Why Guinness Bubbles Sink

Science has answered the question that has beguiled beer drinkers for ages: why the bubbles in Guinness sink.

"If you imagine your pint is full of bubbles, then the bubbles will start to rise," Dr Lee said.

But the bubbles in a standard pint glass find themselves in a different environment as they rise straight up.

"Because of the sloping wall of the pint, the bubbles are moving away from the wall, which means you're getting a much denser region next to the wall," Dr Lee explained.

"That is going to sink under its own gravity, because it's less buoyant, and that sinking fluid will pull the bubbles down."

The bubbles, that is, are "trying" to rise, but the circulation that creates drives fluid down at the wall of the glass.

"You'll see sinking bubbles not because the bubbles themselves are sinking, but because the fluid is and it's pulling them down with it."

I can think of one appropriate way to celebrate this scientific breakthrough! Link


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