Under the condition of constant temperature, the gas is influenced by the gravitational field of the planet, which leads to uneven distribution. Considering the spatial height of gas distribution on the earth

ρ=ρ0×exp(-mgh/kT)

ρ0 is the gas density on the surface; K Boltzmann constant; T is the thermodynamic temperature of the planet.

P=P0×exp(-mgh/kT)

P0 is the gas pressure on the ground;

The so-called "elevation" actually refers to the place where the density and pressure drop to the surface value 1/e;

Mgh/kT= 1, namely h=kT/mg.