Date: Fri, 12 Apr 2002 00:02:46 -0500
From: Jeff Wilson 
Subject: RE: (urth) distance

>      From:  
          "Dan'l Danehy-Oakes"  I'm no orbit mechanic, but that seems unlikely with a six-year period,
> and _very_ unlikely to cause the inhumi to be able to cross only for a 
> short period.
> 
> > Thanks!  You made everything so much easier!  
> 
> Oh. Good.
> 
> > So we know that the moon was moved from about 80 to 50 thousand
> > leagues in Severians day 
> 
> Ahem. We do not know that it "was moved." I believe that most models
> suggest that the Moon _will_ in fact move closer over (geological) 
> time.

	It's moving away, a fact available to SF writers through such obscure
channels as the "Peanuts" comic strip. This is because of an obscure
means of conserving angular momentum lost by the earth from tides on the
moon; this may point to fiddling by Abaia or other Dark Lords, as moving
Lune closer and increasing its mass/gravity would make tides more
severe, something directly impacting Abaia's aquatic minions.

	This kind of mechanics may have escaped a simple potato chip engineer,
but as an SF writer with such sublime grasp of quantum electrodynamics
that he can dramatize them as "How I Lost the Second World War and
Helped Turn Back the German Invasion," I can only wonder.
 
> > ... the moon is proportionally very large for a satellite when compared
> > with the earth's mass.  It is huge compared to the satellites of most
> > of the gas giants.
> 
> Correct; we are actually best regarded as a double-planet system. (The
> center about which the Earth-Moon system mutually orbits is, if I am not 
> mistaken, not actually inside the Earth.) 

	You are mistaken; the barycenter is about 1000 miles deep inside the
earth at all times. But this is not necessarily meaningful; the
Jupiter-Sol barycenter is outside the sun, but no one's suggesting this
is a binary solar system.

-- 
Jeff Wilson
How Am I Posting? 1-800-555-6789
"If your SecOp can see you, so can the enemy." -Cpt Law


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