FYFD

Tag: science

  • Dancing Metal Droplets

    Dancing Metal Droplets

    Droplets of a gallium alloy are liquid at room temperature. When spiked with aluminum grains and immersed in a solution of NaOH, the droplets change shape and move in a random fashion. This video delves into the phenomenon, describing how a chemical reaction with the aluminum grains changes the local surface tension and creates Marangoni flows that make the droplets move. To get the droplet motion, you need to have the aluminum concentration just right. With too little, there’s not enough Marangoni flow. With too much, the hydrogen gas produced in the chemical reaction disrupts the droplet motion. (Video and image credit: N. Kim)

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    “Creation”

    Videographer Vadim Sherbakov’s short film “Creation” is full of glittery vistas created under a macro lens. Shifting, particle-seeded flows shimmer in bright colors. Glistening deltas shift and form, and Marangoni flows generate feathers and tree-like dendritic arms. Macro flows never cease to fascinate. (Video and image credit: V. Sherbakov; via Colossal)

  • Lava Meets Leidenfrost

    Lava Meets Leidenfrost

    Drop water on a surface much hotter than its boiling point, and the liquid will bead up and skitter over the surface, levitated on a cushion of its own vapor. In addition to making the drop hypermobile, this vapor layer insulates it from the heat of the surface, allowing it to survive longer than it would at lower temperatures. Known as the Leidenfrost effect, this phenomenon can show up in lava flows, as well.

    Pillow lava is a smooth, bulbous rock formed when lava breaks out underwater. The exiting lava is incandescent and, therefore, incredibly hot — hot enough to vaporize a layer of water surrounding it. The lava can continue to expand until it cools too much to sustain the vapor layer. An elastic skin builds up over the cooling lava. Eventually, a new pillow will bud off, possibly due to a surge in the lava flow or a weak point in the developing skin. (Image credit: J. de Gier; research credit: A. Mills; via LeidenForce)

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    Inside Cuttlefish Suction

    Cuttlefish, like many cephalopods, catch prey with their tentacles. Suction cups along the tentacle help them hold on. In this video, researchers share preliminary studies of what goes on inside these suction cups as they’re detached. The low pressures inside the suction cup cause water to vaporize, temporarily. As seen for both the cuttlefish and a bio-inspired suction cup, small bubbles form inside the attached cup, coalesce into larger bubbles, and then get destroyed in the catastrophic leak that occurs once part of the suction cup detaches. (Video and image credit: B. Zhang et al.)

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  • Venusian Gravity Currents

    Venusian Gravity Currents

    Radar measurements of Venus‘s surface reveal the remains of many volcanic eruptions. One type of feature, known as a pancake dome, has a very flat top and steep sides; one dome, Narina Tholus, is over 140 kilometers wide. Since their discovery, scientists have been puzzling out how such domes could form. A recent study suggests that the Venusian surface’s elasticity plays a role.

    According to current models, the pancake domes are gravity currents (like a cold draft under your door, an avalanche, or the Boston Molasses Flood), albeit ones so viscous that they may require hundreds of thousands of Earth-years to settle. Researchers found that their simulated pancake domes best matched measurements from Venus when the lava was about 2.5 times denser than water and flowed over a flexible crust.

    We might have more data to support (or refute) the study’s conclusions soon, but only if NASA’s VERITAS mission to Venus is not cancelled. (Image credit: NASA; research credit: M. Borelli et al.; via Gizmodo)

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  • La Grande Dune du Pilat

    La Grande Dune du Pilat

    Southwest of Bordeaux in France stands Europe’s tallest sand dune, La Grande Dune du Pilat. Some 2.7 kilometers long and over 100 meters high, this dune took shape here over thousands of years. It moves inland a few meters every year as winds blowing from the Atlantic push sand up its shallow seaward side to the dune’s crest. There, sand will avalanche down the steeper leeward side, advancing the dune little by little. The dune’s accumulation has not been steady; during cooler and drier times, sand has collected there, but it took warmer and wetter climes to grow the forests that have helped stabilize the soil and build the dune higher. Humanity has played a role as well, at times introducing new tree species to stabilize the dune. (Image credit: W. Liang; via NASA Earth Observatory)

