London, Mar 17 (ANI): Bubbles in the famous Irish brew Guinness go down instead of up, say researchers.
Be it any pint of beer, the drink's bubbles obey the normal laws of physics and rise to the surface and form a frothy head thanks to the buoyant gas fill-up.
However, Guinness does things differently.
The bubbles in a freshly poured pint appear to be cascading down the side of the glass, yet the creamy top remains.
Now, members of the Royal Society of Chemistry used a super-fast camera that could zoom in and magnify the bubbles 10 times to solve the puzzle.
After the analyses, boffins found that more visible outlying bubbles in a pint of Guinness did move downwards, as a result of circulation flow and drag. At the centre of the glass, the bubbles were free to rise rapidly, pulling the surrounding liquid with them and setting up a circulating current.
Flowing outwards from the surface, the frothy "head", the current hit the glass edge and was pushed down. Bubbles held back by dragging on the side of the glass were caught in the circulation and forced to go with the flow - the wrong way, for a bubble, reports The Telegraph.
Dr Andrew Alexander, senior lecturer in chemical physics at the University of Edinburgh, who led the researchers, said: "I'd wanted to try and capture the bubbles going down as I had obviously wondered whether it really did happen, having drunk a few Guinness during my time at university, or whether it was an optical illusion created by the waves in the drink that don't contain any bubbles. Nobody had carried out the experiment before.
"To capture the image, we had a camera which uses 4,500 frames a second and a zoom lens of times 10. When we saw the bubbles really were going down, I was immeasurably happy.
"We then filmed it as a colleague pointed out that people might have said all we did was turn the photos upside down. But it's true. The circulation cells in the glass provide the same effect like you see in a tornado."
A spokesman for the RSC, based in Piccadilly, London, said:
"Guinness is good for this experiment as the bubbles are small, due to being released at high pressure by the widget and therefore easily pushed around.
"The gas in the bubbles is also important. In lager beers, the gas is carbon dioxide which is more easily dissolved into the liquid. The gas in Guinness bubbles is nitrogen - not so easily dissolved and therefore not prone to grow larger.
"Finally, the contrast between the dark liquid and the light cream bubbles make the bubbles much easier to see." (ANI)
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