Published in the February 2016 issue of National Geographic magazine
Walking with a filled-to-the-brim glass of water can be treacherous, but that same journey with a latte or beer is much easier. Scientists at Princeton University think they’ve figured out why: Foam on the surface of a liquid hinders sloshing. To test the hypothesis, the researchers created bubble layers by injecting air into a water, glycerin, and dishwashing solution. When they moved containers full of the solution in ways that would normally cause spills—quickly side to side and steadily back and forth—the bubbles damped the sloshing. Because spilling is dangerous when transporting hazardous liquids such as oil, adding foam could make those trips safer.
—Lindsay N. Smith