[extropy-chat] Astronomical question

[Mike Lorrey]

--- spike <spike66 at comcast.net> wrote:
> 
> Those of you who know from oceans, is a moon tide
> about twice as much as a sun tide?  Is a moon tide
> about a meter and a sun tide about half a meter?
> When a high tide comes at a full moon or new moon,
> is that called a neap tide?  Is that about half
> again higher and lower than normal?

Yes, this is common knowledge, that solar tidal influence is about half
that of the moon.

> 
> Using that and estimating a tide as a sort of a
> 2 dimensional haversine, the mass of a moon tide
> comes out to about 3e16 kg.  Model those as a
> 3e16kg point mass rotated about pi/4 forward of
> center and another mass on the opposite side of
> earth rotated aft of center with the same 3e16 kg mass.
> 
> With these assumptions I get around 20 billion years
> to drag the moon up to tidelock with the earth. 

So the ambitions of my environmental group have already resulted in
success, for the time being.... see how effective I can be as a tree
hugger? ;)

> 
> NOVA way doesn't suck!
> 
> I found an interesting thing that I had never heard
> before: the process of tidal drag not only raises the
> moon to a higher orbit, it increases the eccentricity
> of its orbit.  Kewalll!  {8-]  Someone who knows from 
> astronomy, did you already know that?  I have read
> stuff for years but never did run across that.  I
> found it using the tide-as-mass-concentration model.

Are you also considering the tidal influence of the sun on the moon? 
Solar influence on the moon is so significant that the moon's off
center center of gravity causes it to wobble detectably when it is
ebbing. The moon's geometry is a bit warped...

Oh, and BTW: you shouldn't discount Jupiter either. I hear it's
influence is something like 1% of lunar tide. Not huge, but its there.


=====
Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://www.xanga.com/home.aspx?user=Sadomikeyism


	
		
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