Pressure - example
If we assume that the air has a constant density (it doesn’t) equal to the density it has at sea level (?air = 1.2 kg/m3), how high would the atmosphere extend?
The atmosphere, because it is compressible, actually decreases in density with height, so it extends higher than this example would indicate, and it gradually thins out rather than having an abrupt end (as the essentially incompressible water does). But this will give us a rough estimate of how thick our atmosphere is.