astrophysics, high-energy physics, and theories of quantum gravity. The semi-phenomenological theory of superfluidity was developed by Soviet theoretical physicists Lev Landau and Isaak Khalatnikov. Superfluidity often co-occurs with Bose–Einstein condensation (BEC), but neither phenomenon is directly related to the other; not all Bose–Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates. Even when superfluidity and condensation co-occur, their magnitudes are not linked: at low temperature, liquid helium has a large superfluid fraction but a low condensate fraction; while a weakly interacting BEC, with almost unity condensate fraction, can display a vanishing superfluid fraction. Superfluids have some potential practical uses, such as dissolving substances in a quantum solvent. == Superfluidity of liquid helium == Superfluidity was discovered in helium-4 by Pyotr Kapitsa and independently by John F. Allen and Don


id: thermo-dielectric-effect-20260505-0
file: data/en.wikipedia.org/wiki/Thermo-dielectric_effect-0.md
category: reference
title: Thermo-dielectric effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermo-dielectric_effect
date_saved: 2026-05-05T10:56:34.048783+00:00
instance: kb-cron
parent: thermo-dielectric-effect-20260505-0
summary:
The thermo-dielectric effect is the production of electric currents and charge separation during phase transition. This interesting effect was discovered by Joaquim da Costa Ribeiro in 1944. The Brazilian physicist observed that solidification and melting of many dielectrics are accompanied by charge separation. A thermo-dielectric effect was demonstrated with carnauba wax, naphthalene and paraffin. Charge separation in ice was also expected. This effect was observed during water freezing period, electrical storm effects can be caused by this strange phenomenon. Effect was measured by many researches - Bernhard Gross, Armando Dias Tavares, Sergio Mascarenhas etc. César Lattes (co-discoverer of the pion) supposed that this was the only effect ever to be discovered entirely in Brazil. == Further reading == Gross, B. (1954). "Theory of Thermodielectric effect". Physical Review. 94 (6): 1545–1551. Bibcode:1954PhRv...94.1545G. doi:10.1103/PhysRev.94.1545. Saldaña, Juan José (2006). Science in Latin America: a history. University of Texas Press. ISBN 978-0-292-71271-3. == External links == Thermodielectric effect measurement


id: thermoelectric-effect-20260505-0
file: data/en.wikipedia.org/wiki/Thermoelectric_effect-0.md
category: reference
title: Thermoelectric effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermoelectric_effect
date_saved: 2026-05-05T10:56:35.204054+00:00
instance: kb-cron
parent: thermoelectric-effect-20260505-0
summary:
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature difference. This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is affected by the applied voltage, thermoelectric devices can be used as temperature controllers. The term "thermoelectric effect" encompasses three separately identified effects: the Seebeck effect (temperature differences cause electromotive forces), the Peltier effect (thermocouples create temperature differences), and the Thomson effect (the Seebeck coefficient varies with temperature). The Seebeck and Peltier effects are different manifestations of the same physical process; textbooks may refer to this process as the Peltier–Seebeck effect (the separation derives from the independent discoveries by Jean Charles Athanase Peltier and Thomas Johann Seebeck). The Thomson effect is an extension of the Peltier–Seebeck model and is credited to Lord Kelvin. Joule heating, the heat that is generated whenever a current is passed through a conductive material, is not generally


id: thermoelectric-effect-20260505-1
file: data/en.wikipedia.org/wiki/Thermoelectric_effect-1.md
category: reference
title: Thermoelectric effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermoelectric_effect
date_saved: 2026-05-05T10:56:35.204054+00:00
instance: kb-cron
parent: thermoelectric-effect-20260505-0
summary:
=== Applications === In practice, thermoelectric effects are essentially unobservable for a localized hot or cold spot in a single homogeneous conducting material, since the overall EMFs from the increasing and decreasing temperature gradients will perfectly cancel out. Attaching an electrode to the hotspot in an attempt to measure the locally shifted voltage will only partly succeed: It means another temperature gradient will appear inside of the electrode, so the overall EMF will depend on the difference in Seebeck coefficients between the electrode and the conductor it is attached to. Thermocouples involve two wires, each of a different material, that are electrically joined in a region of unknown temperature. The loose ends are measured in an open-circuit state (without any current, J = 0 {\displaystyle \mathbf {J} =0} ). Although the materials' Seebeck coefficients S {\displaystyle S} are nonlinearly temperature dependent and different for the two materials, the open-circuit condition means that ∇ V = − S ∇ T {\displaystyle \nabla V=-S\nabla T} everywhere. Therefore (see the thermocouple article for more details) the voltage measured at the loose ends of the wires is directly dependent on the unknown temperature, and yet totally independent of other details such as the exact


id: thermoelectric-effect-20260505-2
file: data/en.wikipedia.org/wiki/Thermoelectric_effect-2.md
category: reference
title: Thermoelectric effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermoelectric_effect
date_saved: 2026-05-05T10:56:35.204054+00:00
instance: kb-cron
parent: thermoelectric-effect-20260505-0
summary:
== Thomson effect == For certain materials, the Seebeck coefficient is not constant in temperature, and so a spatial gradient in temperature can result in a gradient in the Seebeck coefficient. If a current is driven through this gradient, then a continuous version of the Peltier effect will occur. This Thomson effect was predicted and later observed in 1851 by Lord Kelvin (William Thomson). It describes the heating or cooling of a current-carrying conductor with a temperature gradient. If a current density J {\displaystyle \mathbf {J} } is passed through a homogeneous conductor, the Thomson effect predicts a heat production rate per unit volume. q ˙ = − K J ⋅ ∇ T , {\displaystyle {\dot {q}}=-{\mathcal {K}}\mathbf {J} \cdot \nabla T,} where ∇ T {\displaystyle \nabla T} is the temperature gradient, and K {\displaystyle {\mathcal {K}}} is the Thomson coefficient. The Thomson effect is a manifestation of the direction of flow of electrical carriers with respect to a temperature gradient within a conductor. These absorb energy (heat) flowing in a direction opposite to a thermal gradient, increasing their potential energy, and, when flowing in the same direction as a thermal gradient, they liberate heat, decreasing their potential energy. The


id: thermoelectric-effect-20260505-3
file: data/en.wikipedia.org/wiki/Thermoelectric_effect-3.md
category: reference
title: Thermoelectric effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermoelectric_effect
date_saved: 2026-05-05T10:56:35.204054+00:00
instance: kb-cron
parent: thermoelectric-effect-20260505-0
summary:
This relation expresses a subtle and fundamental connection between the Peltier and Seebeck effects. It was not satisfactorily proven until the advent of the Onsager relations, and it is worth noting that this second Thomson relation is only guaranteed for a time-reversal symmetric material; if the material is placed in a magnetic field or is itself magnetically ordered (ferromagnetic, antiferromagnetic, etc.), then the second Thomson relation does not take the simple form shown here. Now, using the second relation, the first Thomson relation becomes K = T d S d T {\displaystyle {\mathcal {K}}=T{\tfrac {dS}{dT}}} The Thomson coefficient is unique among the three main thermoelectric coefficients because it is the only one directly measurable for individual materials. The Peltier and Seebeck coefficients can only be easily determined for pairs of materials; hence, it is difficult to find values of absolute Seebeck or Peltier coefficients for an individual material. If the Thomson coefficient of a material is measured over a wide temperature range, it can be integrated using the Thomson relations to determine the absolute values for the Peltier and Seebeck coefficients. This needs to be done only for one material, since the other values can be determined by measuring pairwise


id: time-20260505-0
file: data/en.wikipedia.org/wiki/Time-0.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Time is the continuous progression of existence that occurs in an apparently irreversible succession from the past, through the present, and into the future. Time dictates all forms of action, age, and causality, being a component quantity of various measurements used to sequence events, to compare the duration of events (or the intervals between them), and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions. Time is primarily measured in linear spans or periods, ordered from shortest to longest. Practical, human-scale measurements of time are performed using clocks and calendars, reflecting a 24-hour day collected into a 365-day year linked to the astronomical motion of the Earth. Scientific measurements of time instead vary from Planck time at the shortest to billions of years at the longest. Measurable time is believed to have effectively begun with the Big Bang 13.8 billion years ago, encompassed by the chronology of the universe. Modern physics understands time to be inextricable from space within the concept of spacetime described by general relativity. Time can therefore be dilated by velocity and matter to pass faster or


id: time-20260505-1
file: data/en.wikipedia.org/wiki/Time-1.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Artifacts from the Paleolithic suggest that the moon was being used to reckon time by at least 6,000 years ago. Lunar calendars were among the first to appear, with years of either 12 or 13 lunar months (either 354 or 384 days). Without intercalation to add days or months to some years, seasons quickly drift in a calendar based solely on twelve lunar months. Lunisolar calendars have a thirteenth month added to some years to make up for the difference between a full year (now known to be about 365.24 days) and a year of just twelve lunar months. The numbers twelve and thirteen came to feature prominently in many cultures, at least partly due to this relationship of months to years. Other early forms of calendars originated in Mesoamerica, particularly in ancient Mayan civilization, in which they developed the Maya calendar, consisting of multiple interrelated calendars. These calendars were religiously and astronomically based; the Haab' calendar has 18 months in a year and 20 days in a month, plus five epagomenal days at the end of the year. In conjunction, the Maya also used a 260-day sacred calendar called the Tzolk'in. The reforms of Julius Caesar in 45 BC


id: time-20260505-2
file: data/en.wikipedia.org/wiki/Time-2.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe. Water clocks, and, later, mechanical clocks, were used to mark the events of the abbeys and monasteries of the Middle Ages. The passage of the hours at sea can also be marked by bell. The hours were marked by bells in abbeys as well as at sea. Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical orrery about 1330. The hourglass uses the flow of sand to measure the flow of time. They were also used in navigation. Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe (1522). The English word clock probably comes from the Middle Dutch word klocke which, in turn, derives from the medieval Latin word clocca, which ultimately derives from Celtic and is cognate with French, Latin, and German words that mean bell. Great advances in accurate time-keeping were made by Galileo Galilei and especially Christiaan Huygens with the invention of pendulum-driven clocks along with the invention of the minute hand by Jost Burgi. There is also a clock that was designed to keep


id: time-20260505-3
file: data/en.wikipedia.org/wiki/Time-3.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Many ancient cultures, particularly in the East, had a cyclical view of time. In these traditions, time was often seen as a recurring pattern of ages or cycles, where events and phenomena repeated themselves in a predictable manner. One of the most famous examples of this concept is found in Hindu philosophy, where time is depicted as a wheel called the "Kalachakra" or "Wheel of Time." According to this belief, the universe undergoes endless cycles of creation, preservation, and destruction. Similarly, in other ancient cultures such as those of the Mayans, Aztecs, and Chinese, there were also beliefs in cyclical time, often associated with astronomical observations and calendars. These cultures developed complex systems to track time, seasons, and celestial movements, reflecting their understanding of cyclical patterns in nature and the universe. The cyclical view of time contrasts with the linear concept of time more common in Western thought, where time is seen as progressing in a straight line from past to future without repetition. ==== Time in Abrahamic religions ==== In general, the Islamic and Judeo-Christian world-view regards time as linear and directional, beginning with the act of creation by God. The traditional Christian view sees time ending, teleologically, with


id: time-20260505-4
file: data/en.wikipedia.org/wiki/Time-4.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Two contrasting viewpoints on time divide prominent philosophers. One view is that time is part of the fundamental structure of the universe—a dimension independent of events, in which events occur in sequence. Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time. The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant, holds that time is neither an event nor a thing, and thus is not itself measurable nor can it be travelled. Furthermore, it may be that there is a subjective component to time, but whether or not time itself is "felt", as a sensation, or is a judgment, is a matter of debate. In philosophy, time was questioned throughout the centuries; what time is and if it is real or not. Ancient Greek philosophers asked if time was linear or cyclical and if time was endless or finite. These philosophers


id: time-20260505-5
file: data/en.wikipedia.org/wiki/Time-5.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Immanuel Kant, in the Critique of Pure Reason, described time as an a priori intuition that allows us (together with the other a priori intuition, space) to comprehend sense experience. With Kant, neither space nor time are conceived as substances, but rather both are elements of a systematic mental framework that necessarily structures the experiences of any rational agent, or observing subject. Kant thought of time as a fundamental part of an abstract conceptual framework, together with space and number, within which we sequence events, quantify their duration, and compare the motions of objects. In this view, time does not refer to any kind of entity that "flows," that objects "move through," or that is a "container" for events. Spatial measurements are used to quantify the extent of and distances between objects, and temporal measurements are used to quantify the durations of and between events. Time was designated by Kant as the purest possible schema of a pure concept or category. Henri Bergson believed that time was neither a real homogeneous medium nor a mental construct, but possesses what he referred to as Duration. Duration, in Bergson's view, was creativity and memory as an essential component of reality. According to


id: time-20260505-6
file: data/en.wikipedia.org/wiki/Time-6.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Until Einstein's reinterpretation of the physical concepts associated with time and space in 1907, time was considered to be the same everywhere in the universe, with all observers measuring the same time interval for any event. Non-relativistic classical mechanics is based on this Newtonian idea of time. Einstein, in his special theory of relativity, postulated the constancy and finiteness of the speed of light for all observers. He showed that this postulate, together with a reasonable definition for what it means for two events to be simultaneous, requires that distances appear compressed and time intervals appear lengthened for events associated with objects in motion relative to an inertial observer. The theory of special relativity finds a convenient formulation in Minkowski spacetime, a mathematical structure that combines three dimensions of space with a single dimension of time. In this formalism, distances in space can be measured by how long light takes to travel that distance, e.g., a light-year is a measure of distance, and a meter is now defined in terms of how far light travels in a certain amount of time. Two events in Minkowski spacetime are separated by an invariant interval, which can be either space-like, light-like, or time-like.


id: time-20260505-7
file: data/en.wikipedia.org/wiki/Time-7.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Time has historically been closely related with space, the two together merging into spacetime in Einstein's special relativity and general relativity. According to these theories, the concept of time depends on the spatial reference frame of the observer, and the human perception, as well as the measurement by instruments such as clocks, are different for observers in relative motion. For example, if a spaceship carrying a clock flies through space at (very nearly) the speed of light, its crew does not notice a change in the speed of time on board their vessel because everything traveling at the same speed slows down at the same rate (including the clock, the crew's thought processes, and the functions of their bodies). However, to a stationary observer watching the spaceship fly by, the spaceship appears flattened in the direction it is traveling and the clock on board the spaceship appears to move very slowly. On the other hand, the crew on board the spaceship also perceives the observer as slowed down and flattened along the spaceship's direction of travel, because both are moving at very nearly the speed of light relative to each other. Because the outside universe appears flattened to the spaceship,


id: time-20260505-8
file: data/en.wikipedia.org/wiki/Time-8.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
Time quantization refers to the theory that time has a smallest possible unit. Time quantization is a hypothetical concept. In the modern established physical theories like the Standard Model of particle physics and general relativity time is not quantized. Planck time (c. 5.4 × 10−44 seconds) is the unit of time in the system of natural units known as Planck units. Current established physical theories are believed to fail at this time scale, and many physicists expect that the Planck time might be the smallest unit of time that could ever be measured, even in principle. Though tentative physical theories that attempt to describe phenomena at this scale exist; an example is loop quantum gravity. Loop quantum gravity suggests that time is quantized; if gravity is quantized, spacetime is also quantized. == Travel == Time travel is the concept of moving backwards or forwards to different points in time, in a manner analogous to moving through space, and different from the normal "flow" of time to an earthbound observer. In this view, all points in time (including future times) "persist" in some way. Time travel has been a plot device in fiction since the 19th century. Travelling backwards or forwards


id: time-20260505-9
file: data/en.wikipedia.org/wiki/Time-9.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
=== Biopsychology === The brain's judgment of time is known to be a highly distributed system, including at least the cerebral cortex, cerebellum, and basal ganglia as its components. One particular component, the suprachiasmatic nuclei, is responsible for the circadian (or daily) rhythm, while other cell clusters appear capable of shorter-range (ultradian) timekeeping. Mental chronometry is the use of response time in perceptual-motor tasks to infer the content, duration, and temporal sequencing of cognitive operations. Judgments of time can be altered by temporal illusions (like the kappa effect), age, psychoactive drugs, and hypnosis. The sense of time is impaired in some people with neurological diseases such as Parkinson's disease and attention deficit disorder. Psychoactive drugs can impair the judgment of time. Stimulants can lead both humans and rats to overestimate time intervals, while depressants can have the opposite effect. The level of activity in the brain of neurotransmitters such as dopamine and norepinephrine may be the reason for this. Such chemicals will either excite or inhibit the firing of neurons in the brain, with a greater firing rate allowing the brain to register the occurrence of more events within a given interval (speed up time) and a decreased firing rate


id: time-20260505-10
file: data/en.wikipedia.org/wiki/Time-10.md
category: reference
title: Time
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time
date_saved: 2026-05-05T10:56:36.398112+00:00
instance: kb-cron
parent: time-20260505-0
summary:
In sociology and anthropology, time discipline is the general name given to social and economic rules, conventions, customs, and expectations governing the measurement of time, the social currency and awareness of time measurements, and people's expectations concerning the observance of these customs by others. Arlie Russell Hochschild and Norbert Elias have written on the use of time from a sociological perspective. The use of time is an important issue in understanding human behavior, education, and travel behavior. Time-use research is a developing field of study. The question concerns how time is allocated across a number of activities (such as time spent at home, at work, shopping, etc.). Time use changes with technology, as the television or the Internet created new opportunities to use time in different ways. However, some aspects of time use are relatively stable over long periods of time, such as the amount of time spent traveling to work, which despite major changes in transport, has been observed to be about 20–30 minutes one-way for a large number of cities over a long period. Time management is the organization of tasks or events by first estimating how much time a task requires and when it must be completed,


id: total-internal-reflection-20260505-0
file: data/en.wikipedia.org/wiki/Total_internal_reflection-0.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
In physics, total internal reflection (TIR) is the phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely reflected back into the first ("internal") medium. It occurs when the second medium has a higher wave speed (i.e., lower refractive index) than the first, and the waves are incident at a sufficiently oblique angle on the interface. For example, the water-to-air surface in a typical fish tank, when viewed obliquely from below, reflects the underwater scene like a mirror with no loss of brightness (Fig. 1). A scenario opposite to TIR, referred to as total external reflection, occurs in the extreme ultraviolet and X-ray regimes. TIR occurs not only with electromagnetic waves such as light and microwaves, but also with other types of waves, including sound and water waves. If the waves are capable of forming a narrow beam (Fig. 2), the reflection tends to be described in terms of "rays" rather than waves; in a medium whose properties are independent of direction, such as air, water or glass, the "rays" are perpendicular to associated wavefronts. The total internal reflection occurs when


id: total-internal-reflection-20260505-1
file: data/en.wikipedia.org/wiki/Total_internal_reflection-1.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
== Critical angle == The critical angle is the smallest angle of incidence that yields total reflection, or equivalently the largest angle for which a refracted ray exists. For light waves incident from an "internal" medium with a single refractive index n1, to an "external" medium with a single refractive index n2, the critical angle is given by θ c = arcsin ⁡ ( n 2 / n 1 ) {\displaystyle \theta _{\text{c}}=\arcsin(n_{2}/n_{1})} and is defined if n2 ≤ n1. For some other types of waves, it is more convenient to think in terms of propagation velocities rather than refractive indices. The explanation of the critical angle in terms of velocities is more general and will therefore be discussed first. When a wavefront is refracted from one medium to another, the incident (incoming) and refracted (outgoing) portions of the wavefront meet at a common line on the refracting surface (interface). Let this line, denoted by L, move at velocity u across the surface, where u is measured normal to L (Fig. 4). Let the incident and refracted wavefronts propagate with normal velocities v 1 {\displaystyle v_{1}} and v 2 {\displaystyle v_{2}} respectively, and let them make the dihedral angles θ1


id: total-internal-reflection-20260505-2
file: data/en.wikipedia.org/wiki/Total_internal_reflection-2.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
When standing beside an aquarium with one's eyes below the water level, one is likely to see fish or submerged objects reflected in the water-air surface (Fig. 1). The brightness of the reflected image – just as bright as the "direct" view – can be startling. A similar effect can be observed by opening one's eyes while swimming just below the water's surface. If the water is calm, the surface outside the critical angle (measured from the vertical) appears mirror-like, reflecting objects below. The region above the water cannot be seen except overhead, where the hemispherical field of view is compressed into a conical field known as Snell's window, whose angular diameter is twice the critical angle (cf. Fig. 6). The field of view above the water is theoretically 180° across, but seems less because as we look closer to the horizon, the vertical dimension is more strongly compressed by the refraction; e.g., by Eq. (3), for air-to-water incident angles of 90°, 80°, and 70°, the corresponding angles of refraction are 48.6° (θcr in Fig. 6), 47.6°, and 44.8°, indicating that the image of a point 20° above the horizon is 3.8° from the edge of Snell's window‍ while the


id: total-internal-reflection-20260505-3
file: data/en.wikipedia.org/wiki/Total_internal_reflection-3.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
But, if the reflection is total, the spatial penetration of the fields into medium 2 must be limited somehow, or else the total extent and hence the total energy of those fields would continue to increase, draining power from medium 1. Total reflection of a continuing wavetrain permits some energy to be stored in medium 2, but does not permit a continuing transfer of power from medium 1 to medium 2. Thus, using mostly qualitative reasoning, we can conclude that total internal reflection must be accompanied by a wavelike field in the "external" medium, traveling along the interface in synchronism with the incident and reflected waves, but with some sort of limited spatial penetration into the "external" medium; such a field may be called an evanescent wave. Fig. 9 shows the basic idea. The incident wave is assumed to be plane and sinusoidal. The reflected wave, for simplicity, is not shown. The evanescent wave travels to the right in lock-step with the incident and reflected waves, but its amplitude falls off with increasing distance from the interface. (Two features of the evanescent wave in Fig. 9 are to be explained later: first, that the evanescent wave crests are perpendicular to


id: total-internal-reflection-20260505-4
file: data/en.wikipedia.org/wiki/Total_internal_reflection-4.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
where k 0 = ω / c {\displaystyle k_{0}=\omega /c} is the wavenumber in vacuum. From (5), the electric field in the "external" medium has the form where kt is the wave vector for the transmitted wave (we assume isotropic media, but the transmitted wave is not yet assumed to be evanescent). In Cartesian coordinates (x, y, z), let the region y < 0 have refractive index n1, and let the region y > 0 have refractive index n2. Then the xz plane is the interface, and the y axis is normal to the interface (Fig. 11). Let i and j be the unit vectors in the x and y directions respectively. Let the plane of incidence (containing the incident wave-normal and the normal to the interface) be the xy plane (the plane of the page), with the angle of incidence θi measured from j towards i. Let the angle of refraction, measured in the same sense, be θt ("t" for transmitted, reserving "r" for reflected). From (6), the transmitted wave vector kt has magnitude n2k0. Hence, from the geometry, k t = n 2 k 0 ( i sin ⁡ θ t + j cos ⁡ θ t )


id: total-internal-reflection-20260505-5
file: data/en.wikipedia.org/wiki/Total_internal_reflection-5.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
== Phase shifts == Between 1817 and 1823, Augustin-Jean Fresnel discovered that total internal reflection is accompanied by a non-trivial phase shift (that is, a phase shift that is not restricted to 0° or 180°), as the Fresnel reflection coefficient acquires a non-zero imaginary part. We shall now explain this effect for electromagnetic waves in the case of linear, homogeneous, isotropic, non-magnetic media. The phase shift turns out to be an advance, which grows as the incidence angle increases beyond the critical angle, but which depends on the polarization of the incident wave. In equations (5), (7), (8), (10), and (11), we advance the phase by the angle ϕ if we replace ωt by ωt + ϕ (that is, if we replace −ωt by −ωt − ϕ), with the result that the (complex) field is multiplied by e−iϕ. So a phase advance is equivalent to multiplication by a complex constant with a negative argument. This becomes more obvious when (e.g.) the field (5) is factored as E k e i k ⋅ r e − i ω t , {\displaystyle \mathbf {E_{k}} e^{i\mathbf {k\cdot r} }e^{-i\omega t},} where the last factor contains the time dependence. To represent the polarization of


id: total-internal-reflection-20260505-6
file: data/en.wikipedia.org/wiki/Total_internal_reflection-6.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
which is positive for all angles of incidence with a transmitted ray (since θt > θi), giving a phase shift δs of zero. If we do likewise with (15), the result is easily shown to be equivalent to which is negative for small angles (that is, near normal incidence), but changes sign at Brewster's angle, where θi and θt are complementary. Thus the phase shift δp is 180° for small θi but switches to 0° at Brewster's angle. Combining the complementarity with Snell's law yields θi = arctan (1/n) as Brewster's angle for dense-to-rare incidence. (Equations (19) and (20) are known as Fresnel's sine law and Fresnel's tangent law. Both reduce to 0/0 at normal incidence, but yield the correct results in the limit as θi → 0. That they have opposite signs as we approach normal incidence is an obvious disadvantage of the sign convention used in this article; the corresponding advantage is that they have the same signs at grazing incidence.) That completes the information needed to plot δs and δp for all angles of incidence. This is done in Fig. 13, with δp in red and δs in blue, for three refractive indices. On the angle-of-incidence scale


id: total-internal-reflection-20260505-7
file: data/en.wikipedia.org/wiki/Total_internal_reflection-7.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
Image-erecting prisms for binoculars and spotting scopes include paired 45°-90°-45° Porro prisms (Fig. 14), the Porro–Abbe prism, the inline Koenig and Abbe–Koenig prisms, and the compact inline Schmidt–Pechan prism. (The last consists of two components, of which one is a kind of Bauernfeind prism, which requires a reflective coating on one of its two reflecting faces, due to a sub-critical angle of incidence.) These prisms have the additional function of folding the optical path from the objective lens to the prime focus, reducing the overall length for a given primary focal length. A prismatic star diagonal for an astronomical telescope may consist of a single Porro prism (configured for a single reflection, giving a mirror-reversed image) or an Amici roof prism (which gives a non-reversed image). Roof prisms use TIR at two faces meeting at a sharp 90° angle. This category includes the Koenig, Abbe–Koenig, Schmidt–Pechan, and Amici types (already mentioned), and the roof pentaprism used in SLR cameras; the last of these requires a reflective coating on one non-TIR face. A prismatic corner reflector uses three total internal reflections to reverse the direction of incoming light. The Dove prism gives an inline view with mirror-reversal. Polarizing prisms: Although the


id: total-internal-reflection-20260505-8
file: data/en.wikipedia.org/wiki/Total_internal_reflection-8.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
Theodoric having fallen into obscurity, the discovery of TIR was generally attributed to Johannes Kepler, who published his findings in his Dioptrice in 1611. Although Kepler failed to find the true law of refraction, he showed by experiment that for air-to-glass incidence, the incident and refracted rays rotated in the same sense about the point of incidence, and that as the angle of incidence varied through ±90°, the angle of refraction (as we now call it) varied through ±42°. He was also aware that the incident and refracted rays were interchangeable. But these observations did not cover the case of a ray incident from glass to air at an angle beyond 42°, and Kepler promptly concluded that such a ray could only be reflected. René Descartes rediscovered the law of refraction and published it in his La Dioptrique of 1637. In the same work he mentioned the senses of rotation of the incident and refracted rays and the condition of TIR. But he neglected to discuss the limiting case, and consequently failed to give an expression for the critical angle, although he could easily have done so. === Huygens and Newton: Rival explanations === Christiaan Huygens, in his Treatise on


