a gravitational pull

The pour shot, a staple of beer ads, may never have been more glorified than in such TV spots as “Why man has five senses” for Guinness Stout, by Weiss Stagliano Partners in New York.
But observant drinkers may note an unusual characteristic of Guinness: In a newly poured pint, air bubbles on the side of the glass appear to float downward, seemingly defying the fact that air is lighter than Stout.
Why this happens has now has been answered by a computer, according to Fluent, the New Hampshire maker of Fluent software. The company said a research team from the University of New South Wales in Sydney, Australia, determined through “computational fluid dynamics” software that Guinness rises up the glass’s center with larger bubbles, then moves to the walls, dragging small bubbles down the walls. Study results can be seen at www.Fluent.com.
Keith Hanna, Fluent director of marketing communications, said the study, which came “out of the blue,” has some applications in the food and beverage industry. “It shows our software in a way people can understand,” he said. –Trevor Jensen