In 1644, Evangelista Toricelli wrote, “We live submerged at the bottom of an ocean of air.” We don’t feel the force of the pressure of this fluid any more than aquatic creatures feel the force of the water on all sides. Why? Because there is a uniformity of pressure in both cases; gravity exerts pressure on all sides.
Imagine for a moment that everything on the Earth and above its surface could exist under the water, or vice versa, without any change in appearance or properties. If we visualize horizontal bands atop one another, it would break the habitable area into observable layers. Grass, trees, plants, insects, ground-dwelling animals would all be in the same layer as the plants, crabs, bottom-feeders, and sand dwelling creatures beneath the surface of the ocean. There would be fish swimming in the layer above our heads with the birds. Airplanes would soar further above, in a layer with the whales. Dolphins would escape the surface of the ocean, accompanied by rockets, at the topmost layer above Earth. It would be a jumbled and magnificent scene.
The larger point is that aerodynamics and hydrodynamics are both parts of fluid dynamics. Fluid dynamics explains the behavior of fluids, think air and water, in motion. As a result, the principles of lift, drag, gravity, and thrust would play out for the creatures and objects that fell into each band above the bottom of the ocean or surface of the Earth. That’s the part that fascinates me. Face it, for a whale to stay afloat is no mean feat. Then again, neither is it to keep a jumbo jet full of people in the air.
It’s not quite a 1:1 in every instance above and below the surface of the ocean, but it is close enough that it excites the imagination.