id: total-internal-reflection-20260505-9
file: data/en.wikipedia.org/wiki/Total_internal_reflection-9.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
=== Laplace, Malus, and attenuated total reflectance (ATR) === William Hyde Wollaston, in the first of a pair of papers read to the Royal Society of London in 1802, reported his invention of a refractometer based on the critical angle of incidence from an internal medium of known "refractive power" (refractive index) to an external medium whose index was to be measured. With this device, Wollaston measured the "refractive powers" of numerous materials, some of which were too opaque to permit direct measurement of an angle of refraction. Translations of his papers were published in France in 1803, and apparently came to the attention of Pierre-Simon Laplace. According to Laplace's elaboration of Newton's theory of refraction, a corpuscle incident on a plane interface between two homogeneous isotropic media was subject to a force field that was symmetrical about the interface. If both media were transparent, total reflection would occur if the corpuscle were turned back before it exited the field in the second medium. But if the second medium were opaque, reflection would not be total unless the corpuscle were turned back before it left the first medium; this required a larger critical angle than the one given by Snell's


id: total-internal-reflection-20260505-10
file: data/en.wikipedia.org/wiki/Total_internal_reflection-10.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
calculating the angle of incidence that would introduce a total phase difference of 90° between the s and p components, for various numbers of total internal reflections at that angle (generally there were two solutions), subjecting light to that number of total internal reflections at that angle of incidence, with an initial linear polarization at 45° to the plane of incidence, and checking that the final polarization was circular. This procedure was necessary because, with the technology of the time, one could not measure the s and p phase-shifts directly, and one could not measure an arbitrary degree of ellipticality of polarization, such as might be caused by the difference between the phase shifts. But one could verify that the polarization was circular, because the brightness of the light was then insensitive to the orientation of the analyzer. For glass with a refractive index of 1.51, Fresnel calculated that a 45° phase difference between the two reflection coefficients (hence a 90° difference after two reflections) required an angle of incidence of 48°37' or 54°37'. He cut a rhomb to the latter angle and found that it performed as expected. Thus the specification of the Fresnel rhomb was completed. Similarly, Fresnel


id: total-internal-reflection-20260505-11
file: data/en.wikipedia.org/wiki/Total_internal_reflection-11.md
category: reference
title: Total internal reflection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection
date_saved: 2026-05-05T10:56:39.016628+00:00
instance: kb-cron
parent: total-internal-reflection-20260505-0
summary:
== Bibliography == S. Bochner (June 1963), "The significance of some basic mathematical conceptions for physics", Isis, 54 (2): 179–205; JSTOR 228537. M. Born and E. Wolf, 1970, Principles of Optics, 4th Ed., Oxford: Pergamon Press. C.B. Boyer, 1959, The Rainbow: From Myth to Mathematics, New York: Thomas Yoseloff. J.Z. Buchwald (December 1980), "Experimental investigations of double refraction from Huygens to Malus", Archive for History of Exact Sciences, 21 (4): 311–373. J.Z. Buchwald, 1989, The Rise of the Wave Theory of Light: Optical Theory and Experiment in the Early Nineteenth Century, University of Chicago Press, ISBN 0-226-07886-8. O. Darrigol, 2012, A History of Optics: From Greek Antiquity to the Nineteenth Century, Oxford, ISBN 978-0-19-964437-7. R. Fitzpatrick, 2013, Oscillations and Waves: An Introduction, Boca Raton, FL: CRC Press, ISBN 978-1-4665-6608-8. R. Fitzpatrick, 2013a, "Total Internal Reflection", University of Texas at Austin, accessed 14 March 2018. A. Fresnel, 1866 (ed. H. de Senarmont, E. Verdet, and L. Fresnel), Oeuvres complètes d'Augustin Fresnel, Paris: Imprimerie Impériale (3 vols., 1866–70), vol. 1 (1866). E. Hecht, 2017, Optics, 5th Ed., Pearson Education, ISBN 978-1-292-09693-3. C. Huygens, 1690, Traité de la Lumière (Leiden: Van der Aa), translated by S.P. Thompson as Treatise on Light, University of


id: trilobal-20260505-0
file: data/en.wikipedia.org/wiki/Trilobal-0.md
category: reference
title: Trilobal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Trilobal
date_saved: 2026-05-05T10:56:40.226028+00:00
instance: kb-cron
parent: trilobal-20260505-0
summary:
In fibers, trilobal is a cross-section shape with three distinct sides. The shape is advantageous for optical reflective properties and is used in textile fibers. Silk fibers' rounded edges and triangular cross section contribute to their luster; in some cases, synthetic fibers are manufactured to mimic this trilobal shape to give them a silk-like appearance. Filaments with a round cross section have less brilliance than trilobal filaments. == Etymology == The dictionary definition of Trilobal at Wiktionary is a combination of the words "Tri" for three and "lobal" for sides. == Objective == Trilobal shape helps in altering hand and increasing the luster. Many synthetic fibres, such as polyester and nylon, are manufactured in Trilobal cross sectional shape for the purpose of enhancing the brilliance and changing the handle. Luster adds aesthetic values in fabrics, contributes to their attractiveness. Occasionally, this adds value to their quality assessment. == Use == Synthetic fibers are particularly suitable for specific effects such as crimping and texturizing due to their adaptability during production. Trilobal cross section helps alter texture and several physical attributes such as strength and static properties, in addition to providing brightness to the fibres. The trilobal cross sectional shape helps to


id: ultraviolet-catastrophe-20260505-0
file: data/en.wikipedia.org/wiki/Ultraviolet_catastrophe-0.md
category: reference
title: Ultraviolet catastrophe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet_catastrophe
date_saved: 2026-05-05T10:56:41.419374+00:00
instance: kb-cron
parent: ultraviolet-catastrophe-20260505-0
summary:
The ultraviolet catastrophe, also called the Rayleigh–Jeans catastrophe, was the prediction of late 19th century and early 20th century classical physics that an ideal black body at thermal equilibrium would emit an unbounded quantity of energy as wavelength decreased into the ultraviolet range. The term "ultraviolet catastrophe" was first used in 1911 by the Austrian physicist Paul Ehrenfest, but the concept originated with the 1900 statistical derivation of the Rayleigh–Jeans law. The phrase refers to the fact that the empirically derived Rayleigh–Jeans law, which accurately predicted experimental results at large wavelengths, failed to do so for short wavelengths. (See the image for further elaboration.) As the theory diverged from empirical observations when these frequencies reached the ultraviolet region of the electromagnetic spectrum, there was a problem. This problem was later found to be due to a property of quanta as proposed by Max Planck: There could be no fraction of a discrete energy package already carrying minimal energy. Since the first use of this term, it has also been used for other predictions of a similar nature, as in quantum electrodynamics and such cases as ultraviolet divergence. == Problem == The Rayleigh-Jeans law is an approximation to the spectral radiance


id: unruh-effect-20260505-0
file: data/en.wikipedia.org/wiki/Unruh_effect-0.md
category: reference
title: Unruh effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unruh_effect
date_saved: 2026-05-05T10:56:42.662629+00:00
instance: kb-cron
parent: unruh-effect-20260505-0
summary:
The Unruh effect (also known as the Fulling–Davies–Unruh effect) is a hypothetical, observer-dependent prediction of quantum field theory that an observer who is uniformly accelerating through empty space (Minkowski vacuum) will perceive a thermal bath. This means that even in the absence of any external heat sources, an accelerating observer will detect particles and experience a temperature. In contrast, an inertial observer in the same region of spacetime would observe no particles and no temperature. In other words, the background appears to be warm from an accelerating reference frame. In layman's terms, an accelerating thermometer in empty space (like one being waved around), without any other contribution to its temperature, will record a non-zero temperature, just from its acceleration. Heuristically, for a uniformly accelerating observer, the ground state of an inertial observer is seen as a mixed state in thermodynamic equilibrium with a non-zero temperature bath. The Unruh effect was first described by Stephen Fulling in 1973, Paul Davies in 1975 and W. G. Unruh in 1976. It is currently not clear whether the Unruh effect has actually been observed, since the claimed observations are disputed. There is also some doubt about whether the Unruh effect implies the existence of


id: unruh-effect-20260505-1
file: data/en.wikipedia.org/wiki/Unruh_effect-1.md
category: reference
title: Unruh effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unruh_effect
date_saved: 2026-05-05T10:56:42.662629+00:00
instance: kb-cron
parent: unruh-effect-20260505-0
summary:
== Explanation == Unruh demonstrated theoretically that the notion of vacuum depends on the path of the observer through spacetime. From the viewpoint of the accelerating observer, the vacuum of the inertial observer will look like a state containing many particles in thermal equilibrium—a warm gas. The Unruh effect would only appear to an accelerating observer. And although the Unruh effect would initially be perceived as counter-intuitive, it makes sense if the word vacuum is interpreted in the following specific way. In quantum field theory, the concept of "vacuum" is not the same as "empty space": Space is filled with the quantized fields that make up the universe. Vacuum is simply the lowest possible energy state of these fields. The energy states of any quantized field are defined by the Hamiltonian, based on local conditions, including the time coordinate. According to special relativity, two observers moving relative to each other must use different time coordinates. If those observers are accelerating, there may be no shared coordinate system. Hence, the observers will see different quantum states and thus different vacua. In some cases, the vacuum of one observer is not even in the space of quantum states of the other. In


id: unruh-effect-20260505-2
file: data/en.wikipedia.org/wiki/Unruh_effect-2.md
category: reference
title: Unruh effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Unruh_effect
date_saved: 2026-05-05T10:56:42.662629+00:00
instance: kb-cron
parent: unruh-effect-20260505-0
summary:
A path integral with real time coordinate is dual to a thermal partition function, related by a Wick rotation. The periodicity β {\displaystyle \beta } of imaginary time corresponds to a temperature of β = 1 / T {\displaystyle \beta =1/T} in thermal quantum field theory. Note that the path integral for this Hamiltonian is closed with period 2π. This means that the H modes are thermally occupied with temperature ⁠1/2π⁠. This is not an actual temperature, because H is dimensionless. It is conjugate to the timelike polar angle σ, which is also dimensionless. To restore the length dimension, note that a mode of fixed frequency f in σ at position ρ has a frequency which is determined by the square root of the (absolute value of the) metric at ρ, the redshift factor. This can be seen by transforming the time coordinate of a Rindler observer at fixed ρ to an inertial, co-moving observer observing a proper time. From the Rindler-line-element given above, this is just ρ. The actual inverse temperature at this point is therefore β = 2 π ρ . {\displaystyle \beta =2\pi \rho .} It can be shown that the acceleration of a trajectory at constant


id: upstream-contamination-20260505-0
file: data/en.wikipedia.org/wiki/Upstream_contamination-0.md
category: reference
title: Upstream contamination
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Upstream_contamination
date_saved: 2026-05-05T10:56:43.867068+00:00
instance: kb-cron
parent: upstream-contamination-20260505-0
summary:
Upstream contamination by floating particles is a counterintuitive phenomenon in fluid dynamics. When pouring water from a higher container to a lower one, particles floating in the latter can climb upstream into the upper container. A definitive explanation is still lacking: experimental and computational evidence indicates that the contamination is chiefly driven by surface tension gradients, however the phenomenon is also affected by the dynamics of swirling flows that remain to be fully investigated. == Origins == The phenomenon was observed in 2008 by the Argentine Sebastian Bianchini during mate tea preparation, while studying physics at the University of Havana. It rapidly attracted the interest of professor Alejandro Lage-Castellanos, who performed, with Bianchini, a series of controlled experiments. Later on professor Ernesto Altshuler completed the trio in Havana, which resulted in the Diploma thesis of Bianchini and a short original paper posted in the web arXiv and mentioned as a surprising fact in some online journals. Bianchini's Diploma thesis showed that the phenomenon could be reproduced in a controlled laboratory setting using mate leaves or chalk powder as contaminants, and that temperature gradients (hot in the top, cold in the bottom) were not necessary to generate the effect. The research


id: vacuum-20260505-0
file: data/en.wikipedia.org/wiki/Vacuum-0.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
A vacuum (pl.: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective vacuus (neuter vacuum) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often discuss ideal test results that would occur in a perfect vacuum, which they sometimes simply call "vacuum" or free space, and use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure. The Latin term in vacuo is used to describe an object that is surrounded by a vacuum. The quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10−12) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm3. Outer


id: vacuum-20260505-1
file: data/en.wikipedia.org/wiki/Vacuum-1.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
Medieval thought experiments into the idea of a vacuum considered whether a vacuum was present, if only for an instant, between two flat plates when they were rapidly separated. There was much discussion of whether the air moved in quickly enough as the plates were separated, or, as Walter Burley postulated, whether a 'celestial agent' prevented the vacuum arising. Jean Buridan reported in the 14th century that teams of ten horses could not pull open bellows when the port was sealed. The 17th century saw the first attempts to quantify measurements of partial vacuum. Evangelista Torricelli's mercury barometer of 1643 and Blaise Pascal's experiments both demonstrated a partial vacuum. In 1654, Otto von Guericke invented the first vacuum pump and conducted his famous Magdeburg hemispheres experiment, showing that, owing to atmospheric pressure outside the hemispheres, teams of horses could not separate two hemispheres from which the air had been partially evacuated. Robert Boyle improved Guericke's design and with the help of Robert Hooke further developed vacuum pump technology. Thereafter, research into the partial vacuum lapsed until 1850 when August Toepler invented the Toepler pump and in 1855 when Heinrich Geissler invented the mercury displacement pump, achieving a partial vacuum of


id: vacuum-20260505-2
file: data/en.wikipedia.org/wiki/Vacuum-2.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
In quantum mechanics and quantum field theory, the vacuum is defined as the state (that is, the solution to the equations of the theory) with the lowest possible energy (the ground state of the Hilbert space). In quantum electrodynamics this vacuum is referred to as 'QED vacuum' to distinguish it from the vacuum of quantum chromodynamics, denoted as QCD vacuum. QED vacuum is a state with no matter particles (hence the name), and no photons. As described above, this state is impossible to achieve experimentally. (Even if every matter particle could somehow be removed from a volume, it would be impossible to eliminate all the blackbody photons.) Nonetheless, it provides a good model for realizable vacuum, and agrees with a number of experimental observations as described next. QED vacuum has interesting and complex properties. In QED vacuum, the electric and magnetic fields have zero average values, but their variances are not zero. As a result, QED vacuum contains vacuum fluctuations (virtual particles that hop into and out of existence), and a finite energy called vacuum energy. Vacuum fluctuations are an essential and ubiquitous part of quantum field theory. Some experimentally verified effects of vacuum fluctuations include spontaneous emission and the


id: vacuum-20260505-3
file: data/en.wikipedia.org/wiki/Vacuum-3.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
=== Relative versus absolute measurement === Vacuum is measured in units of pressure, typically as a subtraction relative to ambient atmospheric pressure on Earth. But the amount of relative measurable vacuum varies with local conditions. On the surface of Venus, where ground-level atmospheric pressure is much higher than on Earth, much higher relative vacuum readings would be possible. On the surface of the Moon with almost no atmosphere, it would be extremely difficult to create a measurable vacuum relative to the local environment. Similarly, much higher than normal relative vacuum readings are possible deep in the Earth's ocean. A submarine maintaining an internal pressure of 1 atmosphere submerged to a depth of 10 atmospheres (98 metres; a 9.8-metre column of seawater has the equivalent weight of 1 atm) is effectively a vacuum chamber keeping out the crushing exterior water pressures, though the 1 atm inside the submarine would not normally be considered a vacuum. Therefore, to properly understand the following discussions of vacuum measurement, it is important that the reader assumes the relative measurements are being done on Earth at sea level, at exactly 1 atmosphere of ambient atmospheric pressure. === Measurements relative to 1 atm === The SI unit


id: vacuum-20260505-4
file: data/en.wikipedia.org/wiki/Vacuum-4.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
Vacuum is useful in a variety of processes and devices. Its first widespread use was in the incandescent light bulb to protect the filament from chemical degradation. The chemical inertness produced by a vacuum is also useful for electron-beam welding, cold welding, vacuum packing and vacuum frying. Ultra-high vacuum is used in the study of atomically clean substrates, as only a very good vacuum preserves atomic-scale clean surfaces for a reasonably long time (on the order of minutes to days). High to ultra-high vacuum removes the obstruction of air, allowing particle beams to deposit or remove materials without contamination. This is the principle behind chemical vapor deposition, physical vapor deposition, and dry etching which are essential to the fabrication of semiconductors and optical coatings, and to surface science. The reduction of convection provides the thermal insulation of thermos bottles. Deep vacuum lowers the boiling point of liquids and promotes low temperature outgassing which is used in freeze drying, adhesive preparation, distillation, metallurgy, and process purging. The electrical properties of vacuum make electron microscopes and vacuum tubes possible, including cathode-ray tubes. Vacuum interrupters are used in electrical switchgear. Vacuum arc processes are industrially important for production of certain grades of steel


id: vacuum-20260505-5
file: data/en.wikipedia.org/wiki/Vacuum-5.md
category: reference
title: Vacuum
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vacuum
date_saved: 2026-05-05T10:56:45.128605+00:00
instance: kb-cron
parent: vacuum-20260505-0
summary:
The above explanation is merely a simple introduction to vacuum pumping, and is not representative of the entire range of pumps in use. Many variations of the positive displacement pump have been developed, and many other pump designs rely on fundamentally different principles. Momentum transfer pumps, which bear some similarities to dynamic pumps used at higher pressures, can achieve much higher quality vacuums than positive displacement pumps. Entrapment pumps can capture gases in a solid or absorbed state, often with no moving parts, no seals and no vibration. None of these pumps are universal; each type has important performance limitations. They all share a difficulty in pumping low molecular weight gases, especially hydrogen, helium, and neon. The lowest pressure that can be attained in a system is also dependent on many things other than the nature of the pumps. Multiple pumps may be connected in series, called stages, to achieve higher vacuums. The choice of seals, chamber geometry, materials, and pump-down procedures will all have an impact. Collectively, these are called vacuum technique. And sometimes, the final pressure is not the only relevant characteristic. Pumping systems differ in oil contamination, vibration, preferential pumping of certain gases, pump-down speeds, intermittent duty


id: hydraulic-shock-20260505-0
file: data/en.wikipedia.org/wiki/Hydraulic_shock-0.md
category: reference
title: Hydraulic shock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydraulic_shock
date_saved: 2026-05-05T10:56:46.344223+00:00
instance: kb-cron
parent: hydraulic-shock-20260505-0
summary:
Hydraulic shock (colloquial: water hammer; fluid hammer) is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly: a momentum change. It is usually observed in a liquid but gases can also be affected. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system and a pressure wave propagates in the pipe. This pressure wave can cause major problems, from noise and vibration to pipe rupture and collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, blowoff valves, and other features. The effects can be avoided by ensuring that no valves will close too quickly with significant flow, but there are many situations that can cause the effect. Rough calculations can be made using the Zhukovsky (Joukowsky) equation, or more accurate ones using the method of characteristics. == History == In the 1st century B.C., Marcus Vitruvius Pollio described the effect of water hammer in lead pipes and stone tubes of the Roman public water supply. In 1772, Englishman John Whitehurst built a hydraulic ram for a home in Cheshire, England. In 1796, French inventor


id: hydraulic-shock-20260505-1
file: data/en.wikipedia.org/wiki/Hydraulic_shock-1.md
category: reference
title: Hydraulic shock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydraulic_shock
date_saved: 2026-05-05T10:56:46.344223+00:00
instance: kb-cron
parent: hydraulic-shock-20260505-0
summary:
Water hammers have caused accidents and fatalities, but usually, damage is limited to the breakage of pipes or appendages. An engineer should always assess the risk of a pipeline burst. Pipelines transporting hazardous liquids or gases warrant special care in design, construction, and operation. Hydroelectric power plants, especially, must be carefully designed and maintained because the water hammer can cause water pipes to fail catastrophically. The following characteristics may reduce or eliminate water hammer: Reduce the pressure of the water supply to the building by fitting a regulator. Lower fluid velocities. To keep water hammer low, pipe-sizing charts for some applications recommend flow velocity at or below 1.5 m/s (4.9 ft/s). Fit slowly closing valves. Toilet fill valves are available in a quiet fill type that closes quietly. Non-slam check valves do not rely on fluid flow to close and will do so before the water flow reaches significant velocity. High pipeline pressure rating (does not reduce the effect but protects against damage). Good pipeline control (start-up and shut-down procedures). Water towers (used in many drinking water systems) or surge tanks help maintain steady flow rates and trap large pressure fluctuations. Air vessels such as expansion tanks and some types


id: hydraulic-shock-20260505-2
file: data/en.wikipedia.org/wiki/Hydraulic_shock-2.md
category: reference
title: Hydraulic shock
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydraulic_shock
date_saved: 2026-05-05T10:56:46.344223+00:00
instance: kb-cron
parent: hydraulic-shock-20260505-0
summary:
where P1 is the inlet pressure in psi, V is the flow velocity in ft/s, t is the valve closing time in seconds, and L is the upstream pipe length in feet. Hence, we can say that the magnitude of the water hammer largely depends upon the time of closure, the elastic components of the pipe & fluid properties. == Expression for the excess pressure due to water hammer == When a valve with a volumetric flow rate Q is closed, an excess pressure ΔP is created upstream of the valve, whose value is given by the Joukowsky equation: Δ P = Z Q . {\displaystyle \Delta P=ZQ.} In this expression: ΔP is the overpressurization in Pa; Q is the volumetric flow in m3/s; Z is the hydraulic impedance, expressed in kg/m4/s. The hydraulic impedance Z of the pipeline determines the magnitude of the water hammer pulse. It is itself defined by Z = ρ B A , {\displaystyle Z={\frac {\sqrt {\rho B}}{A}},} where ρ the density of the liquid, expressed in kg/m3; A cross sectional area of the pipe, m2; B equivalent modulus of compressibility of the liquid in the pipe, expressed in Pa. The latter follows from a


id: wigner-effect-20260505-0
file: data/en.wikipedia.org/wiki/Wigner_effect-0.md
category: reference
title: Wigner effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wigner_effect
date_saved: 2026-05-05T10:56:47.516234+00:00
instance: kb-cron
parent: wigner-effect-20260505-0
summary:
The Wigner effect (named for its discoverer, Eugene Wigner), also known as the discomposition effect or Wigner's disease, is the displacement of atoms in a solid caused by neutron radiation. Any solid can display the Wigner effect. The effect is of most concern in neutron moderators, such as graphite, intended to reduce the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235. == Cause == To cause the Wigner effect, neutrons that collide with the atoms in a crystal structure must have enough energy to displace them from the lattice. This amount (threshold displacement energy) is approximately 25 eV. A neutron's energy can vary widely, but it is not uncommon to have energies up to and exceeding 10 MeV (10,000,000 eV) in the centre of a nuclear reactor. A neutron with a significant amount of energy will create a displacement cascade in a matrix via elastic collisions. For example, a 1 MeV neutron striking graphite will create 900 displacements. Not all displacements will create defects, because some of the struck atoms will find and fill the vacancies that were either small pre-existing voids or vacancies newly formed by the other


id: wrinklon-20260505-0
file: data/en.wikipedia.org/wiki/Wrinklon-0.md
category: reference
title: Wrinklon
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wrinklon
date_saved: 2026-05-05T10:56:48.717684+00:00
instance: kb-cron
parent: wrinklon-20260505-0
summary:
A wrinklon is a type of quasiparticle introduced in the study of wrinkling behavior in thin sheet materials, such as graphene or fabric. It is a localized excitation corresponding to wrinkles in a constrained two dimensional system. It represents a localized region where two wrinkles in the material merge into one, serving as part of the pattern seen when the material forms wrinkles. The term "wrinklon" is derived from "wrinkle" and the suffix "-on", the latter commonly used in physics to denote quasiparticles such as the "phonon" or "polaron", as well as particles (photon, electron). The concept of wrinklons aids in understanding and describing the complex wrinkling patterns observed in a variety of materials. This understanding could prove useful in fields such as material science and nanotechnology, particularly in the study and development of two-dimensional materials such as graphene. Further studies have expanded the understanding of wrinklons, demonstrating that the behavior of these wrinkles in thin films, such as graphene, can differ depending on the substrate they are on. For instance, when graphene is on a compliant polymer substrate, the properties of the wrinklons change with the thickness of the graphene. This suggests that the characteristics of the substrate have


id: zeeman-energy-20260505-0
file: data/en.wikipedia.org/wiki/Zeeman_energy-0.md
category: reference
title: Zeeman energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Zeeman_energy
date_saved: 2026-05-05T10:56:49.941247+00:00
instance: kb-cron
parent: zeeman-energy-20260505-0
summary:
Zeeman energy, or the external field energy, is the potential energy of a magnetised body in an external magnetic field. It is named after the Dutch physicist Pieter Zeeman, primarily known for the Zeeman effect. In SI units, it is given by E Z e e m a n = − μ 0 ∫ V M ⋅ H E x t d V {\displaystyle E_{\rm {Zeeman}}=-\mu _{0}\int _{V}\,{\textbf {M}}\cdot {\textbf {H}}_{\rm {Ext}}\,\mathrm {d} V} where HExt is the external field, M the local magnetisation, and the integral is done over the volume of the body. This is the statistical average (over a unit volume macroscopic sample) of a corresponding microscopic Hamiltonial (energy) for each individual magnetic moment m, which is however experiencing a local induction B: H = − m ⋅ B {\displaystyle H=-{\textbf {m}}\cdot {\textbf {B}}} == References == F. Barozzi, F. Gasparini, Fondamenti di Elettrotecnica: Elettromagnetismo, UTET Torino, 1989 Hubert, A. and Schäfer, R. Magnetic domains: the analysis of magnetic microstructures, Springer-Verlag, 1998


id: thermodynamic-process-20260505-0
file: data/en.wikipedia.org/wiki/Thermodynamic_process-0.md
category: reference
title: Thermodynamic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_process
date_saved: 2026-05-05T10:56:51.523233+00:00
instance: kb-cron
parent: thermodynamic-process-20260505-0
summary:
Classical thermodynamics considers three main kinds of thermodynamic processes: (1) changes in a system, (2) cycles in a system, and (3) flow processes. (1) A Thermodynamic process is a process in which the thermodynamic state of a system is changed. A change in a system is defined by a passage from an initial to a final state of thermodynamic equilibrium. In classical thermodynamics, the actual course of the process is not the primary concern, and often is ignored. A state of thermodynamic equilibrium endures unchangingly unless it is interrupted by a thermodynamic operation that initiates a thermodynamic process. The equilibrium states are each respectively fully specified by a suitable set of thermodynamic state variables, that depend only on the current state of the system, not on the path taken by the processes that produce the state. In general, during the actual course of a thermodynamic process, the system may pass through physical states which are not describable as thermodynamic states, because they are far from internal thermodynamic equilibrium. Non-equilibrium thermodynamics, however, considers processes in which the states of the system are close to thermodynamic equilibrium, and aims to describe the continuous passage along the path, at definite rates of progress.


