Tunisia-A Tunisian student solves a 100-year-old physics enigma

Wassim Dhaouadi a student at the Swiss Federal Institute of Technology Lausanne succeeded in solving a mystery that has baffled scientists for 100 years. He found why gas bubbles in narrow vertical tubes seem to remain stuck instead of rising upward. According to his research and observations, an ultra-thin film of liquid forms around the bubble, preventing it from rising freely. And he found that, in fact, the bubbles are not stuck at all—they are just moving very, very slowly.

Dhaouadi and EMSI lab head, John Kolinski, used an optical interference method to measure the film, which they found to be only a few dozen nanometers (1 x 10^-9 meters) thick. The method involved directing light onto an air bubble inside a narrow tube and analyzing the reflected light intensity. Using the interference of the light reflected from the tube’s inner wall and from the bubble’s surface, they precisely measured the film’s thickness.

“I was happy to carry a research project early in my curriculum. It is a new way of thinking and learning and was quite different from a Homework set where you know there is a solution, although it may be hard to find. At first, We did not know if there would even be a solution to this problem.,” says Dhaouadi, who is now completing a Master’s degree at ETH Zurich.