FYFD

Category: Phenomena

  • The Livers of Our Rivers

    The Livers of Our Rivers

    To the naked eye, mussels and other bivalves don’t appear to be doing much. But these filter feeders are hard at work. The mussel takes in water through its incurrent siphon (on the right side in this image), and tiny cilia move the water through its gills, which filter out plankton and other edibles. Wastewater flows out the exacurrent siphon, seen here as the plume coming out the top of the mussel.

    Mussel species are important indicators of the health of both fresh and marine water bodies. Because they’re stationary and they are constantly processing the water, the health of these bivalves is indicative of the ecosystem’s overall health. (Image credit: S. Allen, source)

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    The Actual Shape of Raindrops

    If you imagine the shape of a raindrop, you probably think of a tear drop shape, but the reality of rain is much more complicated. It’s Okay to Be Smart has a great primer on the subject that takes a look at the forces on a raindrop and shows you the actual shape they take, which depends largely on their size.

    Small raindrops tend to coalesce together over time and get larger and progressively flatter. When the drop’s volume gets too large (below), it balloons up like a parachute. Researchers call this a bag. Stretched into a film, the drop’s surface tension is no longer able to win its fight against aerodynamic forces, and the drop shreds into smaller droplets. (Video and image credit: It’s Okay to Be Smart)

  • Kelly Slater’s Surf Ranch

    Kelly Slater’s Surf Ranch

    Many of us who grew up visiting water parks instead of ocean beaches have spent time bobbing in a wave pool. They’ve been around for decades. But a new generation of wave pools are aiming for a different goal: the perfect surf wave. One of the foremost current facilities is Kelly Slater’s Surf Ranch, shown above. Here a hydrofoil (draped in blue tarps on the left) is pulled along an artificial lagoon to create dozens of wave profiles, all engineered to give surfers a long ride on the perfect solitary wave.

    Other facilities, like the surf ranch used by USA Surfing in Waco, Texas, design their waves with different goals in mind. The Waco wave pool uses air pressure to drive their waves, and aims for a larger quantity of shorter waves. They’re designed to help young surfers practice skills they’re working on, and to give them a place where they can experience waves like those they’ll face in the upcoming 2020 Olympics in Tokyo. (Image credit: R. Young/WIRED; CNet, source; submitted by Lionel V.)

  • Exploding Meteors

    Exploding Meteors

    During the recent Perseid shower, photographer Petr Horálek caught an awesome timelapse of an exploding meteor and the vortex ring it created. This is a type of persistent train left when meteors pass through the upper atmosphere. The exact physics are not well understood because such events are difficult to observe; catching them at all is basically just happenstance. But one interpretation is that we’re seeing trails of plasma left by the ionization of parts of the meteor. When the meteor hits the upper atmosphere, there’s an extremely strong hypersonic shock wave. The jump in temperature across that shock wave is enough to pull atoms apart, creating a plasma. The train left by this meteor’s demise was faintly visible even an hour after the fireball. (Image credit: P. Horálek, video version; via APOD; submitted by Andrea S.)

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    The Show in the Sky

    There is a constant drama playing out overhead, though most of us do not take the time to watch. Fortunately, a few, like Blaž Šter, do and make timelapse videos that allow us to enjoy hours of atmospheric drama in only a few minutes. This timelapse shows a cloudy and rainy mid-July day in Slovenia, where an unstable atmosphere leads to turbulent and dramatic clouds. In an unstable atmosphere, it’s easier for vertical motion to take place between altitudes. For example, a parcel of warm air displaced upward will continue to rise because it will be lighter and more buoyant than the surrounding air. This is key to the strong convection that can generate thunderstorms. (Image and video credit: B. Šter, source)

  • Foam and Flow

    Foam and Flow

    Fluid dynamics often play out on a scale that’s difficult to appreciate from our earthbound perspective, but fortunately, we have tools to aid us. This natural-color satellite image shows Rupert Bay in Quebec, where fresh water stained with sediments and organic matter (right) flows into the saltier water of James Bay (left). White filaments at the edges of these mixing regions are likely foam floating atop the water. The turbulence caused at the intersection of the two bodies of water whips up organic films to form bubbles. The white on the far left of the image is ice chunks still floating in James Bay when the image was taken in early June. Click through to admire the high-resolution version. (Image credit: U.S. Geological Survey; via NASA Earth Observatory)

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    From Firenado to Water Spout

    Just a few years ago, fire tornadoes were almost fabled because they were so rarely captured on video. Now, with worsening wildfire seasons and cell phone cameras everywhere, there are new videos all the time. This video captures a fire tornado that sets off a water spout as it reaches the river (~1:15 in).

    Neither the fire tornado or the water spout is truly tornadic; instead they are more like dust devils. They are driven by the rising heat of the fire. As cooler, ambient air flows inward to replace the rising air, it brings with it any vorticity it had. And, like an ice skater, the incoming air spins faster as it moves inward. This sets up both the fire tornado and the water spout’s vortices.

    Although this is the first example I’ve seen video of, fire tornadoes have been known to create water spouts before. Lava flowing into the ocean can create whole trains of them. (Video credit: C. & A. Mackie; via Jean H.)

  • Different Kinds of Boiling

    Different Kinds of Boiling

    When you put a pot of water on to boil, you probably don’t give much thought to the process. In our daily lives, we pretty much only see one kind of boiling: the sort where lots of small bubbles form on a hot surface and then rise. That’s nucleate boiling (top image), and it’s typical when you have a surface close to the boiling point of a liquid. 

    But when you continue raising the temperature of the surface, you get a transition to a different boiling regime (middle image). In this final regime (bottom image), a film of vapor envelopes the heated surface; hence its name: film boiling. Because vapor is less efficient for heat transfer than a liquid, a surface undergoing film boiling can become much, much hotter because it cannot transfer its heat away efficiently. In this experiment, the tube starts at 375K during nucleate boiling and rises to a temperature nearly three times higher during film boiling. (Image credit: TSL, source)

  • Visualizing Aerosols

    Visualizing Aerosols

    Aerosols, micron-sized particles suspended in the atmosphere, impact our weather and air quality. This visualization shows several varieties of aerosol as measured August 23rd, 2018 by satellite. The blue streaks are sea salt suspended in the air; the brightest highlights show three tropical cyclones in the Pacific. Purple marks dust. Strong winds across the Sahara Desert send large plumes of dust wafting eastward. Finally, the red areas show black carbon emissions. Raging wildfires across western North America are releasing large amounts of carbon, but vehicle and factory emissions are also significant sources. (Image credit: NASA; via Katherine G.)

  • Antibubbles

    Antibubbles

    Antibubbles are peculiar and ephemeral creations. A bubble typically encloses a gas within a thin layer of fluid. As the name suggests, an antibubble does the opposite: it’s a thin film of gas enclosing a liquid droplet within a larger background liquid. That thin gas film makes antibubbles extremely delicate. Disturb it at all – as the thinning jet at the top of the animation above does – and that film will break apart, much like a soap bubble. To see more antibubble action, check out some of our previous entries, including antibubbles in a vortex and a simple way to create antibubbles.  (Image credit: C. Kalelkar and S. Phansalkar, source)