Wandering wheel

HOW

1. Carefully look at the pattern on the stationary disc.
2. Start rotating it.
3. Slowly increase the spinning speed.
4. What can you see? Experiment by rotating the disc at different angular speeds, in both directions.

WHY

Slowly rotating the disc creates the illusion that the wheel is moving around its circumference. With a quick spin, the black and white details merge into grey. The eye cannot keep up with the excessively fast colour changes, so that individual images overlap. Near the centre of the disc, the linear speed of the points is lowest. Therefore, details of black lines on a white background can be distinguished in these areas.