Iridescent clouds shine bright over this Finnish sunset. These colorful clouds are nacreous clouds, also known as mother-of-pearl clouds. Formed from ice crystals during frigid conditions in the lower stratosphere, these clouds are most visible before dawn and after sunset, when their high altitude catches sunlight while the lower atmosphere doesn’t. These rare clouds form mostly in high latitudes during winter. While they appear similar to other iridescent clouds that occur all over the world, nacreous clouds are far brighter and more vivid. (Image credit: D. Lehtonen; via APOD)
Tag: iridescence
Soap Bubbles Up Close
Watching soap bubbles up close is endlessly fascinating. The iridescent colors reflect the soap filmâs thickness, or, in the case of black spots, its lack thereof. The dancing of the colors shows the soap filmâs flow and the ever-shifting balance of surface tension necessary to keep the film intact. Even the junctures of the bubblesâso precise and mathematically perfect in structureâreflect the molecular interactions that govern them. (Video credit: Stereokroma; via R. Weston)
“Oil Spill”
In âOil Spillâ artist Fabian Oefner explores the shapes and colors of oil floating atop water. An old adage tells us that oil and water donât mix, but this is not perfectly true. Especially in low concentrations, oil can mix slightly with water, which is why the edges of Oefnerâs creations become fuzzy and break down. For the most part, though, the thin layer of oil spreads across the waterâs surface, its slight variations in thickness casting the different iridescent colors we observe â just the same as a soap bubbleâs iridescence. The colorful patterns are a snapshot of motion in the oil; in some places it radiates outward, pulled by the stronger surface tension of water. In other places it forms plumes and swirls that may be the result of temperature variations or other disquiet motion in the surrounding water or air.  (Image credits: F. Oefner)
Collapsing Soap Bubbles
The colors of a soap film are directly related to their thickness. If a film becomes thin enough (~10 nanometers), it appears black. (Hereâs why.) This video shows the thinning of a vertical soap film. Normally, this is a linear process, with gravity pulling the fluid downward and progressively thinning the film from top to bottom at a constant rate. At 0:20 a cold rod slowly contacts the film, adding a thermal driver for the filmâs thinning. Two large counter-rotating convection cells form underneath the rod, with weaker secondary vortices in the lower corners of the film. This drastically increases mixing in the film. Gradually small black spots, indicating very thin areas of the film, form and advect. Eventually these spots stretch, forming long tails. The thinning of the film kicks up to an exponential rate until the film becomes uniformly thin. (Video credit: M. Winkler et al.)
The Colors of Soap
The brilliant and beautiful colors of a bubble are directly related the the thickness of the soap film surrounding it. When light shines on the soap film, some rays are reflected from the upper surface of the film, while others are refracted through the film and reflect off its lower surface. These reflected rays have different phase shifts and their interference is what causes the colors we observe. The color patterns themselves reveal the interior flow of the soap film, in which gravity tries to thin the film and surface tension tries to distribute the film evenly. (Photo credit: R. Kelly, A. Fish, D. Schwichtenberg, N. Travers, G. Seese)
Soap Bubble Shapes
The shapes of soap bubbles are determined by surface tension, which ensures the smallest surface area for a given contained volume. (#) Their iridescent colors are created by the interference and refraction of light waves passing through the nonuniform thickness of the bubble, as well as to the motion of the soap mixture itself.
Photo credit: found via fuckyeaheyegasms, originally from teacupofmoons
