Editing Hydrostatics (section)

===Atmospheric pressure===
[[Statistical mechanics]] shows that, for a pure [[ideal gas]] of constant temperature in a gravitational field, ''T'', its pressure, ''p'' will vary with height, ''h'', as

:<math>p (h)=p (0) e^{-\frac{Mgh}{kT}}</math>

where
* {{mvar|g}} is the [[standard gravity|acceleration due to gravity]]
* {{mvar|T}} is the  [[absolute temperature]]
* {{mvar|k}} is [[Boltzmann constant]]
* {{mvar|M}} is the [[molecular mass]] of the gas
* {{mvar|p}} is the pressure
* {{mvar|h}} is the height

This is known as the [[barometric formula]], and may be derived from assuming the pressure is [[Hydrostatic pressure|hydrostatic]].

If there are multiple types of molecules in the gas, the [[partial pressure]] of each type will be given by this equation. Under most conditions, the distribution of each species of gas is independent of the other species.