Sitting on the sofa at home with some cold-like illness I'm fascinated by the moiré patterns through the insect screen on the windows.
About 7-8m away is some wood. About 3-4m away is a screen. The wood grain is too fine to perceive. The mesh in the screen is also too fine to perceive. But through the magic of aliasing I can see a low frequency version of the wood grain through the screen.
It's a form of heterodyning that makes a high frequency signal (wood grain) perceptible by multiplying by a local oscillator (screen) and filtering (my eyesight).
