Why does a car wheel look like it's going backwards when at speed?

Why does a car wheel look like like it's going backwards when at speed? I'm not sure if another person has answered this, and they probably have. But still, I shall still share my theory with you.

Have you ever been driving down the freeway and you looked at an other car's wheel and it looked like it was going backwards? Well I have. And I have been thinking about it and now I think I know.

I expect that the car's wheel is traveling faster then we can process. I think instead of making us really really dizzy, I think we have found one group of scratches or marks looked for them again and again and again. Now whilst we're are looking for those marks the wheel is rotating. So when we find the marks the have done a rotation, but we are seeing it just before it passes the last spot we saw it. If that keeps on happening the marks will go further and further backwards.

 So that is why I think when we see a wheel going at speed, we think it is actually moving backwards.

Thank you and good bye. :)