My dog eats and drinks out of metal bowls. I’ve noticed that when I turn around after filling up the water bowl in the sink, any spit bubbles or backwash on the surface of the water stay oriented the same way (relative to everything else, not me). Why is this? This behavior doesn’t change regardless of how fast or slow, careful or not I am. I’m not sure what kind of metal the bowl is, but it’s about the size and shape of half a basketball. Where I live, the tap water is pretty damn clean. If there are any extraneous factors I haven’t thought to mention, let me know.
Yes, just inertia explains what’s described. I’m in the habit of drinking a hot beverage that sometimes has bits of stuff floating in it, and if there’s one floating bit I want to slurp up right away the practical way to get it over to the side of the cup I’m drinking from is to turn around until I’m on the same side of the cup that it is. I rotate, the liquid doesn’t. It’s’ true that “the water will eventually catch up” to the rotation of the bowl, but it might take quite a lot of rotations before it gains any appreciable momentum. The viscosity of water is relatively low.
Personally, I just got good at the cup swirl motion. Enough to get it rotating without the wave going over the top. Mostly just the lazier option but it is much less convenient to turn yourself when at a desk. lol