A Movie Showing The Dynamics Of The Inner Part Of The Crab Nebula Made Using The Chandra X-ray Observatory.

Photograph of the May 1919 solar eclipse captured by Arthur Eddington, which proved Einstein’s theory of general relativity. 

Credit: SSPL/Getty Images

Magnetic Field Viewer

Fluorite

Locality:  Okorusu mine, Otjiwarongo District, Namibia

Swirling swarms of bacteria offer insights on turbulence

In the bacterial world, as in the larger one, beauty can be fleeting. When swimming together with just the right amount of vigor, masses of bacterial cells produce whirling, hypnotic patterns. Too much vigor, however, and they descend into chaotic turbulence.

A team of physicists led by Rockefeller University fellow Tyler Shendruk recently detected a telling mathematical signature inscribed in that disintegration from order to chaos. Their discovery, described May 16 in Nature Communications, provides the first concrete link between turbulence in a biological system and within the larger physical world, where it is best known for buffeting planes and boats.

Amin Doostmohammadi, Tyler N. Shendruk, Kristian Thijssen, Julia M. Yeomans. Onset of meso-scale turbulence in active nematics. Nature Communications, 2017; 8: 15326 DOI: 10.1038/NCOMMS15326

When swimming together, bacteria produce swirling patterns that can disintegrate into turbulence as they speed up. Credit: Kristian Thijssen

Tesla at work. (via Reddit)

Many solids can dissolve in liquids like water, and while this is often treated as a matter of chemistry, fluid dynamics can play a role as well. As seen in this video by Beauty of Science, the dissolving candy coating of an M&M spreads outward from the candy. This is likely surface-tension-driven; as the coating dissolves, it changes the surface tension near the candy and flow starts moving away thanks to the Marangoni effect. With multiple candies dissolving near one another, these outward flows interfere and create more complex flow patterns. 

These flows directly affect the dissolving process by altering flow near the candy surface, which may increase the rate of dissolution by scouring away loose coating. They can also change the concentration of dissolved coating in different areas, which then feeds back to the flow by changing the surface tension gradient. (Video and image credit: Beauty of Science)

Watching the clouds go by on #Mars. Check out these atmospheric ripples!

Layer Drawing Forest, Nobuhiro Nakanishi, 2008.

“Ratio of oscillations.”  La méthode graphique dans les sciences expérimentales et principalement en physiologie et en médecine. 1885.