This is a visual illusion. When you look at it, there appears to be a great deal of motion as things rotate in various directions. But there's no actual motion; this isn't an animated display and you can verify this by fixating the centre or touching your computer screen - no motion. I just fooled your visual system.
But Andrew, you say, you've been talking all this time about how great perception is! It's direct, functional, reflects experience, and lawful: if perception is all these things, how can it be fooled so easily by some pixels? Direct realism surely cannot handle this: perception is flawed, and readily shown not to correspond to the way things really are. Clearly this James Gibson is a mad man and we can go back to 'knowing' that perception is clearly mediated by pretty good but fallible representations.