Mirrors versus diffuse reflection

To answer your first question. A white surface actually absorbs about
50% of the light that hits it. I'm sure special paints could be
created to lower that down to 20%.

The first real problem is keeping the white surface white. Dust and
dirt will fall on it lowering the albedo of the surface.

Paint fades in direct sunlight. Again special paint could be used, but
the maintenance needed maybe much higher then cleaning windows.

Now I had read a novel about a simialr concept. It was a group of
comet cowboys (there term) that was mining a comet from the inside out
and had created "windows" out of the translucent ice.

To answer your second, I don't know but I suspect that it is very
dependant on the type of plants.

Bill

--- In space

settlers@y..., "Dr. Omni" wrote:
> Hi,
>
> For some reason, in the last few days I have been thinking about
designs for
> spherical and cylindrical rotating habitats following what I call
"Frazer's
> Guidelines" (*) for lighting: instead of having huge transparent
areas for
> letting sunlight in, they make use of relatively small transparent
"holes"
> where concentrated sunlight gets into the habitat and is used for
lighting.
> At first, as usual, I thought about mirrors inside the colony to
disperse
> the incoming sunlight in a useful way. But after a while I thought:
wouldn't
> simply making the sunlight hit an opaque and purely white surface be
a
> simpler and cheaper alternative to a mirror system?
>
> To illustrate my reasoning, I'll use the case of a spheric colony
with a
> transparent cap 60 degrees in diameter centered at one of the poles.
> Concentrated sunlight enters throught that "window" and has to
illuminate
> the whole interior of the sphere.
>
> First I thought about using a spherical convex mirror either
protuding from
> the opposite cap or hanging in the space between the two poles to do
the
> job. Then, I thought that it would be simpler to just coat the
opposite cap
> with reflexive material, transforming it into a concave mirror: the
sunlight
> would be concentrated into a focus and then spread to all the
internal
> surface of the colony. However, that could overheat and even ionize
the air
> at the focus, and so I considered it a not-so-elegant approach...
>
> Finally, I saw that if the task is to disperse the light along the
internal
> spherical surface, then simply painting the opposite cap with
pristine white
> would do the job without the unpleasant effect of an overheated
focus.
> Sunlight would hit the white cap and then suffer diffuse reflection:
an
> effect analogous to a spot light hitting a white wall and providing
indirect
> illumination.
>
> For those who think that a colony should be as eartlike as possible,
of
> course that does not sound good, but then neither does the "Frazer's
> Guidelines", so that's outside discussion here. My major concerns
are more
> practical, and I would much apreciate any references or answers to
them:
>
> - Are there white surfaces with albedo comparable to that of
mirrors? In
> other words, would the vast majority of sunlight be reflected or
would a
> significant fraction of it be absorbed by the white cap?
>
> - For some reason, does vegetal life prefers "hard", "direct"
sunlight
> instead of a soft indirect glow?
>
> Thanks in advance,
>
> Lucio Coelho
>
> * I say "Frazer's Guidelines" because John Frazer was the first one
that I