Please bear with me because I'm not that great at physics. I witnessed something earlier today which was the most bizarre thing I have ever seen, and I'm looking for an explanation. I know this sounds contrived but this is exactly what happened without any embellishment: I was at work making two cups of coffee and I poured water from the kettle into the first cup and then as I was pouring water into the second cup, the first cup moved, entirely of its own accord and without me touching it. It turned through 180° whilst sliding to about 2 inches from where it started and was still moving when I grabbed it. So what I think happened is: the kettle is not very good and when you pour the water always dribbles down the spout and pools on the table. So I think that the cup must have been planing on the surface of that water. I reckon the motion of the water inside the cup sloshing around after being poured must have somehow translated into moving the cup. Is this possible? It seems unlikely for something with the mass of a cup of coffee, but I can't think of any other explanation. In case it is relevant: the surface it was on was a laminate kitchen worktop.