id: thermodynamic-process-20260505-1
file: data/en.wikipedia.org/wiki/Thermodynamic_process-1.md
category: reference
title: Thermodynamic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_process
date_saved: 2026-05-05T10:56:51.523233+00:00
instance: kb-cron
parent: thermodynamic-process-20260505-0
summary:
An isobaric process occurs at constant pressure. An example would be to have a movable piston in a cylinder, so that the pressure inside the cylinder is always at atmospheric pressure, although it is separated from the atmosphere. In other words, the system is dynamically connected, by a movable boundary, to a constant-pressure reservoir. An isochoric process is one in which the volume is held constant, with the result that the mechanical PV work done by the system will be zero. On the other hand, work can be done isochorically on the system, for example by a shaft that drives a rotary paddle located inside the system. It follows that, for the simple system of one deformation variable, any heat energy transferred to the system externally will be absorbed as internal energy. An isochoric process is also known as an isometric process or an isovolumetric process. An example would be to place a closed tin can of material into a fire. To a first approximation, the can will not expand, and the only change will be that the contents gain internal energy, evidenced by increase in temperature and pressure. Mathematically, δ Q = d U {\displaystyle \delta Q=dU} . The


id: adiabatic-accessibility-20260505-0
file: data/en.wikipedia.org/wiki/Adiabatic_accessibility-0.md
category: reference
title: Adiabatic accessibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_accessibility
date_saved: 2026-05-05T10:56:52.701422+00:00
instance: kb-cron
parent: adiabatic-accessibility-20260505-0
summary:
In thermodynamics, adiabatic accessibility determines if one equilibrium state of a system can transition to another solely through an adiabatic process, meaning no heat is exchanged with the environment. The concept was coined by Constantin Carathéodory in 1909 ("adiabatische Erreichbarkeit") and taken up 90 years later by Elliott Lieb and J. Yngvason in their axiomatic approach to the foundations of thermodynamics. It was also used by R. Giles in his 1964 monograph. Adiabatic accessibility plays a crucial role in defining fundamental concepts such as entropy and understanding the limitations on state transformations in thermodynamic systems. == Description == A system in a state Y is said to be adiabatically accessible from a state X if X can be transformed into Y without the system suffering transfer of energy as heat or transfer of matter. X may, however, be transformed to Y by doing work on X. For example, a system consisting of one kilogram of warm water is adiabatically accessible from a system consisting of one kilogram of cool water, since the cool water may be mechanically stirred to warm it. However, the cool water is not adiabatically accessible from the warm water, since no amount or type of work


id: list-of-adiabatic-concepts-20260505-0
file: data/en.wikipedia.org/wiki/List_of_adiabatic_concepts-0.md
category: reference
title: List of adiabatic concepts
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_adiabatic_concepts
date_saved: 2026-05-05T10:56:53.965483+00:00
instance: kb-cron
parent: list-of-adiabatic-concepts-20260505-0
summary:
Adiabatic (from Gr. ἀ negative + διάβασις passage; transference) refers to any process that occurs without heat transfer. This concept is used in many areas of physics and engineering. Notable examples are listed below. == Automobiles == Engine braking, a feature of some diesel engines, uses adiabatic expansion to diminish the vehicle's forward momentum. == Meteorology == Adiabatic lapse rate, the change in air temperature with changing height, resulting from pressure change. == Quantum chemistry == Adiabatic invariant Born–Oppenheimer approximation == Thermodynamics == Adiabatic process Adiabatic ionization Adiabatic index Adiabatic accessibility == Quantum mechanics == Adiabatic theorem Adiabatic quantum motor == Electronics == Adiabatic circuit Adiabatic logic == References ==


id: adiabatic-process-20260505-0
file: data/en.wikipedia.org/wiki/Adiabatic_process-0.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
An adiabatic process (adiabatic from Ancient Greek ἀδιάβατος (adiábatos) 'impassable') is a type of thermodynamic process whereby a transfer of energy between the thermodynamic system and its environment is accompanied neither by a transfer of entropy nor of amounts of constituents. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work and/or mass flow. As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. The opposite term to "adiabatic" is diabatic. Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings. In meteorology, adiabatic expansion and cooling of moist air, which can be triggered by winds flowing up and over a mountain for example, can cause the water vapor pressure to exceed the saturation vapor pressure. Expansion and cooling beyond the saturation vapor pressure is often idealized as a pseudo-adiabatic process whereby excess vapor instantly precipitates into water droplets. The change in temperature of air undergoing pseudo-adiabatic


id: adiabatic-process-20260505-1
file: data/en.wikipedia.org/wiki/Adiabatic_process-1.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
If the system has such rigid walls that work cannot be transferred in or out (W = 0), and the walls are not adiabatic and energy is added in the form of heat (Q > 0), and there is no phase change, then the temperature of the system will rise. If the system has such rigid walls that pressure–volume work cannot be done, but the walls are adiabatic (Q = 0), and energy is added as isochoric (constant volume) work in the form of friction or the stirring of a viscous fluid within the system (W < 0), and there is no phase change, then the temperature of the system will rise. If the system walls are adiabatic (Q = 0) but not rigid (W ≠ 0), and, in a fictive idealized process, energy is added to the system in the form of frictionless, non-viscous pressure–volume work (W < 0), and there is no phase change, then the temperature of the system will rise. Such a process is called an isentropic process and is said to be "reversible". Ideally, if the process were reversed the energy could be recovered entirely as work done by the system. If the system contains


id: adiabatic-process-20260505-2
file: data/en.wikipedia.org/wiki/Adiabatic_process-2.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
=== Adiabatic expansion === Adiabatic expansion occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand in size, thus causing it to do work on its surroundings. When the pressure applied on a parcel of gas is reduced, the gas in the parcel is allowed to expand; as the volume increases, the temperature falls as its internal energy decreases. Adiabatic expansion occurs in the Earth's atmosphere with orographic lifting and lee waves, and this can form pilei or lenticular clouds. Due in part to adiabatic expansion in mountainous areas, snowfall actually occurs in some parts of the Sahara desert. Adiabatic expansion does not have to involve a fluid. One technique used to reach very low temperatures (thousandths and even millionths of a degree above absolute zero) is via adiabatic demagnetisation, where the change in magnetic field on a magnetic material is used to provide adiabatic expansion. Also, the contents of an expanding universe can be described (to first order) as an adiabatically expanding fluid. (See heat death of the universe.) Rising magma also undergoes adiabatic expansion before eruption, particularly significant in the case of magmas that rise quickly from great depths such as kimberlites. In


id: adiabatic-process-20260505-3
file: data/en.wikipedia.org/wiki/Adiabatic_process-3.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
or 25.1 bar. This pressure increase is more than a simple 10:1 compression ratio would indicate; this is because the gas is not only compressed, but the work done to compress the gas also increases its internal energy, which manifests itself by a rise in the gas temperature and an additional rise in pressure above what would result from a simplistic calculation of 10 times the original pressure. We can solve for the temperature of the compressed gas in the engine cylinder as well, using the ideal gas law, P V = n R T (n is amount of gas in moles and R the gas constant for that gas). Our initial conditions being 100 kPa of pressure, 1 L volume, and 300 K of temperature, our experimental constant (n R ) is: P V T = c o n s t a n t 2 = 10 5 P a × 10 − 3 m 3 300 K = 0.333 P a m 3 K − 1 . {\displaystyle {\begin{aligned}{\frac {P\ V}{T}}&={\mathsf {constant}}_{2}\\&={\frac {10^{5}~{\mathsf {Pa}}\times 10^{-3}~{\mathsf {m}}^{3}}{300~{\mathsf {K}}}}\\&=0.333~{\mathsf {Pa}}\ {\mathsf {m}}^{3}{\mathsf {K}}^{-1}~.\end{aligned}}} We know the compressed gas has V = 0.1 L and P = 2.51×106 Pa, so we


id: adiabatic-process-20260505-4
file: data/en.wikipedia.org/wiki/Adiabatic_process-4.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
P = P 1 ( V 1 V ) γ . {\displaystyle P=P_{1}\ \left({\frac {V_{1}}{V}}\right)^{\gamma }~.} Substituting this into (b2) gives W = ∫ V 1 V 2 P 1 ( V 1 V ) γ d V . {\displaystyle W=\int _{V_{1}}^{V_{2}}P_{1}\ \left({\frac {V_{1}}{V}}\right)^{\gamma }\ \mathrm {d} V~.} Integrating, we obtain the expression for work, W = P 1 V 1 γ V 2 1 − γ − V 1 1 − γ 1 − γ = P 2 V 2 − P 1 V 1 1 − γ . {\displaystyle {\begin{aligned}W&=P_{1}\ V_{1}^{\gamma }\ {\frac {V_{2}^{1-\gamma }-V_{1}^{1-\gamma }}{1-\gamma }}\\[1ex]&={\frac {P_{2}\ V_{2}-P_{1}\ V_{1}}{1-\gamma }}.\end{aligned}}} Substituting γ = ⁠α + 1/α⁠ in the second term, W = − α P 1 V 1 γ ( V 2 1 − γ − V 1 1 − γ ) . {\displaystyle W=-\alpha \ P_{1}\ V_{1}^{\gamma }\ \left(V_{2}^{1-\gamma }-V_{1}^{1-\gamma }\right)~.} Rearranging, W = − α P 1 V 1 ( ( V 2 V 1 ) 1 − γ − 1 ) . {\displaystyle W=-\alpha \ P_{1}\ V_{1}\ \left(\left({\frac {V_{2}}{V_{1}}}\right)^{1-\gamma }-1\right)~.} Using the ideal gas law and assuming a constant molar quantity (as often happens in practical cases), W = − α n R T


id: adiabatic-process-20260505-5
file: data/en.wikipedia.org/wiki/Adiabatic_process-5.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
An adiabat is a curve of constant entropy in a diagram. Some properties of adiabats on a P – V diagram are indicated. These properties may be read from the classical behaviour of ideal gases, except in the region where P V becomes small (low temperature), where quantum effects become important. Every adiabat asymptotically approaches both the V axis and the P axis (just like isotherms). Each adiabat intersects each isotherm exactly once. An adiabat looks similar to an isotherm, except that during an expansion, an adiabat loses more pressure than an isotherm, so it has a steeper inclination (more vertical). If isotherms are concave towards the north-east direction (45° from V axis), then adiabats are concave towards the east north-east (31° from V axisaxis). If adiabats and isotherms are graphed at regular intervals of entropy and temperature, respectively (like altitude on a contour map), then as the eye moves towards the axes (towards the south-west), it sees the density of isotherms stay constant, but it sees the density of adiabats grow. The exception is very near absolute zero, where the density of adiabats drops sharply and they become rare (see Nernst's theorem). == Etymology == The term adiabatic ()


id: adiabatic-process-20260505-6
file: data/en.wikipedia.org/wiki/Adiabatic_process-6.md
category: reference
title: Adiabatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adiabatic_process
date_saved: 2026-05-05T10:56:55.166101+00:00
instance: kb-cron
parent: adiabatic-process-20260505-0
summary:
== Divergent usages of the word adiabatic == This present article is written from the viewpoint of macroscopic thermodynamics, and the word adiabatic is used in this article in the traditional way of thermodynamics, introduced by Rankine. It is pointed out in the present article that, for example, if a compression of a gas is rapid, then there is little time for heat transfer to occur, even when the gas is not adiabatically isolated by a definite wall. In this sense, a rapid compression of a gas is sometimes approximately or loosely said to be adiabatic, though often far from isentropic, even when the gas is not adiabatically isolated by a definite wall. Some authors, like Pippard, recommend using "adiathermal" to refer to processes where no heat-exchange occurs (such as Joule expansion), and "adiabatic" to reversible quasi-static adiathermal processes (so that rapid compression of a gas is not "adiabatic"). And Laidler has summarized the complicated etymology of "adiabatic". Quantum mechanics and quantum statistical mechanics, however, use the word adiabatic in a very different sense, one that can at times seem almost opposite to the classical thermodynamic sense. In quantum theory, the word adiabatic can mean something perhaps near isentropic, or


id: air-separation-20260505-0
file: data/en.wikipedia.org/wiki/Air_separation-0.md
category: reference
title: Air separation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Air_separation
date_saved: 2026-05-05T10:56:56.320357+00:00
instance: kb-cron
parent: air-separation-20260505-0
summary:
An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen, and sometimes also argon and other rare inert gases. The most common method for air separation is fractional distillation. Cryogenic air separation units (ASUs) are built to provide nitrogen or oxygen and often co-produce argon. Other methods such as membrane, pressure swing adsorption (PSA) and vacuum pressure swing adsorption (VPSA) are commercially used to separate a single component from ordinary air. High purity oxygen, nitrogen, and argon, used for semiconductor device fabrication, require cryogenic distillation. Similarly, the only viable source of the rare gases neon, krypton, xenon is the distillation of air using at least two distillation columns. Helium is also recovered in advanced air separation processes. == Cryogenic distillation process == Pure gases can be separated from air by first cooling it until it liquefies, then selectively distilling the components at their various boiling temperatures. The process can produce high purity gases but is energy-intensive. This process was pioneered by Carl von Linde in the early 20th century and is still used today to produce high purity gases. He developed it in the year 1895; the process remained purely academic for seven years before


id: air-separation-20260505-1
file: data/en.wikipedia.org/wiki/Air_separation-1.md
category: reference
title: Air separation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Air_separation
date_saved: 2026-05-05T10:56:56.320357+00:00
instance: kb-cron
parent: air-separation-20260505-0
summary:
Pressure swing adsorption provides separation of oxygen or nitrogen from air without liquefaction. The process operates around ambient temperature; a zeolite (molecular sponge) is exposed to high pressure air, then the air is released and an adsorbed film of the desired gas is released. The size of compressor is much reduced over a liquefaction plant, and portable oxygen concentrators are made in this manner to provide oxygen-enriched air for medical purposes. Vacuum swing adsorption is a similar process; the product gas is evolved from the zeolite at sub-atmospheric pressure. Membrane technologies can provide alternate, lower-energy approaches to air separation. For example, a number of approaches are being explored for oxygen generation. Polymeric membranes operating at ambient or warm temperatures, for example, may be able to produce oxygen-enriched air (25-50% oxygen). Ceramic membranes can provide high-purity oxygen (90% or more) but require higher temperatures (800-900 deg C) to operate. These ceramic membranes include ion transport membranes (ITM) and oxygen transport membranes (OTM). Air Products and Chemicals Inc and Praxair are developing flat ITM and tubular OTM systems. Membrane gas separation is used to provide oxygen-poor and nitrogen-rich gases instead of air to fill the fuel tanks of jet liners, thus greatly


id: cascade-refrigeration-20260505-0
file: data/en.wikipedia.org/wiki/Cascade_refrigeration-0.md
category: reference
title: Cascade refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cascade_refrigeration
date_saved: 2026-05-05T10:56:57.506538+00:00
instance: kb-cron
parent: cascade-refrigeration-20260505-0
summary:
A cascade refrigeration cycle is a multi-stage thermodynamic cycle. An example two-stage process is shown at right (bottom on mobile). The cascade cycle is often employed for devices such as ULT freezers. In a cascade refrigeration system, two or more vapor-compression cycles with different refrigerants are used. The evaporation-condensation temperatures of each cycle are sequentially lower with some overlap to cover the total temperature drop desired, with refrigerants selected to work efficiently in the temperature range they cover. The low temperature system removes heat from the space to be cooled using an evaporator, and transfers it to a heat exchanger that is cooled by the evaporation of the refrigerant of the high temperature system. Alternatively, a liquid-to-liquid or similar heat exchanger may be used instead. The high-temperature system transfers heat to a conventional condenser that carries the entire heat output of the system and may be passive, fan, or water-cooled. Cascade cycles may be separated by either being sealed in separated loops or in what is referred to as an "auto-cascade", where the gases are compressed as a mixture but separated as one refrigerant condenses into a liquid while the other continues as a gas through the rest of the


id: coil-globule-transition-20260505-0
file: data/en.wikipedia.org/wiki/Coil–globule_transition-0.md
category: reference
title: Coil–globule transition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coil–globule_transition
date_saved: 2026-05-05T10:56:58.729143+00:00
instance: kb-cron
parent: coil-globule-transition-20260505-0
summary:
In polymer physics, the coil–globule transition is the collapse of a macromolecule from an expanded coil state through an ideal coil state to a collapsed globule state, or vice versa. The coil–globule transition is of importance in biology due to the presence of coil-globule transitions in biological macromolecules such as proteins and DNA. It is also analogous with the swelling behavior of a crosslinked polymer gel and is thus of interest in biomedical engineering for controlled drug delivery. A particularly prominent example of a polymer possessing a coil-globule transition of interest in this area is that of Poly(N-isopropylacrylamide) (PNIPAAm). == Description == In its coil state, the radius of gyration of the macromolecule scales as its chain length to the three-fifths power. As it passes through the coil–globule transition, it shifts to scaling as chain length to the half power (at the transition) and finally to the one third power in the collapsed state. The direction of the transition is often specified by the constructions 'coil-to-globule' or 'globule-to-coil' transition. == Origin == This transition is associated with the transition of a polymer chain from good solvent behavior through ideal or theta solvent behavior to poor solvent behavior. The canonical coil–globule


id: dissipation-20260505-0
file: data/en.wikipedia.org/wiki/Dissipation-0.md
category: reference
title: Dissipation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dissipation
date_saved: 2026-05-05T10:56:59.949966+00:00
instance: kb-cron
parent: dissipation-20260505-0
summary:
In thermodynamics, dissipation is the result of an irreversible process that affects a thermodynamic system. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, where the capacity of the final form to do thermodynamic work is less than that of the initial form. For example, transfer of energy as heat is dissipative because it is a transfer of energy other than by thermodynamic work or by transfer of matter, and spreads previously concentrated energy. Following the second law of thermodynamics, in conduction and radiation from one body to another, the entropy varies with temperature (reduces the capacity of the combination of the two bodies to do work), but never decreases in an isolated system. In mechanical engineering, dissipation is the irreversible conversion of mechanical energy into thermal energy with an associated increase in entropy. Processes with defined local temperature produce entropy at a certain rate. The entropy production rate times local temperature gives the dissipated power. Important examples of irreversible processes are: heat flow through a thermal resistance, fluid flow through a flow resistance, diffusion (mixing), chemical reactions, and electric current flow through an electrical resistance (Joule heating).


id: electron-bifurcation-20260505-0
file: data/en.wikipedia.org/wiki/Electron_bifurcation-0.md
category: reference
title: Electron bifurcation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_bifurcation
date_saved: 2026-05-05T10:57:01.118901+00:00
instance: kb-cron
parent: electron-bifurcation-20260505-0
summary:
In biochemistry, electron bifurcation (EB) refers to a system that enables an unfavorable (endergonic) transformation by coupling to a favorable (exergonic) transformation. Two electrons are involved: one flows to an acceptor with a "higher reduction potential and the other with a lower reduction potential" than the donor. The process is suspected of being common in bioenergetics. Two versions of EB are recognized. One involves redox of quinones and the other involves flavins. Quinones and flavins are cofactors that are capable of undergoing 2 e− – 2 proton redox. A pervasive example of electron bifurcation is the Q cycle, which is part of the machinery that results in oxidative phosphorylation. In that case one electron from ubiquinol is directed to a Rieske cluster and the other electron is directed to a cytochrome b. == References ==


id: endergonic-reaction-20260505-0
file: data/en.wikipedia.org/wiki/Endergonic_reaction-0.md
category: reference
title: Endergonic reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Endergonic_reaction
date_saved: 2026-05-05T10:57:02.332457+00:00
instance: kb-cron
parent: endergonic-reaction-20260505-0
summary:
In chemical thermodynamics, an endergonic reaction (from Greek ἔνδον (endon) 'within' and ἔργον (ergon) 'work'; also called a heat absorbing nonspontaneous reaction or an unfavorable reaction) is a chemical reaction in which the standard change in free energy is positive, and an additional driving force is needed to perform this reaction. In layman's terms, the total amount of useful energy is negative (it takes more energy to start the reaction than what is received out of it) so the total energy is a net negative result, as opposed to a net positive result in an exergonic reaction. Another way to phrase this is that useful energy must be absorbed from the surroundings into the workable system for the reaction to happen. Under constant temperature and constant pressure conditions, this means that the change in the standard Gibbs free energy would be positive, Δ G ∘ > 0 {\displaystyle \Delta G^{\circ }>0} for the reaction at standard state (i.e. at standard pressure (1 bar), and standard concentrations (1 molar) of all the reagents). In metabolism, an endergonic process is anabolic, meaning that energy is stored; in many such anabolic processes, energy is supplied by coupling the reaction to adenosine triphosphate (ATP)


id: endothermic-process-20260505-0
file: data/en.wikipedia.org/wiki/Endothermic_process-0.md
category: reference
title: Endothermic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Endothermic_process
date_saved: 2026-05-05T10:57:03.568543+00:00
instance: kb-cron
parent: endothermic-process-20260505-0
summary:
An endothermic process is a chemical or physical process that absorbs heat from its surroundings. In terms of thermodynamics, it is a thermodynamic process with an increase in the enthalpy H (or internal energy U) of the system. In an endothermic process, the heat that a system absorbs is thermal energy transfer into the system. Thus, an endothermic reaction generally leads to a decrease in the temperature of the surroundings. The term was coined by 19th-century French chemist Marcellin Berthelot. The term endothermic comes from the Greek ἔνδον (endon) meaning 'within' and θερμ- (therm) meaning 'hot' or 'warm'. An endothermic process may be a chemical process, such as dissolving ammonium nitrate (NH4NO3) in water (H2O), or a physical process, such as the melting of ice cubes. The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. Thus, endo in endothermic refers to energy or heat going in, and exo in exothermic refers to energy or heat going out. In each term (endothermic and exothermic) the prefix refers to where heat (or electrical energy) goes as the process occurs. == In chemistry ==


id: exergonic-process-20260505-0
file: data/en.wikipedia.org/wiki/Exergonic_process-0.md
category: reference
title: Exergonic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Exergonic_process
date_saved: 2026-05-05T10:57:04.702364+00:00
instance: kb-cron
parent: exergonic-process-20260505-0
summary:
An exergonic process is one which there is a positive flow of energy from the system to the surroundings. This is in contrast with an endergonic process. Constant pressure, constant temperature reactions are exergonic if and only if the Gibbs free energy change is negative (∆G < 0). "Exergonic" (from the prefix exo-, derived for the Greek word ἔξω exō, "outside" and the suffix -ergonic, derived from the Greek word ἔργον ergon, "work") means "releasing energy in the form of work". In thermodynamics, work is defined as the energy moving from the system (the internal region) to the surroundings (the external region) during a given process. All physical and chemical systems in the universe follow the second law of thermodynamics and proceed in a downhill, i.e., exergonic, direction. Thus, left to itself, any physical or chemical system will proceed, according to the second law of thermodynamics, in a direction that tends to lower the free energy of the system, and thus to expend energy in the form of work. These reactions occur spontaneously. A chemical reaction is also exergonic when spontaneous. Thus in this type of reactions the Gibbs free energy decreases. The entropy is included in any change of


id: exergonic-reaction-20260505-0
file: data/en.wikipedia.org/wiki/Exergonic_reaction-0.md
category: reference
title: Exergonic reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Exergonic_reaction
date_saved: 2026-05-05T10:57:05.879383+00:00
instance: kb-cron
parent: exergonic-reaction-20260505-0
summary:
In chemical thermodynamics, an exergonic reaction is a chemical reaction where the change in the free energy is negative (there is a net release of free energy). This indicates a spontaneous reaction if the system is closed and initial and final temperatures are the same. For processes that take place in a closed system at constant pressure and temperature, the Gibbs free energy is used, whereas the Helmholtz energy is relevant for processes that take place at constant volume and temperature. Any reaction occurring at constant temperature without input of electrical or photon energy is exergonic, according to the second law of thermodynamics. An example is cellular respiration. Symbolically, the release of free energy, ⁠ G {\displaystyle G} ⁠, in an exergonic reaction (at constant pressure and temperature) is denoted as Δ G = G p − G r < 0. {\displaystyle \Delta G=G_{\rm {p}}-G_{\rm {r}}<0.\,} Although exergonic reactions are said to occur spontaneously, this does not imply that the reaction will take place at an observable rate. For instance, the disproportionation of hydrogen peroxide releases free energy but is very slow in the absence of a suitable catalyst. It has been suggested that eager would be a more intuitive


id: exothermic-process-20260505-0
file: data/en.wikipedia.org/wiki/Exothermic_process-0.md
category: reference
title: Exothermic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Exothermic_process
date_saved: 2026-05-05T10:57:07.159794+00:00
instance: kb-cron
parent: exothermic-process-20260505-0
summary:
In thermodynamics, an exothermic process (from Ancient Greek έξω (éxō) 'outward' and θερμικός (thermikós) 'thermal') is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term exothermic was coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy, usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). == Two types of chemical reactions == Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: === Exothermic === An exothermic reaction occurs when heat is released to the surroundings. According to the IUPAC, an exothermic reaction is "a reaction for which the overall standard enthalpy change ΔH° is negative". Some examples of exothermic process are fuel combustion, condensation and nuclear fission, which is used in nuclear power plants to release large amounts of energy. === Endothermic === In


id: gas-slug-20260505-0
file: data/en.wikipedia.org/wiki/Gas_slug-0.md
category: reference
title: Gas slug
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gas_slug
date_saved: 2026-05-05T10:57:08.375191+00:00
instance: kb-cron
parent: gas-slug-20260505-0
summary:
A gas slug is a conglomerate of high pressure gas bubbles that forms within certain volcanoes, the agitation of which is a driving factor in Strombolian eruptions. They start out as small bubbles of gas inside of volcanic magma. These accumulate into one large bubble, which starts to rise through the lava plume. Gas slugs also consist of many chemical properties that assist scientists in monitoring volcanic eruptions. == Chemistry == Volcanic eruptions consist of mostly water vapor gases, with sulfur dioxide and carbon dioxide playing a huge part in gas release as well. Volcanic gases also rely on the composition of magma in the chamber of the volcano and gas separation processes before the point of eruption. Taylor bubbles, named after G. I. Taylor, refer to elongated gas bubbles in a liquid flow of a system. Taylor bubbles are distinctly "bullet shaped" and are involved in fluid dynamics. Within volcanic activity, magma rises in the volcanic chamber, slowing the movement of gas particles (H2O, SO2, CO2) and allowing for them to separate. As a result, this creates Taylor bubbles, which play a big part in Strombolian eruptions. == Formation == Once the accumulated slug reaches the top of the


id: isenthalpic-process-20260505-0
file: data/en.wikipedia.org/wiki/Isenthalpic_process-0.md
category: reference
title: Isenthalpic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isenthalpic_process
date_saved: 2026-05-05T10:57:09.549646+00:00
instance: kb-cron
parent: isenthalpic-process-20260505-0
summary:
An isenthalpic process or isoenthalpic process is a process that proceeds without any change in enthalpy, H; or specific enthalpy, h. If a steady-state, steady-flow process is analysed using a control volume, everything outside the control volume is considered to be the surroundings. == Definition and formula == Such a process will be isenthalpic if there is no transfer of heat to or from the surroundings, no work done on or by the surroundings, and no change in the kinetic energy of the fluid. This is a sufficient but not necessary condition for isoenthalpy. The necessary condition for a process to be isoenthalpic is that the sum of each of the terms of the energy balance other than enthalpy (work, heat, changes in kinetic energy, etc.) cancel each other, so that the enthalpy remains unchanged. For a process in which magnetic and electric effects (among others) give negligible contributions, the associated energy balance can be written as d K + d u = Q + W {\displaystyle dK+du=Q+W} d u = d ( h − P V ) = d h − d ( P V ) {\displaystyle du=d(h-PV)=dh-d(PV)} d K + d h − d ( P V )


