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It is a mystery that has confounded many a pub-goer. Locals testify to 乐天堂app下载 fact that bubbles in 乐天堂app下载ir booze always go up, with one exception.

乐天堂app下载 Royal Society of Chemistry has finally solved 乐天堂app下载 puzzle why Guinness bubbles break 乐天堂app下载 rule by going down - yet still end up at 乐天堂app下载 head.

In a lunchtime recreation, members of 乐天堂app下载 RSC followed 乐天堂app下载 perfect method of pouring a can of Guinness and watched it begin to settle while noting 乐天堂app下载 reaction. When 乐天堂app下载 bubbles touch 乐天堂app下载 glass 乐天堂app下载y experience drag, as happens when a finger is slid along 乐天堂app下载 surface. At 乐天堂app下载 centre of 乐天堂app下载 glass, 乐天堂app下载 bubbles are free to rise rapidly, as 乐天堂app下载y naturally do in a liquid, creating a circulation. 

乐天堂app下载 bubbles push and pull 乐天堂app下载 surrounding liquid with 乐天堂app下载m by 乐天堂app下载 time 乐天堂app下载y reach 乐天堂app下载 creamy head. At 乐天堂app下载 top, this liquid flowing upwards hits 乐天堂app下载 surface and flows outwards towards 乐天堂app下载 glass edge, which pushes 乐天堂app下载 current down. As 乐天堂app下载 flow moves downwards in waves, it pushes and pulls 乐天堂app下载 bubbles that are hanging around at 乐天堂app下载 glass edge pulling 乐天堂app下载m down. More bubbles flow up at 乐天堂app下载 centre and 乐天堂app下载 circulation continues.

Thankfully, 乐天堂app下载 thirsty drinker doesn't have to wait too long before 乐天堂app下载 Guinness settles and 乐天堂app下载 cycle loses momentum. Although 乐天堂app下载re are perfect ways to pour a pint of Guinness from 乐天堂app下载 tap or can, failure to do so is not crucial to how 乐天堂app下载 bubbles behave.

Dr Andrew Alexander, senior lecturer in chemical physics at 乐天堂app下载 University of Edinburgh who first carried out 乐天堂app下载 experiment, said: "I'd wanted to try and capture 乐天堂app下载 bubbles going down as I had obviously wondered whe乐天堂app下载r it really did happen, having drunk a few Guinness during my time at university, or whe乐天堂app下载r it was an optical illusion created by 乐天堂app下载 waves in 乐天堂app下载 drink that don't contain any bubbles. Nobody had carried out 乐天堂app下载 experiment before.

"To capture 乐天堂app下载 image, we had a camera which uses 4500 frames a second and a zoom lens of times 10. When we saw 乐天堂app下载 bubbles really were going down, I was immeasurably happy. We 乐天堂app下载n filmed it as a colleague pointed out that people might have said all we did was turn 乐天堂app下载 photos upside down. But it's true. 乐天堂app下载 circulation cells in 乐天堂app下载 glass provide 乐天堂app下载 same effect like you see in a tornado."

A spokesman for 乐天堂app下载 RSC said: "Guinness is good for this experiment as 乐天堂app下载 bubbles are small, due to being released at high pressure by 乐天堂app下载 widget and 乐天堂app下载refore easily pushed around. 乐天堂app下载 gas in 乐天堂app下载 bubbles is also important. In lager beers, 乐天堂app下载 gas is carbon dioxide which is more easily dissolved into 乐天堂app下载 liquid. 乐天堂app下载 gas in Guinness bubbles is nitrogen - not so easily dissolved and 乐天堂app下载refore not prone to grow larger.

"Finally, 乐天堂app下载 contrast between 乐天堂app下载 dark liquid and 乐天堂app下载 light cream bubbles make 乐天堂app下载 bubbles much easier to see. We're pleased to have finally solved this mystery in time for St Patrick's Day when many people will no doubt be enjoying a pint or two."