# Physics The 11 definitions of the physics library, each with its Epsil spelling, its MathJSON name, its signature and its full description. Each definition is listed under its Epsil spelling (the MathJSON name when it has none), with its signature in the engine's type syntax. The [Standard Library](/library/) page is the one-page index of every category. ## Definitions ### avogadroConstant MathJSON `AvogadroConstant` · constant `value` = `6.02214076e+23 mol^-1` Avogadro constant ### boltzmannConstant MathJSON `BoltzmannConstant` · constant `value` = `1.380649e-23 J/K` Boltzmann constant ### elementaryCharge MathJSON `ElementaryCharge` · constant `value` = `1.602176634e-19 C` Elementary electric charge ### gasConstant MathJSON `GasConstant` · constant `value` = `8.314462618 J/mol⋅K` Molar gas constant ### gravitationalConstant MathJSON `GravitationalConstant` · constant `value` = `6.6743e-11 m^3/kg⋅s^2` Newtonian constant of gravitation ### mu0 MathJSON `Mu0` · constant `value` = `0.00000125663706212 N/A^2` Vacuum permeability ### planckConstant MathJSON `PlanckConstant` · constant `value` = `6.62607015e-34 J⋅s` Planck constant ### speedOfLight MathJSON `SpeedOfLight` · constant `value` = `299792458 m/s` Speed of light in vacuum ### standardGravity MathJSON `StandardGravity` · constant `value` = `9.80665 m/s^2` Standard acceleration due to gravity ### stefanBoltzmannConstant MathJSON `StefanBoltzmannConstant` · constant `value` = `5.670374419e-8 W/m^2⋅K^4` Stefan-Boltzmann constant ### vacuumPermittivity MathJSON `VacuumPermittivity` · constant `value` = `8.8541878128e-12 F/m` Vacuum permittivity (electric constant)