Two optical illusions

[Ivan Seeking]

Black Dots
http://www.cse.unsw.edu.au/~geoffo/humour/opticals/black-dots.jpg


Spinning Wheels
http://www.cse.unsw.edu.au/~geoffo/humour/opticals/spinning-wheels.jpg

[recon]

Forgive my ignorance, but how do the optical illusions above work?

[hypnagogue]

Whoa! I've seen the black dots before, but the spinning wheels are pretty trippy... [8)]

[zoobyshoe]

Originally posted by recon
Forgive my ignorance, but how do the optical illusions above work?
Check out these sites for more illusions and explanations:

Optical Illusions: Editor Selected ResultsAbout Optical Illusions
Address:http://results.about.com/optical_illusions/