Bubbly beverages are popular among humans, but there’s surprising complexity underlying their seemingly simply carbonation, as explored in a new Physics Today article. Most drinks get their bubbles from carbon dioxide, which at higher than atmospheric pressures, can stay dissolved inside water and other liquids. When that pressure gets released, any carbon-dioxide-filled gas cavity in the liquid adopts the allowable saturation concentration for the ambient pressure, which sets up a concentration gradient of carbon dioxide between the liquid and the bubble. That causes carbon dioxide gas to diffuse into the bubbles, making them grow.
Here on Earth, those growing bubbles are buoyant, and they form rising plumes of bubbles. They continue gathering carbon dioxide as they rise, making them grow ever larger (lower left). In microgravity, on the other hand, the bubbles congregate where they form and continue growing through diffusion (lower right). This is one reason carbonated beverages are unpopular in space – instead of rising to the surface and escaping, all the carbon dioxide in a drink gets consumed, leaving astronauts with no way to expel it aside from burping!
For lots more fascinating facts about bubbly drinks – including how they relate to geology! – check out the full Physics Today article. (Image credits: beer - rawpixel; bubbles - P. Vega-Martínez et al.; see also: R. Zenit and J. Rodríguez-Rodríguez)