FYFD

Tag: physics

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    A Look at Hagfish

    Hagfish are the lords of slime. Their viscoelastic protection mechanism is so effective that they’ve hardly changed up their game in the past 300 million years. Instead, at the first sign of trouble, they release a mucus that rapidly expands in salt water. When attacking fish try to pull water into their gills, they get clogged with slime instead, sometimes suffocating and becoming the hagfish’s meal instead. To get out of their slime, hagfish knot themselves and wipe it away, thanks to its shear-thinning properties. (Image and video credit: Deep Look)

  • Optimal Bubble Clusters

    Optimal Bubble Clusters

    With a bubble wand, it’s quite easy to create clusters of two or more soap bubbles. These clusters seem to instantly find the lowest energy state, forming a shape that minimizes the cluster’s surface area (including interior walls) for the volume of air they enclose. But mathematicians have struggled for thousands of years to prove that this is actually the case.

    In 1995, mathematician John Sullivan had a breakthrough conjecture, at least for some types of bubble clusters. A proof for double bubble clusters quickly followed. But then progress stalled out, with the triple bubble version seemingly out of reach. But now a duo of mathematicians have published proofs for Sullivan’s bubble clusters in triple and quadruple clusters. Learn their story over at Quanta. (Image credit: N. Franz; via Quanta Magazine)

  • Dandelion Seeds

    Dandelion Seeds

    Each seed on the head of a dandelion has a preferred wind direction, according to new research. Seeds facing the breeze are most likely to release from the head, with those facing other directions holding on tens to hundreds of times harder — until their breeze comes along. To measure the force needed to pluck a dandelion seed, researchers superglued a fine wire to individual seeds and pulled from different directions. This seed-by-seed removal mimics winds from varying angles and allowed the researchers to test the directional dependence of seed release. With seeds poised to release in every direction, the dandelion ensures its successful spread. (Image credit: S. Chaudhry; research credit: J. Shields and C. Roh; via Science News; submitted by Kam-Yung Soh)

  • Turning the Beach Pink

    Turning the Beach Pink

    Lab experiments and numerical simulations can only take us so far; sometimes there’s no substitute for getting out into the field. That’s why a beach in San Diego turned pink this January and February, as researchers released a safe, non-toxic dye into an estuary. The goal is to understand how small freshwater sources mix with colder, saltier ocean waters when they meet in the surf zone. Differences in temperature and salinity both affect the waters’ density and, therefore, how they’ll combine, especially in the face of the turbulent surf. Using drones, distributed sensors, and a specially-outfitted jet ski, the researchers collect data about how the dye (and therefore the estuary’s water) spreads over the 24 hours following each dye release. Check out their experiment’s site to learn more. (Image credits: E. Jepsen/A. Simpson/UC San Diego; via SFGate; submitted by Emily R.)

  • The Optical Atom

    The Optical Atom

    Researchers applied a quantum mechanical technique to study an evaporating drop in extreme detail. The team trapped a spherical water drop and collected the light scattered off it as it evaporated. Using an analytic technique originally developed for an atom, they were able to study changes in the drop down to the nanometric level without relying on numerical simulations to interpret the results. The authors suggest that their method is well-suited to studying the concentration of chemical or biological contaminants on the surface of a drop as it evaporates. (Image credit: droplet – Z. Kaiyv, Fano combs – J. Marmolejo et al.; research credit: J. Marmolejo et al.; via APS Physics)

    Illustration of the Fano combs seen by analyzing light scattered from an evaporating drop.
    Illustration of the Fano combs seen by analyzing light scattered from an evaporating drop.
  • Racing Dunes

    Racing Dunes

    The deserts of Namibia are home to some of the fastest and most consistent winds in the world. As a result, they’re also home to some of the fastest-moving dunes on Earth. Dunes are shaped and moved by the wind, which pushes sand up the dune’s windward side and dumps it down the leeward side. As the process repeats, the entire dune moves. The bigger a dune is, the slower it moves.

    Animation of Landsat images showing dune movement between April 2013 and April 2022.
    Animation of Landsat images showing dune movement between April 2013 and April 2022.

    In this animation, showing dune motion from 2013 to 2022, the largest dunes move about 9 meters per year. In contrast, the smallest dunes move as fast as 83 meters a year! Check out the right side of the image, and you’ll see the dark specks of small dunes racing up and past their bigger brethren. (Image credit: top – E. Böhtlingk, animation – J. Stevens; via NASA Earth Observatory)

  • “Dark Matter”

    “Dark Matter”

    In “Dark Matter” photographer Alberto Seveso captures billowing black pigment against a bright red backdrop. Seveso excels at capturing the developing turbulence in sinking fluids. I’m always blown away by the texture in his images; it almost makes the fluid look fabric-like and solid. Look closely in some of these images and you can catch a few tiny Rayleigh-Taylor instabilities, too, as the denser pigment sinks through water. (Image credit: A. Seveso)

  • Martian Wind Power

    Martian Wind Power

    To support a crew on Mars, a landing site must offer resources like water and allow for sufficient power generation. Thus far, most analyses of this sort have focused on the possibilities of solar power, which is limited by day-and-night cycles and seasonal variations, and nuclear power, which carries some risk to the human crew. In a new report, researchers considered the possibilities of wind power on Mars.

    Since Mars’s atmosphere is so much thinner than Earth’s, wind power has largely been overlooked as an energy source there. But researchers found that a commercially-rated wind turbine expected to produce 330 kW here on Earth could still output a respectable 10 kW on Mars. Since the target power needs for a crew are 24 kW, adding wind energy can boost a power system from providing 40% of needs from solar alone to 60-90% of the needed energy from combined solar and wind sources. A wind turbine is especially helpful in supplementing power needs at times when solar power wanes, like at night or during the Martian winter solstice. (Image credit: NASA; research credit: V. Hartwick et al.; via Physics World)

  • Frozen in Ice

    Frozen in Ice

    Air can dissolve in water, but not in ice. So as water freezes, any dissolved gases have to get squeezed out in order for the ice crystals to grow. Once the concentration of gases is high enough, a bubble nucleates and gets captured by the growing ice around it. The shape of the final bubble depends on its freezing conditions. As seen here, bubbles take on all kinds of shapes, ranging from egg-like to a long and skinny squash-like shape. (Image credit: V. Thiévenaz and A. Sauret)

  • Swimming Intermittently

    Swimming Intermittently

    Many fish do not swim continuously; instead, they use an intermittent motion, swimming in a sudden burst and then coasting. This intermittent swimming is tough to simulate, due to its unsteady nature, but a new study does so using some clever computational techniques.

    Animation showing a fish swimming in a burst-and-coast pattern.
    Animation showing a fish swimming in a burst-and-coast pattern.

    Researchers suspected that the energy intensity of a fish’s burst could be balanced by the low-drag, low-effort phase of coasting. And, indeed, that’s consistent with the team’s results. But they found that the swimming method does require careful optimization; with the wrong cadence, the burst-and-coast technique can be incredibly energy intensive. In nature, of course, fish have had millions of years to optimize their technique, but the results serve as a warning to those building fish-based robots. Those biorobots will need careful optimization to benefit from this swimming style. (Image credit: tetra – Adobe Stock Images, simulation – G. Li et al.; research credit: G. Li et al.; via APS Physics; submitted by Kam-Yung Soh)