Ever since humans descended from the trees and out onto the savannah, we’ve gazed upward in wonder at the sky and the stars. Until fairly recently in our history, this space above our heads was a mystery. Our ancestors would witness the diurnal movements of the Sun and the Moon, and the brilliance of a glowing sunrise or sunset. The clouds would drop water and thundering bolts of light and energy. At night, they would witness a spectacular tapestry of light-emitting dots, and connect them into elaborate shapes. The sky has been a continual source of wonder throughout our history, and we’ve spent countless hours thinking about the world we see above our heads.

There’s a need among humans to occupy and build on the highest places around. These places act like magnets for anyone living around them. There are many reasons for this, but they all boil down to verticality. Occupying or building on a high place means you’ve done battle with gravity, and you’ve won.

The above illustration originally appeared in the 1962 book The Earth from the Life Nature Library. It does a masterful job of explaining the complex layers of the earth’s atmosphere, and it puts the scale of each layer in perspective.