At breakfast this morning, I was looking at a thin film of milk on the spoon resting in my bowl, and noticed a very rapid sparkling. It looked like some sort of white noise - very fine, and very fast. If you've ever looked at a moving laser spot while squinting, it was kind of like that.
I have a couple theories. I know milk is a colloidal suspension, and the fat particles might be small enough to exhibit Brownian motion. Now if the particles are reflective, that could make them sparkle. Or maybe there's some diffraction going on. But I'm not really sure.
Anybody know what actually causes this?