text: """ Physical/chemical constants """
  
  #: Acceleration due to gravity, m/s2
  G = 9.80665
  
  #: Radius of the Earth, km
  # "Equal area" radius. Gives correct total surface area when modeled as a sphere
  R_EARTH = 6371.0072
  
  #: Avogadro's number, molec/mol
  AVOGADRO = 6.022140857e+23
  
  #: Universal gas contant, J/mol/K
  R_GAS_UNIV = 8.314
  
  #: Boltzmann's constant, J/K
  K_BOLTZMANN = 1.381e-23
  
  # Typical molar mass of air, kg/mol
  MW_AIR = 28.97e-3
  
  # Molar mass of water, kg/mol
  MW_H2O = 18.016e-3
  