The image above is a link to a new illusion on Prof. Michael Bach's website, the so-called Roget Picket Fence. Read this first: what you will see on Prof. Bach's page is a spinning wagon wheel with some controls. One control places a brown picket fence in front of the rotating wheel. Through the spaces between the pickets, you will have no trouble verifying that an undistorted wheel is still turning. However, another control allows you to slide the picket fence continuously to the left. When this happens, you will see that the spokes of the wheel become distorted. However, the distortion that appears is rather unexpected. If I had been asked to predict the result before trying it, but not given much time to think before replying, I would probably have replied that the spokes would take on a spiral appearance. Not at all! Clearly, with the wheel turning and the picket fence also moving, we see each spoke at a different position in its rotation through a given slot, as the fence slides. But do you clearly understand the unusual distortion actually seen? And, another thing: the wheel also now appears to be fixed, nonrotating!  Try it!