Once they accomplished that, however, they did something different: they changed the orientation of the bubble relative to gravity. Their first experiments were aimed at replicating how viscous bubble collapse had been studied in the past. Until now, scientists thought that the weight of the thin liquid film was responsible both for the bubble’s collapse and for the formation of the radial wrinkles – suggesting that gravity was the main factor behind viscous bubble bursting.īird and colleagues set out to test this hypothesis by injecting an air bubble into a viscous silicone oil and filming the bubble’s collapse with a high-speed camera. Without the support of this gas, the forces on the liquid film become unbalanced, causing the bubble to collapse and radial wrinkles to form around the bubble’s edge – rather like what happens in an elastic sheet, or a parachute. The reason is that as soon as the hole forms, trapped gas can escape from the bubble. In thicker, viscous fluid, it takes longer, yet the film collapses when the hole is barely open. In runny, low-viscosity liquids, the bursting process is over in a matter of milliseconds. Once this film develops a hole, surface tension causes the film to retract further, and the bubble bursts. When a bubble rises to the surface of a liquid, it typically forms a thin, liquid, dome-shaped film supported by the gas trapped inside it. Their result has implications for industrial processes such as glass manufacturing and spray painting and could even shed light on the break-up of respiratory aerosols – a phenomenon that has taken on extra significance due to the COVID-19 pandemic. Now, however, researchers led by James Bird at Boston University in the US have turned this idea literally on its head, using an upside-down bubble-testing rig to show that surface tension, not gravity, is at fault. What causes a bubble to burst? For bubbles on the surface of viscous liquids such as paint or lava, the finger of blame has long pointed to gravity. Webinars Tune into online presentations that allow expert speakers to explain novel tools and applicationsĪ viscous bubble film with sufficiently large viscosity will collapse under the force of surface tension.Video Watch our specially filmed videos to get a different slant on the latest science.Podcasts Our regular conversations with inspiring figures from the scientific community.Audio and video Explore the sights and sounds of the scientific world.Supercool physics Experiments that probe the exotic behaviour of matter at ultralow temperatures depend on the latest cryogenics technology.The science and business of space Explore the latest trends and opportunities associated with designing, building, launching and exploiting space-based technologies.Revolutions in computing Find out how scientists are exploiting digital technologies to understand online behaviour and drive research progress.Nanotechnology in action The challenges and opportunities of turning advances in nanotechnology into commercial products.#BlackInPhysics Celebrating Black physicists and revealing a more complete picture of what a physicist looks like.Artificial intelligence Explore the ways in which today’s world relies on AI, and ponder how this technology might shape the world of tomorrow.Collections Explore special collections that bring together our best content on trending topics.
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