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Murmuration

Photo credit - SteveMcN - cc-by-nc-nd

Photo credit – SteveMcN – cc-by-nc-nd

In my posts on collective nouns, parts one and two, I had many examples for birds and humans and other animals. Even plants were represented. I could have gone on and on, listing existing collective nouns and inventing my own, but I stopped myself. I wanted the posts to be brief, both to prevent boredom and to encourage readers to explore further. Naturally, this meant that many good examples were left out. This post is about one of those.

Photo credit - adam - cc-by

Photo credit – adam – cc-by

Starlings have numerous collective nouns attached to them, including a chattering, a clattering, a cloud and a congregation, but the one I favor is a murmuration. When starlings are flocking and swooping around in the sky, that’s murmuration.

Photo credit - vytauto - public domain

Photo credit – vytauto – public domain

How do all the birds in a murmuration maintain such coordinated flight? They keep it simple: avoid collisions. Each bird keeps a minimum distance, on the scale of its wingspan, from its immediate neighbors. Analysis of high-speed video reveals that each bird keeps track of six or seven others. Why do they do it? The practical purpose is to evade and confuse predators, such as falcons. But when they’re doing it just before roosting for the night, I think they’re doing it for fun. Starlings are highly social birds. Activities like murmuration can contribute to social bonding.

Photo credit - don macauley - cc-by-sa

Photo credit – don macauley – cc-by-sa

Here’s a nice video of murmuration. Here’s another, with narration. Listen to them murmur.

rjb

  
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Irisation

Photo credit - gquiroga - cc-by-sa

Photo credit – gquiroga – cc-by-sa

Cloud of the Day – Irisation

A close relative of corona is irisation. Both are caused by interference among light waves diffracted by cloud particles. Since different wavelengths of light are scattered at different angles, they interfere with themselves at different distances from the light source. This causes the colors to be separated out, creating the beautiful iridescent irisation. The differential scattering of wavelengths, shorter being more easily scattered, also leads to blue skies, as much of the short wavelength blue in sunlight is scattered, and red sunsets, as more long wavelength red light makes it through.

Photo credit - Guillaume Piolle - cc-by

Photo credit – Guillaume Piolle – cc-by

Irisation is the name of the meteorological phenomenon, and it’s caused by iridescence. Both words have their root in the Greek word iris, or rainbow, derived from the Greek god(dess) of the rainbow: Iris. Iridescence can be found in soap bubbles, bird feathers and seashells. In the case of irisation, it’s found in the clouds.

Image credit - hermitage museum - public domain

Image credit – hermitage museum – public domain

Photo credit - Tagishsimon - cc-by-sa

Photo credit – Tagishsimon – cc-by-sa

Photo credit - Jörg Hempel - cc-by-sa

Photo credit – Jörg Hempel – cc-by-sa

Since it occurs so close to the Sun, irisation is often lost in the glare. You can improve your chances of seeing it by wearing sunglasses, or by physically blocking out the Sun. It occurs in many different types of clouds, generally in the middle and high etages. Any time you see bright white clouds close to the Sun, you have a good chance of seeing it.

Photo credit - Fir0002 - Flagstaffotos - cc-by-nc

Photo credit – Fir0002 – Flagstaffotos – cc-by-nc

Irisation is not reliably predictive of weather.

Note: All pictures link to their larger originals.

rjb

  
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Spring-Summer

moon-silhouette-jeremy-cook

Here is a selection of pictures taken by members of the Oliver Photo Club. The banner at the top of this post is from a picture taken by Jeremy Cook, taken at the time of the so-called SuperMoon. The next two are two views of the same sunset, taken in sagebrush country. The photographers are Jeremy Cook again, and Brandt Leinor. All photos are available in full size by clicking.

sagesunset-jeremy-cook

sagesunset2-brandt-leinor

A few kilometers north of my small town is another small town, which enjoys the benefits of a fair-sized lake. That community has re-purposed an old train trestle into an attraction for tourists and sight-seers. Brandt Leinor has captured it beautifully in the photo below.

okfalls-brandt-leinor

Finally, the rustic charm of my little town, preserved for your enjoyment in this great shot by Paul Eby.

laneway-paul-eby

Happy to share my blessings with you.

rjb

  
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Corona

Corona diagram

Corona diagram

All images, except where noted, credit Wiebke Salzmann CC-BY-SA. Click images for larger versions.

Cloud of the Day – Corona

Here is a meteorological phenomenon that is often misnamed “halo.” A corona is similar to a halo in that they both form rings around the Sun and Moon. The Sun’s corona (the one formed in Earth’s atmosphere, not the one around the actual Sun) is hard to see because the Sun is so bright. A corona is a more subtle effect and needs the more muted light of the Moon to really show itself.

Corona-bright-Wiebke-Salzmann-cc-by-saWhile haloes result from the light being refracted by ice crystals high in the atmosphere, coronae are caused by the diffraction of light scattered by particles – water droplets, ice crystals, dust motes, etc – in the lower atmosphere. A corona can also form on a foggy window pane. Haloes have fixed dimensions, calculable from the known refractive index of ice. Coronae come in various sizes due to the variability in the size of the light-scattering particles. Smaller droplets make larger coronae. In addition to the light scattered from the surface of the particle, small contributions to the corona are made by light that reflects directly off the droplet, or passes through it.

Corona around street lamps through an aspirated window pane.

Corona around street lamp through an aspirated window pane.

Artificial corona around LED lamps of different colors, created with lycopodium spores. As can be seen the diffraction rings of red light have a greater radius than those of blue light.

Artificial corona around LED lamps of different colors, created with lycopodium spores. As can be seen the diffraction rings of red light have a greater radius than those of blue light.

Image credit - Florian Marquardt - CC-BY-SA

Interference patterns – Florian Marquardt – CC-BY-SA

A classic corona consists of a bright aureole in the center, with one or more colorful rings around it. For the sharpest coronae, the droplets must be all close to the same size, so the interference pattern in the light can be well defined. It is constructive and destructive interference among the scattered light waves, where they add to make bright regions and subtract to make dark regions, that make the alternating rings of bright and dark.

rjb

  
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Pery Burge

Photo credit - Pery Burge - click for larger image

Photo credit – Pery Burge – click for larger image

Pery Burge died in 2013, but she left behind a collection of beautiful photographs. Asked how she generated her photographs, Pery Burge said, “I place ink in water, which I photograph . . .” Trust me, there’s a lot more to it than that. In her Artist’s Statement, she said, “In 2011, I began to work with glass and light . . .” That series of photos she called “Lightscapes.” She also has a series called “Smoke.” There’s a series called “Lab Images,” one called “Bubblespreads,” and one containing her personal selections, and many more besides. Finally, you can see tons of her photos on her flickr photostream.

Her website, “Chronoscapes,” has a final journal entry entitled “Pery Burge,” written by a friend shortly after her death. In a sad irony, her own final entry was entitled “Looking Forward to 2013.”

Pery Burge died too young, but she left beauty behind.

rjb

  
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