Physics in a bubble
Feb 25, 2000
A fry-up of sausages, eggs and bacon relies on heating oil in a frying pan. However, as many budding chefs know, if you overheat the pan, air bubbles cause the oil to spit, which makes the job messy and painful. Now Rava da Silveira and colleagues from the Massachusetts Institute of Technology have applied physics to this problem to understand how this happens in detail (Science 287 1468).
The MIT team injected small quantities of air into a highly viscous liquid to stimulate the formation of air bubbles. As the bubbles reached the surface, da Silveira and colleagues punctured them with a needle. A high-speed camera recorded the collapse of the bubble.
They discovered that the bubble bursts slowly through the hole punctured in the surface, and that this hole widens as the air inside escapes. Meanwhile, the overhanging surface of the bubble is pulled back into the liquid by surface tension. As the bubble collapses under its own weight, its buckles, causing a series of ripples to rush across the liquid's surface.
According to the experiments and calculations carried out by da Silveira and colleagues, there is a direct relationship between the number of ripples and the bubble radius and liquid viscosity.