APOD: Ripples Through a Dark Sky (2016 Jul 30)

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APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by APOD Robot » Sat Jul 30, 2016 4:07 am

Image Ripples Through a Dark Sky

Explanation: Sunlight ripples through a dark sky on this Swedish summer midnight as noctilucent or night shining clouds seem to imitate the river below. In fact, the seasonal clouds often appear at high latitudes in corresponding summer months. Also known as polar mesospheric clouds, they form as water vapor is driven into the cold upper atmosphere. Fine dust supplied by disintegrating meteors or volcanic ash provides sites where water vapor can condense, turning to ice at the cold temperatures in the mesosphere. Poised at the edge of space some 80 kilometers above, these icy clouds really do reflect sunlight toward the ground. They are visible here even though the Sun itself was below the horizon, as seen on July 16 from Sweden's Färnebofjärdens National Park.

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Ann
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by Ann » Sat Jul 30, 2016 6:18 am

That's a lovely image. Noctilucent clouds are so beautiful. It's a pity I've seen so little of them this summer.

The rippling sky seems to echo the rippling river, or is it the other way round? Presumably the biggest difference between the two kinds of ripples is their size, with the sky ripples probably being orders of magnitudes larger than the aquatic ones.

I'm reminded of the Mandelbrot fractals, where similar shapes repeat over and over again, even though their sizes become smaller and smaller.
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by Asterhole » Sat Jul 30, 2016 12:02 pm

Not exactly an astronomy subject matter here, but yes, quite a beautiful scene.
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by neufer » Sat Jul 30, 2016 12:46 pm

Asterhole wrote:
Not exactly an astronomy subject matter here, but yes, quite a beautiful scene.
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by macdude » Sat Jul 30, 2016 12:50 pm

Does APOD mean "Artistic Picture Of The Day"? enough of the cloud pictures already!

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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by neufer » Sat Jul 30, 2016 1:44 pm

grisham6@live.com wrote:
The picture of the day Ripples Though The Dark Sky , has a lasting affect an the person who is a viewer.

But the real Question? Just where does these feelings come from?
https://en.wikipedia.org/wiki/Evolutionary_aesthetics wrote:
<<Evolutionary aesthetics refers to evolutionary psychology theories in which the basic aesthetic preferences of Homo sapiens are argued to have evolved in order to enhance survival and reproductive success.

An important choice for a mobile organism is selecting a good habitat to live in. Humans are argued to have strong aesthetical preferences for landscapes which were good habitats in the ancestral environment. When young human children from different nations are asked to select which landscape they prefer, from a selection of standardized landscape photographs, there is a strong preference for savannas with trees. The East African savanna is the ancestral environment in which much of human evolution is argued to have taken place. There is also a preference for landscapes with water, with both open and wooded areas, with trees with branches at a suitable height for climbing and taking foods, with features encouraging exploration such as a path or river curving out of view, with seen or implied game animals, and with some clouds.

A survey of art preferences in many different nations found that realistic painting was preferred. Favorite features were water, trees as well as other plants, humans (in particular beautiful women, children, and well-known historical figures), and animals (in particular both wild and domestic large animals). Blue, followed by green, was the favorite color.>>
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by Chris Peterson » Sat Jul 30, 2016 2:00 pm

Asterhole wrote:Not exactly an astronomy subject matter here, but yes, quite a beautiful scene.
A visible manifestation of interplanetary dust striking Earth's atmosphere. That's pretty astronomical.
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by paulcordinglymorgan@gmail.com » Sun Jul 31, 2016 5:09 am

Lovely picture. Did find the commentary confusing. Is the sun below the horizon from the viewpoint of those clouds? If the sun is below the horizon only from the camera's viewpoint, the sun reflecting off the clouds is not so remarkable.

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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by geckzilla » Sun Jul 31, 2016 5:12 am

paulcordinglymorgan@gmail.com wrote:Lovely picture. Did find the commentary confusing. Is the sun below the horizon from the viewpoint of those clouds? If the sun is below the horizon only from the camera's viewpoint, the sun reflecting off the clouds is not so remarkable.
You are correct. It is the height of them within the atmosphere that is remarkable. That the sun illuminates them is only evidence of their altitude.
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by neufer » Sun Jul 31, 2016 9:04 pm

geckzilla wrote:
paulcordinglymorgan@gmail.com wrote:
Is the sun below the horizon from the viewpoint of those clouds? If the sun is below the horizon only from the camera's viewpoint, the sun reflecting off the clouds is not so remarkable.
It is the height of them within the atmosphere that is remarkable. That the sun illuminates them is only evidence of their altitude.
One could also use parallax:
https://en.wikipedia.org/wiki/Tycho_Brahe wrote:
<<Tycho Brahe's precise measurements indicated that "new stars" (now known as supernovae), in particular that of 1572, lacked the parallax expected in sublunar phenomena and were therefore not tailless comets in the atmosphere as previously believed but were above the atmosphere and beyond the moon. Using similar measurements he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposedly immutable celestial spheres.>>
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Re: APOD: Ripples Through a Dark Sky (2016 Jul 30)

Post by neufer » Sun Jul 31, 2016 10:57 pm

Chris Peterson wrote:
Asterhole wrote:
Not exactly an astronomy subject matter here, but yes, quite a beautiful scene.
A visible manifestation of interplanetary dust striking Earth's atmosphere. That's pretty astronomical.
https://en.wikipedia.org/wiki/Noctilucent_cloud wrote:
<<Noctilucent/mesospheric clouds require water vapour, dust, and very cold temperatures to form. The sources of both the dust and the water vapour in the upper atmosphere are not known with certainty. The dust is believed to come from micrometeors, although particulates from volcanoes and dust from the troposphere are also possibilities. The moisture could be lifted through gaps in the tropopause, as well as forming from the reaction of methane with hydroxyl radicals in the stratosphere.

The exhaust from Space Shuttles, which was almost entirely water vapour after the detachment of the Solid Rocket Booster at a height of about 46 km, was found to generate minuscule individual clouds. About half of the vapour was released into the thermosphere, usually at altitudes of 103 to 114 km. In August 2014, a SpaceX Falcon 9 also caused noctilucent clouds over Orlando, FL after a launch.>>
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