The other day I was working in the lab and observed a very interesting fluid dynamic thing in a beaker: I was cooking acetone on a hot plate to clean a sample, then I see little bubbles on the surface bouncing around. The strange thing is that those bubbles act EXACTLY like a ball on a frictionless surface! They never decelerate (or accelerate for that matter), just travel on a straight line, when ever they hit a obstacle (beaker wall/ sample) they will be bounced back like a tennis ball hitting a wall. That bubbles don't slow down due to friction really bug me. I guess the evaporation provides energy for the motion in a reinforced kind of way to maintain the pattern. Maybe it count as a soliton? And there should be no convection when this happens. I tried to repeat this with 2-propenal, nothing like that happens. With Aceton it works every time. Maybe Acetone has the exact right viscosity/evaporation rate...? So can anyone explain the detailed mechanism? Or it's been done before?