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  • Bright Night Lights

    Bright Night Lights

    A coronal mass ejection from the Sun set night skies ablaze in mid-October 2024. This composite panorama shows a busy night sky over New Zealand’s South Island. A widespread red aurora was joined by a green picket-fence aurora and a host of other magnetohydrodynamic phenomena. To the left shines a bright Stable Auroral Red (SAR) arc. On the right near the Moon hangs the purple arc of a STEVE — strong thermal emission velocity enhancement. All of these auroras (and aurora-adjacent phenomena) take place when high-energy particles from the solar wind interact with molecules in our atmosphere. Which molecules they encounter determines the color of the aurora, and the shape depends, in part, on which magnetic lines the particles get funneled down. With strong solar storms like this one, auroras can reach far from the poles, and, as seen here, can show up in many varieties. (Image credit: T. McDonald; via APOD)

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  • Glimpses of Coronal Rain

    Glimpses of Coronal Rain

    Despite its incredible heat, our sun‘s corona is so faint compared to the rest of the star that we can rarely make it out except during a total solar eclipse. But a new adaptive optic technique has given us coronal images with unprecedented detail.

    A solar prominence dancing in the Sun's magnetic field lines.

    These images come from the 1.6-meter Goode Solar Telescope at Big Bear Solar Observatory, and they required some 2,200 adjustments to the instrument’s mirror every second to counter atmospheric distortions that would otherwise blur the images. With the new technique, the team was able to sharpen their resolution from 1,000 kilometers all the way down to 63 kilometers, revealing heretofore unseen details of plasma from solar prominences dancing in the sun’s magnetic field and cooling plasma falling as coronal rain.

    Coronal rain -- cooler plasma falling back down along magnetic lines.

    The team hope to upgrade the 4-meter Daniel K. Inouye Solar Telescope with the technology next, which will enable even finer imagery. (Image credit: Schmidt et al./NJIT/NSO/AURA/NSF; research credit: D. Schmidt et al.; via Gizmodo)

  • Bow Shock Instability

    Bow Shock Instability

    There are few flows more violent than planetary re-entry. Crossing a shock wave is always violent; it forces a sudden jump in density, temperature, and pressure. But at re-entry speeds this shock wave is so strong the density can jump by a factor of 13 or more, and the temperature increase is high enough that it literally rips air molecules apart into plasma.

    Here, researchers show a numerical simulation of flow around a space capsule moving at Mach 28. The transition through the capsule’s bow shock is so violent that within a few milliseconds, all of the flow behind the shock wave is turbulent. Because turbulence is so good at mixing, this carries hot plasma closer to the capsule’s surface, causing the high temperatures visible in reds and yellows in the image. Also shown — in shades of gray — is the vorticity magnitude of flow around the capsule. (Image credit: A. รlvarez and A. Lozano-Duran)

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  • Building a Better Fog Harp

    Building a Better Fog Harp

    On arid coastlines, fog rolling in can serve as an important water source. Today’s fog collectors often use tight mesh nets. The narrow holes help catch tiny water particles, but they also clog easily. A few years ago, researchers suggested an alternative design — a fog harp inspired by coastal redwoods — that used closely spaced vertical wires to capture water vapor. At small scales, this technique worked well, but once scaled up to a meter-long fog harp, the strings would stick together once wet — much the way wet hairs cling to one another.

    The group has iterated on their design with a new hybrid that maintains the fog harp’s close vertical spacing but adds occasional cross-wires to stabilize. Laboratory tests are promising, with the new hybrid fog harp collecting water with 2 – 8 times the efficiency of either a conventional mesh or their original fog harp. The team notes that even higher efficiencies are possible with electrification. (Image credit: A. Parrish; research credit: J. Kaindu et al.; via Ars Technica)

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