Among other things, Christopher James Huff wrote:

>> > The Earth doesn't really add anything by radiosity alone so I'll add a
>> > light source to it.
>> 
>> Right; it's too far away.
> 
> Distance has little to do with it, it is the area of sky covered and
> brightness per unit area that counts.

Is this true? I mean, in POV world, doesn't distance really matter when 
computing radiosity?

> This all means that Earthlight is much brighter than moonlight. It's
> still very little in comparison to direct sunlight, but it can
> contribute to shadowed areas if the viewer's not looking at a bright
> object, and will be very significant at night on the near side. And it's
> practically all due to radiosity, diffusely scattered sunlight, though
> an area light might be more accurate than any but very high radiosity
> settings.

Yes. When the moon is very thin, you can clearly see the dark side lit by 
"earthlight". Even in a Moon eclipse, when all the moon is in shadow, and 
the earth face it sees is at night, the Moon is notably lit with a red 
glow, which comes from scattering in the Earth's atmosphere (all the dawns 
and twilights).

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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