In a pure liquid, most bubbles pop almost immediately. But with a simple ingredient — a little heat — bubbles can live almost indefinitely. The mechanism is revealed in this video when the researchers use an infrared camera to watch a bubble on a heated pool. The top of the bubble is cooler than the rest of the liquid, forming colder, denser droplets that slide down. But the cooler liquid also has a higher surface tension, which draws warm liquid up the bubble, replenishing it. The result is a stable bubble that simply carries on. (Image and video credit: S. Nath et al.)
For fish, collective motions like schooling rely on a few mechanisms, including flow sensing and — as beautifully demonstrated in this experiment — vision. Researchers used an infrared camera to track fish motions both in light and dark conditions and compared how orderly the school of fish was in each. As expected, the school’s motion was much more orderly when the fish could see one another clearly. Interestingly, the researchers then ran an experiment in which the illumination rose continuously from dark to fully bright. The fish school’s organization grew continuously with the light! The better they could see one another, the more organized their schooling. (Video and research credit: L. Baptiste et al.)
A layer of tiny glass beads sitting atop a pool of castor oil becomes a morphing surface in this video. Applying an electric field creates enough electrostatic force to draw the interface upward against the power of both gravity and surface tension. Moving the electric field — either by shifting the electrode or simply moving a finger over the surface — is enough to pull columns of fluid along! I could imagine this making some very cool human-machine interfaces one day. (Image and video credit: K. Sun et al.)
Eagles and other birds spend much of their lives in the turbulence of our atmospheric boundary layer. Some of their interactions with turbulence — like using topographical effects to aid their flight — are well-known, but much remains uncertain. One team of researchers looked at a tagged golden eagle’s flight data, compared with known wind conditions, and looked for evidence of turbulence’s influence. To do this, they drew on years of research into how turbulence interacts with inertial particles — particles that are heavier than the surrounding fluid and thus unable to follow the flow exactly.
What they found is that turbulence seems to be baked into many aspects of the eagle’s flight. Even the basic accelerations of the eagle’s body during flight showed characteristics that match those of turbulent flows. The findings suggest that turbulence — rather than something to be avoided — is an integral part of flight for birds, an energy source they’ve learned to exploit. (Image credit: J. Wang; research credit: K. Laurent et al.; submission by G. Bewley)
During lockdown, photographer Doris Mitsch turned her eyes to the sky and began capturing these mesmerizing composite images of animals in flight. Vultures, crows, starlings, gulls, and bats all feature in her series. Some images, like “Lockdown Vulture (Signature)”, feature a single bird’s movement over a minute. Others show entire flocks over extended periods.
I love how the images capture a sense of speed. Given equal timing between images, the lines with more space between each snapshot of a bird indicate a faster speed. It’s a bit like having particle image velociometry frames stacked atop one another! (Image credit: D. Mitsch; via Colossal)
In many geophysical and metallurgical processes, there is a stage with a porous layer of liquid-infused solid known as a mushy layer. Such layers form in sea ice, in cooling metals, and even in the depths of our mantle. Within the mushy layer, temperature, density, and concentration can vary dramatically from one location to another.
The image above shows a mushy layer made from a mixture of water and ammonium chloride. Above the mushy layer, green plumes drift upward, carrying lighter fluid. Look closely within the mushy layer and you’ll see narrow channels feeding up to the surface. These are known as chimneys. In sea ice, chimneys like these carry salty brine out of the ice and into the seawater, increasing its salinity. See this Physics Today article for more details on the dynamics of mushy layers. (Image credit: J. Kyselica; via Physics Today)
The splash of a droplet is a surprisingly complex phenomenon, depending not only on the droplet’s characteristics but also the surrounding air pressure, the roughness and temperature of the impact surface, and the surface’s curvature. In this study, researchers investigated the effects of surface curvature on splashing, finding that it’s harder for a drop to splash on spheres of smaller radius than ones with a larger radius of curvature.
In Image 1, the falling droplet coats the 2-mm sphere with no sign of splashing. But as the radius gets larger (Images 2 and 3), splashing becomes more and more pronounced. They found that the splash suppression is due to a modification of the lift force on the leading edge of the lamella, the thin liquid layer created as the drop impacts and spread. (Image, research, and submission credit: T. Sykes et al.; also available here)
In 1904, Scottish architect Charles Rennie Mackintosh created the Hill House, a masterpiece of modern design decades ahead of its time. Unfortunately, the Portland cement used for the house’s exterior has not held up well to a century of Scottish rains. As water saturated the cement, it began to dissolve and crumble. So to save the property, conservators commissioned the giant chainmail Box that currently surrounds the house. It protects the house from rain while allowing ventilation that dries the house out slowly. As an added bonus, the superstructure allows visitors to appreciate the house from new angles. (Video credit: T. Scott; via Colossal)
Ionic liquids are essentially salts in a liquid form. In these images, a mixture of water and ionic liquid separates when heated. This phase separation causes the initial mixture to break into two regions: one low in ionic liquid and one rich in ionic liquid. Because the surface tensions of these two phases are different from one another, complex flow patterns form. (Image and research credit: M. Pascual et al.)
I’m not normally one to talk about myself here on FYFD. This site was made to keep the focus on the science, but I’m making an exception today to share a very special exhibit that I’m a part of: the #IfThenSheCan Exhibit, which opens today at the Smithsonian in Washington, DC as part of their #WomensFuturesFestival.
The exhibit features over 120 statues of real women in STEM careers — everything from robotics to marine biology, artificial intelligence to aerospace engineering. It is an absolutely amazing bunch of women, and I am so honored to be a part of it.
My statue, while on display in Dallas. Photo by Regina Binz.
If you’re in the DC area before March 27th, be sure to swing by the National Mall and see the statues. (If not, you can take a virtual tour, too!) Currently, they are all located at the Arts + Industries Building, the Smithsonian Castle and the adjacent Enid A. Haupt Garden, but after March 7th, some of the statues will move to other museums around the Mall. Mine is heading to the National Air and Space Museum!
When I was twelve years old, I visited DC for the first time, and everything about that trip made a huge impression on me. I was in awe of the history, the memorials, the public transit, and, most of all, the National Air and Space Museum. My parents complained that every time we walked the Mall, I made a beeline — as if drawn by a magnetic field — right up the steps of that building. To be a part of that museum now, some twenty years later, is something I never could have imagined.
I’m so proud to be part of this initiative full of amazing women inspiring the next generation of STEM innovators! Special thanks to AAAS and Lyda Hill Philanthropies for making it all possible. (Image credits given in each description/caption.)
