I have a very vivid memory of a foggy morning from my childhood. Our bus would get to school 10 or 15 minutes before class started so if it was a nice day we would play outside before the bell rang. The fog was so thick the entire playground was an impenetrable white wall. Except the baseball diamond. Something was different between the dirt on the infield and the grass on the outfield. The dirt was clear while the fog clung to the wet grass. We took turns running across the dirt and jumping into the grass. That kid would seemingly vanish into that vertical wall of cloud. It was super cool but never repeated.