APOD: Sunset at the Spiral Jetty (2010 Dec 04)

[APOD Robot]

Sunset at the Spiral Jetty

Explanation: In dwindling twilight at an August day's end, these broad dark bands appeared in the sky for a moment, seen from Robert Smithson's Spiral Jetty on the eastern shore of Utah's Great Salt Lake. Outlined by rays of sunlight known as crepuscular rays, they are actually shadows cast by clouds near the distant western horizon, the setting Sun having disappeared from direct view behind them. The cloud shadows are parallel, but seem to converge in the distance because of perspective. Coiled in the salt-encrusted lake surface, Smithson's most famous earthwork provides a dramatic contrast to the converging lines. The Spiral Jetty was constructed in 1970, when the water level was unusually low and was completely submerged in a few years as the level rose. Now just above water again, it has spent much of its existence submerged in the briny lake.

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[judy]

clouds on the planet earth. that is nice. thank you.

[ssrcc]

Aren't these actually anticrepuscular rays?

[Star*Hopper]

ASTRONOMY:
Y'know, more & more I've come to think maybe my school-taught-&-long-held definition of 'astronomy' was & has been lo these many years, somehow amiss or outrightly erroneous. Curious; what do others say?

American Heritage Dictionary of the English Language:
1. The scientific study of matter in outer space, especially the positions, dimensions, distribution, motion, composition, energy, and evolution of celestial bodies and phenomena.
2. A system of knowledge or beliefs about celestial phenomena: the various astronomies of ancient civilizations.

Merriam-Webster Dictionary:
(noun) : the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties

GNU Webster's 1913:
The science which treats of the celestial bodies, of their magnitudes, motions, distances, periods of revolution, eclipses, constitution, physical condition, and of the causes of their various phenomena.

Dictionary.com:
noun
the science that deals with the material universe beyond the earth's atmosphere.

The American Heritage New Dictionary of Cultural Literacy:
The science that deals with the universe beyond the Earth. It describes the nature, position, and motion of the stars, planets, and other objects in the skies, and their relation to the Earth.

Harper-Collins World English Dictionary
The scientific study of the individual celestial bodies (excluding the earth) and of the universe as a whole.

Wiktionary
–noun
The study of the physical universe beyond the Earth's atmosphere, including the process of mapping locations and properties of the matter and radiation in the universe.

Century Dictionary:
The science which describes the heavenly bodies and explains their apparent motions, etc. That part of the science which gives a description of the motions, figures, periods of revolution, and other phenomena of the heavenly bodies is called descriptive astronomy; that part which teaches how to observe their motions, figures, periodical revolutions, distances, etc., and how to use the necessary instruments, is called practical astronomy; and that part which explains the causes of their motions, and demonstrates the laws by which those causes operate, is termed physical astronomy.
Several other branches of the science are recognized: gravitational astronomy or astronomical mechanics, replacing the term physical astronomy, which is now generally discarded because of the danger of confusion with astronomical physics or astrophysics; nautical astronomy, astronomy applied to navigation; sidereal astronomy, the branch of the science which deals with the stars; spheric astronomy, which treats of the apparent position and motions of bodies on the celestial sphere; theoretical astronomy, which deals with the calculation of orbits and perturbations. These various branches interlace in all directions.

And finally - the Urban Dictionary:
A scientific study for those who seek to understand the intricate ways of other worlds and galaxies because they’ve given up trying to fathom the ways of this one - buy astronomy mugs, tshirts and magnets

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Ummmmmm.....
Nope - pretty much as I understand it, too.

Luvly picture. But is it astronomy?
Just sayin'....
~S*H

[rstevenson]

I would describe (loosely, perhaps) the phenomenom shown in this APOD as celestial.Think of it the way ancient peoples would have, as a mysterious sky effect causing awe and wonder, and which would encourage them to try to understand what they see in the sky.

It's also possible to think of the Earth as a non-special place (except that it's home, of course.) It is a planet and understanding it helps us think about other planets just as understanding those other planets helps us think about Terra.

In short, enjoy the show and don't spend so much time examining dictionaries.

Rob

[owlice]

Aren't these actually anticrepuscular rays?

No. "these broad dark bands" are shadows, which, as they are "seen from Robert Smithson's Spiral Jetty on the eastern shore" are in the western sky; "the setting Sun" had just "disappeared from direct view behind them." So the rays are crepuscular. They'd have to be at the antisolar point to be anticrepuscular.

[owlice]

ASTRONOMY:
Y'know, more & more I've come to think maybe my school-taught-&-long-held definition of 'astronomy' was & has been lo these many years, somehow amiss or outrightly erroneous. Curious; what do others say?

What I say? Take Rob's advice!

