The most mysterious moment in a bubble’s life is when it pops and instantly loses its glorious form.
Now researchers have used a high-speed camera to reveal what exactly happens when a hemispheric bubble, the kind that might sit on a soapy glass, bursts.
A bubble may form a plethora of smaller bubbles when it pops, depending on its viscosity, or how thick and glutinous it is, according to a study published in the June 10 issue of the journal Nature.
When a bubble bursts, its surface film folds back onto itself and traps a doughnut-shaped pocket of air, the researchers observed. Surface tension causes this ring to break, resulting in a set of small droplets — or daughter bubbles.
This effect, as far as the scientists can tell, lasts for one more generation before it stops.
The viscosity of the bubble is correlated to the daughter bubble effect, said James C. Bird, a post doctoral fellow at the Massachusetts Institute of Technology and the lead author of the study.
A soap bubble, which has a low viscosity, generates daughter bubbles.
But a bubble made from molasses or chocolate syrup does not.
“Perhaps you’ve noticed this in your kitchen sink,” said Dr. Bird, who did the research while he was a Ph.D. student at Harvard University. “But there wasn’t a real understanding of why that happens before.”