Moiré patterns from random dots: https://observablehq.com/@otaviocv/moire-patterns-from-random-dots
Overlaying the same random dot pattern on a translated and rotated copy of itself shows concentric dots around the center of rotation, illustrating Chasles' theorem that every rigid transformation of the plane is a translation or rotation. (For 3d version see https://en.wikipedia.org/wiki/Chasles%27_theorem_(kinematics))
The effect seems to have first been observed by Leon Glass ("Moiré patterns from random dots", Nature, 1969, https://doi.org/10.1038/223578a0)
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!