Irish mathematicians may have solved the mystery of why bubbles in stout beers such as Guinness sink: it may simply be down to the glass.
Simulations suggest an upward flow at the glass’s centre and a downward flow at its edges in which the liquid carried the bubbles down with it.
But the reasons behind this flow pattern remained a mystery.
Now a study on the Arxiv server reports simulations and experiments showing the standard glass’ shape is responsible.
Of course, their results are not completely conclusive, so amateur physicists are encouraged to investigate the phenomenon for themselves, and see if they can figure it out.