What is needed
* You, a friend, and the animations provided.
What to Do: Head Shrinker
* Click below to turn on the animation.
* When the animation starts, put your face about one foot from
your screen, and stare hard at the center of the animation. Don't
blink, and don't move your eyes!
* Stare for one minute, without blinking. It hurts, but do it!
* Now, stare at your friend's head. (Or, stare at something else
in the room. A clock is nice, a piece of paper with writing on
it is too.)
* What do you observe?
What to Do: Head
Expander
The same thing, but backwards!
* Click below to turn on the animation.
* When the animation starts, put your face about one foot from
your screen, and stare hard at the center of the animation. Don't
blink, and don't move your eyes!
* Stare for one minute, without blinking. It hurts, but do it!
* Now, stare at your friend's head. (Or, stare at something else
in the room. A clock is nice, a piece of paper with writing on
it is too.)
* What do you observe?
What is Happening
This is an example of what is known as the "waterfall effect." If you stare at something brightly colored for a long time, you will see an afterimage of the color - in a complementary (opposite) color. This animation shows a similar effect: after watching it for a while, you see an afterimage of the motion - and the afterimage is the opposite of the motion you stared at. If the circles were expanding, the afterimage causes things to look like they are shrinking. If the circles were shrinking, the afterimage causes things to look like they are expanding!
Of course, you can do this with a waterfall - which is where the name for the effect came from! If you stare at a waterfall for a long time and then look at something else, it will appear to rise!
Other Things to Try
As the animations play, motion and color illusions start to occur. I see distinct colors appear - and they are different on the top and the bottom of the animations. These are afterimages of the light and dark areas, and produce an illusion of color as different color sensors in your eyes respond at different rates.
I think how well you see this one might be age-related. I have found a bunch of different optical effects and optical illusions that work well for young people or old people but not both, and I suspect this is one.
