APOD: Earth Shadow over Damavand (2017 Apr 14)

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APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby APOD Robot » Fri Apr 14, 2017 4:07 am

Image Earth Shadow over Damavand

Explanation: Through crystal clear skies this beautiful panorama follows the curve of planet Earth's shadow rising across the top of the world. The tantalizing twilight view is composed of eight single frames captured from 4,000 meters above sea level at sunset on April 6. Just above the dark grey Earth-shadow boundary lies a fading, pinkish, anti-twilight arch. Also known as the belt of Venus, its reddened and back-scattered sunlight finally merges with the still blue eastern sky. Standing tall near center along the rugged horizon line is the distant sharp peak of Mount Damavand in the snowy Alborz mountains. A feature in Persian mythology and literature, Damavand is a stratovolcano reaching 5,610 meters above sea level, the highest peak in Iran and the Middle East.

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Ann » Fri Apr 14, 2017 6:54 am

That's a fine portrait of the Earth's shadow. And Mount Damavan looks impressive, almost poking a hole in the rising blue arc with its white summit.

And by the way, April 14, 2017... Congratulations to my brother, who is 60 today.

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Boomer12k » Fri Apr 14, 2017 7:09 am

Awesome view... great pic.... is that pollution on the right???

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby JohnD » Fri Apr 14, 2017 9:22 am

You don't have to be 4000 metres high to see the Belt of Venus.
Last year I was in Rio for both Olympics. Between the two, on a perfectly clear day, we drove south to beaches on the far side of of the modern sprawl of Barra de Tijuca. On our return in the dusk, driving slowly along the 18kms of Barra beach, I could look directly out to sea (I wasn't driving!) and watch the Belt sink lower and lower, as the sky darkened.
A wonderful sight and another wonderful memory of Rio!

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Chris Peterson » Fri Apr 14, 2017 1:47 pm

JohnD wrote:You don't have to be 4000 metres high to see the Belt of Venus.
Last year I was in Rio for both Olympics. Between the two, on a perfectly clear day, we drove south to beaches on the far side of of the modern sprawl of Barra de Tijuca. On our return in the dusk, driving slowly along the 18kms of Barra beach, I could look directly out to sea (I wasn't driving!) and watch the Belt sink lower and lower, as the sky darkened.

That is a most curious perspective. Surely, as the Sun sets, the Belt rises higher in the sky? That's how I've always seen it; indeed, I often refer to it as nightrise.
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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby BDanielMayfield » Fri Apr 14, 2017 3:32 pm

JohnD wrote:You don't have to be 4000 metres high to see the Belt of Venus.

Well that statement is very true. I'm close to sea level and have seen the BoV often, both in the morning and evening.

This phenomenon must often go unnoticed because people's attention is drawn toward the more colorful sunrises and sunsets 180 degrees away.

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Chris Peterson » Fri Apr 14, 2017 3:46 pm

BDanielMayfield wrote:
JohnD wrote:You don't have to be 4000 metres high to see the Belt of Venus.

Well that statement is very true. I'm close to sea level and have seen the BoV often, both in the morning and evening.

This phenomenon must often go unnoticed because people's attention is drawn toward the more colorful sunrises and sunsets 180 degrees away.

I live at a fairly high elevation, 2800 meters, with the consequence that my skies are very clear and dry, and I see the phenomenon almost every day. I can judge the clarity of the sky by how high the belt gets before it finally disappears- the clearer the skies, the higher it gets.
Chris

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby neufer » Fri Apr 14, 2017 4:01 pm

Bill Bryson - A Short History of Nearly Everything wrote:
<<The absolute limit of human tolerance for continuous living appears to be about 5,500 meters, or 18,000 feet, but even people conditioned to living at altitude could not tolerate such heights for long. Frances Ashcroft, in Life at the Extremes, notes that there are Andean sulfur mines at 5,800 meters, but that the miners prefer to descend 460 meters each evening and climb back up the following day, rather than live continuously at that elevation. People who habitually live at altitude have often spent thousands of years developing disproportionately large chests and lungs, increasing their density of oxygen-bearing red blood cells by almost a third, though there are limits to how much thickening with red cells the blood supply can stand. Moreover, above 5,500 meters even the most well-adapted women cannot provide a growing fetus with enough oxygen to bring it to its full term.>>
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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby BDanielMayfield » Fri Apr 14, 2017 4:30 pm

Chris Peterson wrote:
JohnD wrote:You don't have to be 4000 metres high to see the Belt of Venus.
Last year I was in Rio for both Olympics. Between the two, on a perfectly clear day, we drove south to beaches on the far side of of the modern sprawl of Barra de Tijuca. On our return in the dusk, driving slowly along the 18kms of Barra beach, I could look directly out to sea (I wasn't driving!) and watch the Belt sink lower and lower, as the sky darkened.

That is a most curious perspective. Surely, as the Sun sets, the Belt rises higher in the sky? That's how I've always seen it; indeed, I often refer to it as nightrise.

Since people are used to looking toward the setting sun at sundown the common experience is to see darkness descend at dusk. JohnD, like most people, must have seen scores of descending sunsets for every BoV he's observed. My diagnosis would be an error of recollection due to conditioning. How does that sound Dr. John?

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby JohnD » Fri Apr 14, 2017 8:14 pm

Indeed, glad to be corrected!
Maybe I had been partying too hard.
John

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby MarkBour » Fri Apr 14, 2017 8:42 pm

neufer wrote:
Bill Bryson - A Short History of Nearly Everything wrote:
<<The absolute limit of human tolerance for continuous living appears to be about 5,500 meters, or 18,000 feet, but even people conditioned to living at altitude could not tolerate such heights for long. ...
Moreover, above 5,500 meters even the most well-adapted women cannot provide a growing fetus with enough oxygen to bring it to its full term.
>>

Capture1.JPG

Interesting. And while these are facts, I'm in the mood for jest.

