So I was driving my dads truck to pick up my sister when I noticed a very interesting pattern in the raindrops sliding across the truck windshield. It was not raining, but I am currently in the northeast and we just got done with a snowstorm so they really weren't raindrops but simply melted snow... Anyway, I observed that the "raindrops" tended to follow a zigzag pattern as they climbed the windshield. This wasn't one path in particular, many of them seemed to move like recognized swimmers akin to a "glider" in the Game of Life. Here is a picture from Wikipedia: It was very fascinating, so much so that I almost missed my exit! I am not sure if the fact that I was following a tractor trailer makes a difference. Perhaps the vortex shedding frequency behind the trailer had something to do with the water pattern on the windshield. Does anyone have any idea what would be causing this pattern?