What happened ?

You probably saw the clouds moving and boiling for a few seconds. You can also do this with any still picture. Just look at the picture, start the spin machine and when it finishes look back at your picture.
Please note: the vast majority of people will see this dramatic effect. However, there are some that may not see what others do. It is important to stare at the center of the spinning spirals and to hold your head still.

How does it work?

First, we need to understand a little bit about how we see things. Light enters our eyes through the cornea and lens. The light is focused onto the retina and then this information is transferred to the optic nerve and on to our brain. As amazing as our eyes are, it is our brain that allows us to take this information and sort it out into something meaningful.

After staring at the spinning spirals our brain tries to take the visual information and make some sense out of it by compensating for the constant movement. But then, when we suddenly look at a still image, our brains are still trying to apply the readjustment to the new picture and it looks a little funny for a few seconds, until our brains adjust back.