[extropy-chat] Re: SPACE: new planet?

[Mike Lorrey]

--- Spike <spike66 at comcast.net> wrote:
>  
> > Mike Lorrey wrote:
> > 
> >  >It is actually rather easy to define a planet:
> >  >a) it has its own independent orbit around the sun, and,
> >  >b) its own internal gravity has caused it to be round
> > 
> > What is "round"?
> > 
> > - Joe
> 
> 
> And what is "independent"?  Any definition that would
> exclude Luna would also take out Earth.

Picking nits. What is the overwhelmingly major mass in any given orbit?
Any body of significantly less mass orbiting that major mass is a moon,
and the major mass is a planet, if it is spherical due to its own
gravity.

Now, the ancients considered the Moon to be a planet, actually THE
chief planet, since it was the largest in the sky, and second only to
the Sun in cosmological importance. Of course, this is an entirely
primitive, geo-centric point of view. We should  strive to avoid such.

"[The Moon] is only one-fourth the size of the Earth, having a diameter
of 3,476 km (2,318 miles); which is less than the distance across the
United States. The volume of the moon is about 1/50 of the Earth. The
Earth and its moon could be considered twin planets compared to huge
planet like Jupiter and Saturn, which are 40 or 50 times larger than
their biggest moons [ an odd statement to make, since the volume of the
Moon is 1/50th of the Earth, and the mass of the Moon is 1/80th that of
Earth]. The moon's mass is about 0.012 times that of the Earth (7.35 x
1022 kg) [msl comment - the Earth's mass is therefore 80 times that of
the Moon]. The moon's gravity is one-sixth that of the Earth."
http://hypertextbook.com/facts/2002/AdaLi.shtml

It is clear that the Moon is not a co-planet of the earth. While it is
certainly larger in diameter than some planets like Mercury or Pluto,
it is, unfortunately, a significantly minor player in the Earth's
orbit. That is its own fault for hitting the earth so poorly in our
early history. It remains Earth's familiar, never an independent entity.

=====
Mike Lorrey
"Live Free or Die, Death is not the Worst of Evils."
                                       - Gen. John Stark
"Fascists are objectively pro-pacifist..."
                                       - Mike Lorrey
Do not label me, I am an ism of one...
Sado-Mikeyism: http://mikeysoft.zblogger.com

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