Mirrors versus diffuse reflection

Jus another thought about diffuse lighting. If you change the design
to a cone or a paraboloid (half of a football shape) with the base as
a large window, the requirement for diffuse lighting is minimized. The
place will look like the side of a mountain at dawn or dusk all the
time (which may become a pain after a while).

Just a thought.

Bill

--- In spacesettlers@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