Interesting Pictures

Posted by: Justyn on 10 February 2006

The photograph attached was taken by the crew on board the Columbia during its last mission, on a cloudless day.

The picture is of Europe and Africa when the sun is setting. Half of the picture is in night. The bright dots you see are
the cities lights.

The top part of Africa is the Sahara Desert.
Note that the lights are already on in Holland, Paris, and Barcelona, and that's it's still daylight in Dublin, London, Lisbon,
and Madrid.

The sun is still shining on the Strait of Gibraltar. The Mediterranean Sea is already in darkness.
In the middle of the Atlantic Ocean you can see the Azores Islands; below them to the right are the Madeira Islands; a bit
below are the Canary Islands; and further south, close to the farthest western point of Africa, are the Cape Verde Islands.

Note that the Sahara is huge and can be seen clearly both during Daytime and night time.

To the left, on top, is Greenland, totally frozen.



Justyn.
Posted on: 10 February 2006 by Nime
Fascinating. I had never realised the Earth's terminator was so sharply defined. (imagining the atmosphere would soften the shadow/light edge considerably with penumbra)
Posted on: 10 February 2006 by BigH47
It would seem to be slightly broader area of "twilight" further north. A mate always said it almost switched instantly from day to night when he worked near the equator(Zambia I think).
Posted on: 10 February 2006 by DIL
Just wondering if there is any digital jiggery pokery going on here. If you look at the atlantic, the continental shelf around the UK as well as other undersea features can clearly be seen. Surely these would not be ssen in a photohgraph...

Also, given that the shuttle operates in a reletively low earth orbit, is it reasonable to have the light/dark interface in the middle of the image ? See, for example this image of a sunset over argentina from STS037.

/dl
Posted on: 10 February 2006 by Justyn
David,

You are indeed correct. I received the picture in an e-mail,(having checked) the picture is actually correct, however it is a combination of several images from a satellite.

Justyn
Posted on: 10 February 2006 by PS
quote:
David,

You are indeed correct. I received the picture in an e-mail,(having checked) the picture is actually correct, however it is a combination of several images from a satellite.

Justyn


.....correct about the digital jiggery pokery or the light/dark interface???

....it would be wierd if one could see underwater terrain from space.... Confused
Posted on: 10 February 2006 by Justyn
quote:
.....correct about the digital jiggery pokery or the light/dark interface???


This what came up when checking.

quote:
No single spacecraft or astronaut took this picture. It is a digital composite of archived images taken by several Earth-orbiting satellites and ocean-faring ships... Specifically, the daytime land images were taken by the MODIS instrument on NASA's Terra satellite, while the nighttime images were taken by the DMSP satellites. This image is different from what an astronaut would see for reasons including a complete lack of clouds and an unrealistic exaggeration of lights and contrasts.


Justyn.
Posted on: 10 February 2006 by rodwsmith
Wonderful picture, but sadly not everything it purports to be. For the reasons alluded to above, sunset over the Earth would never be visible quite like this.

Not to mention the unlikelihood of no cloud whatsoever over western Europe...

More info here
Posted on: 10 February 2006 by rodwsmith
Simultaneous posting Justyn, sorry...
Posted on: 10 February 2006 by BigH47
It's still a good picture whatever the parentage.

H
Posted on: 10 February 2006 by Nime
My understanding is that the higher you are the deeper you can see under water. I remember this from my childhood. Perhaps something to do with reading about Abbe and the Bathyscape? He went up as well as down.
Posted on: 10 February 2006 by BigH47
Do you meen Beebe? I seem to remember him going deep and high in various steel balls.

H
Posted on: 10 February 2006 by Nime
Thanks H. (Memory crash)

Abbe was the optics chappy.
Posted on: 11 February 2006 by DIL
Nime
quote:
My understanding is that the higher you are the deeper you can see under water. I remember this from my childhood. Perhaps something to do with reading about Abbe and the Bathyscape? He went up as well as down.

Probably correct up to a point. But below a certain depth, light does not penetrate, effectively creatingt a 'black floor' below which nothing, no matter how high up you are, will be visible. Not sure of this depth, but I'd guess at a couple of 100m's.

/david