I can see Haidinger’s brush. A few minutes ago I did not even know that I could, nor that something like this existed, but now I can clearly see it! Or rather, I always wondered why my LCD screen never seemed to be as white as it seemed to be …
Can you see Haidinger’s brush?
http://en.wikipedia.org/wiki/Haidinger’s_brush
Reminds me of birds using skylight polarisation for navigation: Skylight Polarization Patterns and the Orientation of migratory Birds