"Irish Mathematicians Solve The Guinness Sinking Bubble Problem
Bubbles sink in Guinness because of the peculiar
geometry of pint glasses, say a dedicated group of researchers at the
University of Limerick
As many drinkers will attest, the bubbles in Guinness appear to sink as the drink settles and the head forms. How can this be, given that bubbles are less dense than the surrounding fluid and so should rise?"
FOR THE ANSWER READ THE FULL STORY at the Physics arXiv Blog from the MIT Technology Review.