FYFD

Category: Phenomena

  • A Soft Cell in Microgravity

    A Soft Cell in Microgravity

    There are many shapes that can be tiled to fill space, but nearly all of them have sharp corners. Last year, mathematicians identified a new class of shapes, known as “soft cells,” that feature curved edges and faces but very few sharp corners. Like traditional polyhedrals, soft cells can tile to fill a space completely without overlapping or gapping.

    Now the researchers, with some help from astronauts aboard the ISS, have brought one of their soft cells to life. Using an edge skeleton to guide the shape, astronaut Tibor Kapu filled the skeleton with water, which, in microgravity, formed a perfect soft cell, complete with faces curved by surface tension to their minimal area. See it in action below. (Image and video credit: HUNOR/NASA; research credit: G. Domokos et al.; via Oxford Mathematics)

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    Marangoni Bursting With Surfactants

    A few years ago, researchers described how an alcohol-water droplet atop an oil bath could pull itself apart through surface tension forces. Dubbed Marangoni bursting, this phenomena has shown up several times since. Here, researchers explore a twist on the behavior by adding surfactants to see how they affect the bursting phenomenon. (Video and image credit: K. Wu and H. Stone; via GFM)

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  • In Deep Lakes, Mixing is Disappearing

    In Deep Lakes, Mixing is Disappearing

    With a depth of nearly 600 meters, Crater Lake in Oregon is the deepest lake in the United States. It’s known for its brilliant blue hue and startling clarity. But, like other deep lakes, Crater Lake is changing as temperatures warm. It’s edging ever closer to a day where its deep, cold waters no longer mix.

    Although the details of mixing vary from lake to lake, older records show that most deep lakes would overturn and fully mix on a frequency that ranged from twice a year to every seven years. This overturning happens when winds push frigid, near-frozen water. As that water approaches the shoreline, it gets forced downward, where the pressure at depth makes the cold water denser still, causing it to sink beneath the warmer water layer near the lake bottom. That kicks off larger-scale mixing that redistributes oxygen, nutrients, and toxins in the lake.

    When this regular mixing stops, the entire ecosystem gets affected. Over time, oxygen gets depleted in deeper in the lake, leaving a dead zone unable to support fish and other aquatic life. Meanwhile, longer and warmer growing seasons favor phytoplankton and algae that cloud the waters and disrupt a lake’s unique ecology.

    For a much more detailed look at deep lake mixing and the changes we’re seeing, check out this article over at Quanta Magazine. It’s a longer read but well worth your time. (Image credit: N. Perez Aguilar; see also: Quanta Magazine)

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  • Chlorophyll Eddies

    Chlorophyll Eddies

    Instruments aboard NASA’s PACE mission are able to distinguish far more about phytoplankton blooms than previous satellites. This image shows chlorophyll concentrations in the Norwegian Sea in July 2025. Chlorophyll acts as a proxy for phytoplankton, which produce the chemical as they process sunlight into food and oxygen.

    Despite their microscopic size, phytoplankton have enormous collective effects. Scientists estimate that phytoplankton produce as much as half of the Earth’s oxygen in addition to helping transport carbon dioxide from the atmosphere into the deep ocean. They are also the foundation of the marine food web, feeding nearly all life in the ocean. (Image credit: W. Liang; via NASA Earth Observatory)

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  • Shining in the Sky

    Shining in the Sky

    Shades of blue, green, and purple light the Icelandic sky in this image from December 2023. Incoming solar wind particles hit oxygen and nitrogen atoms high in the atmosphere, exciting their electrons and creating this distinctive glow. We’re currently near the peak of our Sun’s 11-year solar cycle, meaning that high numbers of sunspots and outbursts will continue, likely giving us more stunning auroras like this one. (Image credit: J. Zhang; via APOD)

    An aurora in shades of blue, green, and purple.
    An aurora in shades of blue, green, and purple.

    P.S. – This post–this one right here–is FYFD’s 4000th post! When I started this blog back in 2010 as a graduate student, I never imagined that I would have so much to write about the physics of fluids. But this subject is one that just keeps on giving, so I keep on writing. Thanks for joining the fun! – Nicole

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    Entraining Bubbles

    Every time I fill a glass at my refrigerator, I watch how the falling jet creates a cloud of bubbles. The bubbles form when the impacting water jet pulls air in with it, though, as this video shows, the exact origins can vary. Here, researchers take a closer, slowed-down look at the situation; they connect disturbances in the jet and waves at its base to the entrained bubbles that form. (Video and image credit: S. Relph and K. Kiger)

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  • Whorls of Sea Ice

    Whorls of Sea Ice

    Fresh snow shines white on the southern end of Greenland in this satellite image, taken in late February 2025. Whorls of sea ice sit off the coast, where they trace out patterns that reflect the winds and ocean currents of the region. Arctic sea ice typically reaches its largest extent by early March before experiencing a long season of melting. Both the presence and absence of sea ice have a large effect on the Arctic regions. Sea ice helps dampen wave activity; without it, seas are higher and more dynamic, creating more aerosols that seed cloud cover in the Arctic and elsewhere. (Image credit: L. Dauphin; via NASA Earth Observatory)

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    How to Keep Water From Freezing

    When supercooled, water can remain a liquid even below its freezing point. As explained in this Minute Physics video, this happens because of a tug-of-war between effects in the water. Generally speaking, having impurities in the water or smacking the bottle will shift that battle enough for freezing to win out. But it’s possible–theoretically, at least–to create a situation where supercooled water can never freeze. (Video and image credit: Minute Physics)

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  • Spores Get a Lift

    Spores Get a Lift

    Mushrooms have the challenging task of dispersing spores, typically from heights no more than a few centimeters above the ground. At that altitude, viscosity and friction with the ground mean that air barely moves, if it does at all. And mushrooms rely on a wide range of methods, from explosive launches to rain assistance to making their own weather. Every one of these methods gives spores a lift in altitude to reach higher winds and greater dispersal. (Image credit: A. Bejczi/CUPOTY; via Colossal)

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    Draining Topography is Hard

    At first glance, draining an ocean seems simple like a simple problem: just put a drain at the lowest point. But, as shown in this Minute Physics video, the problem is harder than it sounds because drainage depends not just on a point’s elevation but also on the path that leads to the drain. Fortunately, Henry has some clever methods for figuring out which areas would drain and how. (Video and image credit: Minute Physics)

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