# Physical constants and unit conversions (fatiando.constants)¶

Holds all physical constants and unit conversions used in fatiando.

All modules should import the constants from here!

All constants should be in SI, unless otherwise stated!

fatiando.constants.CM = 1e-07

Proportionality constant used in the magnetic method in henry/m (SI)

fatiando.constants.G = 6.673e-11

The gravitational constant in $$m^3 kg^{-1} s^{-1}$$

fatiando.constants.MEAN_EARTH_RADIUS = 6378137.0

The mean earth radius in meters

fatiando.constants.PERM_FREE_SPACE = 1.2566370614359173e-06

Permeability of free space in $$N A^{-2}$$

fatiando.constants.SI2EOTVOS = 1000000000.0

Conversion factor from SI units to Eotvos: $$1/s^2 = 10^9\ Eotvos$$

fatiando.constants.SI2MGAL = 100000.0

Conversion factor from SI units to mGal: $$1\ m/s^2 = 10^5\ mGal$$

fatiando.constants.T2NT = 1000000000.0

Conversion factor from tesla to nanotesla

fatiando.constants.THERMAL_DIFFUSIVITY = 1e-06

The default thermal diffusivity in $$m^2/s$$

fatiando.constants.THERMAL_DIFFUSIVITY_YEAR = 31.5576

The default thermal diffusivity but in $$m^2/year$$