Would it be the same in a hypothetical completely homogeneous gas?
My assumption is that turbulent changes in pressure cause diffraction, causing the light to not take a perfectly straight path. I don’t know enough about physics to know if that’s right.
The speed of light in a medium is the inverse of the refractive index of that medium. It's caused by the interaction between the electrons in matter (bound to atoms) and electromagnetic fields. It does not require inhomogenities larger than the atomic structure.
Materials seem to have different refractive indices for some sort of complicated quantum reason that only relies on the inhomogenity because of materials being made up of atoms containing electrons, not an sort of macroscopic inhomogenity.
My assumption is that turbulent changes in pressure cause diffraction, causing the light to not take a perfectly straight path. I don’t know enough about physics to know if that’s right.