Clouds in my coffee
March 18, 2010 4:45 AM Subscribe
Today I poured cream into my coffee whilst standing up. As the cream 'billowed' through the coffee, I happened to rotate my body but kept my eyes on the coffee, and I noticed that the cream 'clouds' seemed to remain in the same place while the mug turned around them, i.e. the turning motion of the mug had no effect on the 'absolute' position of the goings-on inside it. I think this is kinda cool, and I'm just curious: what principle of physics is this based on? Can someone explain to me how/why this works?