An EPFL Bachelor’s student has solved a mystery that has puzzled scientists for 100 years. He discovered why gas bubbles in narrow vertical tubes seem to remain stuck instead of rising upwards.
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.
Air bubbles in a glass of water float freely up to the surface, and the mechanisms behind this are easily explained by the basic laws of science. However, the same laws of science cannot explain why air bubbles in a tube a few millimeters thick don’t rise the same way.
Physicists first observed this phenomenon nearly a century ago, but couldn’t come up with an explanation – in theory, the bubbles shouldn’t encounter any resistance unless the fluid is in motion; thus a stuck bubble should encounter no resistance.
Back in the 1960s, a scientist named Bretherton developed a formula based on the bubbles’ shape to explain this phenomenon. Other researchers have since postulated that the bubble doesn’t rise due to a thin film of liquid that forms between the bubbles and the tube wall. But these theories cannot fully explain why the bubbles don’t rise upwards.
Source: “EPFL’s student solves a 100-year-old physics enigma”, EPFL News, Laure-Anne Pessina