If there's one thing we know about bubbles it's that they float, right? Not always. If you've ever ordered a pint of Guinness you may have noticed that the bubbles travel down in the glass, but why? Chemists Richard Zare of Stanford University in California and Andy Alexander of University of Edinburgh in the U.K. explain the science behind this mysterious bubble behavior.
Produced by Stanford University News Service. Submitted by Dr. Richard Zare and Dr. Andy Alexander.