Unusual Fluid Behavior Observed In Microgravity

cube

~ wikimedia commons

Robert Irwin @ Art Basel 2015

Black 3, 2008

via

TRAPPIST-1 Planets - Flyaround Animation

Credit: NASA/Spitzer

Hexagons and rhombis spreading out

Sentinels of the Arctic http://go.nasa.gov/2n1ynuo

Mutation by Ben Butler 30″ x 32″ x 16″, cedar, 2006

Heartwood on Tumblr

Samuel W. Hall. Corona of an Eclipse, Moon Hiding Lower and Upper Limb of Sun, Eclipse of the Sun, Moon Hiding Upper and Lower Limb of Sun, Comparative Size of the Planets, Size of the Sun, Elliptical Orbit. Sunshine and Moonlight; with; also, a Flash of Comets, Meteors and Shooting Stars, and a Twinkle of Starlight. 1889.  Contd from here

In this short film, the Macro Room team plays with the diffusion of ink in water and its interaction with various shapes. Injecting ink with a syringe results in a beautiful, billowing turbulent plume. By fiddling with the playback time, the video really highlights some of the neat instabilities the ink goes through before it mixes. Note how the yellow ink at 1:12 breaks into jellyfish-like shapes with tentacles that sprout more ink; that’s a classic form of the Rayleigh-Taylor instability, driven by the higher density ink sinking through the lower density water. Ink’s higher density is what drives the ink-falls flowing down the flowers in the final segment, too. Definitely take a couple minutes to watch the full video. (Image and video credit: Macro Room; via James H./Flow Vis)

Substances don’t have to be a liquid or a gas to behave like a fluid. Swarms of fire ants display viscoelastic properties, meaning they can act like both a liquid and a solid. Like a spring, a ball of fire ants is elastic, bouncing back after being squished (top image). But the group can also act like a viscous liquid. A ball of ants can flow and diffuse outward (middle image). The ants are excellent at linking with one another, which allows them to survive floods by forming rafts and to escape containers by building towers. 

Researchers found the key characteristic is that ants will only maintain links with nearby ants as long as they themselves experience no more than 3 times their own weight in load. In practice, the ants can easily withstand 100 times that load without injury, but that lower threshold describes the transition point between ants as a solid and ants as a fluid. If an ant in a structure is loaded with more force, he’ll let go of his neighbors and start moving around.

When they’re linked, the fire ants are close enough together to be water-repellent. Even if an ant raft gets submerged (bottom image), the space between ants is small enough that water can’t get in and the air around them can’t get out. This coats the submerged ants in their own little bubble, which the ants use to breathe while they float out a flood. For more, check out the video below and the full (fun and readable!) research paper linked in the credits. (Video and image credits: Vox/Georgia Tech; research credit: S. Phonekeo et al., pdf; submitted by Joyce S., Rebecca S., and possibly others)