>If you can physically set up those boundary conditions, the atmosphere will in fact perform the computation. The invalidity of the equivalence principle becom

>If you can physically set up those boundary conditions, the atmosphere will in fact perform the computation. The invalidity of the equivalence principle becomes much more ambiguous for me in that case. >The atmosphere is not solving the Navier-Stokes equation; the atmosphere is doing what the Navier-Stokes equation models It can sometimes be hard to distinguish the two. Analogously, you can compute a Fourier transform optically—as a simple example, the diffraction pattern of an aperture is the Fourier transform of the aperture shape (as if it were a 2D step function) [*]. Is the aperture performing the Fourier transform, or merely doing what the Fourier transform models? In the days before fast DSPs, this is exactly how Fourier transforms were computed. [*] As a more complex example, by passing collimated light through a transparency and then a lens, the image formed is the Fourier transform of the signal encoded by the transparency.