I need to mention that, compressibility effects do not begin until around 250-mph. Until then, air is considered an incompressible fluid, the reason why aerodynamics is just a branch of fluid mechanics.
The 'ground' is the 'ocean floor' of the troposphere. Our cars are fully-submerged structures, completely surrounded by 'fluid.'
When we move, we 'displace' air, but we don't compress it.
