In the 1940’s, the great illustrator Eric Sloane took look at the first three miles that surrounds our planet, the “troposphere,” the slice of sky that contains weather:
When most of us look up, we don’t think of the thinning blue sheet of gases that taper off into space, we think of storms and clouds and rain and tornados and lightning; the stuff that makes looking up interesting. For us, sky equals weather.
And instead of asking “How High Is the Sky?” he flipped it to ask “How High is the Weather?”
We live in a compact neighborhood. Everything we see above us, the vast stretches of clouds, no matter how high they look, are not that far away — no further than the horizon. Ours is a geometrically small world, says Eric.
Sloane wrote that about half of all the air (the gas molecules we breathe) and 90 percent of the moisture is crammed into the first 18,000 feet of sky. That’s the lowest layer of the first layer of sky, so the habitable zone of air is extraordinarily narrow.