 all else being equal the terminal velocity is inversely proportional to the square root of air density air density drops off pretty quickly and i really should be doing something other than digging up the math for that i think it involves calculus to integrate the amount of mass as the column of the atmosphere trails off chemistry types have a method for dealing with this question without dragging in the calculus suppose an atmosphere to be mainly affected by gravity resulting in the potential energy for a mass m to be linear in height h mgh what relative concentrations will we have when two different packets of air are in equilibrium if they are at the same height we will have half the mass in one and half the mass in the other and the amount flowing from one to the other balances the amount flowing in the opposite direction NUMBER if they are at differing heights then a greater percentage of the higher air tends to descend than that percentage of the lower air which ascends in order for the two flows to balance the higher packet must contain less air than the lower and the mass balance of the flows corresponds thusly high percentage of thin air low percentage of dense air now rates are exponential in energy differences NUMBER so that theoretically we should expect an exponential decay in height to compensate how does it go in practice dave NUMBER how well does it balance chemical equilibria seem stable as they deal with very large numbers over a very long time economic equilibria are viewed from the mayfly standpoint of individual people and so at best the shot noise is very visible NUMBER that is to say rates will be exponential in the free energy differences between endpoints and a transition state we can ignore that complication in this model 