One-point-two kilograms per cubic meter. Why is this number significant? It’s the approximate average density, or mass per volume, of the air at sea level.
As you might expect, this mass pales in comparison to that of water, which is roughly 800 times denser than the atmosphere above it. Despite this, air has enough heft to ensure that high-speed hurricane winds can lift whole houses clean off the ground. And when pushed through a jet engine, it can hold a 640-ton airplane aloft — no mean feat for such a lightweight fluid.
Earth’s atmospheric density has fluctuated significantly over the course of its history. In fact, Earth had more in common with Venus, a thick, toxic hothouse world, billions of years ago, according to a study published in Science Advances in 2020. The surface of our blue planet was a molten magma ocean at the time, and its pre-life atmosphere ...