id: isentropic-expansion-waves-20260505-0
file: data/en.wikipedia.org/wiki/Isentropic_expansion_waves-0.md
category: reference
title: Isentropic expansion waves
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_expansion_waves
date_saved: 2026-05-05T10:57:10.815910+00:00
instance: kb-cron
parent: isentropic-expansion-waves-20260505-0
summary:
In fluid dynamics, isentropic expansion waves are created when a supersonic flow is redirected along a curved surface. These waves are studied to obtain a relation between deflection angle and Mach number. Each wave in this case is a Mach wave, so it is at an angle α = sin − 1 ⁡ 1 M , {\displaystyle \alpha =\sin ^{-1}{\tfrac {1}{M}},} where M is the Mach number immediately before the wave. Expansion waves are divergent because as the flow expands the value of Mach number increases, thereby decreasing the Mach angle. In an isentropic wave, the speed changes from v to v + dv, with deflection dθ. We have oriented the coordinate system orthogonal to the wave. We write the basic equations (continuity, momentum and the first and second laws of thermodynamics) for this infinitesimal control volume. == Relation between θ, M and v == Assumptions: Steady flow. Negligible body forces. Adiabatic flow. No work terms. Negligible gravitational effect. The continuity equation is ∂ ∂ t ∫ C V ρ d V + ∫ C S ρ v ¯ d A ¯ = 0 ( 1.1 ) {\displaystyle {\frac {\partial }{\partial t}}\int \limits _{CV}\rho dV+\int \limits _{CS}\rho {\bar {v}}\,d{\bar {A}}=0\qquad


id: isentropic-expansion-waves-20260505-1
file: data/en.wikipedia.org/wiki/Isentropic_expansion_waves-1.md
category: reference
title: Isentropic expansion waves
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_expansion_waves
date_saved: 2026-05-05T10:57:10.815910+00:00
instance: kb-cron
parent: isentropic-expansion-waves-20260505-0
summary:
d v v = d M M − v d v 2 c p T = d M M − d v v 2 c p T 2 v = d M M − d v M 2 c 2 c p T 2 v = d M M − d v M 2 k R T c p T 2 v = d M M − d v [ M 2 ( k − 1 ) ] 2 v {\displaystyle {\begin{aligned}{\frac {dv}{v}}&={\frac {dM}{M}}-{\frac {vdv}{2c_{p}T}}\\[2pt]&={\frac {dM}{M}}-{\frac {dv{\frac {v^{2}}{c_{p}T}}}{2v}}\\[2pt]&={\frac {dM}{M}}-{\frac {dv{\frac {M^{2}c^{2}}{c_{p}T}}}{2v}}\\[2pt]&={\frac {dM}{M}}-{\frac {dv{\frac {M^{2}kRT}{c_{p}T}}}{2v}}\\[2pt]&={\frac {dM}{M}}-{\frac {dv[M^{2}(k-1)]}{2v}}\end{aligned}}} Hence, d v v = 2 2 + M 2 ( k − 1 ) d M M ( 1.7 ) {\displaystyle {\frac {dv}{v}}={\frac {2}{2+M^{2}(k-1)}}{\frac {dM}{M}}\qquad \qquad (1.7)} Combining (1.4) and (1.7) d θ 2 M 2 − 1 = − 1 2 + M 2 ( k − 1 ) d M M ( 1.8 ) {\displaystyle {\frac {d\theta }{2{\sqrt {M^{2}-1}}}}=-{\frac {1}{2+M^{2}(k-1)}}{\frac {dM}{M}}\qquad \qquad (1.8)} We generally apply the above equation to negative d θ {\displaystyle d\theta } , let d ω = d θ {\displaystyle d\omega =d\theta } . We can integrate this between the initial and final Mach numbers of given


id: isentropic-nozzle-flow-20260505-0
file: data/en.wikipedia.org/wiki/Isentropic_nozzle_flow-0.md
category: reference
title: Isentropic nozzle flow
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_nozzle_flow
date_saved: 2026-05-05T10:57:11.982282+00:00
instance: kb-cron
parent: isentropic-nozzle-flow-20260505-0
summary:
In fluid mechanics, isentropic nozzle flow describes the movement of a fluid through a narrow opening without an increase in entropy (an isentropic process). == Overview == Whenever a gas is forced through a tube, the gaseous molecules are deflected by the tube's walls. If the speed of the gas is much less than the speed of sound, the gas density will remain constant and the velocity of the flow will increase. However, as the speed of the flow approaches the speed of sound, compressibility effects on the gas are to be considered. The density of the gas becomes position dependent. While considering flow through a tube, if the flow is very gradually compressed (i.e. area decreases) and then gradually expanded (i.e. area increases), the flow conditions are restored (i.e. return to its initial position). So, such a process is a reversible process. According to the second law of thermodynamics, whenever there is a reversible and adiabatic flow, constant value of entropy is maintained. Engineers classify this type of flow as an isentropic flow of fluids. Isentropic is the combination of the Greek word "iso" (which means - same) and entropy. When the change in flow variables is small and


id: isentropic-nozzle-flow-20260505-1
file: data/en.wikipedia.org/wiki/Isentropic_nozzle_flow-1.md
category: reference
title: Isentropic nozzle flow
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_nozzle_flow
date_saved: 2026-05-05T10:57:11.982282+00:00
instance: kb-cron
parent: isentropic-nozzle-flow-20260505-0
summary:
== Flow analysis == The isentropic efficiency is h 1 − h 2 a h 1 − h 2 {\displaystyle {\frac {h_{1}-h_{2a}}{h_{1}-h_{2}}}} . The variation of fluid density for compressible flows requires attention to density and other fluid property relationships. The fluid equation of state, often unimportant for incompressible flows, is vital in the analysis of compressible flows. Also, temperature variations for compressible flows are usually significant and thus the energy equation is important. Curious phenomena can occur with compressible flows. For simplicity, the gas is assumed to be an ideal gas. The gas flow is isentropic. The gas flow is constant. The gas flow is along a straight line from gas inlet to exhaust gas exit. The gas flow behavior is compressible. There are numerous applications where a steady, uniform, isentropic flow is a good approximation to the flow in conduits. These include the flow through a jet engine, through the nozzle of a rocket, from a broken gas line, and past the blades of a turbine. M = Mach number V = velocity R = universal gas constant p = pressure k = specific heat ratio T = temperature * = sonic conditions ρ = density A =


id: isentropic-nozzle-flow-20260505-2
file: data/en.wikipedia.org/wiki/Isentropic_nozzle_flow-2.md
category: reference
title: Isentropic nozzle flow
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_nozzle_flow
date_saved: 2026-05-05T10:57:11.982282+00:00
instance: kb-cron
parent: isentropic-nozzle-flow-20260505-0
summary:
T ∗ = 0.833333 ⋅ T 0 p ∗ = 0.528282 ⋅ p 0 ρ ∗ = 0.633938 ⋅ ρ 0 {\displaystyle {\begin{aligned}T^{*}&=0.833333\cdot T_{0}\\p^{*}&=0.528282\cdot p_{0}\\\rho ^{*}&=0.633938\cdot \rho _{0}\end{aligned}}} The mass flux through the nozzle is of interest and is given by: m ˙ = ρ A V = p R T ⋅ A ⋅ M k R s p e c i f i c T = p k M m R T A M {\displaystyle {\dot {m}}=\rho AV={\frac {p}{RT}}\cdot A\cdot M{\sqrt {kR_{specific}T}}=p{\sqrt {kM_{m} \over RT}}AM} With the use of Eq. (9.28), the mass flux, after applying some algebra, can be expressed as m ˙ = p 0 M A k M m R T 0 ( 1 + k − 1 2 M 2 ) k + 1 − 2 ( k − 1 ) {\displaystyle {\dot {m}}=p_{0}MA{\sqrt {\frac {kM_{m}}{RT_{0}}}}\left(1+{\frac {k-1}{2}}M^{2}\right)^{\frac {k+1}{-2(k-1)}}} If the critical area is selected where M = 1, this takes the form m ˙ = p 0 A ∗ k M m R T 0 ( 1 + k − 1 2 ) k + 1 − 2 ( k − 1 ) {\displaystyle {\dot {m}}=p_{0}A^{*}{\sqrt {\frac {kM_{m}}{RT_{0}}}}\left(1+{\frac {k-1}{2}}\right)^{\frac {k+1}{-2(k-1)}}} which, when combined with previous


id: isentropic-process-20260505-0
file: data/en.wikipedia.org/wiki/Isentropic_process-0.md
category: reference
title: Isentropic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_process
date_saved: 2026-05-05T10:57:13.245109+00:00
instance: kb-cron
parent: isentropic-process-20260505-0
summary:
An isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. In thermodynamics, adiabatic processes are reversible. Clausius (1875) adopted "isentropic" as meaning the same as Rankine's word: "adiabatic". The work transfers of the system are frictionless, and there is no net transfer of heat or matter. Such an idealized process is useful in engineering as a model of and basis of comparison for real processes. This process is idealized because reversible processes do not occur in reality; thinking of a process as both adiabatic and reversible would show that the initial and final entropies are the same, thus, the reason it is called isentropic (entropy does not change). Thermodynamic processes are named based on the effect they would have on the system (ex. isovolumetric/isochoric: constant volume, isenthalpic: constant enthalpy). Even though in reality it is not necessarily possible to carry out an isentropic process, some may be approximated as such. The word "isentropic" derives from the process being one in which the entropy of the system remains unchanged, in addition to a process which is both adiabatic and reversible. == Background == The second law of thermodynamics states that T surr d S ≥ δ Q


id: isentropic-process-20260505-1
file: data/en.wikipedia.org/wiki/Isentropic_process-1.md
category: reference
title: Isentropic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isentropic_process
date_saved: 2026-05-05T10:57:13.245109+00:00
instance: kb-cron
parent: isentropic-process-20260505-0
summary:
Then for a process that is both reversible and adiabatic (i.e. no heat transfer occurs), δ Q rev = 0 {\displaystyle \delta Q_{\text{rev}}=0} , and so d S = δ Q rev / T = 0 {\displaystyle dS=\delta Q_{\text{rev}}/T=0} All reversible adiabatic processes are isentropic. This leads to two important observations: d U = δ W + δ Q = − p d V + 0 , {\displaystyle dU=\delta W+\delta Q=-p\,dV+0,} d H = δ W + δ Q + p d V + V d p = − p d V + 0 + p d V + V d p = V d p . {\displaystyle dH=\delta W+\delta Q+p\,dV+V\,dp=-p\,dV+0+p\,dV+V\,dp=V\,dp.} Next, a great deal can be computed for isentropic processes of an ideal gas. For any transformation of an ideal gas, it is always true that d U = n C v d T {\displaystyle dU=nC_{v}\,dT} , and d H = n C p d T . {\displaystyle dH=nC_{p}\,dT.} Using the general results derived above for d U {\displaystyle dU} and d H {\displaystyle dH} , then d U = n C v d T = − p d V , {\displaystyle dU=nC_{v}\,dT=-p\,dV,} d H = n C p


id: isobaric-process-20260505-0
file: data/en.wikipedia.org/wiki/Isobaric_process-0.md
category: reference
title: Isobaric process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isobaric_process
date_saved: 2026-05-05T10:57:14.483031+00:00
instance: kb-cron
parent: isobaric-process-20260505-0
summary:
In thermodynamics, an isobaric process is a type of thermodynamic process in which the pressure of the system stays constant: ΔP = 0. The heat transferred to the system does work, but also changes the internal energy (U) of the system. This article uses the physics sign convention for work, where positive work is work done by the system. Using this convention, by the first law of thermodynamics, Q = Δ U + W {\displaystyle Q=\Delta U+W\,} where W is work, U is internal energy, and Q is heat. Pressure-volume work by the closed system is defined as: W = ∫ p d V {\displaystyle W=\int \!p\,dV\,} where Δ means change over the whole process, whereas d denotes a differential. Since pressure is constant, this means that W = p Δ V {\displaystyle W=p\Delta V\,} . Applying the ideal gas law, this becomes W = n R Δ T {\displaystyle W=n\,R\,\Delta T} with R representing the gas constant, and n representing the amount of substance, which is assumed to remain constant (e.g., there is no phase transition during a chemical reaction). According to the equipartition theorem, the change in internal energy is related to the temperature of the system by


id: isobaric-process-20260505-1
file: data/en.wikipedia.org/wiki/Isobaric_process-1.md
category: reference
title: Isobaric process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isobaric_process
date_saved: 2026-05-05T10:57:14.483031+00:00
instance: kb-cron
parent: isobaric-process-20260505-0
summary:
In the first process example, a cylindrical chamber 1 m2 in area encloses 81.2438 mol of an ideal diatomic gas of molecular mass 29 g mol−1 at 300 K. The surrounding gas is at 1 atm and 300 K, and separated from the cylinder gas by a thin piston. For the limiting case of a massless piston, the cylinder gas is also at 1 atm pressure, with an initial volume of 2 m3. Heat is added slowly until the gas temperature is uniformly 600 K, after which the gas volume is 4 m3 and the piston is 2 m above its initial position. If the piston motion is sufficiently slow, the gas pressure at each instant will have practically the same value (psys = 1 atm) throughout. For a thermally perfect diatomic gas, the molar specific heat capacity at constant pressure (cp) is 7/2R or 29.1006 J mol−1 deg−1. The molar heat capacity at constant volume (cv) is 5/2R or 20.7862 J mol−1 deg−1. The ratio γ {\displaystyle \gamma } of the two heat capacities is 1.4. The heat Q required to bring the gas from 300 to 600 K is Q = Δ H = n c p Δ


id: isochoric-process-20260505-0
file: data/en.wikipedia.org/wiki/Isochoric_process-0.md
category: reference
title: Isochoric process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isochoric_process
date_saved: 2026-05-05T10:57:15.681952+00:00
instance: kb-cron
parent: isochoric-process-20260505-0
summary:
In thermodynamics, an isochoric process, also called a constant-volume process, an isovolumetric process, or an isometric process, is a thermodynamic process during which the volume of the closed system undergoing such a process remains constant. An isochoric process is exemplified by the heating or the cooling of the contents of a sealed, inelastic container: The thermodynamic process is the addition or removal of heat; the isolation of the contents of the container establishes the closed system; and the inability of the container to deform imposes the constant-volume condition. == Formalism == An isochoric thermodynamic quasi-static process is characterized by constant volume, i.e., ΔV = 0. The process does no pressure-volume work, since such work is defined by W = P Δ V , {\displaystyle W=P\Delta V,} where P is pressure. The sign convention is such that positive work is performed by the system on the environment. If the process is not quasi-static, the work can perhaps be done in a volume constant thermodynamic process. For a reversible process, the first law of thermodynamics gives the change in the system's internal energy: d U = d Q − d W {\displaystyle dU=dQ-dW} Replacing work with a change in volume gives d


id: isothermal-process-20260505-0
file: data/en.wikipedia.org/wiki/Isothermal_process-0.md
category: reference
title: Isothermal process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_process
date_saved: 2026-05-05T10:57:16.881965+00:00
instance: kb-cron
parent: isothermal-process-20260505-0
summary:
An isothermal process is a type of thermodynamic process in which the temperature T of a system remains constant: ΔT = 0. This typically occurs when a system is in contact with an outside thermal reservoir, and a change in the system occurs slowly enough to allow the system to be continuously adjusted to the temperature of the reservoir through heat exchange (see quasi-equilibrium). In contrast, an adiabatic process is where a system exchanges no heat with its surroundings (Q = 0). Simply, we can say that in an isothermal process T = constant {\displaystyle T={\text{constant}}} Δ T = 0 {\displaystyle \Delta T=0} d T = 0 {\displaystyle dT=0} For ideal gases only, internal energy Δ U = 0 {\displaystyle \Delta U=0} while in adiabatic processes: Q = 0. {\displaystyle Q=0.} == Etymology == The noun isotherm is derived from the Ancient Greek words ἴσος (ísos), meaning "equal", and θέρμη (thérmē), meaning "heat". == Examples == Isothermal processes can occur in any kind of system that has some means of regulating the temperature, including highly structured machines, and even living cells. Some parts of the cycles of some heat engines are carried out isothermally (for example, in the Carnot cycle).


id: isothermal-process-20260505-1
file: data/en.wikipedia.org/wiki/Isothermal_process-1.md
category: reference
title: Isothermal process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_process
date_saved: 2026-05-05T10:57:16.881965+00:00
instance: kb-cron
parent: isothermal-process-20260505-0
summary:
In IUPAC convention, work is defined as work on a system by its surroundings. If, for example, the system is compressed, then the work is done on the system by the surrounding so the work is positive and the internal energy of the system increases. Conversely, if the system expands (i.e., system surrounding expansion, so free expansions not the case), then the work is negative as the system does work on the surroundings. It is also worth noting that for ideal gases, if the temperature is held constant, the internal energy of the system U also is constant, and so ΔU = 0. Since the first law of thermodynamics states that ΔU = Q + W in IUPAC convention, it follows that Q = −W for the isothermal compression or expansion of ideal gases. == Example of an isothermal process == The reversible expansion of an ideal gas can be used as an example of work produced by an isothermal process. Of particular interest is the extent to which heat is converted to usable work, and the relationship between the confining force and the extent of expansion. During isothermal expansion of an ideal gas, both p and V change along


id: isothermal-process-20260505-2
file: data/en.wikipedia.org/wiki/Isothermal_process-2.md
category: reference
title: Isothermal process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_process
date_saved: 2026-05-05T10:57:16.881965+00:00
instance: kb-cron
parent: isothermal-process-20260505-0
summary:
Δ S = n R ln ⁡ P A P B {\displaystyle \Delta S=nR\ln {\frac {P_{\text{A}}}{P_{\text{B}}}}} . Once obtained, these formulas can be applied to an irreversible process, such as the free expansion of an ideal gas. Such an expansion is also isothermal and may have the same initial and final states as in the reversible expansion. Since entropy is a state function (that depends on an equilibrium state, not depending on a path that the system takes to reach that state), the change in entropy of the system is the same as in the reversible process and is given by the formulas above. Note that the result Q = 0 for the free expansion can not be used in the formula for the entropy change since the process is not reversible. The difference between the reversible and irreversible is found in the entropy of the surroundings. In both cases, the surroundings are at a constant temperature, T, so that ΔSsur = −⁠Q/T⁠; the minus sign is used since the heat transferred to the surroundings is equal in magnitude and opposite in sign to the heat Q transferred to the system. In the reversible case, the change in entropy of


id: mass-injection-flow-20260505-0
file: data/en.wikipedia.org/wiki/Mass_injection_flow-0.md
category: reference
title: Mass injection flow
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_injection_flow
date_saved: 2026-05-05T10:57:18.086943+00:00
instance: kb-cron
parent: mass-injection-flow-20260505-0
summary:
Mass injection flow (a.k.a. Limbach Flow) refers to inviscid, adiabatic flow through a constant area duct where the effect of mass addition is considered. For this model, the duct area remains constant, the flow is assumed to be steady and one-dimensional, and mass is added within the duct. Because the flow is adiabatic, unlike in Rayleigh flow, the stagnation temperature is a constant. Compressibility effects often come into consideration, though this flow model also applies to incompressible flow. For supersonic flow (an upstream Mach number greater than 1), deceleration occurs with mass addition to the duct and the flow can become choked. Conversely, for subsonic flow (an upstream Mach number less than 1), acceleration occurs and the flow can become choked given sufficient mass addition. Therefore, mass addition will cause both supersonic and subsonic Mach numbers to approach Mach 1, resulting in choked flow. == Theory == The 1D mass injection flow model begins with a mass-velocity relation derived for mass injection into a steady, adiabatic, frictionless, constant area flow of calorically perfect gas: d m m = − d u u ( M 2 − 1 ) {\displaystyle \ {\frac {dm}{m}}=-{\frac {du}{u}}\left(M^{2}-1\right)} where m {\displaystyle m} represents a mass


id: polytropic-process-20260505-0
file: data/en.wikipedia.org/wiki/Polytropic_process-0.md
category: reference
title: Polytropic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Polytropic_process
date_saved: 2026-05-05T10:57:19.316858+00:00
instance: kb-cron
parent: polytropic-process-20260505-0
summary:
A polytropic process is a thermodynamic process that obeys the relation: p V n = C {\displaystyle pV^{n}=C} where p is the pressure, V is volume, n is the polytropic index, and C is a constant. The polytropic process equation describes expansion and compression processes which include heat transfer. == Particular cases == Some specific values of n correspond to particular cases: n = 0 {\displaystyle n=0} for an isobaric process, n = + ∞ {\displaystyle n=+\infty } for an isochoric process. In addition, when the ideal gas law applies: n = 1 {\displaystyle n=1} for an isothermal process, n = γ {\displaystyle n=\gamma } for an isentropic process. Where γ {\displaystyle \gamma } is the ratio of the heat capacity at constant pressure ( C P {\displaystyle C_{P}} ) to heat capacity at constant volume ( C V {\displaystyle C_{V}} ). == Equivalence between the polytropic coefficient and the ratio of energy transfers == For an ideal gas in a closed system undergoing a slow process with negligible changes in kinetic and potential energy the process is polytropic, such that p v ( 1 − γ ) K + γ = C {\displaystyle pv^{(1-\gamma )K+\gamma }=C} where C is


id: quasistatic-process-20260505-0
file: data/en.wikipedia.org/wiki/Quasistatic_process-0.md
category: reference
title: Quasistatic process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quasistatic_process
date_saved: 2026-05-05T10:57:20.519703+00:00
instance: kb-cron
parent: quasistatic-process-20260505-0
summary:
In thermodynamics, a quasi-static process, also known as a quasi-equilibrium process (from Latin quasi, meaning ‘as if’), is a thermodynamic process that happens slowly enough for the system to remain in internal physical (but not necessarily chemical) thermodynamic equilibrium. An example of this is quasi-static expansion of a mixture of hydrogen and oxygen gas, where the volume of the system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process. Such an idealized process is a succession of physical equilibrium states, characterized by infinite slowness. Only in a quasi-static thermodynamic process can we exactly define intensive quantities (such as pressure, temperature, specific volume, specific entropy) of the system at any instant during the whole process; otherwise, since no internal equilibrium is established, different parts of the system would have different values of these quantities, so a single value per quantity may not be sufficient to represent the whole system. In other words, when an equation for a change in a state function contains P or T, it implies a quasi-static process. == Relation to reversible process == While all reversible processes are quasi-static, most authors do not require a general quasi-static


id: reversible-process-thermodynamics-20260505-0
file: data/en.wikipedia.org/wiki/Reversible_process_(thermodynamics)-0.md
category: reference
title: Reversible process (thermodynamics)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)
date_saved: 2026-05-05T10:57:21.720507+00:00
instance: kb-cron
parent: reversible-process-thermodynamics-20260505-0
summary:
In thermodynamics, a reversible process is a process, involving a system and its surroundings, whose direction can be reversed by infinitesimal changes in some properties of the surroundings, such as pressure or temperature. Throughout an entire reversible process, the system is in thermodynamic equilibrium, both physical and chemical, and nearly in pressure and temperature equilibrium with its surroundings. This prevents unbalanced forces and acceleration of moving system boundaries, which in turn avoids friction and other dissipation. To maintain equilibrium, reversible processes are extremely slow (quasistatic). The process must occur slowly enough that after some small change in a thermodynamic parameter, the physical processes in the system have enough time for the other parameters to self-adjust to match the new, changed parameter value. For example, if a container of water has sat in a room long enough to match the steady temperature of the surrounding air, for a small change in the air temperature to be reversible, the whole system of air, water, and container must wait long enough for the container and air to settle into a new, matching temperature before the next small change can occur. While processes in isolated systems are never reversible, cyclical processes can be reversible


id: supercooling-20260505-0
file: data/en.wikipedia.org/wiki/Supercooling-0.md
category: reference
title: Supercooling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Supercooling
date_saved: 2026-05-05T10:57:22.942902+00:00
instance: kb-cron
parent: supercooling-20260505-0
summary:
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. Per the established international definition, supercooling means "cooling a substance below the normal freezing point without solidification". While it can be achieved by different physical means, the postponed solidification is most often due to the absence of seed crystals or nuclei around which a crystal structure can form. The supercooling of water can be achieved without any special techniques other than chemical demineralization, down to −48.3 °C (−54.9 °F). Supercooled water can occur naturally, for example in the atmosphere, animals or plants. This phenomenon was first described in 1724 by Daniel Gabriel Fahrenheit, while developing the Fahrenheit scale. == Explanation == A liquid crossing its standard freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form creating a solid. Lacking any such nuclei, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs. Homogeneous nucleation can occur above the glass transition temperature, but if homogeneous nucleation has not occurred above that temperature, an amorphous (non-crystalline) solid will


id: supercooling-20260505-1
file: data/en.wikipedia.org/wiki/Supercooling-1.md
category: reference
title: Supercooling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Supercooling
date_saved: 2026-05-05T10:57:22.942902+00:00
instance: kb-cron
parent: supercooling-20260505-0
summary:
== In animals == In order to survive extreme low temperatures in certain environments, some animals use the phenomenon of supercooling that allow them to remain unfrozen and avoid cell damage and death. There are many techniques that aid in maintaining a liquid state, such as the production of antifreeze proteins, or AFPs, which bind to ice crystals to prevent water molecules from binding and spreading the growth of ice. The winter flounder is one such fish that utilizes these proteins to survive in its frigid environment. The liver secretes noncolligative proteins into the bloodstream. Other animals use colligative antifreezes, which increase the concentration of solutes in their bodily fluids, thus lowering their freezing point. Fish that rely on supercooling for survival must also live well below the water surface, because if they came into contact with ice nuclei they would freeze immediately. Animals that undergo supercooling to survive must also remove ice-nucleating agents from their bodies because they act as a starting point for freezing. Supercooling is also a common feature in some insect, reptile, and other ectotherm species. The potato cyst nematode larva (Globodera rostochiensis) could survive inside their cysts in a supercooled state to temperatures as low


id: supercooling-20260505-2
file: data/en.wikipedia.org/wiki/Supercooling-2.md
category: reference
title: Supercooling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Supercooling
date_saved: 2026-05-05T10:57:22.942902+00:00
instance: kb-cron
parent: supercooling-20260505-0
summary:
== Applications == One commercial application of supercooling is in refrigeration. Freezers can cool drinks to a supercooled level so that when they are opened, they form a slush. Another example is a product that can supercool the beverage in a conventional freezer. The Coca-Cola Company briefly marketed special vending machines containing Sprite in the UK, and Coke in Singapore, which stored the bottles in a supercooled state so that their content would turn to slush upon opening. Supercooling was successfully applied to organ preservation at Massachusetts General Hospital/Harvard Medical School. Livers that were later transplanted into recipient animals were preserved by supercooling for up to 4 days, quadrupling the limits of what could be achieved by conventional liver preservation methods. The livers were supercooled to a temperature of −6 °C (21 °F) in a specialized solution that protected against freezing and injury from the cold temperature. Another potential application is drug delivery. In 2015, researchers crystallized membranes at a specific time. Liquid-encapsulated drugs could be delivered to the site and, with a slight environmental change, the liquid rapidly changes into a crystalline form that releases the drug. In 2016, a team at Iowa State University proposed a method for


id: superheating-20260505-0
file: data/en.wikipedia.org/wiki/Superheating-0.md
category: reference
title: Superheating
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Superheating
date_saved: 2026-05-05T10:57:24.142400+00:00
instance: kb-cron
parent: superheating-20260505-0
summary:
In thermodynamics, superheating (sometimes referred to as boiling retardation, or boiling delay) is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling. This is a so-called metastable state or metastate, where boiling might occur at any time, induced by external or internal effects. Superheating is achieved by heating a homogeneous substance in a clean container, free of nucleation sites, while taking care not to disturb the liquid. This may occur by microwaving water in a very smooth container. Disturbing the water may cause an unsafe eruption of hot water and result in burns. == Cause == Water is said to "boil" when bubbles of water vapor grow without bound, bursting at the surface. For a vapor bubble to expand, the temperature must be high enough that the vapor pressure exceeds the ambient pressure (the atmospheric pressure, primarily). Below that temperature, a water vapor bubble will shrink and vanish. Superheating is an exception to this simple rule; a liquid is sometimes observed not to boil even though its vapor pressure does exceed the ambient pressure. The cause is an additional force, the surface tension, which suppresses the growth of bubbles. Surface tension


