The bubbles do go down! And I though I was crazy all this time.
From The Seattle PI:
SEATTLE POST-INTELLIGENCER
http://seattlepi.nwsource.com/national/165035_beer17.html
Booze flash! Tests confirm that beer bubbles do fall
Wednesday, March 17, 2004
By ANDRE PICARD
THE (TORONTO) GLOBE AND MAIL
It wasn’t exactly one of the great mysteries of the universe, but it was a source of countless bar bets: When beer is poured into a glass, do the bubbles rise or fall? Barflies know all too well that the bubbles fall, seemingly defying the laws of physics.
But now, just in time for St. Patrick’s Day, it’s official.
Using a super-slow-motion video camera – able to record 750 frames a second – Stanford University scientists with a penchant for some cold Guinness have confirmed that beer bubbles do fall.
But careful analysis of the tape has revealed that, while bubbles are lighter than beer and should rise, the laws of physics need not be rewritten after all.
“The answer turns out to be really very simple,” said Richard Zare, a professor of natural sciences at Stanford.
He said the old axiom, “What goes up, must come down,” actually holds true.
"In this case, the bubbles go up more easily in the center of the beer glass than on the sides because of the drag from the walls. As they go up, they raise the beer, and the beer has to spill back, and it does.
“It runs down the sides of the glass carrying the bubbles – particularly little bubbles – with it, downward,” Zare said.
They are not the first scientists to tackle this frothy question.
In fact, in 1998, Australian researchers announced that they had created a computer model showing that it was theoretically possible for beer bubbles to flow downward. They based the simulation on the motion of bubbles in a glass of Guinness draft, a popular Irish beer that contains both nitrogen and carbon dioxide gases that bubble.
But Zare and postdoctoral student Andrew Alexander were skeptical, so they set out to test the theory by “analyzing” beer at both the pub and in the lab.
“Andy and I first disbelieved this and wondered if people had maybe too much Guinness to drink,” Zare said.
But, time and time again, the beer bubbles did fall, not only in pints of Guinness, but in pints of Boddingtons, a British ale, that does not contain nitrogen.
“The bubbles are small enough to be pushed down by the liquid,” said Alexander, who is now a professor of chemistry at the University of Edinburgh.
In fact, they showed that it is possible to produce sinking bubbles in almost any liquid – for example, in a glass of water into which is dropped a tablet of Alka-Seltzer. And, for the record, the shape of the glass doesn’t matter, but keeping a glass at room temperature will enhance the bubble effect.
While they admitted the experiments were done in good fun, both scientists insisted that the research on sinking bubbles has applications beyond settling barroom bets.
Zare said the sinking-bubble phenomenon provides valuable insight into how liquids flow, which can have important applications in the fields of chemistry and engineering.
© 1998-2004 Seattle Post-Intelligencer