There is one famous and beautiful high-altitude monastery currently located at roughly 400,000m which has been continuously inhabited for the last 17 years.

It remains to be seen whether or not a woman could carry a pregnancy there, though from what I could gather (I have no medical expertise), the consensus seems to be that it would be unlikely that she could, and currently a very bad idea to try.

It seems that it ought to be possible to capture an image of these living quarters right within the belt of Venus, on a lucky evening or morning.
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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby jadlhoch » Fri Apr 14, 2017 8:59 pm

Boomer12k wrote:Awesome view... great pic.... is that pollution on the right???

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Yes, horrendous pollution!

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby BDanielMayfield » Fri Apr 14, 2017 9:18 pm

Have any experiments with fish, mice, etc. been done on the ISS to see if animals can successfully be bred and raised in zero gee?

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Tszabeau » Fri Apr 14, 2017 10:17 pm

Night falls up.

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby geckzilla » Fri Apr 14, 2017 11:13 pm

Chris Peterson wrote:
BDanielMayfield wrote:
JohnD wrote:You don't have to be 4000 metres high to see the Belt of Venus.

Well that statement is very true. I'm close to sea level and have seen the BoV often, both in the morning and evening.

This phenomenon must often go unnoticed because people's attention is drawn toward the more colorful sunrises and sunsets 180 degrees away.

I live at a fairly high elevation, 2800 meters, with the consequence that my skies are very clear and dry, and I see the phenomenon almost every day. I can judge the clarity of the sky by how high the belt gets before it finally disappears- the clearer the skies, the higher it gets.

There must be some balance that allows for optimal visibility. It would be totally invisible in a perfect vacuum. Too many particles, and there is too much scattering to see far. Too few, and there's nothing for the light to interact with.
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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby MarkBour » Sat Apr 15, 2017 2:42 am

BDanielMayfield wrote:Have any experiments with fish, mice, etc. been done on the ISS to see if animals can successfully be bred and raised in zero gee?
Bruce

Here's one summary, that seems the clearest I found, if it can be believed (since it is not direct reporting) https://space.stackexchange.com/questions/4513/what-animals-if-any-have-reproduced-in-space
There have been a bunch of experiments, and some are in progress on ISS (https://www.nasa.gov/mission_pages/station/research/experiments/893.html)
although it seems they are going at very specific things with the ISS experiments.
Mark Goldfain

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby MarkBour » Sat Apr 15, 2017 2:50 am

Chris Peterson wrote:I live at a fairly high elevation, 2800 meters, with the consequence that my skies are very clear and dry, and I see the phenomenon almost every day. I can judge the clarity of the sky by how high the belt gets before it finally disappears- the clearer the skies, the higher it gets.

So, where you're at, with the Sun setting in the West, you would look at it to the East and watch what you call "night rise". I like the term! If you were up before dawn, I don't suppose you're in as good a position to see it in the West, which you might call "night-set"?
Mark Goldfain

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Chris Peterson » Sat Apr 15, 2017 4:32 am

geckzilla wrote:
Chris Peterson wrote:I live at a fairly high elevation, 2800 meters, with the consequence that my skies are very clear and dry, and I see the phenomenon almost every day. I can judge the clarity of the sky by how high the belt gets before it finally disappears- the clearer the skies, the higher it gets.

There must be some balance that allows for optimal visibility. It would be totally invisible in a perfect vacuum. Too many particles, and there is too much scattering to see far. Too few, and there's nothing for the light to interact with.

I've thought about that. Empirically, I know that the higher I go, or the clearer the air, the more apparent the Belt, and the higher it can get in the sky before it disappears. My conclusion is that it is a phenomenon of light scatter from atmospheric gases, and any aerosols or particulates produce scatter that reduces the contrast. Just as our skies are exceptionally blue because of the low particulates.
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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby Chris Peterson » Sat Apr 15, 2017 4:37 am

MarkBour wrote:
Chris Peterson wrote:I live at a fairly high elevation, 2800 meters, with the consequence that my skies are very clear and dry, and I see the phenomenon almost every day. I can judge the clarity of the sky by how high the belt gets before it finally disappears- the clearer the skies, the higher it gets.

So, where you're at, with the Sun setting in the West, you would look at it to the East and watch what you call "night rise". I like the term! If you were up before dawn, I don't suppose you're in as good a position to see it in the West, which you might call "night-set"?

It's not hard for me to get a view to the west in the morning, but not from the house or deck. And I'm not really a morning person, so I'm seldom inclined to be outside at sunrise. I have, of course, seen the Belt effect in the morning at times. But I see it almost every evening.
Chris

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Re: APOD: Earth Shadow over Damavand (2017 Apr 14)

Postby BDanielMayfield » Sat Apr 15, 2017 10:52 am

MarkBour wrote:
BDanielMayfield wrote:Have any experiments with fish, mice, etc. been done on the ISS to see if animals can successfully be bred and raised in zero gee?
Bruce

Here's one summary, that seems the clearest I found, if it can be believed (since it is not direct reporting) https://space.stackexchange.com/questions/4513/what-animals-if-any-have-reproduced-in-space
There have been a bunch of experiments, and some are in progress on ISS (https://www.nasa.gov/mission_pages/station/research/experiments/893.html)
although it seems they are going at very specific things with the ISS experiments.


Thanks Mark.

Looks like artificial G, (not to mention better radiation shielding) will be needed for any type of animal agriculture to work on a permanent space station or a very long duration space flight.

Bruce
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