FYFD

Tag: physics

  • Catching Krill With Bubble Nets

    Catching Krill With Bubble Nets

    On their own and in groups, some humpback whales enclose their prey in bubbly columns before feeding. The whales build these bubble nets intentionally, swimming in a ring at a constant speed while producing bursts of air from their blowhole. After observing hundreds of bubble nets created by dozens of whales, researchers concluded that whales actively tune the nets, using more rings, closer bubble spacing, or deeper extents to suit their needs. Once they’ve completed the net, whales lunge up through the center, mouth open, collecting their food.

    In their study, the team found that building bubble nets is no more energy intensive for whales than typical lunge-feeding. However, the prey concentration in a bubble net means that hunting there nabs more food per lunge. The authors argue that the way humpback whales build and use bubble nets qualifies them as tool users on par with many fellow mammals, as well as some birds, fish, and insects. (Image credit: C. Le Duc; research credit: A. Szabo et al.; via Gizmodo)

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    The Art of French Drains

    Civil engineers face a constant challenge trying to protect their structures from water — both above and below the ground. Subsurface water can build up enough pressure to lift and damage structures, so engineers use subsurface infrastructure — like French drains — to control the water underground. Despite the name (and my title pun), French drains have nothing to do with France. Instead, they are named for Henry French, an author who described their construction and use in the 19th century. These drains use a combination of rocks, mechanical filters, and perforated pipeline to guide subsurface water and drain it away from foundations. (Video and image credit: Practical Engineering)

  • Synchronizing Cilia

    Synchronizing Cilia

    Just like human swimmers, microswimmers have to coordinate their motion to swim. But unlike humans, swimmers like the freshwater alga Chlamydomonas reinhardtii doesn’t have a brain to help it synchronize its cilia. To investigate how these microswimmers manage their stroke, researchers built a biorobot with mechanically linked segments that mimic the alga’s swimming once a motor sets the robot vibrating.

    When the robot's base is allowed to rotate, the cilia synchronize in the freestyle-like R-mode.
    When the robot’s base is allowed to rotate, the cilia synchronize in the freestyle-like R-mode.
    When allowed to move forward and back, the biorobot's cilia synchronize in the X-mode, which resembles the breaststroke.
    When allowed to move along an axis, the biorobot’s cilia synchronize in the X-mode, which resembles the breaststroke.

    The researchers found two strokes that mirrored the real-life alga. In one, allowing the robot’s base to rotate produced a freestyle-like stroke they called R-mode. The other came from allowing the robot’s base to move forward and backward, which created a breaststroke-like X-mode. In the wild, only the X-mode provides helpful motion, but, oddly enough, the researchers found this mode was the most energy intensive. (Image credit: top – J. Larson, others – Y. Xia et al.; research credit: Y. Xia et al.; via APS Physics)

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    Engineering the City of Venice

    In 452, Roman refugees established what became the city of Venice across a series of low-lying marshy islands in a lagoon. With no solid ground available, Venice has needed clever engineering for its infrastructure, as discussed in this Primal Space video. That started with building the first piles — which still survive to this day — by driving long timbers down into harder clay levels. Because these wooden poles sit entirely below the water and are capped with stone foundations, they are preserved against rotting.

    As Venice grew over the next thousand years, its citizens had other infrastructure problems to solve. When fresh water needs outstripped what could be delivered by boat from the mainland, Venetians redesigned the substructure of each square to capture, filter, and store rainwater. And to wash away waste, they designed tunnels that use gravity and the daily tides to flush out sewage. (Video and image credit: Primal Space)

  • Beneath the Surf

    Beneath the Surf

    A surfer duck-dives beneath a passing wave in this image from photographer John Barton. I always love seeing big waves from this underwater perspective. The turbulent surf looks like storm clouds, and sometimes you see features that are invisible from the surface. Barton’s shot captures the dichotomy of serenity and chaos in the breaking surf. (Image credit: J. Barton/OPOTY; via Colossal)

  • An Exoplanet With Earth-Like Temperatures

    An Exoplanet With Earth-Like Temperatures

    Although researchers have identified thousands of exoplanets in the last 25 years, most of them are far larger and far hotter than Earth. But a team recently announced the discovery of a temperate neighbor, Gliese 12 b, some 40 light years away. Gliese 12 b is a rocky Venus-sized planet orbiting the cool red dwarf star Gliese 12. Based on the star’s energy output and the planet’s characteristics, the team estimate its equilibrium temperature — about how hot it would be without an atmosphere — as 42 degrees Celsius. (For comparison, Earth’s average surface temperature is 15 degrees Celsius and rising.) The next goal will be to determine whether Gliese 12 b has an atmosphere and, if so, what it’s made up of. (Image credit: NASA/JPL-Caltech/R. Hurt; research credit: S. Dholakia et al.; via Gizmodo)

  • Swirls of Green and Teal

    Swirls of Green and Teal

    Captured in March 2024, this satellite image of the Gulf of Oman comes from an instrument aboard the PACE spacecraft. The picture of a phytoplankton bloom is not quite natural-color, at least not as our eyes would see it. Instead, engineers combined data taken from multiple wavelengths and adjusted it to bring out the fine details. It’s not what we’d see by eye, but every feature you see here is real.

    Traditionally, the only way to identify the species of a phytoplankton bloom like this one is by taking a sample directly. But PACE’s instruments can detect hundreds of wavelengths of light, offering enough color detail that scientists may soon be able to identify and track phytoplankton species by satellite image alone. I wonder if distinguishing species could also provide some quantitative flow visualization from a series of these images. In the meantime, at least we can enjoy the view! (Image credit: J. Knuble; via NASA Earth Observatory)

  • Measuring Microfibers in Turbulence

    Measuring Microfibers in Turbulence

    Microplastic pollution is on the rise, especially in waterways. Microfibers — millimeters in length but only microns in diameter — are especially prevalent, as they get washed out of synthetic clothing. Collecting these pollutants first requires understanding how they move and cluster in turbulent flows. Researchers investigated that using a small water channel and high-resolution cameras.

    The team followed microfiber strands as they moved through turbulence, paying special attention to how the fibers tumbled (rotating about their short axis) and spin (rotating around their long axis). How much fibers tumbled depended on the turbulence level; with more intense turbulence, the fibers tumbled more. Rates of spinning, they found, were consistently even higher than those for tumbling. By better understanding how microfibers behave in turbulence, we’ll be able to, for example, predict how far plastics will travel before settling to the ocean floor. (Image credit: Adobe Stock Photos; research credit: V. Giurgiu et al.; via APS Physics)

  • Origins of Salt Polygons

    Origins of Salt Polygons

    Around the world, dry salt lakes are crisscrossed by thousands of meter-wide salt polygons. Although they resemble crack patterns, these structures are actually the result of convection occurring in the salty groundwater beneath the soil. I have covered the physics previously, but this new article by several of the researchers gives a behind-the-scenes glimpse of the investigation itself and how they uncovered the true explanation. (Image credit: S. Liu, see also: Physics Today)

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    “Echo”

    Daniel Kish is an echolocation pioneer, teaching fellow blind people to navigate the world independently. By clicking or tapping and listening to how the sound reflects back, Kish and his students are able to construct a mental map of the world around them. The technique is so effective that they’re able to ride bikes or, as shown with one student in the documentary, learn to skateboard. Check out the full video to see them in action and get a sense of how echolocation works. (Video and image credit: The New Yorker)