Definition
A physical constant, sometimes called a fundamental physical constant or universal constant, is a physical quantity that cannot be explained by a theory and therefore must be measured experimentally. It is distinct from a mathematical constant, which has a fixed numerical value, but does not directly involve any physical measurement.
Related concepts
2019 revision of the SIAge of the universeAmpereAnthropic principleArnold SommerfeldAtomic physicsAtomic unitsAvogadro constantBoltzmann constantCabibbo–Kobayashi–Maskawa matrixCandelaCharacteristic lengthCharacteristic number (physics)Characteristic timeClassical electromagnetismCoefficientDimensional analysisDimensionlessDimensionless physical constantElectric constantElectrical resistivity and conductivityElectromagnetic interactionElectromagnetismElectronElectron rest massElementary chargeElementary particlesEmpirical constantFine-structure constantFine-tuned universeGauge groupGeneral relativityGravitational constantHeat capacityHiggs fieldHyperfine structureIntelligent designInternational System of UnitsInternational prototype of the kilogramIt from bitJohn D. BarrowJosephson constantKelvinKilogramLeast significant digitLengthLeptonLightList of common physics notationsList of mathematical constantsList of physical constantsLuminous efficacyMadelung constantMany-worlds interpretationMaterial constantMathematical constantMaxwell's equationsMeasurementMethanolMetreMichael Duff (physicist)Mole (unit)MultiverseNational Institute of Standards and TechnologyNatural unitsNeutrino massNew physicsParameterPaul DiracPhysical quantityPhysical theoryPhysics beyond the Standard ModelPlanck constantPlanck unitsPontecorvo–Maki–Nakagawa–Sakata matrixProton-to-electron mass ratioQCD vacuumQuantum gravityQuantum mechanicsQuarkRatioReduced Planck constantRest massRydberg constantSI base unitSI base unitsSI unitSI unitsScience (journal)SecondSpace.comSpecial relativitySpeed of lightStandard ModelStandard Model (mathematical formulation)Standard uncertaintyTimeTime-variation of fundamental constantsTruismType Ia supernovaeVacuum permeabilityVacuum permittivityVariable speed of lightVon Klitzing constantWeinberg angleYukawa couplings
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