Iceland’s Múlajökull glacier is prone to sudden surges, where rapid ice flow is interspersed between periods of quiescence or retreat. The isolated nature of the glacier and its marshy surroundings make approaching on foot almost impossible, but photographer Dani Guindo captured gorgeous aerial images of the glacier’s many rivulets ribboning about the landscape it’s carved. (Image credit: D. Guindo; via Colossal)
Most of what we know about Earth’s interior comes from observing how seismic waves–mostly from earthquakes–bounce around. As our observations have gotten better–more seisometers, better imaging techniques–scientists have identified two large anomalies sitting near the bottom of the mantle. Known as large low-velocity provinces, or LLVPs, these zones take up continent-sized areas beneath parts of Africa and the Pacific.
The LLVPs are hot, which would normally make them buoyant, but their stationary nature suggests they are made up of extremely dense material. Narrow plumes of hot material make their way up from the LLVPs to form volcanic hotspots like those that made the Hawaiian and Galapagos Islands. Balancing that upward convection is the downward convection of former tectonic material carried into the mantle at subduction zones.
What the LLVPs are made of remains an active research question. One suggestion is that they contain remnants of Theia, the planet thought to have impacted the proto-Earth to form our Moon. (Image credits: E. Garnero and C. Richardson; see also Physics Today)
Walter, a young African penguin at the New York Aquarium, loves soap bubbles. In fairness to Walter, so do most people I’ve met. There’s just something that feels a bit magical about these ephemeral rainbow spheres that pop at a (dry) touch.
Bubbles owe their colors to thin film interference–the colors actually indicate how thick the bubble film is–and their stability (and fast disintegration) to surface tension. With schlieren photography or flow visualization, watching bubbles gets even cooler. Do you suppose a penguin would appreciate bubbles popping at 50,000 fps? (Image credit: New York Aquarium; via PopSci)
The classic theory of steady wave motion predicts a phenomenon called Stokes drift, in which particles spread horizontally in the direction of wave travel. That means that something like microplastics will drift in the direction that waves are traveling. But in the real world, ocean waves aren’t quite so neat and unchanging. A new study looks at what happens when waves are decaying in strength–in other words, what happens in our world when the wind dies down.
In those circumstances, the researchers found that particles did not just drift horizontally–they drifted vertically, too. Further, how much a particle drifts vertically depends on its initial depth. Since plastics vary in their buoyancy–and can be found in varying numbers and sizes throughout the upper layer of the ocean–this mechanism could significantly affect how waves mix and transport pollution. (Image credit: N. Jensen; research credit: T. Izawa et al.; via Physics World)
NASA’s X-59 aircraft is intended to demonstrate supersonic flight without the boom. Although it’s broken into supersonic speeds, we haven’t yet heard its “sonic thump” because, so far, it’s been accompanied by conventional supersonic aircraft, which are louder.
The idea behind the long, skinny X-59 is to create weaker, widely-spaced shocks along the aircraft body. Weaker shocks are easier for atmospheric effects to damp out before they reach the ground, and spacing them out makes it harder for them to “pile up” at the nose and tail to create the strong double shocks that merge into a sonic boom.
NASA is preparing to test the X-59’s in-flight shocks soon, including with in-air schlieren photography like they’ve done in the past for other aircraft. But we’ve already have a glimpse of what to expect, thanks to wind tunnel testing, shown above. Ignore the three dark diagonal lines in the middle of the image (those are from the wind tunnel, not the model aircraft), and focus instead on the thin bright lines coming off the plane. Those are some impressively subtle shock waves!
Hear more from the aircraft’s designer and test pilots in this Ars Technica article. (Image credit: NASA; see also: Ars Technica, M. Ahaus et al.)
Life in Venice Beach lends itself to wave-watching, or so it seems for photographer Craig Hubbard. His portraits of waves and surfers are ethereal, every swell capped by a cloud-like swath of spray. Somehow, every photographer seems to capture breaking waves a little differently! (Image credit: C. Hubbard; via Colossal)
A telescope’s resolution is set by the size of its reflective surface. Our largest space telescope, JWST, has a 6.5-meter reflector, the largest we could manage given manufacturing constraints and the need to launch it in a rocket. To reach even larger sizes, researchers are considering a new type of reflector: one made of liquid.
A fluidic telescope has some obvious advantages: surface tension makes it atomically smooth, and liquids can be packed into any convenient shape for launch. But there are challenges, also. Like, what happens to the reflector when you point it in an new direction?
That’s what this study looks at, mathematically. Using a mathematical model of a 50-meter-wide, millimeter-thick fluid, the researchers analyzed how different maneuvers over the telescope’s lifetime would affect the image quality.
Shifting the reflector creates perturbations in the surface, initially at the mirror’s edges. Over time, those perturbations move toward the center of the mirror and, at the same time, decay. The team found that, while typical space telescope operations distorted parts of the mirror beyond the limits of good optical quality, the inner 80% of the mirror could remain undisturbed for twenty or more years. That would be like having a 40-meter telescope in orbit with more than 6x the resolution of JWST. (Image credit: NASA; research credit: I. Gabay et al.)
In cold weather, a new geological feature has shown up at Utah’s Great Salt Lake in the last decade. These salty mirabilite mounds form terraced crystals that resemble Yellowstone’s Mammoth Hot Springs.
Mirabilite is hydrated sodium sulfate (as opposed to the sodium chloride of table salt). The structures form when upwelling spring water partially dissolves the layer of mirabilite found beneath the lake bed. That sulfate-laden water rises to the surface, where it freezes into the crystals seen here.
When temperatures rise above freezing, the water in the mirabilite evaporates, leaving behind white, powdery thenardite. (Video credit: Great Salt Lake Institute; image credit: Utah Geological Survey)
In nature, droplets and fibers can meet on a spider’s web, on fur, or on a dew-gathering cactus. Here, researchers explore what happens when the droplet can dissolve the fiber it’s suspended on. As the authors note, a lumberjack who cuts the branch they sit on makes a fatal choice. The droplet sees a different outcome.
As the droplet hangs on the fiber, it dissolves the fiber’s sugar. Dense, sugar-laden water flows downward along the fiber and a replenishing upward flow goes along the droplet’s exterior. Because the sugar concentration is lower near the top of the drop, the fiber thins most quickly there.
The droplet has capillary forces along its top and bottom, where it meets the fiber. At the top, the droplet is free to expand, wetting more fiber, but the bottom of the drop is pinned to the fiber. The excess capillary force there goes into compressing the fiber.
As soon as the fiber breaks, the capillary force is no longer balanced, and the droplet jumps upward. If the drop and fiber are sized just right, the drop will jump upward enough to stay attached to the fiber instead of falling off. (Image and research credit: S. Dorbolo et al.)
In the early twentieth century, Los Angeles had capital and political willpower, but not water. So it built an engineering marvel, the LA Aquaduct, to guide water from the Sierra Nevadas down to the growing city. Grady gets into the literal (and figurative) ups and downs of the project in this Practical Engineering video.
Although the engineering prowess of the aquaduct system is impressive, as Grady points out, the LA Aquaduct’s story is much more complicated than the engineering needed to move water between two points. It’s a story where greed, corruption, politics, cultural impact, environment effects, and climate change all intersect. (Video and image credit: Practical Engineering)