> This is what I'm interested in. Are the lights visible from this distance 
> because they glow? Or would any old object be visible from such a 
> distance? (Assuming it wasn't the middle of the night, obviously.)

The fact that it is dark helps a lot, obviously your eye is much more 
sensitive then.

According to this page:

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

A rod in your eye must receive about 5-9 photons over 100 ms to tell your 
brain that something is there.  That is a pretty damn small amount of light.

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