### 44.1 Fundamental Constants

`GSL_CONST_MKSA_SPEED_OF_LIGHT`

  The speed of light in vacuum, c.

`GSL_CONST_MKSA_VACUUM_PERMEABILITY`

  The permeability of free space, \mu_0. This constant is defined in the MKSA system only.

`GSL_CONST_MKSA_VACUUM_PERMITTIVITY`

  The permittivity of free space, \epsilon_0. This constant is defined in the MKSA system only.

`GSL_CONST_MKSA_PLANCKS_CONSTANT_H`

  Planck’s constant, h.

`GSL_CONST_MKSA_PLANCKS_CONSTANT_HBAR`

  Planck’s constant divided by 2\pi, \hbar.

`GSL_CONST_NUM_AVOGADRO`

  Avogadro’s number, N_a.

`GSL_CONST_MKSA_FARADAY`

  The molar charge of 1 Faraday.

`GSL_CONST_MKSA_BOLTZMANN`

  The Boltzmann constant, k.

`GSL_CONST_MKSA_MOLAR_GAS`

  The molar gas constant, R_0.

`GSL_CONST_MKSA_STANDARD_GAS_VOLUME`

  The standard gas volume, V_0.

`GSL_CONST_MKSA_STEFAN_BOLTZMANN_CONSTANT`

  The Stefan-Boltzmann radiation constant, \sigma.

`GSL_CONST_MKSA_GAUSS`

  The magnetic field of 1 Gauss.