Why do bubbles in a stout seem to sink?
Sinking bubbles in stout beers
Why do bubbles in a pint of stout look like they’re sinking? Mathematicians explain the glass is to blame.
In a freshly poured stout, the tiny bubbles near the glass appear to drift downwards, which seems to break the rules of bubbles. Irish mathematicians modelled the flow inside the glass to find out why.
The bubbles really do rise in the middle, and the classic pint glass, which widens towards the top, makes the liquid near the wall flow down and carry the small bubbles with it. A cosy pub mystery, solved.
The bubbles aren’t rebelling. They’re just going with the flow.