posted by AAA .
The mass of 1 cubic meter of air at sea level is about 1.3kg. Hoe much does it weight in newtons? How much would a stack of 8000 such cubes weigh? If this total weight were all applied to an area of 1m^2, how much pressure would it produce on that surface? The answer should look familiar. (Although the atmosphere actually gets less dense with increasing altitude, the total amount of air is the same as these sea-level cubes were stacked some 8km high.)