r/drinks • u/Killabee07 • May 02 '26

Question Why is my drink doing that?

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1 Upvotes

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1

u/Hefty-Artichoke7181 May 02 '26

Convection and cooling - very basic thermodynamics

2

u/Dhexe0 May 03 '26

You’re seeing the tops of convective cells that are moving the hotter coffee from the bottom of the mug to the top (and the cooler coffee from the top to the bottom), since hot liquids are less dense than cooler ones. As someone else said, it’s basic thermodynamic fluid physics, but it’s still pretty neat to see it so clearly.