[Info-vax] CRTL and RMS vs SSIO

[Phillip Helbig undress to reply]

In article <77d0e992-6ae3-4184-8910-5016b6d23efen at googlegroups.com>,
=?UTF-8?Q?Lawrence_D=E2=80=99Oliveiro?= <lawrencedo99 at gmail.com> writes:

> >> Yes. And also the fact that the Moon is so large compared to the Earth. We = 
> >> are really in a binary-planet system, though for some reason astronomers do= 
> >> n't like that description ... 
> > 
> > That depends on the definition of planet.
> 
> A major body which orbits the Sun? if Terra is one such, then Luna
> must be one too. 

It depends on the definition.  If size were the only criteria, then one 
would have to include some satellites of the Jovian planets as well; 
Ganymede and Titan are larger than Mercury.  Of course, the Moon is 
relatively much larger compared to the Earth, and also larger than all 
asteroids and other satellites except Titan and three of the Galilean 
satellites.  The point about which both orbit is inside the Earth, which 
emphasizes the Earth being the main planet, but the orbit of the Moon is 
always concave relative to the Sun, which emphasizes the independence of 
the Moon.  So it depends on the definition.  The current definition, 
which demoted Pluto, is that it is a body which dominates its orbit, so 
that applies to the Earth and not to the Moon.