Another interesting perspective: Earth's atmosphere is about five miles thick. Yes, it trails off exponentially and airplanes can fly and people can breathe (sort of) at 30,000 feet. However, were it uniformly as dense as it is at sea level (i.e. the atmosphere most of us are familiar with), it would fit in about five miles.
That's indeed an interesting perspective; I just double-checked in sane units:
Standard pressure 101 325 N/m^2 divided by standard gravity 9.80665 N/kg gives the mass of the air per area: 10 329 kg/m^2.
Divide that by an air density of 1.225 kg/m^3 to get a height of 8435 meters[1]. The Mount Everest is 8848 meters high. If the atmosphere were uniformly dense, the highest mountains would rise above it.
([1] Not in fact accurate to four digits because the constants I used aren't really constant across that height range.)
Thanks, codeflo. I calculated similar numbers and only gave a very crude approximation but I will take your word for it. Obviously, with the thermal distribution according to altitude it's a poorly defined problem.
Most intuitively, this means that when looking at some object on earth ~5 miles away, you are looking through roughly as much air as you are when looking at any given planet or star above you in the sky.