id: thermodynamic-cycle-20260505-0
file: data/en.wikipedia.org/wiki/Thermodynamic_cycle-0.md
category: reference
title: Thermodynamic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_cycle
date_saved: 2026-05-05T10:57:25.331304+00:00
instance: kb-cron
parent: thermodynamic-cycle-20260505-0
summary:
A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state. In the process of passing through a cycle, the working fluid (system) may convert heat from a warm source into useful work, and dispose of the remaining heat to a cold sink, thereby acting as a heat engine. Conversely, the cycle may be reversed and use work to move heat from a cold source and transfer it to a warm sink thereby acting as a heat pump. If at every point in the cycle the system is in thermodynamic equilibrium, the cycle is reversible. Whether carried out reversibly or irreversibly, the net entropy change of the system is zero, as entropy is a state function. During a closed cycle, the system returns to its original thermodynamic state of temperature and pressure. Process quantities (or path quantities), such as heat and work are process dependent. For a cycle for which the system returns to its initial state the first law of thermodynamics applies: Δ U = E


id: thermodynamic-cycle-20260505-1
file: data/en.wikipedia.org/wiki/Thermodynamic_cycle-1.md
category: reference
title: Thermodynamic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_cycle
date_saved: 2026-05-05T10:57:25.331304+00:00
instance: kb-cron
parent: thermodynamic-cycle-20260505-0
summary:
1→2: Isentropic / adiabatic expansion: Constant entropy (s), Decrease in pressure (P), Increase in volume (v), Decrease in temperature (T) 2→3: Isochoric cooling: Constant volume(v), Decrease in pressure (P), Decrease in entropy (S), Decrease in temperature (T) 3→4: Isentropic / adiabatic compression: Constant entropy (s), Increase in pressure (P), Decrease in volume (v), Increase in temperature (T) 4→1: Isochoric heating: Constant volume (v), Increase in pressure (P), Increase in entropy (S), Increase in temperature (T) === Power cycles === Thermodynamic power cycles are the basis for the operation of heat engines, which supply most of the world's electric power and run the vast majority of motor vehicles. Power cycles can be organized into two categories: real cycles and ideal cycles. Cycles encountered in real world devices (real cycles) are difficult to analyze because of the presence of complicating effects (friction), and the absence of sufficient time for the establishment of equilibrium conditions. For the purpose of analysis and design, idealized models (ideal cycles) are created; these ideal models allow engineers to study the effects of major parameters that dominate the cycle without having to spend significant time working out intricate details present in the real cycle model. Power cycles can


id: thermodynamic-cycle-20260505-2
file: data/en.wikipedia.org/wiki/Thermodynamic_cycle-2.md
category: reference
title: Thermodynamic cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_cycle
date_saved: 2026-05-05T10:57:25.331304+00:00
instance: kb-cron
parent: thermodynamic-cycle-20260505-0
summary:
TOP (A) and BOTTOM (C) of the loop: a pair of parallel isobaric processes RIGHT (B) and LEFT (D) of the loop: a pair of parallel isochoric processes If the working substance is a perfect gas, U {\displaystyle U} is only a function of T {\displaystyle T} for a closed system since its internal pressure vanishes. Therefore, the internal energy changes of a perfect gas undergoing various processes connecting initial state a {\displaystyle a} to final state b {\displaystyle b} are always given by the formula Δ U = ∫ a b C v d T {\displaystyle \Delta U=\int _{a}^{b}C_{v}dT} Assuming that C v {\displaystyle C_{v}} is constant, Δ U = C v Δ T {\displaystyle \Delta U=C_{v}\Delta T} for any process undergone by a perfect gas. Under this set of assumptions, for processes A and C we have W = p Δ v {\displaystyle W=p\Delta v} and Q = C p Δ T {\displaystyle Q=C_{p}\Delta T} , whereas for processes B and D we have W = 0 {\displaystyle W=0} and Q = Δ U = C v Δ T {\displaystyle Q=\Delta U=C_{v}\Delta T} . The total work done per cycle is W c y c l e =


id: thermodynamic-efficiency-limit-20260505-0
file: data/en.wikipedia.org/wiki/Thermodynamic_efficiency_limit-0.md
category: reference
title: Thermodynamic efficiency limit
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_efficiency_limit
date_saved: 2026-05-05T10:57:26.518623+00:00
instance: kb-cron
parent: thermodynamic-efficiency-limit-20260505-0
summary:
The thermodynamic efficiency limit is the absolute maximum theoretically possible conversion efficiency of sunlight to electricity. Its value is about 86%, which is the Chambadal-Novikov efficiency, an approximation related to the Carnot limit, based on the temperature of the photons emitted by the Sun's surface. == Effect of band gap energy == Solar cells operate as quantum energy conversion devices, and are therefore subject to the thermodynamic efficiency limit. Photons with an energy below the band gap of the absorber material cannot generate an electron-hole pair, and so their energy is not converted to useful output and only generates heat if absorbed. For photons with an energy above the band gap energy, only a fraction of the energy above the band gap can be converted to useful output. When a photon of greater energy is absorbed, the excess energy above the band gap is converted to kinetic energy of the carrier recombination. The excess kinetic energy is converted to heat through phonon interactions as the kinetic energy of the carriers slows to equilibrium velocity. Hence, the solar energy cannot be converted to electricity beyond a certain limit. Solar cells with multiple band gap absorber materials improve efficiency by dividing the


id: thermodynamic-equilibrium-20260505-0
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-0.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
Thermodynamic equilibrium is a notion of thermodynamics with axiomatic status referring to an internal state of a single thermodynamic system, or a relation between several thermodynamic systems connected by more or less permeable or impermeable walls. In thermodynamic equilibrium, there are no net macroscopic flows of mass nor of energy within a system or between systems. In a system that is in its own state of internal thermodynamic equilibrium, not only is there an absence of macroscopic change, but there is an "absence of any tendency toward change on a macroscopic scale." Systems in mutual thermodynamic equilibrium are simultaneously in mutual thermal, mechanical, chemical, and radiative equilibria. Systems can be in one kind of mutual equilibrium, while not in others. In thermodynamic equilibrium, all kinds of equilibrium hold at once and indefinitely, unless disturbed by a thermodynamic operation. In a macroscopic equilibrium, perfectly or almost perfectly balanced microscopic exchanges occur; this is the physical explanation of the notion of macroscopic equilibrium. A thermodynamic system in a state of internal thermodynamic equilibrium has a spatially uniform temperature. Its intensive properties, other than temperature, may be driven to spatial inhomogeneity by an unchanging long-range force field imposed on it by its surroundings.


id: thermodynamic-equilibrium-20260505-1
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-1.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Relation of exchange equilibrium between systems == Often the surroundings of a thermodynamic system may also be regarded as another thermodynamic system. In this view, one may consider the system and its surroundings as two systems in mutual contact, with long-range forces also linking them. The enclosure of the system is the surface of contiguity or boundary between the two systems. In the thermodynamic formalism, that surface is regarded as having specific properties of permeability. For example, the surface of contiguity may be supposed to be permeable only to heat, allowing energy to transfer only as heat. Then the two systems are said to be in thermal equilibrium when the long-range forces are unchanging in time and the transfer of energy as heat between them has slowed and eventually stopped permanently; this is an example of a contact equilibrium. Other kinds of contact equilibrium are defined by other kinds of specific permeability. When two systems are in contact equilibrium with respect to a particular kind of permeability, they have common values of the intensive variable that belongs to that particular kind of permeability. Examples of such intensive variables are temperature, pressure, chemical potential. A contact equilibrium may be regarded


id: thermodynamic-equilibrium-20260505-2
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-2.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Multiple contact equilibrium == The thermodynamic formalism allows that a system may have contact with several other systems at once, which may or may not also have mutual contact, the contacts having respectively different permeabilities. If these systems are all jointly isolated from the rest of the world those of them that are in contact then reach respective contact equilibria with one another. If several systems are free of adiabatic walls between each other, but are jointly isolated from the rest of the world, then they reach a state of multiple contact equilibrium, and they have a common temperature, a total internal energy, and a total entropy. Amongst intensive variables, this is a unique property of temperature. It holds even in the presence of long-range forces. (That is, there is no "force" that can maintain temperature discrepancies.) For example, in a system in thermodynamic equilibrium in a vertical gravitational field, the pressure on the top wall is less than that on the bottom wall, but the temperature is the same everywhere. A thermodynamic operation may occur as an event restricted to the walls that are within the surroundings, directly affecting neither the walls of contact of the system of


id: thermodynamic-equilibrium-20260505-3
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-3.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Local and global equilibrium == It can be useful to distinguish between global and local thermodynamic equilibrium. In thermodynamics, exchanges within a system and between the system and the outside are controlled by intensive parameters. As an example, temperature controls heat exchanges. Global thermodynamic equilibrium (GTE) means that those intensive parameters are homogeneous throughout the whole system, while local thermodynamic equilibrium (LTE) means that those intensive parameters are varying in space and time, but are varying so slowly that, for any point, one can assume thermodynamic equilibrium in some neighborhood about that point. If the description of the system requires variations in the intensive parameters that are too large, the very assumptions upon which the definitions of these intensive parameters are based will break down, and the system will be in neither global nor local equilibrium. For example, it takes a certain number of collisions for a particle to equilibrate to its surroundings. If the average distance it has moved during these collisions removes it from the neighborhood it is equilibrating to, it will never equilibrate, and there will be no LTE. Temperature is, by definition, proportional to the average internal energy of an equilibrated neighborhood. Since there is


id: thermodynamic-equilibrium-20260505-4
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-4.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Definitions == The most general kind of thermodynamic equilibrium of a system is through contact with the surroundings that allows simultaneous passages of all chemical substances and all kinds of energy. A system in thermodynamic equilibrium may move with uniform acceleration through space but must not change its shape or size while doing so; thus it is defined by a rigid volume in space. It may lie within external fields of force, determined by external factors of far greater extent than the system itself, so that events within the system cannot in an appreciable amount affect the external fields of force. The system can be in thermodynamic equilibrium only if the external force fields are uniform, and are determining its uniform acceleration, or if it lies in a non-uniform force field but is held stationary there by local forces, such as mechanical pressures, on its surface. Thermodynamic equilibrium is a primitive notion of the theory of thermodynamics. According to P.M. Morse: "It should be emphasized that the fact that there are thermodynamic states, ..., and the fact that there are thermodynamic variables which are uniquely specified by the equilibrium state ... are not conclusions deduced logically from some philosophical


id: thermodynamic-equilibrium-20260505-5
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-5.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
He then writes: "When the conditions for all three types of equilibrium are satisfied, the system is said to be in a state of thermodynamic equilibrium". P.M. Morse writes that thermodynamics is concerned with "states of thermodynamic equilibrium". He also uses the phrase "thermal equilibrium" while discussing transfer of energy as heat between a body and a heat reservoir in its surroundings, though not explicitly defining a special term 'thermal equilibrium'. J.R. Waldram writes of "a definite thermodynamic state". He defines the term "thermal equilibrium" for a system "when its observables have ceased to change over time". But shortly below that definition he writes of a piece of glass that has not yet reached its "full thermodynamic equilibrium state". Considering equilibrium states, M. Bailyn writes: "Each intensive variable has its own type of equilibrium." He then defines thermal equilibrium, mechanical equilibrium, and material equilibrium. Accordingly, he writes: "If all the intensive variables become uniform, thermodynamic equilibrium is said to exist." He is not here considering the presence of an external force field. J.G. Kirkwood and I. Oppenheim define thermodynamic equilibrium as follows: "A system is in a state of thermodynamic equilibrium if, during the time period allotted for experimentation, (a)


id: thermodynamic-equilibrium-20260505-6
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-6.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Characteristics of a state of internal thermodynamic equilibrium == === Homogeneity in the absence of external forces === A thermodynamic system consisting of a single phase in the absence of external forces, in its own internal thermodynamic equilibrium, is homogeneous. This means that the material in any small volume element of the system can be interchanged with the material of any other geometrically congruent volume element of the system, and the effect is to leave the system thermodynamically unchanged. In general, a strong external force field makes a system of a single phase in its own internal thermodynamic equilibrium inhomogeneous with respect to some intensive variables. For example, a relatively dense component of a mixture can be concentrated by centrifugation. === Uniform temperature === Such equilibrium inhomogeneity, induced by external forces, does not occur for the intensive variable temperature. According to E.A. Guggenheim, "The most important conception of thermodynamics is temperature." Planck introduces his treatise with a brief account of heat and temperature and thermal equilibrium, and then announces: "In the following we shall deal chiefly with homogeneous, isotropic bodies of any form, possessing throughout their substance the same temperature and density, and subject to a uniform pressure acting


id: thermodynamic-equilibrium-20260505-7
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-7.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
=== Approach to thermodynamic equilibrium within an isolated system === When a body of material starts from a non-equilibrium state of inhomogeneity or chemical non-equilibrium, and is then isolated, it spontaneously evolves towards its own internal state of thermodynamic equilibrium. It is not necessary that all aspects of internal thermodynamic equilibrium be reached simultaneously; some can be established before others. For example, in many cases of such evolution, internal mechanical equilibrium is established much more rapidly than the other aspects of the eventual thermodynamic equilibrium. Another example is that, in many cases of such evolution, thermal equilibrium is reached much more rapidly than chemical equilibrium. === Fluctuations within an isolated system in its own internal thermodynamic equilibrium === In an isolated system, thermodynamic equilibrium by definition persists over an indefinitely long time. In classical physics it is often convenient to ignore the effects of measurement and this is assumed in the present account. To consider the notion of fluctuations in an isolated thermodynamic system, a convenient example is a system specified by its extensive state variables, internal energy, volume, and mass composition. By definition they are time-invariant. By definition, they combine with time-invariant nominal values of their conjugate intensive functions


id: thermodynamic-equilibrium-20260505-8
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-8.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
A system's internal state of thermodynamic equilibrium should be distinguished from a "stationary state" in which thermodynamic parameters are unchanging in time but the system is not isolated, so that there are, into and out of the system, non-zero macroscopic fluxes which are constant in time. Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. Many natural systems still today remain beyond the scope of currently known macroscopic thermodynamic methods. Laws governing systems which are far from equilibrium are also debatable. One of the guiding principles for these systems is the maximum entropy production principle. It states that a non-equilibrium system evolves such as to maximize its entropy production. == See also == Thermodynamic models Non-random two-liquid model (NRTL model) - Phase equilibrium calculations UNIQUAC model - Phase equilibrium calculations Time crystal Topics in control theory


id: thermodynamic-equilibrium-20260505-9
file: data/en.wikipedia.org/wiki/Thermodynamic_equilibrium-9.md
category: reference
title: Thermodynamic equilibrium
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_equilibrium
date_saved: 2026-05-05T10:57:27.731222+00:00
instance: kb-cron
parent: thermodynamic-equilibrium-20260505-0
summary:
== Cited bibliography == Adkins, C.J. (1968/1983). Equilibrium Thermodynamics, third edition, McGraw-Hill, London, ISBN 0-521-25445-0. Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, ISBN 0-88318-797-3. Beattie, J.A., Oppenheim, I. (1979). Principles of Thermodynamics, Elsevier Scientific Publishing, Amsterdam, ISBN 0-444-41806-7. Boltzmann, L. (1896/1964). Lectures on Gas Theory, translated by S.G. Brush, University of California Press, Berkeley. Buchdahl, H.A. (1966). The Concepts of Classical Thermodynamics, Cambridge University Press, Cambridge UK. Callen, H.B. (1960/1985). Thermodynamics and an Introduction to Thermostatistics, (1st edition 1960) 2nd edition 1985, Wiley, New York, ISBN 0-471-86256-8. Carathéodory, C. (1909). Untersuchungen über die Grundlagen der Thermodynamik, Mathematische Annalen, 67: 355–386. A translation may be found here. Also a mostly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA. Chapman, S., Cowling, T.G. (1939/1970). The Mathematical Theory of Non-uniform gases. An Account of the Kinetic Theory of Viscosity, Thermal Conduction and Diffusion in Gases, third edition 1970, Cambridge University Press, London. Crawford, F.H. (1963). Heat, Thermodynamics, and Statistical Physics, Rupert Hart-Davis, London, Harcourt, Brace & World, Inc. de Groot, S.R., Mazur, P. (1962). Non-equilibrium Thermodynamics, North-Holland, Amsterdam. Reprinted (1984), Dover Publications Inc.,


id: thermodynamic-system-20260505-0
file: data/en.wikipedia.org/wiki/Thermodynamic_system-0.md
category: reference
title: Thermodynamic system
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_system
date_saved: 2026-05-05T10:57:28.904227+00:00
instance: kb-cron
parent: thermodynamic-system-20260505-0
summary:
A thermodynamic system is a body of matter and/or radiation separate from its surroundings that can be studied using the laws of thermodynamics. Thermodynamic systems can be passive and active according to internal processes. According to internal processes, passive systems and active systems are distinguished: passive, in which there is a redistribution of available energy, active, in which one type of energy is converted into another. Depending on its interaction with the environment, a thermodynamic system may be an isolated system, a closed system, or an open system. An isolated system does not exchange matter or energy with its surroundings. A closed system may exchange heat, experience forces, and exert forces, but does not exchange matter. An open system can interact with its surroundings by exchanging both matter and energy. The physical condition of a thermodynamic system at a given time is described by its state, which can be specified by the values of a set of thermodynamic state variables. A thermodynamic system is in thermodynamic equilibrium when there are no macroscopically apparent flows of matter or energy within it or between it and other systems. == Overview == Thermodynamic equilibrium is characterized not only by the absence of any


id: thermodynamic-system-20260505-1
file: data/en.wikipedia.org/wiki/Thermodynamic_system-1.md
category: reference
title: Thermodynamic system
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_system
date_saved: 2026-05-05T10:57:28.904227+00:00
instance: kb-cron
parent: thermodynamic-system-20260505-0
summary:
== Systems in equilibrium == In isolated systems it is consistently observed that as time goes on internal rearrangements diminish and stable conditions are approached. Pressures and temperatures tend to equalize, and matter arranges itself into one or a few relatively homogeneous phases. A system in which all processes of change have gone practically to completion is considered in a state of thermodynamic equilibrium. The thermodynamic properties of a system in equilibrium are unchanging in time. Equilibrium system states are much easier to describe in a deterministic manner than non-equilibrium states. In some cases, when analyzing a thermodynamic process, one can assume that each intermediate state in the process is at equilibrium. Such a process is called quasistatic. For a process to be reversible, each step in the process must be reversible. For a step in a process to be reversible, the system must be in equilibrium throughout the step. That ideal cannot be accomplished in practice because no step can be taken without perturbing the system from equilibrium, but the ideal can be approached by making changes slowly. The very existence of thermodynamic equilibrium, defining states of thermodynamic systems, is the essential, characteristic, and most fundamental postulate of thermodynamics,


id: thermodynamic-system-20260505-2
file: data/en.wikipedia.org/wiki/Thermodynamic_system-2.md
category: reference
title: Thermodynamic system
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_system
date_saved: 2026-05-05T10:57:28.904227+00:00
instance: kb-cron
parent: thermodynamic-system-20260505-0
summary:
Adiabatic boundary – not allowing any heat exchange: A thermally isolated system Rigid boundary – not allowing exchange of work: A mechanically isolated system One example is fluid being compressed by a piston in a cylinder. Another example of a closed system is a bomb calorimeter, a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Electrical energy travels across the boundary to produce a spark between the electrodes and initiates combustion. Heat transfer occurs across the boundary after combustion but no mass transfer takes place either way. The first law of thermodynamics for energy transfers for closed system may be stated: Δ U = Q − W {\displaystyle \Delta U=Q-W} where U {\displaystyle U} denotes the internal energy of the system, Q {\displaystyle Q} heat added to the system, W {\displaystyle W} the work done by the system. For infinitesimal changes the first law for closed systems may stated: d U = δ Q − δ W . {\displaystyle \mathrm {d} U=\delta Q-\delta W.} If the work is due to a volume expansion by d V {\displaystyle \mathrm {d} V} at a pressure P {\displaystyle P} then: δ W = P d V


id: thermodynamic-system-20260505-3
file: data/en.wikipedia.org/wiki/Thermodynamic_system-3.md
category: reference
title: Thermodynamic system
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_system
date_saved: 2026-05-05T10:57:28.904227+00:00
instance: kb-cron
parent: thermodynamic-system-20260505-0
summary:
== Selective transfer of matter == For a thermodynamic process, the precise physical properties of the walls and surroundings of the system are important, because they determine the possible processes. An open system has one or several walls that allow transfer of matter. To account for the internal energy of the open system, this requires energy transfer terms in addition to those for heat and work. It also leads to the idea of the chemical potential. A wall selectively permeable only to a pure substance can put the system in diffusive contact with a reservoir of that pure substance in the surroundings. Then a process is possible in which that pure substance is transferred between system and surroundings. Also, across that wall a contact equilibrium with respect to that substance is possible. By suitable thermodynamic operations, the pure substance reservoir can be dealt with as a closed system. Its internal energy and its entropy can be determined as functions of its temperature, pressure, and mole number. A thermodynamic operation can render impermeable to matter all system walls other than the contact equilibrium wall for that substance. This allows the definition of an intensive state variable, with respect to a reference


id: thermodynamic-system-20260505-4
file: data/en.wikipedia.org/wiki/Thermodynamic_system-4.md
category: reference
title: Thermodynamic system
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermodynamic_system
date_saved: 2026-05-05T10:57:28.904227+00:00
instance: kb-cron
parent: thermodynamic-system-20260505-0
summary:
== Sources == Abbott, M.M.; van Hess, H. G. (1989). Thermodynamics with Chemical Applications (2nd ed.). McGraw Hill. Bailyn, M. (1994). A Survey of Thermodynamics. New York: American Institute of Physics Press. ISBN 0-88318-797-3. Callen, H. B. (1985) [1960]. Thermodynamics and an Introduction to Thermostatistics (2nd ed.). New York: Wiley. ISBN 0-471-86256-8. Carnot, Sadi (1824). Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance (in French). Paris: Bachelier. Haase, R. (1971). "Survey of Fundamental Laws". In Eyring, H.; Henderson, D.; Jost, W. (eds.). Thermodynamics. Physical Chemistry: An Advanced Treatise. Vol. 1. New York: Academic Press. pp. 1–97. LCCN 73-117081. Dobroborsky B.S. Machine safety and the human factor / Edited by Doctor of Technical Sciences, prof. S.A. Volkov. — St. Petersburg: SPbGASU, 2011. — pp. 33–35. — 114 p. — ISBN 978-5-9227-0276-8. (Ru) Halliday, David; Resnick, Robert; Walker, Jearl (2008). Fundamentals of Physics (8th ed.). Wiley. Moran, Michael J.; Shapiro, Howard N. (2008). Fundamentals of Engineering Thermodynamics (6th ed.). Wiley. Rex, Andrew; Finn, C. B. P. (2017). Finn's Thermal Physics (3rd ed.). Taylor & Francis. ISBN 978-1-498-71887-5. Tisza, László (1966). Generalized Thermodynamics. MIT Press. Tschoegl, N. W. (2000). Fundamentals of Equilibrium and Steady-State Thermodynamics.


id: thermogravitational-cycle-20260505-0
file: data/en.wikipedia.org/wiki/Thermogravitational_cycle-0.md
category: reference
title: Thermogravitational cycle
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermogravitational_cycle
date_saved: 2026-05-05T10:57:30.084117+00:00
instance: kb-cron
parent: thermogravitational-cycle-20260505-0
summary:
A thermogravitational cycle is a reversible thermodynamic cycle using the gravitational works of weight and buoyancy to respectively compress and expand a working fluid. == Theoretical framework == Consider a column filled with a transporting medium and a balloon filled with a working fluid. Due to the hydrostatic pressure of the transporting medium, the pressure inside the column increases along the z axis (see figure). Initially, the balloon is inflated by the working fluid at temperature TC and pressure P0 and located on top of the column. A thermogravitational cycle is decomposed into four ideal steps: 1→2: Descent of the balloon towards the bottom of the column. The working fluid undergoes adiabatic compression with its temperature increasing and its pressure reaching value Ph at the bottom (Ph>P0). 2→3: While the ballon lays at the bottom, the working fluid receives heat from the hot source at temperature TH and undergoes isobaric expansion at pressure Ph. 3→4: The balloon rises towards the column top. The working fluid undergoes adiabatic expansion with a drop in temperature and reaches pressure P0 after expansion when the balloon is on top. 4→1: Once arrived on top, the working fluid supplies heat to the cold source at


id: transpiration-cooling-20260505-0
file: data/en.wikipedia.org/wiki/Transpiration_cooling-0.md
category: reference
title: Transpiration cooling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transpiration_cooling
date_saved: 2026-05-05T10:57:31.278415+00:00
instance: kb-cron
parent: transpiration-cooling-20260505-0
summary:
Transpiration cooling is a thermodynamic process where cooling is achieved by a process of moving a liquid or a gas through the wall of a structure to absorb some portion of the heat energy from the structure while simultaneously actively reducing the convective and radiative heat flux coming into the structure from the surrounding space. One approach to transpiration cooling is to move liquid through small pores in the outer wall of a body leading to evaporation of the liquid to a gas via the physical mechanism of evaporative cooling. Other approaches are possible. == Applications == Transpiration cooling is used in the aerospace industry, in jet and rocket engines. In 2018, researchers at the University of Oxford were experimentally testing transpiration cooling as a Thermal Protection System for Hypersonic Vehicles such as rockets or spaceplanes. Transpiration cooling is one of a variety of cooling techniques that may be used to reduce regenerative cooling loads in rocket engines and subsequently reduce propellant requirements. Other techniques exist, such as film cooling, ablative cooling, radiative cooling, heat sink cooling and dump cooling. Transpiration cooling is being considered for use in space vehicles reentering the Earth's atmosphere at hypersonic velocities where a transpirationally


id: charles-karsner-mills-20260505-0
file: data/en.wikipedia.org/wiki/Charles_Karsner_Mills-0.md
category: reference
title: Charles Karsner Mills
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Charles_Karsner_Mills
date_saved: 2026-05-05T10:57:32.860331+00:00
instance: kb-cron
parent: charles-karsner-mills-20260505-0
summary:
Charles Karsner Mills, M.D. (December 4, 1845 – May 28, 1931) was an American physician and a pioneer in neurology. He founded the first neurology department in a general hospital in the United States at the Philadelphia General Hospital in 1877 and served as chief of neurology at the Hospital of the University of Pennsylvania. He was a professor of neurology at the University of Pennsylvania from 1877 to 1915. He founded the Philadelphia Polyclinic and taught there as professor of diseases of the mind and nervous system from 1883 to 1898. He led major reforms to psychiatric hospitals in the Philadelphia area including the closing of the Blockley Almshouse and the construction of the Philadelphia General Hospital and Byberry Hospital for Mental Diseases. He published over 300 scientific papers on neurology topics including cerebral localization, electrotherapeutics, aphasias and the effects of tumors in the central nervous system. In 1900, he first described a case of ascending paralysis, a rare motor neuron condition that has become known as Mills' syndrome. == Early life and education == Mills was born on December 4, 1845, in Philadelphia, Pennsylvania, to James and Lavinia Ann (Fitzgerald) Mills. He attended Central High School but left


