Re: Staring at the sky for a long time, what are those flying white dots?

Yes, it makes sense. I heard it too. The explanation I recall is that you see the blood cells running through your capillaries, see http://sln.fi.edu/biosc i/vessels/capillaries.html. The capillaries are so thin that blood cells actually passes them in single cells. When those blood cells passes in your eye capillaries they interfere with the light coming in and leave a blurry image on your retina. You can not focus on them because they are actually too close to focus on. While I know of a book dealing with all those visionary effects, I could not find it. I will surely keep looking for this reference.