The effect is well understood. It is temperature dependent, as well as dependent on the mass of the individual molecules in the air. Essentially, there is a balancing act between the force of gravity and the dispersion based on temperature. The average energy of an individual molecule in the air is directly related to the temperature. But it is also related to the mass of the molecule and the average velocity. For ordinary gasses at standard temperatures, the pressure difference is small unless you consider large differences in height. There are also differences due to the masses, so there is a different characteristic height for oxygen, nitrogen, and carbon dioxide.<quoted text>
I just told you why. But feel free to com eup with new sub-theories to patch your theory.
Here is something for you and Polymath to consider.
Take a cylinder of oxygen or any other gas. Evacuate it to a partial vacuum. In this gravity well the remaining gas should collect at the bottom. You should have a pressure differential on the insides of the container between the top and bottom. Gravity on the nuclei. Pure and simple. I haven't researched this, but I suspect the gas will diffuse to an even pressure outwards in all directions. There may be a very tiny differential due to that gravity which will be affected by the Casimir effect, which would reduce that gravitational pull on the individual gas atoms, an internal to the cylinder condition and effect. However, this will not effect the total weight or mass of the cylinder barring any influence of that vacuum being transferred through the cylinder material. I believe what you will find is it is the EM repulsion that scatters the gas atoms. There is really nothing else to do such. Those atoms are spinning. That comes under the heading of motion. Balance of charge created by displacement of space. If you can polarize the spin from without you may see differences of internal pressure on the internal walls. And do not forget these relative pressure, or force may be a better word, differences are also affecting the internal structure of the cylinders themselves. Space goes everywhere.
That all goes under the heading of the conservation of mass and energy. No virtual particles needed.
This is NOT an EM effect. It is a statistical mechanics effect.