[meow_catrix]

Planes do ”flap their wings”, just not the ones protruding from the fuselage.

[trhway]

I think you're mistaking rotating for flapping. Rotation is one of those fundamental things differentiating our technological civilization from Nature.

[meow_catrix]

Those rotating things still produce their thrust by pushing a wing-shaped structure through air, producing a high-pressure zone on one side, and a low-pressure zone on another. That is what I was getting at. It is the same principle.

[andsoitis]

> Rotation is one of those fundamental things differentiating our technological civilization from Nature.

Rotation is very common in nature.

Planetary rotation, inner-core rotation, spinning galaxies, dung beetle rolling, Keratinocyte migration, Rotifers, spirals, rotational symmetry, etc.

What isn’t common (but not non-existent) is using rotation for locomotion in biology.

[eesmith]

Bacterial flagellum rotate. See also https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_... .