Zheng Lu’s stainless steel sculptures capture elaborate splashes in action. In some of the pieces, thousands of Chinese characters cover the sculpture’s surface; these are quotes from historical texts and poems, an homage to early Chinese philosophers who studied the principles of the natural world. See more examples of the artist’s work here. (Image credit: Z. Lu; via Colossal)
Few volcanoes are as well-studied as those of the Big Island of Hawai’i. With a host of seismic monitors and frequent eruptions, scientists know the near-surface region of Hawai’i well. But a recent study looked at nearly 200,000 seismic events after the 2018 collapse of Kilauea’s crater and found hints of what goes on much deeper.
Mapping out earthquakes beneath the island revealed a cluster of activity near a village named Pahala. These earthquakes took place 36 to 43 kilometers below the surface and seem to be connected to magma filling a sill complex there. From that deep reservoir, the team was also able to map seismic activity leading upwards to both Kilauea and Mauna Loa volcanoes. Despite the 34 kilometers between those two volcanoes, they appear to be fed through the same web of magma! (Image credit: top – USGS, illustration – J. Wilding et al.; research credit: J. Wilding et al.; via Physics Today)
Blooms of the algae Karenia brevis — known as a red tide — bring havoc to Gulf Coast shores. The algae can kill fish and other marine life, and it causes skin irritation and even respiratory problems for humans. But in spite of the moniker, these algae can be hard to spot; they can add a green, brown, red, or black hue to the water.
The false-color image above uses a new image processing technique that reveals the bloom. Using satellite images taken over multiple days, scientists can track and study the red tide in unprecedented detail. The new technique will be a boon to those trying to monitor and understand red tides. (Image credit: Y. Yao/USF/Planet Labs/L. Dauphin; via NASA Earth Observatory)
Seals and sea lions often hunt fish in waters too dark or turbid to rely on eyesight. Instead, they follow their whiskers, using the turbulence generated by a fish’s wake. The vortices shed by the fish cause the seal’s whiskers to vibrate, giving them sensory information. To better understand what a seal can derive from this, a recent experiment looked at what a thin whisker can pick up from an upstream cylinder.
As expected, the strength of the whisker’s vibration fell off the farther away the cylinder was. But the researchers found that, if they moved the cylinder quickly — like a fish trying to dart away — the vibration of the whisker was stronger. They also found that the whisker was sensitive to misalignment. If the cylinder was placed ahead and to the side of the whisker, the whisker would still vibrate but would do so around a different equilibrium position. That result implies that a seal can get information both about the fish’s speed and direction, simply from the twitch of its whiskers. (Image credit: seal – K. Luke, illustration – P. Gong et al.; research credit: P. Gong et al.; via APS Physics)
Drying fluids can leave behind all kinds of fascinating patterns, as we’ve seen before with whiskey, coffee, and even blood. Here researchers study patterns left behind by lipids, dyes, and other fluids. They place their mixture in a rotating flask kept in a warm bath. For a few hours, the fluids mix, chemically react, and evaporate. The complex interactions that take place in that time leave behind fascinating, rune-like patterns, seen here under a microscope. It’s a bit like looking at photos of Martian landscapes! (Image credit: M. Murali and L. Shen)
Frogs and toads shoot out their tongues to capture and envelop their prey in a fraction of a second. They owe their success in this area to two features: the squishiness of their tongues and the stickiness of their saliva. The super squishy toad tongue deforms to touch as much of the insect as possible. That shape-changing helps deliver the saliva, which is an impressively fast-acting, shear-thinning fluid. Under normal circumstances, the saliva is sticky and about as viscous as honey. But the shear from the tongue’s impact makes the saliva flow like water, spreading across the insect’s body. Then it morphs back into its viscous, sticky self, providing enough adhesive power that the insect can’t escape the toad pulling its tongue back in. (Video credit: Deep Look/KQED; research credit: A. Noel et al.)
For many microswimmers, like bacteria or spermatozoa, swimming through common fluids is like moving through mud. Unless they can produce enough thrust to overcome a fluid’s yield-stress, they are effectively stuck in a solid. A recent study breaks down exactly what a microswimmer has to manage, assuming they use a helical, corkscrew-like tail for propulsion.
The first barrier is creating enough force to be able to rotate in the fluid, but that alone is not enough to ensure forward motion. Once rotating, the swimmer’s thrust has to be large enough to deform the fluid around it. Without that, the swimmer is stuck. And, finally, once they’re moving, the swimmer’s tail pitch determines how fast they can move and whether the fluid’s characteristics slow it down.
The researchers hope their work can shed light on propulsion for bacteria in the body, as well as larger creatures like burrowing earthworms and fruit-invading parasites. (Image credit: SwedishStockPhotos; research credit: F. Nazari et al.; via APS Physics)
Tomorrow mathematician Luis Caffarelli will receive the Abel Prize — one of the highest honors in mathematics — in part for his work in fluid dynamics. Caffarelli is one of the authors of a partial proof of regularity for the Navier-Stokes equations, the equations governing fluid motion. A full proof of regularity and smoothness — essentially showing that the equations never break down or blow up to infinity — is one of the open Millennium Problems. Caffarelli is the first mathematician born and educated in South America to receive the Abel Prize. Congratulations to Professor Caffarelli! (Image credit: N. Zunk/University of Texas at Austin; via Nature; submitted by Kam-Yung Soh)
Built from approximately 90,000 individual images, “Fusion of Helios” reveals the wisp-like corona of our Sun. Astrophotographers Andrew McCarthy and Jason Guenzel joined forces to combine eclipse images with data from NASA to build this fusion of art and science. Jets of plasma, known as spicules, dot the sun’s surface, and a towering tornado of plasma shoots off one side. For scale, that vortex stretches as far as 14 Earths stacked atop one another. (Image credit: A. McCarthy and J. Guenzel; via Colossal)
Acoustic cameras use arrays of microphones to isolate where sounds are coming from. As Steve Mould shows in this video, they have some incredibly cool properties. They can show engineers which part of a device is producing particular sound frequencies, which is handy, for example, when trying to quiet a vacuum cleaner or learn which wheels on a train need maintenance. They can also show how sound moves around a room; near the end of the video, you can see the echo from a clap flashing around a room. Check out the full video for more! (Video credit: S. Mould)