Christian Walther <cwa### [at] gmxch> wrote:
>consider the
>first-quarter moon. It's approximately a diffusely reflecting sphere
>illuminated from a single direction in an otherwise dark space

I had to jump in here, even though I haven't been following the discussion
closely. The moon is illuminated by two sources: the sun and the earth. The
reflection of sunlight off of the earth (the albedo) is why we can see the
dark portion of the moon. The earth reflects approximately 39% of the
sunlight that hits it (which is where the title of Vangelis' album
"Albedo 0.39" comes from).

Over and out.

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