[orin stepanek]

The sunset is fabulous! The spirals do nothing for me; but I they are art.

Click to view full size image

[dKlinkenberg@hvc.rr.com]

To the folks who bring us APOD,

I try to see APOD every day. When I miss a day or so, I usually go back to the archive and catch up. I've saved many of your pictures, including this one. (Its seldom that I save a picture taken by someone who's standing on this planet.)

The cloud shadows are parallel, but seem to converge in the distance because of perspective.

I disagree. The shadows are not parallel. They point directly at the sun. They converge at the sun. They point (below the horizon) to where the sun would "appear" to be. (They also do this, when the sun is above the horizon). Is there a

professional astronomer

or other person who can respond to me about this?

Sincerely,
Dan Klinkenberg

[bystander]

They are parallel (or very nearly so), they only appear to converge, in much the same way as railroad tracks appear to converge in the distance. It's just a matter of perspective.

http://en.wikipedia.org/wiki/Crepuscular_rays
http://www.atoptics.co.uk/atoptics/ray1.htm

[Céline Richard]

I love this spiral, with trees, inside a salt lake, at sunrise. At the beginning, i thought it was snow
Beautiful, really very beautiful

[smitty]

I'm puzzled by the surface of the jetty. Water, even briny water, typically isn't lumpy. So is the substance on the surface of the jetty snow? In August? If not snow, then what?

[owlice]

The surface of the jetty isn't water, but earth. http://www.diaart.org/sites/main/spiraljetty

[bystander]

So is the substance on the surface of the jetty snow? In August? If not snow, then what?

Salt.

[smitty]

Wow . . . that's a lot of salt!

[owlice]

It's a salt lake; the supply is plentiful!

[neufer]

It's a salt lake; the supply is plentiful!

Monsoonal Flooding in the Rann of Kutch (MODIS)

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Rann of Kutch on the top left in turquoise colour. The Gulf of Kutch is further down below the Kutch region. Image:NASA Earth Observatory

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<<The heavy rains of India’s summer monsoon drenched the land, filling lakes and rivers. These Moderate Resolution Imaging Spectroradiometer (MODIS) images contrast the wet and the dry seasons in the Rann of Kutch in northwestern India. The top image, captured by NASA’s Aqua satellite on October 3, 2003, shows vast regions of standing water over what is otherwise desert land, as can be seen in the bottom image taken on May 10, 2003. September 30 marked the end of the monsoon season, which runs from July through September. Normally a salt clay desert covering some 10,800 square miles, the Rann of Kutch becomes a salt marsh during the annual rains. Nestled between the Gulf of Kutch in India's northwestern state of Gujarat and the mouth of the Indus river in southern Pakistan, the region is home to Asia’s last herds of wild asses. Patches of high ground seen in the image become a refuge for wildlife during the wet season.>>

<<Chir Batti or Cheer batti (Ghost light) is a yet unexplained strange dancing light phenomena occurring on dark nights reported from the Banni grasslands, its seasonal marshy wetlands and the adjoining desert of the marshy salt flats of the Rann of Kutch near Indo-Pak border in Kutch district, Gujarat State, India. Local villagers have been seeing these sometimes hovering, sometimes flying balls of lights since time immemorial, and call it Chir Batti in their Kutchhi-Sindhi language, with Chir meaning ghost and Batti meaning light. A team of local and US ornithologists confirmed observing this strange phenomena in great detail which is already well known to local village folk and soldiers of the Indian Border Security Force (BSF) who patrol day and night the adjoining Rann of Kutch international border area of India with Pakistan.

As per eye witnesses this phenomena refers to a strange light as bright as a mercury lamp that changes its color to blue, red and yellow and resembles a moving ball (reported also pear shaped form) of fire, which may moves as fast as an arrow but may also stop. It is not just one light, but could appear at several places. The light has also been observed to becomes two from one. As per local folklore these lights have been a part of life of Banni grasslands and the adjoining Rann of Kutch for centuries, but unfortunately as not well known beyond the immediate area this phenomena has not yet been studied for scientific explanations and people continue calling these strange light occurrences as ghost lights. It is reported that these lights can only be seen after 8 pm on dark nights and are always 2-feet above the ground to about 8- to 10-feet in the air and no record exists of them having ever harmed any one so far except that if followed in the middle of a dark night one could be misled from the road and lose their way in thorny jungles or desert of the salt flats of the Rann. Witnesses claim that these lights at times appear to be playing hide and seek, even if one decided not to follow them, they can at times creep up on one.>>

