Have you ever looked at your shadow on the ground and noticed a bright spot around the shadow of your head? It’s not an illusion and it certainly doesn’t involve anything supernatural. It’s called the opposition effect. Evil Mad Scientist Laboratories had a nice article on it recently.
The basic idea is that when you look at a rough surface you can see it casting shadows on itself. But in the area opposite the sun, those shadows are each behind the little bump that’s casting them. That means that you see less dark areas there than anywhere else. And, of course, the point opposite the sun is exactly where the shadow of your own head lands.
Pretty neat, huh?