Explain about peanuts dancing beer

In Argentina, bartenders often treat customers with «dancing» peanuts. Setting the beer down in front of a patron, the bartender drops a peanut into the bubbling liquid. The peanut sinks because the bean is denser than the liquid around it. But then the peanuts started to rise, to the surface of the beer. The peanut then sinks and rises again, continuing in this cycle until the customer gets bored and drinks their beer. Researchers now have a physical description for this interesting stick trick, which bears similarities to processes occurring in Earth’s magma [1].

For their experiments, Luiz Pereira of Ludwig Maximilian University in Munich and colleagues dropped whole roasted peanuts, shelled, into a 1-liter lager-style beer barrel. They then recorded the peanut’s movements with a camera.

The videos show that as soon as a peanut falls into the liquid, air bubbles begin to cling to its surface. These bubbles continue to build up after the peanuts sink until enough for the peanuts to float to the surface of the beer. As the peanut floats to the surface, it begins to rotate around its long axis, causing the bubbles to burst and their floating air to dissolve. When a large enough bubble bursts, the peanut loses buoyancy and sinks again. In a pint of beer, this process takes only a few seconds and repeats for an average of 150 minutes until the peanut is completely submerged.

The researchers modeled this process, finding that the nucleation bubbles on the surface of peanuts were more energetically favorable than on glass or in liquids. This advantage comes from the relatively high contact angle that the surface of the peanut provides for bubble nucleation.

Michael Manga, a planetary scientist at the University of California, Berkeley, says that the motions of the hopping beans could help understand gas-induced processes in other systems, such as in the crust. Earth, it is difficult and dangerous to probe experimentally. The surfaces of the liquid magma regions of the Earth’s crust are often decorated with magnetite, the crystalline mineral form of magma. As a solid mineral, magnetite is denser than liquid magma, so why does it float? The leading explanation for magnetism’s buoyancy is that it comes from gas bubbles in the magma that cling to the surface of the mineral, causing it to float.

Once it has risen, the magnetic crystals will not sink, as is the case with peanuts. But Manga—and Pereira—think beer and peanuts could allow researchers to get a safe, close-up look at how the foaming and degassing processes might work in magma. The manga says that the process by which bubbles nucleate on the surface of an object is something that scientists do not fully understand. «[Bubble nucleation] is a phase transition where you go from one state to another and all the phase transitions involve unnecessary physics,” he said.

Pereira says that he and his colleagues are currently testing how different beers and different types of peanuts affect how the peanuts dance. For example, Pereira says that in a highly carbonated beer, such as craft beer, the peanuts will float to the surface longer than in a less carbonated beer, such as the light beer they use. for his experiments. That’s because bubbles continue to build up on the peanut while it’s on the surface and do so at almost as fast a rate as they disappear. Meanwhile, broken peanuts seem to float forever, as they rotate less easily and are therefore able to maintain their bubble buoyancy aid.

– Allison Gasparini

Allison Gasparini is a freelance science writer based in Santa Cruz, CA.

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