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

Mike Dougherty msd001 at gmail.com
Wed Mar 30 03:36:23 UTC 2011

On Tue, Mar 29, 2011 at 7:57 PM, spike <spike66 at att.net> wrote:
> 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
> harder.
> 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?

I'm not very strong (ok, quite weak) on the numbers - I'm more a
brainstorming guy :)

I'd imagine tearing a large chunk off the middle and making the
surface more concave (think one giant crater) by building up the sides
with the regolith removed from the middle.  If we could get a
parabolic surface to redirect that beam to the focal point on the
ground, we might have an apparently smaller/brighter moon (assuming we
don't completely destroy it in the attempt)   It's probably just
nonsense though because the herculean effort might not yield enough
sunlight to be worthwhile.

> 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.

The more I think about it, the nuttier it sounds.  It makes the
numbers for Keith's million tons of earth to orbit look like a weekend
project on a typical honey-do list.

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