[ExI] Fermi question

[BillK]

On Tue, Dec 27, 2011 at 9:53 AM, Kelly Anderson  wrote:
> In this video from 18 to 20 seconds, you can see some lights on the
> earth that appear to be city lights, but it's hard to tell at the
> YouTube resolution.
> http://www.youtube.com/watch?v=6VdSFT8Ouqg&feature=player_embedded
>
> I suspect this is at a distance more or less analogous to the distance
> from the moon... so the answer would seem to be that if you were on
> the moon during a solar eclipse, you could indeed see city lights...
> but I don't know for sure.
>
>

That video is from the EchoStar 11 Satellite, 22,300 miles up. About
1/10 the distance to the moon.
The ‘eyes’ of the DISH Earth camera observes objects in the visible
spectrum, similar to the human eye, with a resolution of about 20 km
per pixel.

Also Snopes comments:
<http://www.snopes.com/science/greatwall.asp>

An object that can barely be seen from a height of 180 miles up is
obviously not going to be visible from the moon (roughly 237,000 miles
away), as confirmed by Apollo 12 astronaut Alan Bean:
The only thing you can see from the moon is a beautiful sphere, mostly
white (clouds), some blue (ocean), patches of yellow (deserts), and
every once in a while some green vegetation. No man-made object is
visible on this scale. In fact, when first leaving earth's orbit and
only a few thousand miles away, no man-made object is visible at that
point either."
---------

Presumably the discussion is about objects seen with human eyes.
Telescopes, radar, etc. can see lots more.


BillK