Perpetual Twilight
Posted on Jan 20, 2012 10:35:35 AM | Don Pettit | 13 Comments    |
terminator

Twice a year, near the winter and summer solstices, the orbit of space station nearly parallels the terminator—the fuzzy line separating day from night on the surface below. For a period of about a week, we live in what seems like perpetual twilight, being in neither full daylight nor full night. Our orbit follows the terminator, so that space station is constantly sunlit. From this vantage I can see both day and night simply by swiveling my head from left to right. But the night is not really dark, and the day is lit by low-angle rays from the Sun.

Geographic relief casts long shadows, and imparts stark contrast to features that are typically overlooked. Small ripples in sand dunes make high contrast striations across the bright desert landscape that look like Nature’s way of drawing with pen and ink. Geographic relief plays tricks on you. First you see the Grand Canyon as this deep scar. Blink your eyes and it is now a rippling bump. Thunderstorms cast shadows that look like they come from some new type of ray beam weapon. Airliners, their path defined by contrails, leave glimmering lines like snail trails in the morning dew. The gardens of Earth appear to have quite an infestation of snails.

The Moon sets in a counterintuitive way. From this vantage it moves nearly parallel to the horizon. Once I saw it slowly set, only to reappear in a few minutes. The Moon was visible for nearly the whole orbit.



The night side is equally fascinating. The atmosphere on edge glows with a vibrant electric blue. Did van Gogh paint this scene? I can see at least five, maybe six distinct layers of blue—perhaps a visual display of the classic atmospheric strata. Just past the terminator, rays of sunlight can be seen projected above the darkened limb of the Earth.

The most striking aspect of our atmosphere is not the palette of electric blue colors but the thinness of it all. Our atmosphere is a diaphanous veil; thin, fragile, transparent, and the only thing that protects us from the harsh vacuum of space. Too much atmosphere, and the planet is choked and suffocated. Too little, and it is exposed to the harshness of cosmic space. My vantage on the station gives me a deep appreciation of this fact.

Tags : astronauts, exploration, international space station  

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13 Comments so far ( Post your own )
13 On Jan 25, 2012 07:06:43 AM  Mr.War  added a comment on your blog post. 

It must be quite a sight...

12 On Jan 20, 2012 11:20:13 PM  Beth Webber  added a comment on your blog post. 

Don, you are quite a poet, not to mention engineer, scientist, and explorer.

Beth

11 On Jan 29, 2012 12:36:33 AM  Johnny Rodgers  added a comment on your blog post. 

Wonderful post and blog. Is it possible to access these photographs in high-res anywhere? They're stunning.

Thanks! Happy trails.

10 On Jan 22, 2012 03:25:21 AM  luis fernando verduzco reyna  added a comment on your blog post. 

luis fernando verduzco reyna.
:psitico mental/ilucionista.

Imagenes pre cargadas en directo programacion de televicion
skype twitcam reproduccion de imagenes computacionales
monitor/plasma televisor.
psiquia mental.

9 On Jan 21, 2012 12:23:58 AM  guest  added a comment on your blog post. 

Awesome and beautiful. Can't get enough of these pictures.

8 On Jan 22, 2012 05:07:36 AM  James Goring  added a comment on your blog post. 

Out of this World Photograghy,

7 On Jan 23, 2012 01:47:33 PM  guest  added a comment on your blog post. 

Liked very much the snails mataphor
:-)

6 On Jan 22, 2012 02:17:54 PM  Victor Zhyla , Vyborg  added a comment on your blog post. 

Wonderful pictures and an entertaining story. Thank you and good luck to you.

5 On Jan 22, 2012 06:07:10 PM  guest  added a comment on your blog post. 

You have written a beautiful description of creation. I see so much through your narrative.

I have a profound appreciation for Earth and better understand the vastness of the Universe and what it means to be a part of life in these times. Beautiful photos!!
Thank you.

4 On Jan 22, 2012 08:45:13 PM  allison  added a comment on your blog post. 

WOW

3 On Jan 23, 2012 05:27:35 AM  Betty Donelly  added a comment on your blog post. 

Hi Don!

Yeah Don, you put it nicely .. Mike Fossum emphasised htat too when he was on board ..

It's a real thin layer we got .. and you didn't even mention hte ozone shortages over the poles.

we are in for a bumpy ride .. we the earth's population from the granite rocks to hte oceans and all of earth's inhabitants.

But im positive on hte whole matter .. technology hand in hand wiht nature ... i put my trust in NASA and the well willingness of folks around hte globe .. so we can see this global ecologic crisis through

Light and Love! .. Betty Donelly

2 On Jan 22, 2012 09:30:14 AM  Liliana  added a comment on your blog post. 

Thank you Dr. Petit for this enjoyable reading, almost poetic way to describe the atmosphere!

1 On Jan 22, 2012 07:22:56 AM  ichiro  added a comment on your blog post. 

Dear Don
Thanks for great photos!
Looking forward to watching fabulous 'free liquid film' experiments and others. (It was so nice to see you and have a talk in TKSC.)
See you soon.

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