It's The Darkness In Bubbles That Make Them Pop

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All of us love shimmery rainbow-colored bubbles. Yet, scientists still don't understand why the bubbles pop. Physicist Li Shen led a team of researchers from Imperial College London and Shell Solutions UK observed and made a video of the behavior of concave and convex bubbles made from dish-washing liquid, one minute before their rupture. They found that dark spots on the bubble film grow and converge rapidly when the bubble is about to pop.

American Physical Society (APS) mentions on its site that the video footage recorded by the researcher showed that, in concave bubbles, the areas where the soap film was thick had brighter colors while the areas with a thin film had dark spots. Due to gravity-driven flow, small secluded dark dots started to converge rapidly coarsening the film and leading to the bubble's eventual rupture.

In a convex bubble, small white dots were observed appearing in a non-uniform pattern. The coarsening effect of the soap film was not observed here but it was seen that the pattern spread outward until the bubble popped. Li Shen and his colleagues first presented their findings in the APS's Division of Fluid Dynamics meeting that took place on November 22, 2016.

According to the Science News, the thickness of the soap film determines what colors we see on a bubble's surface. Light rays reflecting off the film amplify particular wavelengths, an effect known as "constructive interference." In areas where the soap film I thick, colors with longer wavelength appears - making us see rainbow colors in a bubble.

As the pull of the gravity causes the soap film to flow, the color patterns of bubbles keep shifting until they burst. In areas where the soap film becomes thinner, colors with shortest wavelength and dark spots appear - an effect which is known as "destructive influence." It has now been seen that these spots grow and merge over the time period of one minute before a bubble pops.