gassor
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If nitrogen or carbon dioxide, or any gas, sank in water, we'd all be in very serious trouble.
If any gas sank in Guinness, how would it get a head?
I would be pretty sure that the pattern on the inside surface of a glass of Guinness, as it settles, is an optical illusion due to the number and size of bubbles rising and liquid draining from the head.
Seems like the bubbles falling in a pint of Guinness has been seriously investigated and the explanation lies in the shape of the tumbler rather than the bubbles. Every day is a school day.
https://www.livescience.com/20731-mystery-guinness-stout-bubbles-solved.html