wrote in message
oups.com...
Ya know, at a high enough orbit the Venutian blind (sp intentional)
would probably only have to be the size of a football field or three.
Okay, I have absolutely no way of rationalizing this, but I just
latched on to the idea of a NASA/Home Depot collaboration and went off
on a tangent...

If the sun was a point source of light, then you could put a smaller body
between the Earth and it and cover the entire planet with the shadow...
Since the sun is larger, that doesn't work... You would need an object the
size of the Earth and close to it to cover the entire planet... For 75%
coverage, you would need an object at least 75% the size of the Earth...
Even when we have a solar eclipse, the moon's shadow is only going across a
portion of the planet... If the moon orbited at a greater distance (I'm
don't remember of the exact distance off the top of my head), all we would
see of the eclipse would be the silhouette of the moon obscuring a part of
the sun -- the edges of the sun not obscured by the moon would still be
providing light... Although we would still be getting light, it would be at
a reduced energy level, so theoretically it should affect the warming of the
planet... On the other hand, since polar warming and the subsequent melting
of the polar ice packs is seen as a concern by certain individuals, perhaps
we should just shadow these areas and let them build up more ice... Of
course, while we're at it, maybe we can provide a partial shadow for Houston
during the summer months so that the temperature would be more bearable...