[ExI] destiny's road: was RE: rebuilding a saturn v today

Dan dan_ust at yahoo.com
Thu Mar 31 13:01:29 UTC 2011

What about the effect of light from other stars?



From: spike <spike66 at att.net>
To: ExI chat list <extropy-chat at lists.extropy.org>
Sent: Tue, March 29, 2011 7:57:34 PM
Subject: [ExI] destiny's road: was RE: rebuilding a saturn v today

...On Behalf Of Mike Dougherty

>...In "Destiny's Road" Larry Niven poses a nanotech solution of polishing
the moon's surface to mirror-smooth finish to provide solar power at
night... Mike

Interesting thought experiment: imagine the moon to be a perfectly spherical
polished mirror surface of 100 percent reflectivity in all wavelengths.
What would it look like from here?  I would be open to counterargument, but
I think it would appear as one very bright point of light caused by the
reflection of sunlight.  This point of light would have an apparent diameter
of about 80 microradians and would provide a little less than 1% the light
of the sun, nearly regardless of the phase of the moon.  This point of light
would be accompanied by a reflection of the earth, which would also look a
lot like a bluish point of light, much dimmer than the other point of light.

I might be off by a factor of two on the big side.  I need to ponder that

Someone please think that through and see if you can get similar looking
numbers.  Or if you get different numbers, do explain your reasoning: I am
open to suggestion on it.  Mike what numbers did you get, and why?

Another thought experiment:  imagine we can stop the nutation of the moon by
some means and round out the orbit, so that it is perfectly stationary from
our point of view.  Then imagine grinding a flat spot on the moon and polish
that.  What diameter does the flat spot need to be in order to reflect all
the light down to earth?  Think about that one carefully.


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