Look at all of these scientific optical illusions you can do with dot patterns

Here's a fun scientific experiment you can replicate easily. Using printed dot patterns on white paper and a photocopy of that same pattern on transparency, Tadashi Tokieda explains how simply rotating and moving the transparency layer can create lovely (and sometimes nauseating) moire patterns. It's an illusion and practical effect that I've seen used in books before, but having it explained in detail is neat.