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It's amazing what some physical processes can do. During the years I worked with laser physicists, I learned that passive optical systems can do crazy things, such as Fourier transforms.

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Hmm... I suppose it can come across as pedantic, but physical processes as a whole can do anything that can be done, hence it shouldn't come as a surprise that there exists a physical process that can perform a Fourier transform, or any computable process whatsoever.

I agree. To me it's more interesting that there exists a physical process that performs a Fourier transform than that there could exist such a process. If it can be done on pen and paper, it's already proven that it can be done in a physical system, since the pen and paper are physical.

This is done by prisms breaking sunlight into a rainbow, or Newton's Rings of color appearing on oil slicks. Peacocks and bluejays and blue morphos all get their color from notch filters applied to the Fourier transform.

It's a pretty common effect, and frankly trivial. Lensless holographic focusing lenses on sea star exoskeletons are a bit less surprising... but only because they actually evolved, not because it could happen.

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