id: silas-weir-mitchell-physician-20260505-0
file: data/en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)-0.md
category: reference
title: Silas Weir Mitchell (physician)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)
date_saved: 2026-05-05T10:57:34.104016+00:00
instance: kb-cron
parent: silas-weir-mitchell-physician-20260505-0
summary:
Silas Weir Mitchell (February 15, 1829 – January 4, 1914) was an American physician, scientist, novelist, and poet. He is considered the father of medical neurology, and he discovered causalgia (complex regional pain syndrome) and erythromelalgia, and pioneered the rest cure. == Early life == Silas Weir Mitchell was born on February 15, 1829, in Philadelphia, Pennsylvania, to prominent physician and writer John Kearsley Mitchell (1792–1858) and Sarah Henry Mitchell (1800–1872). His father was a doctor and pathologist interested in snake venom, and Mitchell would continue his research later on. Dr. Mitchell studied at the University of Pennsylvania and later earned the degree of MD at the city's Jefferson Medical College in 1850. == Career == During the Civil War, he was director of treatment of nervous injuries and maladies at Turner's Lane Hospital, Philadelphia, and at the close of the war became a specialist in neurology. In this field Mitchell pioneered the rest cure for diseases now termed "psychiatric", particularly neurasthenia and hysteria, subsequently taken up by the medical world. The treatment consisted primarily in isolation, confinement to bed, dieting, electrotherapy and massage; and was popularly known as 'Dr Diet and Dr Quiet'. Mitchell also urged his female patients


id: silas-weir-mitchell-physician-20260505-1
file: data/en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)-1.md
category: reference
title: Silas Weir Mitchell (physician)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)
date_saved: 2026-05-05T10:57:34.104016+00:00
instance: kb-cron
parent: silas-weir-mitchell-physician-20260505-0
summary:
John Kearsley Mitchell (1859–1917), a neurologist who married Anne Keppele Williams in 1890. Langdon Elwyn Mitchell (1862–1935), a playwright who married actress Marion Lea in 1891. On June 23, 1875, Mitchell was married to Mary Cadwalader (1835–1914), who was from one of Philadelphia's most prestigious families. She was a daughter of Thomas McCall Cadwalader and Maria Charlotte Gouverneur (niece of Elizabeth Kortright, who had married U.S. President James Monroe). The marriage "propelled him to one of the city's highest social circles and he became a trustee of the University of Pennsylvania the following year." Together, they were the parents of a daughter: Marie Gouverneur Cadwalader Mitchell (1876–1898), who died unmarried. Mitchell died on January 4, 1914, in Philadelphia and is interred at The Woodlands Cemetery. His widow died a week after his funeral. === Cultural Club Founder === Mitchell and 8 other members of the University Club at Penn founded The Franklin Inn Club in 1902. === Art patron === He was a friend and patron of the artist Thomas Eakins, and owned the painting Whistling for Plover. The Philadelphia Chippendale chairs seen in several Eakins paintings – such as William Rush Carving his Allegorical Figure of Schuylkill River (1877)


id: silas-weir-mitchell-physician-20260505-2
file: data/en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)-2.md
category: reference
title: Silas Weir Mitchell (physician)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silas_Weir_Mitchell_(physician)
date_saved: 2026-05-05T10:57:34.104016+00:00
instance: kb-cron
parent: silas-weir-mitchell-physician-20260505-0
summary:
== Further reading == Anna Robeson Brown Burr, Weir Mitchell: His Life and Letters (Duffield & Company 1929). Nancy Cervetti, S. Weir Mitchell, 1829–1914: Philadelphia's Literary Physician. University Park, PA: Pennsylvania State University Press, 2012. ISBN 0271054042 E. P. Oberholtzer, "Personal Memories of Weir Mitchell," in the Bookman, vol. 39 (1914). p. 132 A. Proust and G. Ballet, The Treatment of Neurasthenia. 1902. Tucker, Beverly R., S. Weir Mitchell. Gorham Press, Boston, 1914. Talcott Williams, "Dr. S. Weir Mitchell" in the Century Magazine, vol. 57 (1898). Talcott Williams, in several articles in the Book News Monthly, vol. 26 (1907). A Catalogue of the Scientific and Literary Work of S. Weir Mitchell. Philadelphia, 1894. == External links == Finding aid to the S. Weir Mitchell collection at the University of Pennsylvania Libraries Silas Weir Mitchell. Biography at WhoNamedIt Silas Weir Mitchell papers from the Historic Psychiatry Collection, Menninger Archives, Kansas Historical Society Works by Silas Weir Mitchell at Project Gutenberg Works by or about Silas Weir Mitchell at the Internet Archive Works by Silas Weir Mitchell in the Ball State University Digital Media Repository Portrait of Silas Weir Mitchell by John Singer Sargent Archived July 5, 2007, at the Wayback Machine


id: andr-strohl-20260505-0
file: data/en.wikipedia.org/wiki/André_Strohl-0.md
category: reference
title: André Strohl
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/André_Strohl
date_saved: 2026-05-05T10:57:35.333123+00:00
instance: kb-cron
parent: andr-strohl-20260505-0
summary:
André Strohl (20 March 1887 – 10 March 1977) was a French physiologist who was a native of Poitiers. He is remembered for his role in the diagnosis of Guillain–Barré syndrome (sometimes called Guillain–Barré–Strohl syndrome), a form of areflexic paralysis that exhibits normal cell count but with an abnormal increase in spinal fluid protein. The syndrome is named after two French neurologists; Georges Guillain and Jean Alexandre Barré. In 1916, during World War I, Strohl was serving in the Neurological Centre of the French Sixth Army with Guillain and Barré. The three doctors noticed that two soldiers, who were suffering from muscular weakening and pain along with paresthesias, had an unexpected amount of spinal fluid protein production. Strohl is credited with performing the electrophysiological tests on the soldiers. Eventually, the two patients were able to recover from their illness. In 1916, Guillain, Barré and Strohl reported their findings in a medical journal. In 1927, H. Draganesco and J. Claudion coined the term "Guillain–Barré syndrome", apparently overlooking Strohl's contributions. In 1924 Strohl became a professor of physiological medicine in Algiers, and two years later acquired the same position at the University of Paris. He retired from there in 1957. He was


id: lag-ri-hasan-elebi-20260505-0
file: data/en.wikipedia.org/wiki/Lagâri_Hasan_Çelebi-0.md
category: reference
title: Lagâri Hasan Çelebi
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lagâri_Hasan_Çelebi
date_saved: 2026-05-05T10:59:25.395421+00:00
instance: kb-cron
parent: lag-ri-hasan-elebi-20260505-0
summary:
Lagâri Hasan Çelebi was an Ottoman scientist, engineer and aviator who, according to the account written by traveller Evliya Çelebi, made a successful crewed rocket flight. == Account == Evliya Çelebi reported that in 1633, Lagari Hasan Çelebi blasted off from Sarayburnu, (the promontory below the Topkapı Palace in Istanbul) in a 7-winged rocket propelled by 50 okka (140 lbs) of gunpowder. The flight was said to have been undertaken at the time of the birth of Sultan Murad IV's daughter. As Evliya Celebi wrote, Lagari proclaimed before launching his craft "O my sultan! Be blessed, I am going to talk to Jesus!"; after ascending in the rocket, he landed in the sea, swimming ashore and joking "O my sultan! Jesus sends his regards to you!"; he was rewarded by the Sultan with silver and the rank of sipahi in the Ottoman army. Evliya Çelebi also mentioned another aviation pioneer, Hezârfen Ahmed Çelebi, making a flight by glider a year earlier. == Popular culture == Istanbul Beneath My Wings is a 1996 film about the lives of Lagari Hasan Çelebi, his brother and fellow aviator Hezârfen Ahmed Çelebi, and Ottoman society in the early 17th century as witnessed and narrated


id: edward-forman-20260505-0
file: data/en.wikipedia.org/wiki/Edward_Forman-0.md
category: reference
title: Edward Forman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Edward_Forman
date_saved: 2026-05-05T10:59:26.610331+00:00
instance: kb-cron
parent: edward-forman-20260505-0
summary:
Edward Seymour Forman (December 3, 1912 – February 12, 1973) was an American engineer and inventor known for his pioneering work in early rocketry in the United States. Forman, along with his collaborators in Guggenheim Aeronautical Laboratory at the California Institute of Technology (GALCIT), demonstrated the first practical jet-assisted take-off (JATO) of an aircraft in the United States. Forman was among the GALCIT innovators that went on to found Aerojet General Corporation, the largest rocket technology manufacturer in the 1940s, and the GALCIT Rocket Research Group itself became the precursor of the Jet Propulsion Laboratory. == Early life and education == Forman was born in Gillespie, Illinois, the youngest of four brothers. The family moved to Pasadena, California and Forman attended Washington Junior High School, where he met Jack Parsons, who would become his lifelong collaborator and friend. Forman found Parsons, who was two years younger than he, being bullied at school and rescued him. Soon after that, the two boys grew a strong bond over their common interest in science fiction. Forman was an avid reader of the Barsoom series by Edgar Rice Burroughs, which is quoted as having influenced a generation of scientists and thinkers, including Carl Sagan.


id: edward-forman-20260505-1
file: data/en.wikipedia.org/wiki/Edward_Forman-1.md
category: reference
title: Edward Forman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Edward_Forman
date_saved: 2026-05-05T10:59:26.610331+00:00
instance: kb-cron
parent: edward-forman-20260505-0
summary:
=== GALCIT Rocket Research Group === In the early 1930s, Forman and Parsons began to realize that the rocket technology was a more complex subject than they had first assumed. They corresponded with rocketry experts on both sides of the Atlantic, but Forman later reminisced that they learned very little beyond the fact that nobody else had yet achieved much.In 1935, a Los Angeles Times article titled “Rocket Plane Visualized Flying 1200 Miles Hour” caught the pair's eyes. The article covered a paper by William Bollay, an aeronautics graduate student at Caltech, on the works of Austrian engineer Eugen Sänger. When they approached Bollay, he directed them to Frank Malina, another graduate student, who was pursuing studies in rocket propulsion. Malina shared their enthusiasm about rocketry and agreed to join their efforts. The trio put together a research proposal to request funding from Caltech. Initially, Foreman and Parsons wanted to propose the development of a sounding rocket, but Malina argued in favor of a more fundamental project aimed at understanding the thermodynamics in a rocket engine through static tests. Malina later recounted that "Parsons and Forman were not too pleased with an austere program that did not include at least


id: robert-esnault-pelterie-20260505-0
file: data/en.wikipedia.org/wiki/Robert_Esnault-Pelterie-0.md
category: reference
title: Robert Esnault-Pelterie
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_Esnault-Pelterie
date_saved: 2026-05-05T10:59:27.835008+00:00
instance: kb-cron
parent: robert-esnault-pelterie-20260505-0
summary:
Robert Albert Charles Esnault-Pelterie (French pronunciation: [ʁɔbɛʁ albɛʁ ʃaʁl eno pɛltəʁi]; 8 November 1881 – 6 December 1957) was a French aircraft designer and spaceflight theorist. He is referred to as being one of the founders of modern rocketry and astronautics, along with the Russian Konstantin Tsiolkovsky, the Chinese Qian Xuesen, the Germans Hermann Oberth, Wernher von Braun and the American Robert H. Goddard. == Biography == He was born on 8 November 1881 in Paris to a textile industrialist. He was educated at the Faculté des Sciences, studying engineering at the Sorbonne. He served in World War I and was made an Officier de la Légion d'Honneur. In November 1928, on board the Ile de France while sailing to New York City, he was married to Carmen Bernaldo de Quirós, the daughter of Don Antonio and Yvonne Cabarrus, and granddaughter of General Marquis of Santiago, Grandee of Spain, Head of the Military Household of Queen Isabella II. He died on 6 December 1957 in Nice, France. == REP == Esnault-Pelterie developed and manufactured aeroplanes and aero engines under the name REP. === Aeroplanes === His first experiments in aviation were based on the Wright brothers 1902 glider. His first


id: robert-esnault-pelterie-20260505-1
file: data/en.wikipedia.org/wiki/Robert_Esnault-Pelterie-1.md
category: reference
title: Robert Esnault-Pelterie
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_Esnault-Pelterie
date_saved: 2026-05-05T10:59:27.835008+00:00
instance: kb-cron
parent: robert-esnault-pelterie-20260505-0
summary:
== Prix REP-Hirsch == The Prix REP-Hirsch was an international award of the Société astronomique de France given in recognition of the study of interplanetary travel and astronautics. Established by Esnault-Pelterie and André-Louis Hirsch, a Parisian banker and science enthusiast, it was the first prize for astronautics in the world. The award was given "to recognize the best original scientific work, theoretical or experimental, that is able to advance one of the questions related to the realisation of space travel, or to increase human understanding of one of the branches related to the science of astronautics." The idea for establishing the prize originated during a dinner Hirsch and Esnault-Pelterie organised in Paris on 26 December 1927. The guests discussed the emerging science of space travel, which they called “astronautics” at the suggestion of science fiction writer J.H. Rosny the elder. Hirsch and Esnault-Pelterie provided funds – 5,000 francs annually for 1928, 1929, and 1930 – to the Société astronomique de France, for an annual award in astronautics in their names. A Comité d'Astronautique was established to manage the prize. In addition to Esnault-Pelterie, Hirsch, and Rosny the elder, it included General Gustave-Auguste Ferrié (President), Jean Perrin and Eugène Fichot (Vice-Presidents)


id: robert-h-goddard-20260505-0
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-0.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American physicist, inventor, and engineer credited with creating and building the world's first liquid-fueled rocket, which was successfully launched on March 16, 1926. By 1915 his pioneering work had dramatically improved the efficiency of the solid-fueled rocket, signaling the era of the modern rocket and innovation. He and his team launched 34 rockets between 1926 and 1941, achieving altitudes as high as 2.6 km (1.6 mi) and speeds as fast as 885 km/h (550 mph). Goddard's work as both theorist and engineer anticipated many of the developments that would make spaceflight possible. He has been called the man who ushered in the Space Age. Two of Goddard's 214 patented inventions, a multi-stage rocket (1914), and a liquid-fuel rocket (1914), were important milestones toward spaceflight. His 1919 monograph A Method of Reaching Extreme Altitudes is considered one of the classic texts of 20th-century rocket science. Goddard successfully pioneered modern methods such as two-axis control (gyroscopes and steerable thrust) to allow rockets to control their flight effectively. Although his work in the field was revolutionary, Goddard received little public or financial support for his research and development work. He was


id: robert-h-goddard-20260505-1
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-1.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
On this day I climbed a tall cherry tree at the back of the barn ... and as I looked toward the fields at the east, I imagined how wonderful it would be to make some device which had even the possibility of ascending to Mars, and how it would look on a small scale, if sent up from the meadow at my feet. I have several photographs of the tree, taken since, with the little ladder I made to climb it, leaning against it. It seemed to me then that a weight whirling around a horizontal shaft, moving more rapidly above than below, could furnish lift by virtue of the greater centrifugal force at the top of the path. I was a different boy when I descended the tree from when I ascended. Existence at last seemed very purposive. For the rest of his life, he observed October 19 as "Anniversary Day", a private commemoration of the day of his greatest inspiration. == Education and early studies == The young Goddard was a thin and frail boy, almost always in fragile health. He suffered from stomach problems, pleurisy, colds, and bronchitis, and he fell two years behind his classmates.


id: robert-h-goddard-20260505-2
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-2.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
=== First scientific writings === The high-school student summed up his ideas on space travel in a proposed article, "The Navigation of Space," which he submitted to the Popular Science News. The journal's editor returned it, saying that they could not use it "in the near future." While still an undergraduate, Goddard wrote a paper proposing a method for balancing airplanes using gyro-stabilization. He submitted the idea to Scientific American, which published the paper in 1907. Goddard later wrote in his diaries that he believed his paper was the first proposal of a way to automatically stabilize aircraft in flight. His proposal came around the same time as other scientists were making breakthroughs in developing functional gyroscopes. While studying physics at WPI, ideas came to Goddard's mind that sometimes seemed impossible, but he was compelled to record them for future investigation. He wrote that "there was something inside which simply would not stop working." He purchased some cloth-covered notebooks and began filling them with a variety of thoughts, mostly concerning his dream of space travel. He considered centrifugal force, radio waves, magnetic reaction, solar energy, atomic energy, ion or electrostatic propulsion and other methods to reach space. After experimenting with


id: robert-h-goddard-20260505-3
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-3.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
=== Foundational patents === In the technological and manufacturing atmosphere of Worcester, patents were considered essential, not only to protect original work but as documentation of first discovery. He began to see the importance of his ideas as intellectual property, and thus began to secure those ideas before someone else did—and he would have to pay to use them. In May 1913, he wrote descriptions concerning his first rocket patent applications. His father brought them to a patent lawyer in Worcester who helped him to refine his ideas for consideration. Goddard's first patent application was submitted in October 1913. In 1914, his first two landmark patents were accepted and registered. The first, U.S. patent 1,102,653, described a multi-stage rocket fueled with a solid "explosive material." The second, U.S. patent 1,103,503, described a rocket fueled with a solid fuel (explosive material) or with liquid propellants (gasoline and liquid nitrous oxide). The two patents would eventually become important milestones in the history of rocketry. Overall, 214 patents were published, some posthumously by his wife. == Early rocketry research == In the fall of 1914 Goddard's health had improved, and he accepted a part-time position as an instructor and research fellow at Clark


id: robert-h-goddard-20260505-4
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-4.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
=== Smithsonian Institution sponsorship === By 1916, the cost of Goddard's rocket research had become too great for his modest teaching salary to bear. He began to solicit potential sponsors for financial assistance, beginning with the Smithsonian Institution, the National Geographic Society, and the Aero Club of America. In his letter to the Smithsonian in September 1916, Goddard claimed he had achieved a 63% efficiency and a nozzle velocity of almost 2438 meters per second. With these performance levels, he believed a rocket could vertically lift a weight of 1 lb (0.45 kg) to a height of 232 miles (373 km) with an initial launch weight of only 89.6 lbs (40.64 kg). (Earth's atmosphere can be considered to end at 80 to 100 miles (130 to 160 km) altitude, where its drag effect on orbiting satellites becomes minimal.) The Smithsonian was interested and asked Goddard to elaborate upon his initial inquiry. Goddard responded with a detailed manuscript he had already prepared, entitled A Method of Reaching Extreme Altitudes. In January 1917, the Smithsonian agreed to provide Goddard with a five-year grant totaling US$5000. Afterward, Clark was able to contribute US$3500 and the use of their physics lab to the project.


id: robert-h-goddard-20260505-5
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-5.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
== A Method of Reaching Extreme Altitudes == In 1919 Goddard thought that it would be premature to disclose the results of his experiments because his engine was not sufficiently developed. Webster realized that Goddard had accomplished a good deal of fine work and insisted that Goddard publish his progress so far or he would take care of it himself, so Goddard asked the Smithsonian Institution if it would publish the report, updated with notes, that he had submitted in late 1916. In late 1919, the Smithsonian published Goddard's groundbreaking work, A Method of Reaching Extreme Altitudes. The report describes Goddard's mathematical theories of rocket flight, his experiments with solid-fuel rockets, and the possibilities he saw of exploring Earth's atmosphere and beyond. Along with Konstantin Tsiolkovsky's earlier work, The Exploration of Cosmic Space by Means of Reaction Devices, Goddard's report is regarded as one of the pioneering works of the science of rocketry, and 1750 copies were distributed worldwide. Goddard also sent a copy to individuals who requested one, until his personal supply was exhausted. Smithsonian aerospace historian Frank Winter said that this paper was "one of the key catalysts behind the international rocket movement of the 1920s and 30s."


id: robert-h-goddard-20260505-6
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-6.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
As a method of sending a missile to the higher, and even highest, part of the earth's atmospheric envelope, Professor Goddard's multiple-charge rocket is a practicable, and therefore promising device. Such a rocket, too, might carry self-recording instruments, to be released at the limit of its flight, and conceivable parachutes would bring them safely to the ground. It is not obvious, however, that the instruments would return to the point of departure; indeed, it is obvious that they would not, for parachutes drift exactly as balloons do. The article pressed further on Goddard's proposal to launch rockets beyond the atmosphere: [A]fter the rocket quits our air and really starts on its longer journey, its flight would be neither accelerated nor maintained by the explosion of the charges it then might have left. To claim that it would be is to deny a fundamental law of dynamics, and only Dr. Einstein and his chosen dozen, so few and fit, are licensed to do that. ... Of course, [Goddard] only seems to lack the knowledge ladled out daily in high schools. Thrust is however possible in a vacuum. ==== Aftermath ==== A week after the New York Times editorial, Goddard released a


id: robert-h-goddard-20260505-7
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-7.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
Goddard began experimenting with liquid oxidizer, liquid fuel rockets in September 1921, and successfully tested the first liquid propellant engine in November 1923. It had a cylindrical combustion chamber, using impinging jets to mix and atomize liquid oxygen and gasoline. In 1924–25, Goddard had problems developing a high-pressure piston pump to send fuel to the combustion chamber. He wanted to scale up the experiments, but his funding would not allow such growth. He decided to forgo the pumps and use a pressurized fuel feed system applying pressure to the fuel tank from a tank of inert gas, a technique that is still used today. The liquid oxygen, some of which evaporated, provided its own pressure. On December 6, 1925, he tested the simpler pressure feed system. He conducted a static test on the firing stand at the Clark University physics laboratory. The engine successfully lifted its own weight in a 27-second test in the static rack. It was a major success for Goddard, proving that a liquid fuel rocket was possible. The test moved Goddard an important step closer to launching a rocket with liquid fuel. Goddard conducted an additional test in December, and two more in January 1926. After


id: robert-h-goddard-20260505-8
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-8.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
=== Guggenheim sponsorship === In the spring of 1930, Lindbergh finally found an ally in the Guggenheim family. Financier Daniel Guggenheim agreed to fund Goddard's research over the next four years for a total of $100,000 (~$2.4 million today). The Guggenheim family, especially Harry Guggenheim, would continue to support Goddard's work in the years to come. The Goddards soon moved to Roswell, New Mexico Because of the military potential of the rocket, Goddard, Lindbergh, Harry Guggenheim, the Smithsonian Institution and others tried in 1940, before the U.S. entered World War II, to convince the Army and Navy of its value. Goddard's services were offered, but there was no interest, initially. Two young, imaginative military officers eventually got the services to attempt to contract with Goddard just prior to the war. The Navy beat the Army to the punch and secured his services to build variable-thrust, liquid-fueled rocket engines for jet-assisted take-off (JATO) of aircraft. These rocket engines were the precursors to the larger throttlable rocket plane engines that helped launch the space age. Astronaut Buzz Aldrin wrote that his father, Edwin Aldrin Sr. "was an early supporter of Robert Goddard." The elder Aldrin was a student of physics under Goddard


id: robert-h-goddard-20260505-9
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-9.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
With new financial backing, Goddard eventually relocated to the Eden Valley Test Site in Roswell, New Mexico, in summer of 1930, where he worked with his team of technicians in near-isolation and relative secrecy for years. He had consulted a meteorologist as to the best area to do his work, and Roswell seemed ideal. Here they would not endanger anyone, would not be bothered by the curious and would experience a more moderate climate (which was also better for Goddard's health). The locals valued personal privacy, knew Goddard desired his, and when travelers asked where Goddard's facilities were located, they would likely be misdirected. By September 1931, his rockets had the now familiar appearance of a smooth casing with tail-fins. He began experimenting with gyroscopic guidance and made a flight test of such a system in April 1932. A gyroscope mounted on gimbals electrically controlled steering vanes in the exhaust, similar to the system used by the German V-2 over 10 years later. Though the rocket crashed after a short ascent, the guidance system had worked, and Goddard considered the test a success. A temporary loss of funding from the Guggenheims, as a result of the depression, forced Goddard in


id: robert-h-goddard-20260505-10
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-10.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
=== General Jimmy Doolittle === Jimmy Doolittle was introduced to the field of space science at an early point in its history. He recalls in his autobiography, "I became interested in rocket development in the 1930s when I met Robert H. Goddard, who laid the foundation. ... While with Shell Oil I worked with him on the development of a type of fuel. ... " Harry Guggenheim and Charles Lindbergh arranged for (then Major) Doolittle to discuss with Goddard a special blend of gasoline. Doolittle flew himself to Roswell in October 1938 and was given a tour of Goddard's shop and a "short course" in rocketry. He then wrote a memo, including a rather detailed description of Goddard's rocket. In closing he said, "interplanetary transportation is probably a dream of the very distant future, but with the moon only a quarter of a million miles away—who knows!" In July 1941, he wrote Goddard that he was still interested in his rocket propulsion research. The Army was interested only in JATO at this point. However, Doolittle and Lindbergh were concerned about the state of rocketry in the US, and Doolittle remained in touch with Goddard. Shortly after World War II, Doolittle


id: robert-h-goddard-20260505-11
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-11.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
== Annapolis, Maryland == Navy Lieutenant Charles F. Fischer, who had visited Goddard in Roswell earlier and gained his confidence, believed Goddard was doing valuable work and was able to convince the Bureau of Aeronautics in September 1941 that Goddard could build the JATO unit the Navy desired. While still in Roswell, and before the Navy contract took effect, Goddard began in September to apply his technology to build a variable-thrust engine to be attached to a PBY seaplane. By May 1942, he had a unit that could meet the Navy's requirements and be able to launch a heavily loaded aircraft from a short runway. In February, he received part of a PBY with bullet holes apparently acquired in the Pearl Harbor attack. Goddard wrote to Guggenheim that "I can think of nothing that would give me greater satisfaction than to have it contribute to the inevitable retaliation." In April, Fischer notified Goddard that the Navy wanted to do all its rocket work at the Engineering Experiment Station at Annapolis. Esther, worried that a move to the climate of Maryland would cause Robert's health to deteriorate faster, objected. But the patriotic Goddard replied, "Esther, don't you know there's a war


id: robert-h-goddard-20260505-12
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-12.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
In its 1942 crash effort to perfect an aircraft booster, the Navy was beginning to learn its way in rocketry. In similar efforts, the Army Air Corps was also exploring the field [with GALCIT]. Compared to Germany's massive program, these beginnings were small, yet essential to later progress. They helped develop a nucleus of trained American rocket engineers, the first of the new breed who would follow the professor into the Age of Space. In August 1943, President Atwood at Clark wrote to Goddard that the university was losing the acting head of the physics department, was taking on "emergency work" for the army, and he was to "report for duty or declare the position vacant." Goddard replied that he believed he was needed by the navy, was nearing retirement age, and was unable to lecture because of his throat problem, which did not allow him to talk above a whisper. He regretfully resigned as professor of physics and expressed his deepest appreciation for all Atwood and the trustees had done for him and indirectly for the war effort. In June he had gone to see a throat specialist in Baltimore, who recommended that he not talk at all, to


id: robert-h-goddard-20260505-13
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-13.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
In the spring of 1945, Goddard saw a captured German V-2 ballistic missile, in the naval laboratory in Annapolis, Maryland, where he had been working under contract. The unlaunched rocket had been captured by the US Army from the Mittelwerk factory in the Harz mountains in Germany and samples began to be shipped by Special Mission V-2 on 22 May 1945. After a thorough inspection, Goddard was convinced that the Germans had "stolen" his work. Though the design details were not exactly the same, the basic design of the V-2 was similar to one of Goddard's rockets. The V-2, however, was technically far more advanced than the most successful of the rockets designed and tested by Goddard. The Peenemünde rocket group led by Wernher von Braun may have benefited from the pre-1939 contacts to a limited extent, but had also started from the work of their own space pioneer, Hermann Oberth; they also had the benefit of intensive state funding, large-scale production facilities (using slave labor), and repeated flight-testing that allowed them to refine their designs. Oberth was a space flight theorist and had never built a rocket, but he tested small liquid propellant thrust chambers in 1929–30 which were


id: robert-h-goddard-20260505-14
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-14.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
== Goddard's secrecy == Goddard avoided sharing details of his work with other scientists and preferred to work alone with his technicians. Frank Malina, who was then studying rocketry at the California Institute of Technology, visited Goddard in August 1936. Goddard hesitated to discuss any of his research, other than that which had already been published in Liquid-Propellant Rocket Development. Theodore von Kármán, Malina's mentor at the time, was unhappy with Goddard's attitude and later wrote, "Naturally we at Caltech wanted as much information as we could get from Goddard for our mutual benefit. But Goddard believed in secrecy. ... The trouble with secrecy is that one can easily go in the wrong direction and never know it." However, at an earlier point, von Kármán said that Malina was "highly enthusiastic" after his visit and that Caltech made changes to their liquid-propellant rocket, based on Goddard's work and patents. Malina remembered his visit as friendly and that he saw all but a few components in Goddard's shop. Goddard's concerns about secrecy led to criticism for failure to cooperate with other scientists and engineers. His approach at that time was that independent development of his ideas without interference would bring quicker


id: robert-h-goddard-20260505-15
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-15.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
== Personal life == On June 21, 1924, Goddard married Esther Christine Kisk (March 31, 1901 – June 4, 1982), a secretary in Clark University's President's office, whom he had met in 1919. She became enthusiastic about rocketry and photographed some of his work as well as aided him in his experiments and paperwork, including accounting. They enjoyed going to the movies in Roswell and participated in community organizations such as the Rotary and the Woman's Club. He painted the New Mexican scenery, sometimes with the artist Peter Hurd, and played the piano. She played bridge, while he read. Esther said Robert participated in the community and readily accepted invitations to speak to church and service groups. The couple did not have children. After his death, she sorted out Goddard's papers, and secured 131 additional patents on his work. She also filmed some of the experiments that took place across the course of Goddard's research. Concerning Goddard's religious views, he was raised as an Episcopalian, though he was not outwardly religious. The Goddards were associated with the Episcopal church in Roswell, and he attended occasionally. He once spoke to a young people's group on the relationship of science and religion.


