# Physical Constants

Constants commonly used in Physics numericals and computational Physics.

### Physics and Astronomical Constants

$$c = \text{Speed of light in vacuum} = 2.99 \times 10^8 ms^{-1}$$

$$e = \text{Elementary charge} = 1.602 \times 10^{-19} C$$

$$m_n = \text{Neutron rest mass} = 1.675 \times 10^{-27} kg$$

$$m_e = \text{Electron rest mass} = 9.112 \times 10^{-31} kg$$

$$h = \text{Planck’s constant} = 6.626 \times 10^{-34} Js$$

$$\overline { h } = \text{Dirac’s constant} = \frac{h}{2π}) = 1.055 \times 10^{−34} Js$$

$$k = \text{Boltzmann’s constant} = 1.1.381 \times 10^{-23} JK^{-1}$$

$$G = \text{Gravitational constant} = 6.673 \times 10^{-11} N m^2 kg^{−2}$$

$$\rho = \text{Stefan-Boltzmann constant} = 5.670 \times 10^{-8} J m^{−2} K^{−4} s^{−1}$$

$$c_1 = \text{First Radiation Constant} = 2πhc^2 = 3.742 \times 10^{-16} J m^2 s^{−1}$$

$$c_2 = \text{Second Radiation Constant} = \frac{hc}{k} = 3.742 \times 10^{-16} J m^2 s{−1}$$

$$\epsilon_0 = \text{Permittivity of free space} = 8.854 \times 10^{-12} C^2 N^{−1} m^{−2}$$

$$\mu_0 = \text{Permeability of free space} = 4\pi \times 10^{-8} hm^{-1}$$

$$N_A = \text{Avogadro constant} = 6.022 \times 10^{23} mol^{-1}$$

$$R = \text{Gas constant} = 8.314 J K^{−1} mol^{−1}$$

$$a_0 = \text{Bohr radius} = 5.292 \times 10^{-11} m$$

$$\mu_B = \text{Bohr magneton} = 9.274 \times 10^{-24} JT^{-1}$$

$$α = \text{Fine structure constant} = 7.297 \times 10^{-3}$$

$$M_\bigodot = \text{Solar Mass} = 1.989 \times 10^{30} kg$$

$$R_\bigodot = \text{Solar radius} = 6.96 \times 10^{8} m$$

$$L_\bigodot = \text{Solar luminosity} = 3.827 \times 10^{26} J s^{−1}$$

$$M_\oplus = \text{Earth Mass} = 5.976 \times 10^{24} kg$$

$$R_\oplus = \text{Mean earth radius} = 6.371 \times 10^{6}m$$

$$\text{1 light year} = 9.461 \times 10^{15} m$$

$$1 AU = \text{Astronomical Unit} = 1.496 \times 10^{11} m$$

$$1 Pc = \text{Parsec} = 3.086 \times 10^{16} m$$

$$\text{1 Year} = 3.156 \times 10^{7} s$$

$$\text{1 Year} = 1 J = 6.2415 \times 10^{18} eV$$