<<The Great Rann of Kutch (Gujarati: કચ્છનું મોટું રણ), is a seasonal salt marsh located in the Thar Desert in the Kutch District of Gujarat, India and the Sindh province of Pakistan. The name "Rann" comes from the Hindi word ran (रण) meaning "salt marsh". The Hindi word is derived from Sanskrit/Vedic word iriṇa (इरिण) attested in the Rigveda and Mahābhārata. The Great Rann of Kutch comprises some 10,000 sq mi between the Gulf of Kutch and the mouth of the Indus River in southern Pakistan. The area was a vast shallows of the Arabian Sea until continuing geological uplift closed off the connection with the sea, creating a vast lake that was still navigable during the time of Alexander the Great. The Ghaggar River, which presently empties into the desert of northern Rajasthan, formerly emptied into the Rann of Kutch, but the lower reaches of the river dried up as its upstream tributaries were captured by the Indus and Ganges thousands of years ago. Traces of the delta and its distributary channels on the northern boundary of the Rann of Kutch were documented by the Geological Survey of India in 2000.

In India's summer monsoon, the flat desert of salty clay and mudflats, averaging 15 meters above sea level, fills with standing waters, interspersed with sandy islets of thorny scrub, breeding grounds for some of the largest flocks of Greater and Lesser Flamingoes, and is a wildlife sanctuary. There are 13 species of lark in the Rann of Kutch. The Little Rann of Kutch is famous for the Indian Wild Ass sanctuary, where the worlds last population of Indian Wild Ass still exists. Other mammals of the area include the Indian Wolf, Desert Fox, Golden Jackal, and the threatened Blackbuck. The marshes are also a resting site for migratory birds, and are home to over 200 species of bird including the threatened Lesser Florican and Houbara Bustard.

This inhospitable salty lowland, rich in natural gas is part of India and Pakistan's ongoing border dispute concerning Kori Creek. In April 1965, a dispute there contributed to the Indo-Pakistani War of 1965, when fighting broke out between India and Pakistan. Later the same year, Prime Minister of the United Kingdom Harold Wilson successfully persuaded both countries to end hostilities and set up a tribunal to resolve the dispute. A verdict was reached in 1968 which saw Pakistan getting 10% of its claim of 3,500 sq mi. The majority of the area thus remained with India.>>

[Beyond]

The sunset is fabulous! The spirals do nothing for me; but I they are art.

Click to view full size image

Orin, don't stare at the picture when you are typing your thoughts. "but I they are Art"? Your englash is as baad as mine sumtimes is.
Or pehaps it's just the Scottish in you coming out a wee bit? Then it would be - "but aye they are Art." But then, afterall, it IS a very nice picture, no matter how you say it!

[Star*Hopper]

ASTRONOMY:
Y'know, more & more I've come to think maybe my school-taught-&-long-held definition of 'astronomy' was & has been lo these many years, somehow amiss or outrightly erroneous. Curious; what do others say?

What I say? Take Rob's advice!

O, kind madame....had I taken Rob's advice, I might not have sought affirmation of my fundamental beliefs, which were shaken, and found it! Mind you, I never said I didn't enjoy the show....but the sky's a multiplex, and if I had my 'druthers........I did after all enter the theatre named "Astronomy Picture Of The Day".

Popcorn?

~S*H

[owlice]

Ah, but regardless of the name of the theater, there are special features, previews, and sometimes even cartoons! It's a long show; there are plenty of opportunities to concentrate on the main feature.

Thanks for the popcorn! Would you like some Snowcaps?

Owl

[macshepperd@gmail.com]

The rays referred to are antecrepuscular, not crepuscular. Crepuscular rays appear to rise from the Earth to the Sun, antecrepuscular rays appear, as do the rays in the photo, to tend up from where the Sun is. Look it up in Bowditch.

[owlice]

The rays referred to are antecrepuscular, not crepuscular. Crepuscular rays appear to rise from the Earth to the Sun, antecrepuscular rays appear, as do the rays in the photo, to tend up from where the Sun is. Look it up in Bowditch.

Ah, no, don't think so; see links in this post:

They are parallel (or very nearly so), they only appear to converge, in much the same way as railroad tracks appear to converge in the distance. It's just a matter of perspective.

http://en.wikipedia.org/wiki/Crepuscular_rays
http://www.atoptics.co.uk/atoptics/ray1.htm

[judy]

fire the projectionist and roll the film called astronomy as the dictionaries describe it. j

[owlice]

Or instead, admire the view shown, look at recent submissions, read the latest astronomy news, see a slice of APOD going back to its first year, check out HiRISE images, or see what APOD was up to on your birthday three years ago. And let's keep the projectionists.

[NoelC]

Funny thing... The image seems to have been taken facing toward the northwest... Most likely a sunset, then, after a long summer day?

You can see the spiral jetty on Google Maps here:

http://maps.google.com/?ie=UTF8&ll=41.4 ... 7&t=h&z=18

-Noel