id: robert-h-goddard-20260505-16
file: data/en.wikipedia.org/wiki/Robert_H._Goddard-16.md
category: reference
title: Robert H. Goddard
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Robert_H._Goddard
date_saved: 2026-05-05T10:59:29.313605+00:00
instance: kb-cron
parent: robert-h-goddard-20260505-0
summary:
U.S. patent 1,102,653 – Rocket apparatus U.S. patent 1,103,503 – Rocket apparatus U.S. patent 2395113A – Mechanism for feeding combustion liquids to rocket apparatus U.S. patent 2397657A – Control mechanism for rocket apparatus U.S. patent 2397659A – Control mechanism for rocket apparatus U.S. patent 2511979A – Vacuum tube transportation system – E. C. Goddard The Guggenheim Foundation and Goddard's estate filed suit in 1951 against the U.S. government for prior infringement of three of Goddard's patents. In 1960, the parties settled the suit, and the U.S. armed forces and NASA paid out an award of $1 million: half of the award settlement went to his wife, Esther. At that time, it was the largest government settlement ever paid in a patent case. The settlement amount exceeded the total amount of all the funding that Goddard received for his work, throughout his entire career. === Important firsts === First American to explore mathematically the practicality of using rocket propulsion to reach high altitudes and to traject to the Moon (1912) First to receive a U.S. patent on the idea of a multistage rocket (1914) First to static test a rocket in a systematic, scientific manner, measuring thrust, exhaust velocity and efficiency.


id: william-moore-mathematician-20260505-0
file: data/en.wikipedia.org/wiki/William_Moore_(mathematician)-0.md
category: reference
title: William Moore (mathematician)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Moore_(mathematician)
date_saved: 2026-05-05T10:59:30.502385+00:00
instance: kb-cron
parent: william-moore-mathematician-20260505-0
summary:
William Moore (fl. 1806 – c. 1823) was a British mathematician and early contributor to rocket theory. He worked at the Royal Military Academy, Woolwich. His 1813 Treatise was the first exposition of rocket mechanics based on Newton's third law of motion. Little is known of his life, because many relevant historical documents were destroyed by German bombing in World War II. == Publications == Theory on the motion of Rockets (1810) A Treatise on the Doctrine of Fluxations (1811) A Treatise on the Motion of Rockets; to which is added, an Essay on Naval Gunnery (1813) == See also == Konstantin Tsiolkovsky Tsiolkovsky rocket equation == References ==


id: hermann-oberth-20260505-0
file: data/en.wikipedia.org/wiki/Hermann_Oberth-0.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
Hermann Julius Oberth (German: [ˈhɛrman ˈjuːli̯ʊs ˈoːbɛrt]; 25 June 1894 – 28 December 1989) was an Austro-Hungarian-born German physicist and rocket pioneer of Transylvanian Saxon descent. Oberth supported Nazi Germany's war effort and received the War Merit Cross (1st Class) in 1943. == Early life == Oberth was born into a Transylvanian Saxon family in Nagyszeben (Hermannstadt), Kingdom of Hungary (today Sibiu in Romania); and besides his native German, he was fluent in Hungarian and Romanian as well. At the age of 11, Oberth's interest in rocketry was sparked by the novels of Jules Verne, especially From the Earth to the Moon and Around the Moon. He was fond of reading them over and over until they were engraved in his memory. As a result, Oberth constructed his first model rocket as a school student at the age of 14. In his youthful experiments, he arrived independently at the concept of the multistage rocket. During this time, however, he lacked the resources to put his ideas into practice. In 1912, Oberth began studying medicine in Munich, Germany, but after World War I broke out, he was drafted into the Imperial German Army, assigned to an infantry battalion, and sent to


id: hermann-oberth-20260505-1
file: data/en.wikipedia.org/wiki/Hermann_Oberth-1.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
Oberth's student Max Valier joined forces with Fritz von Opel to create the world's first large-scale experimental rocket program Opel-RAK, leading to speed records for ground and rail vehicles and the world's first rocket plane. Opel RAK.1, a purpose-built design by Julius Hatry, was demonstrated to the public and world media on September 30, 1929, piloted by von Opel. Valier's and von Opel's demonstrations had a strong and long-lasting impact on later spaceflight pioneers, in particular on another of Oberth's students, Wernher von Braun. Shortly after the Opel RAK team's successful liquid-fuel rocket launches of April 10 and 12, 1929 by Friedrich Wilhelm Sander at Opel Rennbahn in Rüsselsheim, Oberth conducted in the autumn of 1929 a static firing of his first liquid-fueled rocket motor, which he named the Kegeldüse. The engine was built by Klaus Riedel in a workshop space provided by the Reich Institution of Chemical Technology, and although it lacked a cooling system, it did run briefly. He was helped in this experiment by an 18-year-old student Wernher von Braun, who would later become a giant in both German and American rocket engineering from the 1940s onward, culminating with the gigantic Saturn V rockets that made it


id: hermann-oberth-20260505-2
file: data/en.wikipedia.org/wiki/Hermann_Oberth-2.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
=== Space Mirror === In 1923, Oberth initially outlined the concept of his space mirrors in his book Die Rakete zu den Planetenräumen (The Rocket to Interplanetary Space). These mirrors, with diameters ranging from 100 to 300 km, were envisioned to be composed of a grid network consisting of individually adjustable facets. Oberth's concept of space mirrors in orbit around the Earth serves the purpose of focusing sunlight on specific regions of the planet's surface or redirecting it into space. This approach differs from creating shaded areas at the Lagrange point between the Earth and the Sun, as it does not involve diminishing solar radiation across the entire exposed surface. According to Oberth, these colossal orbital mirrors possess the potential to illuminate individual cities, safeguard against natural disasters, manipulate weather patterns and climate, and even create additional living space for billions of people. He places significant emphasis on their capacity to influence the trajectories of barometric high and low-pressure areas. However, it is important to acknowledge that the implementation of such climate engineering interventions, including space mirrors, requires further extensive research before their practical applicability can be fully realized. Further publications followed in which he took into account the technical


id: hermann-oberth-20260505-3
file: data/en.wikipedia.org/wiki/Hermann_Oberth-3.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
== Tasks in World War II == From 1923 to 1938 Oberth worked — with short breaks in 1929 and 1930 — as a high school teacher for physics and mathematics in his home region, Transylvania in Romania. The Romanian Oberth, who was professionally known worldwide and had many foreign contacts, was regarded as a security risk for the secrecy of the development work on the V-2, the world's first large rocket, in Peenemünde. Therefore, from June 1938 he was given a two-year research contract with the German Research Institute for Aviation (DVL) at the Vienna University of Technology and then from July 1940 at the University of Technology Dresden. When he wanted to return to Transylvania in May 1941, he received German citizenship and was conscripted in August 1941 under the alias "Friedrich Hann" to the Army Research Institute Peenemünde, where the V-2 rocket was developed under the direction of Wernher von Braun. Oberth was not involved in this work, but placed in the patent review, and wrote various reports, for example "About the best outline of multi-stage rockets" and about "Defense against enemy planes with large, remote-controlled solid missile". (Oberth criticized the V-2 design because, in his view,


id: hermann-oberth-20260505-4
file: data/en.wikipedia.org/wiki/Hermann_Oberth-4.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
1927: Honorary member of the German Verein für Raumschiffahrt (Space Flight Association), Berlin 1929: International Award for Astronautics (Robert Esnault-Pelterie-Hirsch-Award) of the Société astronomique de France, Paris 1946: Honorary Member of the Astronautical Section of the French Academy of Sciences, Paris 1948: Honorary President of the Gesellschaft für Weltraumforschung (Society for Space Research), Stuttgart, Germany 1949: Honorary memberships of the British Interplanetary Society, London / Dansk Selskab for Rumfartsforskening, Copenhagen / Pacific Rocket Society / Detroit Rocket Society and of Northwest German Society for Space Flight 1950: The Gesellschaft für Weltraumforschung (Society for Space Research) donates the Hermann Oberth Medal 1951: Honorary President of the Detroit Rocket Society 1952: Honorary President of the Deutsche Raketen-Gesellschaft (German Rocket Society), Bremen, Germany 1952: Honorary President of the Vereinigte Astronautische Vereinigung (United Astronautical Association), Leipzig 1953: Honorary member of the Schweizerischen Arbeitsgemeinschaft für Raumfahrt (Swiss Association for Astronautics), Lucerne 1954: Diesel Medal in gold from the Deutschen Erfinderverbandes (German Inventors' Association), Nuremberg 1954: Honorary memberships of the Austrian Society for Space Research, Vienna and of the German Association of Inventors 1955: Plaque of Honor of the American Astronautical Society 1956: Edward Pendray Award from the American Rocket Society, New York 1958: The American


id: hermann-oberth-20260505-5
file: data/en.wikipedia.org/wiki/Hermann_Oberth-5.md
category: reference
title: Hermann Oberth
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hermann_Oberth
date_saved: 2026-05-05T10:59:31.776683+00:00
instance: kb-cron
parent: hermann-oberth-20260505-0
summary:
Hermann Oberth is memorialized by the Hermann Oberth Space Travel Museum in Feucht, Germany, and by the Hermann Oberth Society. The museum brings together scientists, researchers, engineers, and astronauts from the East and the West to carry on his work in rocketry and space exploration. In 1980, Oberth was inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum. The Danish Astronautical Society has named Hermann Oberth an honorary member. In Romania, the Faculty of Engineering of Lucian Blaga University of Sibiu is named after him. In 1994, a memorial house was established in Mediaș on the 100th anniversary of his birth. It exhibits various items related to rocket technology and space travel, and also has an audio-video room for documentary films. He discovered the Oberth effect (powered flyby or Oberth maneuver), a fuel-saving strategy for interplanetary space flight that is commonly used today. There are also a crater on the Moon and asteroid 9253 Oberth named after him. In Star Trek III: The Search for Spock, the USS Grissom was classified as an Oberth-class starship. Several other Oberth-class starships also appeared in subsequent Star Trek films and television series. == Books


id: nikolai-tikhomirov-chemical-engineer-20260505-0
file: data/en.wikipedia.org/wiki/Nikolai_Tikhomirov_(chemical_engineer)-0.md
category: reference
title: Nikolai Tikhomirov (chemical engineer)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nikolai_Tikhomirov_(chemical_engineer)
date_saved: 2026-05-05T10:59:32.998036+00:00
instance: kb-cron
parent: nikolai-tikhomirov-chemical-engineer-20260505-0
summary:
Nikolai Ivanovich Tikhomirov (Russian: Николай Иванович Тихомиров; born Nikolai Viktorovich Slyotov; November 1859 – 28 April 1930) was a Russian and Soviet chemical engineer, inventor, founder of the Gas Dynamics Laboratory, specialist in rocket technology and one of the inventors of the Katyusha, which he was awarded the Hero of Socialist Labor (1991, posthumously). A crater on the far side of the Moon is named after him. == Biography == Born in November 1859 in Moscow, to a noble family of a real state councilor. His birth name was Nikolai Viktorovich Slyotov. In the 1880s, he took a pseudonym for himself, the name of his childhood friend Nikolai, the son of the merchant Ivan Tikhomirov. Subsequently, the pseudonym became his official surname. === Early years === After graduating from the lyceum, he studied at the chemical department of the Faculty of Physics and Mathematics of the Imperial Moscow University. After graduation, he worked in the technical laboratory of the Imperial Moscow University and at Kiev University in the laboratory of Professor Nikolai Bunge, who gave popular lectures on the production of "nutritional and flavoring substances". From the mid-1880s, he worked in various fields of industry, first as an assistant to


id: nikolai-tikhomirov-chemical-engineer-20260505-1
file: data/en.wikipedia.org/wiki/Nikolai_Tikhomirov_(chemical_engineer)-1.md
category: reference
title: Nikolai Tikhomirov (chemical engineer)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nikolai_Tikhomirov_(chemical_engineer)
date_saved: 2026-05-05T10:59:32.998036+00:00
instance: kb-cron
parent: nikolai-tikhomirov-chemical-engineer-20260505-0
summary:
With the assistance of the Commander-in-Chief of the Armed Forces of the Soviet Republic Sergey Kamenev, who instructed to allocate funding for Tikhomirov's workshop, on 1 March 1921, the country's first research and development organization for the development of smokeless powder shells began its work at the military department - " Laboratory for the development of inventions by N. I. Tikhomirov. In 1924, under the leadership of N.I. Tikhomirov, a recipe for smokeless pyroxylin powder was created on a non-volatile solvent - TNT, which differs from black smoke powder in powerful and stable combustion. In 1925 Tikhomirov's laboratory moved to Leningrad. On 3 March 1928, the first launch of a rocket on smokeless powder was carried out at one of the training grounds in the Leningrad region, which had a range of about 1,300 metres. This design served as the foundation for the creation of rockets for the famous Katyusha rocket launcher. In July 1928, the laboratory of N. I. Tikhomirov was renamed the Gas Dynamics Laboratory (GDL) of the Military Scientific Committee under the Revolutionary Military Council of the USSR. Under the leadership of Tikhomirov he personally prepared calculations and drawings of a 3-inch rocket projectile. Equipment for pressing


id: konstantin-tsiolkovsky-20260505-0
file: data/en.wikipedia.org/wiki/Konstantin_Tsiolkovsky-0.md
category: reference
title: Konstantin Tsiolkovsky
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
date_saved: 2026-05-05T10:59:34.323294+00:00
instance: kb-cron
parent: konstantin-tsiolkovsky-20260505-0
summary:
Konstantin Eduardovich Tsiolkovsky (; Russian: Константин Эдуардович Циолковский, IPA: [kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj] ; 17 September [O.S. 5 September] 1857 – 19 September 1935) was a Russian rocket scientist who pioneered astronautics. Along with Hermann Oberth and Robert H. Goddard, he is one of the pioneers of space flight and the founding father of modern rocketry and astronautics. His works later inspired Wernher von Braun and leading Soviet rocket engineers Sergei Korolev and Valentin Glushko, who contributed to the success of the Soviet space program. Tsiolkovsky spent most of his life in a log house on the outskirts of Kaluga, about 200 km (120 mi) southwest of Moscow. A recluse by nature, his unusual habits made him appear eccentric to his fellow townsfolk. == Early life == Tsiolkovsky was born in Izhevskoye (now in Spassky District, Ryazan Oblast), in the Russian Empire, to a middle-class family. His father, Makary Edward Erazm Ciołkowski, was a Polish forester of Roman Catholic faith who relocated to Russia. His Russian Orthodox mother Maria Ivanovna Yumasheva was of mixed Volga Tatar and Russian origin. According to family tradition, Tsiolkovsky family is of the Zaporozhian Cossack descent, related to Cossack Hetman Nalyvaiko. His father was successively a


id: konstantin-tsiolkovsky-20260505-1
file: data/en.wikipedia.org/wiki/Konstantin_Tsiolkovsky-1.md
category: reference
title: Konstantin Tsiolkovsky
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
date_saved: 2026-05-05T10:59:34.323294+00:00
instance: kb-cron
parent: konstantin-tsiolkovsky-20260505-0
summary:
Tsiolkovsky stated that he developed the theory of rocketry only as a supplement to philosophical research on the subject. He wrote more than 400 works including approximately 90 published pieces on space travel and related subjects. Among his works are designs for rockets with steering thrusters, multistage boosters, space stations, airlocks for exiting a spaceship into the vacuum of space, and closed-cycle biological systems to provide food and oxygen for space colonies. Tsiolkovsky's first scientific study dates back to 1880–1881. He wrote a paper called "Theory of Gases," in which he outlined the basis of the kinetic theory of gases, but after submitting it to the Russian Physico-Chemical Society (RPCS), he was informed that his discoveries had already been made 25 years earlier. Undaunted, he pressed ahead with his second work, "The Mechanics of the Animal Organism". It received favorable feedback, and Tsiolkovsky was made a member of the Society. Tsiolkovsky's main works after 1884 dealt with four major areas: the scientific rationale for the all-metal balloon (airship), streamlined airplanes and trains, hovercraft, and rockets for interplanetary travel. In 1892, he was transferred to a new teaching post in Kaluga where he continued to experiment. During this period, Tsiolkovsky began


id: konstantin-tsiolkovsky-20260505-2
file: data/en.wikipedia.org/wiki/Konstantin_Tsiolkovsky-2.md
category: reference
title: Konstantin Tsiolkovsky
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
date_saved: 2026-05-05T10:59:34.323294+00:00
instance: kb-cron
parent: konstantin-tsiolkovsky-20260505-0
summary:
The result of the first publication was not what Tsiolkovsky expected. No foreign scientists appreciated his research, which today is a major scientific discipline. In 1911, he published the second part of the work "Exploration of Outer Space by Means of Rocket Devices". Here Tsiolkovsky evaluated the work needed to overcome the force of gravity, determined the speed needed to propel the device into the Solar System ("escape velocity"), and examined calculation of flight time. The publication of this article made a splash in the scientific world, and Tsiolkovsky found many friends among his fellow scientists. In 1926–1929, Tsiolkovsky solved the practical problem regarding the role played by rocket fuel in getting to escape velocity and leaving the Earth. He showed that the final speed of the rocket depends on the rate of gas flowing from it and on how the weight of the fuel relates to the weight of the empty rocket. Tsiolkovsky conceived a number of ideas that have been later used in rockets. They include: gas rudders (graphite) for controlling a rocket's flight and changing the trajectory of its center of mass, the use of components of the fuel to cool the outer shell of the spacecraft


id: konstantin-tsiolkovsky-20260505-3
file: data/en.wikipedia.org/wiki/Konstantin_Tsiolkovsky-3.md
category: reference
title: Konstantin Tsiolkovsky
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Konstantin_Tsiolkovsky
date_saved: 2026-05-05T10:59:34.323294+00:00
instance: kb-cron
parent: konstantin-tsiolkovsky-20260505-0
summary:
In 1964, The Monument to the Conquerors of Space was erected to celebrate the achievements of the Soviet people in space exploration. Located in Moscow, the monument is 107 meters (350 feet) tall and covered with titanium cladding. The main part of the monument is a giant obelisk topped by a rocket and resembling in shape the exhaust plume of the rocket. A statue of Konstantin Tsiolkovsky, the precursor of astronautics, is located in front of the obelisk. The State Museum of the History of Cosmonautics in Kaluga now bears his name. His residence during the final months of his life (also in Kaluga) was converted into a memorial museum a year after his death. The town Uglegorsk in Amur Oblast was renamed Tsiolkovsky by President of Russia Vladimir Putin in 2015. The crater Tsiolkovskiy, the most prominent crater on the far side of the Moon, was named after him. Asteroid 1590 Tsiolkovskaja was named after his wife. The Soviet Union obtained naming rights by operating Luna 3, the first space device to successfully transmit images of the side of the Moon not seen from Earth. The Tsiolkovsky Memorial Apartment. A museum created in Borovsk where he lived and had


id: franz-abdon-ulinski-20260505-0
file: data/en.wikipedia.org/wiki/Franz_Abdon_Ulinski-0.md
category: reference
title: Franz Abdon Ulinski
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Franz_Abdon_Ulinski
date_saved: 2026-05-05T10:59:35.505970+00:00
instance: kb-cron
parent: franz-abdon-ulinski-20260505-0
summary:
Franz Abdon Ulinski (1890–1974) was an Austrian engineer who was known for his early proposals in spacecraft propulsion. == Biography == Born in Mladějov na Moravě, Moravia (now part of the Czech Republic), Ulinski completed his secondary education in Linz, Austria, in 1910 before joining the Austro-Hungarian Army. Ulinski served in various roles and as a technical officer in the aviation corps during World War I. In 1919, Ulinski proposed a spacecraft design powered by jets of electrons or ions. He published his ideas in a Viennese aeronautical journal in 1920, outlining two potential energy sources: solar panels for energy storage and atomic disintegration for power generation. At the time, his propulsion concepts were not widely adopted, likely due to the energy requirements needed to escape Earth's gravity. Ulinski's work is recognized for anticipating later advancements in ion propulsion technology. Ion thrusters have been utilized in spacecraft such as Deep Space One, which conducted flybys of an asteroid and approached a comet, as well as in the stabilization of satellites in Earth orbit. == References ==


id: wan-hu-20260505-0
file: data/en.wikipedia.org/wiki/Wan_Hu-0.md
category: reference
title: Wan Hu
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wan_Hu
date_saved: 2026-05-05T10:59:36.699508+00:00
instance: kb-cron
parent: wan-hu-20260505-0
summary:
Wan Hu is an alleged Chinese official described in modern sources as possibly the first man to attempt to use a rocket to launch into outer space. Possibly depicted as the "world's first astronaut" and "the first martyr in man's struggle to achieve space flight", NASA named the crater Wan-Hoo on the far side of the Moon after him. According to some Chinese sources, "Wan Hu" was a title granted to him by the imperial court during the early Ming dynasty, and his real name was Tao Chengdao. As a Ming official, he was interested in technological innovation, particularly concerning rockets. He is said to have died in 1390. While the legend is well-known, there is no direct evidence surviving to substantiate it. According to Joseph Needham, the story is dubious and may be invented during or after the Chinoiserie period, considering the lack of firm historical reference. However, Li Chengzhi has argued for the story's plausibility, saying that it may have come from oral transmission by European missionaries who came to China during the late Ming and Qing dynasties, or based on records in an ancient Chinese document that has been subsequently lost. == Legend == === Basic story


id: heinrich-albers-sch-nberg-20260505-0
file: data/en.wikipedia.org/wiki/Heinrich_Albers-Schönberg-0.md
category: reference
title: Heinrich Albers-Schönberg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heinrich_Albers-Schönberg
date_saved: 2026-05-05T10:59:38.191109+00:00
instance: kb-cron
parent: heinrich-albers-sch-nberg-20260505-0
summary:
Heinrich Ernst Albers-Schönberg (21 January 1865 – 4 June 1921) was a German gynecologist and radiologist. He was a native of Hamburg. He studied medicine at the Universities of Tübingen and Leipzig, where in 1891 he earned his medical doctorate under the guidance of Heinrich Curschmann (1846-1910). From 1892 to 1894 he was an assistant at Hamburg-Eppendorf Hospital, afterwards working as an assistant to gynecologist Paul Zweifel (1848–1927) at the University of Leipzig. Soon afterwards, he settled in Hamburg as a medical practitioner. In 1897, with internist Georg Deycke (1865–1938), he established an X-ray clinic and laboratory in Hamburg. Later, he was appointed head of the radiology department at St Georg Hospital. In 1919 he became a full professor and chair of radiology at the newly established University of Hamburg. Albers-Schönberg is credited with providing a description of osteopetrosis, a condition sometimes referred to as "Albers-Schönberg disease". It is described as a syndrome of excessive bone calcification causing a marble-like appearance with increased radiological density of the skeleton. He was an early specialist in the field of radiological medicine. In 1903 he discovered that exposure to radiation caused damage to the reproductive glands of rabbits. In cooperation with other scientists,


id: samuel-barbour-20260505-0
file: data/en.wikipedia.org/wiki/Samuel_Barbour-0.md
category: reference
title: Samuel Barbour
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Samuel_Barbour
date_saved: 2026-05-05T10:59:39.359709+00:00
instance: kb-cron
parent: samuel-barbour-20260505-0
summary:
Samuel Barbour (1860 – 3 June 1938) was an Australian chemist, photographer and X-ray pioneer in the colony of South Australia. In Australia, the medical men of the day took a slow approach in the adoption of the new science that involved X-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of X-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had any great desire to employ X-rays directly in their own medical practice. After the early investigative work of Thomas Ranken Lyle, William Henry Bragg, Joseph Patrick Slattery, and others, almost all medical men were satisfied with soliciting the services of the external X-ray man when necessity arose for skiagraphs to be produced. As the utilization of X-rays became more acceptable, the involvement of electricians


id: lucien-blake-20260505-0
file: data/en.wikipedia.org/wiki/Lucien_Blake-0.md
category: reference
title: Lucien Blake
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lucien_Blake
date_saved: 2026-05-05T10:59:40.546374+00:00
instance: kb-cron
parent: lucien-blake-20260505-0
summary:
Lucien Ira Blake (September 12, 1853 – May 11, 1916) was an American professor of physics and engineering at the University of Kansas. He pioneered studies in underwater sound transmission, the use of X-rays in medicine and electrochemistry. Blake Hall in the University of Kansas was named after him. == Life and work == Blake was born in Mansfield, Massachusetts, where his father Mortimer Blake (1813-1884) was a Congregationalist minister married to Harriet Louisa Daniels (1817-1906). After graduating from Amherst College in 1877, he went to the University of Berlin where he received a PhD with studies under Heinrich Hertz. He returned to take up a position in 1885 at the Rose Polytechnic Institute in Terre Haute, Indiana. Here he conducted experiments on underwater acoustic communication. He experimented on an underwater communication system off Sandy Hook, New Jersey. He patented several inventions and in 1887 he moved to the University of Kansas. Here he set up a four year course in electrical engineering. From 1892 he managed to set up a new physical and electrical laboratory which came to be called "Blake Hall" in 1898 (it was demolished in 1963). In 1893 he was declared one of the 40 most


id: william-henry-bragg-20260505-0
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-0.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
Sir William Henry Bragg (2 July 1862 – 12 March 1942) was a British X-ray crystallographer who uniquely shared a Nobel Prize with his son Lawrence Bragg – the 1915 Nobel Prize in Physics "for their services in the analysis of crystal structure by means of X-rays," an important step in the development of X-ray crystallography. == Early life and education == William Henry Bragg was born on 2 July 1862 in Westward, Cumberland, England, the son of Robert John Bragg, a merchant marine officer and farmer, and Mary Wood, a clergyman's daughter. His mother died when he was age 7, and was raised by his uncle (also named William Bragg) at Market Harborough. He was educated at the Grammar School there, at King William's College on the Isle of Man, and—having won an exhibition—at Trinity College, Cambridge. He graduated in 1884 as third Wrangler, and in 1885 earned First Class Honours in the mathematical Tripos. == Career and research == === University of Adelaide === In 1885, Bragg was appointed Elder Professor of Mathematics and Physics at the University of Adelaide in Australia, and started work there in early 1886. Being a skilled mathematician, at that time he had


