Posted: Sat Oct 11, 2008 3:10 pm
The image is not an attempt to create a completely realistic view of the Earth at night. The "white" you see on your monitor is brighter than the amount of light that would hit your eye if you were viewing the Earth from space. The visual impression might be quite similar, however, since the eye and brain tend to adjust the scale, so you might well see the brightest cities as something like "white", even though there wouldn't be enough light to read your newspaper by it.Fermats Brother wrote:However, I'm a little skeptical about this picture, in that I cannot find any mention of exposure time(s). I think this is important in putting this picture into perspective. As presented, I get the impression that I could read my newspaper in my satellite with the lights switched off !!
There are many galaxies we can see in photographs, but which require exposure times of several hours. Maybe this is similar.
What you would see is far brighter than a galaxy, however. If you've ever flown over cities or towns at night, you already know how bright they are. They don't look any dimmer from space. Astronauts easily see the brightness and color of cities from the ISS, and can image them with handheld cameras. You don't need very long exposure times.
I doubt the equivalent exposure time for this image is more than a few seconds.