Explains Physics on Instagram: "This clip is a clear example of the moiré effect, an interference pattern that appears when two repeating patterns overlap with slightly different spacing or timing. The result is a larger, slower-moving pattern that does not actually exist in either pattern on its own. Here, the ruler’s edge and its fine surface details form a fast, repeating pattern as it vibrates. In shadow, the light is more directional and high-contrast, so tiny movements along the ruler crea