id: william-henry-bragg-20260505-1
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-1.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
=== University of Leeds === From 1909 to 1915, Bragg was Cavendish Professor of Physics at the University of Leeds. He continued his work on X-rays with much success. He invented the X-ray spectrometer and with his son, Lawrence, then a research student at Cambridge, founded the new science of X-ray crystallography, the analysis of crystal structure using X-ray diffraction. === World War I === Both of his sons, Lawrence and Robert, were called into the army after the First World War broke out in 1914 . The following year, Bragg was appointed Quain Professor of Physics at University College London. He had to wait for almost a year to contribute to the war effort; in July 1915, he was appointed to the Board of Invention and Research set up by the Admiralty. In September, his younger son Robert died of wounds at Gallipoli. In November, he shared the Nobel Prize in Physics with Lawrence. The Navy was struggling to prevent sinkings by unseen, submerged U-boats. The scientists recommended that the best tactic was to listen for the submarines. The Navy had a hydrophone research establishment at Aberdour, Scotland, staffed with navy men. In November 1915, two young physicists were


id: william-henry-bragg-20260505-2
file: data/en.wikipedia.org/wiki/William_Henry_Bragg-2.md
category: reference
title: William Henry Bragg
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Henry_Bragg
date_saved: 2026-05-05T10:59:41.784235+00:00
instance: kb-cron
parent: william-henry-bragg-20260505-0
summary:
== Commemoration == The Electoral district of Bragg in the South Australian House of Assembly was created in 1970, and was named after both William and Lawrence Bragg. The lecture theatre of King William's College (KWC) is named in memory of Bragg; the Sixth-Form invitational literary debating society at KWC, the Bragg Society, is also named in his memory. One of the school "Houses" at Robert Smyth School, Market Harborough, Leicester, is named "Bragg" in memory of him being a student there. Since 1992, the Australian Institute of Physics has awarded the Bragg Gold Medal for excellence in physics for the best Ph.D. thesis by a student at an Australian university. The two sides of the medal contain the images of Sir William Henry and his son Sir Lawrence Bragg. The Experimental Technique Centre at Brunel University is named the Bragg Building. The Sir William Henry Bragg Building at the University of Leeds opened in 2021. In 1962, the Bragg Laboratories were constructed at the University of Adelaide to commemorate 100 years since the birth of Sir William H. Bragg. The Australian Bragg Centre for Proton Therapy and Research also in Adelaide, Australia was completed in late 2023. It is


id: frederick-woodward-branson-20260505-0
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-0.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Frederick Woodward Branson, FIC, FCS (6 March 1851 – 30 November 1933) was a British chemist, glassblower, instrument maker and X-ray pioneer. He worked with Jacob Bell & Co a chemist who reformed the profession, location Oxford Street London. He was a Fellow of the Chemical Society in 1882, and became a Fellow of the Institute of Chemistry in 1888, glassblower, instrument maker and X-ray pioneer. Chairman & managing director of Reynolds & Branson 1898 – 1933. He had many published works 1882–1918. He was given the honorary award of Freeman of the City of London 1908. == Life and times of Frederick W. Branson and his family == Frederick Woodward Branson was born on 6 March 1851 at Hanslope, Newport Pagnell, Buckinghamshire, England. He was the son of Thomas Branson a bricklayer, who later became a farmer. Branson's father inherited the farm via his marriage to Sarah Ann née Woodward, who had inherited it from her father. In 1861, Branson lived with his parents and maternal grandparents, William Woodward an agricultural labourer and farm owner, at Hungate End Farm, Hanslope. The farm consisted of 168 acres (68 ha) and employed six men and six boys. William inherited when he


id: frederick-woodward-branson-20260505-1
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-1.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
== The History of Reynolds and Branson Ltd Co 1816–1972 == The original company can be traced back to 1816 (see Grace's Guide which is the leading source of historical information on industry and manufacturing in Britain, The Company was established in 1816) Edward Matterson druggist who was running the firm at 12, Briggate, Leeds in 1822, Matterson was educated at Leeds Grammar School, the company had moved to 13 Briggate, Leeds by 1829 (1822 Baines's Directory and Gazette Edward Matterson is a druggist, and dealer in paint and colours, Location 12, Briggate, Leeds ) (Edward Matterson in Pigot's Directory of 1829 he is still druggist but now located 13 Briggate & 4 Blundel place)(also Noted Baines's Directory 1822 John Cudworth Hop Merchants was located at 13, Briggate Leeds ) (Noted William West is a druggist, located at 14, Briggate in 1822. ) Edward Matterson had been employed by Allen and Hanburys, in 1833 William West F.R.S. took over the company after Matterson went bankrupt (see The bankrupt directory: being a complete register of all the bankrupts, with their residences, trades, and dates when they appeared in the London gazette, from December 1820 to April 1843 ). In 1839 Thomas


id: frederick-woodward-branson-20260505-2
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-2.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Noted that it was a sad end to a company which had been based in Leeds, in some form or another for 156 years.


id: frederick-woodward-branson-20260505-3
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-3.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
== Reynolds and Branson chronology == 1822, Edward Matterson druggist, dealer in paint and colours, Location 12, Briggate, Leeds Baines's Directory and Gazette. 1829, Edward Matterson, druggist, located 13 Briggate & 4 Blundel place. Pigot's Directory 1833, William West F.R.S. took over the company after Matterson went bankrupt, see The bankrupt directory London gazette, from December 1820 to April 1843. 1839, Thomas Harvey, chemist and druggist, 5 Commercial Street. Leeds. 1841, Thomas Harvey, chemist and druggist, 13 Briggate. Leeds. 1854, Reynolds returned to Leeds as partner with Harvey in the chemist business and the firm became Harvey & Reynolds. 1856, Harvey & Reynolds, chemist and druggist, 13 Briggate. Leeds. 1861, Harvey, Reynolds & Fowler. Chemist and druggist, 10 Briggate. Leeds. 1864, Haw & Reynolds. Chemist and druggist. Briggate. Leeds. as Thomas Harvey had retired. 1867, Haw, Reynolds, & Co. Chemist and druggist. Briggate. Leeds. 1872, Haw, Reynolds & Co. Chemist. 14 Commercial Street, and 13 Briggate. Leeds. 1886, Reynolds & Branson. Makers of the first short clinical thermometer. 1891, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds 1901, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds 1911, Reynolds & Reynolds, chemist and druggist, 13 Briggate. Leeds == Reynolds


id: frederick-woodward-branson-20260505-4
file: data/en.wikipedia.org/wiki/Frederick_Woodward_Branson-4.md
category: reference
title: Frederick Woodward Branson
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Woodward_Branson
date_saved: 2026-05-05T10:59:42.987261+00:00
instance: kb-cron
parent: frederick-woodward-branson-20260505-0
summary:
Radium and its Properties. "The Leeds Law Institute was, on the 23rd ult., crowded to the door on the occasion of a lecture by Mr. F. W. Branson, F.I.C., on that mysterious subject known as radium. The Leeds Geological Society and the Leeds Naturalist Club were also represented, and Mr. E. Hawkesworth was in the chair. "The new metal, which Professor Pierre Curie discovered, has, as demonstrated by Mr. Branson, some wonderful properties and a probable great future. "Mr. Branson first showed that radium is an element having the highest atomic weight known, and has a characteristic spectrum, by which it can be easily identified, and that it falls into the group of metals: barium, calcium, and strontium. He then showed the difference between atmospheric (sound) waves and ether waves (heat, light, and electrical), and alluded to the emanations given off by radium as consisting of electrons negatively charged, and also much larger particles of matter termed ions positively charged. The former have very penetrative powers as regards metals and opaque bodies, and are identical with the kathode rays that are given off in an ordinary X-ray tube. "The positively charged particles are not so penetrative; indeed, they are easily


id: frank-styant-browne-20260505-0
file: data/en.wikipedia.org/wiki/Frank_Styant_Browne-0.md
category: reference
title: Frank Styant Browne
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frank_Styant_Browne
date_saved: 2026-05-05T10:59:44.201498+00:00
instance: kb-cron
parent: frank-styant-browne-20260505-0
summary:
Frank Styant Browne (10 July 1854 – 17 April 1938), also known as Styant Browne, was an Australian pharmacist, artist, photographer and X-ray pioneer from Tasmania. In Australia, the medical men of the day took a slow approach in the adoption of the new science that involved X-rays. Many of the early demonstrations were made by investigators outside the medical field. Upon examination of the initial investigators, several key factors were common. The individuals had already either been experimenting along similar lines to Wilhelm Röntgen with Crookes tubes and such, the physicists or scientists, or were actively associated with electrical work, the electricians, which made them particularly receptive to the technical appeal of the new science of X-rays. Records of the events reveal that among the medical men who witnessed the first images produced as radiographs, a rather small number had any great desire to employ X-rays directly in their own medical practice. After the early investigative work of Thomas Ranken Lyle, William Henry Bragg, Joseph Patrick Slattery, and others, almost all medical men were satisfied with soliciting the services of the external X-ray man when necessity arose for skiagraphs to be produced. As the utilization of X-rays became more


id: w-ironside-bruce-20260505-0
file: data/en.wikipedia.org/wiki/W._Ironside_Bruce-0.md
category: reference
title: W. Ironside Bruce
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/W._Ironside_Bruce
date_saved: 2026-05-05T10:59:45.380508+00:00
instance: kb-cron
parent: w-ironside-bruce-20260505-0
summary:
William Ironside Bruce (1876 – 21 March 1921) was a doctor in Europe who conducted early research on the use of X-rays. He headed the X-ray departments at Charing Cross Hospital and at the Hospital for Sick Children. He wrote an early book on X-ray techniques and he was president of the radiology section of the Royal Society of Medicine. In 1921, Bruce was diagnosed with aplastic anaemia, which his physicians attributed to his work with X-rays. He died two months after being diagnosed with the illness. Bruce's death led to the establishment of an X-ray safety committee in Great Britain. == Early life == Bruce was born in Dingwall, the second son of William Bruce, an Aberdeenshire doctor. His uncle was John Mitchell Bruce, a physician who wrote a widely read textbook, Materia Medica and Therapeutics. He was a cousin of Edmund Ironside, 1st Baron Ironside. Many members of the Bruce and Ironside families had come from Keig, a quiet village in Aberdeenshire. Though Bruce was not born there, he received his education in Aberdeen, in the tradition of these relatives. Bruce completed medical school in 1900 at the University of Aberdeen. After medical school he served in the


id: vernon-ellis-cosslett-20260505-0
file: data/en.wikipedia.org/wiki/Vernon_Ellis_Cosslett-0.md
category: reference
title: Vernon Ellis Cosslett
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vernon_Ellis_Cosslett
date_saved: 2026-05-05T10:59:46.532787+00:00
instance: kb-cron
parent: vernon-ellis-cosslett-20260505-0
summary:
Vernon Ellis Cosslett, FRS (16 June 1908 – 21 November 1990) was a British microscopist. The eighth child (of six sons and five daughters) of Edgar William Cosslett (1871–1948), a Welsh cabinet maker and carpenter, clerk of works on the estate of the Earl of Eldon at Stowell Park and latterly a builder, and Anne (née Williams; 1871–1951), he was raised at Cirencester and educated at Cirencester Grammar School, the University of Bristol, the Kaiser-Wilhelm-Institut, Berlin-Dahlem, and University College, London. He was a research fellow at the University of Bristol after completing his PhD there in 1932, having been awarded an H. H. Wills Memorial Fellowship, remaining there until 1935. He then lectured at Faraday House Engineering College, London, until 1939, whilst undertaking part-time research at Birkbeck College, London. Between 1939 and 1941 he was Keddey-Fletcher-Warr Research Fellow of London University, working at the University of Oxford as a temporary lecturer, then lecturing in physics at the University of Oxford Electrical Laboratory from 1941 to 1946. From 1947, as an ICI Research Fellow, Cosslett worked with William Lawrence Bragg at the Cavendish Laboratory, Cambridge University on the electron microscope and founded the Electron Microscopy Department. He also developed improved x-ray


id: friedrich-dessauer-20260505-0
file: data/en.wikipedia.org/wiki/Friedrich_Dessauer-0.md
category: reference
title: Friedrich Dessauer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Friedrich_Dessauer
date_saved: 2026-05-05T10:59:47.719042+00:00
instance: kb-cron
parent: friedrich-dessauer-20260505-0
summary:
Friedrich Dessauer (19 July 1881 – 16 February 1963) was a German physicist, a philosopher, a socially engaged entrepreneur and a journalist. Friedrich Dessauer was born in Aschaffenburg, Kingdom of Bavaria, German Empire. As a young man he was fascinated by new discoveries in the natural sciences. He was particularly interested in the X-rays discovered by Röntgen and their medical applications. After attending the humanistic Gymnasium in Aschaffenburg, he studied electrical engineering and physics at the Technische Universität Darmstadt and the University of Munich. Due to radiation damage during his research on the use of X-rays, his face was badly damaged and he was repeatedly treated with plastic surgery. In connection with this, he was released from military service. Due to the death of his father, he initially interrupted his studies, continued in 1914 at the Goethe University Frankfurt and then completed it in 1917. From 1924 to 1933 he was a Zentrum party member of the Reichstag, the German Parliament. A practicing Catholic with a Jewish grandparent, he was imprisoned by the Nazis when they came to power for his opposition to Hitler. He was released at request of the Turkish government, who invited him to the University of


id: tienne-destot-20260505-0
file: data/en.wikipedia.org/wiki/Étienne_Destot-0.md
category: reference
title: Étienne Destot
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Étienne_Destot
date_saved: 2026-05-05T10:59:48.908017+00:00
instance: kb-cron
parent: tienne-destot-20260505-0
summary:
Étienne Destot (1 March 1864 – 3 December 1918) was a French radiologist and anatomist who was a native of Dijon. He studied medicine in Lyon, and later worked in the hospitals of Hôtel Dieu, Croix-Rousse and Charité in Lyon. In addition to his work in medicine, he was an accomplished sculptor. Destot was a pioneer in the field of radiology. In February 1896, less than two months after Wilhelm Conrad Röntgen (1845–1923) announced his discovery of the X-ray, Destot was making radiographs of patients at the Hôtel-Dieu de Lyon. He made thousands of radiographies, many of which were of patients supplied by surgeon Louis Léopold Ollier (1830–1900). In 1913, due to severe radiation damage to his hands, he was forced to relinquish his position as radiologist. Destot also made contributions in the field of orthopedics, and in 1911 is credited as being the first physician to use the term pilon in orthopedic literature. He was a medical officer during World War I, and died from illness in Châtillon-sur-Seine in 1918. His name is included on the Monument to the X-ray and Radium Martyrs of All Nations erected in Hamburg, Germany in 1936. == Associated eponym == "Destot's space", also


id: francis-john-drake-20260505-0
file: data/en.wikipedia.org/wiki/Francis_John_Drake-0.md
category: reference
title: Francis John Drake
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Francis_John_Drake
date_saved: 2026-05-05T10:59:50.102973+00:00
instance: kb-cron
parent: francis-john-drake-20260505-0
summary:
Francis John Drake, MA MB BS (Melb) (12 December 1860 - 17 December 1929) was resident medical superintendent, Launceston Hospital. In 1860, Drake was born at St. Kilda, Melbourne. On 28 April 1879, he began work as a messenger at the Melbourne Public Library with an annual salary of £50. He attended Scotch College from 1875 to 1880. In 1886, he graduated with a BA degree, and in 1887 received the MA degree from Melbourne. In 1888, Drake completed the MB from the University of Melbourne Medical School. In 1896, the Statistics of the State of Tasmania listed Drake as holding 2 appointments. He was surgeon superintendent at Launceston General Hospital with an annual salary of £400 that included quarters, rations, and fuel. The appointment began on 1 January 1890. Concurrently, Drake held the position as medical officer at the Contagious Diseases Hospital at Launceston. In 1896, Drake and Dr. John Ramsay participated in the first demonstration of X-rays by Frank Styant Browne at Launceston Hospital. The February 1898 issue of the Australasian Medical Gazette listed the resignation of Drake from the Launceston Hospital as surgeon-superintendent. The burial of Drake, who died on 17 December 1929, took place at Box


id: william-duane-physicist-20260505-0
file: data/en.wikipedia.org/wiki/William_Duane_(physicist)-0.md
category: reference
title: William Duane (physicist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Duane_(physicist)
date_saved: 2026-05-05T10:59:51.295050+00:00
instance: kb-cron
parent: william-duane-physicist-20260505-0
summary:
William Duane (February 17, 1872 – March 7, 1935) was an American physicist who conducted research on radioactivity and X-rays and their usage in the treatment of cancer. He developed the Duane-Hunt Law and Duane's hypothesis. He worked with Pierre and Marie Curie in their University of Paris laboratory for six years and developed a method for generating quantities of radon-222 "seeds" from radium for usage in early forms of brachytherapy. He was a professor at the University of Colorado Boulder, professor-emeritus and chair of biophysics at Harvard University and research fellow of physics at the Harvard Cancer Commission. He received the John Scott Medal and the Comstock Prize in Physics in 1922 and the Leonard Prize of the American Roentgen Ray Society in 1923. == Early life and education == Duane was born in Philadelphia, Pennsylvania, to Charles William and Emma Cushman (Lincoln) Duane. He was a direct descendant of Benjamin Franklin from his father's side. He received an A.B. degree in mathematics from the University of Pennsylvania in 1892 and was valedictorian of his class. He studied at Harvard University and graduated with an A.B. in 1893. He worked as an assistant to John Trowbridge in his research


id: walter-drowley-filmer-20260505-0
file: data/en.wikipedia.org/wiki/Walter_Drowley_Filmer-0.md
category: reference
title: Walter Drowley Filmer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Walter_Drowley_Filmer
date_saved: 2026-05-05T10:59:52.518100+00:00
instance: kb-cron
parent: walter-drowley-filmer-20260505-0
summary:
Walter Drowley Filmer (1 September 1865 – 24 August 1944) was an early pioneer of X-rays in Australia, a wireless engineer, for a time ran the British Royal Train, and a world class entomologist that discovered several new species in his homeland. Filmer was a naturalist and established a private collection at his residence that thousands of people visited. == Life and Times == In 1865, Filmer was born in Maitland, New South Wales, Australia. He was the son of William Filmer (1828–1902) and Amy Filmer née Hatton (1831–1901). He married Mary Anne Eliza née Chessell (1868–1951) in 1890 in Sydney. The couple had 4 children: son, Walter Harold Alexander Filmer (1892–1964), born on 10 February 1892 in Sydney; daughter, Mary Filmer (1895–1895), born in 1895 in Petersham; son, Leroy Drowley Filmer (1902–1976), born on 5 April 1902 in Newcastle; and son, Eric Filmer (1903–1986), born 10 December 1903 in Toronto. In 1944, he died at home at Lake Macquarie. In 1876, at the age of 11, he was apprenticed to a boot maker. In 1884, by the age of 19, Filmer became an assistant telegraph line repairer and operator with the New South Wales Post Office. From 1885 to


id: elizabeth-fleischman-20260505-0
file: data/en.wikipedia.org/wiki/Elizabeth_Fleischman-0.md
category: reference
title: Elizabeth Fleischman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_Fleischman
date_saved: 2026-05-05T10:59:53.785949+00:00
instance: kb-cron
parent: elizabeth-fleischman-20260505-0
summary:
Elizabeth Fleischman-Aschheim (née Fleischman; March 5, 1867 – August 3, 1905) was an American radiographer who is considered a pioneer of X-ray technology. Fleischman was the first woman to die as a result of X-ray radiation exposure. == Early years == Elizabeth Fleischman was born in El Dorado County, California (possibly in Placerville), on March 5, 1867, the daughter of Jewish immigrants from the Austrian Empire. Her mother, Katherine Lezansky was born in Prague and had several family members who were physicians in what is now the Czech Republic. Her father, Jacob Fleischman, was a baker. Elizabeth was one of five children. By 1876, the family had moved to San Francisco, where Elizabeth's father worked first as a baker and later as a merchant who sold various sundries and cigars. Elizabeth Fleischman attended the Girls' High School and dropped out in her senior year in 1882 to help support her family. She then took courses in bookkeeping and office management, and for a time she worked as a bookkeeper at Friedlander & Mitau, a San Francisco underwear manufacturer. Upon the death of her mother, Fleischman moved in with her sister Estelle, who was married to English physician and surgeon Michael


id: elizabeth-fleischman-20260505-1
file: data/en.wikipedia.org/wiki/Elizabeth_Fleischman-1.md
category: reference
title: Elizabeth Fleischman
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elizabeth_Fleischman
date_saved: 2026-05-05T10:59:53.785949+00:00
instance: kb-cron
parent: elizabeth-fleischman-20260505-0
summary:
By 1903, the cumulative effects of seven years of unprotected X-ray exposures and twelve-hour workdays began to appear as X-ray dermatitis on her hands. She attributed this irritation to the chemicals used in developing photographic plates. In early 1904, the dermatitis progressed to the point where she sought medical attention. Her doctors found:"The fingers of both hands were found to be badly ulcerated, chiefly the tissues over the middle phalanges and the middle joints....the surfaces presenting both an ulcerated and warty condition, the warts assuming the form of necrogenica-healing alternating with ulceration. All the secreting glands and hair-follicles were destroyed so that the skin was hard and dry and cracked easily. All forms of treatment by ointments and washes were without permanent benefit."She continued to work despite this injury. In 1904, she was responsible for introducing protective measures for the operators of X-ray machines. She commented on the merits of double-plate glass screens, and metals such as lead, aluminium, iron and copper to "resist" X-rays. By late 1904, the dermatitis progressed to cancer. Her doctors attempted to excise a tumor on her right hand, but this failed to halt the progression of the carcinoma. In January 1905 her entire right


id: william-hope-fowler-20260505-0
file: data/en.wikipedia.org/wiki/William_Hope_Fowler-0.md
category: reference
title: William Hope Fowler
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/William_Hope_Fowler
date_saved: 2026-05-05T10:59:54.957712+00:00
instance: kb-cron
parent: william-hope-fowler-20260505-0
summary:
William Hope Fowler CVO FRSE FRCSE (14 March 1876 – 4 October 1933) was a Scottish medical doctor and pioneer of radiology. He was co-founder of the Edinburgh School of Radiology. == Life == He was born in Edinburgh on 14 March 1876, the son of Robert Fowler, an accountant. His early years were spent at 81 Cumberland Street in Edinburgh's New Town. He was educated at Daniel Stewart's College them studied medicine at the University of Edinburgh, graduating with an MB ChB in 1897. He went to work as resident house surgeon at the Edinburgh Royal Infirmary on Lauriston Place. He showed a keen interest in the use of electricity to treat disease and was particularly interested in the newly discovered x-ray process. In 1901 he became the infirmary's Assistant Radiologist under Dawson Turner. In 1907 they were joined by John W. L. Spence. In 1911 he was promoted to Chief Radiologist alongside Archibald McKendrick. In the same year he became Honorary Radiologist to the Admiralty. At this time Fowler was living at 21 Walker Street in Edinburgh's West End. During World War I he was a member of the War Office's X-Ray Commission. In 1933 he was elected


id: wolfram-conrad-fuchs-20260505-0
file: data/en.wikipedia.org/wiki/Wolfram_Conrad_Fuchs-0.md
category: reference
title: Wolfram Conrad Fuchs
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wolfram_Conrad_Fuchs
date_saved: 2026-05-05T10:59:56.130644+00:00
instance: kb-cron
parent: wolfram-conrad-fuchs-20260505-0
summary:
Wolfram Conrad Fuchs (1865–1908) was a German-born electrical engineer who became a pioneer in radiography. He opened the first x-ray laboratory in the United States in Chicago, and had completed over 1400 x-ray examinations by 1896. His work was critical to the history of radiation protection. He was the father of Arthur Wolfram Fuchs (1895 - 1962), the inventor of the fixed kilovoltage technique of radiography. == Early life and education == Fuchs was born in Germany in 1865 to Julius and Wilhelmina Fuchs. The family emigrated to Chicago in 1870. He returned to Germany to study electrical engineering at the University of Berlin and graduated in 1889. He then went on to Paris to study at the Ecole des Beaux Arts. Upon returning to the United States, Fuchs completed his post-graduate work at the Massachusetts Institute of Technology in Boston. == Radiography work == Shortly after Wilhelm Röntgen's discovery of x-rays, Fuchs was traveling in Germany and was interested in the potential implications x-rays could have for electrical engineering. Meanwhile, in Chicago, Dr. Friedrich Cort Hamisch was also becoming interested in x-ray technology and had established a correspondence with Röntgen. He set up an x-ray laboratory but eventually handed


id: frederick-gardiner-radiologist-20260505-0
file: data/en.wikipedia.org/wiki/Frederick_Gardiner_(radiologist)-0.md
category: reference
title: Frederick Gardiner (radiologist)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Frederick_Gardiner_(radiologist)
date_saved: 2026-05-05T10:59:57.356572+00:00
instance: kb-cron
parent: frederick-gardiner-radiologist-20260505-0
summary:
Frederick Gardiner FRSE FRCSE FRSM (1874- 8 September 1933) was a Scottish radiologist and dermatologist. == Life == Gardiner was born in Edinburgh in 1874 the son of John Gardiner and his wife Isabella. He studied medicine at the University of Edinburgh graduating MB CM in 1895. He then worked as a Resident first at Stirling Royal Infirmary, then at Dundee Royal Asylum. He returned to Edinburgh for further study, gaining a diploma in Public Health in 1901. He took on a role as Leith Hospital's radiologist in 1901. He gained his doctorate (MD) in 1902 writing his thesis on x-ray use in pulmonary tuberculosis. From 1904 he worked as Assistant Physician at the Edinburgh Royal Infirmary. In 1912 he became a senior Physician and also began lecturing in dermatology at the University of Edinburgh and in extramural classes. He did much to pioneer (in retrospect now seen as a mistake) the use of x-rays in treating of skin diseases. He also worked with Sir Robert Philip on the use of x-rays to diagnose tuberculosis. He lived close to both University and Infirmary, at 9 George Square in Edinburgh (now demolished). During the First World War he worked at Bangour


id: john-hall-edwards-20260505-0
file: data/en.wikipedia.org/wiki/John_Hall-Edwards-0.md
category: reference
title: John Hall-Edwards
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/John_Hall-Edwards
date_saved: 2026-05-05T10:59:58.586277+00:00
instance: kb-cron
parent: john-hall-edwards-20260505-0
summary:
John Francis Hall-Edwards FRSE (19 December 1858 – 15 August 1926) was a British medical doctor and pioneer in the medical use of X-rays in the United Kingdom. == Life == Hall-Edwards was the son of John Edwards, and was born on Moseley Road, Kings Norton near Birmingham. He attended King Edward VI Grammar School in Birmingham. He then studied medicine, apprenticing under Prof Richard Hill Norris at Queens College Medical School. Norris was both a surgeon and keen amateur photographer, being an early user of the dry-plate process, and he familiarised Hall-Edwards with photographic techniques. Hall-Edwards was licensed to practice medicine by the Royal College of Physicians of Edinburgh. From around 1885 he shows a strong interest in photography and was President of the Midland Photographic Club 1891–93. In 1895 he was made an Honorary Member of the Royal Photographic Society following a lecture to the London Camera Club. Initially his work focussed on photography through microscopes. On 11 January 1896 he made the first use of X-rays under clinical conditions when he radiographed the hand of an associate, revealing a sterilised needle beneath the surface. A month later on 14 February he took the first radiograph to direct


