Colors stream and mix in Rus Khasanov’s short film “Discovery.” Droplet-like liquid lenses float in the mixture until ethanol or other ingredients cause them to spontaneously rupture, sending their interior flowing outward until the lens reaches a new equilibrium. Gradients in surface tension guide Marangoni flows across the screen. There’s never-ending beauty in the world of macro fluids. (Video and image credit: R. Khasanov)
Eighteenth- and nineteenth-century French painters like Chardin and Manet had a certain fascination with bubble-blowing physics. Both left behind artwork depicting children blowing soap bubbles through straws. Now researchers are exploring this bubble-making method in a recent study.
To blow a bubble from a straw or other narrow constriction, there are three basic stages. In the first, the soapy interface bulges and takes on a spherical shape. That’s followed by a period of rapid growth in less than 100 milliseconds. And, finally, the bubble will pinch off and detach from the straw. So far, most studies have focused on that third phase. Instead, this team focused on those early stages.
In that first stage, the bubble’s growth depends on air getting forced out of an attached reservoir. For children, that’s their lungs reducing in volume as they blow air into the straw. In their experiments, the team found that the initial volume of the air reservoir is an important (and previously overlooked) factor in controlling bubble growth. (Image credit: J. Chardin; research credit: M. Grosjean and E. Lorenceau; via Ars Technica)
Blow across the top of a glass bottle, and you’ll get a whistle-like sound. Put some liquid in there and the pitch of the sound changes. Our vocal tracts are basically the same thing: a tube with a hole at the end. But as Joe Hanson shows in this Be Smart video, our ability to change the shape and resonance of our vocal tract by moving our tongues and lips enables us to make a wide range of vowel sounds. Enjoy this dive into the world of linguistic physics! (Video and image credit: Be Smart)
In a cave, mineral-rich water drips from the ceiling, spreading ions used to build stalagmites. A recent study considers how the depth of a pool affects the droplet’s splash and how material from the droplet spreads. The authors found several scenarios that vary widely depending on pool depth.
A drop falling into a shallow pool had a splash that quickly broke up into droplets (above). By dyeing the pool green and the droplet red, they could track where the droplet’s material wound up. The spray of small droplets carried fluid far, but the main point of impact had a strong concentration of the drop’s fluid.
In contrast, a deeper pool sent up a thick-walled splash crown that collapsed in on itself. This droplet’s material saw lots of mixing with the pool, but only near the point of impact. From their work, the authors concluded that models of stalagmite growth should incorporate pool depth in order to capture how minerals actually concentrate and move. (Image credit: cave – H. Roberson, others – J. Parmentier et al.; research credit: J. Parmentier et al.; via APS Physics; submitted by Kam-Yung Soh)
In January 2022, the Hunga Tonga-Hunga Ha’apai volcano erupted spectacularly, sending waves around the world through the air, water, and ground. In many ways, it was unlike any eruption scientists have observed, though they think it bears similarities to the 1883 eruption at Krakatoa. This video summarizes some of the research to come out of the eruption, looking at how waves propagated, what aerosols the volcano pushed high into the atmosphere, and what the long-term effects of the eruption may be. (Video credit: Science)
Expedition guide and photographer Ryan Newburn captures the ephemeral beauty of the glacial caves he explores in Iceland. These caves are in constant flux, thanks to the run and melt of water. The scalloped walls are a sign of this process of melting and dissolution. The icicles, too, hint at ongoing melting and refreezing. Caves can appear and disappear rapidly; they’re a dangerous environ, but Newburn freezes them in time, letting the rest of us experience a piece of their majesty. See more of his images on his Instagram. (Image credit: R. Newburn; via Colossal)
The Earth’s interior is almost entirely inaccessible to humanity, so how do we know what it consists of? As explained in this video, our knowledge of the planet’s interior is based on measuring waves sent out by earthquakes and nuclear blasts. Both produce two kinds of waves — pressure waves (P-waves) and shear waves (S-waves) that travel through the earth and get picked up by seismometers. Scientists noticed that pressure waves travel through the center of the planet while shear waves — which get dissipated in liquids — do not. This led them to conclude that part of Earth’s interior is a liquid. The idea of a solid inner core came from observations of pressure waves scattering in a way that only made sense if they’d hit something solid. (Video and image credit: Science)
The Diamantina River in Australia is dry for much of the year. But seasonal rains flood its riverbeds and provoke a bloom of vegetation along its banks. This false-color satellite image shows the river in April 2023; land appears pale and reddish, the river and its sediment blue, and vegetation a bright green. The Diamantina is an anabranching river; rather than the typical meandering paths of a delta, anabranching rivers have semi-permanent paths hemmed in by vegetation-stabilized islands. Look closely, though, and you’ll still see smaller delta-like features known as floodouts dotting some of the islands. (Image credit: A. Nussbaum; via NASA Earth Observatory)
Bright colors mark this slowly draining soap film. The film sits slightly off-horizontal, so flow shifts over time from the top of the frame to the bottom. The fluid is also evaporating. All the faster shifts are caused by ambient air currents from the room. The colors of the film are directly related to the local thickness; as the film thins and evaporates, the bright colors shift to darker ones. Eventually, that black region at the top will expand and the film will break up. (Video credit: B. Sandnes/Complex Flow Lab)
Snakes’ forked tongues have long inspired fear, but, in reality, they are part of a highly-effective sensory system. When snakes flick out their tongues, they waggle them up and down about 15 times a second. That motion draws air inward toward the tongue (Image 2), allowing scent molecules to stick to the saliva on either side of the tongue. Once those molecules are gathered, the snake pulls its tongue back into its mouth, where it settles into two grooves (Image 3). Each one has its own path to the snake’s olfactory organs, giving the snake independent spots to evaluate the left and right forks. That means the snake knows which side has a stronger scent and is better able to track its prey. (Video and image credit: Deep Look)