On Aug 6, 9:37 pm, Tina wrote:
the variable that matters is that there's 14.7 pounds of air over
every square inch at sea level. If that's the one that stays constant,
the answer is clear.


Well...not to quibble, but 14.7 (ok, 14.694) psi is the MEAN sea level
pressure. There are localized variations in pressure caused by
density differences over those areas. (which is why GENERALLY
speaking, areas of lower pressure indicate "rain" systems; the lighter
air indicates a higher moisture content).

Although, in large enough volumes the differences are close enough to
zero that they do not significantly affect calculations since

lim (m/V) = 0
V-inf